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llvm-6502/lib/Transforms/Scalar/InstructionCombining.cpp
Chris Lattner c5943fb186 Implement cast.ll::test14/15 
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@11742 91177308-0d34-0410-b5e6-96231b3b80d8
2004-02-23 07:16:20 +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 1, %X
// %Z = add int 1, %Y
// into:
// %Z = add int 2, %X
//
// 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.
// N. This list is incomplete
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Scalar.h"
#include "llvm/Instructions.h"
#include "llvm/Pass.h"
#include "llvm/Constants.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/InstIterator.h"
#include "llvm/Support/InstVisitor.h"
#include "llvm/Support/CallSite.h"
#include "Support/Statistic.h"
#include <algorithm>
using namespace llvm;
namespace {
Statistic<> NumCombined ("instcombine", "Number of insts combined");
Statistic<> NumConstProp("instcombine", "Number of constant folds");
Statistic<> NumDeadInst ("instcombine", "Number of dead inst eliminated");
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;
void AddUsesToWorkList(Instruction &I) {
// The instruction was simplified, add all users of the instruction to
// the work lists because they might get more simplified now...
//
for (Value::use_iterator UI = I.use_begin(), UE = I.use_end();
UI != UE; ++UI)
WorkList.push_back(cast<Instruction>(*UI));
}
// 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();
}
// 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(BinaryOperator &I);
Instruction *visitShiftInst(ShiftInst &I);
Instruction *visitCastInst(CastInst &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 *visitBranchInst(BranchInst &BI);
// visitInstruction - Specify what to return for unhandled instructions...
Instruction *visitInstruction(Instruction &I) { return 0; }
private:
Instruction *visitCallSite(CallSite CS);
bool transformConstExprCastCall(CallSite CS);
// InsertNewInstBefore - insert an instruction New before instruction Old
// in the program. Add the new instruction to the worklist.
//
Value *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;
}
public:
// 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) {
AddUsesToWorkList(I); // Add all modified instrs to worklist
I.replaceAllUsesWith(V);
return &I;
}
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);
Instruction *OptAndOp(Instruction *Op, ConstantIntegral *OpRHS,
ConstantIntegral *AndRHS, BinaryOperator &TheAnd);
};
RegisterOpt<InstCombiner> X("instcombine", "Combine redundant instructions");
}
// getComplexity: Assign a complexity or rank value to LLVM Values...
// 0 -> Constant, 1 -> Other, 2 -> Argument, 2 -> Unary, 3 -> OtherInst
static unsigned getComplexity(Value *V) {
if (isa<Instruction>(V)) {
if (BinaryOperator::isNeg(V) || BinaryOperator::isNot(V))
return 2;
return 3;
}
if (isa<Argument>(V)) return 2;
return isa<Constant>(V) ? 0 : 1;
}
// 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);
}
// getSignedIntegralType - Given an unsigned integral type, return the signed
// version of it that has the same size.
static const Type *getSignedIntegralType(const Type *Ty) {
switch (Ty->getPrimitiveID()) {
default: assert(0 && "Invalid unsigned integer type!"); abort();
case Type::UByteTyID: return Type::SByteTy;
case Type::UShortTyID: return Type::ShortTy;
case Type::UIntTyID: return Type::IntTy;
case Type::ULongTyID: return Type::LongTy;
}
}
// 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->getPrimitiveID()) {
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;
}
}
// 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(cast<BinaryOperator>(V));
// Constants can be considered to be negated values if they can be folded...
if (Constant *C = dyn_cast<Constant>(V))
return ConstantExpr::get(Instruction::Sub,
Constant::getNullValue(V->getType()), C);
return 0;
}
static Constant *NotConstant(Constant *C) {
return ConstantExpr::get(Instruction::Xor, C,
ConstantIntegral::getAllOnesValue(C->getType()));
}
static inline Value *dyn_castNotVal(Value *V) {
if (BinaryOperator::isNot(V))
return BinaryOperator::getNotArgument(cast<BinaryOperator>(V));
// Constants can be considered to be not'ed values...
if (ConstantIntegral *C = dyn_cast<ConstantIntegral>(V))
return NotConstant(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.
//
static inline Value *dyn_castFoldableMul(Value *V) {
if (V->hasOneUse() && V->getType()->isInteger())
if (Instruction *I = dyn_cast<Instruction>(V))
if (I->getOpcode() == Instruction::Mul)
if (isa<Constant>(I->getOperand(1)))
return I->getOperand(0);
return 0;
}
// dyn_castMaskingAnd - If this value is an And instruction masking a value with
// a constant, return the constant being anded with.
//
template<class ValueType>
static inline Constant *dyn_castMaskingAnd(ValueType *V) {
if (Instruction *I = dyn_cast<Instruction>(V))
if (I->getOpcode() == Instruction::And)
return dyn_cast<Constant>(I->getOperand(1));
// If this is a constant, it acts just like we were masking with it.
return dyn_cast<Constant>(V);
}
// Log2 - Calculate the log base 2 for the specified value if it is exactly a
// power of 2.
static unsigned Log2(uint64_t Val) {
assert(Val > 1 && "Values 0 and 1 should be handled elsewhere!");
unsigned Count = 0;
while (Val != 1) {
if (Val & 1) return 0; // Multiple bits set?
Val >>= 1;
++Count;
}
return Count;
}
/// 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();
// All of the instructions have a single use and have no side-effects,
// because of this, we can pull them all into the current basic block.
if (LHSI->getParent() != BB) {
// Move all of the instructions from root to LHSI into the current
// block.
