[llvm] [LAA] Allow zero-distance dependences between mixed-width accesses (PR #221531)

[Ramkumar Ramachandra via llvm-commits]

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@@ -2285,6 +2285,10 @@ MemoryDepChecker::getDependenceDistanceStrideAndSize(
   std::optional<uint64_t> CommonStride;
   if (StrideAScaled == StrideBScaled)
     CommonStride = StrideAScaled;
+  // The zero-distance mixed-width case in isDependent relies on each access
+  // fitting within CommonStride.
+  assert((!CommonStride || *CommonStride >= std::max(ASz, BSz)) &&
+         "Common stride must cover both accesses");
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artagnon wrote:

Ah, the assert isn't so useful here -- as readers can infer it trivially from the code above; I was suggesting putting it at the use-site instead of the comment re-computing ASz and BSz for the assert using [[maybe_unused]], which would not affect release performance, but if it's too much trouble, simply adjust the comment to be a bit clearer, and let's land this?

https://github.com/llvm/llvm-project/pull/221531