Loop Region Code Generation (#1597)

This PR adapts code generation to make use of hierarchical control flow
regions, and by extension `LoopRegion`s. This forms the fourth core
element of the [plan to make loops first class citizens of
SDFGs](https://github.com/orgs/spcl/projects/10) and marks the last
element in the architecture.

By extending codegen with the capability of handling hierarchical
control flow graphs and SDFGs, a myriad of complexities that come with
control flow detection are circumvented, which currently lead to
significant issues for certain SDFGs (e.g., #635 and #1586). Making use
of control flow regions such as `LoopRegion`s instead allows codegen to
be much less 'smart' and behave more akin to a lookup table that decides
what code to generate for what SDFG element, making it significantly
less error prone.

dace/codegen/codegen.py

@@ -1,12 +1,11 @@
 # Copyright 2019-2021 ETH Zurich and the DaCe authors. All rights reserved.
 import functools
-import os
-from typing import List, Set
+from typing import List
 
 import dace
 from dace import dtypes
 from dace import data
-from dace.sdfg import SDFG, utils as sdutils
+from dace.sdfg import SDFG
 from dace.codegen.targets import framecode
 from dace.codegen.codeobject import CodeObject
 from dace.config import Config
@@ -95,7 +94,7 @@ def _get_codegen_targets(sdfg: SDFG, frame: framecode.DaCeCodeGenerator):
     for node, parent in sdfg.all_nodes_recursive():
         # Query nodes and scopes
         if isinstance(node, SDFGState):
-            frame.targets.add(disp.get_state_dispatcher(parent, node))
+            frame.targets.add(disp.get_state_dispatcher(node.sdfg, node))
         elif isinstance(node, dace.nodes.EntryNode):
             frame.targets.add(disp.get_scope_dispatcher(node.schedule))
         elif isinstance(node, dace.nodes.Node):
@@ -149,7 +148,7 @@ def _get_codegen_targets(sdfg: SDFG, frame: framecode.DaCeCodeGenerator):
         disp.instrumentation[sdfg.instrument] = provider_mapping[sdfg.instrument]
 
 
-def generate_code(sdfg, validate=True) -> List[CodeObject]:
+def generate_code(sdfg: SDFG, validate=True) -> List[CodeObject]:
     """
     Generates code as a list of code objects for a given SDFG.
 
@@ -186,11 +185,6 @@ def generate_code(sdfg, validate=True) -> List[CodeObject]:
                 shutil.move(f'{tmp_dir}/test2.sdfg', 'test2.sdfg')
                 raise RuntimeError(f'SDFG serialization failed - files do not match:\n{diff}')
 
-    # Convert any loop constructs with hierarchical loop regions into simple 1-level state machine loops.
-    # TODO (later): Adapt codegen to deal with hierarchical CFGs instead.
-    sdutils.inline_loop_blocks(sdfg)
-    sdutils.inline_control_flow_regions(sdfg)
-
     # Before generating the code, run type inference on the SDFG connectors
     infer_types.infer_connector_types(sdfg)