split cf lowering (#186)

split `cf` lowering into a separate dialect so we can have `cf` co-exist
with `scf` in decorators, some Python syntax may require `cf` such as
`pass`. This gives us some more choice when we want to lower as much as
possible to `scf` instead of lowering everything into `cf`.

Author: Roger-luo

src/kirin/dialects/cf/__init__.py

@@ -1,9 +1,17 @@
+"""Control flow dialect.
+
+This dialect provides a low-level control flow representation.
+
+This dialect does not provide any lowering strategies, to lowering
+a Python AST to this dialect, use the `kirin.dialects.lowering.cf` dialect
+with this dialect.
+"""
+
 from kirin.dialects.cf import (
     emit as emit,
     constprop as constprop,
     typeinfer as typeinfer,
 )
-from kirin.dialects.cf.lower import CfLowering as CfLowering
 from kirin.dialects.cf.stmts import (
     Branch as Branch,
     ConditionalBranch as ConditionalBranch,

src/kirin/dialects/lowering/__init__.py

@@ -0,0 +1,7 @@
+"""This module contains the dialects for choosing different lowering strategies.
+
+The dialects defined inside this module do not provide any new statements, it only
+provide different lowering strategies for existing statements.
+"""
+
+from . import cf as cf

src/kirin/dialects/cf/lower.py src/kirin/dialects/lowering/cf.pysrc/kirin/dialects/cf/lower.py renamed to src/kirin/dialects/lowering/cf.py

@@ -1,10 +1,14 @@
+"""Lowering Python AST to cf dialect.
+"""
+
 import ast
 
 from kirin import ir
 from kirin.lowering import Frame, Result, FromPythonAST, LoweringState
 from kirin.exceptions import DialectLoweringError
 from kirin.dialects.cf import stmts as cf
-from kirin.dialects.cf.dialect import dialect
+
+dialect = ir.Dialect("lowering.cf")
 
 
 @dialect.register

src/kirin/prelude.py

@@ -7,7 +7,7 @@
 
 from kirin.ir import Method, dialect_group
 from kirin.passes import aggressive
-from kirin.dialects import cf, func, math, ilist
+from kirin.dialects import cf, func, math, ilist, lowering
 from kirin.dialects.py import (
     cmp,
     len,
@@ -56,7 +56,7 @@ def run_pass(mt: Method) -> None:
     return run_pass
 
 
-@dialect_group(python_basic.union([list, range, slice, cf, func, math]))
+@dialect_group(python_basic.union([list, range, slice, cf, lowering.cf, func, math]))
 def python_no_opt(self):
     """The Python dialect without optimization passes."""
 
@@ -66,7 +66,7 @@ def run_pass(mt: Method) -> None:
     return run_pass
 
 
-@dialect_group(python_basic.union([ilist, range, slice, cf, func, math]))
+@dialect_group(python_basic.union([ilist, range, slice, cf, lowering.cf, func, math]))
 def basic_no_opt(self):
     """The basic kernel without optimization passes. This is a builtin
     eDSL that includes the basic dialects that are commonly used in