[llvm] [LV] Vectorize maxnum/minnum w/o fast-math flags. (PR #148239)

[Florian Hahn via llvm-commits]

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@@ -941,10 +941,27 @@ RecurrenceDescriptor::InstDesc RecurrenceDescriptor::isRecurrenceInstr(
                   m_Intrinsic<Intrinsic::minimumnum>(m_Value(), m_Value())) ||
             match(I, m_Intrinsic<Intrinsic::maximumnum>(m_Value(), m_Value()));
     };
-    if (isIntMinMaxRecurrenceKind(Kind) ||
-        (HasRequiredFMF() && isFPMinMaxRecurrenceKind(Kind)))
+    if (isIntMinMaxRecurrenceKind(Kind))
       return isMinMaxPattern(I, Kind, Prev);
-    else if (isFMulAddIntrinsic(I))
+    if (isFPMinMaxRecurrenceKind(Kind)) {
+      if (HasRequiredFMF())
+        return isMinMaxPattern(I, Kind, Prev);
+      // We may be able to vectorize FMax/FMin reductions using maxnum/minnum
+      // intrinsics with extra checks ensuring the inputs are not NaN.
+      auto *StartV = dyn_cast<ConstantFP>(
+          OrigPhi->getIncomingValueForBlock(L->getLoopPredecessor()));
+      if (StartV && !StartV->getValue().isNaN() &&
+          isMinMaxPattern(I, Kind, Prev).isRecurrence()) {
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fhahn wrote:

Simplified some checks and updated to use early exit, thanks!

https://github.com/llvm/llvm-project/pull/148239