https://github.com/arsenm updated https://github.com/llvm/llvm-project/pull/174023
>From 45afbb363c9d48aa9c552829c42e9c802c280a50 Mon Sep 17 00:00:00 2001 From: Matt Arsenault <[email protected]> Date: Tue, 30 Dec 2025 20:19:45 +0100 Subject: [PATCH] InstCombine: Handle fmul by -0 case in SimplifyDemandedFPClass The fmul visitor handles this case as copysign and fneg. --- .../InstCombineSimplifyDemanded.cpp | 22 +++++++++++++++++-- .../simplify-demanded-fpclass-fmul.ll | 6 +++-- 2 files changed, 24 insertions(+), 4 deletions(-) diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp index b76d78a4376e3..8fd8425664bb7 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp @@ -2170,8 +2170,6 @@ Value *InstCombinerImpl::SimplifyDemandedUseFPClass(Value *V, // X * -0.0 --> copysign(0.0, -X) // TODO: Apply knowledge of no-infinity returns to sources. - - // TODO: Known -0, turn into copysign(y, fneg(x)) like visitFMul. if (KnownLHS.isKnownNeverInfOrNaN() && KnownRHS.isKnownAlways(fcPosZero | fcNan)) { // => copysign(+0, lhs) @@ -2190,6 +2188,26 @@ Value *InstCombinerImpl::SimplifyDemandedUseFPClass(Value *V, return Copysign; } + if (KnownLHS.isKnownNeverInfOrNaN() && + KnownRHS.isKnownAlways(fcNegZero | fcNan)) { + // => copysign(0, fneg(lhs)) + // Note: Dropping canonicalize + Value *Copysign = + Builder.CreateCopySign(Y, Builder.CreateFNegFMF(X, FMF), FMF); + Copysign->takeName(I); + return Copysign; + } + + if (KnownLHS.isKnownAlways(fcNegZero | fcNan) && + KnownRHS.isKnownNeverInfOrNaN()) { + // => copysign(+0, fneg(rhs)) + // Note: Dropping canonicalize + Value *Copysign = + Builder.CreateCopySign(X, Builder.CreateFNegFMF(Y, FMF), FMF); + Copysign->takeName(I); + return Copysign; + } + Type *EltTy = VTy->getScalarType(); DenormalMode Mode = F.getDenormalMode(EltTy->getFltSemantics()); diff --git a/llvm/test/Transforms/InstCombine/simplify-demanded-fpclass-fmul.ll b/llvm/test/Transforms/InstCombine/simplify-demanded-fpclass-fmul.ll index 98a365b0f4ef6..9e7d11a902362 100644 --- a/llvm/test/Transforms/InstCombine/simplify-demanded-fpclass-fmul.ll +++ b/llvm/test/Transforms/InstCombine/simplify-demanded-fpclass-fmul.ll @@ -1020,7 +1020,8 @@ define nofpclass(ninf) float @ret_ninf__fmul_nnan_unknown__zero(float %unknown) define nofpclass(snan) float @known__nzero_or_nan__fmul__not_inf_or_nan(float nofpclass(inf sub norm pzero) %nzero.or.nan, float nofpclass(inf nan) %not.inf.or.nan) { ; CHECK-LABEL: define nofpclass(snan) float @known__nzero_or_nan__fmul__not_inf_or_nan( ; CHECK-SAME: float nofpclass(inf pzero sub norm) [[NZERO_OR_NAN:%.*]], float nofpclass(nan inf) [[NOT_INF_OR_NAN:%.*]]) { -; CHECK-NEXT: [[MUL:%.*]] = fmul contract float [[NZERO_OR_NAN]], [[NOT_INF_OR_NAN]] +; CHECK-NEXT: [[TMP1:%.*]] = fneg contract float [[NOT_INF_OR_NAN]] +; CHECK-NEXT: [[MUL:%.*]] = call contract float @llvm.copysign.f32(float [[NZERO_OR_NAN]], float [[TMP1]]) ; CHECK-NEXT: ret float [[MUL]] ; %mul = fmul contract float %nzero.or.nan, %not.inf.or.nan @@ -1031,7 +1032,8 @@ define nofpclass(snan) float @known__nzero_or_nan__fmul__not_inf_or_nan(float no define nofpclass(snan) float @known__not_inf_or_nan__fmul__nzero_or_nan(float nofpclass(inf nan) %not.inf.or.nan, float nofpclass(inf sub norm pzero) %nzero.or.nan) { ; CHECK-LABEL: define nofpclass(snan) float @known__not_inf_or_nan__fmul__nzero_or_nan( ; CHECK-SAME: float nofpclass(nan inf) [[NOT_INF_OR_NAN:%.*]], float nofpclass(inf pzero sub norm) [[NZERO_OR_NAN:%.*]]) { -; CHECK-NEXT: [[MUL:%.*]] = fmul contract float [[NOT_INF_OR_NAN]], [[NZERO_OR_NAN]] +; CHECK-NEXT: [[TMP1:%.*]] = fneg contract float [[NOT_INF_OR_NAN]] +; CHECK-NEXT: [[MUL:%.*]] = call contract float @llvm.copysign.f32(float [[NZERO_OR_NAN]], float [[TMP1]]) ; CHECK-NEXT: ret float [[MUL]] ; %mul = fmul contract float %not.inf.or.nan, %nzero.or.nan _______________________________________________ llvm-branch-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-branch-commits
