[llvm-branch-commits] [llvm] ValueTracking: Improve handling for fma/fmuladd (PR #175614)

[Yingwei Zheng via llvm-branch-commits]

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@@ -332,6 +332,19 @@ KnownFPClass KnownFPClass::fmul(const KnownFPClass &KnownLHS,
   return Known;
 }
 
+KnownFPClass KnownFPClass::fma(const KnownFPClass &KnownLHS,
+                               const KnownFPClass &KnownRHS,
+                               const KnownFPClass &KnownAddend,
+                               DenormalMode Mode) {
+  return fadd(fmul(KnownLHS, KnownRHS, Mode), KnownAddend, Mode);
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dtcxzyw wrote:

Does it really work for fused-mul-add? I cannot prove/disprove this. I'd suggest passing DenormalMode::Dynamic() to fmul/square since fma doesn't round the intermediate result (I assume FTZ/DAZ don't apply either).

https://github.com/llvm/llvm-project/pull/175614