[MLIR][Python] add GetTypeID for llvm.struct_type and llvm.ptr and enable downcasting

mlir/include/mlir-c/Dialect/LLVM.h

@@ -58,6 +58,8 @@ MLIR_CAPI_EXPORTED MlirType mlirLLVMFunctionTypeGetReturnType(MlirType type);
 /// Returns `true` if the type is an LLVM dialect struct type.
 MLIR_CAPI_EXPORTED bool mlirTypeIsALLVMStructType(MlirType type);
 
+MLIR_CAPI_EXPORTED MlirTypeID mlirLLVMStructTypeGetTypeID();
+
 /// Returns `true` if the type is a literal (unnamed) LLVM struct type.
 MLIR_CAPI_EXPORTED bool mlirLLVMStructTypeIsLiteral(MlirType type);
 

mlir/lib/Bindings/Python/DialectLLVM.cpp

@@ -31,8 +31,8 @@ static void populateDialectLLVMSubmodule(nanobind::module_ &m) {
   // StructType
   //===--------------------------------------------------------------------===//
 
-  auto llvmStructType =
-      mlir_type_subclass(m, "StructType", mlirTypeIsALLVMStructType);
+  auto llvmStructType = mlir_type_subclass(
+      m, "StructType", mlirTypeIsALLVMStructType, mlirLLVMStructTypeGetTypeID);
 
   llvmStructType
       .def_classmethod(

mlir/lib/CAPI/Dialect/LLVM.cpp

@@ -73,6 +73,10 @@ bool mlirTypeIsALLVMStructType(MlirType type) {
   return isa<LLVM::LLVMStructType>(unwrap(type));
 }
 
+MlirTypeID mlirLLVMStructTypeGetTypeID() {
+  return wrap(LLVM::LLVMStructType::getTypeID());
+}
+
 bool mlirLLVMStructTypeIsLiteral(MlirType type) {
   return !cast<LLVM::LLVMStructType>(unwrap(type)).isIdentified();
 }

mlir/test/python/dialects/llvm.py

@@ -98,6 +98,9 @@ def testStructType():
     assert opaque.opaque
     # CHECK: !llvm.struct<"opaque", opaque>
 
+    typ = Type.parse('!llvm.struct<"zoo", (i32, i64)>')
+    assert isinstance(typ, llvm.StructType)
+
 
 # CHECK-LABEL: testSmoke
 @constructAndPrintInModule