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

[David Sherwood via llvm-commits]

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@@ -1209,6 +1210,36 @@ bool LoopVectorizationLegality::canVectorizeMemory() {
     });
   }
 
+  // FIXME: Remove or reduce this restriction. We're in a bit of an odd spot
+  //        since we're (potentially) doing the load out of its normal order
+  //        in the loop and that may throw off dependency checking.
+  //        A forward dependency should be fine, but a backwards dep may not
+  //        be even if LAA thinks it is due to performing the load for the
+  //        vector iteration i+1 in vector iteration i.
+  if (isConditionCopyRequired()) {
+    assert(EarlyExitLoad.has_value() && "EE Store without condition load.");
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david-arm wrote:

If you change `isConditionCopyRequired` to test for `EarlyExitLoad` having a value, then you don't need this assert.

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