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llvm-6502/lib/Transforms/Scalar/InstructionCombining.cpp
Nate Begeman 14b0529532 Add support alignment of allocation instructions. 
Add support for specifying alignment and size of setjmp jmpbufs.

No targets currently do anything with this information, nor is it presrved
in the bytecode representation.  That's coming up next.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@24196 91177308-0d34-0410-b5e6-96231b3b80d8
2005-11-05 09:21:28 +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/ADT/DepthFirstIterator.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/STLExtras.h"
#include <algorithm>
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<> NumSunkInst ("instcombine", "Number of instructions sunk");
class 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(Instruction &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);
}
// 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.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 *visitDiv(BinaryOperator &I);
Instruction *visitRem(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 *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);
// 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;
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;
}
}
// 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);
// 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 *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);
};
RegisterOpt<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;
}
// 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)));
}
/// MaskedValueIsZero - Return true if 'V & Mask' is known to be zero. We use
/// this predicate to simplify operations downstream. V and Mask are known to
/// be the same type.
static bool MaskedValueIsZero(Value *V, ConstantIntegral *Mask,
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
// to to 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 (Mask->isNullValue())
return true;
if (ConstantIntegral *CI = dyn_cast<ConstantIntegral>(V))
return ConstantExpr::getAnd(CI, Mask)->isNullValue();
if (Depth == 6) return false; // Limit search depth.
if (Instruction *I = dyn_cast<Instruction>(V)) {
switch (I->getOpcode()) {
case Instruction::And:
// (X & C1) & C2 == 0 iff C1 & C2 == 0.
if (ConstantIntegral *CI = dyn_cast<ConstantIntegral>(I->getOperand(1))) {
ConstantIntegral *C1C2 =
cast<ConstantIntegral>(ConstantExpr::getAnd(CI, Mask));
if (MaskedValueIsZero(I->getOperand(0), C1C2, Depth+1))
return true;
}
// If either the LHS or the RHS are MaskedValueIsZero, the result is zero.
return MaskedValueIsZero(I->getOperand(1), Mask, Depth+1) ||
MaskedValueIsZero(I->getOperand(0), Mask, Depth+1);
case Instruction::Or:
case Instruction::Xor:
// If the LHS and the RHS are MaskedValueIsZero, the result is also zero.
return MaskedValueIsZero(I->getOperand(1), Mask, Depth+1) &&
MaskedValueIsZero(I->getOperand(0), Mask, Depth+1);
case Instruction::Select:
// If the T and F values are MaskedValueIsZero, the result is also zero.
return MaskedValueIsZero(I->getOperand(2), Mask, Depth+1) &&
MaskedValueIsZero(I->getOperand(1), Mask, Depth+1);
case Instruction::Cast: {
const Type *SrcTy = I->getOperand(0)->getType();
if (SrcTy == Type::BoolTy)
return (Mask->getRawValue() & 1) == 0;
if (SrcTy->isInteger()) {
// (cast <ty> X to int) & C2 == 0 iff <ty> could not have contained C2.
if (SrcTy->isUnsigned() && // Only handle zero ext.
ConstantExpr::getCast(Mask, SrcTy)->isNullValue())
return true;
// If this is a noop cast, recurse.
if ((SrcTy->isSigned() && SrcTy->getUnsignedVersion() == I->getType())||
SrcTy->getSignedVersion() == I->getType()) {
Constant *NewMask =
ConstantExpr::getCast(Mask, I->getOperand(0)->getType());
return MaskedValueIsZero(I->getOperand(0),
cast<ConstantIntegral>(NewMask), Depth+1);
}
}
break;
}
case Instruction::Shl:
// (shl X, C1) & C2 == 0 iff (X & C2 >>u C1) == 0
if (ConstantUInt *SA = dyn_cast<ConstantUInt>(I->getOperand(1)))
return MaskedValueIsZero(I->getOperand(0),
cast<ConstantIntegral>(ConstantExpr::getUShr(Mask, SA)),
Depth+1);
break;
case Instruction::Shr:
// (ushr X, C1) & C2 == 0 iff (-1 >> C1) & C2 == 0
if (ConstantUInt *SA = dyn_cast<ConstantUInt>(I->getOperand(1)))
if (I->getType()->isUnsigned()) {
Constant *C1 = ConstantIntegral::getAllOnesValue(I->getType());
C1 = ConstantExpr::getShr(C1, SA);
C1 = ConstantExpr::getAnd(C1, Mask);
if (C1->isNullValue())
return true;
}
break;
}
}
return false;
}
// 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 ||
!isa<Constant>(PN->getIncomingValue(0))) return 0;
// Check to see if all of the operands of the PHI are constants. If not, we
// cannot do the transformation.
for (unsigned i = 1; i != NumPHIValues; ++i)
if (!isa<Constant>(PN->getIncomingValue(i)))
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) {
Constant *InV = cast<Constant>(PN->getIncomingValue(i));
NewPN->addIncoming(ConstantExpr::get(I.getOpcode(), InV, C),
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) {
Constant *InV = cast<Constant>(PN->getIncomingValue(i));
NewPN->addIncoming(ConstantExpr::getCast(InV, RetTy),
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)) {
unsigned NumBits = CI->getType()->getPrimitiveSizeInBits();
uint64_t Val = CI->getRawValue() & (~0ULL >> (64- NumBits));
if (Val == (1ULL << (NumBits-1)))
return BinaryOperator::createXor(LHS, RHS);
}
if (isa<PHINode>(LHS))
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
ConstantInt *XorRHS;
Value *XorLHS;
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.
Constant *Mask = ConstantInt::getAllOnesValue(XorLHS->getType());
Mask = ConstantExpr::getShl(Mask,
ConstantInt::get(Type::UByteTy, 64-TySizeBits-Size));
if (!MaskedValueIsZero(XorLHS, cast<ConstantInt>(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;
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->getRawValue();
// Form a mask of all bits from the lowest bit added through the top.
uint64_t AddRHSHighBits = ~((AddRHSV & -AddRHSV)-1);
AddRHSHighBits &= ~0ULL >> (64-C2->getType()->getPrimitiveSizeInBits());
// See if the and mask includes all of these bits.
uint64_t AddRHSHighBitsAnd = AddRHSHighBits & C2->getRawValue();
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;
}
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->getRawValue() & (~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::Shr)
if (ConstantUInt *CU = dyn_cast<ConstantUInt>(SI->getOperand(1))) {
const Type *NewTy;
if (SI->getType()->isSigned())
NewTy = SI->getType()->getUnsignedVersion();
else
NewTy = SI->getType()->getSignedVersion();
// Check to see if we are shifting out everything but the sign bit.
if (CU->getValue() == SI->getType()->getPrimitiveSizeInBits()-1) {
// Ok, the transformation is safe. Insert a cast of the incoming
// value, then the new shift, then the new cast.
