Fix max_decode_depth to control decoder hierarchy and port generation (#18)

* Initial plan

* Fix max_decode_depth to properly control decoder hierarchy and port generation

Co-authored-by: arnavsacheti <36746504+arnavsacheti@users.noreply.github.com>

* Fix test that relied on old depth behavior

Co-authored-by: arnavsacheti <36746504+arnavsacheti@users.noreply.github.com>

* Update documentation for max_decode_depth parameter

Co-authored-by: arnavsacheti <36746504+arnavsacheti@users.noreply.github.com>

* fix format

* Add variable_depth RDL file and smoke tests for max_decode_depth parameter

Co-authored-by: arnavsacheti <36746504+arnavsacheti@users.noreply.github.com>

* Add variable depth tests for APB3 and AXI4-Lite CPUIFs

Co-authored-by: arnavsacheti <36746504+arnavsacheti@users.noreply.github.com>

* fix

* fix

* bump

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: arnavsacheti <36746504+arnavsacheti@users.noreply.github.com>

src/peakrdl_busdecoder/cpuif/base_cpuif.py

@@ -25,11 +25,7 @@ class BaseCpuif:
 
     @property
     def addressable_children(self) -> list[AddressableNode]:
-        return [
-            child
-            for child in self.exp.ds.top_node.children(unroll=self.unroll)
-            if isinstance(child, AddressableNode)
-        ]
+        return self.exp.ds.get_addressable_children_at_depth(unroll=self.unroll)
 
     @property
     def addr_width(self) -> int:

src/peakrdl_busdecoder/cpuif/fanin_gen.py

@@ -27,6 +27,17 @@ class FaninGenerator(BusDecoderListener):
     def enter_AddressableComponent(self, node: AddressableNode) -> WalkerAction | None:
         action = super().enter_AddressableComponent(node)
 
+        should_generate = action == WalkerAction.SkipDescendants
+        if not should_generate and self._ds.max_decode_depth == 0:
+            for child in node.children():
+                if isinstance(child, AddressableNode):
+                    break
+            else:
+                should_generate = True
+
+        if not should_generate:
+            return action
+
         if node.array_dimensions:
             for i, dim in enumerate(node.array_dimensions):
                 fb = ForLoopBody(

src/peakrdl_busdecoder/cpuif/fanout_gen.py

@@ -23,6 +23,17 @@ class FanoutGenerator(BusDecoderListener):
     def enter_AddressableComponent(self, node: AddressableNode) -> WalkerAction | None:
         action = super().enter_AddressableComponent(node)
 
+        should_generate = action == WalkerAction.SkipDescendants
+        if not should_generate and self._ds.max_decode_depth == 0:
+            for child in node.children():
+                if isinstance(child, AddressableNode):
+                    break
+            else:
+                should_generate = True
+
+        if not should_generate:
+            return action
+
         if node.array_dimensions:
             for i, dim in enumerate(node.array_dimensions):
                 fb = ForLoopBody(