[llvm] [LV] Add initial legality checks for ee loops with stores (PR #145663)

[David Sherwood via llvm-commits]

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@@ -407,6 +407,14 @@ class LoopVectorizationLegality {
     return hasUncountableEarlyExit() ? getUncountableEdge()->second : nullptr;
   }
 
+  /// Returns true if this is an early exit loop containing a store.
+  bool isConditionCopyRequired() const { return EarlyExitLoad.has_value(); }
+
+  /// Returns the load instruction, if any, directly used for an exit comparison
+  /// in and early exit loop containing state-changing or potentially-faulting
+  /// operations.
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david-arm wrote:

Given we already have support for vectorising early exit loops with loads in them, I think the name `getEarlyExitLoad` could be confusing. It also makes it sound like there is only one load in the loop. How about something like `getCriticalLoadInUncountableEarlyExit`? The problem is that we support vectorising loops with countable early exits so we have to be specific what we mean.

https://github.com/llvm/llvm-project/pull/145663