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| author | Dale Johannesen <dalej@apple.com> | 2007-10-03 17:45:27 +0000 |
|---|---|---|
| committer | Dale Johannesen <dalej@apple.com> | 2007-10-03 17:45:27 +0000 |
| commit | 9d559cfff5b2ee00819a633122301a405709473f (patch) | |
| tree | d23a9a1b02af4ee3d383f72be7249729041e691c /llvm/lib/Transforms/Scalar/InstructionCombining.cpp | |
| parent | 87a3dbe743223e5c38c10ceac61d7becef9c5c4f (diff) | |
| download | bcm5719-llvm-9d559cfff5b2ee00819a633122301a405709473f.tar.gz bcm5719-llvm-9d559cfff5b2ee00819a633122301a405709473f.zip | |
Tone down an overzealous optimization.
llvm-svn: 42582
Diffstat (limited to 'llvm/lib/Transforms/Scalar/InstructionCombining.cpp')
| -rw-r--r-- | llvm/lib/Transforms/Scalar/InstructionCombining.cpp | 24 |
1 files changed, 21 insertions, 3 deletions
diff --git a/llvm/lib/Transforms/Scalar/InstructionCombining.cpp b/llvm/lib/Transforms/Scalar/InstructionCombining.cpp index 3a7d1018c40..2311f1eb5a3 100644 --- a/llvm/lib/Transforms/Scalar/InstructionCombining.cpp +++ b/llvm/lib/Transforms/Scalar/InstructionCombining.cpp @@ -7354,8 +7354,17 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) { if (FCmpInst *FCI = dyn_cast<FCmpInst>(CondVal)) { if (FCI->getOperand(0) == TrueVal && FCI->getOperand(1) == FalseVal) { // 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); + } // Transform (X != Y) ? X : Y -> X if (FCI->getPredicate() == FCmpInst::FCMP_ONE) return ReplaceInstUsesWith(SI, TrueVal); @@ -7363,8 +7372,17 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) { } else if (FCI->getOperand(0) == FalseVal && FCI->getOperand(1) == TrueVal){ // Transform (X == Y) ? Y : X -> X - if (FCI->getPredicate() == FCmpInst::FCMP_OEQ) - return ReplaceInstUsesWith(SI, FalseVal); + 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); + } // Transform (X != Y) ? Y : X -> Y if (FCI->getPredicate() == FCmpInst::FCMP_ONE) return ReplaceInstUsesWith(SI, TrueVal); |