Instruction *FirstCast = new CastInst(SI->getOperand(0), NewTy,
SI->getOperand(0)->getName());
Value *InV = InsertNewInstBefore(FirstCast, I);
Instruction *NewShift = new ShiftInst(Instruction::Shr, FirstCast,
CU, SI->getName());
if (NewShift->getType() == I.getType())
return NewShift;
else {
InV = InsertNewInstBefore(NewShift, I);
return new CastInst(NewShift, I.getType());
}
}
}
}
// 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);
}
// -(X sdiv C) -> (X sdiv -C)
if (Op1I->getOpcode() == Instruction::Div)
if (ConstantSInt *CSI = dyn_cast<ConstantSInt>(Op0))
if (CSI->isNullValue())
if (Constant *DivRHS = dyn_cast<Constant>(Op1I->getOperand(1)))
return BinaryOperator::createDiv(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 {
ConstantUInt *RHSC = cast<ConstantUInt>(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->getValue() ==
1ULL << (RHS->getType()->getPrimitiveSizeInBits()-1);
if (Opcode == Instruction::SetGT)
return RHSC->getValue() ==
(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)->getRawValue();
if (isPowerOf2_64(Val)) { // Replace X*(2^C) with X << C
uint64_t C = Log2_64(Val);
return new ShiftInst(Instruction::Shl, Op0,
ConstantUInt::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'
}
// 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 = ConstantUInt::get(Type::UByteTy,
SCOpTy->getPrimitiveSizeInBits()-1);
if (SCIOp0->getType()->isUnsigned()) {
const Type *NewTy = SCIOp0->getType()->getSignedVersion();
SCIOp0 = InsertNewInstBefore(new CastInst(SCIOp0, NewTy,
SCIOp0->getName()), I);
}
Value *V =
InsertNewInstBefore(new ShiftInst(Instruction::Shr, 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 = InsertNewInstBefore(new CastInst(V, I.getType(), V->getName()),I);
Value *OtherOp = Op0 == BoolCast ? I.getOperand(1) : Op0;
return BinaryOperator::createAnd(V, OtherOp);
}
}
}
return Changed ? &I : 0;
}
Instruction *InstCombiner::visitDiv(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
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
if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) {
// div X, 1 == X
if (RHS->equalsInt(1))
return ReplaceInstUsesWith(I, Op0);
// div X, -1 == -X
if (RHS->isAllOnesValue())
return BinaryOperator::createNeg(Op0);
if (Instruction *LHS = dyn_cast<Instruction>(Op0))
if (LHS->getOpcode() == Instruction::Div)
if (ConstantInt *LHSRHS = dyn_cast<ConstantInt>(LHS->getOperand(1))) {
// (X / C1) / C2 -> X / (C1*C2)
return BinaryOperator::createDiv(LHS->getOperand(0),
ConstantExpr::getMul(RHS, LHSRHS));
}
// Check to see if this is an unsigned division with an exact power of 2,
// if so, convert to a right shift.
if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
if (uint64_t Val = C->getValue()) // Don't break X / 0
if (isPowerOf2_64(Val)) {
uint64_t C = Log2_64(Val);
return new ShiftInst(Instruction::Shr, Op0,
ConstantUInt::get(Type::UByteTy, C));
}
// -X/C -> X/-C
if (RHS->getType()->isSigned())
if (Value *LHSNeg = dyn_castNegVal(Op0))
return BinaryOperator::createDiv(LHSNeg, ConstantExpr::getNeg(RHS));
if (!RHS->isNullValue()) {
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 this is 'udiv X, (Cond ? C1, C2)' where C1&C2 are powers of two,
// transform this into: '(Cond ? (udiv X, C1) : (udiv X, C2))'.
if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
if (ConstantUInt *STO = dyn_cast<ConstantUInt>(SI->getOperand(1)))
if (ConstantUInt *SFO = dyn_cast<ConstantUInt>(SI->getOperand(2))) {
if (STO->getValue() == 0) { // Couldn't be this argument.
I.setOperand(1, SFO);
return &I;
} else if (SFO->getValue() == 0) {
I.setOperand(1, STO);
return &I;
}
uint64_t TVA = STO->getValue(), FVA = SFO->getValue();
if (isPowerOf2_64(TVA) && isPowerOf2_64(FVA)) {
unsigned TSA = Log2_64(TVA), FSA = Log2_64(FVA);
Constant *TC = ConstantUInt::get(Type::UByteTy, TSA);
Instruction *TSI = new ShiftInst(Instruction::Shr, Op0,
TC, SI->getName()+".t");
TSI = InsertNewInstBefore(TSI, I);
Constant *FC = ConstantUInt::get(Type::UByteTy, FSA);
Instruction *FSI = new ShiftInst(Instruction::Shr, Op0,
FC, SI->getName()+".f");
FSI = InsertNewInstBefore(FSI, I);
return new SelectInst(SI->getOperand(0), TSI, FSI);
}
}
// 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()));
if (I.getType()->isSigned()) {
// If the top bits of both operands are zero (i.e. we can prove they are
// unsigned inputs), turn this into a udiv.
ConstantIntegral *MaskV = ConstantSInt::getMinValue(I.getType());
if (MaskedValueIsZero(Op1, MaskV) && MaskedValueIsZero(Op0, MaskV)) {
const Type *NTy = Op0->getType()->getUnsignedVersion();
Instruction *LHS = new CastInst(Op0, NTy, Op0->getName());
InsertNewInstBefore(LHS, I);
Value *RHS;
if (Constant *R = dyn_cast<Constant>(Op1))
RHS = ConstantExpr::getCast(R, NTy);
else
RHS = InsertNewInstBefore(new CastInst(Op1, NTy, Op1->getName()), I);
Instruction *Div = BinaryOperator::createDiv(LHS, RHS, I.getName());
InsertNewInstBefore(Div, I);
return new CastInst(Div, I.getType());
}
}
return 0;
}
Instruction *InstCombiner::visitRem(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
if (I.getType()->isSigned()) {
if (Value *RHSNeg = dyn_castNegVal(Op1))
if (!isa<ConstantSInt>(RHSNeg) ||
cast<ConstantSInt>(RHSNeg)->getValue() > 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.
