1to1 fork optimization, fix substitute

src/kyupy/circuit.py

@@ -314,6 +314,28 @@ class Circuit:
     def get_or_add_fork(self, name):
         return self.forks[name] if name in self.forks else Node(self, name)
 
+    def eliminate_1to1_forks(self):
+        """Removes all forks that drive only one node.
+
+        Such forks are inserted by parsers to annotate signal names. If this
+        information is not needed, such forks can be removed and the two neighbors
+        can be connected directly using one line. Forks that drive more than one node
+        are not removed by this function.
+        """
+        ios = set(self.io_nodes)
+        for n in list(self.forks.values()):
+            if n in ios: continue
+            if len(n.outs) != 1: continue
+            in_line = n.ins[0]
+            out_line = n.outs[0]
+            out_reader = out_line.reader
+            out_reader_pin = out_line.reader_pin
+            n.remove()
+            out_line.remove()
+            in_line.reader = out_reader
+            in_line.reader_pin = out_reader_pin
+            in_line.reader.ins[in_line.reader_pin] = in_line
+
     def substitute(self, node, impl):
         """Replaces a given node with the given implementation circuit.
 
@@ -321,10 +343,10 @@ class Circuit:
         the signal lines are connected appropriately. The number and arrangement
         of the input and output ports must match the pins of the replaced node.
         """
-        node_in_lines = [l for l in node.ins if l]
-        node_out_lines = [l for l in node.outs if l]
         impl_in_lines = [n.outs[0] for n in impl.io_nodes if len(n.outs) > 0]
         impl_out_lines = [n.ins[0] for n in impl.io_nodes if len(n.ins) > 0]
+        node_in_lines = list(node.ins) + [None] * (len(impl_in_lines)-len(node.ins))
+        node_out_lines = list(node.outs) + [None] * (len(impl_out_lines)-len(node.outs))
         assert len(node_in_lines) == len(impl_in_lines)
         assert len(node_out_lines) == len(impl_out_lines)
         in_lines_map = dict(zip(impl_in_lines, node_in_lines))
@@ -338,11 +360,13 @@ class Circuit:
         for l in impl.lines:
             if l in in_lines_map:
                 ll = in_lines_map[l]
+                if ll is not None:
                     ll.reader = node_map[l.reader]
                     ll.reader_pin = l.reader_pin
                     ll.reader.ins[ll.reader_pin] = ll
             elif l in out_lines_map:
                 ll = out_lines_map[l]
+                if ll is not None:
                     ll.driver = node_map[l.driver]
                     ll.driver_pin = l.driver_pin
                     ll.driver.outs[ll.driver_pin] = ll