[PATCH] Improve restrict handling further

[Richard Biener]

The following fixes

int
f5 (S *__restrict x, S *__restrict y)
{
  x->p[0] = 5;
  y->p[0] = 0;
// { dg-final { scan-tree-dump-times "return 5" 1 "optimized" { xfail 
*-*-* } } }
  return x->p[0];
}

which requires building representatives for restrict qualified pointers
(as opposed to references or decl-by-references).  The fear here was
that as we can access that representative with out-of-bound objects
(we eventually point to an array) we'd miscompute points-to sets.
I verified we do the obvious thing here, namely glob those accesses
to the first/last subfield of the representative (that code was added
to compensate for pointer arithmetic going ouf-of-bounds).

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

Richard.

2015-09-23  Richard Biener  <rguent...@suse.de>

        * tree-ssa-structalias.c (intra_create_variable_infos): Build
        representatives for all restrict qualified pointer destinations.

        * g++.dg/tree-ssa/restrict2.C: Un-XFAIL testcase.

Index: gcc/tree-ssa-structalias.c
===================================================================
*** gcc/tree-ssa-structalias.c  (revision 228014)
--- gcc/tree-ssa-structalias.c  (working copy)
*************** intra_create_variable_infos (struct func
*** 5854,5865 ****
      {
        varinfo_t p = get_vi_for_tree (t);
  
!       /* For restrict qualified pointers to objects passed by
!          reference build a real representative for the pointed-to object.
!        Treat restrict qualified references the same.  */
!       if (TYPE_RESTRICT (TREE_TYPE (t))
!         && ((DECL_BY_REFERENCE (t) && POINTER_TYPE_P (TREE_TYPE (t)))
!             || TREE_CODE (TREE_TYPE (t)) == REFERENCE_TYPE)
          && !type_contains_placeholder_p (TREE_TYPE (TREE_TYPE (t))))
        {
          struct constraint_expr lhsc, rhsc;
--- 5854,5865 ----
      {
        varinfo_t p = get_vi_for_tree (t);
  
!       /* For restrict qualified pointers build a representative for
!        the pointed-to object.  Note that this ends up handling
!        out-of-bound references conservatively by aggregating them
!        in the first/last subfield of the object.  */
!       if (POINTER_TYPE_P (TREE_TYPE (t))
!         && TYPE_RESTRICT (TREE_TYPE (t))
          && !type_contains_placeholder_p (TREE_TYPE (TREE_TYPE (t))))
        {
          struct constraint_expr lhsc, rhsc;
Index: gcc/testsuite/g++.dg/tree-ssa/restrict2.C
===================================================================
*** gcc/testsuite/g++.dg/tree-ssa/restrict2.C   (revision 228014)
--- gcc/testsuite/g++.dg/tree-ssa/restrict2.C   (working copy)
*************** f5 (S *__restrict x, S *__restrict y)
*** 45,52 ****
  {
    x->p[0] = 5;
    y->p[0] = 0;
! // We might handle this some day
! // { dg-final { scan-tree-dump-times "return 5" 1 "optimized" { xfail *-*-* } 
} }
    return x->p[0];
  }
  
--- 45,51 ----
  {
    x->p[0] = 5;
    y->p[0] = 0;
! // { dg-final { scan-tree-dump-times "return 5" 1 "optimized" } }
    return x->p[0];
  }