[llvm] [LoopUtils] Cache VFs in addDiffRuntimeChecks (NFC) (PR #130157)

[Ramkumar Ramachandra via llvm-commits]

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@@ -2048,12 +2048,18 @@ Value *llvm::addDiffRuntimeChecks(
   // Map to keep track of created compares, The key is the pair of operands for
   // the compare, to allow detecting and re-using redundant compares.
   DenseMap<std::pair<Value *, Value *>, Value *> SeenCompares;
+  // Map to detect redundant values returned by GetVF.
+  DenseMap<Type *, Value *> SeenVFs;
   for (const auto &[SrcStart, SinkStart, AccessSize, NeedsFreeze] : Checks) {
     Type *Ty = SinkStart->getType();
+    Value *VF = SeenVFs.lookup(Ty);
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artagnon wrote:

> This looks like a bug fix to me, given we were previously using the same VF value regardless of the type of SinkStart. Although I suppose it's hard to see how the bug would trigger.

Yes, and I'm currently investigating to see if the change is testable: it could very well be untestable as LAA forbids different store sizes to begin with.

https://github.com/llvm/llvm-project/pull/130157