[llvm-branch-commits] [llvm] InstCombine: Consider not-inf/nan context when simplifying fmul (PR #174024)
Matt Arsenault via llvm-branch-commits
llvm-branch-commits at lists.llvm.org
Mon Jan 5 02:04:56 PST 2026
https://github.com/arsenm updated https://github.com/llvm/llvm-project/pull/174024
>From 5c39e3c567994d1f41bd04bd284b28f6a8df24e7 Mon Sep 17 00:00:00 2001
From: Matt Arsenault <Matthew.Arsenault at amd.com>
Date: Tue, 30 Dec 2025 21:04:37 +0100
Subject: [PATCH] InstCombine: Consider not-inf/nan context when simplifying
fmul
Consider if the result can be nan, or if the inputs cannot
be infinity from the flag when trying to simplify fmul into
copysign.
---
.../InstCombineSimplifyDemanded.cpp | 18 +++++++----
.../simplify-demanded-fpclass-fmul.ll | 30 +++++++++++--------
2 files changed, 30 insertions(+), 18 deletions(-)
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
index 8fd8425664bb7..10a9c98a73147 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
@@ -2165,12 +2165,18 @@ Value *InstCombinerImpl::SimplifyDemandedUseFPClass(Value *V,
KnownRHS.knownNot(fcNan);
}
+ if (FMF.noInfs()) {
+ // Flag implies inputs cannot be infinity.
+ KnownLHS.knownNot(fcInf);
+ KnownRHS.knownNot(fcInf);
+ }
+
+ bool NonNanResult = (DemandedMask & fcNan) == fcNone;
+
// With no-nans/no-infs:
// X * 0.0 --> copysign(0.0, X)
// X * -0.0 --> copysign(0.0, -X)
-
- // TODO: Apply knowledge of no-infinity returns to sources.
- if (KnownLHS.isKnownNeverInfOrNaN() &&
+ if ((NonNanResult || KnownLHS.isKnownNeverInfOrNaN()) &&
KnownRHS.isKnownAlways(fcPosZero | fcNan)) {
// => copysign(+0, lhs)
// Note: Dropping canonicalize
@@ -2180,7 +2186,7 @@ Value *InstCombinerImpl::SimplifyDemandedUseFPClass(Value *V,
}
if (KnownLHS.isKnownAlways(fcPosZero | fcNan) &&
- KnownRHS.isKnownNeverInfOrNaN()) {
+ (NonNanResult || KnownRHS.isKnownNeverInfOrNaN())) {
// => copysign(+0, rhs)
// Note: Dropping canonicalize
Value *Copysign = Builder.CreateCopySign(X, Y, FMF);
@@ -2188,7 +2194,7 @@ Value *InstCombinerImpl::SimplifyDemandedUseFPClass(Value *V,
return Copysign;
}
- if (KnownLHS.isKnownNeverInfOrNaN() &&
+ if ((NonNanResult || KnownLHS.isKnownNeverInfOrNaN()) &&
KnownRHS.isKnownAlways(fcNegZero | fcNan)) {
// => copysign(0, fneg(lhs))
// Note: Dropping canonicalize
@@ -2199,7 +2205,7 @@ Value *InstCombinerImpl::SimplifyDemandedUseFPClass(Value *V,
}
if (KnownLHS.isKnownAlways(fcNegZero | fcNan) &&
- KnownRHS.isKnownNeverInfOrNaN()) {
+ (NonNanResult || KnownRHS.isKnownNeverInfOrNaN())) {
// => copysign(+0, fneg(rhs))
// Note: Dropping canonicalize
Value *Copysign =
diff --git a/llvm/test/Transforms/InstCombine/simplify-demanded-fpclass-fmul.ll b/llvm/test/Transforms/InstCombine/simplify-demanded-fpclass-fmul.ll
index 9e7d11a902362..a5017ec383b51 100644
