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InstCombine: Add a couple of fabs identities for comparing with 0.0.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@162174 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Benjamin Kramer
2012-08-18 20:06:47 +00:00
parent 2b74957106
commit 00abcd3da0
2 changed files with 121 additions and 0 deletions
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39
lib/Transforms/InstCombine/InstCombineCompares.cpp
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@ -17,6 +17,7 @@
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/MemoryBuiltins.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Target/TargetLibraryInfo.h"
#include "llvm/Support/ConstantRange.h"
#include "llvm/Support/GetElementPtrTypeIterator.h"
#include "llvm/Support/PatternMatch.h"
@ -2985,6 +2986,44 @@ Instruction *InstCombiner::visitFCmpInst(FCmpInst &I) {
return Res;
}
break;
case Instruction::Call: {
CallInst *CI = cast<CallInst>(LHSI);
LibFunc::Func Func;
// Various optimization for fabs compared with zero.
if (RHSC->isNullValue() && CI->hasOneUse() &&
TLI->getLibFunc(CI->getCalledFunction()->getName(), Func) &&
TLI->has(Func)) {
if (Func == LibFunc::fabs || Func == LibFunc::fabsf ||
Func == LibFunc::fabsl) {
switch (I.getPredicate()) {
default: break;
// fabs(x) < 0 --> false
case FCmpInst::FCMP_OLT:
return ReplaceInstUsesWith(I, Builder->getFalse());
// fabs(x) > 0 --> x != 0
case FCmpInst::FCMP_OGT:
return new FCmpInst(FCmpInst::FCMP_ONE, CI->getArgOperand(0),
RHSC);
// fabs(x) <= 0 --> x == 0
case FCmpInst::FCMP_OLE:
return new FCmpInst(FCmpInst::FCMP_OEQ, CI->getArgOperand(0),
RHSC);
// fabs(x) >= 0 --> !isnan(x)
case FCmpInst::FCMP_OGE:
return new FCmpInst(FCmpInst::FCMP_ORD, CI->getArgOperand(0),
RHSC);
// fabs(x) == 0 --> x == 0
// fabs(x) != 0 --> x != 0
case FCmpInst::FCMP_OEQ:
case FCmpInst::FCMP_UEQ:
case FCmpInst::FCMP_ONE:
case FCmpInst::FCMP_UNE:
return new FCmpInst(I.getPredicate(), CI->getArgOperand(0),
RHSC);
}
}
}
}
}
}