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llvm-6502/lib/Transforms/Scalar/InstructionCombining.cpp
Reid Spencer 3822ff5c71 For PR950: 
This patch converts the old SHR instruction into two instructions,
AShr (Arithmetic) and LShr (Logical). The Shr instructions now are not
dependent on the sign of their operands.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@31542 91177308-0d34-0410-b5e6-96231b3b80d8
2006-11-08 06:47:33 +00:00

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//===- InstructionCombining.cpp - Combine multiple instructions -----------===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// InstructionCombining - Combine instructions to form fewer, simple
// instructions. This pass does not modify the CFG This pass is where algebraic
// simplification happens.
//
// This pass combines things like:
// %Y = add int %X, 1
// %Z = add int %Y, 1
// into:
// %Z = add int %X, 2
//
// This is a simple worklist driven algorithm.
//
// This pass guarantees that the following canonicalizations are performed on
// the program:
// 1. If a binary operator has a constant operand, it is moved to the RHS
// 2. Bitwise operators with constant operands are always grouped so that
// shifts are performed first, then or's, then and's, then xor's.
// 3. SetCC instructions are converted from <,>,<=,>= to ==,!= if possible
// 4. All SetCC instructions on boolean values are replaced with logical ops
// 5. add X, X is represented as (X*2) => (X << 1)
// 6. Multiplies with a power-of-two constant argument are transformed into
// shifts.
// ... etc.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "instcombine"
#include "llvm/Transforms/Scalar.h"
#include "llvm/IntrinsicInst.h"
#include "llvm/Pass.h"
#include "llvm/DerivedTypes.h"
#include "llvm/GlobalVariable.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Support/CallSite.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/GetElementPtrTypeIterator.h"
#include "llvm/Support/InstVisitor.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/PatternMatch.h"
#include "llvm/Support/Compiler.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/STLExtras.h"
#include <algorithm>
#include <iostream>
using namespace llvm;
using namespace llvm::PatternMatch;
namespace {
Statistic<> NumCombined ("instcombine", "Number of insts combined");
Statistic<> NumConstProp("instcombine", "Number of constant folds");
Statistic<> NumDeadInst ("instcombine", "Number of dead inst eliminated");
Statistic<> NumDeadStore("instcombine", "Number of dead stores eliminated");
Statistic<> NumSunkInst ("instcombine", "Number of instructions sunk");
class VISIBILITY_HIDDEN InstCombiner
: public FunctionPass,
public InstVisitor<InstCombiner, Instruction*> {
// Worklist of all of the instructions that need to be simplified.
std::vector<Instruction*> WorkList;
TargetData *TD;
/// AddUsersToWorkList - When an instruction is simplified, add all users of
/// the instruction to the work lists because they might get more simplified
/// now.
///
void AddUsersToWorkList(Value &I) {
for (Value::use_iterator UI = I.use_begin(), UE = I.use_end();
UI != UE; ++UI)
WorkList.push_back(cast<Instruction>(*UI));
}
/// AddUsesToWorkList - When an instruction is simplified, add operands to
/// the work lists because they might get more simplified now.
///
void AddUsesToWorkList(Instruction &I) {
for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i)
if (Instruction *Op = dyn_cast<Instruction>(I.getOperand(i)))
WorkList.push_back(Op);
}
/// AddSoonDeadInstToWorklist - The specified instruction is about to become
/// dead. Add all of its operands to the worklist, turning them into
/// undef's to reduce the number of uses of those instructions.
///
/// Return the specified operand before it is turned into an undef.
///
Value *AddSoonDeadInstToWorklist(Instruction &I, unsigned op) {
Value *R = I.getOperand(op);
for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i)
if (Instruction *Op = dyn_cast<Instruction>(I.getOperand(i))) {
WorkList.push_back(Op);
// Set the operand to undef to drop the use.
I.setOperand(i, UndefValue::get(Op->getType()));
}
return R;
}
// removeFromWorkList - remove all instances of I from the worklist.
void removeFromWorkList(Instruction *I);
public:
virtual bool runOnFunction(Function &F);
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<TargetData>();
AU.addPreservedID(LCSSAID);
AU.setPreservesCFG();
}
TargetData &getTargetData() const { return *TD; }
// Visitation implementation - Implement instruction combining for different
// instruction types. The semantics are as follows:
// Return Value:
// null - No change was made
// I - Change was made, I is still valid, I may be dead though
// otherwise - Change was made, replace I with returned instruction
//
Instruction *visitAdd(BinaryOperator &I);
Instruction *visitSub(BinaryOperator &I);
Instruction *visitMul(BinaryOperator &I);
Instruction *visitURem(BinaryOperator &I);
Instruction *visitSRem(BinaryOperator &I);
Instruction *visitFRem(BinaryOperator &I);
Instruction *commonRemTransforms(BinaryOperator &I);
Instruction *commonIRemTransforms(BinaryOperator &I);
Instruction *commonDivTransforms(BinaryOperator &I);
Instruction *commonIDivTransforms(BinaryOperator &I);
Instruction *visitUDiv(BinaryOperator &I);
Instruction *visitSDiv(BinaryOperator &I);
Instruction *visitFDiv(BinaryOperator &I);
Instruction *visitAnd(BinaryOperator &I);
Instruction *visitOr (BinaryOperator &I);
Instruction *visitXor(BinaryOperator &I);
Instruction *visitSetCondInst(SetCondInst &I);
Instruction *visitSetCondInstWithCastAndCast(SetCondInst &SCI);
Instruction *FoldGEPSetCC(User *GEPLHS, Value *RHS,
Instruction::BinaryOps Cond, Instruction &I);
Instruction *visitShiftInst(ShiftInst &I);
Instruction *FoldShiftByConstant(Value *Op0, ConstantInt *Op1,
ShiftInst &I);
Instruction *visitCastInst(CastInst &CI);
Instruction *FoldSelectOpOp(SelectInst &SI, Instruction *TI,
Instruction *FI);
Instruction *visitSelectInst(SelectInst &CI);
Instruction *visitCallInst(CallInst &CI);
Instruction *visitInvokeInst(InvokeInst &II);
Instruction *visitPHINode(PHINode &PN);
Instruction *visitGetElementPtrInst(GetElementPtrInst &GEP);
Instruction *visitAllocationInst(AllocationInst &AI);
Instruction *visitFreeInst(FreeInst &FI);
Instruction *visitLoadInst(LoadInst &LI);
Instruction *visitStoreInst(StoreInst &SI);
Instruction *visitBranchInst(BranchInst &BI);
Instruction *visitSwitchInst(SwitchInst &SI);
Instruction *visitInsertElementInst(InsertElementInst &IE);
Instruction *visitExtractElementInst(ExtractElementInst &EI);
Instruction *visitShuffleVectorInst(ShuffleVectorInst &SVI);
// visitInstruction - Specify what to return for unhandled instructions...
Instruction *visitInstruction(Instruction &I) { return 0; }
private:
Instruction *visitCallSite(CallSite CS);
bool transformConstExprCastCall(CallSite CS);
public:
// InsertNewInstBefore - insert an instruction New before instruction Old
// in the program. Add the new instruction to the worklist.
//
Instruction *InsertNewInstBefore(Instruction *New, Instruction &Old) {
assert(New && New->getParent() == 0 &&
"New instruction already inserted into a basic block!");
BasicBlock *BB = Old.getParent();
BB->getInstList().insert(&Old, New); // Insert inst
WorkList.push_back(New); // Add to worklist
return New;
}
/// InsertCastBefore - Insert a cast of V to TY before the instruction POS.
/// This also adds the cast to the worklist. Finally, this returns the
/// cast.
Value *InsertCastBefore(Value *V, const Type *Ty, Instruction &Pos) {
if (V->getType() == Ty) return V;
if (Constant *CV = dyn_cast<Constant>(V))
return ConstantExpr::getCast(CV, Ty);
Instruction *C = new CastInst(V, Ty, V->getName(), &Pos);
WorkList.push_back(C);
return C;
}
// ReplaceInstUsesWith - This method is to be used when an instruction is
// found to be dead, replacable with another preexisting expression. Here
// we add all uses of I to the worklist, replace all uses of I with the new
// value, then return I, so that the inst combiner will know that I was
// modified.
//
Instruction *ReplaceInstUsesWith(Instruction &I, Value *V) {
AddUsersToWorkList(I); // Add all modified instrs to worklist
if (&I != V) {
I.replaceAllUsesWith(V);
return &I;
} else {
// If we are replacing the instruction with itself, this must be in a
// segment of unreachable code, so just clobber the instruction.
I.replaceAllUsesWith(UndefValue::get(I.getType()));
return &I;
}
}
// UpdateValueUsesWith - This method is to be used when an value is
// found to be replacable with another preexisting expression or was
// updated. Here we add all uses of I to the worklist, replace all uses of
// I with the new value (unless the instruction was just updated), then
// return true, so that the inst combiner will know that I was modified.
//
bool UpdateValueUsesWith(Value *Old, Value *New) {
AddUsersToWorkList(*Old); // Add all modified instrs to worklist
if (Old != New)
Old->replaceAllUsesWith(New);
if (Instruction *I = dyn_cast<Instruction>(Old))
WorkList.push_back(I);
if (Instruction *I = dyn_cast<Instruction>(New))
WorkList.push_back(I);
return true;
}
// EraseInstFromFunction - When dealing with an instruction that has side
// effects or produces a void value, we can't rely on DCE to delete the
// instruction. Instead, visit methods should return the value returned by
// this function.
Instruction *EraseInstFromFunction(Instruction &I) {
assert(I.use_empty() && "Cannot erase instruction that is used!");
AddUsesToWorkList(I);
removeFromWorkList(&I);
I.eraseFromParent();
return 0; // Don't do anything with FI
}
private:
/// InsertOperandCastBefore - This inserts a cast of V to DestTy before the
/// InsertBefore instruction. This is specialized a bit to avoid inserting
/// casts that are known to not do anything...
///
Value *InsertOperandCastBefore(Value *V, const Type *DestTy,
Instruction *InsertBefore);
// SimplifyCommutative - This performs a few simplifications for commutative
// operators.
bool SimplifyCommutative(BinaryOperator &I);
bool SimplifyDemandedBits(Value *V, uint64_t Mask,
uint64_t &KnownZero, uint64_t &KnownOne,
unsigned Depth = 0);
Value *SimplifyDemandedVectorElts(Value *V, uint64_t DemandedElts,
uint64_t &UndefElts, unsigned Depth = 0);
// FoldOpIntoPhi - Given a binary operator or cast instruction which has a
// PHI node as operand #0, see if we can fold the instruction into the PHI
// (which is only possible if all operands to the PHI are constants).
Instruction *FoldOpIntoPhi(Instruction &I);
// FoldPHIArgOpIntoPHI - If all operands to a PHI node are the same "unary"
// operator and they all are only used by the PHI, PHI together their
// inputs, and do the operation once, to the result of the PHI.
Instruction *FoldPHIArgOpIntoPHI(PHINode &PN);
Instruction *FoldPHIArgBinOpIntoPHI(PHINode &PN);
Instruction *OptAndOp(Instruction *Op, ConstantIntegral *OpRHS,
ConstantIntegral *AndRHS, BinaryOperator &TheAnd);
Value *FoldLogicalPlusAnd(Value *LHS, Value *RHS, ConstantIntegral *Mask,
bool isSub, Instruction &I);
Instruction *InsertRangeTest(Value *V, Constant *Lo, Constant *Hi,
bool Inside, Instruction &IB);
Instruction *PromoteCastOfAllocation(CastInst &CI, AllocationInst &AI);
Instruction *MatchBSwap(BinaryOperator &I);
Value *EvaluateInDifferentType(Value *V, const Type *Ty);
};
RegisterPass<InstCombiner> X("instcombine", "Combine redundant instructions");
}
// getComplexity: Assign a complexity or rank value to LLVM Values...
// 0 -> undef, 1 -> Const, 2 -> Other, 3 -> Arg, 3 -> Unary, 4 -> OtherInst
static unsigned getComplexity(Value *V) {
if (isa<Instruction>(V)) {
if (BinaryOperator::isNeg(V) || BinaryOperator::isNot(V))
return 3;
return 4;
}
if (isa<Argument>(V)) return 3;
return isa<Constant>(V) ? (isa<UndefValue>(V) ? 0 : 1) : 2;
}
// isOnlyUse - Return true if this instruction will be deleted if we stop using
// it.
static bool isOnlyUse(Value *V) {
return V->hasOneUse() || isa<Constant>(V);
}
// getPromotedType - Return the specified type promoted as it would be to pass
// though a va_arg area...
static const Type *getPromotedType(const Type *Ty) {
switch (Ty->getTypeID()) {
case Type::SByteTyID:
case Type::ShortTyID: return Type::IntTy;
case Type::UByteTyID:
case Type::UShortTyID: return Type::UIntTy;
case Type::FloatTyID: return Type::DoubleTy;
default: return Ty;
}
}
/// isCast - If the specified operand is a CastInst or a constant expr cast,
/// return the operand value, otherwise return null.
static Value *isCast(Value *V) {
if (CastInst *I = dyn_cast<CastInst>(V))
return I->getOperand(0);
else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
if (CE->getOpcode() == Instruction::Cast)
return CE->getOperand(0);
return 0;
}
enum CastType {
Noop = 0,
Truncate = 1,
Signext = 2,
Zeroext = 3
};
/// getCastType - In the future, we will split the cast instruction into these
/// various types. Until then, we have to do the analysis here.
static CastType getCastType(const Type *Src, const Type *Dest) {
assert(Src->isIntegral() && Dest->isIntegral() &&
"Only works on integral types!");
unsigned SrcSize = Src->getPrimitiveSizeInBits();
unsigned DestSize = Dest->getPrimitiveSizeInBits();
if (SrcSize == DestSize) return Noop;
if (SrcSize > DestSize) return Truncate;
if (Src->isSigned()) return Signext;
return Zeroext;
}
// isEliminableCastOfCast - Return true if it is valid to eliminate the CI
// instruction.
//
static bool isEliminableCastOfCast(const Type *SrcTy, const Type *MidTy,
const Type *DstTy, TargetData *TD) {
// It is legal to eliminate the instruction if casting A->B->A if the sizes
// are identical and the bits don't get reinterpreted (for example
// int->float->int would not be allowed).
if (SrcTy == DstTy && SrcTy->isLosslesslyConvertibleTo(MidTy))
return true;
// If we are casting between pointer and integer types, treat pointers as
// integers of the appropriate size for the code below.
if (isa<PointerType>(SrcTy)) SrcTy = TD->getIntPtrType();
if (isa<PointerType>(MidTy)) MidTy = TD->getIntPtrType();
if (isa<PointerType>(DstTy)) DstTy = TD->getIntPtrType();
// Allow free casting and conversion of sizes as long as the sign doesn't
// change...
if (SrcTy->isIntegral() && MidTy->isIntegral() && DstTy->isIntegral()) {
CastType FirstCast = getCastType(SrcTy, MidTy);
CastType SecondCast = getCastType(MidTy, DstTy);
// Capture the effect of these two casts. If the result is a legal cast,
// the CastType is stored here, otherwise a special code is used.
static const unsigned CastResult[] = {
// First cast is noop
0, 1, 2, 3,
// First cast is a truncate
1, 1, 4, 4, // trunc->extend is not safe to eliminate
// First cast is a sign ext
2, 5, 2, 4, // signext->zeroext never ok
// First cast is a zero ext
3, 5, 3, 3,
};
unsigned Result = CastResult[FirstCast*4+SecondCast];
switch (Result) {
default: assert(0 && "Illegal table value!");
case 0:
case 1:
case 2:
case 3:
// FIXME: in the future, when LLVM has explicit sign/zeroextends and
// truncates, we could eliminate more casts.
return (unsigned)getCastType(SrcTy, DstTy) == Result;
case 4:
return false; // Not possible to eliminate this here.
case 5:
// Sign or zero extend followed by truncate is always ok if the result
// is a truncate or noop.
CastType ResultCast = getCastType(SrcTy, DstTy);
if (ResultCast == Noop || ResultCast == Truncate)
return true;
// Otherwise we are still growing the value, we are only safe if the
// result will match the sign/zeroextendness of the result.
return ResultCast == FirstCast;
}
}
// If this is a cast from 'float -> double -> integer', cast from
// 'float -> integer' directly, as the value isn't changed by the
// float->double conversion.
if (SrcTy->isFloatingPoint() && MidTy->isFloatingPoint() &&
DstTy->isIntegral() &&
SrcTy->getPrimitiveSize() < MidTy->getPrimitiveSize())
return true;
// Packed type conversions don't modify bits.
if (isa<PackedType>(SrcTy) && isa<PackedType>(MidTy) &&isa<PackedType>(DstTy))
return true;
return false;
}
/// ValueRequiresCast - Return true if the cast from "V to Ty" actually results
/// in any code being generated. It does not require codegen if V is simple
/// enough or if the cast can be folded into other casts.
static bool ValueRequiresCast(const Value *V, const Type *Ty, TargetData *TD) {
if (V->getType() == Ty || isa<Constant>(V)) return false;
// If this is a noop cast, it isn't real codegen.
if (V->getType()->isLosslesslyConvertibleTo(Ty))
return false;
// If this is another cast that can be eliminated, it isn't codegen either.
if (const CastInst *CI = dyn_cast<CastInst>(V))
if (isEliminableCastOfCast(CI->getOperand(0)->getType(), CI->getType(), Ty,
TD))
return false;
return true;
}
/// InsertOperandCastBefore - This inserts a cast of V to DestTy before the
/// InsertBefore instruction. This is specialized a bit to avoid inserting
/// casts that are known to not do anything...
///
Value *InstCombiner::InsertOperandCastBefore(Value *V, const Type *DestTy,
Instruction *InsertBefore) {
if (V->getType() == DestTy) return V;
if (Constant *C = dyn_cast<Constant>(V))
return ConstantExpr::getCast(C, DestTy);
return InsertCastBefore(V, DestTy, *InsertBefore);
}
// SimplifyCommutative - This performs a few simplifications for commutative
// operators:
//
// 1. Order operands such that they are listed from right (least complex) to
// left (most complex). This puts constants before unary operators before
// binary operators.
//
// 2. Transform: (op (op V, C1), C2) ==> (op V, (op C1, C2))
// 3. Transform: (op (op V1, C1), (op V2, C2)) ==> (op (op V1, V2), (op C1,C2))
//
bool InstCombiner::SimplifyCommutative(BinaryOperator &I) {
bool Changed = false;
if (getComplexity(I.getOperand(0)) < getComplexity(I.getOperand(1)))
Changed = !I.swapOperands();
if (!I.isAssociative()) return Changed;
Instruction::BinaryOps Opcode = I.getOpcode();
if (BinaryOperator *Op = dyn_cast<BinaryOperator>(I.getOperand(0)))
if (Op->getOpcode() == Opcode && isa<Constant>(Op->getOperand(1))) {
if (isa<Constant>(I.getOperand(1))) {
Constant *Folded = ConstantExpr::get(I.getOpcode(),
cast<Constant>(I.getOperand(1)),
cast<Constant>(Op->getOperand(1)));
I.setOperand(0, Op->getOperand(0));
I.setOperand(1, Folded);
return true;
} else if (BinaryOperator *Op1=dyn_cast<BinaryOperator>(I.getOperand(1)))
if (Op1->getOpcode() == Opcode && isa<Constant>(Op1->getOperand(1)) &&
isOnlyUse(Op) && isOnlyUse(Op1)) {
Constant *C1 = cast<Constant>(Op->getOperand(1));
Constant *C2 = cast<Constant>(Op1->getOperand(1));
// Fold (op (op V1, C1), (op V2, C2)) ==> (op (op V1, V2), (op C1,C2))
Constant *Folded = ConstantExpr::get(I.getOpcode(), C1, C2);
Instruction *New = BinaryOperator::create(Opcode, Op->getOperand(0),
Op1->getOperand(0),
Op1->getName(), &I);
WorkList.push_back(New);
I.setOperand(0, New);
I.setOperand(1, Folded);
return true;
}
}
return Changed;
}
// dyn_castNegVal - Given a 'sub' instruction, return the RHS of the instruction
// if the LHS is a constant zero (which is the 'negate' form).
//
static inline Value *dyn_castNegVal(Value *V) {
if (BinaryOperator::isNeg(V))
return BinaryOperator::getNegArgument(V);
// Constants can be considered to be negated values if they can be folded.
if (ConstantInt *C = dyn_cast<ConstantInt>(V))
return ConstantExpr::getNeg(C);
return 0;
}
static inline Value *dyn_castNotVal(Value *V) {
if (BinaryOperator::isNot(V))
return BinaryOperator::getNotArgument(V);
// Constants can be considered to be not'ed values...
if (ConstantIntegral *C = dyn_cast<ConstantIntegral>(V))
return ConstantExpr::getNot(C);
return 0;
}
// dyn_castFoldableMul - If this value is a multiply that can be folded into
// other computations (because it has a constant operand), return the
// non-constant operand of the multiply, and set CST to point to the multiplier.
// Otherwise, return null.
//
static inline Value *dyn_castFoldableMul(Value *V, ConstantInt *&CST) {
if (V->hasOneUse() && V->getType()->isInteger())
if (Instruction *I = dyn_cast<Instruction>(V)) {
if (I->getOpcode() == Instruction::Mul)
if ((CST = dyn_cast<ConstantInt>(I->getOperand(1))))
return I->getOperand(0);
if (I->getOpcode() == Instruction::Shl)
if ((CST = dyn_cast<ConstantInt>(I->getOperand(1)))) {
// The multiplier is really 1 << CST.
Constant *One = ConstantInt::get(V->getType(), 1);
CST = cast<ConstantInt>(ConstantExpr::getShl(One, CST));
return I->getOperand(0);
}
}
return 0;
}
/// dyn_castGetElementPtr - If this is a getelementptr instruction or constant
/// expression, return it.
static User *dyn_castGetElementPtr(Value *V) {
if (isa<GetElementPtrInst>(V)) return cast<User>(V);
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
if (CE->getOpcode() == Instruction::GetElementPtr)
return cast<User>(V);
return false;
}
// AddOne, SubOne - Add or subtract a constant one from an integer constant...
static ConstantInt *AddOne(ConstantInt *C) {
return cast<ConstantInt>(ConstantExpr::getAdd(C,
ConstantInt::get(C->getType(), 1)));
}
static ConstantInt *SubOne(ConstantInt *C) {
return cast<ConstantInt>(ConstantExpr::getSub(C,
ConstantInt::get(C->getType(), 1)));
}
/// GetConstantInType - Return a ConstantInt with the specified type and value.
///
static ConstantIntegral *GetConstantInType(const Type *Ty, uint64_t Val) {
if (Ty->isUnsigned())
return ConstantInt::get(Ty, Val);
else if (Ty->getTypeID() == Type::BoolTyID)
return ConstantBool::get(Val);
int64_t SVal = Val;
SVal <<= 64-Ty->getPrimitiveSizeInBits();
SVal >>= 64-Ty->getPrimitiveSizeInBits();
return ConstantInt::get(Ty, SVal);
}
/// ComputeMaskedBits - Determine which of the bits specified in Mask are
/// known to be either zero or one and return them in the KnownZero/KnownOne
/// bitsets. This code only analyzes bits in Mask, in order to short-circuit
/// processing.
static void ComputeMaskedBits(Value *V, uint64_t Mask, uint64_t &KnownZero,
uint64_t &KnownOne, unsigned Depth = 0) {
// Note, we cannot consider 'undef' to be "IsZero" here. The problem is that
// we cannot optimize based on the assumption that it is zero without changing
// it to be an explicit zero. If we don't change it to zero, other code could
// optimized based on the contradictory assumption that it is non-zero.
// Because instcombine aggressively folds operations with undef args anyway,
// this won't lose us code quality.
if (ConstantIntegral *CI = dyn_cast<ConstantIntegral>(V)) {
// We know all of the bits for a constant!
KnownOne = CI->getZExtValue() & Mask;
KnownZero = ~KnownOne & Mask;
return;
}
KnownZero = KnownOne = 0; // Don't know anything.
if (Depth == 6 || Mask == 0)
return; // Limit search depth.
uint64_t KnownZero2, KnownOne2;
Instruction *I = dyn_cast<Instruction>(V);
if (!I) return;
Mask &= V->getType()->getIntegralTypeMask();
switch (I->getOpcode()) {
case Instruction::And:
// If either the LHS or the RHS are Zero, the result is zero.
ComputeMaskedBits(I->getOperand(1), Mask, KnownZero, KnownOne, Depth+1);
Mask &= ~KnownZero;
ComputeMaskedBits(I->getOperand(0), Mask, KnownZero2, KnownOne2, Depth+1);
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
// Output known-1 bits are only known if set in both the LHS & RHS.
KnownOne &= KnownOne2;
// Output known-0 are known to be clear if zero in either the LHS | RHS.
KnownZero |= KnownZero2;
return;
case Instruction::Or:
ComputeMaskedBits(I->getOperand(1), Mask, KnownZero, KnownOne, Depth+1);
Mask &= ~KnownOne;
ComputeMaskedBits(I->getOperand(0), Mask, KnownZero2, KnownOne2, Depth+1);
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
// Output known-0 bits are only known if clear in both the LHS & RHS.
KnownZero &= KnownZero2;
// Output known-1 are known to be set if set in either the LHS | RHS.
KnownOne |= KnownOne2;
return;
case Instruction::Xor: {
ComputeMaskedBits(I->getOperand(1), Mask, KnownZero, KnownOne, Depth+1);
ComputeMaskedBits(I->getOperand(0), Mask, KnownZero2, KnownOne2, Depth+1);
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
// Output known-0 bits are known if clear or set in both the LHS & RHS.
uint64_t KnownZeroOut = (KnownZero & KnownZero2) | (KnownOne & KnownOne2);
// Output known-1 are known to be set if set in only one of the LHS, RHS.
KnownOne = (KnownZero & KnownOne2) | (KnownOne & KnownZero2);
KnownZero = KnownZeroOut;
return;
}
case Instruction::Select:
ComputeMaskedBits(I->getOperand(2), Mask, KnownZero, KnownOne, Depth+1);
ComputeMaskedBits(I->getOperand(1), Mask, KnownZero2, KnownOne2, Depth+1);
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
// Only known if known in both the LHS and RHS.
KnownOne &= KnownOne2;
KnownZero &= KnownZero2;
return;
case Instruction::Cast: {
const Type *SrcTy = I->getOperand(0)->getType();
if (!SrcTy->isIntegral()) return;
// If this is an integer truncate or noop, just look in the input.
if (SrcTy->getPrimitiveSizeInBits() >=
I->getType()->getPrimitiveSizeInBits()) {
ComputeMaskedBits(I->getOperand(0), Mask, KnownZero, KnownOne, Depth+1);
return;
}
// Sign or Zero extension. Compute the bits in the result that are not
// present in the input.
uint64_t NotIn = ~SrcTy->getIntegralTypeMask();
uint64_t NewBits = I->getType()->getIntegralTypeMask() & NotIn;
// Handle zero extension.
if (!SrcTy->isSigned()) {
Mask &= SrcTy->getIntegralTypeMask();
ComputeMaskedBits(I->getOperand(0), Mask, KnownZero, KnownOne, Depth+1);
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
// The top bits are known to be zero.
KnownZero |= NewBits;
} else {
// Sign extension.
Mask &= SrcTy->getIntegralTypeMask();
ComputeMaskedBits(I->getOperand(0), Mask, KnownZero, KnownOne, Depth+1);
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
// If the sign bit of the input is known set or clear, then we know the
// top bits of the result.
uint64_t InSignBit = 1ULL << (SrcTy->getPrimitiveSizeInBits()-1);
if (KnownZero & InSignBit) { // Input sign bit known zero
KnownZero |= NewBits;
KnownOne &= ~NewBits;
} else if (KnownOne & InSignBit) { // Input sign bit known set
KnownOne |= NewBits;
KnownZero &= ~NewBits;
} else { // Input sign bit unknown
KnownZero &= ~NewBits;
KnownOne &= ~NewBits;
}
}
return;
}
case Instruction::Shl:
// (shl X, C1) & C2 == 0 iff (X & C2 >>u C1) == 0
if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) {
uint64_t ShiftAmt = SA->getZExtValue();
Mask >>= ShiftAmt;
ComputeMaskedBits(I->getOperand(0), Mask, KnownZero, KnownOne, Depth+1);
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
KnownZero <<= ShiftAmt;
KnownOne <<= ShiftAmt;
KnownZero |= (1ULL << ShiftAmt)-1; // low bits known zero.
return;
}
break;
case Instruction::LShr:
// (ushr X, C1) & C2 == 0 iff (-1 >> C1) & C2 == 0
if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) {
// Compute the new bits that are at the top now.
uint64_t ShiftAmt = SA->getZExtValue();
uint64_t HighBits = (1ULL << ShiftAmt)-1;
HighBits <<= I->getType()->getPrimitiveSizeInBits()-ShiftAmt;
// Unsigned shift right.
Mask <<= ShiftAmt;
ComputeMaskedBits(I->getOperand(0), Mask, KnownZero,KnownOne,Depth+1);
assert((KnownZero & KnownOne) == 0&&"Bits known to be one AND zero?");
KnownZero >>= ShiftAmt;
KnownOne >>= ShiftAmt;
KnownZero |= HighBits; // high bits known zero.
return;
}
break;
case Instruction::AShr:
// (ushr X, C1) & C2 == 0 iff (-1 >> C1) & C2 == 0
if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) {
// Compute the new bits that are at the top now.
uint64_t ShiftAmt = SA->getZExtValue();
uint64_t HighBits = (1ULL << ShiftAmt)-1;
HighBits <<= I->getType()->getPrimitiveSizeInBits()-ShiftAmt;
// Signed shift right.
Mask <<= ShiftAmt;
ComputeMaskedBits(I->getOperand(0), Mask, KnownZero,KnownOne,Depth+1);
assert((KnownZero & KnownOne) == 0&&"Bits known to be one AND zero?");
KnownZero >>= ShiftAmt;
KnownOne >>= ShiftAmt;
// Handle the sign bits.
uint64_t SignBit = 1ULL << (I->getType()->getPrimitiveSizeInBits()-1);
SignBit >>= ShiftAmt; // Adjust to where it is now in the mask.
if (KnownZero & SignBit) { // New bits are known zero.
KnownZero |= HighBits;
} else if (KnownOne & SignBit) { // New bits are known one.
KnownOne |= HighBits;
}
return;
}
break;
}
}
/// MaskedValueIsZero - Return true if 'V & Mask' is known to be zero. We use
/// this predicate to simplify operations downstream. Mask is known to be zero
/// for bits that V cannot have.
static bool MaskedValueIsZero(Value *V, uint64_t Mask, unsigned Depth = 0) {
uint64_t KnownZero, KnownOne;
ComputeMaskedBits(V, Mask, KnownZero, KnownOne, Depth);
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
return (KnownZero & Mask) == Mask;
}
/// ShrinkDemandedConstant - Check to see if the specified operand of the
/// specified instruction is a constant integer. If so, check to see if there
/// are any bits set in the constant that are not demanded. If so, shrink the
/// constant and return true.
static bool ShrinkDemandedConstant(Instruction *I, unsigned OpNo,
uint64_t Demanded) {
ConstantInt *OpC = dyn_cast<ConstantInt>(I->getOperand(OpNo));
if (!OpC) return false;
// If there are no bits set that aren't demanded, nothing to do.
if ((~Demanded & OpC->getZExtValue()) == 0)
return false;
// This is producing any bits that are not needed, shrink the RHS.
uint64_t Val = Demanded & OpC->getZExtValue();
I->setOperand(OpNo, GetConstantInType(OpC->getType(), Val));
return true;
}
// ComputeSignedMinMaxValuesFromKnownBits - Given a signed integer type and a
// set of known zero and one bits, compute the maximum and minimum values that
// could have the specified known zero and known one bits, returning them in
// min/max.
static void ComputeSignedMinMaxValuesFromKnownBits(const Type *Ty,
uint64_t KnownZero,
uint64_t KnownOne,
int64_t &Min, int64_t &Max) {
uint64_t TypeBits = Ty->getIntegralTypeMask();
uint64_t UnknownBits = ~(KnownZero|KnownOne) & TypeBits;
uint64_t SignBit = 1ULL << (Ty->getPrimitiveSizeInBits()-1);
// The minimum value is when all unknown bits are zeros, EXCEPT for the sign
// bit if it is unknown.
Min = KnownOne;
Max = KnownOne|UnknownBits;
if (SignBit & UnknownBits) { // Sign bit is unknown
Min |= SignBit;
Max &= ~SignBit;
}
// Sign extend the min/max values.
int ShAmt = 64-Ty->getPrimitiveSizeInBits();
Min = (Min << ShAmt) >> ShAmt;
Max = (Max << ShAmt) >> ShAmt;
}
// ComputeUnsignedMinMaxValuesFromKnownBits - Given an unsigned integer type and
// a set of known zero and one bits, compute the maximum and minimum values that
// could have the specified known zero and known one bits, returning them in
// min/max.
static void ComputeUnsignedMinMaxValuesFromKnownBits(const Type *Ty,
uint64_t KnownZero,
uint64_t KnownOne,
uint64_t &Min,
uint64_t &Max) {
uint64_t TypeBits = Ty->getIntegralTypeMask();
uint64_t UnknownBits = ~(KnownZero|KnownOne) & TypeBits;
// The minimum value is when the unknown bits are all zeros.
Min = KnownOne;
// The maximum value is when the unknown bits are all ones.
Max = KnownOne|UnknownBits;
}
/// SimplifyDemandedBits - Look at V. At this point, we know that only the
/// DemandedMask bits of the result of V are ever used downstream. If we can
/// use this information to simplify V, do so and return true. Otherwise,
/// analyze the expression and return a mask of KnownOne and KnownZero bits for
/// the expression (used to simplify the caller). The KnownZero/One bits may
/// only be accurate for those bits in the DemandedMask.
bool InstCombiner::SimplifyDemandedBits(Value *V, uint64_t DemandedMask,
uint64_t &KnownZero, uint64_t &KnownOne,
unsigned Depth) {
if (ConstantIntegral *CI = dyn_cast<ConstantIntegral>(V)) {
// We know all of the bits for a constant!
KnownOne = CI->getZExtValue() & DemandedMask;
KnownZero = ~KnownOne & DemandedMask;
return false;
}
KnownZero = KnownOne = 0;
if (!V->hasOneUse()) { // Other users may use these bits.
if (Depth != 0) { // Not at the root.
// Just compute the KnownZero/KnownOne bits to simplify things downstream.
ComputeMaskedBits(V, DemandedMask, KnownZero, KnownOne, Depth);
return false;
}
// If this is the root being simplified, allow it to have multiple uses,
// just set the DemandedMask to all bits.
DemandedMask = V->getType()->getIntegralTypeMask();
} else if (DemandedMask == 0) { // Not demanding any bits from V.
if (V != UndefValue::get(V->getType()))
return UpdateValueUsesWith(V, UndefValue::get(V->getType()));
return false;
} else if (Depth == 6) { // Limit search depth.
return false;
}
Instruction *I = dyn_cast<Instruction>(V);
if (!I) return false; // Only analyze instructions.
DemandedMask &= V->getType()->getIntegralTypeMask();
uint64_t KnownZero2, KnownOne2;
switch (I->getOpcode()) {
default: break;
case Instruction::And:
// If either the LHS or the RHS are Zero, the result is zero.
if (SimplifyDemandedBits(I->getOperand(1), DemandedMask,
KnownZero, KnownOne, Depth+1))
return true;
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
// If something is known zero on the RHS, the bits aren't demanded on the
// LHS.
if (SimplifyDemandedBits(I->getOperand(0), DemandedMask & ~KnownZero,
KnownZero2, KnownOne2, Depth+1))
return true;
assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
// If all of the demanded bits are known one on one side, return the other.
// These bits cannot contribute to the result of the 'and'.
if ((DemandedMask & ~KnownZero2 & KnownOne) == (DemandedMask & ~KnownZero2))
return UpdateValueUsesWith(I, I->getOperand(0));
if ((DemandedMask & ~KnownZero & KnownOne2) == (DemandedMask & ~KnownZero))
return UpdateValueUsesWith(I, I->getOperand(1));
// If all of the demanded bits in the inputs are known zeros, return zero.
if ((DemandedMask & (KnownZero|KnownZero2)) == DemandedMask)
return UpdateValueUsesWith(I, Constant::getNullValue(I->getType()));
// If the RHS is a constant, see if we can simplify it.
if (ShrinkDemandedConstant(I, 1, DemandedMask & ~KnownZero2))
return UpdateValueUsesWith(I, I);
// Output known-1 bits are only known if set in both the LHS & RHS.
KnownOne &= KnownOne2;
// Output known-0 are known to be clear if zero in either the LHS | RHS.
KnownZero |= KnownZero2;
break;
case Instruction::Or:
if (SimplifyDemandedBits(I->getOperand(1), DemandedMask,
KnownZero, KnownOne, Depth+1))
return true;
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
if (SimplifyDemandedBits(I->getOperand(0), DemandedMask & ~KnownOne,
KnownZero2, KnownOne2, Depth+1))
return true;
assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
// If all of the demanded bits are known zero on one side, return the other.
// These bits cannot contribute to the result of the 'or'.
if ((DemandedMask & ~KnownOne2 & KnownZero) == (DemandedMask & ~KnownOne2))
return UpdateValueUsesWith(I, I->getOperand(0));
if ((DemandedMask & ~KnownOne & KnownZero2) == (DemandedMask & ~KnownOne))
return UpdateValueUsesWith(I, I->getOperand(1));
// If all of the potentially set bits on one side are known to be set on
// the other side, just use the 'other' side.
if ((DemandedMask & (~KnownZero) & KnownOne2) ==
(DemandedMask & (~KnownZero)))
return UpdateValueUsesWith(I, I->getOperand(0));
if ((DemandedMask & (~KnownZero2) & KnownOne) ==
(DemandedMask & (~KnownZero2)))
return UpdateValueUsesWith(I, I->getOperand(1));
// If the RHS is a constant, see if we can simplify it.
if (ShrinkDemandedConstant(I, 1, DemandedMask))
return UpdateValueUsesWith(I, I);
// Output known-0 bits are only known if clear in both the LHS & RHS.
KnownZero &= KnownZero2;
// Output known-1 are known to be set if set in either the LHS | RHS.
KnownOne |= KnownOne2;
break;
case Instruction::Xor: {
if (SimplifyDemandedBits(I->getOperand(1), DemandedMask,
KnownZero, KnownOne, Depth+1))
return true;
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
if (SimplifyDemandedBits(I->getOperand(0), DemandedMask,
KnownZero2, KnownOne2, Depth+1))
return true;
assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
// If all of the demanded bits are known zero on one side, return the other.
// These bits cannot contribute to the result of the 'xor'.
if ((DemandedMask & KnownZero) == DemandedMask)
return UpdateValueUsesWith(I, I->getOperand(0));
if ((DemandedMask & KnownZero2) == DemandedMask)
return UpdateValueUsesWith(I, I->getOperand(1));
// Output known-0 bits are known if clear or set in both the LHS & RHS.
uint64_t KnownZeroOut = (KnownZero & KnownZero2) | (KnownOne & KnownOne2);
// Output known-1 are known to be set if set in only one of the LHS, RHS.
uint64_t KnownOneOut = (KnownZero & KnownOne2) | (KnownOne & KnownZero2);
// If all of the unknown bits are known to be zero on one side or the other
// (but not both) turn this into an *inclusive* or.
// e.g. (A & C1)^(B & C2) -> (A & C1)|(B & C2) iff C1&C2 == 0
if (uint64_t UnknownBits = DemandedMask & ~(KnownZeroOut|KnownOneOut)) {
if ((UnknownBits & (KnownZero|KnownZero2)) == UnknownBits) {
Instruction *Or =
BinaryOperator::createOr(I->getOperand(0), I->getOperand(1),
I->getName());
InsertNewInstBefore(Or, *I);
return UpdateValueUsesWith(I, Or);
}
}
// If all of the demanded bits on one side are known, and all of the set
// bits on that side are also known to be set on the other side, turn this
// into an AND, as we know the bits will be cleared.
// e.g. (X | C1) ^ C2 --> (X | C1) & ~C2 iff (C1&C2) == C2
if ((DemandedMask & (KnownZero|KnownOne)) == DemandedMask) { // all known
if ((KnownOne & KnownOne2) == KnownOne) {
Constant *AndC = GetConstantInType(I->getType(),
~KnownOne & DemandedMask);
Instruction *And =
BinaryOperator::createAnd(I->getOperand(0), AndC, "tmp");
InsertNewInstBefore(And, *I);
return UpdateValueUsesWith(I, And);
}
}
// If the RHS is a constant, see if we can simplify it.
// FIXME: for XOR, we prefer to force bits to 1 if they will make a -1.
if (ShrinkDemandedConstant(I, 1, DemandedMask))
return UpdateValueUsesWith(I, I);
KnownZero = KnownZeroOut;
KnownOne = KnownOneOut;
break;
}
case Instruction::Select:
if (SimplifyDemandedBits(I->getOperand(2), DemandedMask,
KnownZero, KnownOne, Depth+1))
return true;
if (SimplifyDemandedBits(I->getOperand(1), DemandedMask,
KnownZero2, KnownOne2, Depth+1))
return true;
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
// If the operands are constants, see if we can simplify them.
if (ShrinkDemandedConstant(I, 1, DemandedMask))
return UpdateValueUsesWith(I, I);
if (ShrinkDemandedConstant(I, 2, DemandedMask))
return UpdateValueUsesWith(I, I);
// Only known if known in both the LHS and RHS.
KnownOne &= KnownOne2;
KnownZero &= KnownZero2;
break;
case Instruction::Cast: {
const Type *SrcTy = I->getOperand(0)->getType();
if (!SrcTy->isIntegral()) return false;
// If this is an integer truncate or noop, just look in the input.
if (SrcTy->getPrimitiveSizeInBits() >=
I->getType()->getPrimitiveSizeInBits()) {
// Cast to bool is a comparison against 0, which demands all bits. We
// can't propagate anything useful up.
if (I->getType() == Type::BoolTy)
break;
if (SimplifyDemandedBits(I->getOperand(0), DemandedMask,
KnownZero, KnownOne, Depth+1))
return true;
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
break;
}
// Sign or Zero extension. Compute the bits in the result that are not
// present in the input.
uint64_t NotIn = ~SrcTy->getIntegralTypeMask();
uint64_t NewBits = I->getType()->getIntegralTypeMask() & NotIn;
// Handle zero extension.
if (!SrcTy->isSigned()) {
DemandedMask &= SrcTy->getIntegralTypeMask();
if (SimplifyDemandedBits(I->getOperand(0), DemandedMask,
KnownZero, KnownOne, Depth+1))
return true;
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
// The top bits are known to be zero.
KnownZero |= NewBits;
} else {
// Sign extension.
uint64_t InSignBit = 1ULL << (SrcTy->getPrimitiveSizeInBits()-1);
int64_t InputDemandedBits = DemandedMask & SrcTy->getIntegralTypeMask();
// If any of the sign extended bits are demanded, we know that the sign
// bit is demanded.
if (NewBits & DemandedMask)
InputDemandedBits |= InSignBit;
if (SimplifyDemandedBits(I->getOperand(0), InputDemandedBits,
KnownZero, KnownOne, Depth+1))
return true;
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
// If the sign bit of the input is known set or clear, then we know the
// top bits of the result.
// If the input sign bit is known zero, or if the NewBits are not demanded
// convert this into a zero extension.
if ((KnownZero & InSignBit) || (NewBits & ~DemandedMask) == NewBits) {
// Convert to unsigned first.
Value *NewVal =
InsertCastBefore(I->getOperand(0), SrcTy->getUnsignedVersion(), *I);
// Then cast that to the destination type.