--- a/llvm/test/Transforms/InstCombine/simplify-demanded-fpclass-fmul.ll
+++ b/llvm/test/Transforms/InstCombine/simplify-demanded-fpclass-fmul.ll
@@ -688,7 +688,7 @@ define nofpclass(nan) float @ret_no_nan_result__known_negative_non0__fmul__known
define nofpclass(inf nan) float @ret_noinf_nonan__known_pzero_or_nan__fmul__not_inf_or_nan(float nofpclass(inf sub norm nzero) %pzero.or.nan, float %unknown) {
; CHECK-LABEL: define nofpclass(nan inf) float @ret_noinf_nonan__known_pzero_or_nan__fmul__not_inf_or_nan(
; CHECK-SAME: float nofpclass(inf nzero sub norm) [[PZERO_OR_NAN:%.*]], float [[UNKNOWN:%.*]]) {
-; CHECK-NEXT: [[MUL:%.*]] = fmul float [[UNKNOWN]], 0.000000e+00
+; CHECK-NEXT: [[MUL:%.*]] = call float @llvm.copysign.f32(float 0.000000e+00, float [[UNKNOWN]])
; CHECK-NEXT: ret float [[MUL]]
;
%mul = fmul float %pzero.or.nan, %unknown
@@ -699,7 +699,7 @@ define nofpclass(inf nan) float @ret_noinf_nonan__known_pzero_or_nan__fmul__not_
define nofpclass(inf nan) float @ret_noinf_nonan__not_inf_or_nan__fmul__known_pzero_or_nan(float nofpclass(inf sub norm nzero) %pzero.or.nan, float %unknown) {
; CHECK-LABEL: define nofpclass(nan inf) float @ret_noinf_nonan__not_inf_or_nan__fmul__known_pzero_or_nan(
; CHECK-SAME: float nofpclass(inf nzero sub norm) [[PZERO_OR_NAN:%.*]], float [[UNKNOWN:%.*]]) {
-; CHECK-NEXT: [[MUL:%.*]] = fmul float [[UNKNOWN]], 0.000000e+00
+; CHECK-NEXT: [[MUL:%.*]] = call float @llvm.copysign.f32(float 0.000000e+00, float [[UNKNOWN]])
; CHECK-NEXT: ret float [[MUL]]
;
%mul = fmul float %pzero.or.nan, %unknown
@@ -948,7 +948,7 @@ define nofpclass(nan) float @ret_no_nan__fmul_pzero__unknown(float %unknown) {
; CHECK-LABEL: define nofpclass(nan) float @ret_no_nan__fmul_pzero__unknown(
; CHECK-SAME: float [[UNKNOWN:%.*]]) {
; CHECK-NEXT: [[PZERO:%.*]] = call float @returns_pzero()
-; CHECK-NEXT: [[FMUL:%.*]] = fmul float [[UNKNOWN]], 0.000000e+00
+; CHECK-NEXT: [[FMUL:%.*]] = call float @llvm.copysign.f32(float 0.000000e+00, float [[UNKNOWN]])
; CHECK-NEXT: ret float [[FMUL]]
;
%pzero = call float @returns_pzero()
@@ -960,7 +960,7 @@ define nofpclass(nan) float @ret_no_nan__fmul_unknown__pzero(float %unknown) {
; CHECK-LABEL: define nofpclass(nan) float @ret_no_nan__fmul_unknown__pzero(
; CHECK-SAME: float [[UNKNOWN:%.*]]) {
; CHECK-NEXT: [[PZERO:%.*]] = call float @returns_pzero()
-; CHECK-NEXT: [[FMUL:%.*]] = fmul float [[UNKNOWN]], 0.000000e+00
+; CHECK-NEXT: [[FMUL:%.*]] = call float @llvm.copysign.f32(float 0.000000e+00, float [[UNKNOWN]])
; CHECK-NEXT: ret float [[FMUL]]
;
%pzero = call float @returns_pzero()
@@ -972,7 +972,8 @@ define nofpclass(nan) float @ret_no_nan__fmul_nzero__unknown(float %unknown) {
; CHECK-LABEL: define nofpclass(nan) float @ret_no_nan__fmul_nzero__unknown(