Instruction *TmpLHSI = cast<Instruction>(Root.getOperand(0));
Instruction *LastUse = &Root;
while (TmpLHSI->getParent() == BB) {
LastUse = TmpLHSI;
TmpLHSI = cast<Instruction>(TmpLHSI->getOperand(0));
}
// Loop over all of the instructions in other blocks, moving them into
// the current one.
Value *TmpLHS = TmpLHSI;
do {
TmpLHSI = cast<Instruction>(TmpLHS);
// Remove from current block...
TmpLHSI->getParent()->getInstList().remove(TmpLHSI);
// Insert before the last instruction...
BB->getInstList().insert(LastUse, TmpLHSI);
TmpLHS = TmpLHSI->getOperand(0);
} while (TmpLHSI != LHSI);
}
// 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);
Root.replaceAllUsesWith(TmpLHSI); // Users now use TmpLHSI
TmpLHSI->setOperand(1, &Root); // TmpLHSI now uses the root
BB->getInstList().remove(&Root); // Remove root from the BB
BB->getInstList().insert(TmpLHSI, &Root); // Insert root before TmpLHSI
// Now propagate the ExtraOperand down the chain of instructions until we
// get to LHSI.
while (TmpLHSI != LHSI) {
Instruction *NextLHSI = cast<Instruction>(TmpLHSI->getOperand(0));
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 {
if (Constant *C1 = dyn_castMaskingAnd(LHS))
return ConstantExpr::get(Instruction::And, C1, C2)->isNullValue();
return false;
}
Instruction *apply(BinaryOperator &Add) const {
return BinaryOperator::create(Instruction::Or, Add.getOperand(0),
Add.getOperand(1));
}
};
Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
bool Changed = SimplifyCommutative(I);
Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
// X + 0 --> X
if (RHS == Constant::getNullValue(I.getType()))
return ReplaceInstUsesWith(I, LHS);
// X + X --> X << 1
if (I.getType()->isInteger())
if (Instruction *Result = AssociativeOpt(I, AddRHS(RHS))) return Result;
// -A + B --> B - A
if (Value *V = dyn_castNegVal(LHS))
return BinaryOperator::create(Instruction::Sub, RHS, V);
// A + -B --> A - B
if (!isa<Constant>(RHS))
if (Value *V = dyn_castNegVal(RHS))
return BinaryOperator::create(Instruction::Sub, LHS, V);
// X*C + X --> X * (C+1)
if (dyn_castFoldableMul(LHS) == RHS) {
Constant *CP1 =
ConstantExpr::get(Instruction::Add,
cast<Constant>(cast<Instruction>(LHS)->getOperand(1)),
ConstantInt::get(I.getType(), 1));
return BinaryOperator::create(Instruction::Mul, RHS, CP1);
}
// X + X*C --> X * (C+1)
if (dyn_castFoldableMul(RHS) == LHS) {
Constant *CP1 =
ConstantExpr::get(Instruction::Add,
cast<Constant>(cast<Instruction>(RHS)->getOperand(1)),
ConstantInt::get(I.getType(), 1));
return BinaryOperator::create(Instruction::Mul, LHS, CP1);
}
// (A & C1)+(B & C2) --> (A & C1)|(B & C2) iff C1&C2 == 0
if (Constant *C2 = dyn_castMaskingAnd(RHS))
if (Instruction *R = AssociativeOpt(I, AddMaskingAnd(C2))) return R;
if (ConstantInt *CRHS = dyn_cast<ConstantInt>(RHS)) {
if (Instruction *ILHS = dyn_cast<Instruction>(LHS)) {
switch (ILHS->getOpcode()) {
case Instruction::Xor:
// ~X + C --> (C-1) - X
if (ConstantInt *XorRHS = dyn_cast<ConstantInt>(ILHS->getOperand(1)))
if (XorRHS->isAllOnesValue())
return BinaryOperator::create(Instruction::Sub,
ConstantExpr::get(Instruction::Sub,
CRHS, ConstantInt::get(I.getType(), 1)),
ILHS->getOperand(0));
break;
default: break;
}
}
}
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()->getPrimitiveSize()*8;
return (CI->getRawValue() & ~(-1LL << NumBits)) == (1ULL << (NumBits-1));
}
static unsigned getTypeSizeInBits(const Type *Ty) {
return Ty == Type::BoolTy ? 1 : Ty->getPrimitiveSize()*8;
}
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::create(Instruction::Add, Op0, V);
if (ConstantInt *C = dyn_cast<ConstantInt>(Op0)) {
// Replace (-1 - A) with (~A)...