ConstantIntegral *MaskV = ConstantSInt::getMinValue(I.getType());
if (MaskedValueIsZero(Op1, MaskV) && MaskedValueIsZero(Op0, MaskV)) {
const Type *NTy = Op0->getType()->getUnsignedVersion();
Instruction *LHS = new CastInst(Op0, NTy, Op0->getName());
InsertNewInstBefore(LHS, I);
Value *RHS;
if (Constant *R = dyn_cast<Constant>(Op1))
RHS = ConstantExpr::getCast(R, NTy);
else
RHS = InsertNewInstBefore(new CastInst(Op1, NTy, Op1->getName()), I);
Instruction *Rem = BinaryOperator::createRem(LHS, RHS, I.getName());
InsertNewInstBefore(Rem, I);
return new CastInst(Rem, 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
if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) {
if (RHS->equalsInt(1)) // X % 1 == 0
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
// Check to see if this is an unsigned remainder with an exact power of 2,
// if so, convert to a bitwise and.
if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
if (uint64_t Val = C->getValue()) // Don't break X % 0 (divide by zero)
if (!(Val & (Val-1))) // Power of 2
return BinaryOperator::createAnd(Op0,
ConstantUInt::get(I.getType(), Val-1));
if (!RHS->isNullValue()) {
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 this is 'urem X, (Cond ? C1, C2)' where C1&C2 are powers of two,
// transform this into: '(Cond ? (urem X, C1) : (urem X, C2))'.
if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
if (ConstantUInt *STO = dyn_cast<ConstantUInt>(SI->getOperand(1)))
if (ConstantUInt *SFO = dyn_cast<ConstantUInt>(SI->getOperand(2))) {
if (STO->getValue() == 0) { // Couldn't be this argument.
I.setOperand(1, SFO);
return &I;
} else if (SFO->getValue() == 0) {
I.setOperand(1, STO);
return &I;
}
if (!(STO->getValue() & (STO->getValue()-1)) &&
!(SFO->getValue() & (SFO->getValue()-1))) {
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);
}
}
// 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;
}
// isMaxValueMinusOne - return true if this is Max-1
static bool isMaxValueMinusOne(const ConstantInt *C) {
if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C)) {
// Calculate -1 casted to the right type...
unsigned TypeBits = C->getType()->getPrimitiveSizeInBits();
uint64_t Val = ~0ULL; // All ones
Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
return CU->getValue() == Val-1;
}
const ConstantSInt *CS = cast<ConstantSInt>(C);
// Calculate 0111111111..11111
unsigned TypeBits = C->getType()->getPrimitiveSizeInBits();
int64_t Val = INT64_MAX; // All ones
Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
return CS->getValue() == Val-1;
}
// isMinValuePlusOne - return true if this is Min+1
static bool isMinValuePlusOne(const ConstantInt *C) {
if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C))
return CU->getValue() == 1;
const ConstantSInt *CS = cast<ConstantSInt>(C);
// Calculate 1111111111000000000000
unsigned TypeBits = C->getType()->getPrimitiveSizeInBits();
int64_t Val = -1; // All ones
Val <<= TypeBits-1; // Shift over to the right spot
return CS->getValue() == 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->getRawValue();
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->getRawValue();
// There won't be bits set in parts that the type doesn't contain.
V &= ConstantInt::getAllOnesValue(CI->getType())->getRawValue();
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->getRawValue();
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())->getRawValue();
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::False;
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::True;
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)->getRawValue();
// Clear bits that are not part of the constant.
AndRHSV &= ~0ULL >> (64-AndRHS->getType()->getPrimitiveSizeInBits());
// 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)->getRawValue();
// 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::Shr:
// 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!
//
if (AndRHS->getType()->isUnsigned()) {
Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
Constant *ShrMask = ConstantExpr::getShr(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;
}
} else { // 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::getUShr(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 = InsertCastBefore(ShVal,
ShVal->getType()->getUnsignedVersion(),
TheAnd);
ShVal = InsertNewInstBefore(new ShiftInst(Instruction::Shr, ShVal,
OpRHS, Op->getName()),
TheAnd);
Value *AndRHS2 = ConstantExpr::getCast(AndRHS, ShVal->getType());
ShVal = InsertNewInstBefore(BinaryOperator::createAnd(ShVal, AndRHS2,
TheAnd.getName()),
TheAnd);
return new CastInst(ShVal, Op->getType());
}
}
}
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));
if (cast<ConstantIntegral>(Lo)->isMinValue()) // V < 0 || V >= Hi ->'V > Hi-1'
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->getRawValue();
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->getRawValue() & Mask->getRawValue()+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
Constant *Mask = ConstantInt::getAllOnesValue(RHS->getType());
Mask = ConstantExpr::getUShr(Mask,
ConstantInt::get(Type::UByteTy,
(64-MB+1)));
if (MaskedValueIsZero(RHS, cast<ConstantIntegral>(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->getRawValue() & Mask->getRawValue()+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);
if (ConstantIntegral *AndRHS = dyn_cast<ConstantIntegral>(Op1)) {
// and X, -1 == X
if (AndRHS->isAllOnesValue())
return ReplaceInstUsesWith(I, Op0);
// and (and X, c1), c2 -> and (x, c1&c2). Handle this case here, before
// calling MaskedValueIsZero, to avoid inefficient cases where we traipse
// through many levels of ands.
{
Value *X; ConstantInt *C1;
if (match(Op0, m_And(m_Value(X), m_ConstantInt(C1))))
return BinaryOperator::createAnd(X, ConstantExpr::getAnd(C1, AndRHS));
}
if (MaskedValueIsZero(Op0, AndRHS)) // LHS & RHS == 0
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
// If the mask is not masking out any bits, there is no reason to do the
// and in the first place.
ConstantIntegral *NotAndRHS =
cast<ConstantIntegral>(ConstantExpr::getNot(AndRHS));
if (MaskedValueIsZero(Op0, NotAndRHS))
return ReplaceInstUsesWith(I, Op0);
// 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:
// (X ^ V) & C2 --> (X & C2) iff (V & C2) == 0
// (X | V) & C2 --> (X & C2) iff (V & C2) == 0
if (MaskedValueIsZero(Op0LHS, AndRHS))
return BinaryOperator::createAnd(Op0RHS, AndRHS);
if (MaskedValueIsZero(Op0RHS, AndRHS))
return BinaryOperator::createAnd(Op0LHS, AndRHS);
// 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>(NotAndRHS) &&
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::And:
// (X & V) & C2 --> 0 iff (V & C2) == 0
if (MaskedValueIsZero(Op0LHS, AndRHS) ||
MaskedValueIsZero(Op0RHS, AndRHS))
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
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);
}
}
// If this is an integer sign or zero extension instruction.
if (SrcTy->isIntegral() &&
SrcTy->getPrimitiveSizeInBits() <
CI->getType()->getPrimitiveSizeInBits()) {
if (SrcTy->isUnsigned()) {
// See if this and is clearing out bits that are known to be zero
// anyway (due to the zero extension).
Constant *Mask = ConstantIntegral::getAllOnesValue(SrcTy);
Mask = ConstantExpr::getZeroExtend(Mask, CI->getType());
Constant *Result = ConstantExpr::getAnd(Mask, AndRHS);
if (Result == Mask) // The "and" isn't doing anything, remove it.
return ReplaceInstUsesWith(I, CI);
if (Result != AndRHS) { // Reduce the and RHS constant.
I.setOperand(1, Result);
return &I;
}
} else {
if (CI->hasOneUse() && SrcTy->isInteger()) {
// We can only do this if all of the sign bits brought in are masked
// out. Compute this by first getting 0000011111, then inverting
// it.
