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

[Ramkumar Ramachandra via llvm-commits]

================
@@ -259,17 +267,33 @@ class RecurrenceDescriptor {
     return Kind == RecurKind::FindLastIV;
   }
 
+  /// Returns true if the recurrence kind is of the form
+  ///   select(cmp(),x,y) where one of (x,y) is an increasing or decreasing loop
+  ///   induction.
+  static bool isFindIVRecurrenceKind(RecurKind Kind) {
----------------
artagnon wrote:

Factor out isFindFirstIVRecurrenceKind?

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