NewVal = new CastInst(NewVal, I->getType(), I->getName());
InsertNewInstBefore(cast<Instruction>(NewVal), *I);
return UpdateValueUsesWith(I, NewVal);
} else if (KnownOne & InSignBit) { // Input sign bit known set
KnownOne |= NewBits;
KnownZero &= ~NewBits;
} else { // Input sign bit unknown
KnownZero &= ~NewBits;
KnownOne &= ~NewBits;
}
}
break;
}
case Instruction::Shl:
if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) {
uint64_t ShiftAmt = SA->getZExtValue();
if (SimplifyDemandedBits(I->getOperand(0), DemandedMask >> ShiftAmt,
KnownZero, KnownOne, Depth+1))
return true;
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
KnownZero <<= ShiftAmt;
KnownOne <<= ShiftAmt;
KnownZero |= (1ULL << ShiftAmt) - 1; // low bits known zero.
}
break;
case Instruction::LShr:
// For a logical shift right
if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) {
unsigned ShiftAmt = SA->getZExtValue();
// Compute the new bits that are at the top now.
uint64_t HighBits = (1ULL << ShiftAmt)-1;
HighBits <<= I->getType()->getPrimitiveSizeInBits() - ShiftAmt;
uint64_t TypeMask = I->getType()->getIntegralTypeMask();
// Unsigned shift right.
if (SimplifyDemandedBits(I->getOperand(0),
(DemandedMask << ShiftAmt) & TypeMask,
KnownZero, KnownOne, Depth+1))
return true;
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
KnownZero &= TypeMask;
KnownOne &= TypeMask;
KnownZero >>= ShiftAmt;
KnownOne >>= ShiftAmt;
KnownZero |= HighBits; // high bits known zero.
}
break;
case Instruction::AShr:
// If this is an arithmetic shift right and only the low-bit is set, we can
// always convert this into a logical shr, even if the shift amount is
// variable. The low bit of the shift cannot be an input sign bit unless
// the shift amount is >= the size of the datatype, which is undefined.
if (DemandedMask == 1) {
// Perform the logical shift right.
Value *NewVal = new ShiftInst(Instruction::LShr, I->getOperand(0),
I->getOperand(1), I->getName());
InsertNewInstBefore(cast<Instruction>(NewVal), *I);
return UpdateValueUsesWith(I, NewVal);
}
if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) {
unsigned ShiftAmt = SA->getZExtValue();
// Compute the new bits that are at the top now.
uint64_t HighBits = (1ULL << ShiftAmt)-1;
HighBits <<= I->getType()->getPrimitiveSizeInBits() - ShiftAmt;
uint64_t TypeMask = I->getType()->getIntegralTypeMask();
// Signed shift right.
if (SimplifyDemandedBits(I->getOperand(0),
(DemandedMask << ShiftAmt) & TypeMask,
KnownZero, KnownOne, Depth+1))
return true;
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
KnownZero &= TypeMask;
KnownOne &= TypeMask;
KnownZero >>= ShiftAmt;
KnownOne >>= ShiftAmt;
// Handle the sign bits.
uint64_t SignBit = 1ULL << (I->getType()->getPrimitiveSizeInBits()-1);
SignBit >>= ShiftAmt; // Adjust to where it is now in the mask.
// If the input sign bit is known to be zero, or if none of the top bits
// are demanded, turn this into an unsigned shift right.
if ((KnownZero & SignBit) || (HighBits & ~DemandedMask) == HighBits) {
// Perform the logical shift right.
Value *NewVal = new ShiftInst(Instruction::LShr, I->getOperand(0),
SA, I->getName());
InsertNewInstBefore(cast<Instruction>(NewVal), *I);
return UpdateValueUsesWith(I, NewVal);
} else if (KnownOne & SignBit) { // New bits are known one.
KnownOne |= HighBits;
}
}
break;
}
// If the client is only demanding bits that we know, return the known
// constant.
if ((DemandedMask & (KnownZero|KnownOne)) == DemandedMask)
return UpdateValueUsesWith(I, GetConstantInType(I->getType(), KnownOne));
return false;
}
/// SimplifyDemandedVectorElts - The specified value producecs a vector with
/// 64 or fewer elements. DemandedElts contains the set of elements that are
/// actually used by the caller. This method analyzes which elements of the
/// operand are undef and returns that information in UndefElts.
///
/// If the information about demanded elements can be used to simplify the
/// operation, the operation is simplified, then the resultant value is
/// returned. This returns null if no change was made.
Value *InstCombiner::SimplifyDemandedVectorElts(Value *V, uint64_t DemandedElts,
uint64_t &UndefElts,
unsigned Depth) {
unsigned VWidth = cast<PackedType>(V->getType())->getNumElements();
assert(VWidth <= 64 && "Vector too wide to analyze!");
uint64_t EltMask = ~0ULL >> (64-VWidth);
assert(DemandedElts != EltMask && (DemandedElts & ~EltMask) == 0 &&
"Invalid DemandedElts!");
if (isa<UndefValue>(V)) {
// If the entire vector is undefined, just return this info.
UndefElts = EltMask;
return 0;
} else if (DemandedElts == 0) { // If nothing is demanded, provide undef.
UndefElts = EltMask;
return UndefValue::get(V->getType());
}
UndefElts = 0;
if (ConstantPacked *CP = dyn_cast<ConstantPacked>(V)) {
const Type *EltTy = cast<PackedType>(V->getType())->getElementType();
Constant *Undef = UndefValue::get(EltTy);
std::vector<Constant*> Elts;
for (unsigned i = 0; i != VWidth; ++i)
if (!(DemandedElts & (1ULL << i))) { // If not demanded, set to undef.
Elts.push_back(Undef);
UndefElts |= (1ULL << i);
} else if (isa<UndefValue>(CP->getOperand(i))) { // Already undef.
Elts.push_back(Undef);
UndefElts |= (1ULL << i);
} else { // Otherwise, defined.
Elts.push_back(CP->getOperand(i));
}
// If we changed the constant, return it.
Constant *NewCP = ConstantPacked::get(Elts);
return NewCP != CP ? NewCP : 0;
} else if (isa<ConstantAggregateZero>(V)) {
// Simplify the CAZ to a ConstantPacked where the non-demanded elements are
// set to undef.
const Type *EltTy = cast<PackedType>(V->getType())->getElementType();
Constant *Zero = Constant::getNullValue(EltTy);
Constant *Undef = UndefValue::get(EltTy);
std::vector<Constant*> Elts;
for (unsigned i = 0; i != VWidth; ++i)
Elts.push_back((DemandedElts & (1ULL << i)) ? Zero : Undef);
UndefElts = DemandedElts ^ EltMask;
return ConstantPacked::get(Elts);
}
if (!V->hasOneUse()) { // Other users may use these bits.
if (Depth != 0) { // Not at the root.
// TODO: Just compute the UndefElts information recursively.
return false;
}
return false;
} else if (Depth == 10) { // Limit search depth.
return false;
}
Instruction *I = dyn_cast<Instruction>(V);
if (!I) return false; // Only analyze instructions.
bool MadeChange = false;
uint64_t UndefElts2;
Value *TmpV;
switch (I->getOpcode()) {
default: break;
case Instruction::InsertElement: {
// If this is a variable index, we don't know which element it overwrites.
// demand exactly the same input as we produce.
ConstantInt *Idx = dyn_cast<ConstantInt>(I->getOperand(2));
if (Idx == 0) {
// Note that we can't propagate undef elt info, because we don't know
// which elt is getting updated.
TmpV = SimplifyDemandedVectorElts(I->getOperand(0), DemandedElts,
UndefElts2, Depth+1);
if (TmpV) { I->setOperand(0, TmpV); MadeChange = true; }
break;
}
// If this is inserting an element that isn't demanded, remove this
// insertelement.
unsigned IdxNo = Idx->getZExtValue();
if (IdxNo >= VWidth || (DemandedElts & (1ULL << IdxNo)) == 0)
return AddSoonDeadInstToWorklist(*I, 0);
// Otherwise, the element inserted overwrites whatever was there, so the
// input demanded set is simpler than the output set.
TmpV = SimplifyDemandedVectorElts(I->getOperand(0),
DemandedElts & ~(1ULL << IdxNo),
UndefElts, Depth+1);
if (TmpV) { I->setOperand(0, TmpV); MadeChange = true; }
// The inserted element is defined.
UndefElts |= 1ULL << IdxNo;
break;
}
case Instruction::And:
case Instruction::Or:
case Instruction::Xor:
case Instruction::Add:
case Instruction::Sub:
case Instruction::Mul:
// div/rem demand all inputs, because they don't want divide by zero.
TmpV = SimplifyDemandedVectorElts(I->getOperand(0), DemandedElts,
UndefElts, Depth+1);
if (TmpV) { I->setOperand(0, TmpV); MadeChange = true; }
TmpV = SimplifyDemandedVectorElts(I->getOperand(1), DemandedElts,
UndefElts2, Depth+1);
if (TmpV) { I->setOperand(1, TmpV); MadeChange = true; }
// Output elements are undefined if both are undefined. Consider things
// like undef&0. The result is known zero, not undef.
UndefElts &= UndefElts2;
break;
case Instruction::Call: {
IntrinsicInst *II = dyn_cast<IntrinsicInst>(I);
if (!II) break;
switch (II->getIntrinsicID()) {
default: break;
// Binary vector operations that work column-wise. A dest element is a
// function of the corresponding input elements from the two inputs.
case Intrinsic::x86_sse_sub_ss:
case Intrinsic::x86_sse_mul_ss:
case Intrinsic::x86_sse_min_ss:
case Intrinsic::x86_sse_max_ss:
case Intrinsic::x86_sse2_sub_sd:
case Intrinsic::x86_sse2_mul_sd:
case Intrinsic::x86_sse2_min_sd:
case Intrinsic::x86_sse2_max_sd:
TmpV = SimplifyDemandedVectorElts(II->getOperand(1), DemandedElts,
UndefElts, Depth+1);
if (TmpV) { II->setOperand(1, TmpV); MadeChange = true; }
TmpV = SimplifyDemandedVectorElts(II->getOperand(2), DemandedElts,
UndefElts2, Depth+1);
if (TmpV) { II->setOperand(2, TmpV); MadeChange = true; }
// If only the low elt is demanded and this is a scalarizable intrinsic,
// scalarize it now.
if (DemandedElts == 1) {
switch (II->getIntrinsicID()) {
default: break;
case Intrinsic::x86_sse_sub_ss:
case Intrinsic::x86_sse_mul_ss:
case Intrinsic::x86_sse2_sub_sd:
case Intrinsic::x86_sse2_mul_sd:
// TODO: Lower MIN/MAX/ABS/etc
Value *LHS = II->getOperand(1);
Value *RHS = II->getOperand(2);
// Extract the element as scalars.
LHS = InsertNewInstBefore(new ExtractElementInst(LHS, 0U,"tmp"), *II);
RHS = InsertNewInstBefore(new ExtractElementInst(RHS, 0U,"tmp"), *II);
switch (II->getIntrinsicID()) {
default: assert(0 && "Case stmts out of sync!");
case Intrinsic::x86_sse_sub_ss:
case Intrinsic::x86_sse2_sub_sd:
TmpV = InsertNewInstBefore(BinaryOperator::createSub(LHS, RHS,
II->getName()), *II);
break;
case Intrinsic::x86_sse_mul_ss:
case Intrinsic::x86_sse2_mul_sd:
TmpV = InsertNewInstBefore(BinaryOperator::createMul(LHS, RHS,
II->getName()), *II);
break;
}
Instruction *New =
new InsertElementInst(UndefValue::get(II->getType()), TmpV, 0U,
II->getName());
InsertNewInstBefore(New, *II);
AddSoonDeadInstToWorklist(*II, 0);
return New;
}
}
// Output elements are undefined if both are undefined. Consider things
// like undef&0. The result is known zero, not undef.
UndefElts &= UndefElts2;
break;
}
break;
}
}
return MadeChange ? I : 0;
}
// isTrueWhenEqual - Return true if the specified setcondinst instruction is
// true when both operands are equal...
//
static bool isTrueWhenEqual(Instruction &I) {
return I.getOpcode() == Instruction::SetEQ ||
I.getOpcode() == Instruction::SetGE ||
I.getOpcode() == Instruction::SetLE;
}
/// AssociativeOpt - Perform an optimization on an associative operator. This
/// function is designed to check a chain of associative operators for a
/// potential to apply a certain optimization. Since the optimization may be
/// applicable if the expression was reassociated, this checks the chain, then
/// reassociates the expression as necessary to expose the optimization
/// opportunity. This makes use of a special Functor, which must define
/// 'shouldApply' and 'apply' methods.
///
template<typename Functor>
Instruction *AssociativeOpt(BinaryOperator &Root, const Functor &F) {
unsigned Opcode = Root.getOpcode();
Value *LHS = Root.getOperand(0);
// Quick check, see if the immediate LHS matches...
if (F.shouldApply(LHS))
return F.apply(Root);
// Otherwise, if the LHS is not of the same opcode as the root, return.
Instruction *LHSI = dyn_cast<Instruction>(LHS);
while (LHSI && LHSI->getOpcode() == Opcode && LHSI->hasOneUse()) {
// Should we apply this transform to the RHS?
bool ShouldApply = F.shouldApply(LHSI->getOperand(1));
// If not to the RHS, check to see if we should apply to the LHS...
if (!ShouldApply && F.shouldApply(LHSI->getOperand(0))) {
cast<BinaryOperator>(LHSI)->swapOperands(); // Make the LHS the RHS
ShouldApply = true;
}
// If the functor wants to apply the optimization to the RHS of LHSI,
// reassociate the expression from ((? op A) op B) to (? op (A op B))
if (ShouldApply) {
BasicBlock *BB = Root.getParent();
// Now all of the instructions are in the current basic block, go ahead
// and perform the reassociation.
Instruction *TmpLHSI = cast<Instruction>(Root.getOperand(0));
// First move the selected RHS to the LHS of the root...
Root.setOperand(0, LHSI->getOperand(1));
// Make what used to be the LHS of the root be the user of the root...
Value *ExtraOperand = TmpLHSI->getOperand(1);
if (&Root == TmpLHSI) {
Root.replaceAllUsesWith(Constant::getNullValue(TmpLHSI->getType()));
return 0;
}
Root.replaceAllUsesWith(TmpLHSI); // Users now use TmpLHSI
TmpLHSI->setOperand(1, &Root); // TmpLHSI now uses the root
TmpLHSI->getParent()->getInstList().remove(TmpLHSI);
BasicBlock::iterator ARI = &Root; ++ARI;
BB->getInstList().insert(ARI, TmpLHSI); // Move TmpLHSI to after Root
ARI = Root;
// Now propagate the ExtraOperand down the chain of instructions until we
// get to LHSI.
while (TmpLHSI != LHSI) {
Instruction *NextLHSI = cast<Instruction>(TmpLHSI->getOperand(0));
// Move the instruction to immediately before the chain we are
// constructing to avoid breaking dominance properties.
NextLHSI->getParent()->getInstList().remove(NextLHSI);
BB->getInstList().insert(ARI, NextLHSI);
ARI = NextLHSI;
Value *NextOp = NextLHSI->getOperand(1);
NextLHSI->setOperand(1, ExtraOperand);
TmpLHSI = NextLHSI;
ExtraOperand = NextOp;
}
// Now that the instructions are reassociated, have the functor perform
// the transformation...
return F.apply(Root);
}
LHSI = dyn_cast<Instruction>(LHSI->getOperand(0));
}
return 0;
}
// AddRHS - Implements: X + X --> X << 1
struct AddRHS {
Value *RHS;
AddRHS(Value *rhs) : RHS(rhs) {}
bool shouldApply(Value *LHS) const { return LHS == RHS; }
Instruction *apply(BinaryOperator &Add) const {
return new ShiftInst(Instruction::Shl, Add.getOperand(0),
ConstantInt::get(Type::UByteTy, 1));
}
};
// AddMaskingAnd - Implements (A & C1)+(B & C2) --> (A & C1)|(B & C2)
// iff C1&C2 == 0
struct AddMaskingAnd {
Constant *C2;
AddMaskingAnd(Constant *c) : C2(c) {}
bool shouldApply(Value *LHS) const {
ConstantInt *C1;
return match(LHS, m_And(m_Value(), m_ConstantInt(C1))) &&
ConstantExpr::getAnd(C1, C2)->isNullValue();
}
Instruction *apply(BinaryOperator &Add) const {
return BinaryOperator::createOr(Add.getOperand(0), Add.getOperand(1));
}
};
static Value *FoldOperationIntoSelectOperand(Instruction &I, Value *SO,
InstCombiner *IC) {
if (isa<CastInst>(I)) {
if (Constant *SOC = dyn_cast<Constant>(SO))
return ConstantExpr::getCast(SOC, I.getType());
return IC->InsertNewInstBefore(new CastInst(SO, I.getType(),
SO->getName() + ".cast"), I);
}
// Figure out if the constant is the left or the right argument.
bool ConstIsRHS = isa<Constant>(I.getOperand(1));
Constant *ConstOperand = cast<Constant>(I.getOperand(ConstIsRHS));
if (Constant *SOC = dyn_cast<Constant>(SO)) {
if (ConstIsRHS)
return ConstantExpr::get(I.getOpcode(), SOC, ConstOperand);
return ConstantExpr::get(I.getOpcode(), ConstOperand, SOC);
}
Value *Op0 = SO, *Op1 = ConstOperand;
if (!ConstIsRHS)
std::swap(Op0, Op1);
Instruction *New;
if (BinaryOperator *BO = dyn_cast<BinaryOperator>(&I))
New = BinaryOperator::create(BO->getOpcode(), Op0, Op1,SO->getName()+".op");
else if (ShiftInst *SI = dyn_cast<ShiftInst>(&I))
New = new ShiftInst(SI->getOpcode(), Op0, Op1, SO->getName()+".sh");
else {
assert(0 && "Unknown binary instruction type!");
abort();
}
return IC->InsertNewInstBefore(New, I);
}
// FoldOpIntoSelect - Given an instruction with a select as one operand and a
// constant as the other operand, try to fold the binary operator into the
// select arguments. This also works for Cast instructions, which obviously do
// not have a second operand.
static Instruction *FoldOpIntoSelect(Instruction &Op, SelectInst *SI,
InstCombiner *IC) {
// Don't modify shared select instructions
if (!SI->hasOneUse()) return 0;
Value *TV = SI->getOperand(1);
Value *FV = SI->getOperand(2);
if (isa<Constant>(TV) || isa<Constant>(FV)) {
// Bool selects with constant operands can be folded to logical ops.
if (SI->getType() == Type::BoolTy) return 0;
Value *SelectTrueVal = FoldOperationIntoSelectOperand(Op, TV, IC);
Value *SelectFalseVal = FoldOperationIntoSelectOperand(Op, FV, IC);
return new SelectInst(SI->getCondition(), SelectTrueVal,
SelectFalseVal);
}
return 0;
}
/// FoldOpIntoPhi - Given a binary operator or cast instruction which has a PHI
/// node as operand #0, see if we can fold the instruction into the PHI (which
/// is only possible if all operands to the PHI are constants).
Instruction *InstCombiner::FoldOpIntoPhi(Instruction &I) {
PHINode *PN = cast<PHINode>(I.getOperand(0));
unsigned NumPHIValues = PN->getNumIncomingValues();
if (!PN->hasOneUse() || NumPHIValues == 0) return 0;
// Check to see if all of the operands of the PHI are constants. If there is
// one non-constant value, remember the BB it is. If there is more than one
// bail out.
BasicBlock *NonConstBB = 0;
for (unsigned i = 0; i != NumPHIValues; ++i)
if (!isa<Constant>(PN->getIncomingValue(i))) {
if (NonConstBB) return 0; // More than one non-const value.
NonConstBB = PN->getIncomingBlock(i);
// If the incoming non-constant value is in I's block, we have an infinite
// loop.
if (NonConstBB == I.getParent())
return 0;
}
// If there is exactly one non-constant value, we can insert a copy of the
// operation in that block. However, if this is a critical edge, we would be
// inserting the computation one some other paths (e.g. inside a loop). Only
// do this if the pred block is unconditionally branching into the phi block.
if (NonConstBB) {
BranchInst *BI = dyn_cast<BranchInst>(NonConstBB->getTerminator());
if (!BI || !BI->isUnconditional()) return 0;
}
// Okay, we can do the transformation: create the new PHI node.
PHINode *NewPN = new PHINode(I.getType(), I.getName());
I.setName("");
NewPN->reserveOperandSpace(PN->getNumOperands()/2);
InsertNewInstBefore(NewPN, *PN);
// Next, add all of the operands to the PHI.
if (I.getNumOperands() == 2) {
Constant *C = cast<Constant>(I.getOperand(1));
for (unsigned i = 0; i != NumPHIValues; ++i) {
Value *InV;
if (Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i))) {
InV = ConstantExpr::get(I.getOpcode(), InC, C);
} else {
assert(PN->getIncomingBlock(i) == NonConstBB);
if (BinaryOperator *BO = dyn_cast<BinaryOperator>(&I))
InV = BinaryOperator::create(BO->getOpcode(),
PN->getIncomingValue(i), C, "phitmp",
NonConstBB->getTerminator());
else if (ShiftInst *SI = dyn_cast<ShiftInst>(&I))
InV = new ShiftInst(SI->getOpcode(),
PN->getIncomingValue(i), C, "phitmp",
NonConstBB->getTerminator());
else
assert(0 && "Unknown binop!");
WorkList.push_back(cast<Instruction>(InV));
}
NewPN->addIncoming(InV, PN->getIncomingBlock(i));
}
} else {
assert(isa<CastInst>(I) && "Unary op should be a cast!");
const Type *RetTy = I.getType();
for (unsigned i = 0; i != NumPHIValues; ++i) {
Value *InV;
if (Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i))) {
InV = ConstantExpr::getCast(InC, RetTy);
} else {
assert(PN->getIncomingBlock(i) == NonConstBB);
InV = new CastInst(PN->getIncomingValue(i), I.getType(), "phitmp",
NonConstBB->getTerminator());
WorkList.push_back(cast<Instruction>(InV));
}
NewPN->addIncoming(InV, PN->getIncomingBlock(i));
}
}
return ReplaceInstUsesWith(I, NewPN);
}
Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
bool Changed = SimplifyCommutative(I);
Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
if (Constant *RHSC = dyn_cast<Constant>(RHS)) {
// X + undef -> undef
if (isa<UndefValue>(RHS))
return ReplaceInstUsesWith(I, RHS);
// X + 0 --> X
if (!I.getType()->isFloatingPoint()) { // NOTE: -0 + +0 = +0.
if (RHSC->isNullValue())
return ReplaceInstUsesWith(I, LHS);
} else if (ConstantFP *CFP = dyn_cast<ConstantFP>(RHSC)) {
if (CFP->isExactlyValue(-0.0))
return ReplaceInstUsesWith(I, LHS);
}
// X + (signbit) --> X ^ signbit
if (ConstantInt *CI = dyn_cast<ConstantInt>(RHSC)) {
uint64_t Val = CI->getZExtValue();
if (Val == (1ULL << (CI->getType()->getPrimitiveSizeInBits()-1)))
return BinaryOperator::createXor(LHS, RHS);
}
if (isa<PHINode>(LHS))
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
ConstantInt *XorRHS = 0;
Value *XorLHS = 0;
if (match(LHS, m_Xor(m_Value(XorLHS), m_ConstantInt(XorRHS)))) {
unsigned TySizeBits = I.getType()->getPrimitiveSizeInBits();
int64_t RHSSExt = cast<ConstantInt>(RHSC)->getSExtValue();
uint64_t RHSZExt = cast<ConstantInt>(RHSC)->getZExtValue();
uint64_t C0080Val = 1ULL << 31;
int64_t CFF80Val = -C0080Val;
unsigned Size = 32;
do {
if (TySizeBits > Size) {
bool Found = false;
// If we have ADD(XOR(AND(X, 0xFF), 0x80), 0xF..F80), it's a sext.
// If we have ADD(XOR(AND(X, 0xFF), 0xF..F80), 0x80), it's a sext.
if (RHSSExt == CFF80Val) {
if (XorRHS->getZExtValue() == C0080Val)
Found = true;
} else if (RHSZExt == C0080Val) {
if (XorRHS->getSExtValue() == CFF80Val)
Found = true;
}
if (Found) {
// This is a sign extend if the top bits are known zero.
uint64_t Mask = ~0ULL;
Mask <<= 64-(TySizeBits-Size);
Mask &= XorLHS->getType()->getIntegralTypeMask();
if (!MaskedValueIsZero(XorLHS, Mask))
Size = 0; // Not a sign ext, but can't be any others either.
goto FoundSExt;
}
}
Size >>= 1;
C0080Val >>= Size;
CFF80Val >>= Size;
} while (Size >= 8);
FoundSExt:
const Type *MiddleType = 0;
switch (Size) {
default: break;
case 32: MiddleType = Type::IntTy; break;
case 16: MiddleType = Type::ShortTy; break;
case 8: MiddleType = Type::SByteTy; break;
}
if (MiddleType) {
Instruction *NewTrunc = new CastInst(XorLHS, MiddleType, "sext");
InsertNewInstBefore(NewTrunc, I);
return new CastInst(NewTrunc, I.getType());
}
}
}
// X + X --> X << 1
if (I.getType()->isInteger()) {
if (Instruction *Result = AssociativeOpt(I, AddRHS(RHS))) return Result;
if (Instruction *RHSI = dyn_cast<Instruction>(RHS)) {
if (RHSI->getOpcode() == Instruction::Sub)
if (LHS == RHSI->getOperand(1)) // A + (B - A) --> B
return ReplaceInstUsesWith(I, RHSI->getOperand(0));
}
if (Instruction *LHSI = dyn_cast<Instruction>(LHS)) {
if (LHSI->getOpcode() == Instruction::Sub)
if (RHS == LHSI->getOperand(1)) // (B - A) + A --> B
return ReplaceInstUsesWith(I, LHSI->getOperand(0));
}
}
// -A + B --> B - A
if (Value *V = dyn_castNegVal(LHS))
return BinaryOperator::createSub(RHS, V);
// A + -B --> A - B
if (!isa<Constant>(RHS))
if (Value *V = dyn_castNegVal(RHS))
return BinaryOperator::createSub(LHS, V);
ConstantInt *C2;
if (Value *X = dyn_castFoldableMul(LHS, C2)) {
if (X == RHS) // X*C + X --> X * (C+1)
return BinaryOperator::createMul(RHS, AddOne(C2));
// X*C1 + X*C2 --> X * (C1+C2)
ConstantInt *C1;
if (X == dyn_castFoldableMul(RHS, C1))
return BinaryOperator::createMul(X, ConstantExpr::getAdd(C1, C2));
}
// X + X*C --> X * (C+1)
if (dyn_castFoldableMul(RHS, C2) == LHS)
return BinaryOperator::createMul(LHS, AddOne(C2));
// (A & C1)+(B & C2) --> (A & C1)|(B & C2) iff C1&C2 == 0
if (match(RHS, m_And(m_Value(), m_ConstantInt(C2))))
if (Instruction *R = AssociativeOpt(I, AddMaskingAnd(C2))) return R;
if (ConstantInt *CRHS = dyn_cast<ConstantInt>(RHS)) {
Value *X = 0;
if (match(LHS, m_Not(m_Value(X)))) { // ~X + C --> (C-1) - X
Constant *C= ConstantExpr::getSub(CRHS, ConstantInt::get(I.getType(), 1));
return BinaryOperator::createSub(C, X);
}
// (X & FF00) + xx00 -> (X+xx00) & FF00
if (LHS->hasOneUse() && match(LHS, m_And(m_Value(X), m_ConstantInt(C2)))) {
Constant *Anded = ConstantExpr::getAnd(CRHS, C2);
if (Anded == CRHS) {
// See if all bits from the first bit set in the Add RHS up are included
// in the mask. First, get the rightmost bit.
uint64_t AddRHSV = CRHS->getZExtValue();
// Form a mask of all bits from the lowest bit added through the top.
uint64_t AddRHSHighBits = ~((AddRHSV & -AddRHSV)-1);
AddRHSHighBits &= C2->getType()->getIntegralTypeMask();
// See if the and mask includes all of these bits.
uint64_t AddRHSHighBitsAnd = AddRHSHighBits & C2->getZExtValue();
if (AddRHSHighBits == AddRHSHighBitsAnd) {
// Okay, the xform is safe. Insert the new add pronto.
Value *NewAdd = InsertNewInstBefore(BinaryOperator::createAdd(X, CRHS,
LHS->getName()), I);
return BinaryOperator::createAnd(NewAdd, C2);
}
}
}
// Try to fold constant add into select arguments.
if (SelectInst *SI = dyn_cast<SelectInst>(LHS))
if (Instruction *R = FoldOpIntoSelect(I, SI, this))
return R;
}
// add (cast *A to intptrtype) B ->
// cast (GEP (cast *A to sbyte*) B) ->
// intptrtype
{
CastInst* CI = dyn_cast<CastInst>(LHS);
Value* Other = RHS;
if (!CI) {
CI = dyn_cast<CastInst>(RHS);
Other = LHS;
}
if (CI && CI->getType()->isSized() &&
(CI->getType()->getPrimitiveSize() ==
TD->getIntPtrType()->getPrimitiveSize())
&& isa<PointerType>(CI->getOperand(0)->getType())) {
Value* I2 = InsertCastBefore(CI->getOperand(0),
PointerType::get(Type::SByteTy), I);
I2 = InsertNewInstBefore(new GetElementPtrInst(I2, Other, "ctg2"), I);
return new CastInst(I2, CI->getType());
}
}
return Changed ? &I : 0;
}
// isSignBit - Return true if the value represented by the constant only has the
// highest order bit set.
static bool isSignBit(ConstantInt *CI) {
unsigned NumBits = CI->getType()->getPrimitiveSizeInBits();
return (CI->getZExtValue() & (~0ULL >> (64-NumBits))) == (1ULL << (NumBits-1));
}
/// RemoveNoopCast - Strip off nonconverting casts from the value.
///
static Value *RemoveNoopCast(Value *V) {
if (CastInst *CI = dyn_cast<CastInst>(V)) {
const Type *CTy = CI->getType();
const Type *OpTy = CI->getOperand(0)->getType();
if (CTy->isInteger() && OpTy->isInteger()) {
if (CTy->getPrimitiveSizeInBits() == OpTy->getPrimitiveSizeInBits())
return RemoveNoopCast(CI->getOperand(0));
} else if (isa<PointerType>(CTy) && isa<PointerType>(OpTy))
return RemoveNoopCast(CI->getOperand(0));
}
return V;
}
Instruction *InstCombiner::visitSub(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
if (Op0 == Op1) // sub X, X -> 0
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
// If this is a 'B = x-(-A)', change to B = x+A...
if (Value *V = dyn_castNegVal(Op1))
return BinaryOperator::createAdd(Op0, V);
if (isa<UndefValue>(Op0))
return ReplaceInstUsesWith(I, Op0); // undef - X -> undef
if (isa<UndefValue>(Op1))
return ReplaceInstUsesWith(I, Op1); // X - undef -> undef
if (ConstantInt *C = dyn_cast<ConstantInt>(Op0)) {
// Replace (-1 - A) with (~A)...
if (C->isAllOnesValue())
return BinaryOperator::createNot(Op1);
// C - ~X == X + (1+C)
Value *X = 0;
if (match(Op1, m_Not(m_Value(X))))
return BinaryOperator::createAdd(X,
ConstantExpr::getAdd(C, ConstantInt::get(I.getType(), 1)));
// -((uint)X >> 31) -> ((int)X >> 31)
// -((int)X >> 31) -> ((uint)X >> 31)
if (C->isNullValue()) {
Value *NoopCastedRHS = RemoveNoopCast(Op1);
if (ShiftInst *SI = dyn_cast<ShiftInst>(NoopCastedRHS))
if (SI->getOpcode() == Instruction::LShr) {
if (ConstantInt *CU = dyn_cast<ConstantInt>(SI->getOperand(1))) {
// Check to see if we are shifting out everything but the sign bit.
if (CU->getZExtValue() ==
SI->getType()->getPrimitiveSizeInBits()-1) {
// Ok, the transformation is safe. Insert AShr.
return new ShiftInst(Instruction::AShr, SI->getOperand(0),
CU, SI->getName());
}
}
}
else if (SI->getOpcode() == Instruction::AShr) {
if (ConstantInt *CU = dyn_cast<ConstantInt>(SI->getOperand(1))) {
// Check to see if we are shifting out everything but the sign bit.
if (CU->getZExtValue() ==
SI->getType()->getPrimitiveSizeInBits()-1) {
// Ok, the transformation is safe. Insert LShr.
return new ShiftInst(Instruction::LShr, SI->getOperand(0),
CU, SI->getName());
}
}
}
}
// Try to fold constant sub into select arguments.
if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
if (Instruction *R = FoldOpIntoSelect(I, SI, this))
return R;
if (isa<PHINode>(Op0))
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
}
if (BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1)) {
if (Op1I->getOpcode() == Instruction::Add &&
!Op0->getType()->isFloatingPoint()) {
if (Op1I->getOperand(0) == Op0) // X-(X+Y) == -Y
return BinaryOperator::createNeg(Op1I->getOperand(1), I.getName());
else if (Op1I->getOperand(1) == Op0) // X-(Y+X) == -Y
return BinaryOperator::createNeg(Op1I->getOperand(0), I.getName());
else if (ConstantInt *CI1 = dyn_cast<ConstantInt>(I.getOperand(0))) {
if (ConstantInt *CI2 = dyn_cast<ConstantInt>(Op1I->getOperand(1)))
// C1-(X+C2) --> (C1-C2)-X
return BinaryOperator::createSub(ConstantExpr::getSub(CI1, CI2),
Op1I->getOperand(0));
}
}
if (Op1I->hasOneUse()) {
// Replace (x - (y - z)) with (x + (z - y)) if the (y - z) subexpression
// is not used by anyone else...
//
if (Op1I->getOpcode() == Instruction::Sub &&
!Op1I->getType()->isFloatingPoint()) {
// Swap the two operands of the subexpr...
Value *IIOp0 = Op1I->getOperand(0), *IIOp1 = Op1I->getOperand(1);
Op1I->setOperand(0, IIOp1);
Op1I->setOperand(1, IIOp0);
// Create the new top level add instruction...
return BinaryOperator::createAdd(Op0, Op1);
}
// Replace (A - (A & B)) with (A & ~B) if this is the only use of (A&B)...
//
if (Op1I->getOpcode() == Instruction::And &&
(Op1I->getOperand(0) == Op0 || Op1I->getOperand(1) == Op0)) {
Value *OtherOp = Op1I->getOperand(Op1I->getOperand(0) == Op0);
Value *NewNot =
InsertNewInstBefore(BinaryOperator::createNot(OtherOp, "B.not"), I);
return BinaryOperator::createAnd(Op0, NewNot);
}
// 0 - (X sdiv C) -> (X sdiv -C)
if (Op1I->getOpcode() == Instruction::SDiv)
if (ConstantInt *CSI = dyn_cast<ConstantInt>(Op0))
if (CSI->isNullValue())
if (Constant *DivRHS = dyn_cast<Constant>(Op1I->getOperand(1)))
return BinaryOperator::createSDiv(Op1I->getOperand(0),
ConstantExpr::getNeg(DivRHS));
// X - X*C --> X * (1-C)
ConstantInt *C2 = 0;
if (dyn_castFoldableMul(Op1I, C2) == Op0) {
Constant *CP1 =
ConstantExpr::getSub(ConstantInt::get(I.getType(), 1), C2);
return BinaryOperator::createMul(Op0, CP1);
}
}
}
if (!Op0->getType()->isFloatingPoint())
if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0))
if (Op0I->getOpcode() == Instruction::Add) {
if (Op0I->getOperand(0) == Op1) // (Y+X)-Y == X
return ReplaceInstUsesWith(I, Op0I->getOperand(1));
else if (Op0I->getOperand(1) == Op1) // (X+Y)-Y == X
return ReplaceInstUsesWith(I, Op0I->getOperand(0));
} else if (Op0I->getOpcode() == Instruction::Sub) {
if (Op0I->getOperand(0) == Op1) // (X-Y)-X == -Y
return BinaryOperator::createNeg(Op0I->getOperand(1), I.getName());
}
ConstantInt *C1;
if (Value *X = dyn_castFoldableMul(Op0, C1)) {
if (X == Op1) { // X*C - X --> X * (C-1)
Constant *CP1 = ConstantExpr::getSub(C1, ConstantInt::get(I.getType(),1));
return BinaryOperator::createMul(Op1, CP1);
}
ConstantInt *C2; // X*C1 - X*C2 -> X * (C1-C2)
if (X == dyn_castFoldableMul(Op1, C2))
return BinaryOperator::createMul(Op1, ConstantExpr::getSub(C1, C2));
}
return 0;
}
/// isSignBitCheck - Given an exploded setcc instruction, return true if it is
/// really just returns true if the most significant (sign) bit is set.
static bool isSignBitCheck(unsigned Opcode, Value *LHS, ConstantInt *RHS) {
if (RHS->getType()->isSigned()) {
// True if source is LHS < 0 or LHS <= -1
return Opcode == Instruction::SetLT && RHS->isNullValue() ||
Opcode == Instruction::SetLE && RHS->isAllOnesValue();
} else {
ConstantInt *RHSC = cast<ConstantInt>(RHS);
// True if source is LHS > 127 or LHS >= 128, where the constants depend on
// the size of the integer type.
if (Opcode == Instruction::SetGE)
return RHSC->getZExtValue() ==
1ULL << (RHS->getType()->getPrimitiveSizeInBits()-1);
if (Opcode == Instruction::SetGT)
return RHSC->getZExtValue() ==
(1ULL << (RHS->getType()->getPrimitiveSizeInBits()-1))-1;
}
return false;
}
Instruction *InstCombiner::visitMul(BinaryOperator &I) {
bool Changed = SimplifyCommutative(I);
Value *Op0 = I.getOperand(0);
if (isa<UndefValue>(I.getOperand(1))) // undef * X -> 0
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
// Simplify mul instructions with a constant RHS...
if (Constant *Op1 = dyn_cast<Constant>(I.getOperand(1))) {
if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
// ((X << C1)*C2) == (X * (C2 << C1))
if (ShiftInst *SI = dyn_cast<ShiftInst>(Op0))
if (SI->getOpcode() == Instruction::Shl)
if (Constant *ShOp = dyn_cast<Constant>(SI->getOperand(1)))
return BinaryOperator::createMul(SI->getOperand(0),
ConstantExpr::getShl(CI, ShOp));
if (CI->isNullValue())
return ReplaceInstUsesWith(I, Op1); // X * 0 == 0
if (CI->equalsInt(1)) // X * 1 == X
return ReplaceInstUsesWith(I, Op0);
if (CI->isAllOnesValue()) // X * -1 == 0 - X
return BinaryOperator::createNeg(Op0, I.getName());
int64_t Val = (int64_t)cast<ConstantInt>(CI)->getZExtValue();
if (isPowerOf2_64(Val)) { // Replace X*(2^C) with X << C
uint64_t C = Log2_64(Val);
return new ShiftInst(Instruction::Shl, Op0,
ConstantInt::get(Type::UByteTy, C));
}
} else if (ConstantFP *Op1F = dyn_cast<ConstantFP>(Op1)) {
if (Op1F->isNullValue())
return ReplaceInstUsesWith(I, Op1);
// "In IEEE floating point, x*1 is not equivalent to x for nans. However,
// ANSI says we can drop signals, so we can do this anyway." (from GCC)
if (Op1F->getValue() == 1.0)
return ReplaceInstUsesWith(I, Op0); // Eliminate 'mul double %X, 1.0'
}
if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0))
if (Op0I->getOpcode() == Instruction::Add && Op0I->hasOneUse() &&
isa<ConstantInt>(Op0I->getOperand(1))) {
// Canonicalize (X+C1)*C2 -> X*C2+C1*C2.
Instruction *Add = BinaryOperator::createMul(Op0I->getOperand(0),
Op1, "tmp");
InsertNewInstBefore(Add, I);
Value *C1C2 = ConstantExpr::getMul(Op1,
cast<Constant>(Op0I->getOperand(1)));
return BinaryOperator::createAdd(Add, C1C2);
}
// Try to fold constant mul into select arguments.
if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
if (Instruction *R = FoldOpIntoSelect(I, SI, this))
return R;
if (isa<PHINode>(Op0))
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
}
if (Value *Op0v = dyn_castNegVal(Op0)) // -X * -Y = X*Y
if (Value *Op1v = dyn_castNegVal(I.getOperand(1)))
return BinaryOperator::createMul(Op0v, Op1v);
// If one of the operands of the multiply is a cast from a boolean value, then
// we know the bool is either zero or one, so this is a 'masking' multiply.
// See if we can simplify things based on how the boolean was originally
// formed.
CastInst *BoolCast = 0;
if (CastInst *CI = dyn_cast<CastInst>(I.getOperand(0)))
if (CI->getOperand(0)->getType() == Type::BoolTy)
BoolCast = CI;
if (!BoolCast)
if (CastInst *CI = dyn_cast<CastInst>(I.getOperand(1)))
if (CI->getOperand(0)->getType() == Type::BoolTy)
BoolCast = CI;
if (BoolCast) {
if (SetCondInst *SCI = dyn_cast<SetCondInst>(BoolCast->getOperand(0))) {
Value *SCIOp0 = SCI->getOperand(0), *SCIOp1 = SCI->getOperand(1);
const Type *SCOpTy = SCIOp0->getType();
// If the setcc is true iff the sign bit of X is set, then convert this
// multiply into a shift/and combination.
if (isa<ConstantInt>(SCIOp1) &&
isSignBitCheck(SCI->getOpcode(), SCIOp0, cast<ConstantInt>(SCIOp1))) {
// Shift the X value right to turn it into "all signbits".
Constant *Amt = ConstantInt::get(Type::UByteTy,
SCOpTy->getPrimitiveSizeInBits()-1);
if (SCIOp0->getType()->isUnsigned()) {
const Type *NewTy = SCIOp0->getType()->getSignedVersion();
SCIOp0 = InsertCastBefore(SCIOp0, NewTy, I);
}
Value *V =
InsertNewInstBefore(new ShiftInst(Instruction::AShr, SCIOp0, Amt,
BoolCast->getOperand(0)->getName()+
".mask"), I);
// If the multiply type is not the same as the source type, sign extend
// or truncate to the multiply type.
if (I.getType() != V->getType())
V = InsertCastBefore(V, I.getType(), I);
Value *OtherOp = Op0 == BoolCast ? I.getOperand(1) : Op0;
return BinaryOperator::createAnd(V, OtherOp);
}
}
}
return Changed ? &I : 0;
}
/// This function implements the transforms on div instructions that work
/// regardless of the kind of div instruction it is (udiv, sdiv, or fdiv). It is
/// used by the visitors to those instructions.
/// @brief Transforms common to all three div instructions
Instruction* InstCombiner::commonDivTransforms(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
// undef / X -> 0
if (isa<UndefValue>(Op0))
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
// X / undef -> undef
if (isa<UndefValue>(Op1))
return ReplaceInstUsesWith(I, Op1);
// Handle cases involving: div X, (select Cond, Y, Z)
if (SelectInst *SI = dyn_cast<SelectInst>(Op1)) {
// div X, (Cond ? 0 : Y) -> div X, Y. If the div and the select are in the
// same basic block, then we replace the select with Y, and the condition
// of the select with false (if the cond value is in the same BB). If the
// select has uses other than the div, this allows them to be simplified
// also. Note that div X, Y is just as good as div X, 0 (undef)
if (Constant *ST = dyn_cast<Constant>(SI->getOperand(1)))
if (ST->isNullValue()) {
Instruction *CondI = dyn_cast<Instruction>(SI->getOperand(0));
if (CondI && CondI->getParent() == I.getParent())
UpdateValueUsesWith(CondI, ConstantBool::getFalse());
else if (I.getParent() != SI->getParent() || SI->hasOneUse())
I.setOperand(1, SI->getOperand(2));
else
UpdateValueUsesWith(SI, SI->getOperand(2));
return &I;
}
// Likewise for: div X, (Cond ? Y : 0) -> div X, Y
if (Constant *ST = dyn_cast<Constant>(SI->getOperand(2)))
if (ST->isNullValue()) {
Instruction *CondI = dyn_cast<Instruction>(SI->getOperand(0));
if (CondI && CondI->getParent() == I.getParent())
UpdateValueUsesWith(CondI, ConstantBool::getTrue());
else if (I.getParent() != SI->getParent() || SI->hasOneUse())
I.setOperand(1, SI->getOperand(1));
else
UpdateValueUsesWith(SI, SI->getOperand(1));
return &I;
}
}
return 0;
}
/// This function implements the transforms common to both integer division
/// instructions (udiv and sdiv). It is called by the visitors to those integer
/// division instructions.
