Reuse state names for function parameters; restart UsedNames.

Gives us a few more opportunities for catching single-letter identifiers.

UsedNames was not restarted. It's unlikely that this had any detrimental effect on optimization, and it was certainly safe to not restart it. But it looks more correct like this.

lslopt/lslrenamer.py

@@ -30,10 +30,10 @@ class renamer(object):
     CharSet1 = '_ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'
     CharSet2 = '0123456789_ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'
     # TODO: Derive these from builtins.txt somehow.
-    Kws = (frozenset({'do', 'if', 'PI',
-                      'for', 'key', 'EOF',
-                      'jump', 'else', 'list', 'TRUE', 'LOOP', 'case'
-                     }))
+    Kws = frozenset({'do', 'if', 'PI',
+                     'for', 'key', 'EOF',
+                     'jump', 'else', 'list', 'TRUE', 'LOOP', 'case'
+                     })
     def GetNextShortest(self):
         """Generate the next shortest possible identifier"""
         while True:
@@ -89,8 +89,11 @@ class renamer(object):
                 assert False, 'Invalid kind at this scope: ' \
                     + kind # pragma: no cover
 
-        # We make three passes, one for states, then functions, then globals,
-        # in that order.
+        # We make four passes, one for states, then functions, then globals,
+        # then parameter names and locals, in that order.
+
+        # State names are usable as short identifiers for parameters.
+        stateNames = []
 
         for name in states:
             # States have top priority. Here's why. An internal event function
@@ -111,6 +114,7 @@ class renamer(object):
             entry = globaldefs[name]
             if name != 'default':
                 name = entry['NewName'] = self.GetNextShortest()
+                stateNames.append(name)
             # Find also the event names it uses, to add them for reuse.
             for node in self.tree[entry['Loc']]['ch']:
                 assert node['nt'] == 'FNDEF'
@@ -159,6 +163,10 @@ class renamer(object):
         restart = self.WordFirstChar
         restartReusable = ReusableNames
         ReusableNames = restartReusable.copy()
+        restartState = stateNames;
+        stateNames = restartState[:]
+        restartUsed = self.UsedNames;
+        self.UsedNames = restartUsed.copy()
         for table in self.symtab:
             if First:
                 First = False
@@ -178,10 +186,16 @@ class renamer(object):
                         InParams = True
                         self.WordFirstChar = restart
                         ReusableNames = restartReusable.copy()
+                        stateNames = restartState[:]
+                        self.UsedNames = restartUsed.copy()
                     # Same procedure as for global vars
                     if ReusableNames:
                         short = ReusableNames.pop()
                         self.UsedNames.add(short)
+                    elif stateNames:
+                        short = stateNames.pop()
+                        # No need to add it to UsedNames because
+                        # GetNextShortest will always start past it anyway.
                     else:
                         short = self.GetNextShortest()
                     table[name]['NewName'] = short