if (C->isAllOnesValue())
return BinaryOperator::createNot(Op1);
// C - ~X == X + (1+C)
if (BinaryOperator::isNot(Op1))
return BinaryOperator::create(Instruction::Add,
BinaryOperator::getNotArgument(cast<BinaryOperator>(Op1)),
ConstantExpr::get(Instruction::Add, C,
ConstantInt::get(I.getType(), 1)));
}
if (BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1))
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::create(Instruction::Add, 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);
Instruction *NewNot = BinaryOperator::createNot(OtherOp, "B.not", &I);
return BinaryOperator::create(Instruction::And, Op0, NewNot);
}
// X - X*C --> X * (1-C)
if (dyn_castFoldableMul(Op1I) == Op0) {
Constant *CP1 =
ConstantExpr::get(Instruction::Sub,
ConstantInt::get(I.getType(), 1),
cast<Constant>(cast<Instruction>(Op1)->getOperand(1)));
assert(CP1 && "Couldn't constant fold 1-C?");
return BinaryOperator::create(Instruction::Mul, Op0, CP1);
}
}
// X*C - X --> X * (C-1)
if (dyn_castFoldableMul(Op0) == Op1) {
Constant *CP1 =
ConstantExpr::get(Instruction::Sub,
cast<Constant>(cast<Instruction>(Op0)->getOperand(1)),
ConstantInt::get(I.getType(), 1));
assert(CP1 && "Couldn't constant fold C - 1?");
return BinaryOperator::create(Instruction::Mul, Op1, CP1);
}
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()->getPrimitiveSize()*8-1);
if (Opcode == Instruction::SetGT)
return RHSC->getValue() ==
(1ULL << (RHS->getType()->getPrimitiveSize()*8-1))-1;
}
return false;
}
Instruction *InstCombiner::visitMul(BinaryOperator &I) {
bool Changed = SimplifyCommutative(I);
Value *Op0 = I.getOperand(0);
// 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::create(Instruction::Mul, SI->getOperand(0),
ConstantExpr::get(Instruction::Shl, 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 (uint64_t C = Log2(Val)) // Replace X*(2^C) with X << C
return new ShiftInst(Instruction::Shl, Op0,
ConstantUInt::get(Type::UByteTy, C));
} else {
ConstantFP *Op1F = cast<ConstantFP>(Op1);
if (Op1F->isNullValue())
return ReplaceInstUsesWith(I, Op1);
// "In IEEE floating point, x*1 is not equivalent to x for nans. However,
// ANSI says we can drop signals, so we can do this anyway." (from GCC)
if (Op1F->getValue() == 1.0)
return ReplaceInstUsesWith(I, Op0); // Eliminate 'mul double %X, 1.0'
}
}
if (Value *Op0v = dyn_castNegVal(Op0)) // -X * -Y = X*Y
if (Value *Op1v = dyn_castNegVal(I.getOperand(1)))
return BinaryOperator::create(Instruction::Mul, 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->getPrimitiveSize()*8-1);
if (SCIOp0->getType()->isUnsigned()) {
const Type *NewTy = getSignedIntegralType(SCIOp0->getType());
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::create(Instruction::And, V, OtherOp);
}
}
}
return Changed ? &I : 0;
}
Instruction *InstCombiner::visitDiv(BinaryOperator &I) {
// div X, 1 == X
if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
if (RHS->equalsInt(1))
return ReplaceInstUsesWith(I, I.getOperand(0));
// 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 (uint64_t C = Log2(Val))
return new ShiftInst(Instruction::Shr, I.getOperand(0),
ConstantUInt::get(Type::UByteTy, C));
}
// 0 / X == 0, we don't need to preserve faults!
if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0)))
if (LHS->equalsInt(0))
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
return 0;
}
Instruction *InstCombiner::visitRem(BinaryOperator &I) {
if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
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 (Log2(Val))
return BinaryOperator::create(Instruction::And, I.getOperand(0),
ConstantUInt::get(I.getType(), Val-1));
}
// 0 % X == 0, we don't need to preserve faults!
if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0)))
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()->getPrimitiveSize()*8;
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()->getPrimitiveSize()*8;
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()->getPrimitiveSize()*8;
int64_t Val = -1; // All ones
Val <<= TypeBits-1; // Shift over to the right spot
return CS->getValue() == Val+1;
}
/// 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::get(Instruction::And, AndRHS, OpRHS);
switch (Op->getOpcode()) {
case Instruction::Xor:
if (Together->isNullValue()) {
// (X ^ C1) & C2 --> (X & C2) iff (C1&C2) == 0
return BinaryOperator::create(Instruction::And, X, AndRHS);
} else if (Op->hasOneUse()) {
// (X ^ C1) & C2 --> (X & C2) ^ (C1&C2)
std::string OpName = Op->getName(); Op->setName("");
Instruction *And = BinaryOperator::create(Instruction::And,
X, AndRHS, OpName);
InsertNewInstBefore(And, TheAnd);
return BinaryOperator::create(Instruction::Xor, And, Together);
}
break;
case Instruction::Or:
// (X | C1) & C2 --> X & C2 iff C1 & C1 == 0
if (Together->isNullValue())
return BinaryOperator::create(Instruction::And, X, AndRHS);
else {
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::create(Instruction::Or, X,
Together, Op0Name);
InsertNewInstBefore(Or, TheAnd);
return BinaryOperator::create(Instruction::And, 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.
unsigned long long AndRHSV = cast<ConstantInt>(AndRHS)->getRawValue();
// Clear bits that are not part of the constant.
AndRHSV &= (1ULL << AndRHS->getType()->getPrimitiveSize()*8)-1;
// If there is only one bit set...
if ((AndRHSV & (AndRHSV-1)) == 0) {
// 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.