/// @brief Common integer divide transforms
Instruction* InstCombiner::commonIDivTransforms(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
if (Instruction *Common = commonDivTransforms(I))
return Common;
if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) {
// div X, 1 == X
if (RHS->equalsInt(1))
return ReplaceInstUsesWith(I, Op0);
// (X / C1) / C2 -> X / (C1*C2)
if (Instruction *LHS = dyn_cast<Instruction>(Op0))
if (Instruction::BinaryOps(LHS->getOpcode()) == I.getOpcode())
if (ConstantInt *LHSRHS = dyn_cast<ConstantInt>(LHS->getOperand(1))) {
return BinaryOperator::create(I.getOpcode(), LHS->getOperand(0),
ConstantExpr::getMul(RHS, LHSRHS));
}
if (!RHS->isNullValue()) { // avoid X udiv 0
if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
if (Instruction *R = FoldOpIntoSelect(I, SI, this))
return R;
if (isa<PHINode>(Op0))
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
}
}
// 0 / X == 0, we don't need to preserve faults!
if (ConstantInt *LHS = dyn_cast<ConstantInt>(Op0))
if (LHS->equalsInt(0))
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
return 0;
}
Instruction *InstCombiner::visitUDiv(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
// Handle the integer div common cases
if (Instruction *Common = commonIDivTransforms(I))
return Common;
// X udiv C^2 -> X >> C
// Check to see if this is an unsigned division with an exact power of 2,
// if so, convert to a right shift.
if (ConstantInt *C = dyn_cast<ConstantInt>(Op1)) {
if (uint64_t Val = C->getZExtValue()) // Don't break X / 0
if (isPowerOf2_64(Val)) {
uint64_t ShiftAmt = Log2_64(Val);
return new ShiftInst(Instruction::LShr, Op0,
ConstantInt::get(Type::UByteTy, ShiftAmt));
}
}
// X udiv (C1 << N), where C1 is "1<<C2" --> X >> (N+C2)
if (ShiftInst *RHSI = dyn_cast<ShiftInst>(I.getOperand(1))) {
if (RHSI->getOpcode() == Instruction::Shl &&
isa<ConstantInt>(RHSI->getOperand(0))) {
uint64_t C1 = cast<ConstantInt>(RHSI->getOperand(0))->getZExtValue();
if (isPowerOf2_64(C1)) {
Value *N = RHSI->getOperand(1);
const Type* NTy = N->getType();
if (uint64_t C2 = Log2_64(C1)) {
Constant *C2V = ConstantInt::get(NTy, C2);
N = InsertNewInstBefore(BinaryOperator::createAdd(N, C2V, "tmp"), I);
}
return new ShiftInst(Instruction::LShr, Op0, N);
}
}
}
// udiv X, (Select Cond, C1, C2) --> Select Cond, (shr X, C1), (shr X, C2)
// where C1&C2 are powers of two.
if (SelectInst *SI = dyn_cast<SelectInst>(Op1)) {
if (ConstantInt *STO = dyn_cast<ConstantInt>(SI->getOperand(1)))
if (ConstantInt *SFO = dyn_cast<ConstantInt>(SI->getOperand(2)))
if (!STO->isNullValue() && !STO->isNullValue()) {
uint64_t TVA = STO->getZExtValue(), FVA = SFO->getZExtValue();
if (isPowerOf2_64(TVA) && isPowerOf2_64(FVA)) {
// Compute the shift amounts
unsigned TSA = Log2_64(TVA), FSA = Log2_64(FVA);
// Construct the "on true" case of the select
Constant *TC = ConstantInt::get(Type::UByteTy, TSA);
Instruction *TSI =
new ShiftInst(Instruction::LShr, Op0, TC, SI->getName()+".t");
TSI = InsertNewInstBefore(TSI, I);
// Construct the "on false" case of the select
Constant *FC = ConstantInt::get(Type::UByteTy, FSA);
Instruction *FSI =
new ShiftInst(Instruction::LShr, Op0, FC, SI->getName()+".f");
FSI = InsertNewInstBefore(FSI, I);
// construct the select instruction and return it.
return new SelectInst(SI->getOperand(0), TSI, FSI, SI->getName());
}
}
}
return 0;
}
Instruction *InstCombiner::visitSDiv(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
// Handle the integer div common cases
if (Instruction *Common = commonIDivTransforms(I))
return Common;
if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) {
// sdiv X, -1 == -X
if (RHS->isAllOnesValue())
return BinaryOperator::createNeg(Op0);
// -X/C -> X/-C
if (Value *LHSNeg = dyn_castNegVal(Op0))
return BinaryOperator::createSDiv(LHSNeg, ConstantExpr::getNeg(RHS));
}
// If the sign bits of both operands are zero (i.e. we can prove they are
// unsigned inputs), turn this into a udiv.
if (I.getType()->isInteger()) {
uint64_t Mask = 1ULL << (I.getType()->getPrimitiveSizeInBits()-1);
if (MaskedValueIsZero(Op1, Mask) && MaskedValueIsZero(Op0, Mask)) {
return BinaryOperator::createUDiv(Op0, Op1, I.getName());
}
}
return 0;
}
Instruction *InstCombiner::visitFDiv(BinaryOperator &I) {
return commonDivTransforms(I);
}
/// GetFactor - If we can prove that the specified value is at least a multiple
/// of some factor, return that factor.
static Constant *GetFactor(Value *V) {
if (ConstantInt *CI = dyn_cast<ConstantInt>(V))
return CI;
// Unless we can be tricky, we know this is a multiple of 1.
Constant *Result = ConstantInt::get(V->getType(), 1);
Instruction *I = dyn_cast<Instruction>(V);
if (!I) return Result;
if (I->getOpcode() == Instruction::Mul) {
// Handle multiplies by a constant, etc.
return ConstantExpr::getMul(GetFactor(I->getOperand(0)),
GetFactor(I->getOperand(1)));
} else if (I->getOpcode() == Instruction::Shl) {
// (X<<C) -> X * (1 << C)
if (Constant *ShRHS = dyn_cast<Constant>(I->getOperand(1))) {
ShRHS = ConstantExpr::getShl(Result, ShRHS);
return ConstantExpr::getMul(GetFactor(I->getOperand(0)), ShRHS);
}
} else if (I->getOpcode() == Instruction::And) {
if (ConstantInt *RHS = dyn_cast<ConstantInt>(I->getOperand(1))) {
// X & 0xFFF0 is known to be a multiple of 16.
unsigned Zeros = CountTrailingZeros_64(RHS->getZExtValue());
if (Zeros != V->getType()->getPrimitiveSizeInBits())
return ConstantExpr::getShl(Result,
ConstantInt::get(Type::UByteTy, Zeros));
}
} else if (I->getOpcode() == Instruction::Cast) {
Value *Op = I->getOperand(0);
// Only handle int->int casts.
if (!Op->getType()->isInteger()) return Result;
return ConstantExpr::getCast(GetFactor(Op), V->getType());
}
return Result;
}
/// This function implements the transforms on rem instructions that work
/// regardless of the kind of rem instruction it is (urem, srem, or frem). It
/// is used by the visitors to those instructions.
/// @brief Transforms common to all three rem instructions
Instruction *InstCombiner::commonRemTransforms(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
// 0 % X == 0, we don't need to preserve faults!
if (Constant *LHS = dyn_cast<Constant>(Op0))
if (LHS->isNullValue())
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
if (isa<UndefValue>(Op0)) // undef % X -> 0
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
if (isa<UndefValue>(Op1))
return ReplaceInstUsesWith(I, Op1); // X % undef -> undef
// Handle cases involving: rem X, (select Cond, Y, Z)
if (SelectInst *SI = dyn_cast<SelectInst>(Op1)) {
// rem X, (Cond ? 0 : Y) -> rem X, Y. If the rem and the select are in
// the same basic block, then we replace the select with Y, and the
// condition of the select with false (if the cond value is in the same
// BB). If the select has uses other than the div, this allows them to be
// simplified also.
if (Constant *ST = dyn_cast<Constant>(SI->getOperand(1)))
if (ST->isNullValue()) {
Instruction *CondI = dyn_cast<Instruction>(SI->getOperand(0));
if (CondI && CondI->getParent() == I.getParent())
UpdateValueUsesWith(CondI, ConstantBool::getFalse());
else if (I.getParent() != SI->getParent() || SI->hasOneUse())
I.setOperand(1, SI->getOperand(2));
else
UpdateValueUsesWith(SI, SI->getOperand(2));
return &I;
}
// Likewise for: rem X, (Cond ? Y : 0) -> rem X, Y
if (Constant *ST = dyn_cast<Constant>(SI->getOperand(2)))
if (ST->isNullValue()) {
Instruction *CondI = dyn_cast<Instruction>(SI->getOperand(0));
if (CondI && CondI->getParent() == I.getParent())
UpdateValueUsesWith(CondI, ConstantBool::getTrue());
else if (I.getParent() != SI->getParent() || SI->hasOneUse())
I.setOperand(1, SI->getOperand(1));
else
UpdateValueUsesWith(SI, SI->getOperand(1));
return &I;
}
}
return 0;
}
/// This function implements the transforms common to both integer remainder
/// instructions (urem and srem). It is called by the visitors to those integer
/// remainder instructions.
/// @brief Common integer remainder transforms
Instruction *InstCombiner::commonIRemTransforms(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
if (Instruction *common = commonRemTransforms(I))
return common;
if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) {
// X % 0 == undef, we don't need to preserve faults!
if (RHS->equalsInt(0))
return ReplaceInstUsesWith(I, UndefValue::get(I.getType()));
if (RHS->equalsInt(1)) // X % 1 == 0
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
if (Instruction *Op0I = dyn_cast<Instruction>(Op0)) {
if (SelectInst *SI = dyn_cast<SelectInst>(Op0I)) {
if (Instruction *R = FoldOpIntoSelect(I, SI, this))
return R;
} else if (isa<PHINode>(Op0I)) {
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
}
// (X * C1) % C2 --> 0 iff C1 % C2 == 0
if (ConstantExpr::getSRem(GetFactor(Op0I), RHS)->isNullValue())
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
}
}
return 0;
}
Instruction *InstCombiner::visitURem(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
if (Instruction *common = commonIRemTransforms(I))
return common;
if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) {
// X urem C^2 -> X and C
// Check to see if this is an unsigned remainder with an exact power of 2,
// if so, convert to a bitwise and.
if (ConstantInt *C = dyn_cast<ConstantInt>(RHS))
if (isPowerOf2_64(C->getZExtValue()))
return BinaryOperator::createAnd(Op0, SubOne(C));
}
if (Instruction *RHSI = dyn_cast<Instruction>(I.getOperand(1))) {
// Turn A % (C << N), where C is 2^k, into A & ((C << N)-1)
if (RHSI->getOpcode() == Instruction::Shl &&
isa<ConstantInt>(RHSI->getOperand(0))) {
unsigned C1 = cast<ConstantInt>(RHSI->getOperand(0))->getZExtValue();
if (isPowerOf2_64(C1)) {
Constant *N1 = ConstantInt::getAllOnesValue(I.getType());
Value *Add = InsertNewInstBefore(BinaryOperator::createAdd(RHSI, N1,
"tmp"), I);
return BinaryOperator::createAnd(Op0, Add);
}
}
}
// urem X, (select Cond, 2^C1, 2^C2) --> select Cond, (and X, C1), (and X, C2)
// where C1&C2 are powers of two.
if (SelectInst *SI = dyn_cast<SelectInst>(Op1)) {
if (ConstantInt *STO = dyn_cast<ConstantInt>(SI->getOperand(1)))
if (ConstantInt *SFO = dyn_cast<ConstantInt>(SI->getOperand(2))) {
// STO == 0 and SFO == 0 handled above.
if (isPowerOf2_64(STO->getZExtValue()) &&
isPowerOf2_64(SFO->getZExtValue())) {
Value *TrueAnd = InsertNewInstBefore(
BinaryOperator::createAnd(Op0, SubOne(STO), SI->getName()+".t"), I);
Value *FalseAnd = InsertNewInstBefore(
BinaryOperator::createAnd(Op0, SubOne(SFO), SI->getName()+".f"), I);
return new SelectInst(SI->getOperand(0), TrueAnd, FalseAnd);
}
}
}
return 0;
}
Instruction *InstCombiner::visitSRem(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
if (Instruction *common = commonIRemTransforms(I))
return common;
if (Value *RHSNeg = dyn_castNegVal(Op1))
if (!isa<ConstantInt>(RHSNeg) ||
cast<ConstantInt>(RHSNeg)->getSExtValue() > 0) {
// X % -Y -> X % Y
AddUsesToWorkList(I);
I.setOperand(1, RHSNeg);
return &I;
}
// If the top bits of both operands are zero (i.e. we can prove they are
// unsigned inputs), turn this into a urem.
uint64_t Mask = 1ULL << (I.getType()->getPrimitiveSizeInBits()-1);
if (MaskedValueIsZero(Op1, Mask) && MaskedValueIsZero(Op0, Mask)) {
// X srem Y -> X urem Y, iff X and Y don't have sign bit set
return BinaryOperator::createURem(Op0, Op1, I.getName());
}
return 0;
}
Instruction *InstCombiner::visitFRem(BinaryOperator &I) {
return commonRemTransforms(I);
}
// isMaxValueMinusOne - return true if this is Max-1
static bool isMaxValueMinusOne(const ConstantInt *C) {
if (C->getType()->isUnsigned())
return C->getZExtValue() == C->getType()->getIntegralTypeMask()-1;
// Calculate 0111111111..11111
unsigned TypeBits = C->getType()->getPrimitiveSizeInBits();
int64_t Val = INT64_MAX; // All ones
Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
return C->getSExtValue() == Val-1;
}
// isMinValuePlusOne - return true if this is Min+1
static bool isMinValuePlusOne(const ConstantInt *C) {
if (C->getType()->isUnsigned())
return C->getZExtValue() == 1;
// Calculate 1111111111000000000000
unsigned TypeBits = C->getType()->getPrimitiveSizeInBits();
int64_t Val = -1; // All ones
Val <<= TypeBits-1; // Shift over to the right spot
return C->getSExtValue() == Val+1;
}
// isOneBitSet - Return true if there is exactly one bit set in the specified
// constant.
static bool isOneBitSet(const ConstantInt *CI) {
uint64_t V = CI->getZExtValue();
return V && (V & (V-1)) == 0;
}
#if 0 // Currently unused
// isLowOnes - Return true if the constant is of the form 0+1+.
static bool isLowOnes(const ConstantInt *CI) {
uint64_t V = CI->getZExtValue();
// There won't be bits set in parts that the type doesn't contain.
V &= ConstantInt::getAllOnesValue(CI->getType())->getZExtValue();
uint64_t U = V+1; // If it is low ones, this should be a power of two.
return U && V && (U & V) == 0;
}
#endif
// isHighOnes - Return true if the constant is of the form 1+0+.
// This is the same as lowones(~X).
static bool isHighOnes(const ConstantInt *CI) {
uint64_t V = ~CI->getZExtValue();
if (~V == 0) return false; // 0's does not match "1+"
// There won't be bits set in parts that the type doesn't contain.
V &= ConstantInt::getAllOnesValue(CI->getType())->getZExtValue();
uint64_t U = V+1; // If it is low ones, this should be a power of two.
return U && V && (U & V) == 0;
}
/// getSetCondCode - Encode a setcc opcode into a three bit mask. These bits
/// are carefully arranged to allow folding of expressions such as:
///
/// (A < B) | (A > B) --> (A != B)
///
/// Bit value '4' represents that the comparison is true if A > B, bit value '2'
/// represents that the comparison is true if A == B, and bit value '1' is true
/// if A < B.
///
static unsigned getSetCondCode(const SetCondInst *SCI) {
switch (SCI->getOpcode()) {
// False -> 0
case Instruction::SetGT: return 1;
case Instruction::SetEQ: return 2;
case Instruction::SetGE: return 3;
case Instruction::SetLT: return 4;
case Instruction::SetNE: return 5;
case Instruction::SetLE: return 6;
// True -> 7
default:
assert(0 && "Invalid SetCC opcode!");
return 0;
}
}
/// getSetCCValue - This is the complement of getSetCondCode, which turns an
/// opcode and two operands into either a constant true or false, or a brand new
/// SetCC instruction.
static Value *getSetCCValue(unsigned Opcode, Value *LHS, Value *RHS) {
switch (Opcode) {
case 0: return ConstantBool::getFalse();
case 1: return new SetCondInst(Instruction::SetGT, LHS, RHS);
case 2: return new SetCondInst(Instruction::SetEQ, LHS, RHS);
case 3: return new SetCondInst(Instruction::SetGE, LHS, RHS);
case 4: return new SetCondInst(Instruction::SetLT, LHS, RHS);
case 5: return new SetCondInst(Instruction::SetNE, LHS, RHS);
case 6: return new SetCondInst(Instruction::SetLE, LHS, RHS);
case 7: return ConstantBool::getTrue();
default: assert(0 && "Illegal SetCCCode!"); return 0;
}
}
// FoldSetCCLogical - Implements (setcc1 A, B) & (setcc2 A, B) --> (setcc3 A, B)
struct FoldSetCCLogical {
InstCombiner &IC;
Value *LHS, *RHS;
FoldSetCCLogical(InstCombiner &ic, SetCondInst *SCI)
: IC(ic), LHS(SCI->getOperand(0)), RHS(SCI->getOperand(1)) {}
bool shouldApply(Value *V) const {
if (SetCondInst *SCI = dyn_cast<SetCondInst>(V))
return (SCI->getOperand(0) == LHS && SCI->getOperand(1) == RHS ||
SCI->getOperand(0) == RHS && SCI->getOperand(1) == LHS);
return false;
}
Instruction *apply(BinaryOperator &Log) const {
SetCondInst *SCI = cast<SetCondInst>(Log.getOperand(0));
if (SCI->getOperand(0) != LHS) {
assert(SCI->getOperand(1) == LHS);
SCI->swapOperands(); // Swap the LHS and RHS of the SetCC
}
unsigned LHSCode = getSetCondCode(SCI);
unsigned RHSCode = getSetCondCode(cast<SetCondInst>(Log.getOperand(1)));
unsigned Code;
switch (Log.getOpcode()) {
case Instruction::And: Code = LHSCode & RHSCode; break;
case Instruction::Or: Code = LHSCode | RHSCode; break;
case Instruction::Xor: Code = LHSCode ^ RHSCode; break;
default: assert(0 && "Illegal logical opcode!"); return 0;
}
Value *RV = getSetCCValue(Code, LHS, RHS);
if (Instruction *I = dyn_cast<Instruction>(RV))
return I;
// Otherwise, it's a constant boolean value...
return IC.ReplaceInstUsesWith(Log, RV);
}
};
// OptAndOp - This handles expressions of the form ((val OP C1) & C2). Where
// the Op parameter is 'OP', OpRHS is 'C1', and AndRHS is 'C2'. Op is
// guaranteed to be either a shift instruction or a binary operator.
Instruction *InstCombiner::OptAndOp(Instruction *Op,
ConstantIntegral *OpRHS,
ConstantIntegral *AndRHS,
BinaryOperator &TheAnd) {
Value *X = Op->getOperand(0);
Constant *Together = 0;
if (!isa<ShiftInst>(Op))
Together = ConstantExpr::getAnd(AndRHS, OpRHS);
switch (Op->getOpcode()) {
case Instruction::Xor:
if (Op->hasOneUse()) {
// (X ^ C1) & C2 --> (X & C2) ^ (C1&C2)
std::string OpName = Op->getName(); Op->setName("");
Instruction *And = BinaryOperator::createAnd(X, AndRHS, OpName);
InsertNewInstBefore(And, TheAnd);
return BinaryOperator::createXor(And, Together);
}
break;
case Instruction::Or:
if (Together == AndRHS) // (X | C) & C --> C
return ReplaceInstUsesWith(TheAnd, AndRHS);
if (Op->hasOneUse() && Together != OpRHS) {
// (X | C1) & C2 --> (X | (C1&C2)) & C2
std::string Op0Name = Op->getName(); Op->setName("");
Instruction *Or = BinaryOperator::createOr(X, Together, Op0Name);
InsertNewInstBefore(Or, TheAnd);
return BinaryOperator::createAnd(Or, AndRHS);
}
break;
case Instruction::Add:
if (Op->hasOneUse()) {
// Adding a one to a single bit bit-field should be turned into an XOR
// of the bit. First thing to check is to see if this AND is with a
// single bit constant.
uint64_t AndRHSV = cast<ConstantInt>(AndRHS)->getZExtValue();
// Clear bits that are not part of the constant.
AndRHSV &= AndRHS->getType()->getIntegralTypeMask();
// If there is only one bit set...
if (isOneBitSet(cast<ConstantInt>(AndRHS))) {
// Ok, at this point, we know that we are masking the result of the
// ADD down to exactly one bit. If the constant we are adding has
// no bits set below this bit, then we can eliminate the ADD.
uint64_t AddRHS = cast<ConstantInt>(OpRHS)->getZExtValue();
// Check to see if any bits below the one bit set in AndRHSV are set.
if ((AddRHS & (AndRHSV-1)) == 0) {
// If not, the only thing that can effect the output of the AND is
// the bit specified by AndRHSV. If that bit is set, the effect of
// the XOR is to toggle the bit. If it is clear, then the ADD has
// no effect.
if ((AddRHS & AndRHSV) == 0) { // Bit is not set, noop
TheAnd.setOperand(0, X);
return &TheAnd;
} else {
std::string Name = Op->getName(); Op->setName("");
// Pull the XOR out of the AND.
Instruction *NewAnd = BinaryOperator::createAnd(X, AndRHS, Name);
InsertNewInstBefore(NewAnd, TheAnd);
return BinaryOperator::createXor(NewAnd, AndRHS);
}
}
}
}
break;
case Instruction::Shl: {
// We know that the AND will not produce any of the bits shifted in, so if
// the anded constant includes them, clear them now!
//
Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
Constant *ShlMask = ConstantExpr::getShl(AllOne, OpRHS);
Constant *CI = ConstantExpr::getAnd(AndRHS, ShlMask);
if (CI == ShlMask) { // Masking out bits that the shift already masks
return ReplaceInstUsesWith(TheAnd, Op); // No need for the and.
} else if (CI != AndRHS) { // Reducing bits set in and.
TheAnd.setOperand(1, CI);
return &TheAnd;
}
break;
}
case Instruction::LShr:
{
// We know that the AND will not produce any of the bits shifted in, so if
// the anded constant includes them, clear them now! This only applies to
// unsigned shifts, because a signed shr may bring in set bits!
//
Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
Constant *ShrMask = ConstantExpr::getLShr(AllOne, OpRHS);
Constant *CI = ConstantExpr::getAnd(AndRHS, ShrMask);
if (CI == ShrMask) { // Masking out bits that the shift already masks.
return ReplaceInstUsesWith(TheAnd, Op);
} else if (CI != AndRHS) {
TheAnd.setOperand(1, CI); // Reduce bits set in and cst.
return &TheAnd;
}
break;
}
case Instruction::AShr:
// Signed shr.
// See if this is shifting in some sign extension, then masking it out
// with an and.
if (Op->hasOneUse()) {
Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
Constant *ShrMask = ConstantExpr::getLShr(AllOne, OpRHS);
Constant *CI = ConstantExpr::getAnd(AndRHS, ShrMask);
if (CI == AndRHS) { // Masking out bits shifted in.
// Make the argument unsigned.
Value *ShVal = Op->getOperand(0);
ShVal = InsertNewInstBefore(new ShiftInst(Instruction::LShr, ShVal,
OpRHS, Op->getName()),
TheAnd);
Value *AndRHS2 = ConstantExpr::getCast(AndRHS, ShVal->getType());
return BinaryOperator::createAnd(ShVal, AndRHS2, TheAnd.getName());
}
}
break;
}
return 0;
}
/// InsertRangeTest - Emit a computation of: (V >= Lo && V < Hi) if Inside is
/// true, otherwise (V < Lo || V >= Hi). In pratice, we emit the more efficient
/// (V-Lo) <u Hi-Lo. This method expects that Lo <= Hi. IB is the location to
/// insert new instructions.
Instruction *InstCombiner::InsertRangeTest(Value *V, Constant *Lo, Constant *Hi,
bool Inside, Instruction &IB) {
assert(cast<ConstantBool>(ConstantExpr::getSetLE(Lo, Hi))->getValue() &&
"Lo is not <= Hi in range emission code!");
if (Inside) {
if (Lo == Hi) // Trivially false.
return new SetCondInst(Instruction::SetNE, V, V);
if (cast<ConstantIntegral>(Lo)->isMinValue())
return new SetCondInst(Instruction::SetLT, V, Hi);
Constant *AddCST = ConstantExpr::getNeg(Lo);
Instruction *Add = BinaryOperator::createAdd(V, AddCST,V->getName()+".off");
InsertNewInstBefore(Add, IB);
// Convert to unsigned for the comparison.
const Type *UnsType = Add->getType()->getUnsignedVersion();
Value *OffsetVal = InsertCastBefore(Add, UnsType, IB);
AddCST = ConstantExpr::getAdd(AddCST, Hi);
AddCST = ConstantExpr::getCast(AddCST, UnsType);
return new SetCondInst(Instruction::SetLT, OffsetVal, AddCST);
}
if (Lo == Hi) // Trivially true.
return new SetCondInst(Instruction::SetEQ, V, V);
Hi = SubOne(cast<ConstantInt>(Hi));
// V < 0 || V >= Hi ->'V > Hi-1'
if (cast<ConstantIntegral>(Lo)->isMinValue())
return new SetCondInst(Instruction::SetGT, V, Hi);
// Emit X-Lo > Hi-Lo-1
Constant *AddCST = ConstantExpr::getNeg(Lo);
Instruction *Add = BinaryOperator::createAdd(V, AddCST, V->getName()+".off");
InsertNewInstBefore(Add, IB);
// Convert to unsigned for the comparison.
const Type *UnsType = Add->getType()->getUnsignedVersion();
Value *OffsetVal = InsertCastBefore(Add, UnsType, IB);
AddCST = ConstantExpr::getAdd(AddCST, Hi);
AddCST = ConstantExpr::getCast(AddCST, UnsType);
return new SetCondInst(Instruction::SetGT, OffsetVal, AddCST);
}
// isRunOfOnes - Returns true iff Val consists of one contiguous run of 1s with
// any number of 0s on either side. The 1s are allowed to wrap from LSB to
// MSB, so 0x000FFF0, 0x0000FFFF, and 0xFF0000FF are all runs. 0x0F0F0000 is
// not, since all 1s are not contiguous.
static bool isRunOfOnes(ConstantIntegral *Val, unsigned &MB, unsigned &ME) {
uint64_t V = Val->getZExtValue();
if (!isShiftedMask_64(V)) return false;
// look for the first zero bit after the run of ones
MB = 64-CountLeadingZeros_64((V - 1) ^ V);
// look for the first non-zero bit
ME = 64-CountLeadingZeros_64(V);
return true;
}
/// FoldLogicalPlusAnd - This is part of an expression (LHS +/- RHS) & Mask,
/// where isSub determines whether the operator is a sub. If we can fold one of
/// the following xforms:
///
/// ((A & N) +/- B) & Mask -> (A +/- B) & Mask iff N&Mask == Mask
/// ((A | N) +/- B) & Mask -> (A +/- B) & Mask iff N&Mask == 0
/// ((A ^ N) +/- B) & Mask -> (A +/- B) & Mask iff N&Mask == 0
///
/// return (A +/- B).
///
Value *InstCombiner::FoldLogicalPlusAnd(Value *LHS, Value *RHS,
ConstantIntegral *Mask, bool isSub,
Instruction &I) {
Instruction *LHSI = dyn_cast<Instruction>(LHS);
if (!LHSI || LHSI->getNumOperands() != 2 ||
!isa<ConstantInt>(LHSI->getOperand(1))) return 0;
ConstantInt *N = cast<ConstantInt>(LHSI->getOperand(1));
switch (LHSI->getOpcode()) {
default: return 0;
case Instruction::And:
if (ConstantExpr::getAnd(N, Mask) == Mask) {
// If the AndRHS is a power of two minus one (0+1+), this is simple.
if ((Mask->getZExtValue() & Mask->getZExtValue()+1) == 0)
break;
// Otherwise, if Mask is 0+1+0+, and if B is known to have the low 0+
// part, we don't need any explicit masks to take them out of A. If that
// is all N is, ignore it.
unsigned MB, ME;
if (isRunOfOnes(Mask, MB, ME)) { // begin/end bit of run, inclusive
uint64_t Mask = RHS->getType()->getIntegralTypeMask();
Mask >>= 64-MB+1;
if (MaskedValueIsZero(RHS, Mask))
break;
}
}
return 0;
case Instruction::Or:
case Instruction::Xor:
// If the AndRHS is a power of two minus one (0+1+), and N&Mask == 0
if ((Mask->getZExtValue() & Mask->getZExtValue()+1) == 0 &&
ConstantExpr::getAnd(N, Mask)->isNullValue())
break;
return 0;
}
Instruction *New;
if (isSub)
New = BinaryOperator::createSub(LHSI->getOperand(0), RHS, "fold");
else
New = BinaryOperator::createAdd(LHSI->getOperand(0), RHS, "fold");
return InsertNewInstBefore(New, I);
}
Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
bool Changed = SimplifyCommutative(I);
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
if (isa<UndefValue>(Op1)) // X & undef -> 0
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
// and X, X = X
if (Op0 == Op1)
return ReplaceInstUsesWith(I, Op1);
// See if we can simplify any instructions used by the instruction whose sole
// purpose is to compute bits we don't care about.
uint64_t KnownZero, KnownOne;
if (!isa<PackedType>(I.getType()) &&
SimplifyDemandedBits(&I, I.getType()->getIntegralTypeMask(),
KnownZero, KnownOne))
return &I;
if (ConstantIntegral *AndRHS = dyn_cast<ConstantIntegral>(Op1)) {
uint64_t AndRHSMask = AndRHS->getZExtValue();
uint64_t TypeMask = Op0->getType()->getIntegralTypeMask();
uint64_t NotAndRHS = AndRHSMask^TypeMask;
// Optimize a variety of ((val OP C1) & C2) combinations...
if (isa<BinaryOperator>(Op0) || isa<ShiftInst>(Op0)) {
Instruction *Op0I = cast<Instruction>(Op0);
Value *Op0LHS = Op0I->getOperand(0);
Value *Op0RHS = Op0I->getOperand(1);
switch (Op0I->getOpcode()) {
case Instruction::Xor:
case Instruction::Or:
// If the mask is only needed on one incoming arm, push it up.
if (Op0I->hasOneUse()) {
if (MaskedValueIsZero(Op0LHS, NotAndRHS)) {
// Not masking anything out for the LHS, move to RHS.
Instruction *NewRHS = BinaryOperator::createAnd(Op0RHS, AndRHS,
Op0RHS->getName()+".masked");
InsertNewInstBefore(NewRHS, I);
return BinaryOperator::create(
cast<BinaryOperator>(Op0I)->getOpcode(), Op0LHS, NewRHS);
}
if (!isa<Constant>(Op0RHS) &&
MaskedValueIsZero(Op0RHS, NotAndRHS)) {
// Not masking anything out for the RHS, move to LHS.
Instruction *NewLHS = BinaryOperator::createAnd(Op0LHS, AndRHS,
Op0LHS->getName()+".masked");
InsertNewInstBefore(NewLHS, I);
return BinaryOperator::create(
cast<BinaryOperator>(Op0I)->getOpcode(), NewLHS, Op0RHS);
}
}
break;
case Instruction::Add:
// ((A & N) + B) & AndRHS -> (A + B) & AndRHS iff N&AndRHS == AndRHS.
// ((A | N) + B) & AndRHS -> (A + B) & AndRHS iff N&AndRHS == 0
// ((A ^ N) + B) & AndRHS -> (A + B) & AndRHS iff N&AndRHS == 0
if (Value *V = FoldLogicalPlusAnd(Op0LHS, Op0RHS, AndRHS, false, I))
return BinaryOperator::createAnd(V, AndRHS);
if (Value *V = FoldLogicalPlusAnd(Op0RHS, Op0LHS, AndRHS, false, I))
return BinaryOperator::createAnd(V, AndRHS); // Add commutes
break;
case Instruction::Sub:
// ((A & N) - B) & AndRHS -> (A - B) & AndRHS iff N&AndRHS == AndRHS.
// ((A | N) - B) & AndRHS -> (A - B) & AndRHS iff N&AndRHS == 0
// ((A ^ N) - B) & AndRHS -> (A - B) & AndRHS iff N&AndRHS == 0
if (Value *V = FoldLogicalPlusAnd(Op0LHS, Op0RHS, AndRHS, true, I))
return BinaryOperator::createAnd(V, AndRHS);
break;
}
if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
if (Instruction *Res = OptAndOp(Op0I, Op0CI, AndRHS, I))
return Res;
} else if (CastInst *CI = dyn_cast<CastInst>(Op0)) {
const Type *SrcTy = CI->getOperand(0)->getType();
// If this is an integer truncation or change from signed-to-unsigned, and
// if the source is an and/or with immediate, transform it. This
// frequently occurs for bitfield accesses.
if (Instruction *CastOp = dyn_cast<Instruction>(CI->getOperand(0))) {
if (SrcTy->getPrimitiveSizeInBits() >=
I.getType()->getPrimitiveSizeInBits() &&
CastOp->getNumOperands() == 2)
if (ConstantInt *AndCI = dyn_cast<ConstantInt>(CastOp->getOperand(1)))
if (CastOp->getOpcode() == Instruction::And) {
// Change: and (cast (and X, C1) to T), C2
// into : and (cast X to T), trunc(C1)&C2
// This will folds the two ands together, which may allow other
// simplifications.
Instruction *NewCast =
new CastInst(CastOp->getOperand(0), I.getType(),
CastOp->getName()+".shrunk");
NewCast = InsertNewInstBefore(NewCast, I);
Constant *C3=ConstantExpr::getCast(AndCI, I.getType());//trunc(C1)
C3 = ConstantExpr::getAnd(C3, AndRHS); // trunc(C1)&C2
return BinaryOperator::createAnd(NewCast, C3);
} else if (CastOp->getOpcode() == Instruction::Or) {
// Change: and (cast (or X, C1) to T), C2
// into : trunc(C1)&C2 iff trunc(C1)&C2 == C2
Constant *C3=ConstantExpr::getCast(AndCI, I.getType());//trunc(C1)
if (ConstantExpr::getAnd(C3, AndRHS) == AndRHS) // trunc(C1)&C2
return ReplaceInstUsesWith(I, AndRHS);
}
}
}
// Try to fold constant and into select arguments.
if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
if (Instruction *R = FoldOpIntoSelect(I, SI, this))
return R;
if (isa<PHINode>(Op0))
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
}
Value *Op0NotVal = dyn_castNotVal(Op0);
Value *Op1NotVal = dyn_castNotVal(Op1);
if (Op0NotVal == Op1 || Op1NotVal == Op0) // A & ~A == ~A & A == 0
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
// (~A & ~B) == (~(A | B)) - De Morgan's Law
if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
Instruction *Or = BinaryOperator::createOr(Op0NotVal, Op1NotVal,
I.getName()+".demorgan");
InsertNewInstBefore(Or, I);
return BinaryOperator::createNot(Or);
}
{
Value *A = 0, *B = 0;
if (match(Op0, m_Or(m_Value(A), m_Value(B))))
if (A == Op1 || B == Op1) // (A | ?) & A --> A
return ReplaceInstUsesWith(I, Op1);
if (match(Op1, m_Or(m_Value(A), m_Value(B))))
if (A == Op0 || B == Op0) // A & (A | ?) --> A
return ReplaceInstUsesWith(I, Op0);
if (Op0->hasOneUse() &&
match(Op0, m_Xor(m_Value(A), m_Value(B)))) {
if (A == Op1) { // (A^B)&A -> A&(A^B)
I.swapOperands(); // Simplify below
std::swap(Op0, Op1);
} else if (B == Op1) { // (A^B)&B -> B&(B^A)
cast<BinaryOperator>(Op0)->swapOperands();
I.swapOperands(); // Simplify below
std::swap(Op0, Op1);
}
}
if (Op1->hasOneUse() &&
match(Op1, m_Xor(m_Value(A), m_Value(B)))) {
if (B == Op0) { // B&(A^B) -> B&(B^A)
cast<BinaryOperator>(Op1)->swapOperands();
std::swap(A, B);
}
if (A == Op0) { // A&(A^B) -> A & ~B
Instruction *NotB = BinaryOperator::createNot(B, "tmp");
InsertNewInstBefore(NotB, I);
return BinaryOperator::createAnd(A, NotB);
}
}
}
if (SetCondInst *RHS = dyn_cast<SetCondInst>(Op1)) {
// (setcc1 A, B) & (setcc2 A, B) --> (setcc3 A, B)
if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
return R;
Value *LHSVal, *RHSVal;
ConstantInt *LHSCst, *RHSCst;
Instruction::BinaryOps LHSCC, RHSCC;
if (match(Op0, m_SetCond(LHSCC, m_Value(LHSVal), m_ConstantInt(LHSCst))))
if (match(RHS, m_SetCond(RHSCC, m_Value(RHSVal), m_ConstantInt(RHSCst))))
if (LHSVal == RHSVal && // Found (X setcc C1) & (X setcc C2)
// Set[GL]E X, CST is folded to Set[GL]T elsewhere.
LHSCC != Instruction::SetGE && LHSCC != Instruction::SetLE &&
RHSCC != Instruction::SetGE && RHSCC != Instruction::SetLE) {
// Ensure that the larger constant is on the RHS.
Constant *Cmp = ConstantExpr::getSetGT(LHSCst, RHSCst);
SetCondInst *LHS = cast<SetCondInst>(Op0);
if (cast<ConstantBool>(Cmp)->getValue()) {
std::swap(LHS, RHS);
std::swap(LHSCst, RHSCst);
std::swap(LHSCC, RHSCC);
}
// At this point, we know we have have two setcc instructions
// comparing a value against two constants and and'ing the result
// together. Because of the above check, we know that we only have
// SetEQ, SetNE, SetLT, and SetGT here. We also know (from the
// FoldSetCCLogical check above), that the two constants are not
// equal.
assert(LHSCst != RHSCst && "Compares not folded above?");
switch (LHSCC) {
default: assert(0 && "Unknown integer condition code!");
case Instruction::SetEQ:
switch (RHSCC) {
default: assert(0 && "Unknown integer condition code!");
case Instruction::SetEQ: // (X == 13 & X == 15) -> false
case Instruction::SetGT: // (X == 13 & X > 15) -> false
return ReplaceInstUsesWith(I, ConstantBool::getFalse());
case Instruction::SetNE: // (X == 13 & X != 15) -> X == 13
case Instruction::SetLT: // (X == 13 & X < 15) -> X == 13
return ReplaceInstUsesWith(I, LHS);
}
case Instruction::SetNE:
switch (RHSCC) {
default: assert(0 && "Unknown integer condition code!");
case Instruction::SetLT:
if (LHSCst == SubOne(RHSCst)) // (X != 13 & X < 14) -> X < 13
return new SetCondInst(Instruction::SetLT, LHSVal, LHSCst);
break; // (X != 13 & X < 15) -> no change
case Instruction::SetEQ: // (X != 13 & X == 15) -> X == 15
case Instruction::SetGT: // (X != 13 & X > 15) -> X > 15
return ReplaceInstUsesWith(I, RHS);
case Instruction::SetNE:
if (LHSCst == SubOne(RHSCst)) {// (X != 13 & X != 14) -> X-13 >u 1
Constant *AddCST = ConstantExpr::getNeg(LHSCst);
Instruction *Add = BinaryOperator::createAdd(LHSVal, AddCST,
LHSVal->getName()+".off");
InsertNewInstBefore(Add, I);
const Type *UnsType = Add->getType()->getUnsignedVersion();
Value *OffsetVal = InsertCastBefore(Add, UnsType, I);
AddCST = ConstantExpr::getSub(RHSCst, LHSCst);
AddCST = ConstantExpr::getCast(AddCST, UnsType);
return new SetCondInst(Instruction::SetGT, OffsetVal, AddCST);
}
break; // (X != 13 & X != 15) -> no change
}
break;
case Instruction::SetLT:
switch (RHSCC) {
default: assert(0 && "Unknown integer condition code!");
case Instruction::SetEQ: // (X < 13 & X == 15) -> false
case Instruction::SetGT: // (X < 13 & X > 15) -> false
return ReplaceInstUsesWith(I, ConstantBool::getFalse());
case Instruction::SetNE: // (X < 13 & X != 15) -> X < 13
case Instruction::SetLT: // (X < 13 & X < 15) -> X < 13
return ReplaceInstUsesWith(I, LHS);
}
case Instruction::SetGT:
switch (RHSCC) {
default: assert(0 && "Unknown integer condition code!");
case Instruction::SetEQ: // (X > 13 & X == 15) -> X > 13
return ReplaceInstUsesWith(I, LHS);
case Instruction::SetGT: // (X > 13 & X > 15) -> X > 15
return ReplaceInstUsesWith(I, RHS);
case Instruction::SetNE:
if (RHSCst == AddOne(LHSCst)) // (X > 13 & X != 14) -> X > 14
return new SetCondInst(Instruction::SetGT, LHSVal, RHSCst);
break; // (X > 13 & X != 15) -> no change
case Instruction::SetLT: // (X > 13 & X < 15) -> (X-14) <u 1
return InsertRangeTest(LHSVal, AddOne(LHSCst), RHSCst, true, I);
}
}
}
}
// fold (and (cast A), (cast B)) -> (cast (and A, B))
if (CastInst *Op0C = dyn_cast<CastInst>(Op0)) {
const Type *SrcTy = Op0C->getOperand(0)->getType();
if (CastInst *Op1C = dyn_cast<CastInst>(Op1))
if (SrcTy == Op1C->getOperand(0)->getType() && SrcTy->isIntegral() &&
// Only do this if the casts both really cause code to be generated.
ValueRequiresCast(Op0C->getOperand(0), I.getType(), TD) &&
ValueRequiresCast(Op1C->getOperand(0), I.getType(), TD)) {
Instruction *NewOp = BinaryOperator::createAnd(Op0C->getOperand(0),
Op1C->getOperand(0),
I.getName());
InsertNewInstBefore(NewOp, I);
return new CastInst(NewOp, I.getType());
}
}
return Changed ? &I : 0;
}
/// CollectBSwapParts - Look to see if the specified value defines a single byte
/// in the result. If it does, and if the specified byte hasn't been filled in
/// yet, fill it in and return false.
static bool CollectBSwapParts(Value *V, std::vector<Value*> &ByteValues) {
Instruction *I = dyn_cast<Instruction>(V);
if (I == 0) return true;
// If this is an or instruction, it is an inner node of the bswap.
if (I->getOpcode() == Instruction::Or)
return CollectBSwapParts(I->getOperand(0), ByteValues) ||
CollectBSwapParts(I->getOperand(1), ByteValues);
// If this is a shift by a constant int, and it is "24", then its operand
// defines a byte. We only handle unsigned types here.
if (isa<ShiftInst>(I) && isa<ConstantInt>(I->getOperand(1))) {
// Not shifting the entire input by N-1 bytes?
if (cast<ConstantInt>(I->getOperand(1))->getZExtValue() !=
8*(ByteValues.size()-1))
return true;
unsigned DestNo;
if (I->getOpcode() == Instruction::Shl) {
// X << 24 defines the top byte with the lowest of the input bytes.
