[fx] Use module Operations instead of Module.

This was only used in certain advanced uses of the API that want to build into their own module. The MLIR `Module` class is an awkward/restrictive way to require this to go as only some things will have it. Just switch everything to be based on a module `Operation`.

python/torch_mlir/extras/fx_importer.py

@@ -302,7 +302,9 @@ def sparsity_encoding(shape: torch.Size, sparsity: SparsityMeta) -> str:
     if sparsity.layout is torch.sparse_coo:
         assert sparse_dim >= 2 and blocksize is None
         trail_dim = batch_dim + sparse_dim - 1
-        coords = ",".join(f"d{d}:singleton(nonunique,soa)" for d in range(batch_dim+1, trail_dim))
+        coords = ",".join(
+            f"d{d}:singleton(nonunique,soa)" for d in range(batch_dim + 1, trail_dim)
+        )
         sep = "," if sparse_dim > 2 else ""
         lvls = f"d{batch_dim}:compressed(nonunique),{coords}{sep}d{trail_dim}:singleton(soa)"
     elif sparsity.layout is torch.sparse_csr:
@@ -415,7 +417,7 @@ class FxImporter:
     __slots__ = [
         "_c",
         "_cc",
-        "_m",
+        "_m_op",
         "_m_ip",
         "_py_attr_tracker",
         "_hooks",
@@ -425,28 +427,31 @@ class FxImporter:
     def __init__(
         self,
         *,
-        module: Optional[Module] = None,
+        module_op: Optional[Operation] = None,
         context: Optional[Context] = None,
         config_check: bool = True,
         py_attr_tracker: Optional["RefTracker"] = None,
         hooks: Optional[FxImporterHooks] = None,
     ):
-        if module is not None:
-            assert context is None, "If configuring with a Module, context must be None"
-            self._m = module
-            self._c = self.module.context
+        if module_op is not None:
+            assert (
+                context is None
+            ), "If configuring with a module op, context must be None"
+            self._m_op = module_op
+            self._c = self._m_op.context
         else:
             self._c = context if context else Context()
-            self._m = Module.create(Location.unknown(self._c))
+            self._m_op = Module.create(Location.unknown(self._c)).operation
+        body = self._m_op.regions[0].blocks[0]
         if config_check:
             # Production code can disable this for a bit of a boost.
             self._config_check()
         self._py_attr_tracker = py_attr_tracker or RefTracker()
         self._cc = ContextCache(self._c, py_attr_tracker=self._py_attr_tracker)
-        self._m_ip = InsertionPoint(self._m.body)
+        self._m_ip = InsertionPoint(body)
         self._hooks = hooks or FxImporterHooks()
-        self.symbol_table = SymbolTable(self._m.operation)
-        self._hooks.prepare_module(self._m.operation)
+        self.symbol_table = SymbolTable(self._m_op)
+        self._hooks.prepare_module(self._m_op)
 
     def _config_check(self):
         for dname in REQUIRED_DIALCTS:
@@ -458,17 +463,17 @@ class FxImporter:
                     f"The MLIR context {self._c} is missing required dialect '{dname}'"
                 )
 
-    @property
-    def module(self) -> Module:
-        return self._m
-
     @property
     def module_op(self) -> Operation:
-        return self._m.operation
+        return self._m_op
 
     def import_program(
-        self, prog: torch.export.ExportedProgram, *, func_name: str = "main"
-    ):
+        self,
+        prog: torch.export.ExportedProgram,
+        *,
+        func_name: str = "main",
+        func_visibility: Optional[str] = None,
+    ) -> Operation:
         """Imports an ExportedProgram according to our chosen canonical representation.
 
         This mechanism is the fully general solution for handling an ExportedProgram
@@ -490,6 +495,8 @@ class FxImporter:
         It is recommended that integrators subclass and override the `resolve_literal`
         method to control access to mutable buffers and parameters. Without that, the
         default policy is to capture them as frozen values.
+
+        Returns the created entry function as a generic Operation.
         """
         # Create lookaside table of placeholders/outputs.
         placeholder_nodes: Dict[str, Node] = {}
@@ -628,7 +635,9 @@ class FxImporter:
 
         # Create the function.
         with loc:
-            func_op = func_dialect.FuncOp(func_name, ftype, ip=self._m_ip)
+            func_op = func_dialect.FuncOp(
+                func_name, ftype, ip=self._m_ip, visibility=func_visibility
+            )
             entry_block = Block.create_at_start(func_op.body, ftype.inputs)
 
         node_importer = GraphNodeImporter(
@@ -668,9 +677,13 @@ class FxImporter:
         )
         node_importer.return_node_values(loc, user_outputs)
         self.symbol_table.insert(func_op)
+        return func_op.operation
 
     def import_frozen_program(
-        self, prog: torch.export.ExportedProgram, func_name: str = "main"
+        self,
+        prog: torch.export.ExportedProgram,
+        func_name: str = "main",
+        func_visibility: Optional[str] = None,
     ):
         """Imports a consolidated torch.export.ExportedProgram instance.
 
@@ -750,7 +763,7 @@ class FxImporter:
                 node.replace_all_uses_with(replacement)
                 g.erase_node(node)
 
-        self.import_stateless_graph(g, func_name)
+        self.import_stateless_graph(g, func_name, func_visibility=func_visibility)
 
     def import_graph_module(self, gm: GraphModule):
         """Low-level import of a GraphModule assuming that it has been functionalized.
@@ -760,7 +773,9 @@ class FxImporter:
         """
         self.import_stateless_graph(gm.graph)
 
-    def import_stateless_graph(self, g: Graph, func_name: str = "main"):
+    def import_stateless_graph(
+        self, g: Graph, func_name: str = "main", func_visibility: Optional[str] = None
+    ):
         """Low-level import of a functionalized, assumed stateless Graph as a func.
 
         TODO: This mechanism is deprecated by the `import_program` entry-point and
@@ -775,6 +790,7 @@ class FxImporter:
                 func_name,
                 ftype,
                 ip=self._m_ip,
+                func_visibility=func_visibility,
             )
             entry_block = Block.create_at_start(func.body, ftype.inputs)
         node_importer = GraphNodeImporter(