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[SimplifyLibCalls] Restore the old behaviour, emit a libcall.

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Hal pointed out that the semantic of our intrinsic and the libc
call are slightly different. Add a comment while I'm here to
explain why we can't emit an intrinsic. Thanks Hal!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@278200 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Davide Italiano 2016-08-10 06:33:32 +00:00
parent 74dacfe33e
commit 1ea5b393e5
2 changed files with 6 additions and 4 deletions
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8
lib/Transforms/Utils/SimplifyLibCalls.cpp
View File

@ -1052,9 +1052,11 @@ Value *LibCallSimplifier::optimizePow(CallInst *CI, IRBuilder<> &B) {
if (CI->hasUnsafeAlgebra()) {
IRBuilder<>::FastMathFlagGuard Guard(B);
B.setFastMathFlags(CI->getFastMathFlags());
Value *Sqrt = Intrinsic::getDeclaration(CI->getModule(), Intrinsic::sqrt,
Op1->getType());
return B.CreateCall(Sqrt, Op1, "sqrt");
// Unlike other math intrinsics, sqrt has differerent semantics
// from the libc function. See LangRef for details.
return emitUnaryFloatFnCall(Op1, TLI->getName(LibFunc::sqrt), B,
Callee->getAttributes());
}
// Expand pow(x, 0.5) to (x == -infinity ? +infinity : fabs(sqrt(x))).

2
test/Transforms/InstCombine/pow-sqrt.ll
View File

@ -6,7 +6,7 @@ define double @pow_half(double %x) {
}
; CHECK-LABEL: define double @pow_half(
; CHECK-NEXT: %sqrt = call fast double @llvm.sqrt.f64(double %x)
; CHECK-NEXT: %sqrt = call fast double @sqrt(double %x)
; CHECK-NEXT: ret double %sqrt
declare double @llvm.pow.f64(double, double)