DestNo = ByteValues.size()-1;
} else {
// X >>u 24 defines the low byte with the highest of the input bytes.
DestNo = 0;
}
// If the destination byte value is already defined, the values are or'd
// together, which isn't a bswap (unless it's an or of the same bits).
if (ByteValues[DestNo] && ByteValues[DestNo] != I->getOperand(0))
return true;
ByteValues[DestNo] = I->getOperand(0);
return false;
}
// Otherwise, we can only handle and(shift X, imm), imm). Bail out of if we
// don't have this.
Value *Shift = 0, *ShiftLHS = 0;
ConstantInt *AndAmt = 0, *ShiftAmt = 0;
if (!match(I, m_And(m_Value(Shift), m_ConstantInt(AndAmt))) ||
!match(Shift, m_Shift(m_Value(ShiftLHS), m_ConstantInt(ShiftAmt))))
return true;
Instruction *SI = cast<Instruction>(Shift);
// Make sure that the shift amount is by a multiple of 8 and isn't too big.
if (ShiftAmt->getZExtValue() & 7 ||
ShiftAmt->getZExtValue() > 8*ByteValues.size())
return true;
// Turn 0xFF -> 0, 0xFF00 -> 1, 0xFF0000 -> 2, etc.
unsigned DestByte;
for (DestByte = 0; DestByte != ByteValues.size(); ++DestByte)
if (AndAmt->getZExtValue() == uint64_t(0xFF) << 8*DestByte)
break;
// Unknown mask for bswap.
if (DestByte == ByteValues.size()) return true;
unsigned ShiftBytes = ShiftAmt->getZExtValue()/8;
unsigned SrcByte;
if (SI->getOpcode() == Instruction::Shl)
SrcByte = DestByte - ShiftBytes;
else
SrcByte = DestByte + ShiftBytes;
// If the SrcByte isn't a bswapped value from the DestByte, reject it.
if (SrcByte != ByteValues.size()-DestByte-1)
return true;
// If the destination byte value is already defined, the values are or'd
// together, which isn't a bswap (unless it's an or of the same bits).
if (ByteValues[DestByte] && ByteValues[DestByte] != SI->getOperand(0))
return true;
ByteValues[DestByte] = SI->getOperand(0);
return false;
}
/// MatchBSwap - Given an OR instruction, check to see if this is a bswap idiom.
/// If so, insert the new bswap intrinsic and return it.
Instruction *InstCombiner::MatchBSwap(BinaryOperator &I) {
// We can only handle bswap of unsigned integers, and cannot bswap one byte.
if (!I.getType()->isUnsigned() || I.getType() == Type::UByteTy)
return 0;
/// ByteValues - For each byte of the result, we keep track of which value
/// defines each byte.
std::vector<Value*> ByteValues;
ByteValues.resize(I.getType()->getPrimitiveSize());
// Try to find all the pieces corresponding to the bswap.
if (CollectBSwapParts(I.getOperand(0), ByteValues) ||
CollectBSwapParts(I.getOperand(1), ByteValues))
return 0;
// Check to see if all of the bytes come from the same value.
Value *V = ByteValues[0];
if (V == 0) return 0; // Didn't find a byte? Must be zero.
// Check to make sure that all of the bytes come from the same value.
for (unsigned i = 1, e = ByteValues.size(); i != e; ++i)
if (ByteValues[i] != V)
return 0;
// If they do then *success* we can turn this into a bswap. Figure out what
// bswap to make it into.
Module *M = I.getParent()->getParent()->getParent();
const char *FnName = 0;
if (I.getType() == Type::UShortTy)
FnName = "llvm.bswap.i16";
else if (I.getType() == Type::UIntTy)
FnName = "llvm.bswap.i32";
else if (I.getType() == Type::ULongTy)
FnName = "llvm.bswap.i64";
else
assert(0 && "Unknown integer type!");
Function *F = M->getOrInsertFunction(FnName, I.getType(), I.getType(), NULL);
return new CallInst(F, V);
}
Instruction *InstCombiner::visitOr(BinaryOperator &I) {
bool Changed = SimplifyCommutative(I);
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
if (isa<UndefValue>(Op1))
return ReplaceInstUsesWith(I, // X | undef -> -1
ConstantIntegral::getAllOnesValue(I.getType()));
// or X, X = X
if (Op0 == Op1)
return ReplaceInstUsesWith(I, Op0);
// See if we can simplify any instructions used by the instruction whose sole
// purpose is to compute bits we don't care about.
uint64_t KnownZero, KnownOne;
if (!isa<PackedType>(I.getType()) &&
SimplifyDemandedBits(&I, I.getType()->getIntegralTypeMask(),
KnownZero, KnownOne))
return &I;
// or X, -1 == -1
if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
ConstantInt *C1 = 0; Value *X = 0;
// (X & C1) | C2 --> (X | C2) & (C1|C2)
if (match(Op0, m_And(m_Value(X), m_ConstantInt(C1))) && isOnlyUse(Op0)) {
Instruction *Or = BinaryOperator::createOr(X, RHS, Op0->getName());
Op0->setName("");
InsertNewInstBefore(Or, I);
return BinaryOperator::createAnd(Or, ConstantExpr::getOr(RHS, C1));
}
// (X ^ C1) | C2 --> (X | C2) ^ (C1&~C2)
if (match(Op0, m_Xor(m_Value(X), m_ConstantInt(C1))) && isOnlyUse(Op0)) {
std::string Op0Name = Op0->getName(); Op0->setName("");
Instruction *Or = BinaryOperator::createOr(X, RHS, Op0Name);
InsertNewInstBefore(Or, I);
return BinaryOperator::createXor(Or,
ConstantExpr::getAnd(C1, ConstantExpr::getNot(RHS)));
}
// Try to fold constant and into select arguments.
if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
if (Instruction *R = FoldOpIntoSelect(I, SI, this))
return R;
if (isa<PHINode>(Op0))
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
}
Value *A = 0, *B = 0;
ConstantInt *C1 = 0, *C2 = 0;
if (match(Op0, m_And(m_Value(A), m_Value(B))))
if (A == Op1 || B == Op1) // (A & ?) | A --> A
return ReplaceInstUsesWith(I, Op1);
if (match(Op1, m_And(m_Value(A), m_Value(B))))
if (A == Op0 || B == Op0) // A | (A & ?) --> A
return ReplaceInstUsesWith(I, Op0);
// (A | B) | C and A | (B | C) -> bswap if possible.
// (A >> B) | (C << D) and (A << B) | (B >> C) -> bswap if possible.
if (match(Op0, m_Or(m_Value(), m_Value())) ||
match(Op1, m_Or(m_Value(), m_Value())) ||
(match(Op0, m_Shift(m_Value(), m_Value())) &&
match(Op1, m_Shift(m_Value(), m_Value())))) {
if (Instruction *BSwap = MatchBSwap(I))
return BSwap;
}
// (X^C)|Y -> (X|Y)^C iff Y&C == 0
if (Op0->hasOneUse() && match(Op0, m_Xor(m_Value(A), m_ConstantInt(C1))) &&
MaskedValueIsZero(Op1, C1->getZExtValue())) {
Instruction *NOr = BinaryOperator::createOr(A, Op1, Op0->getName());
Op0->setName("");
return BinaryOperator::createXor(InsertNewInstBefore(NOr, I), C1);
}
// Y|(X^C) -> (X|Y)^C iff Y&C == 0
if (Op1->hasOneUse() && match(Op1, m_Xor(m_Value(A), m_ConstantInt(C1))) &&
MaskedValueIsZero(Op0, C1->getZExtValue())) {
Instruction *NOr = BinaryOperator::createOr(A, Op0, Op1->getName());
Op0->setName("");
return BinaryOperator::createXor(InsertNewInstBefore(NOr, I), C1);
}
// (A & C1)|(B & C2)
if (match(Op0, m_And(m_Value(A), m_ConstantInt(C1))) &&
match(Op1, m_And(m_Value(B), m_ConstantInt(C2)))) {
if (A == B) // (A & C1)|(A & C2) == A & (C1|C2)
return BinaryOperator::createAnd(A, ConstantExpr::getOr(C1, C2));
// If we have: ((V + N) & C1) | (V & C2)
// .. and C2 = ~C1 and C2 is 0+1+ and (N & C2) == 0
// replace with V+N.
if (C1 == ConstantExpr::getNot(C2)) {
Value *V1 = 0, *V2 = 0;
if ((C2->getZExtValue() & (C2->getZExtValue()+1)) == 0 && // C2 == 0+1+
match(A, m_Add(m_Value(V1), m_Value(V2)))) {
// Add commutes, try both ways.
if (V1 == B && MaskedValueIsZero(V2, C2->getZExtValue()))
return ReplaceInstUsesWith(I, A);
if (V2 == B && MaskedValueIsZero(V1, C2->getZExtValue()))
return ReplaceInstUsesWith(I, A);
}
// Or commutes, try both ways.
if ((C1->getZExtValue() & (C1->getZExtValue()+1)) == 0 &&
match(B, m_Add(m_Value(V1), m_Value(V2)))) {
// Add commutes, try both ways.
if (V1 == A && MaskedValueIsZero(V2, C1->getZExtValue()))
return ReplaceInstUsesWith(I, B);
if (V2 == A && MaskedValueIsZero(V1, C1->getZExtValue()))
return ReplaceInstUsesWith(I, B);
}
}
}
if (match(Op0, m_Not(m_Value(A)))) { // ~A | Op1
if (A == Op1) // ~A | A == -1
return ReplaceInstUsesWith(I,
ConstantIntegral::getAllOnesValue(I.getType()));
} else {
A = 0;
}
// Note, A is still live here!
if (match(Op1, m_Not(m_Value(B)))) { // Op0 | ~B
if (Op0 == B)
return ReplaceInstUsesWith(I,
ConstantIntegral::getAllOnesValue(I.getType()));
// (~A | ~B) == (~(A & B)) - De Morgan's Law
if (A && isOnlyUse(Op0) && isOnlyUse(Op1)) {
Value *And = InsertNewInstBefore(BinaryOperator::createAnd(A, B,
I.getName()+".demorgan"), I);
return BinaryOperator::createNot(And);
}
}
// (setcc1 A, B) | (setcc2 A, B) --> (setcc3 A, B)
if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1))) {
if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
return R;
Value *LHSVal, *RHSVal;
ConstantInt *LHSCst, *RHSCst;
Instruction::BinaryOps LHSCC, RHSCC;
if (match(Op0, m_SetCond(LHSCC, m_Value(LHSVal), m_ConstantInt(LHSCst))))
if (match(RHS, m_SetCond(RHSCC, m_Value(RHSVal), m_ConstantInt(RHSCst))))
if (LHSVal == RHSVal && // Found (X setcc C1) | (X setcc C2)
// Set[GL]E X, CST is folded to Set[GL]T elsewhere.
LHSCC != Instruction::SetGE && LHSCC != Instruction::SetLE &&
RHSCC != Instruction::SetGE && RHSCC != Instruction::SetLE) {
// Ensure that the larger constant is on the RHS.
Constant *Cmp = ConstantExpr::getSetGT(LHSCst, RHSCst);
SetCondInst *LHS = cast<SetCondInst>(Op0);
if (cast<ConstantBool>(Cmp)->getValue()) {
std::swap(LHS, RHS);
std::swap(LHSCst, RHSCst);
std::swap(LHSCC, RHSCC);
}
// At this point, we know we have have two setcc instructions
// comparing a value against two constants and or'ing the result
// together. Because of the above check, we know that we only have
// SetEQ, SetNE, SetLT, and SetGT here. We also know (from the
// FoldSetCCLogical check above), that the two constants are not
// equal.
assert(LHSCst != RHSCst && "Compares not folded above?");
switch (LHSCC) {
default: assert(0 && "Unknown integer condition code!");
case Instruction::SetEQ:
switch (RHSCC) {
default: assert(0 && "Unknown integer condition code!");
case Instruction::SetEQ:
if (LHSCst == SubOne(RHSCst)) {// (X == 13 | X == 14) -> X-13 <u 2
Constant *AddCST = ConstantExpr::getNeg(LHSCst);
Instruction *Add = BinaryOperator::createAdd(LHSVal, AddCST,
LHSVal->getName()+".off");
InsertNewInstBefore(Add, I);
const Type *UnsType = Add->getType()->getUnsignedVersion();
Value *OffsetVal = InsertCastBefore(Add, UnsType, I);
AddCST = ConstantExpr::getSub(AddOne(RHSCst), LHSCst);
AddCST = ConstantExpr::getCast(AddCST, UnsType);
return new SetCondInst(Instruction::SetLT, OffsetVal, AddCST);
}
break; // (X == 13 | X == 15) -> no change
case Instruction::SetGT: // (X == 13 | X > 14) -> no change
break;
case Instruction::SetNE: // (X == 13 | X != 15) -> X != 15
case Instruction::SetLT: // (X == 13 | X < 15) -> X < 15
return ReplaceInstUsesWith(I, RHS);
}
break;
case Instruction::SetNE:
switch (RHSCC) {
default: assert(0 && "Unknown integer condition code!");
case Instruction::SetEQ: // (X != 13 | X == 15) -> X != 13
case Instruction::SetGT: // (X != 13 | X > 15) -> X != 13
return ReplaceInstUsesWith(I, LHS);
case Instruction::SetNE: // (X != 13 | X != 15) -> true
case Instruction::SetLT: // (X != 13 | X < 15) -> true
return ReplaceInstUsesWith(I, ConstantBool::getTrue());
}
break;
case Instruction::SetLT:
switch (RHSCC) {
default: assert(0 && "Unknown integer condition code!");
case Instruction::SetEQ: // (X < 13 | X == 14) -> no change
break;
case Instruction::SetGT: // (X < 13 | X > 15) -> (X-13) > 2
return InsertRangeTest(LHSVal, LHSCst, AddOne(RHSCst), false, I);
case Instruction::SetNE: // (X < 13 | X != 15) -> X != 15
case Instruction::SetLT: // (X < 13 | X < 15) -> X < 15
return ReplaceInstUsesWith(I, RHS);
}
break;
case Instruction::SetGT:
switch (RHSCC) {
default: assert(0 && "Unknown integer condition code!");
case Instruction::SetEQ: // (X > 13 | X == 15) -> X > 13
case Instruction::SetGT: // (X > 13 | X > 15) -> X > 13
return ReplaceInstUsesWith(I, LHS);
case Instruction::SetNE: // (X > 13 | X != 15) -> true
case Instruction::SetLT: // (X > 13 | X < 15) -> true
return ReplaceInstUsesWith(I, ConstantBool::getTrue());
}
}
}
}
// fold (or (cast A), (cast B)) -> (cast (or A, B))
if (CastInst *Op0C = dyn_cast<CastInst>(Op0)) {
const Type *SrcTy = Op0C->getOperand(0)->getType();
if (CastInst *Op1C = dyn_cast<CastInst>(Op1))
if (SrcTy == Op1C->getOperand(0)->getType() && SrcTy->isIntegral() &&
// Only do this if the casts both really cause code to be generated.
ValueRequiresCast(Op0C->getOperand(0), I.getType(), TD) &&
ValueRequiresCast(Op1C->getOperand(0), I.getType(), TD)) {
Instruction *NewOp = BinaryOperator::createOr(Op0C->getOperand(0),
Op1C->getOperand(0),
I.getName());
InsertNewInstBefore(NewOp, I);
return new CastInst(NewOp, I.getType());
}
}
return Changed ? &I : 0;
}
// XorSelf - Implements: X ^ X --> 0
struct XorSelf {
Value *RHS;
XorSelf(Value *rhs) : RHS(rhs) {}
bool shouldApply(Value *LHS) const { return LHS == RHS; }
Instruction *apply(BinaryOperator &Xor) const {
return &Xor;
}
};
Instruction *InstCombiner::visitXor(BinaryOperator &I) {
bool Changed = SimplifyCommutative(I);
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
if (isa<UndefValue>(Op1))
return ReplaceInstUsesWith(I, Op1); // X ^ undef -> undef
// xor X, X = 0, even if X is nested in a sequence of Xor's.
if (Instruction *Result = AssociativeOpt(I, XorSelf(Op1))) {
assert(Result == &I && "AssociativeOpt didn't work?");
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
}
// See if we can simplify any instructions used by the instruction whose sole
// purpose is to compute bits we don't care about.
uint64_t KnownZero, KnownOne;
if (!isa<PackedType>(I.getType()) &&
SimplifyDemandedBits(&I, I.getType()->getIntegralTypeMask(),
KnownZero, KnownOne))
return &I;
if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0)) {
// xor (setcc A, B), true = not (setcc A, B) = setncc A, B
if (SetCondInst *SCI = dyn_cast<SetCondInst>(Op0I))
if (RHS == ConstantBool::getTrue() && SCI->hasOneUse())
return new SetCondInst(SCI->getInverseCondition(),
SCI->getOperand(0), SCI->getOperand(1));
// ~(c-X) == X-c-1 == X+(-c-1)
if (Op0I->getOpcode() == Instruction::Sub && RHS->isAllOnesValue())
if (Constant *Op0I0C = dyn_cast<Constant>(Op0I->getOperand(0))) {
Constant *NegOp0I0C = ConstantExpr::getNeg(Op0I0C);
Constant *ConstantRHS = ConstantExpr::getSub(NegOp0I0C,
ConstantInt::get(I.getType(), 1));
return BinaryOperator::createAdd(Op0I->getOperand(1), ConstantRHS);
}
// ~(~X & Y) --> (X | ~Y)
if (Op0I->getOpcode() == Instruction::And && RHS->isAllOnesValue()) {
if (dyn_castNotVal(Op0I->getOperand(1))) Op0I->swapOperands();
if (Value *Op0NotVal = dyn_castNotVal(Op0I->getOperand(0))) {
Instruction *NotY =
BinaryOperator::createNot(Op0I->getOperand(1),
Op0I->getOperand(1)->getName()+".not");
InsertNewInstBefore(NotY, I);
return BinaryOperator::createOr(Op0NotVal, NotY);
}
}
if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
if (Op0I->getOpcode() == Instruction::Add) {
// ~(X-c) --> (-c-1)-X
if (RHS->isAllOnesValue()) {
Constant *NegOp0CI = ConstantExpr::getNeg(Op0CI);
return BinaryOperator::createSub(
ConstantExpr::getSub(NegOp0CI,
ConstantInt::get(I.getType(), 1)),
Op0I->getOperand(0));
}
} else if (Op0I->getOpcode() == Instruction::Or) {
// (X|C1)^C2 -> X^(C1|C2) iff X&~C1 == 0
if (MaskedValueIsZero(Op0I->getOperand(0), Op0CI->getZExtValue())) {
Constant *NewRHS = ConstantExpr::getOr(Op0CI, RHS);
// Anything in both C1 and C2 is known to be zero, remove it from
// NewRHS.
Constant *CommonBits = ConstantExpr::getAnd(Op0CI, RHS);
NewRHS = ConstantExpr::getAnd(NewRHS,
ConstantExpr::getNot(CommonBits));
WorkList.push_back(Op0I);
I.setOperand(0, Op0I->getOperand(0));
I.setOperand(1, NewRHS);
return &I;
}
}
}
// Try to fold constant and into select arguments.
if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
if (Instruction *R = FoldOpIntoSelect(I, SI, this))
return R;
if (isa<PHINode>(Op0))
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
}
if (Value *X = dyn_castNotVal(Op0)) // ~A ^ A == -1
if (X == Op1)
return ReplaceInstUsesWith(I,
ConstantIntegral::getAllOnesValue(I.getType()));
if (Value *X = dyn_castNotVal(Op1)) // A ^ ~A == -1
if (X == Op0)
return ReplaceInstUsesWith(I,
ConstantIntegral::getAllOnesValue(I.getType()));
if (BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1))
if (Op1I->getOpcode() == Instruction::Or) {
if (Op1I->getOperand(0) == Op0) { // B^(B|A) == (A|B)^B
Op1I->swapOperands();
I.swapOperands();
std::swap(Op0, Op1);
} else if (Op1I->getOperand(1) == Op0) { // B^(A|B) == (A|B)^B
I.swapOperands(); // Simplified below.
std::swap(Op0, Op1);
}
} else if (Op1I->getOpcode() == Instruction::Xor) {
if (Op0 == Op1I->getOperand(0)) // A^(A^B) == B
return ReplaceInstUsesWith(I, Op1I->getOperand(1));
else if (Op0 == Op1I->getOperand(1)) // A^(B^A) == B
return ReplaceInstUsesWith(I, Op1I->getOperand(0));
} else if (Op1I->getOpcode() == Instruction::And && Op1I->hasOneUse()) {
if (Op1I->getOperand(0) == Op0) // A^(A&B) -> A^(B&A)
Op1I->swapOperands();
if (Op0 == Op1I->getOperand(1)) { // A^(B&A) -> (B&A)^A
I.swapOperands(); // Simplified below.
std::swap(Op0, Op1);
}
}
if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0))
if (Op0I->getOpcode() == Instruction::Or && Op0I->hasOneUse()) {
if (Op0I->getOperand(0) == Op1) // (B|A)^B == (A|B)^B
Op0I->swapOperands();
if (Op0I->getOperand(1) == Op1) { // (A|B)^B == A & ~B
Instruction *NotB = BinaryOperator::createNot(Op1, "tmp");
InsertNewInstBefore(NotB, I);
return BinaryOperator::createAnd(Op0I->getOperand(0), NotB);
}
} else if (Op0I->getOpcode() == Instruction::Xor) {
if (Op1 == Op0I->getOperand(0)) // (A^B)^A == B
return ReplaceInstUsesWith(I, Op0I->getOperand(1));
else if (Op1 == Op0I->getOperand(1)) // (B^A)^A == B
return ReplaceInstUsesWith(I, Op0I->getOperand(0));
} else if (Op0I->getOpcode() == Instruction::And && Op0I->hasOneUse()) {
if (Op0I->getOperand(0) == Op1) // (A&B)^A -> (B&A)^A
Op0I->swapOperands();
if (Op0I->getOperand(1) == Op1 && // (B&A)^A == ~B & A
!isa<ConstantInt>(Op1)) { // Canonical form is (B&C)^C
Instruction *N = BinaryOperator::createNot(Op0I->getOperand(0), "tmp");
InsertNewInstBefore(N, I);
return BinaryOperator::createAnd(N, Op1);
}
}
// (setcc1 A, B) ^ (setcc2 A, B) --> (setcc3 A, B)
if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
return R;
// fold (xor (cast A), (cast B)) -> (cast (xor A, B))
if (CastInst *Op0C = dyn_cast<CastInst>(Op0)) {
const Type *SrcTy = Op0C->getOperand(0)->getType();
if (CastInst *Op1C = dyn_cast<CastInst>(Op1))
if (SrcTy == Op1C->getOperand(0)->getType() && SrcTy->isIntegral() &&
// Only do this if the casts both really cause code to be generated.
ValueRequiresCast(Op0C->getOperand(0), I.getType(), TD) &&
ValueRequiresCast(Op1C->getOperand(0), I.getType(), TD)) {
Instruction *NewOp = BinaryOperator::createXor(Op0C->getOperand(0),
Op1C->getOperand(0),
I.getName());
InsertNewInstBefore(NewOp, I);
return new CastInst(NewOp, I.getType());
}
}
return Changed ? &I : 0;
}
static bool isPositive(ConstantInt *C) {
return C->getSExtValue() >= 0;
}
/// AddWithOverflow - Compute Result = In1+In2, returning true if the result
/// overflowed for this type.
static bool AddWithOverflow(ConstantInt *&Result, ConstantInt *In1,
ConstantInt *In2) {
Result = cast<ConstantInt>(ConstantExpr::getAdd(In1, In2));
if (In1->getType()->isUnsigned())
return cast<ConstantInt>(Result)->getZExtValue() <
cast<ConstantInt>(In1)->getZExtValue();
if (isPositive(In1) != isPositive(In2))
return false;
if (isPositive(In1))
return cast<ConstantInt>(Result)->getSExtValue() <
cast<ConstantInt>(In1)->getSExtValue();
return cast<ConstantInt>(Result)->getSExtValue() >
cast<ConstantInt>(In1)->getSExtValue();
}
/// EmitGEPOffset - Given a getelementptr instruction/constantexpr, emit the
/// code necessary to compute the offset from the base pointer (without adding
/// in the base pointer). Return the result as a signed integer of intptr size.
static Value *EmitGEPOffset(User *GEP, Instruction &I, InstCombiner &IC) {
TargetData &TD = IC.getTargetData();
gep_type_iterator GTI = gep_type_begin(GEP);
const Type *UIntPtrTy = TD.getIntPtrType();
const Type *SIntPtrTy = UIntPtrTy->getSignedVersion();
Value *Result = Constant::getNullValue(SIntPtrTy);
// Build a mask for high order bits.
uint64_t PtrSizeMask = ~0ULL >> (64-TD.getPointerSize()*8);
for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i, ++GTI) {
Value *Op = GEP->getOperand(i);
uint64_t Size = TD.getTypeSize(GTI.getIndexedType()) & PtrSizeMask;
Constant *Scale = ConstantExpr::getCast(ConstantInt::get(UIntPtrTy, Size),
SIntPtrTy);
if (Constant *OpC = dyn_cast<Constant>(Op)) {
if (!OpC->isNullValue()) {
OpC = ConstantExpr::getCast(OpC, SIntPtrTy);
Scale = ConstantExpr::getMul(OpC, Scale);
if (Constant *RC = dyn_cast<Constant>(Result))
Result = ConstantExpr::getAdd(RC, Scale);
else {
// Emit an add instruction.
Result = IC.InsertNewInstBefore(
BinaryOperator::createAdd(Result, Scale,
GEP->getName()+".offs"), I);
}
}
} else {
// Convert to correct type.
Op = IC.InsertNewInstBefore(new CastInst(Op, SIntPtrTy,
Op->getName()+".c"), I);
if (Size != 1)
// We'll let instcombine(mul) convert this to a shl if possible.
Op = IC.InsertNewInstBefore(BinaryOperator::createMul(Op, Scale,
GEP->getName()+".idx"), I);
// Emit an add instruction.
Result = IC.InsertNewInstBefore(BinaryOperator::createAdd(Op, Result,
GEP->getName()+".offs"), I);
}
}
return Result;
}
/// FoldGEPSetCC - Fold comparisons between a GEP instruction and something
/// else. At this point we know that the GEP is on the LHS of the comparison.
Instruction *InstCombiner::FoldGEPSetCC(User *GEPLHS, Value *RHS,
Instruction::BinaryOps Cond,
Instruction &I) {
assert(dyn_castGetElementPtr(GEPLHS) && "LHS is not a getelementptr!");
if (CastInst *CI = dyn_cast<CastInst>(RHS))
if (isa<PointerType>(CI->getOperand(0)->getType()))
RHS = CI->getOperand(0);
Value *PtrBase = GEPLHS->getOperand(0);
if (PtrBase == RHS) {
// As an optimization, we don't actually have to compute the actual value of
// OFFSET if this is a seteq or setne comparison, just return whether each
// index is zero or not.
if (Cond == Instruction::SetEQ || Cond == Instruction::SetNE) {
Instruction *InVal = 0;
gep_type_iterator GTI = gep_type_begin(GEPLHS);
for (unsigned i = 1, e = GEPLHS->getNumOperands(); i != e; ++i, ++GTI) {
bool EmitIt = true;
if (Constant *C = dyn_cast<Constant>(GEPLHS->getOperand(i))) {
if (isa<UndefValue>(C)) // undef index -> undef.
return ReplaceInstUsesWith(I, UndefValue::get(I.getType()));
if (C->isNullValue())
EmitIt = false;
else if (TD->getTypeSize(GTI.getIndexedType()) == 0) {
EmitIt = false; // This is indexing into a zero sized array?
} else if (isa<ConstantInt>(C))
return ReplaceInstUsesWith(I, // No comparison is needed here.
ConstantBool::get(Cond == Instruction::SetNE));
}
if (EmitIt) {
Instruction *Comp =
new SetCondInst(Cond, GEPLHS->getOperand(i),
Constant::getNullValue(GEPLHS->getOperand(i)->getType()));
if (InVal == 0)
InVal = Comp;
else {
InVal = InsertNewInstBefore(InVal, I);
InsertNewInstBefore(Comp, I);
if (Cond == Instruction::SetNE) // True if any are unequal
InVal = BinaryOperator::createOr(InVal, Comp);
else // True if all are equal
InVal = BinaryOperator::createAnd(InVal, Comp);
}
}
}
if (InVal)
return InVal;
else
ReplaceInstUsesWith(I, // No comparison is needed here, all indexes = 0
ConstantBool::get(Cond == Instruction::SetEQ));
}
// Only lower this if the setcc is the only user of the GEP or if we expect
// the result to fold to a constant!
if (isa<ConstantExpr>(GEPLHS) || GEPLHS->hasOneUse()) {
// ((gep Ptr, OFFSET) cmp Ptr) ---> (OFFSET cmp 0).
Value *Offset = EmitGEPOffset(GEPLHS, I, *this);
return new SetCondInst(Cond, Offset,
Constant::getNullValue(Offset->getType()));
}
} else if (User *GEPRHS = dyn_castGetElementPtr(RHS)) {
// If the base pointers are different, but the indices are the same, just
// compare the base pointer.
if (PtrBase != GEPRHS->getOperand(0)) {
bool IndicesTheSame = GEPLHS->getNumOperands()==GEPRHS->getNumOperands();
IndicesTheSame &= GEPLHS->getOperand(0)->getType() ==
GEPRHS->getOperand(0)->getType();
if (IndicesTheSame)
for (unsigned i = 1, e = GEPLHS->getNumOperands(); i != e; ++i)
if (GEPLHS->getOperand(i) != GEPRHS->getOperand(i)) {
IndicesTheSame = false;
break;
}
// If all indices are the same, just compare the base pointers.
if (IndicesTheSame)
return new SetCondInst(Cond, GEPLHS->getOperand(0),
GEPRHS->getOperand(0));
// Otherwise, the base pointers are different and the indices are
// different, bail out.
return 0;
}
// If one of the GEPs has all zero indices, recurse.
bool AllZeros = true;
for (unsigned i = 1, e = GEPLHS->getNumOperands(); i != e; ++i)
if (!isa<Constant>(GEPLHS->getOperand(i)) ||
!cast<Constant>(GEPLHS->getOperand(i))->isNullValue()) {
AllZeros = false;
break;
}
if (AllZeros)
return FoldGEPSetCC(GEPRHS, GEPLHS->getOperand(0),
SetCondInst::getSwappedCondition(Cond), I);
// If the other GEP has all zero indices, recurse.
AllZeros = true;
for (unsigned i = 1, e = GEPRHS->getNumOperands(); i != e; ++i)
if (!isa<Constant>(GEPRHS->getOperand(i)) ||
!cast<Constant>(GEPRHS->getOperand(i))->isNullValue()) {
AllZeros = false;
break;
}
if (AllZeros)
return FoldGEPSetCC(GEPLHS, GEPRHS->getOperand(0), Cond, I);
if (GEPLHS->getNumOperands() == GEPRHS->getNumOperands()) {
// If the GEPs only differ by one index, compare it.
unsigned NumDifferences = 0; // Keep track of # differences.
unsigned DiffOperand = 0; // The operand that differs.
for (unsigned i = 1, e = GEPRHS->getNumOperands(); i != e; ++i)
if (GEPLHS->getOperand(i) != GEPRHS->getOperand(i)) {
if (GEPLHS->getOperand(i)->getType()->getPrimitiveSizeInBits() !=
GEPRHS->getOperand(i)->getType()->getPrimitiveSizeInBits()) {
// Irreconcilable differences.
NumDifferences = 2;
break;
} else {
if (NumDifferences++) break;
DiffOperand = i;
}
}
if (NumDifferences == 0) // SAME GEP?
return ReplaceInstUsesWith(I, // No comparison is needed here.
ConstantBool::get(Cond == Instruction::SetEQ));
else if (NumDifferences == 1) {
Value *LHSV = GEPLHS->getOperand(DiffOperand);
Value *RHSV = GEPRHS->getOperand(DiffOperand);
// Convert the operands to signed values to make sure to perform a
// signed comparison.
const Type *NewTy = LHSV->getType()->getSignedVersion();
if (LHSV->getType() != NewTy)
LHSV = InsertCastBefore(LHSV, NewTy, I);
if (RHSV->getType() != NewTy)
RHSV = InsertCastBefore(RHSV, NewTy, I);
return new SetCondInst(Cond, LHSV, RHSV);
}
}
// Only lower this if the setcc is the only user of the GEP or if we expect
// the result to fold to a constant!
if ((isa<ConstantExpr>(GEPLHS) || GEPLHS->hasOneUse()) &&
(isa<ConstantExpr>(GEPRHS) || GEPRHS->hasOneUse())) {
// ((gep Ptr, OFFSET1) cmp (gep Ptr, OFFSET2) ---> (OFFSET1 cmp OFFSET2)
Value *L = EmitGEPOffset(GEPLHS, I, *this);
Value *R = EmitGEPOffset(GEPRHS, I, *this);
return new SetCondInst(Cond, L, R);
}
}
return 0;
}
Instruction *InstCombiner::visitSetCondInst(SetCondInst &I) {
bool Changed = SimplifyCommutative(I);
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
const Type *Ty = Op0->getType();
// setcc X, X
if (Op0 == Op1)
return ReplaceInstUsesWith(I, ConstantBool::get(isTrueWhenEqual(I)));
if (isa<UndefValue>(Op1)) // X setcc undef -> undef
return ReplaceInstUsesWith(I, UndefValue::get(Type::BoolTy));
// setcc <global/alloca*/null>, <global/alloca*/null> - Global/Stack value
// addresses never equal each other! We already know that Op0 != Op1.
if ((isa<GlobalValue>(Op0) || isa<AllocaInst>(Op0) ||
isa<ConstantPointerNull>(Op0)) &&
(isa<GlobalValue>(Op1) || isa<AllocaInst>(Op1) ||
isa<ConstantPointerNull>(Op1)))
return ReplaceInstUsesWith(I, ConstantBool::get(!isTrueWhenEqual(I)));
// setcc's with boolean values can always be turned into bitwise operations
if (Ty == Type::BoolTy) {
switch (I.getOpcode()) {
default: assert(0 && "Invalid setcc instruction!");
case Instruction::SetEQ: { // seteq bool %A, %B -> ~(A^B)
Instruction *Xor = BinaryOperator::createXor(Op0, Op1, I.getName()+"tmp");
InsertNewInstBefore(Xor, I);
return BinaryOperator::createNot(Xor);
}
case Instruction::SetNE:
return BinaryOperator::createXor(Op0, Op1);
case Instruction::SetGT:
std::swap(Op0, Op1); // Change setgt -> setlt
// FALL THROUGH
case Instruction::SetLT: { // setlt bool A, B -> ~X & Y
Instruction *Not = BinaryOperator::createNot(Op0, I.getName()+"tmp");
InsertNewInstBefore(Not, I);
return BinaryOperator::createAnd(Not, Op1);
}
case Instruction::SetGE:
std::swap(Op0, Op1); // Change setge -> setle
// FALL THROUGH
case Instruction::SetLE: { // setle bool %A, %B -> ~A | B
Instruction *Not = BinaryOperator::createNot(Op0, I.getName()+"tmp");
InsertNewInstBefore(Not, I);
return BinaryOperator::createOr(Not, Op1);
}
}
}
// See if we are doing a comparison between a constant and an instruction that
// can be folded into the comparison.
if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
// Check to see if we are comparing against the minimum or maximum value...
if (CI->isMinValue()) {
if (I.getOpcode() == Instruction::SetLT) // A < MIN -> FALSE
return ReplaceInstUsesWith(I, ConstantBool::getFalse());
if (I.getOpcode() == Instruction::SetGE) // A >= MIN -> TRUE
return ReplaceInstUsesWith(I, ConstantBool::getTrue());
if (I.getOpcode() == Instruction::SetLE) // A <= MIN -> A == MIN
return BinaryOperator::createSetEQ(Op0, Op1);
if (I.getOpcode() == Instruction::SetGT) // A > MIN -> A != MIN
return BinaryOperator::createSetNE(Op0, Op1);
} else if (CI->isMaxValue()) {
if (I.getOpcode() == Instruction::SetGT) // A > MAX -> FALSE
return ReplaceInstUsesWith(I, ConstantBool::getFalse());
if (I.getOpcode() == Instruction::SetLE) // A <= MAX -> TRUE
return ReplaceInstUsesWith(I, ConstantBool::getTrue());
if (I.getOpcode() == Instruction::SetGE) // A >= MAX -> A == MAX
return BinaryOperator::createSetEQ(Op0, Op1);
if (I.getOpcode() == Instruction::SetLT) // A < MAX -> A != MAX
return BinaryOperator::createSetNE(Op0, Op1);
// Comparing against a value really close to min or max?
} else if (isMinValuePlusOne(CI)) {
if (I.getOpcode() == Instruction::SetLT) // A < MIN+1 -> A == MIN
return BinaryOperator::createSetEQ(Op0, SubOne(CI));
if (I.getOpcode() == Instruction::SetGE) // A >= MIN-1 -> A != MIN
return BinaryOperator::createSetNE(Op0, SubOne(CI));
} else if (isMaxValueMinusOne(CI)) {
if (I.getOpcode() == Instruction::SetGT) // A > MAX-1 -> A == MAX
return BinaryOperator::createSetEQ(Op0, AddOne(CI));
if (I.getOpcode() == Instruction::SetLE) // A <= MAX-1 -> A != MAX
return BinaryOperator::createSetNE(Op0, AddOne(CI));
}
// If we still have a setle or setge instruction, turn it into the
// appropriate setlt or setgt instruction. Since the border cases have
// already been handled above, this requires little checking.
//
if (I.getOpcode() == Instruction::SetLE)
return BinaryOperator::createSetLT(Op0, AddOne(CI));
if (I.getOpcode() == Instruction::SetGE)
return BinaryOperator::createSetGT(Op0, SubOne(CI));
// See if we can fold the comparison based on bits known to be zero or one
// in the input.
uint64_t KnownZero, KnownOne;
if (SimplifyDemandedBits(Op0, Ty->getIntegralTypeMask(),
KnownZero, KnownOne, 0))
return &I;
// Given the known and unknown bits, compute a range that the LHS could be
// in.
if (KnownOne | KnownZero) {
if (Ty->isUnsigned()) { // Unsigned comparison.
uint64_t Min, Max;
uint64_t RHSVal = CI->getZExtValue();
ComputeUnsignedMinMaxValuesFromKnownBits(Ty, KnownZero, KnownOne,
Min, Max);
switch (I.getOpcode()) { // LE/GE have been folded already.
default: assert(0 && "Unknown setcc opcode!");
case Instruction::SetEQ:
if (Max < RHSVal || Min > RHSVal)
return ReplaceInstUsesWith(I, ConstantBool::getFalse());
break;
case Instruction::SetNE:
if (Max < RHSVal || Min > RHSVal)
return ReplaceInstUsesWith(I, ConstantBool::getTrue());
break;
case Instruction::SetLT:
if (Max < RHSVal)
return ReplaceInstUsesWith(I, ConstantBool::getTrue());
if (Min > RHSVal)
return ReplaceInstUsesWith(I, ConstantBool::getFalse());
break;
case Instruction::SetGT:
if (Min > RHSVal)
return ReplaceInstUsesWith(I, ConstantBool::getTrue());
if (Max < RHSVal)
return ReplaceInstUsesWith(I, ConstantBool::getFalse());
break;
}
} else { // Signed comparison.
int64_t Min, Max;
int64_t RHSVal = CI->getSExtValue();
ComputeSignedMinMaxValuesFromKnownBits(Ty, KnownZero, KnownOne,
Min, Max);
switch (I.getOpcode()) { // LE/GE have been folded already.
default: assert(0 && "Unknown setcc opcode!");
case Instruction::SetEQ:
if (Max < RHSVal || Min > RHSVal)
return ReplaceInstUsesWith(I, ConstantBool::getFalse());
break;
case Instruction::SetNE:
if (Max < RHSVal || Min > RHSVal)
return ReplaceInstUsesWith(I, ConstantBool::getTrue());
break;
case Instruction::SetLT:
if (Max < RHSVal)
return ReplaceInstUsesWith(I, ConstantBool::getTrue());
if (Min > RHSVal)
return ReplaceInstUsesWith(I, ConstantBool::getFalse());
break;
case Instruction::SetGT:
if (Min > RHSVal)
return ReplaceInstUsesWith(I, ConstantBool::getTrue());
if (Max < RHSVal)
return ReplaceInstUsesWith(I, ConstantBool::getFalse());
break;
}
}
}
// Since the RHS is a constantInt (CI), if the left hand side is an
// instruction, see if that instruction also has constants so that the
// instruction can be folded into the setcc
if (Instruction *LHSI = dyn_cast<Instruction>(Op0))
switch (LHSI->getOpcode()) {
case Instruction::And:
if (LHSI->hasOneUse() && isa<ConstantInt>(LHSI->getOperand(1)) &&
LHSI->getOperand(0)->hasOneUse()) {
ConstantInt *AndCST = cast<ConstantInt>(LHSI->getOperand(1));
// If an operand is an AND of a truncating cast, we can widen the
// and/compare to be the input width without changing the value
// produced, eliminating a cast.
if (CastInst *Cast = dyn_cast<CastInst>(LHSI->getOperand(0))) {
// We can do this transformation if either the AND constant does not
// have its sign bit set or if it is an equality comparison.
// Extending a relational comparison when we're checking the sign
// bit would not work.
if (Cast->hasOneUse() && Cast->isTruncIntCast() &&
(I.isEquality() ||
(AndCST->getZExtValue() == (uint64_t)AndCST->getSExtValue()) &&
(CI->getZExtValue() == (uint64_t)CI->getSExtValue()))) {
ConstantInt *NewCST;
ConstantInt *NewCI;
if (Cast->getOperand(0)->getType()->isSigned()) {
NewCST = ConstantInt::get(Cast->getOperand(0)->getType(),
AndCST->getZExtValue());
NewCI = ConstantInt::get(Cast->getOperand(0)->getType(),
CI->getZExtValue());
} else {
NewCST = ConstantInt::get(Cast->getOperand(0)->getType(),
AndCST->getZExtValue());
NewCI = ConstantInt::get(Cast->getOperand(0)->getType(),
CI->getZExtValue());
}
Instruction *NewAnd =
BinaryOperator::createAnd(Cast->getOperand(0), NewCST,
LHSI->getName());
InsertNewInstBefore(NewAnd, I);
return new SetCondInst(I.getOpcode(), NewAnd, NewCI);
}
}
// If this is: (X >> C1) & C2 != C3 (where any shift and any compare
// could exist), turn it into (X & (C2 << C1)) != (C3 << C1). This
// happens a LOT in code produced by the C front-end, for bitfield
// access.
ShiftInst *Shift = dyn_cast<ShiftInst>(LHSI->getOperand(0));
// Check to see if there is a noop-cast between the shift and the and.
if (!Shift) {
if (CastInst *CI = dyn_cast<CastInst>(LHSI->getOperand(0)))
if (CI->getOperand(0)->getType()->isIntegral() &&
CI->getOperand(0)->getType()->getPrimitiveSizeInBits() ==
CI->getType()->getPrimitiveSizeInBits())
Shift = dyn_cast<ShiftInst>(CI->getOperand(0));
}
ConstantInt *ShAmt;
ShAmt = Shift ? dyn_cast<ConstantInt>(Shift->getOperand(1)) : 0;
const Type *Ty = Shift ? Shift->getType() : 0; // Type of the shift.
const Type *AndTy = AndCST->getType(); // Type of the and.
// We can fold this as long as we can't shift unknown bits
// into the mask. This can only happen with signed shift
// rights, as they sign-extend.
if (ShAmt) {
bool CanFold = Shift->isLogicalShift();
if (!CanFold) {
// To test for the bad case of the signed shr, see if any
// of the bits shifted in could be tested after the mask.
int ShAmtVal = Ty->getPrimitiveSizeInBits()-ShAmt->getZExtValue();
if (ShAmtVal < 0) ShAmtVal = 0; // Out of range shift.