; CHECK-SAME: float [[UNKNOWN:%.*]]) {
; CHECK-NEXT: [[NZERO:%.*]] = call float @returns_nzero()
-; CHECK-NEXT: [[FMUL:%.*]] = fmul float [[UNKNOWN]], -0.000000e+00
+; CHECK-NEXT: [[TMP1:%.*]] = fneg float [[UNKNOWN]]
+; CHECK-NEXT: [[FMUL:%.*]] = call float @llvm.copysign.f32(float 0.000000e+00, float [[TMP1]])
; CHECK-NEXT: ret float [[FMUL]]
;
%nzero = call float @returns_nzero()
@@ -984,7 +985,8 @@ define nofpclass(nan) float @ret_no_nan__fmul_unknown__nzero(float %unknown) {
; CHECK-LABEL: define nofpclass(nan) float @ret_no_nan__fmul_unknown__nzero(
; CHECK-SAME: float [[UNKNOWN:%.*]]) {
; CHECK-NEXT: [[NZERO:%.*]] = call float @returns_nzero()
-; CHECK-NEXT: [[FMUL:%.*]] = fmul float [[UNKNOWN]], -0.000000e+00
+; CHECK-NEXT: [[TMP1:%.*]] = fneg float [[UNKNOWN]]
+; CHECK-NEXT: [[FMUL:%.*]] = call float @llvm.copysign.f32(float 0.000000e+00, float [[TMP1]])
; CHECK-NEXT: ret float [[FMUL]]
;
%nzero = call float @returns_nzero()
@@ -1110,7 +1112,8 @@ define nofpclass(inf) float @ret_noinf__not_inf_or_nan__fmul__nzero_or_nan(float
define nofpclass(nan) float @ret_nonan__nzero_or_nan__fmul__not_inf_or_nan(float nofpclass(inf sub norm pzero) %nzero.or.nan, float nofpclass(nan) %not.nan) {
; CHECK-LABEL: define nofpclass(nan) float @ret_nonan__nzero_or_nan__fmul__not_inf_or_nan(
; CHECK-SAME: float nofpclass(inf pzero sub norm) [[NZERO_OR_NAN:%.*]], float nofpclass(nan) [[NOT_NAN:%.*]]) {
-; CHECK-NEXT: [[MUL:%.*]] = fmul float [[NOT_NAN]], -0.000000e+00
+; CHECK-NEXT: [[TMP1:%.*]] = fneg float [[NOT_NAN]]
+; CHECK-NEXT: [[MUL:%.*]] = call float @llvm.copysign.f32(float 0.000000e+00, float [[TMP1]])
; CHECK-NEXT: ret float [[MUL]]
;
%mul = fmul float %nzero.or.nan, %not.nan
@@ -1121,7 +1124,8 @@ define nofpclass(nan) float @ret_nonan__nzero_or_nan__fmul__not_inf_or_nan(float
define nofpclass(nan) float @ret_nonan__not_inf_or_nan__fmul__nzero_or_nan(float nofpclass(nan) %not.nan, float nofpclass(inf sub norm pzero) %nzero.or.nan) {
; CHECK-LABEL: define nofpclass(nan) float @ret_nonan__not_inf_or_nan__fmul__nzero_or_nan(
; CHECK-SAME: float nofpclass(nan) [[NOT_NAN:%.*]], float nofpclass(inf pzero sub norm) [[NZERO_OR_NAN:%.*]]) {
-; CHECK-NEXT: [[MUL:%.*]] = fmul float [[NOT_NAN]], -0.000000e+00
+; CHECK-NEXT: [[TMP1:%.*]] = fneg float [[NOT_NAN]]
+; CHECK-NEXT: [[MUL:%.*]] = call float @llvm.copysign.f32(float 0.000000e+00, float [[TMP1]])
; CHECK-NEXT: ret float [[MUL]]
;
%mul = fmul float %not.nan, %nzero.or.nan
@@ -1132,7 +1136,8 @@ define nofpclass(nan) float @ret_nonan__not_inf_or_nan__fmul__nzero_or_nan(float
define nofpclass(snan) float @ret__nzero_or_nan__fmul_ninf__not_inf_or_nan(float nofpclass(inf sub norm pzero) %nzero.or.nan, float nofpclass(nan) %not.nan) {
