[InstSimplify] Handle nsz when simplifying X * 0.0 #142181
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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
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@llvm/pr-subscribers-llvm-transforms Author: None (Nadharm) ChangesIf ValueTracking can guarantee non-NaN and non-INF and the https://alive2.llvm.org/ce/z/XacRQZ Full diff: https://github.com/llvm/llvm-project/pull/142181.diff 2 Files Affected:
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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@llvm/pr-subscribers-llvm-analysis Author: None (Nadharm) ChangesIf ValueTracking can guarantee non-NaN and non-INF and the https://alive2.llvm.org/ce/z/XacRQZ Full diff: https://github.com/llvm/llvm-project/pull/142181.diff 2 Files Affected:
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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@Nadharm Congratulations on having your first Pull Request (PR) merged into the LLVM Project! Your changes will be combined with recent changes from other authors, then tested by our build bots. If there is a problem with a build, you may receive a report in an email or a comment on this PR. Please check whether problems have been caused by your change specifically, as the builds can include changes from many authors. It is not uncommon for your change to be included in a build that fails due to someone else's changes, or infrastructure issues. How to do this, and the rest of the post-merge process, is covered in detail here. If your change does cause a problem, it may be reverted, or you can revert it yourself. This is a normal part of LLVM development. You can fix your changes and open a new PR to merge them again. If you don't get any reports, no action is required from you. Your changes are working as expected, well done! |
If ValueTracking can guarantee non-NaN and non-INF and the
nszfast-math flag is set, we can simplify X * 0.0 ==> 0.0.https://alive2.llvm.org/ce/z/XacRQZ