Constant *OShAmt = ConstantInt::get(Type::UByteTy, ShAmtVal);
Constant *ShVal =
ConstantExpr::getShl(ConstantInt::getAllOnesValue(AndTy),
OShAmt);
if (ConstantExpr::getAnd(ShVal, AndCST)->isNullValue())
CanFold = true;
}
if (CanFold) {
Constant *NewCst;
if (Shift->getOpcode() == Instruction::Shl)
NewCst = ConstantExpr::getLShr(CI, ShAmt);
else
NewCst = ConstantExpr::getShl(CI, ShAmt);
// Check to see if we are shifting out any of the bits being
// compared.
if (ConstantExpr::get(Shift->getOpcode(), NewCst, ShAmt) != CI){
// If we shifted bits out, the fold is not going to work out.
// As a special case, check to see if this means that the
// result is always true or false now.
if (I.getOpcode() == Instruction::SetEQ)
return ReplaceInstUsesWith(I, ConstantBool::getFalse());
if (I.getOpcode() == Instruction::SetNE)
return ReplaceInstUsesWith(I, ConstantBool::getTrue());
} else {
I.setOperand(1, NewCst);
Constant *NewAndCST;
if (Shift->getOpcode() == Instruction::Shl)
NewAndCST = ConstantExpr::getLShr(AndCST, ShAmt);
else
NewAndCST = ConstantExpr::getShl(AndCST, ShAmt);
LHSI->setOperand(1, NewAndCST);
if (AndTy == Ty)
LHSI->setOperand(0, Shift->getOperand(0));
else {
Value *NewCast = InsertCastBefore(Shift->getOperand(0), AndTy,
*Shift);
LHSI->setOperand(0, NewCast);
}
WorkList.push_back(Shift); // Shift is dead.
AddUsesToWorkList(I);
return &I;
}
}
}
// Turn ((X >> Y) & C) == 0 into (X & (C << Y)) == 0. The later is
// preferable because it allows the C<<Y expression to be hoisted out
// of a loop if Y is invariant and X is not.
if (Shift && Shift->hasOneUse() && CI->isNullValue() &&
I.isEquality() && !Shift->isArithmeticShift() &&
isa<Instruction>(Shift->getOperand(0))) {
// Compute C << Y.
Value *NS;
if (Shift->getOpcode() == Instruction::LShr) {
NS = new ShiftInst(Instruction::Shl, AndCST, Shift->getOperand(1),
"tmp");
} else {
// Make sure we insert a logical shift.
Constant *NewAndCST = AndCST;
if (AndCST->getType()->isSigned())
NewAndCST = ConstantExpr::getCast(AndCST,
AndCST->getType()->getUnsignedVersion());
NS = new ShiftInst(Instruction::LShr, NewAndCST,
Shift->getOperand(1), "tmp");
}
InsertNewInstBefore(cast<Instruction>(NS), I);
// If C's sign doesn't agree with the and, insert a cast now.
if (NS->getType() != LHSI->getType())
NS = InsertCastBefore(NS, LHSI->getType(), I);
Value *ShiftOp = Shift->getOperand(0);
if (ShiftOp->getType() != LHSI->getType())
ShiftOp = InsertCastBefore(ShiftOp, LHSI->getType(), I);
// Compute X & (C << Y).
Instruction *NewAnd =
BinaryOperator::createAnd(ShiftOp, NS, LHSI->getName());
InsertNewInstBefore(NewAnd, I);
I.setOperand(0, NewAnd);
return &I;
}
}
break;
case Instruction::Shl: // (setcc (shl X, ShAmt), CI)
if (ConstantInt *ShAmt = dyn_cast<ConstantInt>(LHSI->getOperand(1))) {
if (I.isEquality()) {
unsigned TypeBits = CI->getType()->getPrimitiveSizeInBits();
// Check that the shift amount is in range. If not, don't perform
// undefined shifts. When the shift is visited it will be
// simplified.
if (ShAmt->getZExtValue() >= TypeBits)
break;
// If we are comparing against bits always shifted out, the
// comparison cannot succeed.
Constant *Comp =
ConstantExpr::getShl(ConstantExpr::getLShr(CI, ShAmt), ShAmt);
if (Comp != CI) {// Comparing against a bit that we know is zero.
bool IsSetNE = I.getOpcode() == Instruction::SetNE;
Constant *Cst = ConstantBool::get(IsSetNE);
return ReplaceInstUsesWith(I, Cst);
}
if (LHSI->hasOneUse()) {
// Otherwise strength reduce the shift into an and.
unsigned ShAmtVal = (unsigned)ShAmt->getZExtValue();
uint64_t Val = (1ULL << (TypeBits-ShAmtVal))-1;
Constant *Mask;
if (CI->getType()->isUnsigned()) {
Mask = ConstantInt::get(CI->getType(), Val);
} else if (ShAmtVal != 0) {
Mask = ConstantInt::get(CI->getType(), Val);
} else {
Mask = ConstantInt::getAllOnesValue(CI->getType());
}
Instruction *AndI =
BinaryOperator::createAnd(LHSI->getOperand(0),
Mask, LHSI->getName()+".mask");
Value *And = InsertNewInstBefore(AndI, I);
return new SetCondInst(I.getOpcode(), And,
ConstantExpr::getLShr(CI, ShAmt));
}
}
}
break;
case Instruction::LShr: // (setcc (shr X, ShAmt), CI)
case Instruction::AShr:
if (ConstantInt *ShAmt = dyn_cast<ConstantInt>(LHSI->getOperand(1))) {
if (I.isEquality()) {
// Check that the shift amount is in range. If not, don't perform
// undefined shifts. When the shift is visited it will be
// simplified.
unsigned TypeBits = CI->getType()->getPrimitiveSizeInBits();
if (ShAmt->getZExtValue() >= TypeBits)
break;
// If we are comparing against bits always shifted out, the
// comparison cannot succeed.
Constant *Comp;
if (CI->getType()->isUnsigned())
Comp = ConstantExpr::getLShr(ConstantExpr::getShl(CI, ShAmt),
ShAmt);
else
Comp = ConstantExpr::getAShr(ConstantExpr::getShl(CI, ShAmt),
ShAmt);
if (Comp != CI) {// Comparing against a bit that we know is zero.
bool IsSetNE = I.getOpcode() == Instruction::SetNE;
Constant *Cst = ConstantBool::get(IsSetNE);
return ReplaceInstUsesWith(I, Cst);
}
if (LHSI->hasOneUse() || CI->isNullValue()) {
unsigned ShAmtVal = (unsigned)ShAmt->getZExtValue();
// Otherwise strength reduce the shift into an and.
uint64_t Val = ~0ULL; // All ones.
Val <<= ShAmtVal; // Shift over to the right spot.
Constant *Mask;
if (CI->getType()->isUnsigned()) {
Val &= ~0ULL >> (64-TypeBits);
Mask = ConstantInt::get(CI->getType(), Val);
} else {
Mask = ConstantInt::get(CI->getType(), Val);
}
Instruction *AndI =
BinaryOperator::createAnd(LHSI->getOperand(0),
Mask, LHSI->getName()+".mask");
Value *And = InsertNewInstBefore(AndI, I);
return new SetCondInst(I.getOpcode(), And,
ConstantExpr::getShl(CI, ShAmt));
}
}
}
break;
case Instruction::SDiv:
case Instruction::UDiv:
// Fold: setcc ([us]div X, C1), C2 -> range test
// Fold this div into the comparison, producing a range check.
// Determine, based on the divide type, what the range is being
// checked. If there is an overflow on the low or high side, remember
// it, otherwise compute the range [low, hi) bounding the new value.
// See: InsertRangeTest above for the kinds of replacements possible.
if (ConstantInt *DivRHS = dyn_cast<ConstantInt>(LHSI->getOperand(1))) {
// FIXME: If the operand types don't match the type of the divide
// then don't attempt this transform. The code below doesn't have the
// logic to deal with a signed divide and an unsigned compare (and
// vice versa). This is because (x /s C1) <s C2 produces different
// results than (x /s C1) <u C2 or (x /u C1) <s C2 or even
// (x /u C1) <u C2. Simply casting the operands and result won't
// work. :( The if statement below tests that condition and bails
// if it finds it.
const Type* DivRHSTy = DivRHS->getType();
unsigned DivOpCode = LHSI->getOpcode();
if (I.isEquality() &&
((DivOpCode == Instruction::SDiv && DivRHSTy->isUnsigned()) ||
(DivOpCode == Instruction::UDiv && DivRHSTy->isSigned())))
break;
// Initialize the variables that will indicate the nature of the
// range check.
bool LoOverflow = false, HiOverflow = false;
ConstantInt *LoBound = 0, *HiBound = 0;
// Compute Prod = CI * DivRHS. We are essentially solving an equation
// of form X/C1=C2. We solve for X by multiplying C1 (DivRHS) and
// C2 (CI). By solving for X we can turn this into a range check
// instead of computing a divide.
ConstantInt *Prod =
cast<ConstantInt>(ConstantExpr::getMul(CI, DivRHS));
// Determine if the product overflows by seeing if the product is
// not equal to the divide. Make sure we do the same kind of divide
// as in the LHS instruction that we're folding.
bool ProdOV = !DivRHS->isNullValue() &&
(DivOpCode == Instruction::SDiv ?
ConstantExpr::getSDiv(Prod, DivRHS) :
ConstantExpr::getUDiv(Prod, DivRHS)) != CI;
// Get the SetCC opcode
Instruction::BinaryOps Opcode = I.getOpcode();
if (DivRHS->isNullValue()) {
// Don't hack on divide by zeros!
} else if (DivOpCode == Instruction::UDiv) { // udiv
LoBound = Prod;
LoOverflow = ProdOV;
HiOverflow = ProdOV || AddWithOverflow(HiBound, LoBound, DivRHS);
} else if (isPositive(DivRHS)) { // Divisor is > 0.
if (CI->isNullValue()) { // (X / pos) op 0
// Can't overflow.
LoBound = cast<ConstantInt>(ConstantExpr::getNeg(SubOne(DivRHS)));
HiBound = DivRHS;
} else if (isPositive(CI)) { // (X / pos) op pos
LoBound = Prod;
LoOverflow = ProdOV;
HiOverflow = ProdOV || AddWithOverflow(HiBound, Prod, DivRHS);
} else { // (X / pos) op neg
Constant *DivRHSH = ConstantExpr::getNeg(SubOne(DivRHS));
LoOverflow = AddWithOverflow(LoBound, Prod,
cast<ConstantInt>(DivRHSH));
HiBound = Prod;
HiOverflow = ProdOV;
}
} else { // Divisor is < 0.
if (CI->isNullValue()) { // (X / neg) op 0
LoBound = AddOne(DivRHS);
HiBound = cast<ConstantInt>(ConstantExpr::getNeg(DivRHS));
if (HiBound == DivRHS)
LoBound = 0; // - INTMIN = INTMIN
} else if (isPositive(CI)) { // (X / neg) op pos
HiOverflow = LoOverflow = ProdOV;
if (!LoOverflow)
LoOverflow = AddWithOverflow(LoBound, Prod, AddOne(DivRHS));
HiBound = AddOne(Prod);
} else { // (X / neg) op neg
LoBound = Prod;
LoOverflow = HiOverflow = ProdOV;
HiBound = cast<ConstantInt>(ConstantExpr::getSub(Prod, DivRHS));
}
// Dividing by a negate swaps the condition.
Opcode = SetCondInst::getSwappedCondition(Opcode);
}
if (LoBound) {
Value *X = LHSI->getOperand(0);
switch (Opcode) {
default: assert(0 && "Unhandled setcc opcode!");
case Instruction::SetEQ:
if (LoOverflow && HiOverflow)
return ReplaceInstUsesWith(I, ConstantBool::getFalse());
else if (HiOverflow)
return new SetCondInst(Instruction::SetGE, X, LoBound);
else if (LoOverflow)
return new SetCondInst(Instruction::SetLT, X, HiBound);
else
return InsertRangeTest(X, LoBound, HiBound, true, I);
case Instruction::SetNE:
if (LoOverflow && HiOverflow)
return ReplaceInstUsesWith(I, ConstantBool::getTrue());
else if (HiOverflow)
return new SetCondInst(Instruction::SetLT, X, LoBound);
else if (LoOverflow)
return new SetCondInst(Instruction::SetGE, X, HiBound);
else
return InsertRangeTest(X, LoBound, HiBound, false, I);
case Instruction::SetLT:
if (LoOverflow)
return ReplaceInstUsesWith(I, ConstantBool::getFalse());
return new SetCondInst(Instruction::SetLT, X, LoBound);
case Instruction::SetGT:
if (HiOverflow)
return ReplaceInstUsesWith(I, ConstantBool::getFalse());
return new SetCondInst(Instruction::SetGE, X, HiBound);
}
}
}
break;
}
// Simplify seteq and setne instructions...
if (I.isEquality()) {
bool isSetNE = I.getOpcode() == Instruction::SetNE;
// If the first operand is (add|sub|and|or|xor|rem) with a constant, and
// the second operand is a constant, simplify a bit.
if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0)) {
switch (BO->getOpcode()) {
case Instruction::SRem:
// If we have a signed (X % (2^c)) == 0, turn it into an unsigned one.
if (CI->isNullValue() && isa<ConstantInt>(BO->getOperand(1)) &&
BO->hasOneUse()) {
int64_t V = cast<ConstantInt>(BO->getOperand(1))->getSExtValue();
if (V > 1 && isPowerOf2_64(V)) {
Value *NewRem = InsertNewInstBefore(BinaryOperator::createURem(
BO->getOperand(0), BO->getOperand(1), BO->getName()), I);
return BinaryOperator::create(I.getOpcode(), NewRem,
Constant::getNullValue(BO->getType()));
}
}
break;
case Instruction::Add:
// Replace ((add A, B) != C) with (A != C-B) if B & C are constants.
if (ConstantInt *BOp1C = dyn_cast<ConstantInt>(BO->getOperand(1))) {
if (BO->hasOneUse())
return new SetCondInst(I.getOpcode(), BO->getOperand(0),
ConstantExpr::getSub(CI, BOp1C));
} else if (CI->isNullValue()) {
// Replace ((add A, B) != 0) with (A != -B) if A or B is
// efficiently invertible, or if the add has just this one use.
Value *BOp0 = BO->getOperand(0), *BOp1 = BO->getOperand(1);
if (Value *NegVal = dyn_castNegVal(BOp1))
return new SetCondInst(I.getOpcode(), BOp0, NegVal);
else if (Value *NegVal = dyn_castNegVal(BOp0))
return new SetCondInst(I.getOpcode(), NegVal, BOp1);
else if (BO->hasOneUse()) {
Instruction *Neg = BinaryOperator::createNeg(BOp1, BO->getName());
BO->setName("");
InsertNewInstBefore(Neg, I);
return new SetCondInst(I.getOpcode(), BOp0, Neg);
}
}
break;
case Instruction::Xor:
// For the xor case, we can xor two constants together, eliminating
// the explicit xor.
if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1)))
return BinaryOperator::create(I.getOpcode(), BO->getOperand(0),
ConstantExpr::getXor(CI, BOC));
// FALLTHROUGH
case Instruction::Sub:
// Replace (([sub|xor] A, B) != 0) with (A != B)
if (CI->isNullValue())
return new SetCondInst(I.getOpcode(), BO->getOperand(0),
BO->getOperand(1));
break;
case Instruction::Or:
// If bits are being or'd in that are not present in the constant we
// are comparing against, then the comparison could never succeed!
if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1))) {
Constant *NotCI = ConstantExpr::getNot(CI);
if (!ConstantExpr::getAnd(BOC, NotCI)->isNullValue())
return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
}
break;
case Instruction::And:
if (ConstantInt *BOC = dyn_cast<ConstantInt>(BO->getOperand(1))) {
// If bits are being compared against that are and'd out, then the
// comparison can never succeed!
if (!ConstantExpr::getAnd(CI,
ConstantExpr::getNot(BOC))->isNullValue())
return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
// If we have ((X & C) == C), turn it into ((X & C) != 0).
if (CI == BOC && isOneBitSet(CI))
return new SetCondInst(isSetNE ? Instruction::SetEQ :
Instruction::SetNE, Op0,
Constant::getNullValue(CI->getType()));
// Replace (and X, (1 << size(X)-1) != 0) with x < 0, converting X
// to be a signed value as appropriate.
if (isSignBit(BOC)) {
Value *X = BO->getOperand(0);
// If 'X' is not signed, insert a cast now...
if (!BOC->getType()->isSigned()) {
const Type *DestTy = BOC->getType()->getSignedVersion();
X = InsertCastBefore(X, DestTy, I);
}
return new SetCondInst(isSetNE ? Instruction::SetLT :
Instruction::SetGE, X,
Constant::getNullValue(X->getType()));
}
// ((X & ~7) == 0) --> X < 8
if (CI->isNullValue() && isHighOnes(BOC)) {
Value *X = BO->getOperand(0);
Constant *NegX = ConstantExpr::getNeg(BOC);
// If 'X' is signed, insert a cast now.
if (NegX->getType()->isSigned()) {
const Type *DestTy = NegX->getType()->getUnsignedVersion();
X = InsertCastBefore(X, DestTy, I);
NegX = ConstantExpr::getCast(NegX, DestTy);
}
return new SetCondInst(isSetNE ? Instruction::SetGE :
Instruction::SetLT, X, NegX);
}
}
default: break;
}
}
} else { // Not a SetEQ/SetNE
// If the LHS is a cast from an integral value of the same size,
if (CastInst *Cast = dyn_cast<CastInst>(Op0)) {
Value *CastOp = Cast->getOperand(0);
const Type *SrcTy = CastOp->getType();
unsigned SrcTySize = SrcTy->getPrimitiveSizeInBits();
if (SrcTy != Cast->getType() && SrcTy->isInteger() &&
SrcTySize == Cast->getType()->getPrimitiveSizeInBits()) {
assert((SrcTy->isSigned() ^ Cast->getType()->isSigned()) &&
"Source and destination signednesses should differ!");
if (Cast->getType()->isSigned()) {
// If this is a signed comparison, check for comparisons in the
// vicinity of zero.
if (I.getOpcode() == Instruction::SetLT && CI->isNullValue())
// X < 0 => x > 127
return BinaryOperator::createSetGT(CastOp,
ConstantInt::get(SrcTy, (1ULL << (SrcTySize-1))-1));
else if (I.getOpcode() == Instruction::SetGT &&
cast<ConstantInt>(CI)->getSExtValue() == -1)
// X > -1 => x < 128
return BinaryOperator::createSetLT(CastOp,
ConstantInt::get(SrcTy, 1ULL << (SrcTySize-1)));
} else {
ConstantInt *CUI = cast<ConstantInt>(CI);
if (I.getOpcode() == Instruction::SetLT &&
CUI->getZExtValue() == 1ULL << (SrcTySize-1))
// X < 128 => X > -1
return BinaryOperator::createSetGT(CastOp,
ConstantInt::get(SrcTy, -1));
else if (I.getOpcode() == Instruction::SetGT &&
CUI->getZExtValue() == (1ULL << (SrcTySize-1))-1)
// X > 127 => X < 0
return BinaryOperator::createSetLT(CastOp,
Constant::getNullValue(SrcTy));
}
}
}
}
}
// Handle setcc with constant RHS's that can be integer, FP or pointer.
if (Constant *RHSC = dyn_cast<Constant>(Op1)) {
if (Instruction *LHSI = dyn_cast<Instruction>(Op0))
switch (LHSI->getOpcode()) {
case Instruction::GetElementPtr:
if (RHSC->isNullValue()) {
// Transform setcc GEP P, int 0, int 0, int 0, null -> setcc P, null
bool isAllZeros = true;
for (unsigned i = 1, e = LHSI->getNumOperands(); i != e; ++i)
if (!isa<Constant>(LHSI->getOperand(i)) ||
!cast<Constant>(LHSI->getOperand(i))->isNullValue()) {
isAllZeros = false;
break;
}
if (isAllZeros)
return new SetCondInst(I.getOpcode(), LHSI->getOperand(0),
Constant::getNullValue(LHSI->getOperand(0)->getType()));
}
break;
case Instruction::PHI:
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
break;
case Instruction::Select:
// If either operand of the select is a constant, we can fold the
// comparison into the select arms, which will cause one to be
// constant folded and the select turned into a bitwise or.
Value *Op1 = 0, *Op2 = 0;
if (LHSI->hasOneUse()) {
if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(1))) {
// Fold the known value into the constant operand.
Op1 = ConstantExpr::get(I.getOpcode(), C, RHSC);
// Insert a new SetCC of the other select operand.
Op2 = InsertNewInstBefore(new SetCondInst(I.getOpcode(),
LHSI->getOperand(2), RHSC,
I.getName()), I);
} else if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(2))) {
// Fold the known value into the constant operand.
Op2 = ConstantExpr::get(I.getOpcode(), C, RHSC);
// Insert a new SetCC of the other select operand.
Op1 = InsertNewInstBefore(new SetCondInst(I.getOpcode(),
LHSI->getOperand(1), RHSC,
I.getName()), I);
}
}
if (Op1)
return new SelectInst(LHSI->getOperand(0), Op1, Op2);
break;
}
}
// If we can optimize a 'setcc GEP, P' or 'setcc P, GEP', do so now.
if (User *GEP = dyn_castGetElementPtr(Op0))
if (Instruction *NI = FoldGEPSetCC(GEP, Op1, I.getOpcode(), I))
return NI;
if (User *GEP = dyn_castGetElementPtr(Op1))
if (Instruction *NI = FoldGEPSetCC(GEP, Op0,
SetCondInst::getSwappedCondition(I.getOpcode()), I))
return NI;
// Test to see if the operands of the setcc are casted versions of other
// values. If the cast can be stripped off both arguments, we do so now.
if (CastInst *CI = dyn_cast<CastInst>(Op0)) {
Value *CastOp0 = CI->getOperand(0);
if (CastOp0->getType()->isLosslesslyConvertibleTo(CI->getType()) &&
(isa<Constant>(Op1) || isa<CastInst>(Op1)) && I.isEquality()) {
// We keep moving the cast from the left operand over to the right
// operand, where it can often be eliminated completely.
Op0 = CastOp0;
// If operand #1 is a cast instruction, see if we can eliminate it as
// well.
if (CastInst *CI2 = dyn_cast<CastInst>(Op1))
if (CI2->getOperand(0)->getType()->isLosslesslyConvertibleTo(
Op0->getType()))
Op1 = CI2->getOperand(0);
// If Op1 is a constant, we can fold the cast into the constant.
if (Op1->getType() != Op0->getType())
if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
Op1 = ConstantExpr::getCast(Op1C, Op0->getType());
} else {
// Otherwise, cast the RHS right before the setcc
Op1 = InsertCastBefore(Op1, Op0->getType(), I);
}
return BinaryOperator::create(I.getOpcode(), Op0, Op1);
}
// Handle the special case of: setcc (cast bool to X), <cst>
// This comes up when you have code like
// int X = A < B;
// if (X) ...
// For generality, we handle any zero-extension of any operand comparison
// with a constant or another cast from the same type.
if (isa<ConstantInt>(Op1) || isa<CastInst>(Op1))
if (Instruction *R = visitSetCondInstWithCastAndCast(I))
return R;
}
if (I.isEquality()) {
Value *A, *B;
if (match(Op0, m_Xor(m_Value(A), m_Value(B))) &&
(A == Op1 || B == Op1)) {
// (A^B) == A -> B == 0
Value *OtherVal = A == Op1 ? B : A;
return BinaryOperator::create(I.getOpcode(), OtherVal,
Constant::getNullValue(A->getType()));
} else if (match(Op1, m_Xor(m_Value(A), m_Value(B))) &&
(A == Op0 || B == Op0)) {
// A == (A^B) -> B == 0
Value *OtherVal = A == Op0 ? B : A;
return BinaryOperator::create(I.getOpcode(), OtherVal,
Constant::getNullValue(A->getType()));
} else if (match(Op0, m_Sub(m_Value(A), m_Value(B))) && A == Op1) {
// (A-B) == A -> B == 0
return BinaryOperator::create(I.getOpcode(), B,
Constant::getNullValue(B->getType()));
} else if (match(Op1, m_Sub(m_Value(A), m_Value(B))) && A == Op0) {
// A == (A-B) -> B == 0
return BinaryOperator::create(I.getOpcode(), B,
Constant::getNullValue(B->getType()));
}
}
return Changed ? &I : 0;
}
// visitSetCondInstWithCastAndCast - Handle setcond (cast x to y), (cast/cst).
// We only handle extending casts so far.
//
Instruction *InstCombiner::visitSetCondInstWithCastAndCast(SetCondInst &SCI) {
Value *LHSCIOp = cast<CastInst>(SCI.getOperand(0))->getOperand(0);
const Type *SrcTy = LHSCIOp->getType();
const Type *DestTy = SCI.getOperand(0)->getType();
Value *RHSCIOp;
if (!DestTy->isIntegral() || !SrcTy->isIntegral())
return 0;
unsigned SrcBits = SrcTy->getPrimitiveSizeInBits();
unsigned DestBits = DestTy->getPrimitiveSizeInBits();
if (SrcBits >= DestBits) return 0; // Only handle extending cast.
// Is this a sign or zero extension?
bool isSignSrc = SrcTy->isSigned();
bool isSignDest = DestTy->isSigned();
if (CastInst *CI = dyn_cast<CastInst>(SCI.getOperand(1))) {
// Not an extension from the same type?
RHSCIOp = CI->getOperand(0);
if (RHSCIOp->getType() != LHSCIOp->getType()) return 0;
} else if (ConstantInt *CI = dyn_cast<ConstantInt>(SCI.getOperand(1))) {
// Compute the constant that would happen if we truncated to SrcTy then
// reextended to DestTy.
Constant *Res = ConstantExpr::getCast(CI, SrcTy);
if (ConstantExpr::getCast(Res, DestTy) == CI) {
// Make sure that src sign and dest sign match. For example,
//
// %A = cast short %X to uint
// %B = setgt uint %A, 1330
//
// It is incorrect to transform this into
//
// %B = setgt short %X, 1330
//
// because %A may have negative value.
// However, it is OK if SrcTy is bool (See cast-set.ll testcase)
// OR operation is EQ/NE.
if (isSignSrc == isSignDest || SrcTy == Type::BoolTy || SCI.isEquality())
RHSCIOp = Res;
else
return 0;
} else {
// If the value cannot be represented in the shorter type, we cannot emit
// a simple comparison.
if (SCI.getOpcode() == Instruction::SetEQ)
return ReplaceInstUsesWith(SCI, ConstantBool::getFalse());
if (SCI.getOpcode() == Instruction::SetNE)
return ReplaceInstUsesWith(SCI, ConstantBool::getTrue());
// Evaluate the comparison for LT.
Value *Result;
if (DestTy->isSigned()) {
// We're performing a signed comparison.
if (isSignSrc) {
// Signed extend and signed comparison.
if (cast<ConstantInt>(CI)->getSExtValue() < 0)// X < (small) --> false
Result = ConstantBool::getFalse();
else
Result = ConstantBool::getTrue(); // X < (large) --> true
} else {
// Unsigned extend and signed comparison.
if (cast<ConstantInt>(CI)->getSExtValue() < 0)
Result = ConstantBool::getFalse();
else
Result = ConstantBool::getTrue();
}
} else {
// We're performing an unsigned comparison.
if (!isSignSrc) {
// Unsigned extend & compare -> always true.
Result = ConstantBool::getTrue();
} else {
// We're performing an unsigned comp with a sign extended value.
// This is true if the input is >= 0. [aka >s -1]
Constant *NegOne = ConstantIntegral::getAllOnesValue(SrcTy);
Result = InsertNewInstBefore(BinaryOperator::createSetGT(LHSCIOp,
NegOne, SCI.getName()), SCI);
}
}
// Finally, return the value computed.
if (SCI.getOpcode() == Instruction::SetLT) {
return ReplaceInstUsesWith(SCI, Result);
} else {
assert(SCI.getOpcode()==Instruction::SetGT &&"SetCC should be folded!");
if (Constant *CI = dyn_cast<Constant>(Result))
return ReplaceInstUsesWith(SCI, ConstantExpr::getNot(CI));
else
return BinaryOperator::createNot(Result);
}
}
} else {
return 0;
}
// Okay, just insert a compare of the reduced operands now!
return BinaryOperator::create(SCI.getOpcode(), LHSCIOp, RHSCIOp);
}
Instruction *InstCombiner::visitShiftInst(ShiftInst &I) {
assert(I.getOperand(1)->getType() == Type::UByteTy);
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
bool isLeftShift = I.getOpcode() == Instruction::Shl;
// shl X, 0 == X and shr X, 0 == X
// shl 0, X == 0 and shr 0, X == 0
if (Op1 == Constant::getNullValue(Type::UByteTy) ||
Op0 == Constant::getNullValue(Op0->getType()))
return ReplaceInstUsesWith(I, Op0);
if (isa<UndefValue>(Op0)) { // undef >>s X -> undef
if (!isLeftShift && I.getType()->isSigned())
return ReplaceInstUsesWith(I, Op0);
else // undef << X -> 0 AND undef >>u X -> 0
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
}
if (isa<UndefValue>(Op1)) {
if (isLeftShift || I.getType()->isUnsigned())// X << undef, X >>u undef -> 0
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
else
return ReplaceInstUsesWith(I, Op0); // X >>s undef -> X
}
// shr int -1, X = -1 (for any arithmetic shift rights of ~0)
if (!isLeftShift)
if (ConstantInt *CSI = dyn_cast<ConstantInt>(Op0))
if (CSI->isAllOnesValue() && Op0->getType()->isSigned())
return ReplaceInstUsesWith(I, CSI);
// Try to fold constant and into select arguments.
if (isa<Constant>(Op0))
if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
if (Instruction *R = FoldOpIntoSelect(I, SI, this))
return R;
// See if we can turn a signed shr into an unsigned shr.
if (I.isArithmeticShift()) {
if (MaskedValueIsZero(Op0,
1ULL << (I.getType()->getPrimitiveSizeInBits()-1))) {
return new ShiftInst(Instruction::LShr, Op0, Op1, I.getName());
}
}
if (ConstantInt *CUI = dyn_cast<ConstantInt>(Op1))
if (CUI->getType()->isUnsigned())
if (Instruction *Res = FoldShiftByConstant(Op0, CUI, I))
return Res;
return 0;
}
Instruction *InstCombiner::FoldShiftByConstant(Value *Op0, ConstantInt *Op1,
ShiftInst &I) {
bool isLeftShift = I.getOpcode() == Instruction::Shl;
bool isSignedShift = isLeftShift ? Op0->getType()->isSigned() :
I.getOpcode() == Instruction::AShr;
bool isUnsignedShift = !isSignedShift;
// See if we can simplify any instructions used by the instruction whose sole
// purpose is to compute bits we don't care about.
uint64_t KnownZero, KnownOne;
if (SimplifyDemandedBits(&I, I.getType()->getIntegralTypeMask(),
KnownZero, KnownOne))
return &I;
// shl uint X, 32 = 0 and shr ubyte Y, 9 = 0, ... just don't eliminate shr
// of a signed value.
//
unsigned TypeBits = Op0->getType()->getPrimitiveSizeInBits();
if (Op1->getZExtValue() >= TypeBits) {
if (isUnsignedShift || isLeftShift)
return ReplaceInstUsesWith(I, Constant::getNullValue(Op0->getType()));
else {
I.setOperand(1, ConstantInt::get(Type::UByteTy, TypeBits-1));
return &I;
}
}
// ((X*C1) << C2) == (X * (C1 << C2))
if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0))
if (BO->getOpcode() == Instruction::Mul && isLeftShift)
if (Constant *BOOp = dyn_cast<Constant>(BO->getOperand(1)))
return BinaryOperator::createMul(BO->getOperand(0),
ConstantExpr::getShl(BOOp, Op1));
// Try to fold constant and into select arguments.
if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
if (Instruction *R = FoldOpIntoSelect(I, SI, this))
return R;
if (isa<PHINode>(Op0))
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
if (Op0->hasOneUse()) {
if (BinaryOperator *Op0BO = dyn_cast<BinaryOperator>(Op0)) {
// Turn ((X >> C) + Y) << C -> (X + (Y << C)) & (~0 << C)
Value *V1, *V2;
ConstantInt *CC;
switch (Op0BO->getOpcode()) {
default: break;
case Instruction::Add:
case Instruction::And:
case Instruction::Or:
case Instruction::Xor:
// These operators commute.
// Turn (Y + (X >> C)) << C -> (X + (Y << C)) & (~0 << C)
if (isLeftShift && Op0BO->getOperand(1)->hasOneUse() &&
match(Op0BO->getOperand(1),
m_Shr(m_Value(V1), m_ConstantInt(CC))) && CC == Op1) {
Instruction *YS = new ShiftInst(Instruction::Shl,
Op0BO->getOperand(0), Op1,
Op0BO->getName());
InsertNewInstBefore(YS, I); // (Y << C)
Instruction *X =
BinaryOperator::create(Op0BO->getOpcode(), YS, V1,
Op0BO->getOperand(1)->getName());
InsertNewInstBefore(X, I); // (X + (Y << C))
Constant *C2 = ConstantInt::getAllOnesValue(X->getType());
C2 = ConstantExpr::getShl(C2, Op1);
return BinaryOperator::createAnd(X, C2);
}
// Turn (Y + ((X >> C) & CC)) << C -> ((X & (CC << C)) + (Y << C))
if (isLeftShift && Op0BO->getOperand(1)->hasOneUse() &&
match(Op0BO->getOperand(1),
m_And(m_Shr(m_Value(V1), m_Value(V2)),
m_ConstantInt(CC))) && V2 == Op1 &&
cast<BinaryOperator>(Op0BO->getOperand(1))->getOperand(0)->hasOneUse()) {
Instruction *YS = new ShiftInst(Instruction::Shl,
Op0BO->getOperand(0), Op1,
Op0BO->getName());
InsertNewInstBefore(YS, I); // (Y << C)
Instruction *XM =
BinaryOperator::createAnd(V1, ConstantExpr::getShl(CC, Op1),
V1->getName()+".mask");
InsertNewInstBefore(XM, I); // X & (CC << C)
return BinaryOperator::create(Op0BO->getOpcode(), YS, XM);
}
// FALL THROUGH.
case Instruction::Sub:
// Turn ((X >> C) + Y) << C -> (X + (Y << C)) & (~0 << C)
if (isLeftShift && Op0BO->getOperand(0)->hasOneUse() &&
match(Op0BO->getOperand(0),
m_Shr(m_Value(V1), m_ConstantInt(CC))) && CC == Op1) {
Instruction *YS = new ShiftInst(Instruction::Shl,
Op0BO->getOperand(1), Op1,
Op0BO->getName());
InsertNewInstBefore(YS, I); // (Y << C)
Instruction *X =
BinaryOperator::create(Op0BO->getOpcode(), V1, YS,
Op0BO->getOperand(0)->getName());
InsertNewInstBefore(X, I); // (X + (Y << C))
Constant *C2 = ConstantInt::getAllOnesValue(X->getType());
C2 = ConstantExpr::getShl(C2, Op1);
return BinaryOperator::createAnd(X, C2);
}
// Turn (((X >> C)&CC) + Y) << C -> (X + (Y << C)) & (CC << C)
if (isLeftShift && Op0BO->getOperand(0)->hasOneUse() &&
match(Op0BO->getOperand(0),
m_And(m_Shr(m_Value(V1), m_Value(V2)),
m_ConstantInt(CC))) && V2 == Op1 &&
cast<BinaryOperator>(Op0BO->getOperand(0))
->getOperand(0)->hasOneUse()) {
Instruction *YS = new ShiftInst(Instruction::Shl,
Op0BO->getOperand(1), Op1,
Op0BO->getName());
InsertNewInstBefore(YS, I); // (Y << C)
Instruction *XM =
BinaryOperator::createAnd(V1, ConstantExpr::getShl(CC, Op1),
V1->getName()+".mask");
InsertNewInstBefore(XM, I); // X & (CC << C)
return BinaryOperator::create(Op0BO->getOpcode(), XM, YS);
}
break;
}
// If the operand is an bitwise operator with a constant RHS, and the
// shift is the only use, we can pull it out of the shift.
if (ConstantInt *Op0C = dyn_cast<ConstantInt>(Op0BO->getOperand(1))) {
bool isValid = true; // Valid only for And, Or, Xor
bool highBitSet = false; // Transform if high bit of constant set?
switch (Op0BO->getOpcode()) {
default: isValid = false; break; // Do not perform transform!
case Instruction::Add:
isValid = isLeftShift;
break;
case Instruction::Or:
case Instruction::Xor:
highBitSet = false;
break;
case Instruction::And:
highBitSet = true;
break;
}
// If this is a signed shift right, and the high bit is modified
// by the logical operation, do not perform the transformation.
// The highBitSet boolean indicates the value of the high bit of
// the constant which would cause it to be modified for this
// operation.
//
if (isValid && !isLeftShift && isSignedShift) {
uint64_t Val = Op0C->getZExtValue();
isValid = ((Val & (1 << (TypeBits-1))) != 0) == highBitSet;
}
if (isValid) {
Constant *NewRHS = ConstantExpr::get(I.getOpcode(), Op0C, Op1);
Instruction *NewShift =
new ShiftInst(I.getOpcode(), Op0BO->getOperand(0), Op1,
Op0BO->getName());
Op0BO->setName("");
InsertNewInstBefore(NewShift, I);
return BinaryOperator::create(Op0BO->getOpcode(), NewShift,
NewRHS);
}
}
}
}
// Find out if this is a shift of a shift by a constant.
ShiftInst *ShiftOp = 0;
if (ShiftInst *Op0SI = dyn_cast<ShiftInst>(Op0))
ShiftOp = Op0SI;
else if (CastInst *CI = dyn_cast<CastInst>(Op0)) {
// If this is a noop-integer case of a shift instruction, use the shift.
if (CI->getOperand(0)->getType()->isInteger() &&
CI->getOperand(0)->getType()->getPrimitiveSizeInBits() ==
CI->getType()->getPrimitiveSizeInBits() &&
isa<ShiftInst>(CI->getOperand(0))) {
ShiftOp = cast<ShiftInst>(CI->getOperand(0));
}
}
if (ShiftOp && isa<ConstantInt>(ShiftOp->getOperand(1))) {
// Find the operands and properties of the input shift. Note that the
// signedness of the input shift may differ from the current shift if there
// is a noop cast between the two.
bool isShiftOfLeftShift = ShiftOp->getOpcode() == Instruction::Shl;
bool isShiftOfSignedShift = isShiftOfLeftShift ?
ShiftOp->getType()->isSigned() :
ShiftOp->getOpcode() == Instruction::AShr;
bool isShiftOfUnsignedShift = !isShiftOfSignedShift;
ConstantInt *ShiftAmt1C = cast<ConstantInt>(ShiftOp->getOperand(1));
unsigned ShiftAmt1 = (unsigned)ShiftAmt1C->getZExtValue();
unsigned ShiftAmt2 = (unsigned)Op1->getZExtValue();
// Check for (A << c1) << c2 and (A >> c1) >> c2.
if (isLeftShift == isShiftOfLeftShift) {
// Do not fold these shifts if the first one is signed and the second one
// is unsigned and this is a right shift. Further, don't do any folding
// on them.
if (isShiftOfSignedShift && isUnsignedShift && !isLeftShift)
return 0;
unsigned Amt = ShiftAmt1+ShiftAmt2; // Fold into one big shift.
if (Amt > Op0->getType()->getPrimitiveSizeInBits())
Amt = Op0->getType()->getPrimitiveSizeInBits();
Value *Op = ShiftOp->getOperand(0);
if (isShiftOfSignedShift != isSignedShift)
Op = InsertNewInstBefore(new CastInst(Op, I.getType(), "tmp"), I);
ShiftInst* ShiftResult = new ShiftInst(I.getOpcode(), Op,
ConstantInt::get(Type::UByteTy, Amt));
if (I.getType() == ShiftResult->getType())
return ShiftResult;
InsertNewInstBefore(ShiftResult, I);
return new CastInst(ShiftResult, I.getType());
}
// Check for (A << c1) >> c2 or (A >> c1) << c2. If we are dealing with
// signed types, we can only support the (A >> c1) << c2 configuration,
// because it can not turn an arbitrary bit of A into a sign bit.
if (isUnsignedShift || isLeftShift) {
// Calculate bitmask for what gets shifted off the edge.
Constant *C = ConstantIntegral::getAllOnesValue(I.getType());
if (isLeftShift)
C = ConstantExpr::getShl(C, ShiftAmt1C);
else
C = ConstantExpr::getLShr(C, ShiftAmt1C);
Value *Op = ShiftOp->getOperand(0);
if (Op->getType() != C->getType())
Op = InsertCastBefore(Op, I.getType(), I);
Instruction *Mask =
BinaryOperator::createAnd(Op, C, Op->getName()+".mask");
InsertNewInstBefore(Mask, I);
// Figure out what flavor of shift we should use...
if (ShiftAmt1 == ShiftAmt2) {
return ReplaceInstUsesWith(I, Mask); // (A << c) >> c === A & c2
} else if (ShiftAmt1 < ShiftAmt2) {
return new ShiftInst(I.getOpcode(), Mask,
ConstantInt::get(Type::UByteTy, ShiftAmt2-ShiftAmt1));
} else if (isShiftOfUnsignedShift || isShiftOfLeftShift) {
if (isShiftOfUnsignedShift && !isShiftOfLeftShift && isSignedShift) {
return new ShiftInst(Instruction::LShr, Mask,
ConstantInt::get(Type::UByteTy, ShiftAmt1-ShiftAmt2));
} else {
return new ShiftInst(ShiftOp->getOpcode(), Mask,
ConstantInt::get(Type::UByteTy, ShiftAmt1-ShiftAmt2));
}
} else {
// (X >>s C1) << C2 where C1 > C2 === (X >>s (C1-C2)) & mask
Op = InsertCastBefore(Mask, I.getType()->getSignedVersion(), I);
Instruction *Shift =
new ShiftInst(ShiftOp->getOpcode(), Op,
ConstantInt::get(Type::UByteTy, ShiftAmt1-ShiftAmt2));
InsertNewInstBefore(Shift, I);
C = ConstantIntegral::getAllOnesValue(Shift->getType());
C = ConstantExpr::getShl(C, Op1);
Mask = BinaryOperator::createAnd(Shift, C, Op->getName()+".mask");
InsertNewInstBefore(Mask, I);
return new CastInst(Mask, I.getType());
}
} else {
// We can handle signed (X << C1) >>s C2 if it's a sign extend. In
// this case, C1 == C2 and C1 is 8, 16, or 32.
if (ShiftAmt1 == ShiftAmt2) {
const Type *SExtType = 0;
switch (Op0->getType()->getPrimitiveSizeInBits() - ShiftAmt1) {
case 8 : SExtType = Type::SByteTy; break;
case 16: SExtType = Type::ShortTy; break;
case 32: SExtType = Type::IntTy; break;
}
if (SExtType) {
Instruction *NewTrunc = new CastInst(ShiftOp->getOperand(0),
SExtType, "sext");
InsertNewInstBefore(NewTrunc, I);
return new CastInst(NewTrunc, I.getType());
}
}
}
}
return 0;
}
/// DecomposeSimpleLinearExpr - Analyze 'Val', seeing if it is a simple linear
/// expression. If so, decompose it, returning some value X, such that Val is
/// X*Scale+Offset.
///
static Value *DecomposeSimpleLinearExpr(Value *Val, unsigned &Scale,
unsigned &Offset) {
assert(Val->getType() == Type::UIntTy && "Unexpected allocation size type!");
if (ConstantInt *CI = dyn_cast<ConstantInt>(Val)) {
if (CI->getType()->isUnsigned()) {
Offset = CI->getZExtValue();
Scale = 1;
return ConstantInt::get(Type::UIntTy, 0);
}
} else if (Instruction *I = dyn_cast<Instruction>(Val)) {
if (I->getNumOperands() == 2) {
if (ConstantInt *CUI = dyn_cast<ConstantInt>(I->getOperand(1))) {
if (CUI->getType()->isUnsigned()) {
if (I->getOpcode() == Instruction::Shl) {
// This is a value scaled by '1 << the shift amt'.