unsigned long long 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::create(Instruction::And, X, AndRHS, Name);
InsertNewInstBefore(NewAnd, TheAnd);
return BinaryOperator::create(Instruction::Xor, 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 *CI = ConstantExpr::get(Instruction::And, AndRHS,
ConstantExpr::get(Instruction::Shl, AllOne, OpRHS));
if (CI != AndRHS) {
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 *CI = ConstantExpr::get(Instruction::And, AndRHS,
ConstantExpr::get(Instruction::Shr, AllOne, OpRHS));
if (CI != AndRHS) {
TheAnd.setOperand(1, CI);
return &TheAnd;
}
}
break;
}
return 0;
}
Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
bool Changed = SimplifyCommutative(I);
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
// and X, X = X and X, 0 == 0
if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
return ReplaceInstUsesWith(I, Op1);
// and X, -1 == X
if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
if (RHS->isAllOnesValue())
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 *X = Op0I->getOperand(0);
if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
if (Instruction *Res = OptAndOp(Op0I, Op0CI, RHS, I))
return Res;
}
}
Value *Op0NotVal = dyn_castNotVal(Op0);
Value *Op1NotVal = dyn_castNotVal(Op1);
// (~A & ~B) == (~(A | B)) - Demorgan's Law
if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
Instruction *Or = BinaryOperator::create(Instruction::Or, Op0NotVal,
Op1NotVal,I.getName()+".demorgan");
InsertNewInstBefore(Or, I);
return BinaryOperator::createNot(Or);
}
if (Op0NotVal == Op1 || Op1NotVal == Op0) // A & ~A == ~A & A == 0
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
// (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;
}
Instruction *InstCombiner::visitOr(BinaryOperator &I) {
bool Changed = SimplifyCommutative(I);
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
// 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 (RHS->isAllOnesValue())
return ReplaceInstUsesWith(I, Op1);
if (Instruction *Op0I = dyn_cast<Instruction>(Op0)) {
// (X & C1) | C2 --> (X | C2) & (C1|C2)
if (Op0I->getOpcode() == Instruction::And && isOnlyUse(Op0))
if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
std::string Op0Name = Op0I->getName(); Op0I->setName("");
Instruction *Or = BinaryOperator::create(Instruction::Or,
Op0I->getOperand(0), RHS,
Op0Name);
InsertNewInstBefore(Or, I);
return BinaryOperator::create(Instruction::And, Or,
ConstantExpr::get(Instruction::Or, RHS, Op0CI));
}
// (X ^ C1) | C2 --> (X | C2) ^ (C1&~C2)
if (Op0I->getOpcode() == Instruction::Xor && isOnlyUse(Op0))
if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
std::string Op0Name = Op0I->getName(); Op0I->setName("");
Instruction *Or = BinaryOperator::create(Instruction::Or,
Op0I->getOperand(0), RHS,
Op0Name);
InsertNewInstBefore(Or, I);
return BinaryOperator::create(Instruction::Xor, Or,
ConstantExpr::get(Instruction::And, Op0CI,
NotConstant(RHS)));
}
}
}
// (A & C1)|(A & C2) == A & (C1|C2)
if (Instruction *LHS = dyn_cast<BinaryOperator>(Op0))
if (Instruction *RHS = dyn_cast<BinaryOperator>(Op1))
if (LHS->getOperand(0) == RHS->getOperand(0))
if (Constant *C0 = dyn_castMaskingAnd(LHS))
if (Constant *C1 = dyn_castMaskingAnd(RHS))
return BinaryOperator::create(Instruction::And, LHS->getOperand(0),
ConstantExpr::get(Instruction::Or, C0, C1));
Value *Op0NotVal = dyn_castNotVal(Op0);
Value *Op1NotVal = dyn_castNotVal(Op1);
if (Op1 == Op0NotVal) // ~A | A == -1
return ReplaceInstUsesWith(I,
ConstantIntegral::getAllOnesValue(I.getType()));
if (Op0 == Op1NotVal) // A | ~A == -1
return ReplaceInstUsesWith(I,
ConstantIntegral::getAllOnesValue(I.getType()));
// (~A | ~B) == (~(A & B)) - Demorgan's Law
if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
Instruction *And = BinaryOperator::create(Instruction::And, Op0NotVal,
Op1NotVal,I.getName()+".demorgan",
&I);
WorkList.push_back(And);
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;
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);
// 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::get(Instruction::Sub,
Constant::getNullValue(Op0I0C->getType()), Op0I0C);
Constant *ConstantRHS = ConstantExpr::get(Instruction::Sub, NegOp0I0C,
ConstantInt::get(I.getType(), 1));
return BinaryOperator::create(Instruction::Add, Op0I->getOperand(1),
ConstantRHS);
}
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::get(Instruction::Sub,
Constant::getNullValue(Op0CI->getType()), Op0CI);
return BinaryOperator::create(Instruction::Sub,
ConstantExpr::get(Instruction::Sub, 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::get(Instruction::And, RHS, Op0CI)->isNullValue())
return BinaryOperator::create(Instruction::Or, Op0, RHS);
break;
case Instruction::Or:
// (X | C1) ^ C2 --> (X | C1) & ~C2 iff (C1&C2) == C2
if (ConstantExpr::get(Instruction::And, RHS, Op0CI) == RHS)
return BinaryOperator::create(Instruction::And, Op0,
NotConstant(RHS));
break;
default: break;
}
}
}
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 = BinaryOperator::createNot(Op1, Op1->getName()+".not", &I);
WorkList.push_back(cast<Instruction>(NotB));
return BinaryOperator::create(Instruction::And, 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
if (Constant *C1 = dyn_castMaskingAnd(Op0))
if (Constant *C2 = dyn_castMaskingAnd(Op1))
if (ConstantExpr::get(Instruction::And, C1, C2)->isNullValue())
return BinaryOperator::create(Instruction::Or, 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;
}
// AddOne, SubOne - Add or subtract a constant one from an integer constant...
static Constant *AddOne(ConstantInt *C) {
Constant *Result = ConstantExpr::get(Instruction::Add, C,
ConstantInt::get(C->getType(), 1));
assert(Result && "Constant folding integer addition failed!");
return Result;
}
static Constant *SubOne(ConstantInt *C) {
Constant *Result = ConstantExpr::get(Instruction::Sub, C,
ConstantInt::get(C->getType(), 1));
assert(Result && "Constant folding integer addition failed!");
return Result;
}
// 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;
}
Instruction *InstCombiner::visitSetCondInst(BinaryOperator &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)));
// setcc <global/alloca*>, 0 - Global/Stack value addresses are never null!