Constant *Mask = ConstantIntegral::getAllOnesValue(SrcTy);
Mask = ConstantExpr::getZeroExtend(Mask, CI->getType());
Mask = ConstantExpr::getNot(Mask); // 1's in the new bits.
if (ConstantExpr::getAnd(Mask, AndRHS)->isNullValue()) {
// If the and is clearing all of the sign bits, change this to a
// zero extension cast. To do this, cast the cast input to
// unsigned, then to the requested size.
Value *CastOp = CI->getOperand(0);
Instruction *NC =
new CastInst(CastOp, CastOp->getType()->getUnsignedVersion(),
CI->getName()+".uns");
NC = InsertNewInstBefore(NC, I);
// Finally, insert a replacement for CI.
NC = new CastInst(NC, CI->getType(), CI->getName());
CI->setName("");
NC = InsertNewInstBefore(NC, I);
WorkList.push_back(CI); // Delete CI later.
I.setOperand(0, NC);
return &I; // The AND operand was modified.
}
}
}
}
}
// 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);
}
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::False);
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::False);
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);
}
}
}
}
return Changed ? &I : 0;
}
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 or X, 0 == X
if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
return ReplaceInstUsesWith(I, Op0);
// or X, -1 == -1
if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
// If X is known to only contain bits that already exist in RHS, just
// replace this instruction with RHS directly.
if (MaskedValueIsZero(Op0,
cast<ConstantIntegral>(ConstantExpr::getNot(RHS))))
return ReplaceInstUsesWith(I, RHS);
ConstantInt *C1; Value *X;
// (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, *B; ConstantInt *C1, *C2;
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);
// (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)) {
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)) {
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, *V2;
if ((C2->getRawValue() & (C2->getRawValue()+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))
return ReplaceInstUsesWith(I, A);
if (V2 == B && MaskedValueIsZero(V1, C2))
return ReplaceInstUsesWith(I, A);
}
// Or commutes, try both ways.
if ((C1->getRawValue() & (C1->getRawValue()+1)) == 0 &&
match(B, m_Add(m_Value(V1), m_Value(V2)))) {
// Add commutes, try both ways.
if (V1 == A && MaskedValueIsZero(V2, C1))
return ReplaceInstUsesWith(I, B);
if (V2 == A && MaskedValueIsZero(V1, C1))
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::True);
}
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::True);
}
}
}
}
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()));
}
if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
// xor X, 0 == X
if (RHS->isNullValue())
return ReplaceInstUsesWith(I, Op0);
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::True && 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)))
switch (Op0I->getOpcode()) {
case 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));
}
break;
case Instruction::And:
// (X & C1) ^ C2 --> (X & C1) | C2 iff (C1&C2) == 0
if (ConstantExpr::getAnd(RHS, Op0CI)->isNullValue())
return BinaryOperator::createOr(Op0, RHS);
break;
case Instruction::Or:
// (X | C1) ^ C2 --> (X | C1) & ~C2 iff (C1&C2) == C2
if (ConstantExpr::getAnd(RHS, Op0CI) == RHS)
return BinaryOperator::createAnd(Op0, ConstantExpr::getNot(RHS));
break;
default: break;
}
}
// 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 (Instruction *Op1I = dyn_cast<Instruction>(Op1))
if (Op1I->getOpcode() == Instruction::Or) {
if (Op1I->getOperand(0) == Op0) { // B^(B|A) == (A|B)^B
cast<BinaryOperator>(Op1I)->swapOperands();
I.swapOperands();
std::swap(Op0, Op1);
} else if (Op1I->getOperand(1) == Op0) { // B^(A|B) == (A|B)^B
I.swapOperands();
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));
}
if (Instruction *Op0I = dyn_cast<Instruction>(Op0))
if (Op0I->getOpcode() == Instruction::Or && Op0I->hasOneUse()) {
if (Op0I->getOperand(0) == Op1) // (B|A)^B == (A|B)^B
cast<BinaryOperator>(Op0I)->swapOperands();
if (Op0I->getOperand(1) == Op1) { // (A|B)^B == A & ~B
Value *NotB = InsertNewInstBefore(BinaryOperator::createNot(Op1,
Op1->getName()+".not"), 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));
}
// (A & C1)^(B & C2) -> (A & C1)|(B & C2) iff C1&C2 == 0
Value *A, *B; ConstantInt *C1, *C2;
if (match(Op0, m_And(m_Value(A), m_ConstantInt(C1))) &&
match(Op1, m_And(m_Value(B), m_ConstantInt(C2))) &&
ConstantExpr::getAnd(C1, C2)->isNullValue())
return BinaryOperator::createOr(Op0, 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;
return Changed ? &I : 0;
}
/// MulWithOverflow - Compute Result = In1*In2, returning true if the result
/// overflowed for this type.
static bool MulWithOverflow(ConstantInt *&Result, ConstantInt *In1,
ConstantInt *In2) {
Result = cast<ConstantInt>(ConstantExpr::getMul(In1, In2));
return !In2->isNullValue() && ConstantExpr::getDiv(Result, In2) != In1;
}
static bool isPositive(ConstantInt *C) {
return cast<ConstantSInt>(C)->getValue() >= 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<ConstantUInt>(Result)->getValue() <
cast<ConstantUInt>(In1)->getValue();
if (isPositive(In1) != isPositive(In2))
return false;
if (isPositive(In1))
return cast<ConstantSInt>(Result)->getValue() <
cast<ConstantSInt>(In1)->getValue();
return cast<ConstantSInt>(Result)->getValue() >
cast<ConstantSInt>(In1)->getValue();
}
/// 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;
PtrSizeMask >>= 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(ConstantUInt::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 = InsertNewInstBefore(new CastInst(LHSV, NewTy,
LHSV->getName()), I);
if (RHSV->getType() != NewTy)
RHSV = InsertNewInstBefore(new CastInst(RHSV, NewTy,
RHSV->getName()), 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::False);
if (I.getOpcode() == Instruction::SetGE) // A >= MIN -> TRUE
return ReplaceInstUsesWith(I, ConstantBool::True);
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::False);
if (I.getOpcode() == Instruction::SetLE) // A <= MAX -> TRUE
return ReplaceInstUsesWith(I, ConstantBool::True);
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));
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()) {
// 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));
ConstantUInt *ShAmt;
ShAmt = Shift ? dyn_cast<ConstantUInt>(Shift->getOperand(1)) : 0;
ConstantInt *AndCST = cast<ConstantInt>(LHSI->getOperand(1));
const Type *Ty = LHSI->getType();
// 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->getOpcode() != Instruction::Shr ||
Shift->getType()->isUnsigned();
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->getValue();
if (ShAmtVal < 0) ShAmtVal = 0; // Out of range shift.