Scale = 1U << CUI->getZExtValue();
Offset = 0;
return I->getOperand(0);
} else if (I->getOpcode() == Instruction::Mul) {
// This value is scaled by 'CUI'.
Scale = CUI->getZExtValue();
Offset = 0;
return I->getOperand(0);
} else if (I->getOpcode() == Instruction::Add) {
// We have X+C. Check to see if we really have (X*C2)+C1,
// where C1 is divisible by C2.
unsigned SubScale;
Value *SubVal =
DecomposeSimpleLinearExpr(I->getOperand(0), SubScale, Offset);
Offset += CUI->getZExtValue();
if (SubScale > 1 && (Offset % SubScale == 0)) {
Scale = SubScale;
return SubVal;
}
}
}
}
}
}
// Otherwise, we can't look past this.
Scale = 1;
Offset = 0;
return Val;
}
/// PromoteCastOfAllocation - If we find a cast of an allocation instruction,
/// try to eliminate the cast by moving the type information into the alloc.
Instruction *InstCombiner::PromoteCastOfAllocation(CastInst &CI,
AllocationInst &AI) {
const PointerType *PTy = dyn_cast<PointerType>(CI.getType());
if (!PTy) return 0; // Not casting the allocation to a pointer type.
// Remove any uses of AI that are dead.
assert(!CI.use_empty() && "Dead instructions should be removed earlier!");
std::vector<Instruction*> DeadUsers;
for (Value::use_iterator UI = AI.use_begin(), E = AI.use_end(); UI != E; ) {
Instruction *User = cast<Instruction>(*UI++);
if (isInstructionTriviallyDead(User)) {
while (UI != E && *UI == User)
++UI; // If this instruction uses AI more than once, don't break UI.
// Add operands to the worklist.
AddUsesToWorkList(*User);
++NumDeadInst;
DEBUG(std::cerr << "IC: DCE: " << *User);
User->eraseFromParent();
removeFromWorkList(User);
}
}
// Get the type really allocated and the type casted to.
const Type *AllocElTy = AI.getAllocatedType();
const Type *CastElTy = PTy->getElementType();
if (!AllocElTy->isSized() || !CastElTy->isSized()) return 0;
unsigned AllocElTyAlign = TD->getTypeAlignment(AllocElTy);
unsigned CastElTyAlign = TD->getTypeAlignment(CastElTy);
if (CastElTyAlign < AllocElTyAlign) return 0;
// If the allocation has multiple uses, only promote it if we are strictly
// increasing the alignment of the resultant allocation. If we keep it the
// same, we open the door to infinite loops of various kinds.
if (!AI.hasOneUse() && CastElTyAlign == AllocElTyAlign) return 0;
uint64_t AllocElTySize = TD->getTypeSize(AllocElTy);
uint64_t CastElTySize = TD->getTypeSize(CastElTy);
if (CastElTySize == 0 || AllocElTySize == 0) return 0;
// See if we can satisfy the modulus by pulling a scale out of the array
// size argument.
unsigned ArraySizeScale, ArrayOffset;
Value *NumElements = // See if the array size is a decomposable linear expr.
DecomposeSimpleLinearExpr(AI.getOperand(0), ArraySizeScale, ArrayOffset);
// If we can now satisfy the modulus, by using a non-1 scale, we really can
// do the xform.
if ((AllocElTySize*ArraySizeScale) % CastElTySize != 0 ||
(AllocElTySize*ArrayOffset ) % CastElTySize != 0) return 0;
unsigned Scale = (AllocElTySize*ArraySizeScale)/CastElTySize;
Value *Amt = 0;
if (Scale == 1) {
Amt = NumElements;
} else {
// If the allocation size is constant, form a constant mul expression
Amt = ConstantInt::get(Type::UIntTy, Scale);
if (isa<ConstantInt>(NumElements) && NumElements->getType()->isUnsigned())
Amt = ConstantExpr::getMul(
cast<ConstantInt>(NumElements), cast<ConstantInt>(Amt));
// otherwise multiply the amount and the number of elements
else if (Scale != 1) {
Instruction *Tmp = BinaryOperator::createMul(Amt, NumElements, "tmp");
Amt = InsertNewInstBefore(Tmp, AI);
}
}
if (unsigned Offset = (AllocElTySize*ArrayOffset)/CastElTySize) {
Value *Off = ConstantInt::get(Type::UIntTy, Offset);
Instruction *Tmp = BinaryOperator::createAdd(Amt, Off, "tmp");
Amt = InsertNewInstBefore(Tmp, AI);
}
std::string Name = AI.getName(); AI.setName("");
AllocationInst *New;
if (isa<MallocInst>(AI))
New = new MallocInst(CastElTy, Amt, AI.getAlignment(), Name);
else
New = new AllocaInst(CastElTy, Amt, AI.getAlignment(), Name);
InsertNewInstBefore(New, AI);
// If the allocation has multiple uses, insert a cast and change all things
// that used it to use the new cast. This will also hack on CI, but it will
// die soon.
if (!AI.hasOneUse()) {
AddUsesToWorkList(AI);
CastInst *NewCast = new CastInst(New, AI.getType(), "tmpcast");
InsertNewInstBefore(NewCast, AI);
AI.replaceAllUsesWith(NewCast);
}
return ReplaceInstUsesWith(CI, New);
}
/// CanEvaluateInDifferentType - Return true if we can take the specified value
/// and return it without inserting any new casts. This is used by code that
/// tries to decide whether promoting or shrinking integer operations to wider
/// or smaller types will allow us to eliminate a truncate or extend.
static bool CanEvaluateInDifferentType(Value *V, const Type *Ty,
int &NumCastsRemoved) {
if (isa<Constant>(V)) return true;
Instruction *I = dyn_cast<Instruction>(V);
if (!I || !I->hasOneUse()) return false;
switch (I->getOpcode()) {
case Instruction::And:
case Instruction::Or:
case Instruction::Xor:
// These operators can all arbitrarily be extended or truncated.
return CanEvaluateInDifferentType(I->getOperand(0), Ty, NumCastsRemoved) &&
CanEvaluateInDifferentType(I->getOperand(1), Ty, NumCastsRemoved);
case Instruction::Cast:
// If this is a cast from the destination type, we can trivially eliminate
// it, and this will remove a cast overall.
if (I->getOperand(0)->getType() == Ty) {
// If the first operand is itself a cast, and is eliminable, do not count
// this as an eliminable cast. We would prefer to eliminate those two
// casts first.
if (isa<CastInst>(I->getOperand(0)))
return true;
++NumCastsRemoved;
return true;
}
// TODO: Can handle more cases here.
break;
}
return false;
}
/// EvaluateInDifferentType - Given an expression that
/// CanEvaluateInDifferentType returns true for, actually insert the code to
/// evaluate the expression.
Value *InstCombiner::EvaluateInDifferentType(Value *V, const Type *Ty) {
if (Constant *C = dyn_cast<Constant>(V))
return ConstantExpr::getCast(C, Ty);
// Otherwise, it must be an instruction.
Instruction *I = cast<Instruction>(V);
Instruction *Res = 0;
switch (I->getOpcode()) {
case Instruction::And:
case Instruction::Or:
case Instruction::Xor: {
Value *LHS = EvaluateInDifferentType(I->getOperand(0), Ty);
Value *RHS = EvaluateInDifferentType(I->getOperand(1), Ty);
Res = BinaryOperator::create((Instruction::BinaryOps)I->getOpcode(),
LHS, RHS, I->getName());
break;
}
case Instruction::Cast:
// If this is a cast from the destination type, return the input.
if (I->getOperand(0)->getType() == Ty)
return I->getOperand(0);
// TODO: Can handle more cases here.
assert(0 && "Unreachable!");
break;
}
return InsertNewInstBefore(Res, *I);
}
// CastInst simplification
//
Instruction *InstCombiner::visitCastInst(CastInst &CI) {
Value *Src = CI.getOperand(0);
// If the user is casting a value to the same type, eliminate this cast
// instruction...
if (CI.getType() == Src->getType())
return ReplaceInstUsesWith(CI, Src);
if (isa<UndefValue>(Src)) // cast undef -> undef
return ReplaceInstUsesWith(CI, UndefValue::get(CI.getType()));
// If casting the result of another cast instruction, try to eliminate this
// one!
//
if (CastInst *CSrc = dyn_cast<CastInst>(Src)) { // A->B->C cast
Value *A = CSrc->getOperand(0);
if (isEliminableCastOfCast(A->getType(), CSrc->getType(),
CI.getType(), TD)) {
// This instruction now refers directly to the cast's src operand. This
// has a good chance of making CSrc dead.
CI.setOperand(0, CSrc->getOperand(0));
return &CI;
}
// If this is an A->B->A cast, and we are dealing with integral types, try
// to convert this into a logical 'and' instruction.
//
if (A->getType()->isInteger() &&
CI.getType()->isInteger() && CSrc->getType()->isInteger() &&
CSrc->getType()->isUnsigned() && // B->A cast must zero extend
CSrc->getType()->getPrimitiveSizeInBits() <
CI.getType()->getPrimitiveSizeInBits()&&
A->getType()->getPrimitiveSizeInBits() ==
CI.getType()->getPrimitiveSizeInBits()) {
assert(CSrc->getType() != Type::ULongTy &&
"Cannot have type bigger than ulong!");
uint64_t AndValue = CSrc->getType()->getIntegralTypeMask();
Constant *AndOp = ConstantInt::get(A->getType()->getUnsignedVersion(),
AndValue);
AndOp = ConstantExpr::getCast(AndOp, A->getType());
Instruction *And = BinaryOperator::createAnd(CSrc->getOperand(0), AndOp);
if (And->getType() != CI.getType()) {
And->setName(CSrc->getName()+".mask");
InsertNewInstBefore(And, CI);
And = new CastInst(And, CI.getType());
}
return And;
}
}
// If this is a cast to bool, turn it into the appropriate setne instruction.
if (CI.getType() == Type::BoolTy)
return BinaryOperator::createSetNE(CI.getOperand(0),
Constant::getNullValue(CI.getOperand(0)->getType()));
// See if we can simplify any instructions used by the LHS whose sole
// purpose is to compute bits we don't care about.
if (CI.getType()->isInteger() && CI.getOperand(0)->getType()->isIntegral()) {
uint64_t KnownZero, KnownOne;
if (SimplifyDemandedBits(&CI, CI.getType()->getIntegralTypeMask(),
KnownZero, KnownOne))
return &CI;
}
// If casting the result of a getelementptr instruction with no offset, turn
// this into a cast of the original pointer!
//
if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Src)) {
bool AllZeroOperands = true;
for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i)
if (!isa<Constant>(GEP->getOperand(i)) ||
!cast<Constant>(GEP->getOperand(i))->isNullValue()) {
AllZeroOperands = false;
break;
}
if (AllZeroOperands) {
CI.setOperand(0, GEP->getOperand(0));
return &CI;
}
}
// If we are casting a malloc or alloca to a pointer to a type of the same
// size, rewrite the allocation instruction to allocate the "right" type.
//
if (AllocationInst *AI = dyn_cast<AllocationInst>(Src))
if (Instruction *V = PromoteCastOfAllocation(CI, *AI))
return V;
if (SelectInst *SI = dyn_cast<SelectInst>(Src))
if (Instruction *NV = FoldOpIntoSelect(CI, SI, this))
return NV;
if (isa<PHINode>(Src))
if (Instruction *NV = FoldOpIntoPhi(CI))
return NV;
// If the source and destination are pointers, and this cast is equivalent to
// a getelementptr X, 0, 0, 0... turn it into the appropriate getelementptr.
// This can enhance SROA and other transforms that want type-safe pointers.
if (const PointerType *DstPTy = dyn_cast<PointerType>(CI.getType()))
if (const PointerType *SrcPTy = dyn_cast<PointerType>(Src->getType())) {
const Type *DstTy = DstPTy->getElementType();
const Type *SrcTy = SrcPTy->getElementType();
Constant *ZeroUInt = Constant::getNullValue(Type::UIntTy);
unsigned NumZeros = 0;
while (SrcTy != DstTy &&
isa<CompositeType>(SrcTy) && !isa<PointerType>(SrcTy) &&
SrcTy->getNumContainedTypes() /* not "{}" */) {
SrcTy = cast<CompositeType>(SrcTy)->getTypeAtIndex(ZeroUInt);
++NumZeros;
}
// If we found a path from the src to dest, create the getelementptr now.
if (SrcTy == DstTy) {
std::vector<Value*> Idxs(NumZeros+1, ZeroUInt);
return new GetElementPtrInst(Src, Idxs);
}
}
// If the source value is an instruction with only this use, we can attempt to
// propagate the cast into the instruction. Also, only handle integral types
// for now.
if (Instruction *SrcI = dyn_cast<Instruction>(Src)) {
if (SrcI->hasOneUse() && Src->getType()->isIntegral() &&
CI.getType()->isInteger()) { // Don't mess with casts to bool here
int NumCastsRemoved = 0;
if (CanEvaluateInDifferentType(SrcI, CI.getType(), NumCastsRemoved)) {
// If this cast is a truncate, evaluting in a different type always
// eliminates the cast, so it is always a win. If this is a noop-cast
// this just removes a noop cast which isn't pointful, but simplifies
// the code. If this is a zero-extension, we need to do an AND to
// maintain the clear top-part of the computation, so we require that
// the input have eliminated at least one cast. If this is a sign
// extension, we insert two new casts (to do the extension) so we
// require that two casts have been eliminated.
bool DoXForm;
switch (getCastType(Src->getType(), CI.getType())) {
default: assert(0 && "Unknown cast type!");
case Noop:
case Truncate:
DoXForm = true;
break;
case Zeroext:
DoXForm = NumCastsRemoved >= 1;
break;
case Signext:
DoXForm = NumCastsRemoved >= 2;
break;
}
if (DoXForm) {
Value *Res = EvaluateInDifferentType(SrcI, CI.getType());
assert(Res->getType() == CI.getType());
switch (getCastType(Src->getType(), CI.getType())) {
default: assert(0 && "Unknown cast type!");
case Noop:
case Truncate:
// Just replace this cast with the result.
return ReplaceInstUsesWith(CI, Res);
case Zeroext: {
// We need to emit an AND to clear the high bits.
unsigned SrcBitSize = Src->getType()->getPrimitiveSizeInBits();
unsigned DestBitSize = CI.getType()->getPrimitiveSizeInBits();
assert(SrcBitSize < DestBitSize && "Not a zext?");
Constant *C =
ConstantInt::get(Type::ULongTy, (1ULL << SrcBitSize)-1);
C = ConstantExpr::getCast(C, CI.getType());
return BinaryOperator::createAnd(Res, C);
}
case Signext:
// We need to emit a cast to truncate, then a cast to sext.
return new CastInst(InsertCastBefore(Res, Src->getType(), CI),
CI.getType());
}
}
}
const Type *DestTy = CI.getType();
unsigned SrcBitSize = Src->getType()->getPrimitiveSizeInBits();
unsigned DestBitSize = DestTy->getPrimitiveSizeInBits();
Value *Op0 = SrcI->getNumOperands() > 0 ? SrcI->getOperand(0) : 0;
Value *Op1 = SrcI->getNumOperands() > 1 ? SrcI->getOperand(1) : 0;
switch (SrcI->getOpcode()) {
case Instruction::Add:
case Instruction::Mul:
case Instruction::And:
case Instruction::Or:
case Instruction::Xor:
// If we are discarding information, or just changing the sign, rewrite.
if (DestBitSize <= SrcBitSize && DestBitSize != 1) {
// Don't insert two casts if they cannot be eliminated. We allow two
// casts to be inserted if the sizes are the same. This could only be
// converting signedness, which is a noop.
if (DestBitSize == SrcBitSize || !ValueRequiresCast(Op1, DestTy,TD) ||
!ValueRequiresCast(Op0, DestTy, TD)) {
Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI);
Value *Op1c = InsertOperandCastBefore(Op1, DestTy, SrcI);
return BinaryOperator::create(cast<BinaryOperator>(SrcI)
->getOpcode(), Op0c, Op1c);
}
}
// cast (xor bool X, true) to int --> xor (cast bool X to int), 1
if (SrcBitSize == 1 && SrcI->getOpcode() == Instruction::Xor &&
Op1 == ConstantBool::getTrue() &&
(!Op0->hasOneUse() || !isa<SetCondInst>(Op0))) {
Value *New = InsertOperandCastBefore(Op0, DestTy, &CI);
return BinaryOperator::createXor(New,
ConstantInt::get(CI.getType(), 1));
}
break;
case Instruction::SDiv:
case Instruction::UDiv:
case Instruction::SRem:
case Instruction::URem:
// If we are just changing the sign, rewrite.
if (DestBitSize == SrcBitSize) {
// Don't insert two casts if they cannot be eliminated. We allow two
// casts to be inserted if the sizes are the same. This could only be
// converting signedness, which is a noop.
if (!ValueRequiresCast(Op1, DestTy,TD) ||
!ValueRequiresCast(Op0, DestTy, TD)) {
Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI);
Value *Op1c = InsertOperandCastBefore(Op1, DestTy, SrcI);
return BinaryOperator::create(
cast<BinaryOperator>(SrcI)->getOpcode(), Op0c, Op1c);
}
}
break;
case Instruction::Shl:
// Allow changing the sign of the source operand. Do not allow changing
// the size of the shift, UNLESS the shift amount is a constant. We
// must not change variable sized shifts to a smaller size, because it
// is undefined to shift more bits out than exist in the value.
if (DestBitSize == SrcBitSize ||
(DestBitSize < SrcBitSize && isa<Constant>(Op1))) {
Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI);
return new ShiftInst(Instruction::Shl, Op0c, Op1);
}
break;
case Instruction::AShr:
// If this is a signed shr, and if all bits shifted in are about to be
// truncated off, turn it into an unsigned shr to allow greater
// simplifications.
if (DestBitSize < SrcBitSize &&
isa<ConstantInt>(Op1)) {
unsigned ShiftAmt = cast<ConstantInt>(Op1)->getZExtValue();
if (SrcBitSize > ShiftAmt && SrcBitSize-ShiftAmt >= DestBitSize) {
// Insert the new logical shift right.
return new ShiftInst(Instruction::LShr, Op0, Op1);
}
}
break;
case Instruction::SetEQ:
case Instruction::SetNE:
// We if we are just checking for a seteq of a single bit and casting it
// to an integer. If so, shift the bit to the appropriate place then
// cast to integer to avoid the comparison.
if (ConstantInt *Op1C = dyn_cast<ConstantInt>(Op1)) {
uint64_t Op1CV = Op1C->getZExtValue();
// cast (X == 0) to int --> X^1 iff X has only the low bit set.
// cast (X == 0) to int --> (X>>1)^1 iff X has only the 2nd bit set.
// cast (X == 1) to int --> X iff X has only the low bit set.
// cast (X == 2) to int --> X>>1 iff X has only the 2nd bit set.
// cast (X != 0) to int --> X iff X has only the low bit set.
// cast (X != 0) to int --> X>>1 iff X has only the 2nd bit set.
// cast (X != 1) to int --> X^1 iff X has only the low bit set.
// cast (X != 2) to int --> (X>>1)^1 iff X has only the 2nd bit set.
if (Op1CV == 0 || isPowerOf2_64(Op1CV)) {
// If Op1C some other power of two, convert:
uint64_t KnownZero, KnownOne;
uint64_t TypeMask = Op1->getType()->getIntegralTypeMask();
ComputeMaskedBits(Op0, TypeMask, KnownZero, KnownOne);
if (isPowerOf2_64(KnownZero^TypeMask)) { // Exactly one possible 1?
bool isSetNE = SrcI->getOpcode() == Instruction::SetNE;
if (Op1CV && (Op1CV != (KnownZero^TypeMask))) {
// (X&4) == 2 --> false
// (X&4) != 2 --> true
Constant *Res = ConstantBool::get(isSetNE);
Res = ConstantExpr::getCast(Res, CI.getType());
return ReplaceInstUsesWith(CI, Res);
}
unsigned ShiftAmt = Log2_64(KnownZero^TypeMask);
Value *In = Op0;
if (ShiftAmt) {
// Perform a logical shr by shiftamt.
// Insert the shift to put the result in the low bit.
In = InsertNewInstBefore(new ShiftInst(Instruction::LShr, In,
ConstantInt::get(Type::UByteTy, ShiftAmt),
In->getName()+".lobit"), CI);
}
if ((Op1CV != 0) == isSetNE) { // Toggle the low bit.
Constant *One = ConstantInt::get(In->getType(), 1);
In = BinaryOperator::createXor(In, One, "tmp");
InsertNewInstBefore(cast<Instruction>(In), CI);
}
if (CI.getType() == In->getType())
return ReplaceInstUsesWith(CI, In);
else
return new CastInst(In, CI.getType());
}
}
}
break;
}
}
if (SrcI->hasOneUse()) {
if (ShuffleVectorInst *SVI = dyn_cast<ShuffleVectorInst>(SrcI)) {
// Okay, we have (cast (shuffle ..)). We know this cast is a bitconvert
// because the inputs are known to be a vector. Check to see if this is
// a cast to a vector with the same # elts.
if (isa<PackedType>(CI.getType()) &&
cast<PackedType>(CI.getType())->getNumElements() ==
SVI->getType()->getNumElements()) {
CastInst *Tmp;
// If either of the operands is a cast from CI.getType(), then
// evaluating the shuffle in the casted destination's type will allow
// us to eliminate at least one cast.
if (((Tmp = dyn_cast<CastInst>(SVI->getOperand(0))) &&
Tmp->getOperand(0)->getType() == CI.getType()) ||
((Tmp = dyn_cast<CastInst>(SVI->getOperand(1))) &&
Tmp->getOperand(0)->getType() == CI.getType())) {
Value *LHS = InsertOperandCastBefore(SVI->getOperand(0),
CI.getType(), &CI);
Value *RHS = InsertOperandCastBefore(SVI->getOperand(1),
CI.getType(), &CI);
// Return a new shuffle vector. Use the same element ID's, as we
// know the vector types match #elts.
return new ShuffleVectorInst(LHS, RHS, SVI->getOperand(2));
}
}
}
}
}
return 0;
}
/// GetSelectFoldableOperands - We want to turn code that looks like this:
/// %C = or %A, %B
/// %D = select %cond, %C, %A
/// into:
/// %C = select %cond, %B, 0
/// %D = or %A, %C
///
/// Assuming that the specified instruction is an operand to the select, return
/// a bitmask indicating which operands of this instruction are foldable if they
/// equal the other incoming value of the select.
///
static unsigned GetSelectFoldableOperands(Instruction *I) {
switch (I->getOpcode()) {
case Instruction::Add:
case Instruction::Mul:
case Instruction::And:
case Instruction::Or:
case Instruction::Xor:
return 3; // Can fold through either operand.
case Instruction::Sub: // Can only fold on the amount subtracted.
case Instruction::Shl: // Can only fold on the shift amount.
case Instruction::LShr:
case Instruction::AShr:
return 1;
default:
return 0; // Cannot fold
}
}
/// GetSelectFoldableConstant - For the same transformation as the previous
/// function, return the identity constant that goes into the select.
static Constant *GetSelectFoldableConstant(Instruction *I) {
switch (I->getOpcode()) {
default: assert(0 && "This cannot happen!"); abort();
case Instruction::Add:
case Instruction::Sub:
case Instruction::Or:
case Instruction::Xor:
return Constant::getNullValue(I->getType());
case Instruction::Shl:
case Instruction::LShr:
case Instruction::AShr:
return Constant::getNullValue(Type::UByteTy);
case Instruction::And:
return ConstantInt::getAllOnesValue(I->getType());
case Instruction::Mul:
return ConstantInt::get(I->getType(), 1);
}
}
/// FoldSelectOpOp - Here we have (select c, TI, FI), and we know that TI and FI
/// have the same opcode and only one use each. Try to simplify this.
Instruction *InstCombiner::FoldSelectOpOp(SelectInst &SI, Instruction *TI,
Instruction *FI) {
if (TI->getNumOperands() == 1) {
// If this is a non-volatile load or a cast from the same type,
// merge.
if (TI->getOpcode() == Instruction::Cast) {
if (TI->getOperand(0)->getType() != FI->getOperand(0)->getType())
return 0;
} else {
return 0; // unknown unary op.
}
// Fold this by inserting a select from the input values.
SelectInst *NewSI = new SelectInst(SI.getCondition(), TI->getOperand(0),
FI->getOperand(0), SI.getName()+".v");
InsertNewInstBefore(NewSI, SI);
return new CastInst(NewSI, TI->getType());
}
// Only handle binary operators here.
if (!isa<ShiftInst>(TI) && !isa<BinaryOperator>(TI))
return 0;
// Figure out if the operations have any operands in common.
Value *MatchOp, *OtherOpT, *OtherOpF;
bool MatchIsOpZero;
if (TI->getOperand(0) == FI->getOperand(0)) {
MatchOp = TI->getOperand(0);
OtherOpT = TI->getOperand(1);
OtherOpF = FI->getOperand(1);
MatchIsOpZero = true;
} else if (TI->getOperand(1) == FI->getOperand(1)) {
MatchOp = TI->getOperand(1);
OtherOpT = TI->getOperand(0);
OtherOpF = FI->getOperand(0);
MatchIsOpZero = false;
} else if (!TI->isCommutative()) {
return 0;
} else if (TI->getOperand(0) == FI->getOperand(1)) {
MatchOp = TI->getOperand(0);
OtherOpT = TI->getOperand(1);
OtherOpF = FI->getOperand(0);
MatchIsOpZero = true;
} else if (TI->getOperand(1) == FI->getOperand(0)) {
MatchOp = TI->getOperand(1);
OtherOpT = TI->getOperand(0);
OtherOpF = FI->getOperand(1);
MatchIsOpZero = true;
} else {
return 0;
}
// If we reach here, they do have operations in common.
SelectInst *NewSI = new SelectInst(SI.getCondition(), OtherOpT,
OtherOpF, SI.getName()+".v");
InsertNewInstBefore(NewSI, SI);
if (BinaryOperator *BO = dyn_cast<BinaryOperator>(TI)) {
if (MatchIsOpZero)
return BinaryOperator::create(BO->getOpcode(), MatchOp, NewSI);
else
return BinaryOperator::create(BO->getOpcode(), NewSI, MatchOp);
} else {
if (MatchIsOpZero)
return new ShiftInst(cast<ShiftInst>(TI)->getOpcode(), MatchOp, NewSI);
else
return new ShiftInst(cast<ShiftInst>(TI)->getOpcode(), NewSI, MatchOp);
}
}
Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
Value *CondVal = SI.getCondition();
Value *TrueVal = SI.getTrueValue();
Value *FalseVal = SI.getFalseValue();
// select true, X, Y -> X
// select false, X, Y -> Y
if (ConstantBool *C = dyn_cast<ConstantBool>(CondVal))
return ReplaceInstUsesWith(SI, C->getValue() ? TrueVal : FalseVal);
// select C, X, X -> X
if (TrueVal == FalseVal)
return ReplaceInstUsesWith(SI, TrueVal);
if (isa<UndefValue>(TrueVal)) // select C, undef, X -> X
return ReplaceInstUsesWith(SI, FalseVal);
if (isa<UndefValue>(FalseVal)) // select C, X, undef -> X
return ReplaceInstUsesWith(SI, TrueVal);
if (isa<UndefValue>(CondVal)) { // select undef, X, Y -> X or Y
if (isa<Constant>(TrueVal))
return ReplaceInstUsesWith(SI, TrueVal);
else
return ReplaceInstUsesWith(SI, FalseVal);
}
if (SI.getType() == Type::BoolTy)
if (ConstantBool *C = dyn_cast<ConstantBool>(TrueVal)) {
if (C->getValue()) {
// Change: A = select B, true, C --> A = or B, C
return BinaryOperator::createOr(CondVal, FalseVal);
} else {
// Change: A = select B, false, C --> A = and !B, C
Value *NotCond =
InsertNewInstBefore(BinaryOperator::createNot(CondVal,
"not."+CondVal->getName()), SI);
return BinaryOperator::createAnd(NotCond, FalseVal);
}
} else if (ConstantBool *C = dyn_cast<ConstantBool>(FalseVal)) {
if (C->getValue() == false) {
// Change: A = select B, C, false --> A = and B, C
return BinaryOperator::createAnd(CondVal, TrueVal);
} else {
// Change: A = select B, C, true --> A = or !B, C
Value *NotCond =
InsertNewInstBefore(BinaryOperator::createNot(CondVal,
"not."+CondVal->getName()), SI);
return BinaryOperator::createOr(NotCond, TrueVal);
}
}
// Selecting between two integer constants?
if (ConstantInt *TrueValC = dyn_cast<ConstantInt>(TrueVal))
if (ConstantInt *FalseValC = dyn_cast<ConstantInt>(FalseVal)) {
// select C, 1, 0 -> cast C to int
if (FalseValC->isNullValue() && TrueValC->getZExtValue() == 1) {
return new CastInst(CondVal, SI.getType());
} else if (TrueValC->isNullValue() && FalseValC->getZExtValue() == 1) {
// select C, 0, 1 -> cast !C to int
Value *NotCond =
InsertNewInstBefore(BinaryOperator::createNot(CondVal,
"not."+CondVal->getName()), SI);
return new CastInst(NotCond, SI.getType());
}
if (SetCondInst *IC = dyn_cast<SetCondInst>(SI.getCondition())) {
// (x <s 0) ? -1 : 0 -> sra x, 31
// (x >u 2147483647) ? -1 : 0 -> sra x, 31
if (TrueValC->isAllOnesValue() && FalseValC->isNullValue())
if (ConstantInt *CmpCst = dyn_cast<ConstantInt>(IC->getOperand(1))) {
bool CanXForm = false;
if (CmpCst->getType()->isSigned())
CanXForm = CmpCst->isNullValue() &&
IC->getOpcode() == Instruction::SetLT;
else {
unsigned Bits = CmpCst->getType()->getPrimitiveSizeInBits();
CanXForm = (CmpCst->getZExtValue() == ~0ULL >> (64-Bits+1)) &&
IC->getOpcode() == Instruction::SetGT;
}
if (CanXForm) {
// The comparison constant and the result are not neccessarily the
// same width. In any case, the first step to do is make sure
// that X is signed.
Value *X = IC->getOperand(0);
if (!X->getType()->isSigned())
X = InsertCastBefore(X, X->getType()->getSignedVersion(), SI);
// Now that X is signed, we have to make the all ones value. Do
// this by inserting a new SRA.
unsigned Bits = X->getType()->getPrimitiveSizeInBits();
Constant *ShAmt = ConstantInt::get(Type::UByteTy, Bits-1);
Instruction *SRA = new ShiftInst(Instruction::AShr, X,
ShAmt, "ones");
InsertNewInstBefore(SRA, SI);
// Finally, convert to the type of the select RHS. If this is
// smaller than the compare value, it will truncate the ones to
// fit. If it is larger, it will sext the ones to fit.
return new CastInst(SRA, SI.getType());
}
}
// If one of the constants is zero (we know they can't both be) and we
// have a setcc instruction with zero, and we have an 'and' with the
// non-constant value, eliminate this whole mess. This corresponds to
// cases like this: ((X & 27) ? 27 : 0)
if (TrueValC->isNullValue() || FalseValC->isNullValue())
if (IC->isEquality() && isa<ConstantInt>(IC->getOperand(1)) &&
cast<Constant>(IC->getOperand(1))->isNullValue())
if (Instruction *ICA = dyn_cast<Instruction>(IC->getOperand(0)))
if (ICA->getOpcode() == Instruction::And &&
isa<ConstantInt>(ICA->getOperand(1)) &&
(ICA->getOperand(1) == TrueValC ||
ICA->getOperand(1) == FalseValC) &&
isOneBitSet(cast<ConstantInt>(ICA->getOperand(1)))) {
// Okay, now we know that everything is set up, we just don't
// know whether we have a setne or seteq and whether the true or
// false val is the zero.
bool ShouldNotVal = !TrueValC->isNullValue();
ShouldNotVal ^= IC->getOpcode() == Instruction::SetNE;
Value *V = ICA;
if (ShouldNotVal)
V = InsertNewInstBefore(BinaryOperator::create(
Instruction::Xor, V, ICA->getOperand(1)), SI);
return ReplaceInstUsesWith(SI, V);
}
}
}
// See if we are selecting two values based on a comparison of the two values.
if (SetCondInst *SCI = dyn_cast<SetCondInst>(CondVal)) {
if (SCI->getOperand(0) == TrueVal && SCI->getOperand(1) == FalseVal) {
// Transform (X == Y) ? X : Y -> Y
if (SCI->getOpcode() == Instruction::SetEQ)
return ReplaceInstUsesWith(SI, FalseVal);
// Transform (X != Y) ? X : Y -> X
if (SCI->getOpcode() == Instruction::SetNE)
return ReplaceInstUsesWith(SI, TrueVal);
// NOTE: if we wanted to, this is where to detect MIN/MAX/ABS/etc.
} else if (SCI->getOperand(0) == FalseVal && SCI->getOperand(1) == TrueVal){
// Transform (X == Y) ? Y : X -> X
if (SCI->getOpcode() == Instruction::SetEQ)
return ReplaceInstUsesWith(SI, FalseVal);
// Transform (X != Y) ? Y : X -> Y
if (SCI->getOpcode() == Instruction::SetNE)
return ReplaceInstUsesWith(SI, TrueVal);
// NOTE: if we wanted to, this is where to detect MIN/MAX/ABS/etc.
}
}
if (Instruction *TI = dyn_cast<Instruction>(TrueVal))
if (Instruction *FI = dyn_cast<Instruction>(FalseVal))
if (TI->hasOneUse() && FI->hasOneUse()) {
Instruction *AddOp = 0, *SubOp = 0;
// Turn (select C, (op X, Y), (op X, Z)) -> (op X, (select C, Y, Z))
if (TI->getOpcode() == FI->getOpcode())
if (Instruction *IV = FoldSelectOpOp(SI, TI, FI))
return IV;
// Turn select C, (X+Y), (X-Y) --> (X+(select C, Y, (-Y))). This is
// even legal for FP.
if (TI->getOpcode() == Instruction::Sub &&
FI->getOpcode() == Instruction::Add) {
AddOp = FI; SubOp = TI;
} else if (FI->getOpcode() == Instruction::Sub &&
TI->getOpcode() == Instruction::Add) {
AddOp = TI; SubOp = FI;
}
if (AddOp) {
Value *OtherAddOp = 0;
if (SubOp->getOperand(0) == AddOp->getOperand(0)) {
OtherAddOp = AddOp->getOperand(1);
} else if (SubOp->getOperand(0) == AddOp->getOperand(1)) {
OtherAddOp = AddOp->getOperand(0);
}
if (OtherAddOp) {
// So at this point we know we have (Y -> OtherAddOp):
// select C, (add X, Y), (sub X, Z)
Value *NegVal; // Compute -Z
if (Constant *C = dyn_cast<Constant>(SubOp->getOperand(1))) {
NegVal = ConstantExpr::getNeg(C);
} else {
NegVal = InsertNewInstBefore(
BinaryOperator::createNeg(SubOp->getOperand(1), "tmp"), SI);
}
Value *NewTrueOp = OtherAddOp;
Value *NewFalseOp = NegVal;
if (AddOp != TI)
std::swap(NewTrueOp, NewFalseOp);
Instruction *NewSel =
new SelectInst(CondVal, NewTrueOp,NewFalseOp,SI.getName()+".p");
NewSel = InsertNewInstBefore(NewSel, SI);
return BinaryOperator::createAdd(SubOp->getOperand(0), NewSel);
}
}
}
// See if we can fold the select into one of our operands.
if (SI.getType()->isInteger()) {
// See the comment above GetSelectFoldableOperands for a description of the
// transformation we are doing here.
if (Instruction *TVI = dyn_cast<Instruction>(TrueVal))
if (TVI->hasOneUse() && TVI->getNumOperands() == 2 &&
!isa<Constant>(FalseVal))
if (unsigned SFO = GetSelectFoldableOperands(TVI)) {
unsigned OpToFold = 0;
if ((SFO & 1) && FalseVal == TVI->getOperand(0)) {
OpToFold = 1;
} else if ((SFO & 2) && FalseVal == TVI->getOperand(1)) {
OpToFold = 2;
}
if (OpToFold) {
Constant *C = GetSelectFoldableConstant(TVI);
std::string Name = TVI->getName(); TVI->setName("");
Instruction *NewSel =
new SelectInst(SI.getCondition(), TVI->getOperand(2-OpToFold), C,
Name);
InsertNewInstBefore(NewSel, SI);
if (BinaryOperator *BO = dyn_cast<BinaryOperator>(TVI))
return BinaryOperator::create(BO->getOpcode(), FalseVal, NewSel);
else if (ShiftInst *SI = dyn_cast<ShiftInst>(TVI))
return new ShiftInst(SI->getOpcode(), FalseVal, NewSel);
else {
assert(0 && "Unknown instruction!!");
}
}
}
if (Instruction *FVI = dyn_cast<Instruction>(FalseVal))
if (FVI->hasOneUse() && FVI->getNumOperands() == 2 &&
!isa<Constant>(TrueVal))
if (unsigned SFO = GetSelectFoldableOperands(FVI)) {
unsigned OpToFold = 0;
if ((SFO & 1) && TrueVal == FVI->getOperand(0)) {
OpToFold = 1;
} else if ((SFO & 2) && TrueVal == FVI->getOperand(1)) {
OpToFold = 2;
}
if (OpToFold) {
Constant *C = GetSelectFoldableConstant(FVI);
std::string Name = FVI->getName(); FVI->setName("");
Instruction *NewSel =
new SelectInst(SI.getCondition(), C, FVI->getOperand(2-OpToFold),
Name);
InsertNewInstBefore(NewSel, SI);
if (BinaryOperator *BO = dyn_cast<BinaryOperator>(FVI))
return BinaryOperator::create(BO->getOpcode(), TrueVal, NewSel);
else if (ShiftInst *SI = dyn_cast<ShiftInst>(FVI))
return new ShiftInst(SI->getOpcode(), TrueVal, NewSel);
else {
assert(0 && "Unknown instruction!!");
}
}
}
}
if (BinaryOperator::isNot(CondVal)) {
SI.setOperand(0, BinaryOperator::getNotArgument(CondVal));
SI.setOperand(1, FalseVal);
SI.setOperand(2, TrueVal);
return &SI;
}
return 0;
}
/// GetKnownAlignment - If the specified pointer has an alignment that we can
/// determine, return it, otherwise return 0.
static unsigned GetKnownAlignment(Value *V, TargetData *TD) {
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) {
unsigned Align = GV->getAlignment();
if (Align == 0 && TD)
Align = TD->getTypeAlignment(GV->getType()->getElementType());
return Align;
} else if (AllocationInst *AI = dyn_cast<AllocationInst>(V)) {
unsigned Align = AI->getAlignment();
if (Align == 0 && TD) {
if (isa<AllocaInst>(AI))
Align = TD->getTypeAlignment(AI->getType()->getElementType());
else if (isa<MallocInst>(AI)) {
// Malloc returns maximally aligned memory.
Align = TD->getTypeAlignment(AI->getType()->getElementType());
Align = std::max(Align, (unsigned)TD->getTypeAlignment(Type::DoubleTy));
Align = std::max(Align, (unsigned)TD->getTypeAlignment(Type::LongTy));
}
}
return Align;
} else if (isa<CastInst>(V) ||
(isa<ConstantExpr>(V) &&
cast<ConstantExpr>(V)->getOpcode() == Instruction::Cast)) {
User *CI = cast<User>(V);
if (isa<PointerType>(CI->getOperand(0)->getType()))
return GetKnownAlignment(CI->getOperand(0), TD);
return 0;
} else if (isa<GetElementPtrInst>(V) ||
(isa<ConstantExpr>(V) &&
cast<ConstantExpr>(V)->getOpcode()==Instruction::GetElementPtr)) {
User *GEPI = cast<User>(V);
unsigned BaseAlignment = GetKnownAlignment(GEPI->getOperand(0), TD);
if (BaseAlignment == 0) return 0;
// If all indexes are zero, it is just the alignment of the base pointer.
bool AllZeroOperands = true;
for (unsigned i = 1, e = GEPI->getNumOperands(); i != e; ++i)
if (!isa<Constant>(GEPI->getOperand(i)) ||
!cast<Constant>(GEPI->getOperand(i))->isNullValue()) {
AllZeroOperands = false;
break;
}
if (AllZeroOperands)
return BaseAlignment;
// Otherwise, if the base alignment is >= the alignment we expect for the
// base pointer type, then we know that the resultant pointer is aligned at
// least as much as its type requires.
if (!TD) return 0;
const Type *BasePtrTy = GEPI->getOperand(0)->getType();
if (TD->getTypeAlignment(cast<PointerType>(BasePtrTy)->getElementType())
<= BaseAlignment) {
const Type *GEPTy = GEPI->getType();
return TD->getTypeAlignment(cast<PointerType>(GEPTy)->getElementType());
}
return 0;
}
return 0;
}
/// visitCallInst - CallInst simplification. This mostly only handles folding
/// of intrinsic instructions. For normal calls, it allows visitCallSite to do
/// the heavy lifting.
///
Instruction *InstCombiner::visitCallInst(CallInst &CI) {
IntrinsicInst *II = dyn_cast<IntrinsicInst>(&CI);
if (!II) return visitCallSite(&CI);
// Intrinsics cannot occur in an invoke, so handle them here instead of in
// visitCallSite.
if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(II)) {
bool Changed = false;
// memmove/cpy/set of zero bytes is a noop.
if (Constant *NumBytes = dyn_cast<Constant>(MI->getLength())) {
if (NumBytes->isNullValue()) return EraseInstFromFunction(CI);
if (ConstantInt *CI = dyn_cast<ConstantInt>(NumBytes))
if (CI->getZExtValue() == 1) {
// Replace the instruction with just byte operations. We would
// transform other cases to loads/stores, but we don't know if
// alignment is sufficient.
}
}
// If we have a memmove and the source operation is a constant global,
// then the source and dest pointers can't alias, so we can change this
// into a call to memcpy.
if (MemMoveInst *MMI = dyn_cast<MemMoveInst>(II)) {
if (GlobalVariable *GVSrc = dyn_cast<GlobalVariable>(MMI->getSource()))
if (GVSrc->isConstant()) {
Module *M = CI.getParent()->getParent()->getParent();
const char *Name;
if (CI.getCalledFunction()->getFunctionType()->getParamType(2) ==
Type::UIntTy)
Name = "llvm.memcpy.i32";
else
Name = "llvm.memcpy.i64";
Function *MemCpy = M->getOrInsertFunction(Name,
CI.getCalledFunction()->getFunctionType());
CI.setOperand(0, MemCpy);
Changed = true;
}
}
// If we can determine a pointer alignment that is bigger than currently
// set, update the alignment.
if (isa<MemCpyInst>(MI) || isa<MemMoveInst>(MI)) {
unsigned Alignment1 = GetKnownAlignment(MI->getOperand(1), TD);
unsigned Alignment2 = GetKnownAlignment(MI->getOperand(2), TD);
unsigned Align = std::min(Alignment1, Alignment2);
if (MI->getAlignment()->getZExtValue() < Align) {
MI->setAlignment(ConstantInt::get(Type::UIntTy, Align));
Changed = true;
}
} else if (isa<MemSetInst>(MI)) {
unsigned Alignment = GetKnownAlignment(MI->getDest(), TD);
if (MI->getAlignment()->getZExtValue() < Alignment) {
MI->setAlignment(ConstantInt::get(Type::UIntTy, Alignment));
Changed = true;
}
}
if (Changed) return II;
} else {
switch (II->getIntrinsicID()) {
default: break;
case Intrinsic::ppc_altivec_lvx:
case Intrinsic::ppc_altivec_lvxl:
case Intrinsic::x86_sse_loadu_ps:
case Intrinsic::x86_sse2_loadu_pd:
case Intrinsic::x86_sse2_loadu_dq:
// Turn PPC lvx -> load if the pointer is known aligned.
