[llvm] [SelectionDAG] Remove UnsafeFPMath check in `visitFADDForFMACombine` (PR #127770)

[via llvm-commits]

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@@ -17855,11 +17856,17 @@ template <class MatchContextClass> SDValue DAGCombiner::visitFMA(SDNode *N) {
   }
 
   // FIXME: use fast math flags instead of Options.UnsafeFPMath
-  if (Options.UnsafeFPMath) {
-    if (N0CFP && N0CFP->isZero())
-      return N2;
-    if (N1CFP && N1CFP->isZero())
-      return N2;
+  // TODO: Finally migrate away from global TargetOptions.
+  if (Options.AllowFPOpFusion == FPOpFusion::Fast ||
+      (Options.NoNaNsFPMath && Options.NoInfsFPMath) ||
+      (N->getFlags().hasNoNaNs() && N->getFlags().hasNoInfs())) {
+    if (Options.NoSignedZerosFPMath || N->getFlags().hasNoSignedZeros() ||
+        (N2CFP && !N2CFP->isExactlyValue(-0.0))) {
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paperchalice wrote:

Add a simple test for X86
Finally we should merge it into `SelectionDAG::foldConstantFPMath` when it support unary and ternary operators.

https://github.com/llvm/llvm-project/pull/127770