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[SimplifyLibCalls] Transform log(exp2(y)) to y*log(2) under fast-math.

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llvm-svn: 254317
This commit is contained in:
Davide Italiano 2015-11-30 19:36:35 +00:00
parent 8619fd0740
commit 0f427b7147
3 changed files with 35 additions and 1 deletions
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10
lib/Transforms/Utils/SimplifyLibCalls.cpp
View File

@ -1322,6 +1322,15 @@ Value *LibCallSimplifier::optimizeLog(CallInst *CI, IRBuilder<> &B) {
return B.CreateFMul(OpC->getArgOperand(1),
EmitUnaryFloatFnCall(OpC->getOperand(0), Callee->getName(), B,
Callee->getAttributes()), "mul");
// log(exp2(y)) -> y*log(2)
if (F && Name == "log" && TLI->getLibFunc(F->getName(), Func) &&
TLI->has(Func) && Func == LibFunc::exp2)
return B.CreateFMul(
OpC->getArgOperand(0),
EmitUnaryFloatFnCall(ConstantFP::get(CI->getType(), 2.0),
Callee->getName(), B, Callee->getAttributes()),
"logmul");
return Ret;
}
@ -2301,7 +2310,6 @@ void LibCallSimplifier::replaceAllUsesWith(Instruction *I, Value *With) {
// log, logf, logl:
// * log(exp(x)) -> x
// * log(exp(y)) -> y*log(e)
// * log(exp2(y)) -> y*log(2)
// * log(exp10(y)) -> y*log(10)
// * log(sqrt(x)) -> 0.5*log(x)
//

13
test/Transforms/InstCombine/log-pow-nofastmath.ll
View File

@ -13,5 +13,18 @@ entry:
; CHECK: ret double %call
; CHECK: }
define double @test3(double %x) #0 {
%call2 = call double @exp2(double %x) #0
%call3 = call double @log(double %call2) #0
ret double %call3
}
; CHECK-LABEL: @test3
; CHECK: %call2 = call double @exp2(double %x)
; CHECK: %call3 = call double @log(double %call2)
; CHECK: ret double %call3
; CHECK: }
declare double @log(double) #0
declare double @exp2(double)
declare double @llvm.pow.f64(double, double)

13
test/Transforms/InstCombine/log-pow.ll
View File

@ -22,7 +22,20 @@ define double @test2(double ()* %fptr, double %p1) #0 {
; CHECK-LABEL: @test2
; CHECK: log
define double @test3(double %x) #0 {
%call2 = call double @exp2(double %x) #0
%call3 = call double @log(double %call2) #0
ret double %call3
}
; CHECK-LABEL: @test3
; CHECK: %call2 = call double @exp2(double %x) #0
; CHECK: %logmul = fmul fast double %x, 0x3FE62E42FEFA39EF
; CHECK: ret double %logmul
; CHECK: }
declare double @log(double) #0
declare double @exp2(double) #0
declare double @llvm.pow.f64(double, double)
attributes #0 = { "unsafe-fp-math"="true" }