// Turn X86 loadups -> load if the pointer is known aligned.
if (GetKnownAlignment(II->getOperand(1), TD) >= 16) {
Value *Ptr = InsertCastBefore(II->getOperand(1),
PointerType::get(II->getType()), CI);
return new LoadInst(Ptr);
}
break;
case Intrinsic::ppc_altivec_stvx:
case Intrinsic::ppc_altivec_stvxl:
// Turn stvx -> store if the pointer is known aligned.
if (GetKnownAlignment(II->getOperand(2), TD) >= 16) {
const Type *OpPtrTy = PointerType::get(II->getOperand(1)->getType());
Value *Ptr = InsertCastBefore(II->getOperand(2), OpPtrTy, CI);
return new StoreInst(II->getOperand(1), Ptr);
}
break;
case Intrinsic::x86_sse_storeu_ps:
case Intrinsic::x86_sse2_storeu_pd:
case Intrinsic::x86_sse2_storeu_dq:
case Intrinsic::x86_sse2_storel_dq:
// Turn X86 storeu -> store if the pointer is known aligned.
if (GetKnownAlignment(II->getOperand(1), TD) >= 16) {
const Type *OpPtrTy = PointerType::get(II->getOperand(2)->getType());
Value *Ptr = InsertCastBefore(II->getOperand(1), OpPtrTy, CI);
return new StoreInst(II->getOperand(2), Ptr);
}
break;
case Intrinsic::x86_sse_cvttss2si: {
// These intrinsics only demands the 0th element of its input vector. If
// we can simplify the input based on that, do so now.
uint64_t UndefElts;
if (Value *V = SimplifyDemandedVectorElts(II->getOperand(1), 1,
UndefElts)) {
II->setOperand(1, V);
return II;
}
break;
}
case Intrinsic::ppc_altivec_vperm:
// Turn vperm(V1,V2,mask) -> shuffle(V1,V2,mask) if mask is a constant.
if (ConstantPacked *Mask = dyn_cast<ConstantPacked>(II->getOperand(3))) {
assert(Mask->getNumOperands() == 16 && "Bad type for intrinsic!");
// Check that all of the elements are integer constants or undefs.
bool AllEltsOk = true;
for (unsigned i = 0; i != 16; ++i) {
if (!isa<ConstantInt>(Mask->getOperand(i)) &&
!isa<UndefValue>(Mask->getOperand(i))) {
AllEltsOk = false;
break;
}
}
if (AllEltsOk) {
// Cast the input vectors to byte vectors.
Value *Op0 = InsertCastBefore(II->getOperand(1), Mask->getType(), CI);
Value *Op1 = InsertCastBefore(II->getOperand(2), Mask->getType(), CI);
Value *Result = UndefValue::get(Op0->getType());
// Only extract each element once.
Value *ExtractedElts[32];
memset(ExtractedElts, 0, sizeof(ExtractedElts));
for (unsigned i = 0; i != 16; ++i) {
if (isa<UndefValue>(Mask->getOperand(i)))
continue;
unsigned Idx =cast<ConstantInt>(Mask->getOperand(i))->getZExtValue();
Idx &= 31; // Match the hardware behavior.
if (ExtractedElts[Idx] == 0) {
Instruction *Elt =
new ExtractElementInst(Idx < 16 ? Op0 : Op1, Idx&15, "tmp");
InsertNewInstBefore(Elt, CI);
ExtractedElts[Idx] = Elt;
}
// Insert this value into the result vector.
Result = new InsertElementInst(Result, ExtractedElts[Idx], i,"tmp");
InsertNewInstBefore(cast<Instruction>(Result), CI);
}
return new CastInst(Result, CI.getType());
}
}
break;
case Intrinsic::stackrestore: {
// If the save is right next to the restore, remove the restore. This can
// happen when variable allocas are DCE'd.
if (IntrinsicInst *SS = dyn_cast<IntrinsicInst>(II->getOperand(1))) {
if (SS->getIntrinsicID() == Intrinsic::stacksave) {
BasicBlock::iterator BI = SS;
if (&*++BI == II)
return EraseInstFromFunction(CI);
}
}
// If the stack restore is in a return/unwind block and if there are no
// allocas or calls between the restore and the return, nuke the restore.
TerminatorInst *TI = II->getParent()->getTerminator();
if (isa<ReturnInst>(TI) || isa<UnwindInst>(TI)) {
BasicBlock::iterator BI = II;
bool CannotRemove = false;
for (++BI; &*BI != TI; ++BI) {
if (isa<AllocaInst>(BI) ||
(isa<CallInst>(BI) && !isa<IntrinsicInst>(BI))) {
CannotRemove = true;
break;
}
}
if (!CannotRemove)
return EraseInstFromFunction(CI);
}
break;
}
}
}
return visitCallSite(II);
}
// InvokeInst simplification
//
Instruction *InstCombiner::visitInvokeInst(InvokeInst &II) {
return visitCallSite(&II);
}
// visitCallSite - Improvements for call and invoke instructions.
//
Instruction *InstCombiner::visitCallSite(CallSite CS) {
bool Changed = false;
// If the callee is a constexpr cast of a function, attempt to move the cast
// to the arguments of the call/invoke.
if (transformConstExprCastCall(CS)) return 0;
Value *Callee = CS.getCalledValue();
if (Function *CalleeF = dyn_cast<Function>(Callee))
if (CalleeF->getCallingConv() != CS.getCallingConv()) {
Instruction *OldCall = CS.getInstruction();
// If the call and callee calling conventions don't match, this call must
// be unreachable, as the call is undefined.
new StoreInst(ConstantBool::getTrue(),
UndefValue::get(PointerType::get(Type::BoolTy)), OldCall);
if (!OldCall->use_empty())
OldCall->replaceAllUsesWith(UndefValue::get(OldCall->getType()));
if (isa<CallInst>(OldCall)) // Not worth removing an invoke here.
return EraseInstFromFunction(*OldCall);
return 0;
}
if (isa<ConstantPointerNull>(Callee) || isa<UndefValue>(Callee)) {
// This instruction is not reachable, just remove it. We insert a store to
// undef so that we know that this code is not reachable, despite the fact
// that we can't modify the CFG here.
new StoreInst(ConstantBool::getTrue(),
UndefValue::get(PointerType::get(Type::BoolTy)),
CS.getInstruction());
if (!CS.getInstruction()->use_empty())
CS.getInstruction()->
replaceAllUsesWith(UndefValue::get(CS.getInstruction()->getType()));
if (InvokeInst *II = dyn_cast<InvokeInst>(CS.getInstruction())) {
// Don't break the CFG, insert a dummy cond branch.
new BranchInst(II->getNormalDest(), II->getUnwindDest(),
ConstantBool::getTrue(), II);
}
return EraseInstFromFunction(*CS.getInstruction());
}
const PointerType *PTy = cast<PointerType>(Callee->getType());
const FunctionType *FTy = cast<FunctionType>(PTy->getElementType());
if (FTy->isVarArg()) {
// See if we can optimize any arguments passed through the varargs area of
// the call.
for (CallSite::arg_iterator I = CS.arg_begin()+FTy->getNumParams(),
E = CS.arg_end(); I != E; ++I)
if (CastInst *CI = dyn_cast<CastInst>(*I)) {
// If this cast does not effect the value passed through the varargs
// area, we can eliminate the use of the cast.
Value *Op = CI->getOperand(0);
if (CI->getType()->isLosslesslyConvertibleTo(Op->getType())) {
*I = Op;
Changed = true;
}
}
}
return Changed ? CS.getInstruction() : 0;
}
// transformConstExprCastCall - If the callee is a constexpr cast of a function,
// attempt to move the cast to the arguments of the call/invoke.
//
bool InstCombiner::transformConstExprCastCall(CallSite CS) {
if (!isa<ConstantExpr>(CS.getCalledValue())) return false;
ConstantExpr *CE = cast<ConstantExpr>(CS.getCalledValue());
if (CE->getOpcode() != Instruction::Cast || !isa<Function>(CE->getOperand(0)))
return false;
Function *Callee = cast<Function>(CE->getOperand(0));
Instruction *Caller = CS.getInstruction();
// Okay, this is a cast from a function to a different type. Unless doing so
// would cause a type conversion of one of our arguments, change this call to
// be a direct call with arguments casted to the appropriate types.
//
const FunctionType *FT = Callee->getFunctionType();
const Type *OldRetTy = Caller->getType();
// Check to see if we are changing the return type...
if (OldRetTy != FT->getReturnType()) {
if (Callee->isExternal() &&
!(OldRetTy->isLosslesslyConvertibleTo(FT->getReturnType()) ||
(isa<PointerType>(FT->getReturnType()) &&
TD->getIntPtrType()->isLosslesslyConvertibleTo(OldRetTy)))
&& !Caller->use_empty())
return false; // Cannot transform this return value...
// If the callsite is an invoke instruction, and the return value is used by
// a PHI node in a successor, we cannot change the return type of the call
// because there is no place to put the cast instruction (without breaking
// the critical edge). Bail out in this case.
if (!Caller->use_empty())
if (InvokeInst *II = dyn_cast<InvokeInst>(Caller))
for (Value::use_iterator UI = II->use_begin(), E = II->use_end();
UI != E; ++UI)
if (PHINode *PN = dyn_cast<PHINode>(*UI))
if (PN->getParent() == II->getNormalDest() ||
PN->getParent() == II->getUnwindDest())
return false;
}
unsigned NumActualArgs = unsigned(CS.arg_end()-CS.arg_begin());
unsigned NumCommonArgs = std::min(FT->getNumParams(), NumActualArgs);
CallSite::arg_iterator AI = CS.arg_begin();
for (unsigned i = 0, e = NumCommonArgs; i != e; ++i, ++AI) {
const Type *ParamTy = FT->getParamType(i);
const Type *ActTy = (*AI)->getType();
ConstantInt* c = dyn_cast<ConstantInt>(*AI);
//Either we can cast directly, or we can upconvert the argument
bool isConvertible = ActTy->isLosslesslyConvertibleTo(ParamTy) ||
(ParamTy->isIntegral() && ActTy->isIntegral() &&
ParamTy->isSigned() == ActTy->isSigned() &&
ParamTy->getPrimitiveSize() >= ActTy->getPrimitiveSize()) ||
(c && ParamTy->getPrimitiveSize() >= ActTy->getPrimitiveSize() &&
c->getSExtValue() > 0);
if (Callee->isExternal() && !isConvertible) return false;
}
if (FT->getNumParams() < NumActualArgs && !FT->isVarArg() &&
Callee->isExternal())
return false; // Do not delete arguments unless we have a function body...
// Okay, we decided that this is a safe thing to do: go ahead and start
// inserting cast instructions as necessary...
std::vector<Value*> Args;
Args.reserve(NumActualArgs);
AI = CS.arg_begin();
for (unsigned i = 0; i != NumCommonArgs; ++i, ++AI) {
const Type *ParamTy = FT->getParamType(i);
if ((*AI)->getType() == ParamTy) {
Args.push_back(*AI);
} else {
Args.push_back(InsertNewInstBefore(new CastInst(*AI, ParamTy, "tmp"),
*Caller));
}
}
// If the function takes more arguments than the call was taking, add them
// now...
for (unsigned i = NumCommonArgs; i != FT->getNumParams(); ++i)
Args.push_back(Constant::getNullValue(FT->getParamType(i)));
// If we are removing arguments to the function, emit an obnoxious warning...
if (FT->getNumParams() < NumActualArgs)
if (!FT->isVarArg()) {
std::cerr << "WARNING: While resolving call to function '"
<< Callee->getName() << "' arguments were dropped!\n";
} else {
// Add all of the arguments in their promoted form to the arg list...
for (unsigned i = FT->getNumParams(); i != NumActualArgs; ++i, ++AI) {
const Type *PTy = getPromotedType((*AI)->getType());
if (PTy != (*AI)->getType()) {
// Must promote to pass through va_arg area!
Instruction *Cast = new CastInst(*AI, PTy, "tmp");
InsertNewInstBefore(Cast, *Caller);
Args.push_back(Cast);
} else {
Args.push_back(*AI);
}
}
}
if (FT->getReturnType() == Type::VoidTy)
Caller->setName(""); // Void type should not have a name...
Instruction *NC;
if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
NC = new InvokeInst(Callee, II->getNormalDest(), II->getUnwindDest(),
Args, Caller->getName(), Caller);
cast<InvokeInst>(II)->setCallingConv(II->getCallingConv());
} else {
NC = new CallInst(Callee, Args, Caller->getName(), Caller);
if (cast<CallInst>(Caller)->isTailCall())
cast<CallInst>(NC)->setTailCall();
cast<CallInst>(NC)->setCallingConv(cast<CallInst>(Caller)->getCallingConv());
}
// Insert a cast of the return type as necessary...
Value *NV = NC;
if (Caller->getType() != NV->getType() && !Caller->use_empty()) {
if (NV->getType() != Type::VoidTy) {
NV = NC = new CastInst(NC, Caller->getType(), "tmp");
// If this is an invoke instruction, we should insert it after the first
// non-phi, instruction in the normal successor block.
if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
BasicBlock::iterator I = II->getNormalDest()->begin();
while (isa<PHINode>(I)) ++I;
InsertNewInstBefore(NC, *I);
} else {
// Otherwise, it's a call, just insert cast right after the call instr
InsertNewInstBefore(NC, *Caller);
}
AddUsersToWorkList(*Caller);
} else {
NV = UndefValue::get(Caller->getType());
}
}
if (Caller->getType() != Type::VoidTy && !Caller->use_empty())
Caller->replaceAllUsesWith(NV);
Caller->getParent()->getInstList().erase(Caller);
removeFromWorkList(Caller);
return true;
}
/// FoldPHIArgBinOpIntoPHI - If we have something like phi [add (a,b), add(c,d)]
/// and if a/b/c/d and the add's all have a single use, turn this into two phi's
/// and a single binop.
Instruction *InstCombiner::FoldPHIArgBinOpIntoPHI(PHINode &PN) {
Instruction *FirstInst = cast<Instruction>(PN.getIncomingValue(0));
assert(isa<BinaryOperator>(FirstInst) || isa<ShiftInst>(FirstInst) ||
isa<GetElementPtrInst>(FirstInst));
unsigned Opc = FirstInst->getOpcode();
const Type *LHSType = FirstInst->getOperand(0)->getType();
const Type *RHSType = FirstInst->getOperand(1)->getType();
// Scan to see if all operands are the same opcode, all have one use, and all
// kill their operands (i.e. the operands have one use).
for (unsigned i = 0; i != PN.getNumIncomingValues(); ++i) {
Instruction *I = dyn_cast<Instruction>(PN.getIncomingValue(i));
if (!I || I->getOpcode() != Opc || !I->hasOneUse() ||
// Verify type of the LHS matches so we don't fold setcc's of different
// types or GEP's with different index types.
I->getOperand(0)->getType() != LHSType ||
I->getOperand(1)->getType() != RHSType)
return 0;
}
// Otherwise, this is safe and profitable to transform. Create two phi nodes.
PHINode *NewLHS = new PHINode(FirstInst->getOperand(0)->getType(),
FirstInst->getOperand(0)->getName()+".pn");
NewLHS->reserveOperandSpace(PN.getNumOperands()/2);
PHINode *NewRHS = new PHINode(FirstInst->getOperand(1)->getType(),
FirstInst->getOperand(1)->getName()+".pn");
NewRHS->reserveOperandSpace(PN.getNumOperands()/2);
Value *InLHS = FirstInst->getOperand(0);
NewLHS->addIncoming(InLHS, PN.getIncomingBlock(0));
Value *InRHS = FirstInst->getOperand(1);
NewRHS->addIncoming(InRHS, PN.getIncomingBlock(0));
// Add all operands to the new PHsI.
for (unsigned i = 1, e = PN.getNumIncomingValues(); i != e; ++i) {
Value *NewInLHS = cast<Instruction>(PN.getIncomingValue(i))->getOperand(0);
Value *NewInRHS = cast<Instruction>(PN.getIncomingValue(i))->getOperand(1);
if (NewInLHS != InLHS) InLHS = 0;
if (NewInRHS != InRHS) InRHS = 0;
NewLHS->addIncoming(NewInLHS, PN.getIncomingBlock(i));
NewRHS->addIncoming(NewInRHS, PN.getIncomingBlock(i));
}
Value *LHSVal;
if (InLHS) {
// The new PHI unions all of the same values together. This is really
// common, so we handle it intelligently here for compile-time speed.
LHSVal = InLHS;
delete NewLHS;
} else {
InsertNewInstBefore(NewLHS, PN);
LHSVal = NewLHS;
}
Value *RHSVal;
if (InRHS) {
// The new PHI unions all of the same values together. This is really
// common, so we handle it intelligently here for compile-time speed.
RHSVal = InRHS;
delete NewRHS;
} else {
InsertNewInstBefore(NewRHS, PN);
RHSVal = NewRHS;
}
if (BinaryOperator *BinOp = dyn_cast<BinaryOperator>(FirstInst))
return BinaryOperator::create(BinOp->getOpcode(), LHSVal, RHSVal);
else if (ShiftInst *SI = dyn_cast<ShiftInst>(FirstInst))
return new ShiftInst(SI->getOpcode(), LHSVal, RHSVal);
else {
assert(isa<GetElementPtrInst>(FirstInst));
return new GetElementPtrInst(LHSVal, RHSVal);
}
}
/// isSafeToSinkLoad - Return true if we know that it is safe sink the load out
/// of the block that defines it. This means that it must be obvious the value
/// of the load is not changed from the point of the load to the end of the
/// block it is in.
static bool isSafeToSinkLoad(LoadInst *L) {
BasicBlock::iterator BBI = L, E = L->getParent()->end();
for (++BBI; BBI != E; ++BBI)
if (BBI->mayWriteToMemory())
return false;
return true;
}
// FoldPHIArgOpIntoPHI - If all operands to a PHI node are the same "unary"
// operator and they all are only used by the PHI, PHI together their
// inputs, and do the operation once, to the result of the PHI.
Instruction *InstCombiner::FoldPHIArgOpIntoPHI(PHINode &PN) {
Instruction *FirstInst = cast<Instruction>(PN.getIncomingValue(0));
// Scan the instruction, looking for input operations that can be folded away.
// If all input operands to the phi are the same instruction (e.g. a cast from
// the same type or "+42") we can pull the operation through the PHI, reducing
// code size and simplifying code.
Constant *ConstantOp = 0;
const Type *CastSrcTy = 0;
bool isVolatile = false;
if (isa<CastInst>(FirstInst)) {
CastSrcTy = FirstInst->getOperand(0)->getType();
} else if (isa<BinaryOperator>(FirstInst) || isa<ShiftInst>(FirstInst)) {
// Can fold binop or shift here if the RHS is a constant, otherwise call
// FoldPHIArgBinOpIntoPHI.
ConstantOp = dyn_cast<Constant>(FirstInst->getOperand(1));
if (ConstantOp == 0)
return FoldPHIArgBinOpIntoPHI(PN);
} else if (LoadInst *LI = dyn_cast<LoadInst>(FirstInst)) {
isVolatile = LI->isVolatile();
// We can't sink the load if the loaded value could be modified between the
// load and the PHI.
if (LI->getParent() != PN.getIncomingBlock(0) ||
!isSafeToSinkLoad(LI))
return 0;
} else if (isa<GetElementPtrInst>(FirstInst)) {
if (FirstInst->getNumOperands() == 2)
return FoldPHIArgBinOpIntoPHI(PN);
// Can't handle general GEPs yet.
return 0;
} else {
return 0; // Cannot fold this operation.
}
// Check to see if all arguments are the same operation.
for (unsigned i = 1, e = PN.getNumIncomingValues(); i != e; ++i) {
if (!isa<Instruction>(PN.getIncomingValue(i))) return 0;
Instruction *I = cast<Instruction>(PN.getIncomingValue(i));
if (!I->hasOneUse() || I->getOpcode() != FirstInst->getOpcode())
return 0;
if (CastSrcTy) {
if (I->getOperand(0)->getType() != CastSrcTy)
return 0; // Cast operation must match.
} else if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
// We can't sink the load if the loaded value could be modified between the
// load and the PHI.
if (LI->isVolatile() != isVolatile ||
LI->getParent() != PN.getIncomingBlock(i) ||
!isSafeToSinkLoad(LI))
return 0;
} else if (I->getOperand(1) != ConstantOp) {
return 0;
}
}
// Okay, they are all the same operation. Create a new PHI node of the
// correct type, and PHI together all of the LHS's of the instructions.
PHINode *NewPN = new PHINode(FirstInst->getOperand(0)->getType(),
PN.getName()+".in");
NewPN->reserveOperandSpace(PN.getNumOperands()/2);
Value *InVal = FirstInst->getOperand(0);
NewPN->addIncoming(InVal, PN.getIncomingBlock(0));
// Add all operands to the new PHI.
for (unsigned i = 1, e = PN.getNumIncomingValues(); i != e; ++i) {
Value *NewInVal = cast<Instruction>(PN.getIncomingValue(i))->getOperand(0);
if (NewInVal != InVal)
InVal = 0;
NewPN->addIncoming(NewInVal, PN.getIncomingBlock(i));
}
Value *PhiVal;
if (InVal) {
// The new PHI unions all of the same values together. This is really
// common, so we handle it intelligently here for compile-time speed.
PhiVal = InVal;
delete NewPN;
} else {
InsertNewInstBefore(NewPN, PN);
PhiVal = NewPN;
}
// Insert and return the new operation.
if (isa<CastInst>(FirstInst))
return new CastInst(PhiVal, PN.getType());
else if (isa<LoadInst>(FirstInst))
return new LoadInst(PhiVal, "", isVolatile);
else if (BinaryOperator *BinOp = dyn_cast<BinaryOperator>(FirstInst))
return BinaryOperator::create(BinOp->getOpcode(), PhiVal, ConstantOp);
else
return new ShiftInst(cast<ShiftInst>(FirstInst)->getOpcode(),
PhiVal, ConstantOp);
}
/// DeadPHICycle - Return true if this PHI node is only used by a PHI node cycle
/// that is dead.
static bool DeadPHICycle(PHINode *PN, std::set<PHINode*> &PotentiallyDeadPHIs) {
if (PN->use_empty()) return true;
if (!PN->hasOneUse()) return false;
// Remember this node, and if we find the cycle, return.
if (!PotentiallyDeadPHIs.insert(PN).second)
return true;
if (PHINode *PU = dyn_cast<PHINode>(PN->use_back()))
return DeadPHICycle(PU, PotentiallyDeadPHIs);
return false;
}
// PHINode simplification
//
Instruction *InstCombiner::visitPHINode(PHINode &PN) {
// If LCSSA is around, don't mess with Phi nodes
if (mustPreserveAnalysisID(LCSSAID)) return 0;
if (Value *V = PN.hasConstantValue())
return ReplaceInstUsesWith(PN, V);
// If the only user of this instruction is a cast instruction, and all of the
// incoming values are constants, change this PHI to merge together the casted
// constants.
if (PN.hasOneUse())
if (CastInst *CI = dyn_cast<CastInst>(PN.use_back()))
if (CI->getType() != PN.getType()) { // noop casts will be folded
bool AllConstant = true;
for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
if (!isa<Constant>(PN.getIncomingValue(i))) {
AllConstant = false;
break;
}
if (AllConstant) {
// Make a new PHI with all casted values.
PHINode *New = new PHINode(CI->getType(), PN.getName(), &PN);
for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) {
Constant *OldArg = cast<Constant>(PN.getIncomingValue(i));
New->addIncoming(ConstantExpr::getCast(OldArg, New->getType()),
PN.getIncomingBlock(i));
}
// Update the cast instruction.
CI->setOperand(0, New);
WorkList.push_back(CI); // revisit the cast instruction to fold.
WorkList.push_back(New); // Make sure to revisit the new Phi
return &PN; // PN is now dead!
}
}
// If all PHI operands are the same operation, pull them through the PHI,
// reducing code size.
if (isa<Instruction>(PN.getIncomingValue(0)) &&
PN.getIncomingValue(0)->hasOneUse())
if (Instruction *Result = FoldPHIArgOpIntoPHI(PN))
return Result;
// If this is a trivial cycle in the PHI node graph, remove it. Basically, if
// this PHI only has a single use (a PHI), and if that PHI only has one use (a
// PHI)... break the cycle.
if (PN.hasOneUse())
if (PHINode *PU = dyn_cast<PHINode>(PN.use_back())) {
std::set<PHINode*> PotentiallyDeadPHIs;
PotentiallyDeadPHIs.insert(&PN);
if (DeadPHICycle(PU, PotentiallyDeadPHIs))
return ReplaceInstUsesWith(PN, UndefValue::get(PN.getType()));
}
return 0;
}
static Value *InsertSignExtendToPtrTy(Value *V, const Type *DTy,
Instruction *InsertPoint,
InstCombiner *IC) {
unsigned PS = IC->getTargetData().getPointerSize();
const Type *VTy = V->getType();
if (!VTy->isSigned() && VTy->getPrimitiveSize() < PS)
// We must insert a cast to ensure we sign-extend.
V = IC->InsertCastBefore(V, VTy->getSignedVersion(), *InsertPoint);
return IC->InsertCastBefore(V, DTy, *InsertPoint);
}
Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
Value *PtrOp = GEP.getOperand(0);
// Is it 'getelementptr %P, long 0' or 'getelementptr %P'
// If so, eliminate the noop.
if (GEP.getNumOperands() == 1)
return ReplaceInstUsesWith(GEP, PtrOp);
if (isa<UndefValue>(GEP.getOperand(0)))
return ReplaceInstUsesWith(GEP, UndefValue::get(GEP.getType()));
bool HasZeroPointerIndex = false;
if (Constant *C = dyn_cast<Constant>(GEP.getOperand(1)))
HasZeroPointerIndex = C->isNullValue();
if (GEP.getNumOperands() == 2 && HasZeroPointerIndex)
return ReplaceInstUsesWith(GEP, PtrOp);
// Eliminate unneeded casts for indices.
bool MadeChange = false;
gep_type_iterator GTI = gep_type_begin(GEP);
for (unsigned i = 1, e = GEP.getNumOperands(); i != e; ++i, ++GTI)
if (isa<SequentialType>(*GTI)) {
if (CastInst *CI = dyn_cast<CastInst>(GEP.getOperand(i))) {
Value *Src = CI->getOperand(0);
const Type *SrcTy = Src->getType();
const Type *DestTy = CI->getType();
if (Src->getType()->isInteger()) {
if (SrcTy->getPrimitiveSizeInBits() ==
DestTy->getPrimitiveSizeInBits()) {
// We can always eliminate a cast from ulong or long to the other.
// We can always eliminate a cast from uint to int or the other on
// 32-bit pointer platforms.
if (DestTy->getPrimitiveSizeInBits() >= TD->getPointerSizeInBits()){
MadeChange = true;
GEP.setOperand(i, Src);
}
} else if (SrcTy->getPrimitiveSize() < DestTy->getPrimitiveSize() &&
SrcTy->getPrimitiveSize() == 4) {
// We can always eliminate a cast from int to [u]long. We can
// eliminate a cast from uint to [u]long iff the target is a 32-bit
// pointer target.
if (SrcTy->isSigned() ||
SrcTy->getPrimitiveSizeInBits() >= TD->getPointerSizeInBits()) {
MadeChange = true;
GEP.setOperand(i, Src);
}
}
}
}
// If we are using a wider index than needed for this platform, shrink it
// to what we need. If the incoming value needs a cast instruction,
// insert it. This explicit cast can make subsequent optimizations more
// obvious.
Value *Op = GEP.getOperand(i);
if (Op->getType()->getPrimitiveSize() > TD->getPointerSize())
if (Constant *C = dyn_cast<Constant>(Op)) {
GEP.setOperand(i, ConstantExpr::getCast(C,
TD->getIntPtrType()->getSignedVersion()));
MadeChange = true;
} else {
Op = InsertCastBefore(Op, TD->getIntPtrType(), GEP);
GEP.setOperand(i, Op);
MadeChange = true;
}
// If this is a constant idx, make sure to canonicalize it to be a signed
// operand, otherwise CSE and other optimizations are pessimized.
if (ConstantInt *CUI = dyn_cast<ConstantInt>(Op))
if (CUI->getType()->isUnsigned()) {
GEP.setOperand(i,
ConstantExpr::getCast(CUI, CUI->getType()->getSignedVersion()));
MadeChange = true;
}
}
if (MadeChange) return &GEP;
// Combine Indices - If the source pointer to this getelementptr instruction
// is a getelementptr instruction, combine the indices of the two
// getelementptr instructions into a single instruction.
//
std::vector<Value*> SrcGEPOperands;
if (User *Src = dyn_castGetElementPtr(PtrOp))
SrcGEPOperands.assign(Src->op_begin(), Src->op_end());
if (!SrcGEPOperands.empty()) {
// Note that if our source is a gep chain itself that we wait for that
// chain to be resolved before we perform this transformation. This
// avoids us creating a TON of code in some cases.
//
if (isa<GetElementPtrInst>(SrcGEPOperands[0]) &&
cast<Instruction>(SrcGEPOperands[0])->getNumOperands() == 2)
return 0; // Wait until our source is folded to completion.
std::vector<Value *> Indices;
// Find out whether the last index in the source GEP is a sequential idx.
bool EndsWithSequential = false;
for (gep_type_iterator I = gep_type_begin(*cast<User>(PtrOp)),
E = gep_type_end(*cast<User>(PtrOp)); I != E; ++I)
EndsWithSequential = !isa<StructType>(*I);
// Can we combine the two pointer arithmetics offsets?
if (EndsWithSequential) {
// Replace: gep (gep %P, long B), long A, ...
// With: T = long A+B; gep %P, T, ...
//
Value *Sum, *SO1 = SrcGEPOperands.back(), *GO1 = GEP.getOperand(1);
if (SO1 == Constant::getNullValue(SO1->getType())) {
Sum = GO1;
} else if (GO1 == Constant::getNullValue(GO1->getType())) {
Sum = SO1;
} else {
// If they aren't the same type, convert both to an integer of the
// target's pointer size.
if (SO1->getType() != GO1->getType()) {
if (Constant *SO1C = dyn_cast<Constant>(SO1)) {
SO1 = ConstantExpr::getCast(SO1C, GO1->getType());
} else if (Constant *GO1C = dyn_cast<Constant>(GO1)) {
GO1 = ConstantExpr::getCast(GO1C, SO1->getType());
} else {
unsigned PS = TD->getPointerSize();
if (SO1->getType()->getPrimitiveSize() == PS) {
// Convert GO1 to SO1's type.
GO1 = InsertSignExtendToPtrTy(GO1, SO1->getType(), &GEP, this);
} else if (GO1->getType()->getPrimitiveSize() == PS) {
// Convert SO1 to GO1's type.
SO1 = InsertSignExtendToPtrTy(SO1, GO1->getType(), &GEP, this);
} else {
const Type *PT = TD->getIntPtrType();
SO1 = InsertSignExtendToPtrTy(SO1, PT, &GEP, this);
GO1 = InsertSignExtendToPtrTy(GO1, PT, &GEP, this);
}
}
}
if (isa<Constant>(SO1) && isa<Constant>(GO1))
Sum = ConstantExpr::getAdd(cast<Constant>(SO1), cast<Constant>(GO1));
else {
Sum = BinaryOperator::createAdd(SO1, GO1, PtrOp->getName()+".sum");
InsertNewInstBefore(cast<Instruction>(Sum), GEP);
}
}
// Recycle the GEP we already have if possible.
if (SrcGEPOperands.size() == 2) {
GEP.setOperand(0, SrcGEPOperands[0]);
GEP.setOperand(1, Sum);
return &GEP;
} else {
Indices.insert(Indices.end(), SrcGEPOperands.begin()+1,
SrcGEPOperands.end()-1);
Indices.push_back(Sum);
Indices.insert(Indices.end(), GEP.op_begin()+2, GEP.op_end());
}
} else if (isa<Constant>(*GEP.idx_begin()) &&
cast<Constant>(*GEP.idx_begin())->isNullValue() &&
SrcGEPOperands.size() != 1) {
// Otherwise we can do the fold if the first index of the GEP is a zero
Indices.insert(Indices.end(), SrcGEPOperands.begin()+1,
SrcGEPOperands.end());
Indices.insert(Indices.end(), GEP.idx_begin()+1, GEP.idx_end());
}
if (!Indices.empty())
return new GetElementPtrInst(SrcGEPOperands[0], Indices, GEP.getName());
} else if (GlobalValue *GV = dyn_cast<GlobalValue>(PtrOp)) {
// GEP of global variable. If all of the indices for this GEP are
// constants, we can promote this to a constexpr instead of an instruction.
// Scan for nonconstants...
std::vector<Constant*> Indices;
User::op_iterator I = GEP.idx_begin(), E = GEP.idx_end();
for (; I != E && isa<Constant>(*I); ++I)
Indices.push_back(cast<Constant>(*I));
if (I == E) { // If they are all constants...
Constant *CE = ConstantExpr::getGetElementPtr(GV, Indices);
// Replace all uses of the GEP with the new constexpr...
return ReplaceInstUsesWith(GEP, CE);
}
} else if (Value *X = isCast(PtrOp)) { // Is the operand a cast?
if (!isa<PointerType>(X->getType())) {
// Not interesting. Source pointer must be a cast from pointer.
} else if (HasZeroPointerIndex) {
// transform: GEP (cast [10 x ubyte]* X to [0 x ubyte]*), long 0, ...
// into : GEP [10 x ubyte]* X, long 0, ...
//
// This occurs when the program declares an array extern like "int X[];"
//
const PointerType *CPTy = cast<PointerType>(PtrOp->getType());
const PointerType *XTy = cast<PointerType>(X->getType());
if (const ArrayType *XATy =
dyn_cast<ArrayType>(XTy->getElementType()))
if (const ArrayType *CATy =
dyn_cast<ArrayType>(CPTy->getElementType()))
if (CATy->getElementType() == XATy->getElementType()) {
// At this point, we know that the cast source type is a pointer
// to an array of the same type as the destination pointer
// array. Because the array type is never stepped over (there
// is a leading zero) we can fold the cast into this GEP.
GEP.setOperand(0, X);
return &GEP;
}
} else if (GEP.getNumOperands() == 2) {
// Transform things like:
// %t = getelementptr ubyte* cast ([2 x int]* %str to uint*), uint %V
// into: %t1 = getelementptr [2 x int*]* %str, int 0, uint %V; cast
const Type *SrcElTy = cast<PointerType>(X->getType())->getElementType();
const Type *ResElTy=cast<PointerType>(PtrOp->getType())->getElementType();
if (isa<ArrayType>(SrcElTy) &&
TD->getTypeSize(cast<ArrayType>(SrcElTy)->getElementType()) ==
TD->getTypeSize(ResElTy)) {
Value *V = InsertNewInstBefore(
new GetElementPtrInst(X, Constant::getNullValue(Type::IntTy),
GEP.getOperand(1), GEP.getName()), GEP);
return new CastInst(V, GEP.getType());
}
// Transform things like:
// getelementptr sbyte* cast ([100 x double]* X to sbyte*), int %tmp
// (where tmp = 8*tmp2) into:
// getelementptr [100 x double]* %arr, int 0, int %tmp.2
if (isa<ArrayType>(SrcElTy) &&
(ResElTy == Type::SByteTy || ResElTy == Type::UByteTy)) {
uint64_t ArrayEltSize =
TD->getTypeSize(cast<ArrayType>(SrcElTy)->getElementType());
// Check to see if "tmp" is a scale by a multiple of ArrayEltSize. We
// allow either a mul, shift, or constant here.
Value *NewIdx = 0;
ConstantInt *Scale = 0;
if (ArrayEltSize == 1) {
NewIdx = GEP.getOperand(1);
Scale = ConstantInt::get(NewIdx->getType(), 1);
} else if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP.getOperand(1))) {
NewIdx = ConstantInt::get(CI->getType(), 1);
Scale = CI;
} else if (Instruction *Inst =dyn_cast<Instruction>(GEP.getOperand(1))){
if (Inst->getOpcode() == Instruction::Shl &&
isa<ConstantInt>(Inst->getOperand(1))) {
unsigned ShAmt =
cast<ConstantInt>(Inst->getOperand(1))->getZExtValue();
if (Inst->getType()->isSigned())
Scale = ConstantInt::get(Inst->getType(), 1ULL << ShAmt);
else
Scale = ConstantInt::get(Inst->getType(), 1ULL << ShAmt);
NewIdx = Inst->getOperand(0);
} else if (Inst->getOpcode() == Instruction::Mul &&
isa<ConstantInt>(Inst->getOperand(1))) {
Scale = cast<ConstantInt>(Inst->getOperand(1));
NewIdx = Inst->getOperand(0);
}
}
// If the index will be to exactly the right offset with the scale taken
// out, perform the transformation.
if (Scale && Scale->getZExtValue() % ArrayEltSize == 0) {
if (isa<ConstantInt>(Scale))
Scale = ConstantInt::get(Scale->getType(),
Scale->getZExtValue() / ArrayEltSize);
if (Scale->getZExtValue() != 1) {
Constant *C = ConstantExpr::getCast(Scale, NewIdx->getType());
Instruction *Sc = BinaryOperator::createMul(NewIdx, C, "idxscale");
NewIdx = InsertNewInstBefore(Sc, GEP);
}
// Insert the new GEP instruction.
Instruction *Idx =
new GetElementPtrInst(X, Constant::getNullValue(Type::IntTy),
NewIdx, GEP.getName());
Idx = InsertNewInstBefore(Idx, GEP);
return new CastInst(Idx, GEP.getType());
}
}
}
}
return 0;
}
Instruction *InstCombiner::visitAllocationInst(AllocationInst &AI) {
// Convert: malloc Ty, C - where C is a constant != 1 into: malloc [C x Ty], 1
if (AI.isArrayAllocation()) // Check C != 1
if (const ConstantInt *C = dyn_cast<ConstantInt>(AI.getArraySize())) {
const Type *NewTy =
ArrayType::get(AI.getAllocatedType(), C->getZExtValue());
AllocationInst *New = 0;
// Create and insert the replacement instruction...
if (isa<MallocInst>(AI))
New = new MallocInst(NewTy, 0, AI.getAlignment(), AI.getName());
else {
assert(isa<AllocaInst>(AI) && "Unknown type of allocation inst!");
New = new AllocaInst(NewTy, 0, AI.getAlignment(), AI.getName());
}
InsertNewInstBefore(New, AI);
// Scan to the end of the allocation instructions, to skip over a block of
// allocas if possible...
//
BasicBlock::iterator It = New;
while (isa<AllocationInst>(*It)) ++It;
// Now that I is pointing to the first non-allocation-inst in the block,
// insert our getelementptr instruction...
//
Value *NullIdx = Constant::getNullValue(Type::IntTy);
Value *V = new GetElementPtrInst(New, NullIdx, NullIdx,
New->getName()+".sub", It);
// Now make everything use the getelementptr instead of the original
// allocation.
return ReplaceInstUsesWith(AI, V);
} else if (isa<UndefValue>(AI.getArraySize())) {
return ReplaceInstUsesWith(AI, Constant::getNullValue(AI.getType()));
}
// If alloca'ing a zero byte object, replace the alloca with a null pointer.
// Note that we only do this for alloca's, because malloc should allocate and
// return a unique pointer, even for a zero byte allocation.
if (isa<AllocaInst>(AI) && AI.getAllocatedType()->isSized() &&
TD->getTypeSize(AI.getAllocatedType()) == 0)
return ReplaceInstUsesWith(AI, Constant::getNullValue(AI.getType()));
return 0;
}
Instruction *InstCombiner::visitFreeInst(FreeInst &FI) {
Value *Op = FI.getOperand(0);
// Change free <ty>* (cast <ty2>* X to <ty>*) into free <ty2>* X
if (CastInst *CI = dyn_cast<CastInst>(Op))
if (isa<PointerType>(CI->getOperand(0)->getType())) {
FI.setOperand(0, CI->getOperand(0));
return &FI;
}
// free undef -> unreachable.
if (isa<UndefValue>(Op)) {
// Insert a new store to null because we cannot modify the CFG here.
new StoreInst(ConstantBool::getTrue(),
UndefValue::get(PointerType::get(Type::BoolTy)), &FI);
return EraseInstFromFunction(FI);
}
// If we have 'free null' delete the instruction. This can happen in stl code
// when lots of inlining happens.
if (isa<ConstantPointerNull>(Op))
return EraseInstFromFunction(FI);
return 0;
}
/// InstCombineLoadCast - Fold 'load (cast P)' -> cast (load P)' when possible.
static Instruction *InstCombineLoadCast(InstCombiner &IC, LoadInst &LI) {
User *CI = cast<User>(LI.getOperand(0));
Value *CastOp = CI->getOperand(0);
const Type *DestPTy = cast<PointerType>(CI->getType())->getElementType();
if (const PointerType *SrcTy = dyn_cast<PointerType>(CastOp->getType())) {
const Type *SrcPTy = SrcTy->getElementType();
if (DestPTy->isInteger() || isa<PointerType>(DestPTy) ||
isa<PackedType>(DestPTy)) {
// If the source is an array, the code below will not succeed. Check to
// see if a trivial 'gep P, 0, 0' will help matters. Only do this for
// constants.
if (const ArrayType *ASrcTy = dyn_cast<ArrayType>(SrcPTy))
if (Constant *CSrc = dyn_cast<Constant>(CastOp))
if (ASrcTy->getNumElements() != 0) {
std::vector<Value*> Idxs(2, Constant::getNullValue(Type::IntTy));
CastOp = ConstantExpr::getGetElementPtr(CSrc, Idxs);
SrcTy = cast<PointerType>(CastOp->getType());
SrcPTy = SrcTy->getElementType();
}
if ((SrcPTy->isInteger() || isa<PointerType>(SrcPTy) ||
isa<PackedType>(SrcPTy)) &&
// Do not allow turning this into a load of an integer, which is then
// casted to a pointer, this pessimizes pointer analysis a lot.
(isa<PointerType>(SrcPTy) == isa<PointerType>(LI.getType())) &&
IC.getTargetData().getTypeSize(SrcPTy) ==
IC.getTargetData().getTypeSize(DestPTy)) {
// Okay, we are casting from one integer or pointer type to another of
// the same size. Instead of casting the pointer before the load, cast
// the result of the loaded value.
Value *NewLoad = IC.InsertNewInstBefore(new LoadInst(CastOp,
CI->getName(),
LI.isVolatile()),LI);
// Now cast the result of the load.
return new CastInst(NewLoad, LI.getType());
}
}
}
return 0;
}
/// isSafeToLoadUnconditionally - Return true if we know that executing a load
/// from this value cannot trap. If it is not obviously safe to load from the
/// specified pointer, we do a quick local scan of the basic block containing
/// ScanFrom, to determine if the address is already accessed.
static bool isSafeToLoadUnconditionally(Value *V, Instruction *ScanFrom) {
// If it is an alloca or global variable, it is always safe to load from.
if (isa<AllocaInst>(V) || isa<GlobalVariable>(V)) return true;
// Otherwise, be a little bit agressive by scanning the local block where we
// want to check to see if the pointer is already being loaded or stored
// from/to. If so, the previous load or store would have already trapped,
// so there is no harm doing an extra load (also, CSE will later eliminate
// the load entirely).
