enable scfg.restructure()

This moves the loop and branch restructuring code from the `ByteFlow`
class to the `SCFG` class. The `ByteFlow` class is scheduled for
eventual deletion anyway -- so this is a first step in that direction.

This is needed now, such that `SCFG` generated from Python abstract
syntax trees can also be transformed.

numba_rvsdg/core/datastructures/byte_flow.py

@@ -1,18 +1,11 @@
 import dis
-from copy import deepcopy
 from dataclasses import dataclass
-from typing import Generator, Callable
+from typing import Callable
 
 from numba_rvsdg.core.datastructures.scfg import SCFG
-from numba_rvsdg.core.datastructures.basic_block import RegionBlock
 from numba_rvsdg.core.datastructures.flow_info import FlowInfo
 from numba_rvsdg.core.utils import _logger, _LogWrap
 
-from numba_rvsdg.core.transformations import (
-    restructure_loop,
-    restructure_branch,
-)
-
 
 @dataclass(frozen=True)
 class ByteFlow:
@@ -60,96 +53,3 @@ def from_bytecode(code: Callable) -> "ByteFlow":  # type: ignore
         flowinfo = FlowInfo.from_bytecode(bc)
         scfg = flowinfo.build_basicblocks()
         return ByteFlow(bc=bc, scfg=scfg)
-
-    def _join_returns(self) -> "ByteFlow":
-        """Joins the return blocks within the corresponding SCFG.
-
-        This method creates a deep copy of the SCFG and performs
-        operation to join return blocks within the control flow.
-        It returns a new ByteFlow object with the updated SCFG.
-
-        Returns
-        -------
-        byteflow: ByteFlow
-            The new ByteFlow object with updated SCFG.
-        """
-        scfg = deepcopy(self.scfg)
-        scfg.join_returns()
-        return ByteFlow(bc=self.bc, scfg=scfg)
-
-    def _restructure_loop(self) -> "ByteFlow":
-        """Restructures the loops within the corresponding SCFG.
-
-        Creates a deep copy of the SCFG and performs the operation to
-        restructure loop constructs within the control flow using
-        the algorithm LOOP RESTRUCTURING from section 4.1 of Bahmann2015.
-        It applies the restructuring operation to both the main SCFG
-        and any subregions within it. It returns a new ByteFlow object
-        with the updated SCFG.
-
-        Returns
-        -------
-        byteflow: ByteFlow
-            The new ByteFlow object with updated SCFG.
-        """
-        scfg = deepcopy(self.scfg)
-        restructure_loop(scfg.region)
-        for region in _iter_subregions(scfg):
-            restructure_loop(region)
-        return ByteFlow(bc=self.bc, scfg=scfg)
-
-    def _restructure_branch(self) -> "ByteFlow":
-        """Restructures the branches within the corresponding SCFG.
-
-        Creates a deep copy of the SCFG and performs the operation to
-        restructure branch constructs within the control flow. It applies
-        the restructuring operation to both the main SCFG and any
-        subregions within it. It returns a new ByteFlow object with
-        the updated SCFG.
-
-        Returns
-        -------
-        byteflow: ByteFlow
-            The new ByteFlow object with updated SCFG.
-        """
-        scfg = deepcopy(self.scfg)
-        restructure_branch(scfg.region)
-        for region in _iter_subregions(scfg):
-            restructure_branch(region)
-        return ByteFlow(bc=self.bc, scfg=scfg)
-
-    def restructure(self) -> "ByteFlow":
-        """Applies join_returns, restructure_loop and restructure_branch
-        in the respective order on the SCFG.
-
-        Creates a deep copy of the SCFG and applies a series of
-        restructuring operations to it. The operations include
-        joining return blocks, restructuring loop constructs, and
-        restructuring branch constructs. It returns a new ByteFlow
-        object with the updated SCFG.
-
-        Returns
-        -------
-        byteflow: ByteFlow
-            The new ByteFlow object with updated SCFG.
-        """
-        scfg = deepcopy(self.scfg)
-        # close
-        scfg.join_returns()
-        # handle loop
-        restructure_loop(scfg.region)
-        for region in _iter_subregions(scfg):
-            restructure_loop(region)
-        # handle branch
-        restructure_branch(scfg.region)
-        for region in _iter_subregions(scfg):
-            restructure_branch(region)
-        return ByteFlow(bc=self.bc, scfg=scfg)
-
-
-def _iter_subregions(scfg: SCFG) -> Generator[RegionBlock, SCFG, None]:
-    for node in scfg.graph.values():
-        if isinstance(node, RegionBlock):
-            yield node
-            assert node.subregion is not None
-            yield from _iter_subregions(node.subregion)

