[llvm] [LAA] Be more precise on different store sizes (PR #122318)

[Florian Hahn via llvm-commits]

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@@ -2061,14 +2061,12 @@ MemoryDepChecker::getDependenceDistanceStrideAndSize(
     return MemoryDepChecker::Dependence::Unknown;
   }
 
-  TypeSize AStoreSz = DL.getTypeStoreSize(ATy);
-  TypeSize BStoreSz = DL.getTypeStoreSize(BTy);
-
-  // If store sizes are not the same, set TypeByteSize to zero, so we can check
-  // it in the caller isDependent.
   uint64_t ASz = DL.getTypeAllocSize(ATy);
   uint64_t BSz = DL.getTypeAllocSize(BTy);
-  uint64_t TypeByteSize = (AStoreSz == BStoreSz) ? BSz : 0;
+
+  // The TypeByteSize is used to scale Distance and VF. In these contexts, the
+  // only size that matters is the size of the Sink.
+  uint64_t TypeByteSize = BSz;
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fhahn wrote:

It's not clear to me why picking the size of the sink is always correct. I've not checked all uses, but intuitively the larger size may serve as an upper bound for some (all?) uses

https://github.com/llvm/llvm-project/pull/122318