[acc][flang] Add getInitRegion() to GlobalVariableOpInterface (#169569)

Some globals (e.g., fir.global) have initialization regions that may
transitively reference other globals or type descriptors. Add
getInitRegion() to GlobalVariableOpInterface to retrieve these regions,
returning Region* (nullptr if the global uses attributes for
initialization, as with memref.global).

Author: razvanlupusoru

flang/include/flang/Optimizer/OpenACC/Support/FIROpenACCOpsInterfaces.h

@@ -65,6 +65,7 @@ struct GlobalVariableModel
     : public mlir::acc::GlobalVariableOpInterface::ExternalModel<
           GlobalVariableModel, fir::GlobalOp> {
   bool isConstant(mlir::Operation *op) const;
+  mlir::Region *getInitRegion(mlir::Operation *op) const;
 };
 
 template <typename Op>

flang/lib/Optimizer/OpenACC/Support/FIROpenACCOpsInterfaces.cpp

@@ -71,6 +71,11 @@ bool GlobalVariableModel::isConstant(mlir::Operation *op) const {
   return globalOp.getConstant().has_value();
 }
 
+mlir::Region *GlobalVariableModel::getInitRegion(mlir::Operation *op) const {
+  auto globalOp = mlir::cast<fir::GlobalOp>(op);
+  return globalOp.hasInitializationBody() ? &globalOp.getRegion() : nullptr;
+}
+
 // Helper to recursively process address-of operations in derived type
 // descriptors and collect all needed fir.globals.
 static void processAddrOfOpInDerivedTypeDescriptor(

mlir/include/mlir/Dialect/OpenACC/OpenACCOpsInterfaces.td

@@ -72,6 +72,8 @@ def GlobalVariableOpInterface : OpInterface<"GlobalVariableOpInterface"> {
       "isConstant", (ins), [{
         return false;
       }]>,
+    InterfaceMethod<"Get the initialization region (returns nullptr if none)",
+      "::mlir::Region*", "getInitRegion", (ins)>,
   ];
 }
 

mlir/lib/Dialect/OpenACC/IR/OpenACC.cpp

@@ -227,6 +227,11 @@ struct MemrefGlobalVariableModel
     auto globalOp = cast<memref::GlobalOp>(op);
     return globalOp.getConstant();
   }
+
+  Region *getInitRegion(Operation *op) const {
+    // GlobalOp uses attributes for initialization, not regions
+    return nullptr;
+  }
 };
 
 /// Helper function for any of the times we need to modify an ArrayAttr based on

mlir/unittests/Dialect/OpenACC/OpenACCOpsInterfacesTest.cpp

@@ -75,6 +75,28 @@ TEST_F(OpenACCOpsInterfacesTest, GlobalVariableOpInterfaceConstant) {
   EXPECT_TRUE(globalVarIface.isConstant());
 }
 
+TEST_F(OpenACCOpsInterfacesTest, GlobalVariableOpInterfaceInitRegion) {
+  // Test that memref::GlobalOp returns nullptr for getInitRegion()
+  // since it uses attributes for initialization, not regions
+
+  auto memrefType = MemRefType::get({10}, builder.getF32Type());
+  OwningOpRef<memref::GlobalOp> globalOp = memref::GlobalOp::create(
+      builder, loc,
+      /*sym_name=*/builder.getStringAttr("test_global"),
+      /*sym_visibility=*/builder.getStringAttr("private"),
+      /*type=*/TypeAttr::get(memrefType),
+      /*initial_value=*/Attribute(),
+      /*constant=*/UnitAttr(),
+      /*alignment=*/IntegerAttr());
+
+  auto globalVarIface =
+      dyn_cast<GlobalVariableOpInterface>(globalOp->getOperation());
+  ASSERT_TRUE(globalVarIface != nullptr);
+
+  // memref::GlobalOp doesn't have regions for initialization
+  EXPECT_EQ(globalVarIface.getInitRegion(), nullptr);
+}
+
 //===----------------------------------------------------------------------===//
 // AddressOfGlobalOpInterface Tests
 //===----------------------------------------------------------------------===//