Improve dummy argument identification

Make sure they're not block arguments not on functions.  Encapsulate
the check.

Author: jdenny-ornl

flang/include/flang/Optimizer/Analysis/AliasAnalysis.h

@@ -93,6 +93,9 @@ struct AliasAnalysis {
 
   /// Return the memory source of a value.
   Source getSource(mlir::Value);
+
+  /// Return true if `v` is a dummy argument.
+  static bool isDummyArgument(mlir::Value v);
 };
 
 inline llvm::raw_ostream &operator<<(llvm::raw_ostream &os,

flang/lib/Optimizer/Analysis/AliasAnalysis.cpp

@@ -28,14 +28,6 @@ using namespace mlir;
 // AliasAnalysis: alias
 //===----------------------------------------------------------------------===//
 
-static bool isDummyArgument(mlir::Value v) {
-  auto blockArg{v.dyn_cast<mlir::BlockArgument>()};
-  if (!blockArg)
-    return false;
-
-  return blockArg.getOwner()->isEntryBlock();
-}
-
 /// Temporary function to skip through all the no op operations
 /// TODO: Generalize support of fir.load
 static mlir::Value getOriginalDef(mlir::Value v) {
@@ -429,4 +421,13 @@ AliasAnalysis::Source AliasAnalysis::getSource(mlir::Value v) {
   return {v, type, ty, attributes, approximateSource};
 }
 
+bool AliasAnalysis::isDummyArgument(mlir::Value v) {
+  auto blockArg{v.dyn_cast<mlir::BlockArgument>()};
+  if (!blockArg)
+    return false;
+  auto *owner{blockArg.getOwner()};
+  return owner->isEntryBlock() &&
+         mlir::isa<mlir::FunctionOpInterface>(owner->getParentOp());
+}
+
 } // namespace fir

flang/lib/Optimizer/Transforms/AddAliasTags.cpp

@@ -170,29 +170,24 @@ void AddAliasTagsPass::runOnAliasInterface(fir::FirAliasTagOpInterface op,
       LLVM_DEBUG(llvm::dbgs().indent(2) << "Found reference to direct " << name
                                         << " at " << *op << "\n");
       tag = state.getFuncTree(func).directDataTree.getTag(name);
-    } else {
-      bool sourceIsDummyArgument = false;
-      if (auto blockArg =
-              source.u.get<mlir::Value>().dyn_cast<mlir::BlockArgument>())
-        sourceIsDummyArgument = blockArg.getOwner()->isEntryBlock();
-      if (sourceIsDummyArgument) {
-        std::string name = getFuncArgName(source.u.get<mlir::Value>());
-        if (!name.empty()) {
-          LLVM_DEBUG(llvm::dbgs().indent(2)
-                     << "Found reference to direct from dummy argument " << name
-                     << " at " << *op << "\n");
-          tag = state.getFuncTree(func).directDataTree.getTag(name);
-        } else {
-          LLVM_DEBUG(llvm::dbgs().indent(2)
-                     << "WARN: for direct, couldn't find a name for dummy "
-                     << "argument " << *op << "\n");
-        }
+    } else if (fir::AliasAnalysis::isDummyArgument(
+                   source.u.get<mlir::Value>())) {
+      std::string name = getFuncArgName(source.u.get<mlir::Value>());
+      if (!name.empty()) {
+        LLVM_DEBUG(llvm::dbgs().indent(2)
+                   << "Found reference to direct from dummy argument " << name
+                   << " at " << *op << "\n");
+        tag = state.getFuncTree(func).directDataTree.getTag(name);
       } else {
-        // SourceKind::Direct is likely to be extended to more cases in the
-        // future
-        LLVM_DEBUG(llvm::dbgs().indent(2) << "Can't get name for direct "
-                                          << source << " at " << *op << "\n");
+        LLVM_DEBUG(llvm::dbgs().indent(2)
+                   << "WARN: for direct, couldn't find a name for dummy "
+                   << "argument " << *op << "\n");
       }
+    } else {
+      // SourceKind::Direct is likely to be extended to more cases in the
+      // future
+      LLVM_DEBUG(llvm::dbgs().indent(2) << "Can't get name for direct "
+                                        << source << " at " << *op << "\n");
     }
 
     // TBAA for local allocations