numba_rvsdg/core/datastructures/scfg.py

@@ -39,6 +39,7 @@
 )
 
 
+
 @dataclass(frozen=True)
 class NameGenerator:
     """Unique Name Generator.
@@ -672,7 +673,8 @@ def join_returns(self) -> None:
         """Close the CFG.
 
         A closed CFG is a CFG with a unique entry and exit node that have no
-        predescessors and no successors respectively.
+        predescessors and no successors respectively. Transformation is applied
+        in-place.
         """
         # for all nodes that contain a return
         return_nodes = [
@@ -683,6 +685,51 @@ def join_returns(self) -> None:
             return_solo_name = self.name_gen.new_block_name(SYNTH_RETURN)
             self.insert_SyntheticReturn(return_solo_name, return_nodes, [])
 
+    def iter_subregions(self) -> Generator[RegionBlock, "SCFG", None]:
+        """ Iterate over all subregions of this CFG. """
+        for node in self.graph.values():
+            if isinstance(node, RegionBlock):
+                yield node
+                assert node.subregion is not None
+                yield from node.subregion.iter_subregions()
+
+    def restructure_loop(self) -> None:
+        """ Apply LOOP RESTRUCTURING transform.
+
+        Performs the operation to restructure loop constructs using the
+        algorithm LOOP RESTRUCTURING from section 4.1 of Bahmann2015.  It
+        applies an in-place restructuring operation to both the main SCFG and
+        any subregions within it.
+
+        """
+        # Avoid cyclic imports
+        from numba_rvsdg.core.transformations import restructure_loop
+
+        restructure_loop(self.region)
+        for region in self.iter_subregions():
+            restructure_loop(region)
+
+    def restructure_branch(self) -> None:
+        """Apply BRANCH RESTRUCTURING transform.
+
+        Performs the operation to restructure branch constructs using the
+        algorithm BRANCH RESTRUCTURING from section 4.2 of Bahmann2015.  It
+        applies an in-place restructuring operation to both the main SCFG and
+        any subregions within it.
+
+        """
+        # Avoid cyclic imports
+        from numba_rvsdg.core.transformations import restructure_branch
+
+        restructure_branch(self.region)
+        for region in self.iter_subregions():
+            restructure_branch(region)
+
+    def restructure(self) -> None:
+        self.join_returns()
+        self.restructure_loop()
+        self.restructure_branch()
+
     def join_tails_and_exits(
         self, tails: List[str], exits: List[str]
     ) -> Tuple[str, str]:

numba_rvsdg/tests/test_figures.py

@@ -1,6 +1,5 @@
 # mypy: ignore-errors
 
-from numba_rvsdg.core.datastructures.byte_flow import ByteFlow
 from numba_rvsdg.core.datastructures.flow_info import FlowInfo
 from numba_rvsdg.core.datastructures.scfg import SCFG
 from numba_rvsdg.tests.test_utils import SCFGComparator
@@ -441,11 +440,10 @@ def test_figure_3(self):
         ]
         flow = FlowInfo.from_bytecode(bc)
         scfg = flow.build_basicblocks()
-        byteflow = ByteFlow(bc=bc, scfg=scfg)
-        byteflow = byteflow.restructure()
+        scfg.restructure()
 
