> URL: http://llvm.org/viewvc/llvm-project?rev=42582&view=rev > Log: > Tone down an overzealous optimization.
Nice catch! -Chris > > Modified: > llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp > > Modified: llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp > URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/ > Scalar/InstructionCombining.cpp?rev=42582&r1=42581&r2=42582&view=diff > > ====================================================================== > ======== > --- llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp > (original) > +++ llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp Wed > Oct 3 12:45:27 2007 > @@ -7354,8 +7354,17 @@ > 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 @@ > > } 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); > > > _______________________________________________ > llvm-commits mailing list > llvm-commits@cs.uiuc.edu > http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits _______________________________________________ llvm-commits mailing list llvm-commits@cs.uiuc.edu http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