Constant *OShAmt = ConstantUInt::get(Type::UByteTy, ShAmtVal);
Constant *ShVal =
ConstantExpr::getShl(ConstantInt::getAllOnesValue(Ty), OShAmt);
if (ConstantExpr::getAnd(ShVal, AndCST)->isNullValue())
CanFold = true;
}
if (CanFold) {
Constant *NewCst;
if (Shift->getOpcode() == Instruction::Shl)
NewCst = ConstantExpr::getUShr(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::False);
if (I.getOpcode() == Instruction::SetNE)
return ReplaceInstUsesWith(I, ConstantBool::True);
} else {
I.setOperand(1, NewCst);
Constant *NewAndCST;
if (Shift->getOpcode() == Instruction::Shl)
NewAndCST = ConstantExpr::getUShr(AndCST, ShAmt);
else
NewAndCST = ConstantExpr::getShl(AndCST, ShAmt);
LHSI->setOperand(1, NewAndCST);
LHSI->setOperand(0, Shift->getOperand(0));
WorkList.push_back(Shift); // Shift is dead.
AddUsesToWorkList(I);
return &I;
}
}
}
}
break;
case Instruction::Shl: // (setcc (shl X, ShAmt), CI)
if (ConstantUInt *ShAmt = dyn_cast<ConstantUInt>(LHSI->getOperand(1))) {
switch (I.getOpcode()) {
default: break;
case Instruction::SetEQ:
case Instruction::SetNE: {
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->getValue() >= TypeBits)
break;
// If we are comparing against bits always shifted out, the
// comparison cannot succeed.
Constant *Comp =
ConstantExpr::getShl(ConstantExpr::getShr(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->getValue();
uint64_t Val = (1ULL << (TypeBits-ShAmtVal))-1;
Constant *Mask;
if (CI->getType()->isUnsigned()) {
Mask = ConstantUInt::get(CI->getType(), Val);
} else if (ShAmtVal != 0) {
Mask = ConstantSInt::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::getUShr(CI, ShAmt));
}
}
}
}
break;
case Instruction::Shr: // (setcc (shr X, ShAmt), CI)
if (ConstantUInt *ShAmt = dyn_cast<ConstantUInt>(LHSI->getOperand(1))) {
switch (I.getOpcode()) {
default: break;
case Instruction::SetEQ:
case Instruction::SetNE: {
// 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->getValue() >= TypeBits)
break;
// If we are comparing against bits always shifted out, the
// comparison cannot succeed.
Constant *Comp =
ConstantExpr::getShr(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->getValue();
// 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 = ConstantUInt::get(CI->getType(), Val);
} else {
Mask = ConstantSInt::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;
}
}
}
break;
case Instruction::Div:
// Fold: (div X, C1) op C2 -> range check
if (ConstantInt *DivRHS = dyn_cast<ConstantInt>(LHSI->getOperand(1))) {
// 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.
bool LoOverflow = false, HiOverflow = 0;
ConstantInt *LoBound = 0, *HiBound = 0;
ConstantInt *Prod;
bool ProdOV = MulWithOverflow(Prod, CI, DivRHS);
Instruction::BinaryOps Opcode = I.getOpcode();
if (DivRHS->isNullValue()) { // Don't hack on divide by zeros.
} else if (LHSI->getType()->isUnsigned()) { // 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::False);
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::True);
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::False);
return new SetCondInst(Instruction::SetLT, X, LoBound);
case Instruction::SetGT:
if (HiOverflow)
return ReplaceInstUsesWith(I, ConstantBool::False);
return new SetCondInst(Instruction::SetGE, X, HiBound);
}
}
}
break;
}
// Simplify seteq and setne instructions...
if (I.getOpcode() == Instruction::SetEQ ||
I.getOpcode() == Instruction::SetNE) {
bool isSetNE = I.getOpcode() == Instruction::SetNE;
// If the first operand is (and|or|xor) 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::Rem:
// If we have a signed (X % (2^c)) == 0, turn it into an unsigned one.
if (CI->isNullValue() && isa<ConstantSInt>(BO->getOperand(1)) &&
BO->hasOneUse() &&
cast<ConstantSInt>(BO->getOperand(1))->getValue() > 1) {
int64_t V = cast<ConstantSInt>(BO->getOperand(1))->getValue();
if (isPowerOf2_64(V)) {
unsigned L2 = Log2_64(V);
const Type *UTy = BO->getType()->getUnsignedVersion();
Value *NewX = InsertNewInstBefore(new CastInst(BO->getOperand(0),
UTy, "tmp"), I);
Constant *RHSCst = ConstantUInt::get(UTy, 1ULL << L2);
Value *NewRem =InsertNewInstBefore(BinaryOperator::createRem(NewX,
RHSCst, BO->getName()), I);
return BinaryOperator::create(I.getOpcode(), NewRem,
Constant::getNullValue(UTy));
}
}
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,
ConstantUInt::get(SrcTy, (1ULL << (SrcTySize-1))-1));
else if (I.getOpcode() == Instruction::SetGT &&
cast<ConstantSInt>(CI)->getValue() == -1)
// X > -1 => x < 128
return BinaryOperator::createSetLT(CastOp,
ConstantUInt::get(SrcTy, 1ULL << (SrcTySize-1)));
} else {
ConstantUInt *CUI = cast<ConstantUInt>(CI);
if (I.getOpcode() == Instruction::SetLT &&
CUI->getValue() == 1ULL << (SrcTySize-1))
// X < 128 => X > -1
return BinaryOperator::createSetGT(CastOp,
ConstantSInt::get(SrcTy, -1));
else if (I.getOpcode() == Instruction::SetGT &&
CUI->getValue() == (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.getOpcode() == Instruction::SetEQ ||
I.getOpcode() == Instruction::SetNE)) {
// 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 = new CastInst(Op1, Op0->getType(), Op1->getName());
InsertNewInstBefore(cast<Instruction>(Op1), 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;
}
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) {
RHSCIOp = Res;
} 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::False);
if (SCI.getOpcode() == Instruction::SetNE)
return ReplaceInstUsesWith(SCI, ConstantBool::True);
// 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<ConstantSInt>(CI)->getValue() < 0) // X < (small) --> false
Result = ConstantBool::False;
else
Result = ConstantBool::True; // X < (large) --> true
} else {
// Unsigned extend and signed comparison.
if (cast<ConstantSInt>(CI)->getValue() < 0)
Result = ConstantBool::False;
else
Result = ConstantBool::True;
}
} else {
// We're performing an unsigned comparison.
if (!isSignSrc) {
// Unsigned extend & compare -> always true.