         x, _ = SCFG.from_yaml(fig_3_yaml)
-        self.assertSCFGEqual(x, byteflow.scfg)
+        self.assertSCFGEqual(x, scfg)
 
     def test_figure_4(self):
         # Figure 4 of the paper
@@ -474,8 +472,7 @@ def test_figure_4(self):
         ]
         flow = FlowInfo.from_bytecode(bc)
         scfg = flow.build_basicblocks()
-        byteflow = ByteFlow(bc=bc, scfg=scfg)
-        byteflow = byteflow.restructure()
+        scfg.restructure()
 
         x, _ = SCFG.from_yaml(fig_4_yaml)
-        self.assertSCFGEqual(x, byteflow.scfg)
+        self.assertSCFGEqual(x, scfg)

numba_rvsdg/tests/test_scc.py

@@ -54,7 +54,7 @@ def make_flow(func):
 
 def test_scc():
     f = make_flow(scc)
-    f.restructure()
+    f.scfg.restructure()
 
 
 if __name__ == "__main__":

numba_rvsdg/tests/test_scfg.py

@@ -194,7 +194,7 @@ def foo(n):
 
     def test_concealed_region_view_iter(self):
         flow = ByteFlow.from_bytecode(self.foo)
-        restructured = flow._restructure_loop()
+        flow.scfg.restructure_loop()
         expected = [
             ("python_bytecode_block_0", PythonBytecodeBlock),
             ("loop_region_0", RegionBlock),
@@ -203,7 +203,7 @@ def test_concealed_region_view_iter(self):
         received = list(
             (
                 (k, type(v))
-                for k, v in restructured.scfg.concealed_region_view.items()
+                for k, v in flow.scfg.concealed_region_view.items()
             )
         )
         self.assertEqual(expected, received)

numba_rvsdg/tests/test_simulate.py

@@ -44,7 +44,7 @@ def foo(x):
             return c
 
         flow = ByteFlow.from_bytecode(foo)
-        flow = flow.restructure()
+        flow.scfg.restructure()
 
         # if case
         self._run(foo, flow, {"x": 1})
@@ -59,7 +59,7 @@ def foo(x):
             return c
 
         flow = ByteFlow.from_bytecode(foo)
-        flow = flow.restructure()
+        flow.scfg.restructure()
 
         # loop bypass case
         self._run(foo, flow, {"x": 0})
@@ -78,7 +78,7 @@ def foo(x):
             return c
 
         flow = ByteFlow.from_bytecode(foo)
-        flow = flow.restructure()
+        flow.scfg.restructure()
 
         # loop bypass case
         self._run(foo, flow, {"x": 0})
@@ -97,7 +97,7 @@ def foo(x):
             return c
 
         flow = ByteFlow.from_bytecode(foo)
-        flow = flow.restructure()
+        flow.scfg.restructure()
 
         # loop bypass case
         self._run(foo, flow, {"x": 0})
@@ -121,7 +121,7 @@ def foo(x):
             return c
 
         flow = ByteFlow.from_bytecode(foo)
-        flow = flow.restructure()
+        flow.scfg.restructure()
 
         # no loop
         self._run(foo, flow, {"x": 0})
@@ -145,7 +145,7 @@ def foo(x):
             return c
 
         flow = ByteFlow.from_bytecode(foo)
-        flow = flow.restructure()
+        flow.scfg.restructure()
 
         # loop bypass
         self._run(foo, flow, {"x": 0})
@@ -161,7 +161,7 @@ def foo(x, y):
             return (x > 0 and x < 10) or (y > 0 and y < 10)
 
         flow = ByteFlow.from_bytecode(foo)
-        flow = flow.restructure()
+        flow.scfg.restructure()
 
         self._run(foo, flow, {"x": 5, "y": 5})
 
@@ -175,7 +175,7 @@ def foo(s, e):
             return c
 
         flow = ByteFlow.from_bytecode(foo)
-        flow = flow.restructure()
+        flow.scfg.restructure()
 
         # no looping
         self._run(foo, flow, {"s": 0, "e": 0})