[llvm] f71e4e9 - [InstSimplify] Handle nsz when simplifying X * 0.0 (#142181)
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Fri May 30 22:50:25 PDT 2025
Author: Nadharm
Date: 2025-05-31T13:50:22+08:00
New Revision: f71e4e9bc2b6cd1444ab2a395a1ce20d486362de
URL: https://github.com/llvm/llvm-project/commit/f71e4e9bc2b6cd1444ab2a395a1ce20d486362de
DIFF: https://github.com/llvm/llvm-project/commit/f71e4e9bc2b6cd1444ab2a395a1ce20d486362de.diff
LOG: [InstSimplify] Handle nsz when simplifying X * 0.0 (#142181)
If ValueTracking can guarantee non-NaN and non-INF and the `nsz`
fast-math flag is set, we can simplify X * 0.0 ==> 0.0.
https://alive2.llvm.org/ce/z/XacRQZ
Added:
Modified:
llvm/lib/Analysis/InstructionSimplify.cpp
llvm/test/Transforms/InstSimplify/floating-point-arithmetic.ll
Removed:
################################################################################
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 23e147ba8c6a1..12c84c718d4fd 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -5844,6 +5844,9 @@ static Value *simplifyFMAFMul(Value *Op0, Value *Op1, FastMathFlags FMF,
KnownFPClass Known =
computeKnownFPClass(Op0, FMF, fcInf | fcNan, /*Depth=*/0, Q);
if (Known.isKnownNever(fcInf | fcNan)) {
+ // if nsz is set, return 0.0
+ if (FMF.noSignedZeros())
+ return ConstantFP::getZero(Op0->getType());
// +normal number * (-)0.0 --> (-)0.0
if (Known.SignBit == false)
return Op1;
diff --git a/llvm/test/Transforms/InstSimplify/floating-point-arithmetic.ll b/llvm/test/Transforms/InstSimplify/floating-point-arithmetic.ll
index d3178a103d42c..ab4448b460bfc 100644
--- a/llvm/test/Transforms/InstSimplify/floating-point-arithmetic.ll
+++ b/llvm/test/Transforms/InstSimplify/floating-point-arithmetic.ll
@@ -211,6 +211,22 @@ define double @fmul_nnan_ninf_nneg_n0.0_commute(i127 %x) {
ret double %r
}
+define float @fmul_ninf_nnan_mul_zero_nsz(float nofpclass(inf nan) %f) {
+; CHECK-LABEL: @fmul_ninf_nnan_mul_zero_nsz(
+; CHECK-NEXT: ret float 0.000000e+00
+;
+ %r = fmul nsz float %f, 0.0
+ ret float %r
+}
+
+define float @fmul_ninf_nnan_mul_nzero_nsz(float nofpclass(inf nan) %f) {
+; CHECK-LABEL: @fmul_ninf_nnan_mul_nzero_nsz(
+; CHECK-NEXT: ret float 0.000000e+00
+;
+ %r = fmul nsz float %f, -0.0
+ ret float %r
+}
+
define float @src_mul_nzero_neg(float nofpclass(inf nan pzero psub pnorm) %f) {
; CHECK-LABEL: @src_mul_nzero_neg(
; CHECK-NEXT: ret float 0.000000e+00
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