[llvm] [LV] Add support for cmp reductions with decreasing IVs. (PR #140451)

[Florian Hahn via llvm-commits]

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@@ -713,36 +715,66 @@ RecurrenceDescriptor::isFindLastIVPattern(Loop *TheLoop, PHINode *OrigPhi,
       return std::nullopt;
 
     const SCEV *Step = AR->getStepRecurrence(SE);
-    if (!SE.isKnownPositive(Step))
+
+    if (isFindFirstIVRecurrenceKind(Kind)) {
+      if (!SE.isKnownNegative(Step))
+        return std::nullopt;
+    } else if (!SE.isKnownPositive(Step))
       return std::nullopt;
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fhahn wrote:

Updated, thanks

https://github.com/llvm/llvm-project/pull/140451