Result = ConstantBool::True;
} 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 (ConstantSInt *CSI = dyn_cast<ConstantSInt>(Op0))
if (CSI->isAllOnesValue())
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 (!isLeftShift && I.getType()->isSigned()) {
if (MaskedValueIsZero(Op0, ConstantInt::getMinValue(I.getType()))) {
Value *V = InsertCastBefore(Op0, I.getType()->getUnsignedVersion(), I);
V = InsertNewInstBefore(new ShiftInst(Instruction::Shr, V, Op1,
I.getName()), I);
return new CastInst(V, I.getType());
}
}
if (ConstantUInt *CUI = dyn_cast<ConstantUInt>(Op1)) {
// 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 (CUI->getValue() >= TypeBits) {
if (!Op0->getType()->isSigned() || isLeftShift)
return ReplaceInstUsesWith(I, Constant::getNullValue(Op0->getType()));
else {
I.setOperand(1, ConstantUInt::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, CUI));
// 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 this is a SHL of a sign-extending cast, see if we can turn the input
// into a zero extending cast (a simple strength reduction).
if (CastInst *CI = dyn_cast<CastInst>(Op0)) {
const Type *SrcTy = CI->getOperand(0)->getType();
if (isLeftShift && SrcTy->isInteger() && SrcTy->isSigned() &&
SrcTy->getPrimitiveSizeInBits() <
CI->getType()->getPrimitiveSizeInBits()) {
// We can change it to a zero extension if we are shifting out all of
// the sign extended bits. To check this, form a mask of all of the
// sign extend bits, then shift them left and see if we have anything
// left.
Constant *Mask = ConstantIntegral::getAllOnesValue(SrcTy); // 1111
Mask = ConstantExpr::getZeroExtend(Mask, CI->getType()); // 00001111
Mask = ConstantExpr::getNot(Mask); // 1's in the sign bits: 11110000
if (ConstantExpr::getShl(Mask, CUI)->isNullValue()) {
// If the shift is nuking all of the sign bits, change this to a
// zero extension cast. To do this, cast the cast input to
// unsigned, then to the requested size.
Value *CastOp = CI->getOperand(0);
Instruction *NC =
new CastInst(CastOp, CastOp->getType()->getUnsignedVersion(),
CI->getName()+".uns");
NC = InsertNewInstBefore(NC, I);
// Finally, insert a replacement for CI.
NC = new CastInst(NC, CI->getType(), CI->getName());
CI->setName("");
NC = InsertNewInstBefore(NC, I);
WorkList.push_back(CI); // Delete CI later.
I.setOperand(0, NC);
return &I; // The SHL operand was modified.
}
}
}
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 == CUI) {
Instruction *YS = new ShiftInst(Instruction::Shl,
Op0BO->getOperand(0), CUI,
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, CUI);
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 == CUI &&
cast<BinaryOperator>(Op0BO->getOperand(1))->getOperand(0)->hasOneUse()) {
Instruction *YS = new ShiftInst(Instruction::Shl,
Op0BO->getOperand(0), CUI,
Op0BO->getName());
InsertNewInstBefore(YS, I); // (Y << C)
Instruction *XM =
BinaryOperator::createAnd(V1, ConstantExpr::getShl(CC, CUI),
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 == CUI) {
Instruction *YS = new ShiftInst(Instruction::Shl,
Op0BO->getOperand(1), CUI,
Op0BO->getName());
InsertNewInstBefore(YS, I); // (Y << C)
Instruction *X = BinaryOperator::create(Op0BO->getOpcode(), YS,
V1,
Op0BO->getOperand(0)->getName());
InsertNewInstBefore(X, I); // (X + (Y << C))
Constant *C2 = ConstantInt::getAllOnesValue(X->getType());
C2 = ConstantExpr::getShl(C2, CUI);
return BinaryOperator::createAnd(X, C2);
}
if (isLeftShift && Op0BO->getOperand(0)->hasOneUse() &&
match(Op0BO->getOperand(0),
m_And(m_Shr(m_Value(V1), m_Value(V2)),
m_ConstantInt(CC))) && V2 == CUI &&
cast<BinaryOperator>(Op0BO->getOperand(0))->getOperand(0)->hasOneUse()) {
Instruction *YS = new ShiftInst(Instruction::Shl,
Op0BO->getOperand(1), CUI,
Op0BO->getName());
InsertNewInstBefore(YS, I); // (Y << C)
Instruction *XM =
BinaryOperator::createAnd(V1, ConstantExpr::getShl(CC, CUI),
V1->getName()+".mask");
InsertNewInstBefore(XM, I); // X & (CC << C)
return BinaryOperator::create(Op0BO->getOpcode(), YS, XM);
}
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 && !I.getType()->isUnsigned()) {
uint64_t Val = Op0C->getRawValue();
isValid = ((Val & (1 << (TypeBits-1))) != 0) == highBitSet;
}
if (isValid) {
Constant *NewRHS = ConstantExpr::get(I.getOpcode(), Op0C, CUI);
Instruction *NewShift =
new ShiftInst(I.getOpcode(), Op0BO->getOperand(0), CUI,
Op0BO->getName());
Op0BO->setName("");
InsertNewInstBefore(NewShift, I);
return BinaryOperator::create(Op0BO->getOpcode(), NewShift,
NewRHS);
}
}
}
}
// If this is a shift of a shift, see if we can fold the two together...
if (ShiftInst *Op0SI = dyn_cast<ShiftInst>(Op0))
if (ConstantUInt *ShiftAmt1C =
dyn_cast<ConstantUInt>(Op0SI->getOperand(1))) {
unsigned ShiftAmt1 = (unsigned)ShiftAmt1C->getValue();
unsigned ShiftAmt2 = (unsigned)CUI->getValue();
// Check for (A << c1) << c2 and (A >> c1) >> c2
if (I.getOpcode() == Op0SI->getOpcode()) {
unsigned Amt = ShiftAmt1+ShiftAmt2; // Fold into one big shift...
if (Op0->getType()->getPrimitiveSizeInBits() < Amt)
Amt = Op0->getType()->getPrimitiveSizeInBits();
return new ShiftInst(I.getOpcode(), Op0SI->getOperand(0),
ConstantUInt::get(Type::UByteTy, Amt));
}
// Check for (A << c1) >> c2 or visaversa. 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 (I.getType()->isUnsigned() || 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::getShr(C, ShiftAmt1C);
Instruction *Mask =
BinaryOperator::createAnd(Op0SI->getOperand(0), C,
Op0SI->getOperand(0)->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,
ConstantUInt::get(Type::UByteTy, ShiftAmt2-ShiftAmt1));
} else {
return new ShiftInst(Op0SI->getOpcode(), Mask,
ConstantUInt::get(Type::UByteTy, ShiftAmt1-ShiftAmt2));
}
} else {
// We can handle signed (X << C1) >> 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 (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(Op0SI->getOperand(0),
SExtType, "sext");
InsertNewInstBefore(NewTrunc, I);
return new CastInst(NewTrunc, I.getType());
}
}
}
}
}
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 inline 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;
}
}
return false;
}
static bool ValueRequiresCast(const Value *V, const Type *Ty, TargetData *TD) {
if (V->getType() == Ty || isa<Constant>(V)) return false;
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);
CastInst *CI = new CastInst(V, DestTy, V->getName());
InsertNewInstBefore(CI, *InsertBefore);
return CI;
}
/// 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 (ConstantUInt *CI = dyn_cast<ConstantUInt>(Val)) {
Offset = CI->getValue();
Scale = 1;
return ConstantUInt::get(Type::UIntTy, 0);
} else if (Instruction *I = dyn_cast<Instruction>(Val)) {
if (I->getNumOperands() == 2) {
if (ConstantUInt *CUI = dyn_cast<ConstantUInt>(I->getOperand(1))) {
if (I->getOpcode() == Instruction::Shl) {
// This is a value scaled by '1 << the shift amt'.