; CHECK-LABEL: define nofpclass(snan) float @ret__nzero_or_nan__fmul_ninf__not_inf_or_nan(
; CHECK-SAME: float nofpclass(inf pzero sub norm) [[NZERO_OR_NAN:%.*]], float nofpclass(nan) [[NOT_NAN:%.*]]) {
-; CHECK-NEXT: [[MUL:%.*]] = fmul ninf float [[NZERO_OR_NAN]], [[NOT_NAN]]
+; CHECK-NEXT: [[TMP1:%.*]] = fneg ninf float [[NOT_NAN]]
+; CHECK-NEXT: [[MUL:%.*]] = call ninf float @llvm.copysign.f32(float [[NZERO_OR_NAN]], float [[TMP1]])
; CHECK-NEXT: ret float [[MUL]]
;
%mul = fmul ninf float %nzero.or.nan, %not.nan
@@ -1143,7 +1148,8 @@ define nofpclass(snan) float @ret__nzero_or_nan__fmul_ninf__not_inf_or_nan(float
define nofpclass(snan) float @ret_not_inf_or_nan__fmul_ninf__nzero_or_nan(float nofpclass(nan) %not.nan, float nofpclass(inf sub norm pzero) %nzero.or.nan) {
; CHECK-LABEL: define nofpclass(snan) float @ret_not_inf_or_nan__fmul_ninf__nzero_or_nan(
; CHECK-SAME: float nofpclass(nan) [[NOT_NAN:%.*]], float nofpclass(inf pzero sub norm) [[NZERO_OR_NAN:%.*]]) {
-; CHECK-NEXT: [[MUL:%.*]] = fmul ninf float [[NOT_NAN]], [[NZERO_OR_NAN]]
+; CHECK-NEXT: [[TMP1:%.*]] = fneg ninf float [[NOT_NAN]]
+; CHECK-NEXT: [[MUL:%.*]] = call ninf float @llvm.copysign.f32(float [[NZERO_OR_NAN]], float [[TMP1]])
; CHECK-NEXT: ret float [[MUL]]
;
%mul = fmul ninf float %not.nan, %nzero.or.nan
@@ -1266,7 +1272,7 @@ define nofpclass(inf) float @ret_noinf__not_inf_or_nan__fmul__pzero_or_nan(float
define nofpclass(snan) float @ret__pzero_or_nan__fmul_ninf__not_inf_or_nan(float nofpclass(inf sub norm nzero) %pzero.or.nan, float nofpclass(nan) %not.nan) {
; CHECK-LABEL: define nofpclass(snan) float @ret__pzero_or_nan__fmul_ninf__not_inf_or_nan(
; CHECK-SAME: float nofpclass(inf nzero sub norm) [[PZERO_OR_NAN:%.*]], float nofpclass(nan) [[NOT_NAN:%.*]]) {
-; CHECK-NEXT: [[MUL:%.*]] = fmul ninf float [[PZERO_OR_NAN]], [[NOT_NAN]]
+; CHECK-NEXT: [[MUL:%.*]] = call ninf float @llvm.copysign.f32(float [[PZERO_OR_NAN]], float [[NOT_NAN]])
; CHECK-NEXT: ret float [[MUL]]
;
%mul = fmul ninf float %pzero.or.nan, %not.nan
@@ -1277,7 +1283,7 @@ define nofpclass(snan) float @ret__pzero_or_nan__fmul_ninf__not_inf_or_nan(float
define nofpclass(snan) float @ret_not_inf_or_nan__fmul_ninf__pzero_or_nan(float nofpclass(nan) %not.nan, float nofpclass(inf sub norm nzero) %pzero.or.nan) {
; CHECK-LABEL: define nofpclass(snan) float @ret_not_inf_or_nan__fmul_ninf__pzero_or_nan(
; CHECK-SAME: float nofpclass(nan) [[NOT_NAN:%.*]], float nofpclass(inf nzero sub norm) [[PZERO_OR_NAN:%.*]]) {
-; CHECK-NEXT: [[MUL:%.*]] = fmul ninf float [[NOT_NAN]], [[PZERO_OR_NAN]]
+; CHECK-NEXT: [[MUL:%.*]] = call ninf float @llvm.copysign.f32(float [[PZERO_OR_NAN]], float [[NOT_NAN]])
; CHECK-NEXT: ret float [[MUL]]
;
%mul = fmul ninf float %not.nan, %pzero.or.nan
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