diff --git a/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp index cc6a3015408..9c310f04dcd 100644 --- a/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp +++ b/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp @@ -374,9 +374,12 @@ Value *InstCombiner::foldFMulConst(Instruction *FMulOrDiv, ConstantFP *C, } else { if (C0) { // (C0 / X) * C => (C0 * C) / X - ConstantFP *F = cast(ConstantExpr::getFMul(C0, C)); - if (isNormalFp(F)) - R = BinaryOperator::CreateFDiv(F, Opnd1); + if (FMulOrDiv->hasOneUse()) { + // It would otherwise introduce another div. + ConstantFP *F = cast(ConstantExpr::getFMul(C0, C)); + if (isNormalFp(F)) + R = BinaryOperator::CreateFDiv(F, Opnd1); + } } else { // (X / C1) * C => X * (C/C1) if C/C1 is not a denormal ConstantFP *F = cast(ConstantExpr::getFDiv(C, C1)); diff --git a/test/Transforms/InstCombine/fast-math.ll b/test/Transforms/InstCombine/fast-math.ll index a9a7015f62d..d8ba2a59ff5 100644 --- a/test/Transforms/InstCombine/fast-math.ll +++ b/test/Transforms/InstCombine/fast-math.ll @@ -202,6 +202,18 @@ define float @fmul2(float %f1) { ; CHECK: fdiv fast float 1.200000e+07, %f1 } +; X/C1 * C2 => X * (C2/C1) is disabled if X/C1 has multiple uses +@fmul2_external = external global float +define float @fmul2_disable(float %f1) { + %div = fdiv fast float 1.000000e+00, %f1 + store float %div, float* @fmul2_external + %mul = fmul fast float %div, 2.000000e+00 + ret float %mul +; CHECK-LABEL: @fmul2_disable +; CHECK: store +; CHECK: fmul fast +} + ; X/C1 * C2 => X * (C2/C1) (if C2/C1 is normal Fp) define float @fmul3(float %f1, float %f2) { %t1 = fdiv float %f1, 2.0e+3