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Tone down an overzealous optimization. 

llvm-svn: 42582
This commit is contained in:
Dale Johannesen 2007-10-03 17:45:27 +00:00
parent 87a3dbe743
commit 9d559cfff5
1 changed files with 21 additions and 3 deletions
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24
llvm/lib/Transforms/Scalar/InstructionCombining.cpp
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@ -7354,8 +7354,17 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
if (FCmpInst *FCI = dyn_cast<FCmpInst>(CondVal)) { if (FCmpInst *FCI = dyn_cast<FCmpInst>(CondVal)) {
if (FCI->getOperand(0) == TrueVal && FCI->getOperand(1) == FalseVal) { if (FCI->getOperand(0) == TrueVal && FCI->getOperand(1) == FalseVal) {
// Transform (X == Y) ? X : Y -> Y // Transform (X == Y) ? X : Y -> Y
if (FCI->getPredicate() == FCmpInst::FCMP_OEQ) if (FCI->getPredicate() == FCmpInst::FCMP_OEQ) {
// This is not safe in general for floating point:
// consider X== -0, Y== +0.
// It becomes safe if either operand is a nonzero constant.
ConstantFP *CFPt, *CFPf;
if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
!CFPt->getValueAPF().isZero()) ||
((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
!CFPf->getValueAPF().isZero()))
return ReplaceInstUsesWith(SI, FalseVal); return ReplaceInstUsesWith(SI, FalseVal);
}
// Transform (X != Y) ? X : Y -> X // Transform (X != Y) ? X : Y -> X
if (FCI->getPredicate() == FCmpInst::FCMP_ONE) if (FCI->getPredicate() == FCmpInst::FCMP_ONE)
return ReplaceInstUsesWith(SI, TrueVal); return ReplaceInstUsesWith(SI, TrueVal);
@ -7363,8 +7372,17 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
} else if (FCI->getOperand(0) == FalseVal && FCI->getOperand(1) == TrueVal){ } else if (FCI->getOperand(0) == FalseVal && FCI->getOperand(1) == TrueVal){
// Transform (X == Y) ? Y : X -> X // Transform (X == Y) ? Y : X -> X
if (FCI->getPredicate() == FCmpInst::FCMP_OEQ) if (FCI->getPredicate() == FCmpInst::FCMP_OEQ) {
return ReplaceInstUsesWith(SI, FalseVal); // This is not safe in general for floating point:
// consider X== -0, Y== +0.
// It becomes safe if either operand is a nonzero constant.
ConstantFP *CFPt, *CFPf;
if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
!CFPt->getValueAPF().isZero()) ||
((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
!CFPf->getValueAPF().isZero()))
return ReplaceInstUsesWith(SI, FalseVal);
}
// Transform (X != Y) ? Y : X -> Y // Transform (X != Y) ? Y : X -> Y
if (FCI->getPredicate() == FCmpInst::FCMP_ONE) if (FCI->getPredicate() == FCmpInst::FCMP_ONE)
return ReplaceInstUsesWith(SI, TrueVal); return ReplaceInstUsesWith(SI, TrueVal);