[flang-commits] [flang] [fir][AddAliasTags] allow usage of AddAliasTag pass after FirToMemref (PR #219493)

[Caroline Newcombe via flang-commits]

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@@ -817,15 +817,28 @@ void AddAliasTagsPass::runOnAliasInterface(fir::FirAliasTagOpInterface op,
   } else if (enableLocalAllocs &&
              source.kind == fir::AliasAnalysis::SourceKind::Allocate) {
     std::optional<llvm::StringRef> name;
-    mlir::Operation *sourceOp =
-        llvm::cast<mlir::Value>(source.origin.u).getDefiningOp();
+    mlir::Value sourceVal = llvm::cast<mlir::Value>(source.origin.u);
+    mlir::Operation *sourceOp = sourceVal.getDefiningOp();
     bool unknownAllocOp = false;
     if (auto alloc = mlir::dyn_cast_or_null<fir::AllocaOp>(sourceOp))
       name = alloc.getUniqName();
     else if (auto alloc = mlir::dyn_cast_or_null<fir::AllocMemOp>(sourceOp))
       name = alloc.getUniqName();
-    else
+    else if (mlir::StringAttr nameAttr =
+                 sourceOp ? sourceOp->getAttrOfType<mlir::StringAttr>(
+                                fir::AllocaOp::getUniqNameAttrName())
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cenewcombe wrote:

Your explanation about deriving the name from the allocation operation, along with the change to `tbaa-codegen2.fir`, made me reconsider the `!empty` check. Since accesses sharing an allocation are guaranteed to use the same name, an empty name is still a sound shared bucket ("allocated data/"). The reset moves compiler temps with an empty name onto the parent "allocated data" tag, which makes them `MayAlias` named local allocations and loses existing TBAA precision.

Could we therefore drop the check and `name.reset`? Sorry for the mix-up here.

https://github.com/llvm/llvm-project/pull/219493