[SelectionDAG] Fix NaN regression in fma dag-combine. #146592
Merged
+13
−2
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
After 901e139 (llvm#127770), the DAG combine would transform `fma(x, 0.0, 1.0)` into `1.0` if `-fp-contract=fast` was enabled, in addition to when 'x' is marked nnan/ninf. It's only valid in the latter case, not the former, so delete the extra condition.
|
@llvm/pr-subscribers-llvm-selectiondag @llvm/pr-subscribers-backend-x86 Author: James Y Knight (jyknight) ChangesAfter 901e139 (#127770), the DAG combine would transform It's only valid in the latter case, not the former, so delete the extra condition. Full diff: https://github.com/llvm/llvm-project/pull/146592.diff 2 Files Affected:
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index c43677f8b925c..bfc061b404560 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -18087,8 +18087,7 @@ template <class MatchContextClass> SDValue DAGCombiner::visitFMA(SDNode *N) {
// FIXME: use fast math flags instead of Options.UnsafeFPMath
// TODO: Finally migrate away from global TargetOptions.
- if (Options.AllowFPOpFusion == FPOpFusion::Fast ||
- (Options.NoNaNsFPMath && Options.NoInfsFPMath) ||
+ if ((Options.NoNaNsFPMath && Options.NoInfsFPMath) ||
(N->getFlags().hasNoNaNs() && N->getFlags().hasNoInfs())) {
if (Options.NoSignedZerosFPMath || N->getFlags().hasNoSignedZeros() ||
(N2CFP && !N2CFP->isExactlyValue(-0.0))) {
diff --git a/llvm/test/CodeGen/X86/dag-combiner-fma-folding.ll b/llvm/test/CodeGen/X86/dag-combiner-fma-folding.ll
index 2bd7dc445a02b..6291100f42c3d 100644
--- a/llvm/test/CodeGen/X86/dag-combiner-fma-folding.ll
+++ b/llvm/test/CodeGen/X86/dag-combiner-fma-folding.ll
@@ -1,5 +1,6 @@
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
; RUN: llc -mtriple=x86_64-- --start-before=x86-isel -mattr=+avx,+fma %s -o - | FileCheck %s
+; RUN: llc -mtriple=x86_64-- --start-before=x86-isel -mattr=+avx,+fma %s -o - -fp-contract=fast | FileCheck %s
define double @fma_folding(double %x) {
; CHECK-LABEL: fma_folding:
@@ -20,3 +21,14 @@ define double @fma_no_folding(double %x) {
%fused = call contract nnan ninf double @llvm.fma.f64(double %x, double 0.0, double -0.0)
ret double %fused
}
+
+define double @fma_no_fold_potential_nan(double %x) {
+; CHECK-LABEL: fma_no_fold_potential_nan:
+; CHECK: # %bb.0:
+; CHECK-NEXT: vxorpd %xmm1, %xmm1, %xmm1
+; CHECK-NEXT: vfmadd213sd {{.*#+}} xmm0 = (xmm1 * xmm0) + mem
+; CHECK-NEXT: retq
+ %fused = call contract double @llvm.fma.f64(double %x, double 0.0, double 1.0)
+ ret double %fused
+}
+
|
|
I have verified and it fixes the bug in jax-ml/jax#4780 |
|
we are also blocked on it internally. So would appreciate if we can get a quick a review here sooner. |
I mean...do you want to review the change? |
|
LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/153/builds/36665 Here is the relevant piece of the build log for the reference |
arsenm
reviewed
Jul 2, 2025
| ; CHECK-NEXT: vxorpd %xmm1, %xmm1, %xmm1 | ||
| ; CHECK-NEXT: vfmadd213sd {{.*#+}} xmm0 = (xmm1 * xmm0) + mem | ||
| ; CHECK-NEXT: retq | ||
| %fused = call contract double @llvm.fma.f64(double %x, double 0.0, double 1.0) |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
After 901e139 (#127770), the DAG combine would transform
fma(x, 0.0, 1.0)into1.0if-fp-contract=fastwas enabled, in addition to when 'x' is marked nnan/ninf.It's only valid in the latter case, not the former, so delete the extra condition.