[PATCH][alias-improvements] Fix DOM store value-numbering

[Richard Guenther <rguenther at suse dot de>]

This fixes the store value-numbering of DOM - it relies on
create_ssa_artificial_load_stmt to put on the same virtual operand
SSA name as on the other stmt - at the initial alias rewrite I broke that.
Fixed thusly.

In refs_may_alias_p we may disambiguate references to distinct types
in case their bases do not conflict.  This fixes one piece of the
pr27799.c testsuite fail.

Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to the 
branch.

Richard.

2009-01-04  Richard Guenther  <rguenther@suse.de>

	* tree-dfa.c (refs_may_alias_p): Disambiguate using alias
	sets of the bases.
	* tree-ssa-operands.c (create_ssa_artificial_load_stmt): Add
	the virtual operand in SSA form.

Index: gcc/tree-dfa.c
===================================================================
*** gcc/tree-dfa.c	(revision 143048)
--- gcc/tree-dfa.c	(working copy)
*************** refs_may_alias_p (tree ref1, tree ref2)
*** 1049,1054 ****
--- 1049,1060 ----
  			      TREE_OPERAND (base2, 0), 0)))
      return ranges_overlap_p (offset1, max_size1, offset2, max_size2);
  
+   /* If the base objects do not conflict, references based on them
+      cannot either.  */
+   if (strict_aliasing_applies
+       && !alias_sets_conflict_p (get_alias_set (base1), get_alias_set (base2)))
+     return false;
+ 
    /* If both are component references through pointers try to find a
       common base and apply offset based disambiguation.  This handles
       for example
*************** refs_may_alias_p (tree ref1, tree ref2)
*** 1093,1101 ****
  	  offset1 -= offadj;
  	  return ranges_overlap_p (offset1, max_size1, offset2, max_size2);
  	}
-       /* If we can be sure to catch all equivalent types in the search
- 	 for the common base then we could return false here.  In that
- 	 case we would be able to disambiguate q->i and p->k.  */
      }
  
    return true;
--- 1099,1104 ----
Index: gcc/tree-ssa-operands.c
===================================================================
*** gcc/tree-ssa-operands.c	(revision 143048)
--- gcc/tree-ssa-operands.c	(working copy)
*************** create_ssa_artificial_load_stmt (gimple 
*** 1774,1782 ****
    bitmap_clear (build_stores);
  
    /* For each VDEF on the original statement, we want to create a
!      VUSE of the VDEF result operand on the new statement.  */
    FOR_EACH_SSA_TREE_OPERAND (op, old_stmt, iter, SSA_OP_VDEF)
!     append_vuse ();
  
    finalize_ssa_stmt_operands (new_stmt);
  
--- 1774,1783 ----
    bitmap_clear (build_stores);
  
    /* For each VDEF on the original statement, we want to create a
!      VUSE of the VDEF result operand on the new statement.
!      ???  All this function can be simplified very much.  */
    FOR_EACH_SSA_TREE_OPERAND (op, old_stmt, iter, SSA_OP_VDEF)
!     VEC_safe_push (tree, heap, build_vuses, op);
  
    finalize_ssa_stmt_operands (new_stmt);