[RFC] Enable saliasing for structs with arrays

[Richard Guenther]

This simple patch enables structure aliasing for structs containing
arrays (_not_ enabling subvars for the arrays).  Unfortunately, the
patch breaks bootstrap due to IVOPTs and friends.  This is sad, as
it may even help for better alias analysis for GCCs tree structure.

Maybe some IVOPTs folks can help out here.

Richard.


2005-07-19  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/22555
	* tree-ssa-alias.c (create_overlap_variables_for): Do not
	give up, if one structure field is an array.
	* tree-ssa-structalias.c (create_variable_info_for): Likewise.

	* gcc.dg/tree-ssa/alias-3.c: New testcase.


Index: tree-ssa-alias.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/tree-ssa-alias.c,v
retrieving revision 2.104
diff -c -3 -p -r2.104 tree-ssa-alias.c
*** tree-ssa-alias.c	16 Jul 2005 18:56:52 -0000	2.104
--- tree-ssa-alias.c	19 Jul 2005 09:00:54 -0000
*************** create_overlap_variables_for (tree var)
*** 2532,2538 ****
  	{
  	  if (!DECL_SIZE (fo->field) 
  	      || TREE_CODE (DECL_SIZE (fo->field)) != INTEGER_CST
- 	      || TREE_CODE (TREE_TYPE (fo->field)) == ARRAY_TYPE
  	      || fo->offset < 0)
  	    {
  	      notokay = true;
--- 2532,2537 ----
Index: tree-ssa-structalias.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/tree-ssa-structalias.c,v
retrieving revision 2.21
diff -c -3 -p -r2.21 tree-ssa-structalias.c
*** tree-ssa-structalias.c	16 Jul 2005 22:27:21 -0000	2.21
--- tree-ssa-structalias.c	19 Jul 2005 09:00:54 -0000
*************** create_variable_info_for (tree decl, con
*** 3017,3023 ****
    vi->has_union = hasunion;
    if (!TYPE_SIZE (decltype) 
        || TREE_CODE (TYPE_SIZE (decltype)) != INTEGER_CST
-       || TREE_CODE (decltype) == ARRAY_TYPE
        || TREE_CODE (decltype) == UNION_TYPE
        || TREE_CODE (decltype) == QUAL_UNION_TYPE)
      {
--- 3017,3022 ----
*************** create_variable_info_for (tree decl, con
*** 3051,3057 ****
  	{
  	  if (!DECL_SIZE (fo->field) 
  	      || TREE_CODE (DECL_SIZE (fo->field)) != INTEGER_CST
- 	      || TREE_CODE (TREE_TYPE (fo->field)) == ARRAY_TYPE
  	      || fo->offset < 0)
  	    {
  	      notokay = true;
--- 3050,3055 ----


/* { dg-do compile } */
/* { dg-options "-O2 -fdump-tree-vars" } */

struct {
	int i;
	int j;
	int x[2];
} a;

int foo(void)
{
	a.i = 1;
	a.j = 0;
	a.x[0] = 0;
	return a.i + a.j;
}

/* { dg-final { scan-tree-dump "return 1;" "vars" } } */
/* { dg-final { cleanup-tree-dump "vars" } } */