[flang-commits] [flang] [flang] Create TBAA subtree for COMMON block variables. (PR #156558)

[Tom Eccles via flang-commits]

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@@ -98,8 +223,65 @@ class PassState {
   // attachment.
   bool attachLocalAllocTag();
 
+  // Return fir.global for the given name.
+  fir::GlobalOp getGlobalDefiningOp(mlir::StringAttr name) const {
+    return symTab.lookup<fir::GlobalOp>(name);
+  }
+
+  // Process fir::FortranVariableStorageOpInterface operations within
+  // the given op, and fill in declToStorageMap with the information
+  // about their physical storages and layouts.
+  void collectPhysicalStorageAliasSets(mlir::Operation *op);
+
+  // Return the byte size of the given declaration.
+  std::size_t getDeclarationSize(fir::FortranVariableStorageOpInterface decl) {
+    mlir::Type memType = fir::unwrapRefType(decl.getBase().getType());
+    auto [size, alignment] =
+        getTypeSizeAndAlignment(memType, llvmTypeConverter);
+    return llvm::alignTo(size, alignment);
+  }
+
+  // A StorageDesc specifies an operation that defines a physical storage
+  // and the <offset, size> pair within that physical storage where
+  // a variable resides.
+  struct StorageDesc {
+    StorageDesc() = delete;
+    StorageDesc(mlir::Operation *storageDef, std::uint64_t start,
+                std::size_t size)
+        : storageDef(storageDef), interval(start, size) {}
+
+    // Return a string representing the byte range of the variable within
+    // its storage, e.g. bytes_0_to_0 for a 1-byte variable starting
+    // at offset 0.
+    std::string getByteRangeStr() const {
+      return ("bytes_" + llvm::Twine(interval.getStart()) + "_to_" +
+              llvm::Twine(interval.getEnd()))
+          .str();
+    }
+
+    mlir::Operation *storageDef;
+    IntervalTy interval;
+  };
+
+  const StorageDesc *getStorageDesc(mlir::Operation *op) {
+    auto it = declToStorageMap.find(op);
+    return it == declToStorageMap.end() ? nullptr : &it->second;
+  }
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tblah wrote:

This is currently only called when processing non-pointer global variables. Populating `declToStorageMap` looks expensive. I think it would be better to populate it on demand the first time this method is called, so that we don't incur the expense for top level operations that do not refer to any non-pointer global variables.

https://github.com/llvm/llvm-project/pull/156558