if (isa<ConstantPointerNull>(Op1) &&
(isa<GlobalValue>(Op0) || isa<AllocaInst>(Op0)))
return ReplaceInstUsesWith(I, ConstantBool::get(!isTrueWhenEqual(I)));
// setcc's with boolean values can always be turned into bitwise operations
if (Ty == Type::BoolTy) {
// If this is <, >, or !=, we can change this into a simple xor instruction
if (!isTrueWhenEqual(I))
return BinaryOperator::create(Instruction::Xor, Op0, Op1);
// Otherwise we need to make a temporary intermediate instruction and insert
// it into the instruction stream. This is what we are after:
//
// seteq bool %A, %B -> ~(A^B)
// setle bool %A, %B -> ~A | B
// setge bool %A, %B -> A | ~B
//
if (I.getOpcode() == Instruction::SetEQ) { // seteq case
Instruction *Xor = BinaryOperator::create(Instruction::Xor, Op0, Op1,
I.getName()+"tmp");
InsertNewInstBefore(Xor, I);
return BinaryOperator::createNot(Xor);
}
// Handle the setXe cases...
assert(I.getOpcode() == Instruction::SetGE ||
I.getOpcode() == Instruction::SetLE);
if (I.getOpcode() == Instruction::SetGE)
std::swap(Op0, Op1); // Change setge -> setle
// Now we just have the SetLE case.
Instruction *Not = BinaryOperator::createNot(Op0, I.getName()+"tmp");
InsertNewInstBefore(Not, I);
return BinaryOperator::create(Instruction::Or, Not, Op1);
}
// Check to see if we are doing one of many comparisons against constant
// integers at the end of their ranges...
//
if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
// 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::Add:
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::get(Instruction::Xor, 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 = NotConstant(CI);
if (!ConstantExpr::get(Instruction::And, 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::get(Instruction::And, CI,
NotConstant(BOC))->isNullValue())
return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
// 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 = getSignedIntegralType(BOC->getType());
CastInst *NewCI = new CastInst(X,DestTy,X->getName()+".signed");
InsertNewInstBefore(NewCI, I);
X = NewCI;
}
return new SetCondInst(isSetNE ? Instruction::SetLT :
Instruction::SetGE, X,
Constant::getNullValue(X->getType()));
}
}
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->getPrimitiveSize();
if (SrcTy != Cast->getType() && SrcTy->isInteger() &&
SrcTySize == Cast->getType()->getPrimitiveSize()) {
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::create(Instruction::SetGT, CastOp,
ConstantUInt::get(SrcTy, (1ULL << (SrcTySize*8-1))-1));
else if (I.getOpcode() == Instruction::SetGT &&
cast<ConstantSInt>(CI)->getValue() == -1)
// X > -1 => x < 128
return BinaryOperator::create(Instruction::SetGT, CastOp,
ConstantUInt::get(SrcTy, 1ULL << (SrcTySize*8-1)));
} else {
ConstantUInt *CUI = cast<ConstantUInt>(CI);
if (I.getOpcode() == Instruction::SetLT &&
CUI->getValue() == 1ULL << (SrcTySize*8-1))
// X < 128 => X > -1
return BinaryOperator::create(Instruction::SetGT, CastOp,
ConstantSInt::get(SrcTy, -1));
else if (I.getOpcode() == Instruction::SetGT &&
CUI->getValue() == (1ULL << (SrcTySize*8-1))-1)
// X > 127 => X < 0
return BinaryOperator::create(Instruction::SetLT, CastOp,
Constant::getNullValue(SrcTy));
}
}
}
}
// 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::create(Instruction::SetEQ, Op0, Op1);
if (I.getOpcode() == Instruction::SetGT) // A > MIN -> A != MIN
return BinaryOperator::create(Instruction::SetNE, 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::create(Instruction::SetEQ, Op0, Op1);
if (I.getOpcode() == Instruction::SetLT) // A < MAX -> A != MAX
return BinaryOperator::create(Instruction::SetNE, 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::create(Instruction::SetEQ, Op0, SubOne(CI));
if (I.getOpcode() == Instruction::SetGE) // A >= MIN-1 -> A != MIN
return BinaryOperator::create(Instruction::SetNE, Op0, SubOne(CI));
} else if (isMaxValueMinusOne(CI)) {
if (I.getOpcode() == Instruction::SetGT) // A > MAX-1 -> A == MAX
return BinaryOperator::create(Instruction::SetEQ, Op0, AddOne(CI));
if (I.getOpcode() == Instruction::SetLE) // A <= MAX-1 -> A != MAX
return BinaryOperator::create(Instruction::SetNE, 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::create(Instruction::SetLT, Op0, AddOne(CI));
if (I.getOpcode() == Instruction::SetGE)
return BinaryOperator::create(Instruction::SetGT, Op0, SubOne(CI));
}
// 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<Argument>(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.
if (ConstantInt *ConstantRHS = dyn_cast<ConstantInt>(Op1)) {
const Type *SrcTy = CastOp0->getType();
const Type *DestTy = Op0->getType();
if (SrcTy->getPrimitiveSize() < DestTy->getPrimitiveSize() &&
(SrcTy->isUnsigned() || SrcTy == Type::BoolTy)) {
// Ok, we have an expansion of operand 0 into a new type. Get the
// constant value, masink off bits which are not set in the RHS. These
// could be set if the destination value is signed.