BasicBlock::iterator BBI = ScanFrom, E = ScanFrom->getParent()->begin();
while (BBI != E) {
--BBI;
if (LoadInst *LI = dyn_cast<LoadInst>(BBI)) {
if (LI->getOperand(0) == V) return true;
} else if (StoreInst *SI = dyn_cast<StoreInst>(BBI))
if (SI->getOperand(1) == V) return true;
}
return false;
}
Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
Value *Op = LI.getOperand(0);
// load (cast X) --> cast (load X) iff safe
if (isa<CastInst>(Op))
if (Instruction *Res = InstCombineLoadCast(*this, LI))
return Res;
// None of the following transforms are legal for volatile loads.
if (LI.isVolatile()) return 0;
if (&LI.getParent()->front() != &LI) {
BasicBlock::iterator BBI = &LI; --BBI;
// If the instruction immediately before this is a store to the same
// address, do a simple form of store->load forwarding.
if (StoreInst *SI = dyn_cast<StoreInst>(BBI))
if (SI->getOperand(1) == LI.getOperand(0))
return ReplaceInstUsesWith(LI, SI->getOperand(0));
if (LoadInst *LIB = dyn_cast<LoadInst>(BBI))
if (LIB->getOperand(0) == LI.getOperand(0))
return ReplaceInstUsesWith(LI, LIB);
}
if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(Op))
if (isa<ConstantPointerNull>(GEPI->getOperand(0)) ||
isa<UndefValue>(GEPI->getOperand(0))) {
// Insert a new store to null instruction before the load to indicate
// that this code is not reachable. We do this instead of inserting
// an unreachable instruction directly because we cannot modify the
// CFG.
new StoreInst(UndefValue::get(LI.getType()),
Constant::getNullValue(Op->getType()), &LI);
return ReplaceInstUsesWith(LI, UndefValue::get(LI.getType()));
}
if (Constant *C = dyn_cast<Constant>(Op)) {
// load null/undef -> undef
if ((C->isNullValue() || isa<UndefValue>(C))) {
// Insert a new store to null instruction before the load to indicate that
// this code is not reachable. We do this instead of inserting an
// unreachable instruction directly because we cannot modify the CFG.
new StoreInst(UndefValue::get(LI.getType()),
Constant::getNullValue(Op->getType()), &LI);
return ReplaceInstUsesWith(LI, UndefValue::get(LI.getType()));
}
// Instcombine load (constant global) into the value loaded.
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Op))
if (GV->isConstant() && !GV->isExternal())
return ReplaceInstUsesWith(LI, GV->getInitializer());
// Instcombine load (constantexpr_GEP global, 0, ...) into the value loaded.
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Op))
if (CE->getOpcode() == Instruction::GetElementPtr) {
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getOperand(0)))
if (GV->isConstant() && !GV->isExternal())
if (Constant *V =
ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE))
return ReplaceInstUsesWith(LI, V);
if (CE->getOperand(0)->isNullValue()) {
// Insert a new store to null instruction before the load to indicate
// that this code is not reachable. We do this instead of inserting
// an unreachable instruction directly because we cannot modify the
// CFG.
new StoreInst(UndefValue::get(LI.getType()),
Constant::getNullValue(Op->getType()), &LI);
return ReplaceInstUsesWith(LI, UndefValue::get(LI.getType()));
}
} else if (CE->getOpcode() == Instruction::Cast) {
if (Instruction *Res = InstCombineLoadCast(*this, LI))
return Res;
}
}
if (Op->hasOneUse()) {
// Change select and PHI nodes to select values instead of addresses: this
// helps alias analysis out a lot, allows many others simplifications, and
// exposes redundancy in the code.
//
// Note that we cannot do the transformation unless we know that the
// introduced loads cannot trap! Something like this is valid as long as
// the condition is always false: load (select bool %C, int* null, int* %G),
// but it would not be valid if we transformed it to load from null
// unconditionally.
//
if (SelectInst *SI = dyn_cast<SelectInst>(Op)) {
// load (select (Cond, &V1, &V2)) --> select(Cond, load &V1, load &V2).
if (isSafeToLoadUnconditionally(SI->getOperand(1), SI) &&
isSafeToLoadUnconditionally(SI->getOperand(2), SI)) {
Value *V1 = InsertNewInstBefore(new LoadInst(SI->getOperand(1),
SI->getOperand(1)->getName()+".val"), LI);
Value *V2 = InsertNewInstBefore(new LoadInst(SI->getOperand(2),
SI->getOperand(2)->getName()+".val"), LI);
return new SelectInst(SI->getCondition(), V1, V2);
}
// load (select (cond, null, P)) -> load P
if (Constant *C = dyn_cast<Constant>(SI->getOperand(1)))
if (C->isNullValue()) {
LI.setOperand(0, SI->getOperand(2));
return &LI;
}
// load (select (cond, P, null)) -> load P
if (Constant *C = dyn_cast<Constant>(SI->getOperand(2)))
if (C->isNullValue()) {
LI.setOperand(0, SI->getOperand(1));
return &LI;
}
}
}
return 0;
}
/// InstCombineStoreToCast - Fold 'store V, (cast P)' -> store (cast V), P'
/// when possible.
static Instruction *InstCombineStoreToCast(InstCombiner &IC, StoreInst &SI) {
User *CI = cast<User>(SI.getOperand(1));
Value *CastOp = CI->getOperand(0);
const Type *DestPTy = cast<PointerType>(CI->getType())->getElementType();
if (const PointerType *SrcTy = dyn_cast<PointerType>(CastOp->getType())) {
const Type *SrcPTy = SrcTy->getElementType();
if (DestPTy->isInteger() || isa<PointerType>(DestPTy)) {
// If the source is an array, the code below will not succeed. Check to
// see if a trivial 'gep P, 0, 0' will help matters. Only do this for
// constants.
if (const ArrayType *ASrcTy = dyn_cast<ArrayType>(SrcPTy))
if (Constant *CSrc = dyn_cast<Constant>(CastOp))
if (ASrcTy->getNumElements() != 0) {
std::vector<Value*> Idxs(2, Constant::getNullValue(Type::IntTy));
CastOp = ConstantExpr::getGetElementPtr(CSrc, Idxs);
SrcTy = cast<PointerType>(CastOp->getType());
SrcPTy = SrcTy->getElementType();
}
if ((SrcPTy->isInteger() || isa<PointerType>(SrcPTy)) &&
IC.getTargetData().getTypeSize(SrcPTy) ==
IC.getTargetData().getTypeSize(DestPTy)) {
// Okay, we are casting from one integer or pointer type to another of
// the same size. Instead of casting the pointer before the store, cast
// the value to be stored.
Value *NewCast;
if (Constant *C = dyn_cast<Constant>(SI.getOperand(0)))
NewCast = ConstantExpr::getCast(C, SrcPTy);
else
NewCast = IC.InsertNewInstBefore(new CastInst(SI.getOperand(0),
SrcPTy,
SI.getOperand(0)->getName()+".c"), SI);
return new StoreInst(NewCast, CastOp);
}
}
}
return 0;
}
Instruction *InstCombiner::visitStoreInst(StoreInst &SI) {
Value *Val = SI.getOperand(0);
Value *Ptr = SI.getOperand(1);
if (isa<UndefValue>(Ptr)) { // store X, undef -> noop (even if volatile)
EraseInstFromFunction(SI);
++NumCombined;
return 0;
}
// Do really simple DSE, to catch cases where there are several consequtive
// stores to the same location, separated by a few arithmetic operations. This
// situation often occurs with bitfield accesses.
BasicBlock::iterator BBI = &SI;
for (unsigned ScanInsts = 6; BBI != SI.getParent()->begin() && ScanInsts;
--ScanInsts) {
--BBI;
if (StoreInst *PrevSI = dyn_cast<StoreInst>(BBI)) {
// Prev store isn't volatile, and stores to the same location?
if (!PrevSI->isVolatile() && PrevSI->getOperand(1) == SI.getOperand(1)) {
++NumDeadStore;
++BBI;
EraseInstFromFunction(*PrevSI);
continue;
}
break;
}
// If this is a load, we have to stop. However, if the loaded value is from
// the pointer we're loading and is producing the pointer we're storing,
// then *this* store is dead (X = load P; store X -> P).
if (LoadInst *LI = dyn_cast<LoadInst>(BBI)) {
if (LI == Val && LI->getOperand(0) == Ptr) {
EraseInstFromFunction(SI);
++NumCombined;
return 0;
}
// Otherwise, this is a load from some other location. Stores before it
// may not be dead.
break;
}
// Don't skip over loads or things that can modify memory.
if (BBI->mayWriteToMemory())
break;
}
if (SI.isVolatile()) return 0; // Don't hack volatile stores.
// store X, null -> turns into 'unreachable' in SimplifyCFG
if (isa<ConstantPointerNull>(Ptr)) {
if (!isa<UndefValue>(Val)) {
SI.setOperand(0, UndefValue::get(Val->getType()));
if (Instruction *U = dyn_cast<Instruction>(Val))
WorkList.push_back(U); // Dropped a use.
++NumCombined;
}
return 0; // Do not modify these!
}
// store undef, Ptr -> noop
if (isa<UndefValue>(Val)) {
EraseInstFromFunction(SI);
++NumCombined;
return 0;
}
// If the pointer destination is a cast, see if we can fold the cast into the
// source instead.
if (isa<CastInst>(Ptr))
if (Instruction *Res = InstCombineStoreToCast(*this, SI))
return Res;
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr))
if (CE->getOpcode() == Instruction::Cast)
if (Instruction *Res = InstCombineStoreToCast(*this, SI))
return Res;
// If this store is the last instruction in the basic block, and if the block
// ends with an unconditional branch, try to move it to the successor block.
BBI = &SI; ++BBI;
if (BranchInst *BI = dyn_cast<BranchInst>(BBI))
if (BI->isUnconditional()) {
// Check to see if the successor block has exactly two incoming edges. If
// so, see if the other predecessor contains a store to the same location.
// if so, insert a PHI node (if needed) and move the stores down.
BasicBlock *Dest = BI->getSuccessor(0);
pred_iterator PI = pred_begin(Dest);
BasicBlock *Other = 0;
if (*PI != BI->getParent())
Other = *PI;
++PI;
if (PI != pred_end(Dest)) {
if (*PI != BI->getParent())
if (Other)
Other = 0;
else
Other = *PI;
if (++PI != pred_end(Dest))
Other = 0;
}
if (Other) { // If only one other pred...
BBI = Other->getTerminator();
// Make sure this other block ends in an unconditional branch and that
// there is an instruction before the branch.
if (isa<BranchInst>(BBI) && cast<BranchInst>(BBI)->isUnconditional() &&
BBI != Other->begin()) {
--BBI;
StoreInst *OtherStore = dyn_cast<StoreInst>(BBI);
// If this instruction is a store to the same location.
if (OtherStore && OtherStore->getOperand(1) == SI.getOperand(1)) {
// Okay, we know we can perform this transformation. Insert a PHI
// node now if we need it.
Value *MergedVal = OtherStore->getOperand(0);
if (MergedVal != SI.getOperand(0)) {
PHINode *PN = new PHINode(MergedVal->getType(), "storemerge");
PN->reserveOperandSpace(2);
PN->addIncoming(SI.getOperand(0), SI.getParent());
PN->addIncoming(OtherStore->getOperand(0), Other);
MergedVal = InsertNewInstBefore(PN, Dest->front());
}
// Advance to a place where it is safe to insert the new store and
// insert it.
BBI = Dest->begin();
while (isa<PHINode>(BBI)) ++BBI;
InsertNewInstBefore(new StoreInst(MergedVal, SI.getOperand(1),
OtherStore->isVolatile()), *BBI);
// Nuke the old stores.
EraseInstFromFunction(SI);
EraseInstFromFunction(*OtherStore);
++NumCombined;
return 0;
}
}
}
}
return 0;
}
Instruction *InstCombiner::visitBranchInst(BranchInst &BI) {
// Change br (not X), label True, label False to: br X, label False, True
Value *X = 0;
BasicBlock *TrueDest;
BasicBlock *FalseDest;
if (match(&BI, m_Br(m_Not(m_Value(X)), TrueDest, FalseDest)) &&
!isa<Constant>(X)) {
// Swap Destinations and condition...
BI.setCondition(X);
BI.setSuccessor(0, FalseDest);
BI.setSuccessor(1, TrueDest);
return &BI;
}
// Cannonicalize setne -> seteq
Instruction::BinaryOps Op; Value *Y;
if (match(&BI, m_Br(m_SetCond(Op, m_Value(X), m_Value(Y)),
TrueDest, FalseDest)))
if ((Op == Instruction::SetNE || Op == Instruction::SetLE ||
Op == Instruction::SetGE) && BI.getCondition()->hasOneUse()) {
SetCondInst *I = cast<SetCondInst>(BI.getCondition());
std::string Name = I->getName(); I->setName("");
Instruction::BinaryOps NewOpcode = SetCondInst::getInverseCondition(Op);
Value *NewSCC = BinaryOperator::create(NewOpcode, X, Y, Name, I);
// Swap Destinations and condition...
BI.setCondition(NewSCC);
BI.setSuccessor(0, FalseDest);
BI.setSuccessor(1, TrueDest);
removeFromWorkList(I);
I->getParent()->getInstList().erase(I);
WorkList.push_back(cast<Instruction>(NewSCC));
return &BI;
}
return 0;
}
Instruction *InstCombiner::visitSwitchInst(SwitchInst &SI) {
Value *Cond = SI.getCondition();
if (Instruction *I = dyn_cast<Instruction>(Cond)) {
if (I->getOpcode() == Instruction::Add)
if (ConstantInt *AddRHS = dyn_cast<ConstantInt>(I->getOperand(1))) {
// change 'switch (X+4) case 1:' into 'switch (X) case -3'
for (unsigned i = 2, e = SI.getNumOperands(); i != e; i += 2)
SI.setOperand(i,ConstantExpr::getSub(cast<Constant>(SI.getOperand(i)),
AddRHS));
SI.setOperand(0, I->getOperand(0));
WorkList.push_back(I);
return &SI;
}
}
return 0;
}
/// CheapToScalarize - Return true if the value is cheaper to scalarize than it
/// is to leave as a vector operation.
static bool CheapToScalarize(Value *V, bool isConstant) {
if (isa<ConstantAggregateZero>(V))
return true;
if (ConstantPacked *C = dyn_cast<ConstantPacked>(V)) {
if (isConstant) return true;
// If all elts are the same, we can extract.
Constant *Op0 = C->getOperand(0);
for (unsigned i = 1; i < C->getNumOperands(); ++i)
if (C->getOperand(i) != Op0)
return false;
return true;
}
Instruction *I = dyn_cast<Instruction>(V);
if (!I) return false;
// Insert element gets simplified to the inserted element or is deleted if
// this is constant idx extract element and its a constant idx insertelt.
if (I->getOpcode() == Instruction::InsertElement && isConstant &&
isa<ConstantInt>(I->getOperand(2)))
return true;
if (I->getOpcode() == Instruction::Load && I->hasOneUse())
return true;
if (BinaryOperator *BO = dyn_cast<BinaryOperator>(I))
if (BO->hasOneUse() &&
(CheapToScalarize(BO->getOperand(0), isConstant) ||
CheapToScalarize(BO->getOperand(1), isConstant)))
return true;
return false;
}
/// getShuffleMask - Read and decode a shufflevector mask. It turns undef
/// elements into values that are larger than the #elts in the input.
static std::vector<unsigned> getShuffleMask(const ShuffleVectorInst *SVI) {
unsigned NElts = SVI->getType()->getNumElements();
if (isa<ConstantAggregateZero>(SVI->getOperand(2)))
return std::vector<unsigned>(NElts, 0);
if (isa<UndefValue>(SVI->getOperand(2)))
return std::vector<unsigned>(NElts, 2*NElts);
std::vector<unsigned> Result;
const ConstantPacked *CP = cast<ConstantPacked>(SVI->getOperand(2));
for (unsigned i = 0, e = CP->getNumOperands(); i != e; ++i)
if (isa<UndefValue>(CP->getOperand(i)))
Result.push_back(NElts*2); // undef -> 8
else
Result.push_back(cast<ConstantInt>(CP->getOperand(i))->getZExtValue());
return Result;
}
/// FindScalarElement - Given a vector and an element number, see if the scalar
/// value is already around as a register, for example if it were inserted then
/// extracted from the vector.
static Value *FindScalarElement(Value *V, unsigned EltNo) {
assert(isa<PackedType>(V->getType()) && "Not looking at a vector?");
const PackedType *PTy = cast<PackedType>(V->getType());
unsigned Width = PTy->getNumElements();
if (EltNo >= Width) // Out of range access.
return UndefValue::get(PTy->getElementType());
if (isa<UndefValue>(V))
return UndefValue::get(PTy->getElementType());
else if (isa<ConstantAggregateZero>(V))
return Constant::getNullValue(PTy->getElementType());
else if (ConstantPacked *CP = dyn_cast<ConstantPacked>(V))
return CP->getOperand(EltNo);
else if (InsertElementInst *III = dyn_cast<InsertElementInst>(V)) {
// If this is an insert to a variable element, we don't know what it is.
if (!isa<ConstantInt>(III->getOperand(2)))
return 0;
unsigned IIElt = cast<ConstantInt>(III->getOperand(2))->getZExtValue();
// If this is an insert to the element we are looking for, return the
// inserted value.
if (EltNo == IIElt)
return III->getOperand(1);
// Otherwise, the insertelement doesn't modify the value, recurse on its
// vector input.
return FindScalarElement(III->getOperand(0), EltNo);
} else if (ShuffleVectorInst *SVI = dyn_cast<ShuffleVectorInst>(V)) {
unsigned InEl = getShuffleMask(SVI)[EltNo];
if (InEl < Width)
return FindScalarElement(SVI->getOperand(0), InEl);
else if (InEl < Width*2)
return FindScalarElement(SVI->getOperand(1), InEl - Width);
else
return UndefValue::get(PTy->getElementType());
}
// Otherwise, we don't know.
return 0;
}
Instruction *InstCombiner::visitExtractElementInst(ExtractElementInst &EI) {
// If packed val is undef, replace extract with scalar undef.
if (isa<UndefValue>(EI.getOperand(0)))
return ReplaceInstUsesWith(EI, UndefValue::get(EI.getType()));
// If packed val is constant 0, replace extract with scalar 0.
if (isa<ConstantAggregateZero>(EI.getOperand(0)))
return ReplaceInstUsesWith(EI, Constant::getNullValue(EI.getType()));
if (ConstantPacked *C = dyn_cast<ConstantPacked>(EI.getOperand(0))) {
// If packed val is constant with uniform operands, replace EI
// with that operand
Constant *op0 = C->getOperand(0);
for (unsigned i = 1; i < C->getNumOperands(); ++i)
if (C->getOperand(i) != op0) {
op0 = 0;
break;
}
if (op0)
return ReplaceInstUsesWith(EI, op0);
}
// If extracting a specified index from the vector, see if we can recursively
// find a previously computed scalar that was inserted into the vector.
if (ConstantInt *IdxC = dyn_cast<ConstantInt>(EI.getOperand(1))) {
// This instruction only demands the single element from the input vector.
// If the input vector has a single use, simplify it based on this use
// property.
uint64_t IndexVal = IdxC->getZExtValue();
if (EI.getOperand(0)->hasOneUse()) {
uint64_t UndefElts;
if (Value *V = SimplifyDemandedVectorElts(EI.getOperand(0),
1 << IndexVal,
UndefElts)) {
EI.setOperand(0, V);
return &EI;
}
}
if (Value *Elt = FindScalarElement(EI.getOperand(0), IndexVal))
return ReplaceInstUsesWith(EI, Elt);
}
if (Instruction *I = dyn_cast<Instruction>(EI.getOperand(0))) {
if (I->hasOneUse()) {
// Push extractelement into predecessor operation if legal and
// profitable to do so
if (BinaryOperator *BO = dyn_cast<BinaryOperator>(I)) {
bool isConstantElt = isa<ConstantInt>(EI.getOperand(1));
if (CheapToScalarize(BO, isConstantElt)) {
ExtractElementInst *newEI0 =
new ExtractElementInst(BO->getOperand(0), EI.getOperand(1),
EI.getName()+".lhs");
ExtractElementInst *newEI1 =
new ExtractElementInst(BO->getOperand(1), EI.getOperand(1),
EI.getName()+".rhs");
InsertNewInstBefore(newEI0, EI);
InsertNewInstBefore(newEI1, EI);
return BinaryOperator::create(BO->getOpcode(), newEI0, newEI1);
}
} else if (isa<LoadInst>(I)) {
Value *Ptr = InsertCastBefore(I->getOperand(0),
PointerType::get(EI.getType()), EI);
GetElementPtrInst *GEP =
new GetElementPtrInst(Ptr, EI.getOperand(1),
I->getName() + ".gep");
InsertNewInstBefore(GEP, EI);
return new LoadInst(GEP);
}
}
if (InsertElementInst *IE = dyn_cast<InsertElementInst>(I)) {
// Extracting the inserted element?
if (IE->getOperand(2) == EI.getOperand(1))
return ReplaceInstUsesWith(EI, IE->getOperand(1));
// If the inserted and extracted elements are constants, they must not
// be the same value, extract from the pre-inserted value instead.
if (isa<Constant>(IE->getOperand(2)) &&
isa<Constant>(EI.getOperand(1))) {
AddUsesToWorkList(EI);
EI.setOperand(0, IE->getOperand(0));
return &EI;
}
} else if (ShuffleVectorInst *SVI = dyn_cast<ShuffleVectorInst>(I)) {
// If this is extracting an element from a shufflevector, figure out where
// it came from and extract from the appropriate input element instead.
if (ConstantInt *Elt = dyn_cast<ConstantInt>(EI.getOperand(1))) {
unsigned SrcIdx = getShuffleMask(SVI)[Elt->getZExtValue()];
Value *Src;
if (SrcIdx < SVI->getType()->getNumElements())
Src = SVI->getOperand(0);
else if (SrcIdx < SVI->getType()->getNumElements()*2) {
SrcIdx -= SVI->getType()->getNumElements();
Src = SVI->getOperand(1);
} else {
return ReplaceInstUsesWith(EI, UndefValue::get(EI.getType()));
}
return new ExtractElementInst(Src, SrcIdx);
}
}
}
return 0;
}
/// CollectSingleShuffleElements - If V is a shuffle of values that ONLY returns
/// elements from either LHS or RHS, return the shuffle mask and true.
/// Otherwise, return false.
static bool CollectSingleShuffleElements(Value *V, Value *LHS, Value *RHS,
std::vector<Constant*> &Mask) {
assert(V->getType() == LHS->getType() && V->getType() == RHS->getType() &&
"Invalid CollectSingleShuffleElements");
unsigned NumElts = cast<PackedType>(V->getType())->getNumElements();
if (isa<UndefValue>(V)) {
Mask.assign(NumElts, UndefValue::get(Type::UIntTy));
return true;
} else if (V == LHS) {
for (unsigned i = 0; i != NumElts; ++i)
Mask.push_back(ConstantInt::get(Type::UIntTy, i));
return true;
} else if (V == RHS) {
for (unsigned i = 0; i != NumElts; ++i)
Mask.push_back(ConstantInt::get(Type::UIntTy, i+NumElts));
return true;
} else if (InsertElementInst *IEI = dyn_cast<InsertElementInst>(V)) {
// If this is an insert of an extract from some other vector, include it.
Value *VecOp = IEI->getOperand(0);
Value *ScalarOp = IEI->getOperand(1);
Value *IdxOp = IEI->getOperand(2);
if (!isa<ConstantInt>(IdxOp))
return false;
unsigned InsertedIdx = cast<ConstantInt>(IdxOp)->getZExtValue();
if (isa<UndefValue>(ScalarOp)) { // inserting undef into vector.
// Okay, we can handle this if the vector we are insertinting into is
// transitively ok.
if (CollectSingleShuffleElements(VecOp, LHS, RHS, Mask)) {
// If so, update the mask to reflect the inserted undef.
Mask[InsertedIdx] = UndefValue::get(Type::UIntTy);
return true;
}
} else if (ExtractElementInst *EI = dyn_cast<ExtractElementInst>(ScalarOp)){
if (isa<ConstantInt>(EI->getOperand(1)) &&
EI->getOperand(0)->getType() == V->getType()) {
unsigned ExtractedIdx =
cast<ConstantInt>(EI->getOperand(1))->getZExtValue();
// This must be extracting from either LHS or RHS.
if (EI->getOperand(0) == LHS || EI->getOperand(0) == RHS) {
// Okay, we can handle this if the vector we are insertinting into is
// transitively ok.
if (CollectSingleShuffleElements(VecOp, LHS, RHS, Mask)) {
// If so, update the mask to reflect the inserted value.
if (EI->getOperand(0) == LHS) {
Mask[InsertedIdx & (NumElts-1)] =
ConstantInt::get(Type::UIntTy, ExtractedIdx);
} else {
assert(EI->getOperand(0) == RHS);
Mask[InsertedIdx & (NumElts-1)] =
ConstantInt::get(Type::UIntTy, ExtractedIdx+NumElts);
}
return true;
}
}
}
}
}
// TODO: Handle shufflevector here!
return false;
}
/// CollectShuffleElements - We are building a shuffle of V, using RHS as the
/// RHS of the shuffle instruction, if it is not null. Return a shuffle mask
/// that computes V and the LHS value of the shuffle.
static Value *CollectShuffleElements(Value *V, std::vector<Constant*> &Mask,
Value *&RHS) {
assert(isa<PackedType>(V->getType()) &&
(RHS == 0 || V->getType() == RHS->getType()) &&
"Invalid shuffle!");
unsigned NumElts = cast<PackedType>(V->getType())->getNumElements();
if (isa<UndefValue>(V)) {
Mask.assign(NumElts, UndefValue::get(Type::UIntTy));
return V;
} else if (isa<ConstantAggregateZero>(V)) {
Mask.assign(NumElts, ConstantInt::get(Type::UIntTy, 0));
return V;
} else if (InsertElementInst *IEI = dyn_cast<InsertElementInst>(V)) {
// If this is an insert of an extract from some other vector, include it.
Value *VecOp = IEI->getOperand(0);
Value *ScalarOp = IEI->getOperand(1);
Value *IdxOp = IEI->getOperand(2);
if (ExtractElementInst *EI = dyn_cast<ExtractElementInst>(ScalarOp)) {
if (isa<ConstantInt>(EI->getOperand(1)) && isa<ConstantInt>(IdxOp) &&
EI->getOperand(0)->getType() == V->getType()) {
unsigned ExtractedIdx =
cast<ConstantInt>(EI->getOperand(1))->getZExtValue();
unsigned InsertedIdx = cast<ConstantInt>(IdxOp)->getZExtValue();
// Either the extracted from or inserted into vector must be RHSVec,
// otherwise we'd end up with a shuffle of three inputs.
if (EI->getOperand(0) == RHS || RHS == 0) {
RHS = EI->getOperand(0);
Value *V = CollectShuffleElements(VecOp, Mask, RHS);
Mask[InsertedIdx & (NumElts-1)] =
ConstantInt::get(Type::UIntTy, NumElts+ExtractedIdx);
return V;
}
if (VecOp == RHS) {
Value *V = CollectShuffleElements(EI->getOperand(0), Mask, RHS);
// Everything but the extracted element is replaced with the RHS.
for (unsigned i = 0; i != NumElts; ++i) {
if (i != InsertedIdx)
Mask[i] = ConstantInt::get(Type::UIntTy, NumElts+i);
}
return V;
}
// If this insertelement is a chain that comes from exactly these two
// vectors, return the vector and the effective shuffle.
if (CollectSingleShuffleElements(IEI, EI->getOperand(0), RHS, Mask))
return EI->getOperand(0);
}
}
}
// TODO: Handle shufflevector here!
// Otherwise, can't do anything fancy. Return an identity vector.
for (unsigned i = 0; i != NumElts; ++i)
Mask.push_back(ConstantInt::get(Type::UIntTy, i));
return V;
}
Instruction *InstCombiner::visitInsertElementInst(InsertElementInst &IE) {
Value *VecOp = IE.getOperand(0);
Value *ScalarOp = IE.getOperand(1);
Value *IdxOp = IE.getOperand(2);
// If the inserted element was extracted from some other vector, and if the
// indexes are constant, try to turn this into a shufflevector operation.
if (ExtractElementInst *EI = dyn_cast<ExtractElementInst>(ScalarOp)) {
if (isa<ConstantInt>(EI->getOperand(1)) && isa<ConstantInt>(IdxOp) &&
EI->getOperand(0)->getType() == IE.getType()) {
unsigned NumVectorElts = IE.getType()->getNumElements();
unsigned ExtractedIdx=cast<ConstantInt>(EI->getOperand(1))->getZExtValue();
unsigned InsertedIdx = cast<ConstantInt>(IdxOp)->getZExtValue();
if (ExtractedIdx >= NumVectorElts) // Out of range extract.
return ReplaceInstUsesWith(IE, VecOp);
if (InsertedIdx >= NumVectorElts) // Out of range insert.
return ReplaceInstUsesWith(IE, UndefValue::get(IE.getType()));
// If we are extracting a value from a vector, then inserting it right
// back into the same place, just use the input vector.
if (EI->getOperand(0) == VecOp && ExtractedIdx == InsertedIdx)
return ReplaceInstUsesWith(IE, VecOp);
// We could theoretically do this for ANY input. However, doing so could
// turn chains of insertelement instructions into a chain of shufflevector
// instructions, and right now we do not merge shufflevectors. As such,
// only do this in a situation where it is clear that there is benefit.
if (isa<UndefValue>(VecOp) || isa<ConstantAggregateZero>(VecOp)) {
// Turn this into shuffle(EIOp0, VecOp, Mask). The result has all of
// the values of VecOp, except then one read from EIOp0.
// Build a new shuffle mask.
std::vector<Constant*> Mask;
if (isa<UndefValue>(VecOp))
Mask.assign(NumVectorElts, UndefValue::get(Type::UIntTy));
else {
assert(isa<ConstantAggregateZero>(VecOp) && "Unknown thing");
Mask.assign(NumVectorElts, ConstantInt::get(Type::UIntTy,
NumVectorElts));
}
Mask[InsertedIdx] = ConstantInt::get(Type::UIntTy, ExtractedIdx);
return new ShuffleVectorInst(EI->getOperand(0), VecOp,
ConstantPacked::get(Mask));
}
// If this insertelement isn't used by some other insertelement, turn it
// (and any insertelements it points to), into one big shuffle.
if (!IE.hasOneUse() || !isa<InsertElementInst>(IE.use_back())) {
std::vector<Constant*> Mask;
Value *RHS = 0;
Value *LHS = CollectShuffleElements(&IE, Mask, RHS);
if (RHS == 0) RHS = UndefValue::get(LHS->getType());
// We now have a shuffle of LHS, RHS, Mask.
return new ShuffleVectorInst(LHS, RHS, ConstantPacked::get(Mask));
}
}
}
return 0;
}
Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) {
Value *LHS = SVI.getOperand(0);
Value *RHS = SVI.getOperand(1);
std::vector<unsigned> Mask = getShuffleMask(&SVI);
bool MadeChange = false;
// Undefined shuffle mask -> undefined value.
if (isa<UndefValue>(SVI.getOperand(2)))
return ReplaceInstUsesWith(SVI, UndefValue::get(SVI.getType()));
// TODO: If we have shuffle(x, undef, mask) and any elements of mask refer to
// the undef, change them to undefs.
// Canonicalize shuffle(x ,x,mask) -> shuffle(x, undef,mask')
// Canonicalize shuffle(undef,x,mask) -> shuffle(x, undef,mask').
if (LHS == RHS || isa<UndefValue>(LHS)) {
if (isa<UndefValue>(LHS) && LHS == RHS) {
// shuffle(undef,undef,mask) -> undef.
return ReplaceInstUsesWith(SVI, LHS);
}
// Remap any references to RHS to use LHS.
std::vector<Constant*> Elts;
for (unsigned i = 0, e = Mask.size(); i != e; ++i) {
if (Mask[i] >= 2*e)
Elts.push_back(UndefValue::get(Type::UIntTy));
else {
if ((Mask[i] >= e && isa<UndefValue>(RHS)) ||
(Mask[i] < e && isa<UndefValue>(LHS)))
Mask[i] = 2*e; // Turn into undef.
else
Mask[i] &= (e-1); // Force to LHS.
Elts.push_back(ConstantInt::get(Type::UIntTy, Mask[i]));
}
}
SVI.setOperand(0, SVI.getOperand(1));
SVI.setOperand(1, UndefValue::get(RHS->getType()));
SVI.setOperand(2, ConstantPacked::get(Elts));
LHS = SVI.getOperand(0);
RHS = SVI.getOperand(1);
MadeChange = true;
}
// Analyze the shuffle, are the LHS or RHS and identity shuffles?
bool isLHSID = true, isRHSID = true;
for (unsigned i = 0, e = Mask.size(); i != e; ++i) {
if (Mask[i] >= e*2) continue; // Ignore undef values.
// Is this an identity shuffle of the LHS value?
isLHSID &= (Mask[i] == i);
// Is this an identity shuffle of the RHS value?
isRHSID &= (Mask[i]-e == i);
}
// Eliminate identity shuffles.
if (isLHSID) return ReplaceInstUsesWith(SVI, LHS);
if (isRHSID) return ReplaceInstUsesWith(SVI, RHS);
// If the LHS is a shufflevector itself, see if we can combine it with this
// one without producing an unusual shuffle. Here we are really conservative:
// we are absolutely afraid of producing a shuffle mask not in the input
// program, because the code gen may not be smart enough to turn a merged
// shuffle into two specific shuffles: it may produce worse code. As such,
// we only merge two shuffles if the result is one of the two input shuffle
// masks. In this case, merging the shuffles just removes one instruction,
// which we know is safe. This is good for things like turning:
// (splat(splat)) -> splat.
if (ShuffleVectorInst *LHSSVI = dyn_cast<ShuffleVectorInst>(LHS)) {
if (isa<UndefValue>(RHS)) {
std::vector<unsigned> LHSMask = getShuffleMask(LHSSVI);
std::vector<unsigned> NewMask;
for (unsigned i = 0, e = Mask.size(); i != e; ++i)
if (Mask[i] >= 2*e)
NewMask.push_back(2*e);
else
NewMask.push_back(LHSMask[Mask[i]]);
// If the result mask is equal to the src shuffle or this shuffle mask, do
// the replacement.
if (NewMask == LHSMask || NewMask == Mask) {
std::vector<Constant*> Elts;
for (unsigned i = 0, e = NewMask.size(); i != e; ++i) {
if (NewMask[i] >= e*2) {
Elts.push_back(UndefValue::get(Type::UIntTy));
} else {
Elts.push_back(ConstantInt::get(Type::UIntTy, NewMask[i]));
}
}
return new ShuffleVectorInst(LHSSVI->getOperand(0),
LHSSVI->getOperand(1),
ConstantPacked::get(Elts));
}
}
}
return MadeChange ? &SVI : 0;
}
void InstCombiner::removeFromWorkList(Instruction *I) {
WorkList.erase(std::remove(WorkList.begin(), WorkList.end(), I),
WorkList.end());
}
/// TryToSinkInstruction - Try to move the specified instruction from its
/// current block into the beginning of DestBlock, which can only happen if it's
/// safe to move the instruction past all of the instructions between it and the
/// end of its block.
static bool TryToSinkInstruction(Instruction *I, BasicBlock *DestBlock) {
assert(I->hasOneUse() && "Invariants didn't hold!");
// Cannot move control-flow-involving, volatile loads, vaarg, etc.
if (isa<PHINode>(I) || I->mayWriteToMemory()) return false;
// Do not sink alloca instructions out of the entry block.
if (isa<AllocaInst>(I) && I->getParent() == &DestBlock->getParent()->front())
return false;
// We can only sink load instructions if there is nothing between the load and
// the end of block that could change the value.
if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
for (BasicBlock::iterator Scan = LI, E = LI->getParent()->end();
Scan != E; ++Scan)
if (Scan->mayWriteToMemory())
return false;
}
BasicBlock::iterator InsertPos = DestBlock->begin();
while (isa<PHINode>(InsertPos)) ++InsertPos;
I->moveBefore(InsertPos);
++NumSunkInst;
return true;
}
/// OptimizeConstantExpr - Given a constant expression and target data layout
/// information, symbolically evaluation the constant expr to something simpler
/// if possible.
static Constant *OptimizeConstantExpr(ConstantExpr *CE, const TargetData *TD) {
if (!TD) return CE;
Constant *Ptr = CE->getOperand(0);
if (CE->getOpcode() == Instruction::GetElementPtr && Ptr->isNullValue() &&
cast<PointerType>(Ptr->getType())->getElementType()->isSized()) {
// If this is a constant expr gep that is effectively computing an
// "offsetof", fold it into 'cast int Size to T*' instead of 'gep 0, 0, 12'
bool isFoldableGEP = true;
for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i)
if (!isa<ConstantInt>(CE->getOperand(i)))
isFoldableGEP = false;
if (isFoldableGEP) {
std::vector<Value*> Ops(CE->op_begin()+1, CE->op_end());
uint64_t Offset = TD->getIndexedOffset(Ptr->getType(), Ops);
Constant *C = ConstantInt::get(Type::ULongTy, Offset);
C = ConstantExpr::getCast(C, TD->getIntPtrType());
return ConstantExpr::getCast(C, CE->getType());
}
}
return CE;
}
/// AddReachableCodeToWorklist - Walk the function in depth-first order, adding
/// all reachable code to the worklist.
///
/// This has a couple of tricks to make the code faster and more powerful. In
/// particular, we constant fold and DCE instructions as we go, to avoid adding
/// them to the worklist (this significantly speeds up instcombine on code where
/// many instructions are dead or constant). Additionally, if we find a branch
/// whose condition is a known constant, we only visit the reachable successors.
///
static void AddReachableCodeToWorklist(BasicBlock *BB,
std::set<BasicBlock*> &Visited,
std::vector<Instruction*> &WorkList,
const TargetData *TD) {
// We have now visited this block! If we've already been here, bail out.
if (!Visited.insert(BB).second) return;
for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E; ) {
Instruction *Inst = BBI++;
// DCE instruction if trivially dead.
if (isInstructionTriviallyDead(Inst)) {
++NumDeadInst;
DEBUG(std::cerr << "IC: DCE: " << *Inst);
Inst->eraseFromParent();
continue;
}
// ConstantProp instruction if trivially constant.
if (Constant *C = ConstantFoldInstruction(Inst)) {
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
C = OptimizeConstantExpr(CE, TD);
DEBUG(std::cerr << "IC: ConstFold to: " << *C << " from: " << *Inst);
Inst->replaceAllUsesWith(C);
++NumConstProp;
Inst->eraseFromParent();
continue;
}
WorkList.push_back(Inst);
}
// Recursively visit successors. If this is a branch or switch on a constant,
// only visit the reachable successor.
TerminatorInst *TI = BB->getTerminator();
if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
if (BI->isConditional() && isa<ConstantBool>(BI->getCondition())) {
bool CondVal = cast<ConstantBool>(BI->getCondition())->getValue();
AddReachableCodeToWorklist(BI->getSuccessor(!CondVal), Visited, WorkList,
TD);
return;
}
} else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
if (ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition())) {
// See if this is an explicit destination.
for (unsigned i = 1, e = SI->getNumSuccessors(); i != e; ++i)
if (SI->getCaseValue(i) == Cond) {
AddReachableCodeToWorklist(SI->getSuccessor(i), Visited, WorkList,TD);
return;
}
// Otherwise it is the default destination.
AddReachableCodeToWorklist(SI->getSuccessor(0), Visited, WorkList, TD);
return;
}
}
for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
AddReachableCodeToWorklist(TI->getSuccessor(i), Visited, WorkList, TD);
}
bool InstCombiner::runOnFunction(Function &F) {
bool Changed = false;
TD = &getAnalysis<TargetData>();
{
// Do a depth-first traversal of the function, populate the worklist with
// the reachable instructions. Ignore blocks that are not reachable. Keep
// track of which blocks we visit.
std::set<BasicBlock*> Visited;
AddReachableCodeToWorklist(F.begin(), Visited, WorkList, TD);
// Do a quick scan over the function. If we find any blocks that are
// unreachable, remove any instructions inside of them. This prevents
// the instcombine code from having to deal with some bad special cases.
for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
if (!Visited.count(BB)) {
Instruction *Term = BB->getTerminator();
while (Term != BB->begin()) { // Remove instrs bottom-up
BasicBlock::iterator I = Term; --I;
DEBUG(std::cerr << "IC: DCE: " << *I);
++NumDeadInst;
if (!I->use_empty())
I->replaceAllUsesWith(UndefValue::get(I->getType()));
I->eraseFromParent();
}
}
}
while (!WorkList.empty()) {
Instruction *I = WorkList.back(); // Get an instruction from the worklist
WorkList.pop_back();
// Check to see if we can DCE the instruction.
if (isInstructionTriviallyDead(I)) {
// Add operands to the worklist.
if (I->getNumOperands() < 4)
AddUsesToWorkList(*I);
++NumDeadInst;
DEBUG(std::cerr << "IC: DCE: " << *I);
I->eraseFromParent();
removeFromWorkList(I);
continue;
}
// Instruction isn't dead, see if we can constant propagate it.
if (Constant *C = ConstantFoldInstruction(I)) {
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
C = OptimizeConstantExpr(CE, TD);
DEBUG(std::cerr << "IC: ConstFold to: " << *C << " from: " << *I);
// Add operands to the worklist.
AddUsesToWorkList(*I);
ReplaceInstUsesWith(*I, C);
++NumConstProp;
I->eraseFromParent();
removeFromWorkList(I);
continue;
}
// See if we can trivially sink this instruction to a successor basic block.
if (I->hasOneUse()) {
BasicBlock *BB = I->getParent();
BasicBlock *UserParent = cast<Instruction>(I->use_back())->getParent();
if (UserParent != BB) {
bool UserIsSuccessor = false;
// See if the user is one of our successors.
for (succ_iterator SI = succ_begin(BB), E = succ_end(BB); SI != E; ++SI)
if (*SI == UserParent) {
UserIsSuccessor = true;
break;
}
// If the user is one of our immediate successors, and if that successor
// only has us as a predecessors (we'd have to split the critical edge
// otherwise), we can keep going.
if (UserIsSuccessor && !isa<PHINode>(I->use_back()) &&
next(pred_begin(UserParent)) == pred_end(UserParent))
// Okay, the CFG is simple enough, try to sink this instruction.
Changed |= TryToSinkInstruction(I, UserParent);
}
}
// Now that we have an instruction, try combining it to simplify it...
if (Instruction *Result = visit(*I)) {
++NumCombined;
// Should we replace the old instruction with a new one?
if (Result != I) {
DEBUG(std::cerr << "IC: Old = " << *I
<< " New = " << *Result);
// Everything uses the new instruction now.
I->replaceAllUsesWith(Result);
// Push the new instruction and any users onto the worklist.
WorkList.push_back(Result);
AddUsersToWorkList(*Result);
// Move the name to the new instruction first...
std::string OldName = I->getName(); I->setName("");
Result->setName(OldName);
// Insert the new instruction into the basic block...
BasicBlock *InstParent = I->getParent();
BasicBlock::iterator InsertPos = I;
if (!isa<PHINode>(Result)) // If combining a PHI, don't insert
while (isa<PHINode>(InsertPos)) // middle of a block of PHIs.
++InsertPos;
InstParent->getInstList().insert(InsertPos, Result);
// Make sure that we reprocess all operands now that we reduced their
// use counts.
for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
if (Instruction *OpI = dyn_cast<Instruction>(I->getOperand(i)))
WorkList.push_back(OpI);
// Instructions can end up on the worklist more than once. Make sure
// we do not process an instruction that has been deleted.
removeFromWorkList(I);
// Erase the old instruction.
InstParent->getInstList().erase(I);
} else {
DEBUG(std::cerr << "IC: MOD = " << *I);
// If the instruction was modified, it's possible that it is now dead.
// if so, remove it.
if (isInstructionTriviallyDead(I)) {
// Make sure we process all operands now that we are reducing their
// use counts.
for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
if (Instruction *OpI = dyn_cast<Instruction>(I->getOperand(i)))
WorkList.push_back(OpI);
// Instructions may end up in the worklist more than once. Erase all
// occurrences of this instruction.
removeFromWorkList(I);
I->eraseFromParent();
} else {
WorkList.push_back(Result);
AddUsersToWorkList(*Result);
}
}
Changed = true;
}
}
return Changed;
}
FunctionPass *llvm::createInstructionCombiningPass() {
return new InstCombiner();
}
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