alias.c (rtx_refs_may_alias_p): Do not resort to TBAA if either alias-set is zero.

2010-08-04  Richard Guenther  <rguenther@suse.de>

	* alias.c (rtx_refs_may_alias_p): Do not resort to TBAA
	if either alias-set is zero.

From-SVN: r162867

gcc/ChangeLog

 2010-08-04  Richard Guenther  <rguenther@suse.de>
 
+	* alias.c (rtx_refs_may_alias_p): Do not resort to TBAA
+	if either alias-set is zero.
+
+2010-08-04  Richard Guenther  <rguenther@suse.de>
+
 	* tree-ssa-propagate.h (struct prop_value_d, prop_value_t): Move ...
 	* tree-ssa-ccp.c: ... here.
 	* tree-ssa-copy.c: ... and here.

gcc/alias.c

@@ -354,7 +354,10 @@ rtx_refs_may_alias_p (const_rtx x, const_rtx mem, bool tbaa_p)
       || !ao_ref_from_mem (&ref2, mem))
     return true;
 
-  return refs_may_alias_p_1 (&ref1, &ref2, tbaa_p);
+  return refs_may_alias_p_1 (&ref1, &ref2,
+			     tbaa_p
+			     && MEM_ALIAS_SET (x) != 0
+			     && MEM_ALIAS_SET (mem) != 0);
 }
 
 /* Returns a pointer to the alias set entry for ALIAS_SET, if there is