[llvm] [LV] Vectorize selecting last IV of min/max element. (PR #141431)

[Florian Hahn via llvm-commits]

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@@ -214,6 +214,51 @@ static bool checkOrderedReduction(RecurKind Kind, Instruction *ExactFPMathInst,
   return true;
 }
 
+/// Returns true if \p Phi is a min/max reduction matching \p Kind where \p Phi
+/// is used in the loop outside the reduction chain. This is common for
+static bool isMinMaxReductionWithLoopUsersOutsideReductionChain(
+    PHINode *Phi, RecurKind Kind, Loop *TheLoop, RecurrenceDescriptor &RedDes) {
+  BasicBlock *Latch = TheLoop->getLoopLatch();
+  if (!Latch)
+    return false;
+  assert(Phi->getNumIncomingValues() == 2 &&
+         "phi must have exactly 2 incoming values");
+  Value *Inc = Phi->getIncomingValueForBlock(Latch);
+  if (Phi->hasOneUse() ||
+      !RecurrenceDescriptor::isIntMinMaxRecurrenceKind(Kind))
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fhahn wrote:

Done thanks, but I retained the `isIntMinMaxRecurrenceKind` for now, to catch missing cases below

https://github.com/llvm/llvm-project/pull/141431