# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1267143961 -3600
# Node ID 72af990b63cfcede9d32547dbeb1e8faa7912972
# Parent  1686ed14e71328204797a2386df8fe8e4eca0e63
Introduced loop nodes as attribute users tracking attribute usage.

diff -r 1686ed14e713 -r 72af990b63cf micropython/data.py
--- a/micropython/data.py	Thu Feb 25 01:22:21 2010 +0100
+++ b/micropython/data.py	Fri Feb 26 01:26:01 2010 +0100
@@ -135,6 +135,7 @@
 
         self.attribute_users = [{}] # stack of assignments
         self.user_shelves = []
+        self.loop_users = [{}]      # stack of loop nodes
 
         # Define attribute usage to identify active program sections.
 
@@ -330,13 +331,17 @@
         with the given 'attrname'.
         """
 
+        for users in (self.attribute_users[-1], self.loop_users[-1]):
+
+            # Add the usage to all current users.
+
+            if users.has_key(name):
+                for user in users[name]:
+                    user._attrnames[name].add(attrname)
+
         users = self.attribute_users[-1]
 
-        # Add the usage to all current users.
-
         if users.has_key(name):
-            for user in users[name]:
-                user._attrnames[name].add(attrname)
             return users[name]
         else:
             return []
@@ -363,15 +368,30 @@
 
         # Record the attribute combinations for the name.
 
+        self._init_attribute_user_for_name(node, name)
+
+        # Propagate any loop usage forward to any redefinition of a name.
+
+        loop_users = self.loop_users[-1]
+
+        if loop_users.has_key(name):
+            for loop_user in loop_users[name]:
+                node._attrnames[name].update(loop_user._attrnames[name])
+            del loop_users[name]
+
+        # Remember this user.
+
+        self.all_attribute_users.add(node)
+
+    def _init_attribute_user_for_name(self, node, name):
+
+        "Make sure that 'node' is initialised for 'name'."
+
         if not hasattr(node, "_attrnames"):
             node._attrnames = {}
 
         node._attrnames[name] = set()
 
-        # Remember this user.
-
-        self.all_attribute_users.add(node)
-
     def _new_branchpoint(self):
 
         """
@@ -381,11 +401,14 @@
 
         self.user_shelves.append([])
 
-    def _new_branch(self):
+    def _new_branch(self, loop_node=None):
 
         """
         Establish a new control-flow branch, transferring attribute usage to
         the new branch so that it may be augmented for each name locally.
+
+        If the optional 'loop_node' is given, add it as an active user to be
+        informed of attribute usage.
         """
 
         # Retain a record of active users.
@@ -394,6 +417,21 @@
         d.update(self.attribute_users[-1])
         self.attribute_users.append(d)
 
+        new_users = self.attribute_users[-1]
+
+        d = {}
+        d.update(self.loop_users[-1])
+
+        if loop_node is not None:
+            for name, nodes in new_users.items():
+                if not d.has_key(name):
+                    d[name] = set([loop_node])
+                else:
+                    d[name] = d[name].union([loop_node])
+                self._init_attribute_user_for_name(loop_node, name)
+
+        self.loop_users.append(d)
+
     def _abandon_branch(self):
         pass
 
diff -r 1686ed14e713 -r 72af990b63cf micropython/inspect.py
--- a/micropython/inspect.py	Thu Feb 25 01:22:21 2010 +0100
+++ b/micropython/inspect.py	Fri Feb 26 01:26:01 2010 +0100
@@ -329,8 +329,8 @@
     def new_branchpoint(self):
         self.get_namespace()._new_branchpoint()
 
-    def new_branch(self):
-        self.get_namespace()._new_branch()
+    def new_branch(self, loop_node=None):
+        self.get_namespace()._new_branch(loop_node)
 
     def abandon_branch(self):
         self.get_namespace()._abandon_branch()
@@ -960,13 +960,14 @@
 
         self.in_loop = 1
         self.dispatch(node.test)
-        self.new_branch()
+        self.new_branch(node)
         self.dispatch(node.body)
         self.shelve_branch()
         self.in_loop = 0
 
         # Maintain a branch for the else clause or the current retained usage
         # where execution avoids the conditional clauses.
+        # NOTE: Consider merging here before the else clause.
 
         self.new_branch()
         if node.else_ is not None: