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minor cleanups, teach instcombine that sitofp/uitofp cannot

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produce a negative zero.

llvm-svn: 51272
This commit is contained in:
Chris Lattner 2008-05-19 20:27:56 +00:00
parent 63c384df1e
commit 92599bcc72
1 changed files with 8 additions and 3 deletions
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11
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -834,10 +834,11 @@ void InstCombiner::ComputeMaskedBits(Value *V, const APInt &Mask,
case Instruction::IntToPtr:
// We can't handle these if we don't know the pointer size.
if (!TD) return;
// Fall through and handle them the same as zext/trunc.
// FALL THROUGH and handle them the same as zext/trunc.
case Instruction::ZExt:
case Instruction::Trunc: {
// All these have integer operands
// Note that we handle pointer operands here because of inttoptr/ptrtoint
// which fall through here.
const Type *SrcTy = I->getOperand(0)->getType();
uint32_t SrcBitWidth = TD ?
TD->getTypeSizeInBits(SrcTy) :
@ -2339,13 +2340,17 @@ static bool CannotBeNegativeZero(const Value *V) {
if (const ConstantFP *CFP = dyn_cast<ConstantFP>(V))
return !CFP->getValueAPF().isNegZero();
// (add x, 0.0) is guaranteed to return +0.0, not -0.0.
if (const Instruction *I = dyn_cast<Instruction>(V)) {
// (add x, 0.0) is guaranteed to return +0.0, not -0.0.
if (I->getOpcode() == Instruction::Add &&
isa<ConstantFP>(I->getOperand(1)) &&
cast<ConstantFP>(I->getOperand(1))->isNullValue())
return true;
// sitofp and uitofp turn into +0.0 for zero.
if (isa<SIToFPInst>(I) || isa<UIToFPInst>(I))
return true;
if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(I))
if (II->getIntrinsicID() == Intrinsic::sqrt)
return CannotBeNegativeZero(II->getOperand(1));