[flang-commits] [flang] [flang] Create TBAA subtree for COMMON block variables. (PR #153918)

[Tom Eccles via flang-commits]

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@@ -310,14 +318,55 @@ void AddAliasTagsPass::runOnAliasInterface(fir::FirAliasTagOpInterface op,
              source.kind == fir::AliasAnalysis::SourceKind::Global &&
              !source.isBoxData()) {
     mlir::SymbolRefAttr glbl = llvm::cast<mlir::SymbolRefAttr>(source.origin.u);
-    const char *name = glbl.getRootReference().data();
-    LLVM_DEBUG(llvm::dbgs().indent(2) << "Found reference to global " << name
-                                      << " at " << *op << "\n");
-    if (source.isPointer())
+    mlir::StringAttr name = glbl.getRootReference();
+    LLVM_DEBUG(llvm::dbgs().indent(2) << "Found reference to global "
+                                      << name.str() << " at " << *op << "\n");
+    if (source.isPointer()) {
       tag = state.getFuncTreeWithScope(func, scopeOp).targetDataTree.getTag();
-    else
-      tag =
-          state.getFuncTreeWithScope(func, scopeOp).globalDataTree.getTag(name);
+    } else {
+      // In general, place the tags under the "global data" root.
+      fir::TBAATree::SubtreeState *subTree =
+          &state.getMutableFuncTreeWithScope(func, scopeOp).globalDataTree;
+
+      // The COMMON blocks have their own sub-tree root under the "global data"
+      // root, which is named after the name of the COMMON block.
+      // If we can identify the name of the member variable, then
+      // we create a sub-tree under the root of the COMMON block
+      // and place the tag there. If we cannot identify the name
+      // of the member variable (e.g. for whatever reason there is no
+      // fir.declare for it), then we place the tag under the root
+      // of the COMMON block.
+      auto globalOp = state.getGlobalDefiningOp(name);
+      // TODO: this is a subtle identification of the fact that
+      // the variable belongs to a COMMON block.
+      // Should we have an attribute on [hl]fir.declare
+      // that specifies the name of the COMMON block the variable
+      // belongs to?
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tblah wrote:

Yes I agree this would be better. In OpenMP we handle it all whilst we still have access to the symbol table, but I think with that gone it would be worth including that information here.

https://github.com/llvm/llvm-project/pull/153918