uint64_t ConstVal = ConstantRHS->getRawValue();
ConstVal &= (1ULL << DestTy->getPrimitiveSize()*8)-1;
// If the constant we are comparing it with has high bits set, which
// don't exist in the original value, the values could never be equal,
// because the source would be zero extended.
unsigned SrcBits =
SrcTy == Type::BoolTy ? 1 : SrcTy->getPrimitiveSize()*8;
bool HasSignBit = ConstVal & (1ULL << (DestTy->getPrimitiveSize()*8-1));
if (ConstVal & ~((1ULL << SrcBits)-1)) {
switch (I.getOpcode()) {
default: assert(0 && "Unknown comparison type!");
case Instruction::SetEQ:
return ReplaceInstUsesWith(I, ConstantBool::False);
case Instruction::SetNE:
return ReplaceInstUsesWith(I, ConstantBool::True);
case Instruction::SetLT:
case Instruction::SetLE:
if (DestTy->isSigned() && HasSignBit)
return ReplaceInstUsesWith(I, ConstantBool::False);
return ReplaceInstUsesWith(I, ConstantBool::True);
case Instruction::SetGT:
case Instruction::SetGE:
if (DestTy->isSigned() && HasSignBit)
return ReplaceInstUsesWith(I, ConstantBool::True);
return ReplaceInstUsesWith(I, ConstantBool::False);
}
}
// Otherwise, we can replace the setcc with a setcc of the smaller
// operand value.
Op1 = ConstantExpr::getCast(cast<Constant>(Op1), SrcTy);
return BinaryOperator::create(I.getOpcode(), CastOp0, Op1);
}
}
}
return Changed ? &I : 0;
}
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);
// 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);
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()->getPrimitiveSize()*8;
if (CUI->getValue() >= TypeBits &&
(!Op0->getType()->isSigned() || isLeftShift))
return ReplaceInstUsesWith(I, Constant::getNullValue(Op0->getType()));
// ((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::create(Instruction::Mul, BO->getOperand(0),
ConstantExpr::get(Instruction::Shl, BOOp, CUI));
// 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 (Op0->hasOneUse())
if (BinaryOperator *Op0BO = dyn_cast<BinaryOperator>(Op0))
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::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 = ShiftAmt1C->getValue();
unsigned ShiftAmt2 = 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...
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::get(Instruction::Shl, C, ShiftAmt1C);
else
C = ConstantExpr::get(Instruction::Shr, C, ShiftAmt1C);
Instruction *Mask =
BinaryOperator::create(Instruction::And, 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));
}
}
}
}
return 0;
}
// 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) {
// 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;
// Allow free casting and conversion of sizes as long as the sign doesn't
// change...
if (SrcTy->isIntegral() && MidTy->isIntegral() && DstTy->isIntegral()) {
unsigned SrcSize = SrcTy->getPrimitiveSize();
unsigned MidSize = MidTy->getPrimitiveSize();
unsigned DstSize = DstTy->getPrimitiveSize();
// Cases where we are monotonically decreasing the size of the type are
// always ok, regardless of what sign changes are going on.
//
if (SrcSize >= MidSize && MidSize >= DstSize)
return true;
// Cases where the source and destination type are the same, but the middle
// type is bigger are noops.
//
if (SrcSize == DstSize && MidSize > SrcSize)
return true;
// If we are monotonically growing, things are more complex.
//
if (SrcSize <= MidSize && MidSize <= DstSize) {
// We have eight combinations of signedness to worry about. Here's the
// table:
static const int SignTable[8] = {
// CODE, SrcSigned, MidSigned, DstSigned, Comment
1, // U U U Always ok
1, // U U S Always ok
3, // U S U Ok iff SrcSize != MidSize
3, // U S S Ok iff SrcSize != MidSize
0, // S U U Never ok
2, // S U S Ok iff MidSize == DstSize
1, // S S U Always ok
1, // S S S Always ok
};
// Choose an action based on the current entry of the signtable that this
// cast of cast refers to...
unsigned Row = SrcTy->isSigned()*4+MidTy->isSigned()*2+DstTy->isSigned();
switch (SignTable[Row]) {
case 0: return false; // Never ok
case 1: return true; // Always ok
case 2: return MidSize == DstSize; // Ok iff MidSize == DstSize
case 3: // Ok iff SrcSize != MidSize
return SrcSize != MidSize || SrcTy == Type::BoolTy;
default: assert(0 && "Bad entry in sign table!");
}
}
}
// Otherwise, we cannot succeed. Specifically we do not want to allow things
// like: short -> ushort -> uint, because this can create wrong results if
// the input short is negative!
//
return false;
}
static bool ValueRequiresCast(const Value *V, const Type *Ty) {
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))
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;
}
// 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 casting the result of another cast instruction, try to eliminate this
// one!
//
if (CastInst *CSrc = dyn_cast<CastInst>(Src)) {
if (isEliminableCastOfCast(CSrc->getOperand(0)->getType(),
CSrc->getType(), CI.getType())) {
// 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 (CSrc->getOperand(0)->getType() == CI.getType() &&
CI.getType()->isInteger() && CSrc->getType()->isInteger() &&
CI.getType()->isUnsigned() && CSrc->getType()->isUnsigned() &&
CSrc->getType()->getPrimitiveSize() < CI.getType()->getPrimitiveSize()){
assert(CSrc->getType() != Type::ULongTy &&
"Cannot have type bigger than ulong!");
uint64_t AndValue = (1ULL << CSrc->getType()->getPrimitiveSize()*8)-1;
Constant *AndOp = ConstantUInt::get(CI.getType(), AndValue);
return BinaryOperator::create(Instruction::And, CSrc->getOperand(0),
AndOp);
}
}
// 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 (AI->hasOneUse() && !AI->isArrayAllocation())
if (const PointerType *PTy = dyn_cast<PointerType>(CI.getType())) {
// Get the type really allocated and the type casted to...