Scale = 1U << CUI->getValue();
Offset = 0;
return I->getOperand(0);
} else if (I->getOpcode() == Instruction::Mul) {
// This value is scaled by 'CUI'.
Scale = CUI->getValue();
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->getValue();
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->getTypeSize(AllocElTy);
unsigned CastElTyAlign = TD->getTypeSize(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 {
Amt = ConstantUInt::get(Type::UIntTy, Scale);
if (ConstantUInt *CI = dyn_cast<ConstantUInt>(NumElements))
Amt = ConstantExpr::getMul(CI, cast<ConstantUInt>(Amt));
else if (Scale != 1) {
Instruction *Tmp = BinaryOperator::createMul(Amt, NumElements, "tmp");
Amt = InsertNewInstBefore(Tmp, AI);
}
}
if (unsigned Offset = (AllocElTySize*ArrayOffset)/CastElTySize) {
Value *Off = ConstantUInt::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);
}
// 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 = ~0ULL>>(64-CSrc->getType()->getPrimitiveSizeInBits());
Constant *AndOp = ConstantUInt::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()));
// 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 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
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::True &&
(!Op0->hasOneUse() || !isa<SetCondInst>(Op0))) {
Value *New = InsertOperandCastBefore(Op0, DestTy, &CI);
return BinaryOperator::createXor(New,
ConstantInt::get(CI.getType(), 1));
}
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
// mush 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::Shr:
// 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 && Src->getType()->isSigned() &&
isa<ConstantInt>(Op1)) {
unsigned ShiftAmt = cast<ConstantUInt>(Op1)->getValue();
if (SrcBitSize > ShiftAmt && SrcBitSize-ShiftAmt >= DestBitSize) {
// Convert to unsigned.
Value *N1 = InsertOperandCastBefore(Op0,
Op0->getType()->getUnsignedVersion(), &CI);
// Insert the new shift, which is now unsigned.
N1 = InsertNewInstBefore(new ShiftInst(Instruction::Shr, N1,
Op1, Src->getName()), CI);
return new CastInst(N1, CI.getType());
}
}
break;
case Instruction::SetNE:
if (ConstantInt *Op1C = dyn_cast<ConstantInt>(Op1)) {
if (Op1C->getRawValue() == 0) {
// If the input only has the low bit set, simplify directly.
Constant *Not1 =
ConstantExpr::getNot(ConstantInt::get(Op0->getType(), 1));
// cast (X != 0) to int --> X if X&~1 == 0
if (MaskedValueIsZero(Op0, cast<ConstantIntegral>(Not1))) {
if (CI.getType() == Op0->getType())
return ReplaceInstUsesWith(CI, Op0);
else
return new CastInst(Op0, CI.getType());
}
// If the input is an and with a single bit, shift then simplify.
ConstantInt *AndRHS;
if (match(Op0, m_And(m_Value(), m_ConstantInt(AndRHS))))
if (AndRHS->getRawValue() &&
(AndRHS->getRawValue() & (AndRHS->getRawValue()-1)) == 0) {
unsigned ShiftAmt = Log2_64(AndRHS->getRawValue());
// Perform an unsigned shr by shiftamt. Convert input to
// unsigned if it is signed.
Value *In = Op0;
if (In->getType()->isSigned())
In = InsertNewInstBefore(new CastInst(In,
In->getType()->getUnsignedVersion(), In->getName()),CI);
// Insert the shift to put the result in the low bit.
In = InsertNewInstBefore(new ShiftInst(Instruction::Shr, In,
ConstantInt::get(Type::UByteTy, ShiftAmt),
In->getName()+".lobit"), CI);
if (CI.getType() == In->getType())
return ReplaceInstUsesWith(CI, In);
else
return new CastInst(In, CI.getType());
}
}
}
break;
case Instruction::SetEQ:
// 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)) {
// Is Op1C a power of two or zero?
if ((Op1C->getRawValue() & Op1C->getRawValue()-1) == 0) {
// cast (X == 1) to int -> X iff X has only the low bit set.
if (Op1C->getRawValue() == 1) {
Constant *Not1 =
ConstantExpr::getNot(ConstantInt::get(Op0->getType(), 1));
if (MaskedValueIsZero(Op0, cast<ConstantIntegral>(Not1))) {
if (CI.getType() == Op0->getType())
return ReplaceInstUsesWith(CI, Op0);
else
return new CastInst(Op0, CI.getType());
}
}
}
}
break;
}
}
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::Shr:
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::Shr:
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))
if (C == ConstantBool::True)
return ReplaceInstUsesWith(SI, TrueVal);
else {
assert(C == ConstantBool::False);
return ReplaceInstUsesWith(SI, 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 == ConstantBool::True) {
// 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 == ConstantBool::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->getRawValue() == 1) {
return new CastInst(CondVal, SI.getType());
} else if (TrueValC->isNullValue() && FalseValC->getRawValue() == 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 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 (Instruction *IC = dyn_cast<Instruction>(SI.getCondition()))
if ((IC->getOpcode() == Instruction::SetEQ ||
IC->getOpcode() == Instruction::SetNE) &&
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()) {
bool isInverse = false;
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:
// select C, (add X, Y), (sub X, ?)
