[pypy-svn] r70246 - pypy/trunk/pypy/jit/metainterp

[arigo at codespeak.net]

Author: arigo
Date: Tue Dec 22 13:47:02 2009
New Revision: 70246

Modified:
   pypy/trunk/pypy/jit/metainterp/resume.py
Log:
Use the most negative value for UNASSIGNED values, instead of a random
negative value.  Add a longish comment and an assert to explain why any
negative value would actually be fine.


Modified: pypy/trunk/pypy/jit/metainterp/resume.py
==============================================================================
--- pypy/trunk/pypy/jit/metainterp/resume.py	(original)
+++ pypy/trunk/pypy/jit/metainterp/resume.py	Tue Dec 22 13:47:02 2009
@@ -93,8 +93,8 @@
 TAGBOX      = 2
 TAGVIRTUAL  = 3
 
-UNASSIGNED = tag(-2 ** 12 - 1, TAGBOX)
-UNASSIGNEDVIRTUAL = tag(-2 ** 12 - 1, TAGVIRTUAL)
+UNASSIGNED = tag(-1<<13, TAGBOX)
+UNASSIGNEDVIRTUAL = tag(-1<<13, TAGVIRTUAL)
 NULLREF = tag(-1, TAGCONST)
 
 
@@ -301,6 +301,11 @@
         memo = self.memo
         new_liveboxes = [None] * memo.num_cached_boxes()
         count = 0
+        # So far, self.liveboxes should contain 'tagged' values that are
+        # either UNASSIGNED, UNASSIGNEDVIRTUAL, or a *non-negative* value
+        # with the TAGVIRTUAL.  The following loop removes the UNASSIGNED
+        # and UNASSIGNEDVIRTUAL entries, and replaces them with real
+        # negative values.
         for box, tagged in self.liveboxes.iteritems():
             i, tagbits = untag(tagged)
             if tagbits == TAGBOX:
@@ -315,6 +320,8 @@
                     assert box not in self.liveboxes_from_env
                     index = memo.assign_number_to_virtual(box)
                     self.liveboxes[box] = tag(index, TAGVIRTUAL)
+                else:
+                    assert i >= 0
         new_liveboxes.reverse()
         liveboxes.extend(new_liveboxes)
         nholes = len(new_liveboxes) - count