const Type *AllocElTy = AI->getAllocatedType();
unsigned AllocElTySize = TD->getTypeSize(AllocElTy);
const Type *CastElTy = PTy->getElementType();
unsigned CastElTySize = TD->getTypeSize(CastElTy);
// If the allocation is for an even multiple of the cast type size
if (CastElTySize && (AllocElTySize % CastElTySize == 0)) {
Value *Amt = ConstantUInt::get(Type::UIntTy,
AllocElTySize/CastElTySize);
std::string Name = AI->getName(); AI->setName("");
AllocationInst *New;
if (isa<MallocInst>(AI))
New = new MallocInst(CastElTy, Amt, Name);
else
New = new AllocaInst(CastElTy, Amt, Name);
InsertNewInstBefore(New, CI);
return ReplaceInstUsesWith(CI, New);
}
}
// 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 = getTypeSizeInBits(Src->getType());
unsigned DestBitSize = getTypeSizeInBits(DestTy);
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) ||
!ValueRequiresCast(Op0, DestTy)) {
Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI);
Value *Op1c = InsertOperandCastBefore(Op1, DestTy, SrcI);
return BinaryOperator::create(cast<BinaryOperator>(SrcI)
->getOpcode(), Op0c, Op1c);
}
}
break;
case Instruction::Shl:
// Allow changing the sign of the source operand. Do not allow changing
// the size of the shift, UNLESS the shift amount is a constant. We
// 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;
}
}
return 0;
}
// CallInst simplification
//
Instruction *InstCombiner::visitCallInst(CallInst &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();
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<ConstantPointerRef>(CE->getOperand(0)))
return false;
ConstantPointerRef *CPR = cast<ConstantPointerRef>(CE->getOperand(0));
if (!isa<Function>(CPR->getValue())) return false;
Function *Callee = cast<Function>(CPR->getValue());
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 {
Instruction *Cast = new CastInst(*AI, ParamTy, "tmp");
InsertNewInstBefore(Cast, *Caller);
Args.push_back(Cast);
}
}
// 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);
} else {
NC = new CallInst(Callee, Args, Caller->getName(), Caller);
}
// 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);
}
AddUsesToWorkList(*Caller);
} else {
NV = Constant::getNullValue(Caller->getType());
}
}
if (Caller->getType() != Type::VoidTy && !Caller->use_empty())
Caller->replaceAllUsesWith(NV);
Caller->getParent()->getInstList().erase(Caller);
removeFromWorkList(Caller);
return true;
}
// PHINode simplification
//
Instruction *InstCombiner::visitPHINode(PHINode &PN) {
if (Value *V = hasConstantValue(&PN))
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!
}
}
return 0;
}
Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
// Is it 'getelementptr %P, long 0' or 'getelementptr %P'
// If so, eliminate the noop.
if (GEP.getNumOperands() == 1)
return ReplaceInstUsesWith(GEP, GEP.getOperand(0));
bool HasZeroPointerIndex = false;
if (Constant *C = dyn_cast<Constant>(GEP.getOperand(1)))
HasZeroPointerIndex = C->isNullValue();
if (GEP.getNumOperands() == 2 && HasZeroPointerIndex)
return ReplaceInstUsesWith(GEP, GEP.getOperand(0));
// 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.
//
if (GetElementPtrInst *Src = dyn_cast<GetElementPtrInst>(GEP.getOperand(0))) {
std::vector<Value *> Indices;
// Can we combine the two pointer arithmetics offsets?
if (Src->getNumOperands() == 2 && isa<Constant>(Src->getOperand(1)) &&
isa<Constant>(GEP.getOperand(1))) {
// Replace: gep (gep %P, long C1), long C2, ...
// With: gep %P, long (C1+C2), ...
Value *Sum = ConstantExpr::get(Instruction::Add,
cast<Constant>(Src->getOperand(1)),
cast<Constant>(GEP.getOperand(1)));
assert(Sum && "Constant folding of longs failed!?");
GEP.setOperand(0, Src->getOperand(0));
GEP.setOperand(1, Sum);
AddUsesToWorkList(*Src); // Reduce use count of Src
return &GEP;
} else if (Src->getNumOperands() == 2) {
// Replace: gep (gep %P, long B), long A, ...
// With: T = long A+B; gep %P, T, ...
//
Value *Sum = BinaryOperator::create(Instruction::Add, Src->getOperand(1),
GEP.getOperand(1),
Src->getName()+".sum", &GEP);
GEP.setOperand(0, Src->getOperand(0));
GEP.setOperand(1, Sum);
WorkList.push_back(cast<Instruction>(Sum));
return &GEP;
} else if (*GEP.idx_begin() == Constant::getNullValue(Type::LongTy) &&
Src->getNumOperands() != 1) {
// Otherwise we can do the fold if the first index of the GEP is a zero
Indices.insert(Indices.end(), Src->idx_begin(), Src->idx_end());
Indices.insert(Indices.end(), GEP.idx_begin()+1, GEP.idx_end());
} else if (Src->getOperand(Src->getNumOperands()-1) ==
Constant::getNullValue(Type::LongTy)) {
// If the src gep ends with a constant array index, merge this get into
// it, even if we have a non-zero array index.
