[myhdl-list] [RFC/PATCH] always_comb: include signals from attributes in sensitivity list

[Sébastien B. <seb...@mi...>]

Using always_comb with an instance that reads signals from a class does not work (not even in simulation) because those signals do not get included in the sensitivity list. The proposed patch below fixes this problem for the simulation.

Example/test code:
https://github.com/sbourdeauducq/TokenEngine/blob/master/myhdl-limits/slclass.py

Correct result:
Setting object signal to False
Value outside object: False
Setting object signal to True
Value outside object: True

Incorrect result (currently what MyHDL does without the patch):
Setting object signal to False
Value outside object: False
Setting object signal to True
Value outside object: False
                      ^^^^^

diff -r e18493b5f0ad myhdl/_always_comb.py
--- a/myhdl/_always_comb.py	Fri May 20 21:07:24 2011 +0200
+++ b/myhdl/_always_comb.py	Mon Sep 12 17:06:06 2011 +0200
@@ -76,6 +75,7 @@
         self.toplevel = 1
         self.symdict = symdict
         self.context = INPUT
+        self.attrs = []
 
     def visit_Module(self, node):
         inputs = self.inputs
@@ -106,15 +106,27 @@
         if id not in self.symdict:
             return
         s = self.symdict[id]
-        if isinstance(s, _Signal) or _isListOfSigs(s):
-            if self.context == INPUT:
-                self.inputs.add(id)
-            elif self.context == OUTPUT:
-                self.outputs.add(id)
-            elif self.context == INOUT:
-                raise AlwaysCombError(_error.SignalAsInout % id)
-            else:
-                raise AssertionError("bug in always_comb")
+        ia = iter(self.attrs)
+        while True:
+            if isinstance(s, _Signal) or _isListOfSigs(s):
+                if self.context == INPUT:
+                    self.inputs.add(id)
+                    self.symdict[id] = s
+                    break
+                elif self.context == OUTPUT:
+                    self.outputs.add(id)
+                    self.symdict[id] = s
+                    break
+                elif self.context == INOUT:
+                    raise AlwaysCombError(_error.SignalAsInout % id)
+                else:
+                    raise AssertionError("bug in always_comb")
+            try:
+                a = ia.next()
+            except StopIteration:
+                break
+            id += "." + a
+            s = getattr(s, a)
             
     def visit_Assign(self, node):
         self.context = OUTPUT
@@ -124,7 +136,9 @@
         self.visit(node.value)
 
     def visit_Attribute(self, node):
+        self.attrs.insert(0, node.attr)
         self.visit(node.value)
+        self.attrs.pop(0)
 
     def visit_Subscript(self, node, access=INPUT):
         self.visit(node.value)