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Fix another infinite loop in InstCombine

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Summary:
InstCombine infinite-loops for the testcase added
It is because InstCombine is generating instructions that can be
optimized by itself. Fix by not optimizing frem if the optimized
type is the same as original type.
rdar://problem/19150820

Reviewers: majnemer

Differential Revision: http://reviews.llvm.org/D6634

llvm-svn: 224097
This commit is contained in:
Steven Wu 2014-12-12 04:34:07 +00:00
parent c1a6f36235
commit 896d3dd47b
2 changed files with 24 additions and 9 deletions
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21
lib/Transforms/InstCombine/InstCombineCasts.cpp
View File

@ -1269,16 +1269,19 @@ Instruction *InstCombiner::visitFPTrunc(FPTruncInst &CI) {
// type of OpI doesn't enter into things at all. We simply evaluate
// in whichever source type is larger, then convert to the
// destination type.
if (LHSWidth < SrcWidth)
LHSOrig = Builder->CreateFPExt(LHSOrig, RHSOrig->getType());
else if (RHSWidth <= SrcWidth)
RHSOrig = Builder->CreateFPExt(RHSOrig, LHSOrig->getType());
if (LHSOrig != OpI->getOperand(0) || RHSOrig != OpI->getOperand(1)) {
Value *ExactResult = Builder->CreateFRem(LHSOrig, RHSOrig);
if (Instruction *RI = dyn_cast<Instruction>(ExactResult))
RI->copyFastMathFlags(OpI);
return CastInst::CreateFPCast(ExactResult, CI.getType());
if (SrcWidth != OpWidth) {
if (LHSWidth < SrcWidth)
LHSOrig = Builder->CreateFPExt(LHSOrig, RHSOrig->getType());
else if (RHSWidth <= SrcWidth)
RHSOrig = Builder->CreateFPExt(RHSOrig, LHSOrig->getType());
if (LHSOrig != OpI->getOperand(0) || RHSOrig != OpI->getOperand(1)) {
Value *ExactResult = Builder->CreateFRem(LHSOrig, RHSOrig);
if (Instruction *RI = dyn_cast<Instruction>(ExactResult))
RI->copyFastMathFlags(OpI);
return CastInst::CreateFPCast(ExactResult, CI.getType());
}
}
break;
}
// (fptrunc (fneg x)) -> (fneg (fptrunc x))

12
test/Transforms/InstCombine/fpcast.ll
View File

@ -73,3 +73,15 @@ define float @test7(double %V) {
; CHECK-NEXT: %[[trunc:.*]] = fptrunc double %frem to float
; CHECK-NEXT: ret float %trunc
}
define float @test8(float %V) {
%fext = fpext float %V to double
%frem = frem double %fext, 1.000000e-01
%trunc = fptrunc double %frem to float
ret float %trunc
; CHECK-LABEL: @test8
; CHECK-NEXT: %[[fext:.*]] = fpext float %V to double
; CHECK-NEXT: %[[frem:.*]] = frem double %fext, 1.000000e-01
; CHECK-NEXT: %[[trunc:.*]] = fptrunc double %frem to float
; CHECK-NEXT: ret float %trunc
}