diff --git a/llvm/lib/Transforms/Scalar/GVN.cpp b/llvm/lib/Transforms/Scalar/GVN.cpp index 29ea432e4a4c3..7519b598659f1 100644 --- a/llvm/lib/Transforms/Scalar/GVN.cpp +++ b/llvm/lib/Transforms/Scalar/GVN.cpp @@ -2182,9 +2182,16 @@ bool GVN::propagateEquality(Value *LHS, Value *RHS, // Handle the floating point versions of equality comparisons too. if ((isKnownTrue && Cmp->getPredicate() == CmpInst::FCMP_OEQ) || - (isKnownFalse && Cmp->getPredicate() == CmpInst::FCMP_UNE)) - Worklist.push_back(std::make_pair(Op0, Op1)); - + (isKnownFalse && Cmp->getPredicate() == CmpInst::FCMP_UNE)) { + // Floating point -0.0 and 0.0 compare equal, so we can't + // propagate a constant based on that comparison. + // FIXME: We should do this optimization if 'no signed zeros' is + // applicable via an instruction-level fast-math-flag or some other + // indicator that relaxed FP semantics are being used. + if (!isa(Op1) || !cast(Op1)->isZero()) + Worklist.push_back(std::make_pair(Op0, Op1)); + } + // If "A >= B" is known true, replace "A < B" with false everywhere. CmpInst::Predicate NotPred = Cmp->getInversePredicate(); Constant *NotVal = ConstantInt::get(Cmp->getType(), isKnownFalse); diff --git a/llvm/test/Transforms/GVN/edge.ll b/llvm/test/Transforms/GVN/edge.ll index 1dc285ec3d7cc..f28a76bb42d6c 100644 --- a/llvm/test/Transforms/GVN/edge.ll +++ b/llvm/test/Transforms/GVN/edge.ll @@ -69,11 +69,11 @@ if: br label %return return: - %retval.0 = phi double [ %div, %if ], [ %x, %entry ] - ret double %retval.0 + %retval = phi double [ %div, %if ], [ %x, %entry ] + ret double %retval ; CHECK-LABEL: define double @fcmp_oeq( -; CHECK: %div = fdiv double %x, 2.000000e+00 +; CHECK: %div = fdiv double %x, 2.0 } define double @fcmp_une(double %x, double %y) { @@ -86,10 +86,46 @@ else: br label %return return: - %retval.0 = phi double [ %div, %else ], [ %x, %entry ] - ret double %retval.0 + %retval = phi double [ %div, %else ], [ %x, %entry ] + ret double %retval ; CHECK-LABEL: define double @fcmp_une( -; CHECK: %div = fdiv double %x, 2.000000e+00 +; CHECK: %div = fdiv double %x, 2.0 } +; PR22376 - We can't propagate zero constants because -0.0 +; compares equal to 0.0. If %y is -0.0 in this test case, +; we would produce the wrong sign on the infinity return value. +define double @fcmp_oeq_zero(double %x, double %y) { +entry: + %cmp = fcmp oeq double %y, 0.0 + br i1 %cmp, label %if, label %return + +if: + %div = fdiv double %x, %y + br label %return + +return: + %retval = phi double [ %div, %if ], [ %x, %entry ] + ret double %retval + +; CHECK-LABEL: define double @fcmp_oeq_zero( +; CHECK: %div = fdiv double %x, %y +} + +define double @fcmp_une_zero(double %x, double %y) { +entry: + %cmp = fcmp une double %y, -0.0 + br i1 %cmp, label %return, label %else + +else: + %div = fdiv double %x, %y + br label %return + +return: + %retval = phi double [ %div, %else ], [ %x, %entry ] + ret double %retval + +; CHECK-LABEL: define double @fcmp_une_zero( +; CHECK: %div = fdiv double %x, %y +}