Indices.insert(Indices.end(), Src->idx_begin(), Src->idx_end()-1);
Indices.insert(Indices.end(), GEP.idx_begin(), GEP.idx_end());
}
if (!Indices.empty())
return new GetElementPtrInst(Src->getOperand(0), Indices, GEP.getName());
} else if (GlobalValue *GV = dyn_cast<GlobalValue>(GEP.getOperand(0))) {
// 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(ConstantPointerRef::get(GV), Indices);
// Replace all uses of the GEP with the new constexpr...
return ReplaceInstUsesWith(GEP, CE);
}
} else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP.getOperand(0))) {
if (CE->getOpcode() == Instruction::Cast) {
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[];"
//
Constant *X = CE->getOperand(0);
const PointerType *CPTy = cast<PointerType>(CE->getType());
if (const PointerType *XTy = dyn_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;
}
}
}
}
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.getName(), &AI);
else {
assert(isa<AllocaInst>(AI) && "Unknown type of allocation inst!");
New = new AllocaInst(NewTy, 0, AI.getName(), &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...
//
std::vector<Value*> Idx(2, Constant::getNullValue(Type::LongTy));
Value *V = new GetElementPtrInst(New, Idx, New->getName()+".sub", It);
// Now make everything use the getelementptr instead of the original
// allocation.
ReplaceInstUsesWith(AI, V);
return &AI;
}
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;
}
return 0;
}
/// GetGEPGlobalInitializer - Given a constant, and a getelementptr
/// constantexpr, return the constant value being addressed by the constant
/// expression, or null if something is funny.
///
static Constant *GetGEPGlobalInitializer(Constant *C, ConstantExpr *CE) {
if (CE->getOperand(1) != Constant::getNullValue(Type::LongTy))
return 0; // Do not allow stepping over the value!
// Loop over all of the operands, tracking down which value we are
// addressing...
for (unsigned i = 2, e = CE->getNumOperands(); i != e; ++i)
if (ConstantUInt *CU = dyn_cast<ConstantUInt>(CE->getOperand(i))) {
ConstantStruct *CS = dyn_cast<ConstantStruct>(C);
if (CS == 0) return 0;
if (CU->getValue() >= CS->getValues().size()) return 0;
C = cast<Constant>(CS->getValues()[CU->getValue()]);
} else if (ConstantSInt *CS = dyn_cast<ConstantSInt>(CE->getOperand(i))) {
ConstantArray *CA = dyn_cast<ConstantArray>(C);
if (CA == 0) return 0;
if ((uint64_t)CS->getValue() >= CA->getValues().size()) return 0;
C = cast<Constant>(CA->getValues()[CS->getValue()]);
} else
return 0;
return C;
}
Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
Value *Op = LI.getOperand(0);
if (LI.isVolatile()) return 0;
if (ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(Op))
Op = CPR->getValue();
// 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 (ConstantPointerRef *G=dyn_cast<ConstantPointerRef>(CE->getOperand(0)))
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(G->getValue()))
if (GV->isConstant() && !GV->isExternal())
if (Constant *V = GetGEPGlobalInitializer(GV->getInitializer(), CE))
return ReplaceInstUsesWith(LI, V);
return 0;
}
Instruction *InstCombiner::visitBranchInst(BranchInst &BI) {
// Change br (not X), label True, label False to: br X, label False, True
if (BI.isConditional() && !isa<Constant>(BI.getCondition()))
if (Value *V = dyn_castNotVal(BI.getCondition())) {
BasicBlock *TrueDest = BI.getSuccessor(0);
BasicBlock *FalseDest = BI.getSuccessor(1);
// Swap Destinations and condition...
BI.setCondition(V);
BI.setSuccessor(0, FalseDest);
BI.setSuccessor(1, TrueDest);
return &BI;
}
return 0;
}
void InstCombiner::removeFromWorkList(Instruction *I) {
WorkList.erase(std::remove(WorkList.begin(), WorkList.end(), I),
WorkList.end());
}
bool InstCombiner::runOnFunction(Function &F) {
bool Changed = false;
TD = &getAnalysis<TargetData>();
WorkList.insert(WorkList.end(), inst_begin(F), inst_end(F));
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)
for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
if (Instruction *Op = dyn_cast<Instruction>(I->getOperand(i)))
WorkList.push_back(Op);
++NumDeadInst;
I->getParent()->getInstList().erase(I);
removeFromWorkList(I);
continue;
}
// Instruction isn't dead, see if we can constant propagate it...
if (Constant *C = ConstantFoldInstruction(I)) {
// Add operands to the worklist...
for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
if (Instruction *Op = dyn_cast<Instruction>(I->getOperand(i)))
WorkList.push_back(Op);
ReplaceInstUsesWith(*I, C);
++NumConstProp;
I->getParent()->getInstList().erase(I);
removeFromWorkList(I);
continue;
}
// 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) {
// Instructions can end up on the worklist more than once. Make sure
// we do not process an instruction that has been deleted.
removeFromWorkList(I);
// 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();
InstParent->getInstList().insert(I, Result);
// Everything uses the new instruction now...
I->replaceAllUsesWith(Result);
// Erase the old instruction.
InstParent->getInstList().erase(I);
} else {
BasicBlock::iterator II = I;
// If the instruction was modified, it's possible that it is now dead.
// if so, remove it.
if (dceInstruction(II)) {
// Instructions may end up in the worklist more than once. Erase them
// all.
removeFromWorkList(I);
Result = 0;
}
}
if (Result) {
WorkList.push_back(Result);
AddUsesToWorkList(*Result);
}
Changed = true;
}
}
return Changed;
}
Pass *llvm::createInstructionCombiningPass() {
return new InstCombiner();
}
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