// We can do the transform profitably if either 'Y' = '?' or '?' is
// a constant.
if (SubOp->getOperand(1) == AddOp ||
isa<Constant>(SubOp->getOperand(1))) {
Value *NegVal;
if (Constant *C = dyn_cast<Constant>(SubOp->getOperand(1))) {
NegVal = ConstantExpr::getNeg(C);
} else {
NegVal = InsertNewInstBefore(
BinaryOperator::createNeg(SubOp->getOperand(1)), 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;
}
// CallInst simplification
//
Instruction *InstCombiner::visitCallInst(CallInst &CI) {
// Intrinsics cannot occur in an invoke, so handle them here instead of in
// visitCallSite.
if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(&CI)) {
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);
// FIXME: Increase alignment here.
if (ConstantInt *CI = dyn_cast<ConstantInt>(NumBytes))
if (CI->getRawValue() == 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>(MI))
if (GlobalVariable *GVSrc = dyn_cast<GlobalVariable>(MMI->getSource()))
if (GVSrc->isConstant()) {
Module *M = CI.getParent()->getParent()->getParent();
Function *MemCpy = M->getOrInsertFunction("llvm.memcpy",
CI.getCalledFunction()->getFunctionType());
CI.setOperand(0, MemCpy);
Changed = true;
}
if (Changed) return &CI;
} else if (DbgStopPointInst *SPI = dyn_cast<DbgStopPointInst>(&CI)) {
// If this stoppoint is at the same source location as the previous
// stoppoint in the chain, it is not needed.
if (DbgStopPointInst *PrevSPI =
dyn_cast<DbgStopPointInst>(SPI->getChain()))
if (SPI->getLineNo() == PrevSPI->getLineNo() &&
SPI->getColNo() == PrevSPI->getColNo()) {
SPI->replaceAllUsesWith(PrevSPI);
return EraseInstFromFunction(CI);
}
}
return visitCallSite(&CI);
}
// 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::True,
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::True,
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::True, 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()) &&
!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);
bool isConvertible = (*AI)->getType()->isLosslesslyConvertibleTo(ParamTy);
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;
}
// 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;
if (isa<CastInst>(FirstInst)) {
CastSrcTy = FirstInst->getOperand(0)->getType();
} else if (isa<BinaryOperator>(FirstInst) || isa<ShiftInst>(FirstInst)) {
// Can fold binop or shift if the RHS is a constant.
ConstantOp = dyn_cast<Constant>(FirstInst->getOperand(1));
if (ConstantOp == 0) 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 (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 (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 (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->InsertNewInstBefore(new CastInst(V, VTy->getSignedVersion(),
V->getName()), *InsertPoint);
return IC->InsertNewInstBefore(new CastInst(V, DTy, V->getName()),
*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 = InsertNewInstBefore(new CastInst(Op, TD->getIntPtrType(),
Op->getName()), 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 (ConstantUInt *CUI = dyn_cast<ConstantUInt>(Op)) {
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<ConstantUInt>(Inst->getOperand(1))->getValue();
if (Inst->getType()->isSigned())
Scale = ConstantSInt::get(Inst->getType(), 1ULL << ShAmt);
else
Scale = ConstantUInt::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->getRawValue() % ArrayEltSize == 0) {
if (ConstantSInt *C = dyn_cast<ConstantSInt>(Scale))
Scale = ConstantSInt::get(C->getType(),
(int64_t)C->getRawValue() /
(int64_t)ArrayEltSize);
else
Scale = ConstantUInt::get(Scale->getType(),
Scale->getRawValue() / ArrayEltSize);
if (Scale->getRawValue() != 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 ConstantUInt *C = dyn_cast<ConstantUInt>(AI.getArraySize())) {
const Type *NewTy = ArrayType::get(AI.getAllocatedType(), C->getValue());
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::True,
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)) {
// 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)) &&
// 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 (CastInst *CI = dyn_cast<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;
}
} else if (PHINode *PN = dyn_cast<PHINode>(Op)) {
// load (phi (&V1, &V2, &V3)) --> phi(load &V1, load &V2, load &V3)
bool Safe = PN->getParent() == LI.getParent();
// Scan all of the instructions between the PHI and the load to make
// sure there are no instructions that might possibly alter the value
// loaded from the PHI.
if (Safe) {
BasicBlock::iterator I = &LI;
for (--I; !isa<PHINode>(I); --I)
if (isa<StoreInst>(I) || isa<CallInst>(I)) {
Safe = false;
break;
}
}
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e && Safe; ++i)
if (!isSafeToLoadUnconditionally(PN->getIncomingValue(i),
PN->getIncomingBlock(i)->getTerminator()))
Safe = false;
if (Safe) {
// Create the PHI.
PHINode *NewPN = new PHINode(LI.getType(), PN->getName());
InsertNewInstBefore(NewPN, *PN);
std::map<BasicBlock*,Value*> LoadMap; // Don't insert duplicate loads
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
BasicBlock *BB = PN->getIncomingBlock(i);
Value *&TheLoad = LoadMap[BB];
if (TheLoad == 0) {
Value *InVal = PN->getIncomingValue(i);
TheLoad = InsertNewInstBefore(new LoadInst(InVal,
InVal->getName()+".val"),
*BB->getTerminator());
}
NewPN->addIncoming(TheLoad, BB);
}
return ReplaceInstUsesWith(LI, NewPN);
}
}
}
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)
removeFromWorkList(&SI);
SI.eraseFromParent();
++NumCombined;
return 0;
}
if (SI.isVolatile()) return 0; // Don't hack volatile loads.
// 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)) {
removeFromWorkList(&SI);
SI.eraseFromParent();
++NumCombined;
return 0;
}
// If the pointer destination is a cast, see if we can fold the cast into the
// source instead.
if (CastInst *CI = dyn_cast<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.
BasicBlock::iterator 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.
removeFromWorkList(&SI);
removeFromWorkList(OtherStore);
SI.eraseFromParent();
OtherStore->eraseFromParent();
++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;
}
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;
}
bool InstCombiner::runOnFunction(Function &F) {
bool Changed = false;
TD = &getAnalysis<TargetData>();
{
// Populate the worklist with the reachable instructions.
std::set<BasicBlock*> Visited;
for (df_ext_iterator<BasicBlock*> BB = df_ext_begin(&F.front(), Visited),
E = df_ext_end(&F.front(), Visited); BB != E; ++BB)
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
WorkList.push_back(I);
// 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 or ConstantPropagate the instruction...
// Check to see if we can DIE 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)) {
Value* Ptr = I->getOperand(0);
if (isa<GetElementPtrInst>(I) &&
cast<Constant>(Ptr)->isNullValue() &&
!isa<ConstantPointerNull>(C) &&
cast<PointerType>(Ptr->getType())->getElementType()->isSized()) {
// If this is a constant expr gep that is effectively computing an
// "offsetof", fold it into 'cast int X to T*' instead of 'gep 0, 0, 12'
bool isFoldableGEP = true;
for (unsigned i = 1, e = I->getNumOperands(); i != e; ++i)
if (!isa<ConstantInt>(I->getOperand(i)))
isFoldableGEP = false;
if (isFoldableGEP) {
uint64_t Offset = TD->getIndexedOffset(Ptr->getType(),
std::vector<Value*>(I->op_begin()+1, I->op_end()));
C = ConstantUInt::get(Type::ULongTy, Offset);
C = ConstantExpr::getCast(C, TD->getIntPtrType());
C = ConstantExpr::getCast(C, I->getType());
}
}
DEBUG(std::cerr << "IC: ConstFold to: " << *C << " from: " << *I);
// Add operands to the worklist...
AddUsesToWorkList(*I);
ReplaceInstUsesWith(*I, C);
++NumConstProp;
I->getParent()->getInstList().erase(I);
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
// occurrances 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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