[llvm] [LoadStoreVectorizer] Propagate alignment through contiguous chain (PR #145733)

[Alex MacLean via llvm-commits]

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@@ -1634,3 +1645,27 @@ std::optional<APInt> Vectorizer::getConstantOffset(Value *PtrA, Value *PtrB,
         .sextOrTrunc(OrigBitWidth);
   return std::nullopt;
 }
+
+void Vectorizer::propagateBestAlignmentsInChain(ArrayRef<ChainElem> C) const {
+  ChainElem BestAlignedElem = C[0];
+  Align BestAlignSoFar = getLoadStoreAlignment(C[0].Inst);
+
+  for (const ChainElem &E : C) {
+    Align OrigAlign = getLoadStoreAlignment(E.Inst);
+    if (OrigAlign > BestAlignSoFar) {
+      BestAlignedElem = E;
+      BestAlignSoFar = OrigAlign;
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AlexMaclean wrote:

Should we continue here? or move the rest of this loop into an else? 

https://github.com/llvm/llvm-project/pull/145733