[llvm] [LLVM][MemCpyOpt] Unify alias tags if we optimize allocas (PR #129537)

[Dominik Adamski via llvm-commits]

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@@ -1681,6 +1687,14 @@ bool MemCpyOptPass::performStackMoveOptzn(Instruction *Load, Instruction *Store,
   for (Instruction *I : NoAliasInstrs)
     I->setMetadata(LLVMContext::MD_noalias, nullptr);
 
+  // If we merge two allocas we need to uniform alias tags as well
+  if (!SrcAllocaInstUsers.empty()) {
+    MDNode *mergeTBAA =
+        (*SrcAllocaInstUsers.begin())->getMetadata(LLVMContext::MD_tbaa);
+    for (Instruction *It : DestAllocaInstUsers)
+      It->setMetadata(LLVMContext::MD_tbaa, mergeTBAA);
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DominikAdamski wrote:

I dropped tbaa metadata and I added another test.

https://github.com/llvm/llvm-project/pull/129537