[llvm] [LV] Initial support for stores in early exit loops (PR #137774)

[Graham Hunter via llvm-commits]

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@@ -407,6 +407,13 @@ class LoopVectorizationLegality {
     return hasUncountableEarlyExit() ? getUncountableEdge()->second : nullptr;
   }
 
+  /// Returns true if this is an early exit loop containing a store.
+  bool isConditionCopyRequired() const { return RequiresEarlyExitConditionCopy; }
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huntergr-arm wrote:

The store can be anywhere in the loop, since we either execute a full vector iteration as normal or we bail out to the scalar tail if an exit would occur in the middle.

We need to do this for all exits, so a single transformation to copy and reorder the exit condition IR is sufficient.

https://github.com/llvm/llvm-project/pull/137774