[Py] [PyCDE] Add `get_fields` to struct type and use it in pycde (#1364)

PyCDE uses this for error checking and `.` access.

frontends/PyCDE/src/pycde/support.py

@@ -24,12 +24,23 @@ class Value:
         return Value(hw.ArrayGetOp.create(self.value, idx))
 
     if isinstance(self.type, hw.StructType):
+      fields = self.type.get_fields()
+      if sub not in [name for name, _ in fields]:
+        raise ValueError(f"Struct field '{sub}' not found in {self.type}")
       with get_user_loc():
         return Value(hw.StructExtractOp.create(self.value, sub))
 
     raise TypeError(
         "Subscripting only supported on hw.array and hw.struct types")
 
+  def __getattr__(self, attr):
+    if isinstance(self.type, hw.StructType):
+      fields = self.type.get_fields()
+      if attr in [name for name, _ in fields]:
+        with get_user_loc():
+          return Value(hw.StructExtractOp.create(self.value, attr))
+    raise AttributeError(f"'Value' object has no attribute '{attr}'")
+
 
 # PyCDE needs a custom version of this to support python classes.
 def var_to_attribute(obj) -> ir.Attribute:

frontends/PyCDE/test/pycde_types.py

@@ -1,6 +1,15 @@
 # RUN: %PYTHON% %s 2>&1 | FileCheck %s
 
 from pycde import dim, types
+import sys
+
+# CHECK: [('foo', Type(i1)), ('bar', Type(i13))]
+# CHECK: i1
+st1 = types.struct({"foo": types.i1, "bar": types.i13})
+fields = st1.get_fields()
+sys.stderr.write(str(fields) + "\n")
+st1.get_field("foo").dump()
+print()
 
 # CHECK: i6
 array1 = dim(types.i6)

include/circt-c/Dialect/HW.h

@@ -28,6 +28,7 @@ struct HWStructFieldInfo {
   MlirStringRef name;
   MlirType type;
 };
+typedef struct HWStructFieldInfo HWStructFieldInfo;
 
 //===----------------------------------------------------------------------===//
 // Dialect API.
@@ -80,13 +81,17 @@ MLIR_CAPI_EXPORTED MlirType hwInOutTypeGet(MlirType element);
 MLIR_CAPI_EXPORTED MlirType hwInOutTypeGetElementType(MlirType);
 
 /// Creates an HW struct type in the context associated with the elements.
-MLIR_CAPI_EXPORTED MlirType
-hwStructTypeGet(MlirContext ctx, intptr_t numElements,
-                struct HWStructFieldInfo const *elements);
+MLIR_CAPI_EXPORTED MlirType hwStructTypeGet(MlirContext ctx,
+                                            intptr_t numElements,
+                                            HWStructFieldInfo const *elements);
 
 MLIR_CAPI_EXPORTED MlirType hwStructTypeGetField(MlirType structType,
                                                  MlirStringRef fieldName);
 
+MLIR_CAPI_EXPORTED HWStructFieldInfo
+hwStructTypeGetFieldNum(MlirType structType, unsigned idx);
+MLIR_CAPI_EXPORTED intptr_t hwStructTypeGetNumFields(MlirType structType);
+
 MLIR_CAPI_EXPORTED MlirType hwTypeAliasTypeGet(MlirStringRef scope,
                                                MlirStringRef name,
                                                MlirType innerType);

lib/Bindings/Python/HWModule.cpp

@@ -61,9 +61,20 @@ void circt::python::populateDialectHWSubmodule(py::module &m) {
             return cls(hwStructTypeGet(ctx, mlirFieldInfos.size(),
                                        mlirFieldInfos.data()));
           })
-      .def("get_field", [](MlirType self, std::string fieldName) {
-        return hwStructTypeGetField(
-            self, mlirStringRefCreateFromCString(fieldName.c_str()));
+      .def("get_field",
+           [](MlirType self, std::string fieldName) {
+             return hwStructTypeGetField(
+                 self, mlirStringRefCreateFromCString(fieldName.c_str()));
+           })
+      .def("get_fields", [](MlirType self) {
+        intptr_t num_fields = hwStructTypeGetNumFields(self);
+        py::list fields;
+        for (intptr_t i = 0; i < num_fields; ++i) {
+          auto field = hwStructTypeGetFieldNum(self, i);
+          std::string name(field.name.data, field.name.length);
+          fields.append(py::make_tuple(name, field.type));
+        }
+        return fields;
       });
 
   mlir_type_subclass(m, "TypeAliasType", hwTypeIsATypeAliasType)

lib/CAPI/Dialect/HW.cpp

@@ -79,6 +79,20 @@ MlirType hwStructTypeGetField(MlirType structType, MlirStringRef fieldName) {
   return wrap(st.getFieldType(unwrap(fieldName)));
 }
 
+intptr_t hwStructTypeGetNumFields(MlirType structType) {
+  StructType st = unwrap(structType).cast<StructType>();
+  return st.getElements().size();
+}
+
+HWStructFieldInfo hwStructTypeGetFieldNum(MlirType structType, unsigned idx) {
+  StructType st = unwrap(structType).cast<StructType>();
+  auto cppField = st.getElements()[idx];
+  HWStructFieldInfo ret;
+  ret.name = wrap(cppField.name);
+  ret.type = wrap(cppField.type);
+  return ret;
+}
+
 bool hwTypeIsATypeAliasType(MlirType type) {
   return unwrap(type).isa<TypeAliasType>();
 }