diff options
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp | 5 | ||||
| -rw-r--r-- | llvm/test/Transforms/InstCombine/fmul.ll | 29 |
2 files changed, 34 insertions, 0 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp index da5d00dd9a1..0a19a4880f2 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp @@ -531,6 +531,11 @@ Instruction *InstCombiner::visitFMul(BinaryOperator &I) { } } + // sqrt(X) * sqrt(X) -> X + if (AllowReassociate && (Op0 == Op1)) + if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Op0)) + if (II->getIntrinsicID() == Intrinsic::sqrt) + return ReplaceInstUsesWith(I, II->getOperand(0)); // Under unsafe algebra do: // X * log2(0.5*Y) = X*log2(Y) - X diff --git a/llvm/test/Transforms/InstCombine/fmul.ll b/llvm/test/Transforms/InstCombine/fmul.ll index 18cbf9da536..3c8bab9ffb5 100644 --- a/llvm/test/Transforms/InstCombine/fmul.ll +++ b/llvm/test/Transforms/InstCombine/fmul.ll @@ -123,3 +123,32 @@ define float @test11(float %x, float %y) { ; CHECK-NOT: fadd float ; CHECK: fadd fast float } + +; PR21126: http://llvm.org/bugs/show_bug.cgi?id=21126 +; With unsafe/fast math, sqrt(X) * sqrt(X) is just X. +declare double @llvm.sqrt.f64(double) + +define double @sqrt_squared1(double %f) #0 { + %sqrt = call double @llvm.sqrt.f64(double %f) + %mul = fmul fast double %sqrt, %sqrt + ret double %mul +; CHECK-LABEL: @sqrt_squared1( +; CHECK-NEXT: ret double %f +} + +; With unsafe/fast math, sqrt(X) * sqrt(X) is just X, +; but make sure another use of the sqrt is intact. +; Note that the remaining fmul is altered but is not 'fast' +; itself because it was not marked 'fast' originally. +; Thus, we have an overall fast result, but no more indication of +; 'fast'ness in the code. +define double @sqrt_squared2(double %f) #0 { + %sqrt = call double @llvm.sqrt.f64(double %f) + %mul1 = fmul fast double %sqrt, %sqrt + %mul2 = fmul double %mul1, %sqrt + ret double %mul2 +; CHECK-LABEL: @sqrt_squared2( +; CHECK-NEXT: %sqrt = call double @llvm.sqrt.f64(double %f) +; CHECK-NEXT: %mul2 = fmul double %sqrt, %f +; CHECK-NEXT: ret double %mul2 +} |
