From 24ff8346713d1ff9b5fbdf27dcc6e131846c68ed Mon Sep 17 00:00:00 2001 From: Jim Grosbach Date: Fri, 30 Sep 2011 18:45:50 +0000 Subject: float comparison to double 'zero' constant can just be a float 'zero.' InstCombine was incorrectly considering the conversion of the constant zero to be unsafe. We want to transform: define float @bar(float %x) nounwind readnone optsize ssp { %conv = fpext float %x to double %cmp = fcmp olt double %conv, 0.000000e+00 %conv1 = zext i1 %cmp to i32 %conv2 = sitofp i32 %conv1 to float ret float %conv2 } Into: define float @bar(float %x) nounwind readnone optsize ssp { %cmp = fcmp olt float %x, 0.000000e+00 ; <---- This %conv1 = zext i1 %cmp to i32 %conv2 = sitofp i32 %conv1 to float ret float %conv2 } rdar://10215914 llvm-svn: 140869 --- llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) (limited to 'llvm/lib/Transforms') diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp index d2faab52152..26432d2eed5 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp @@ -2837,10 +2837,13 @@ Instruction *InstCombiner::visitFCmpInst(FCmpInst &I) { APFloat F = RHSF->getValueAPF(); F.convert(*Sem, APFloat::rmNearestTiesToEven, &Lossy); - // Avoid lossy conversions and denormals. + // Avoid lossy conversions and denormals. Zero is a special case + // that's OK to convert. + F.clearSign(); if (!Lossy && - F.compare(APFloat::getSmallestNormalized(*Sem)) != - APFloat::cmpLessThan) + ((F.compare(APFloat::getSmallestNormalized(*Sem)) != + APFloat::cmpLessThan) || F.isZero())) + return new FCmpInst(I.getPredicate(), LHSExt->getOperand(0), ConstantFP::get(RHSC->getContext(), F)); break; -- cgit v1.2.3