[PATCH] Handle &__restrict parameters in tree-ssa-structalias.c like DECL_BY_REFERENCE parameters

[Richard Guenther]

On Fri, Sep 23, 2011 at 7:06 PM, Jakub Jelinek <jakub@redhat.com> wrote:
> Hi!
>
> This simple patch improves the f3 function in the testcase below,
> a parameter with TYPE_RESTRICT REFERENCE_TYPE IMHO can be safely treated
> like the DECL_BY_REFERENCE case where the source actually didn't contain
> a reference, but compiler created it anyway.  If source contains &__restrict
> parameter, the parameter again points to a chunk of (for the function
> global) restrict memory that nothing inside of the function should access
> otherwise than through this parameter or pointers derived from it.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
>
> 2011-09-23  Jakub Jelinek  <jakub@redhat.com>
>
>        * tree-ssa-structalias.c (intra_create_variable_infos): Treat
>        TYPE_RESTRICT REFERENCE_TYPE parameters like restricted
>        DECL_BY_REFERENCE parameters.
>
>        * g++.dg/tree-ssa/restrict2.C: New test.
>
> --- gcc/tree-ssa-structalias.c.jj       2011-09-15 12:18:37.000000000 +0200
> +++ gcc/tree-ssa-structalias.c  2011-09-23 15:36:23.000000000 +0200
> @@ -5589,10 +5589,11 @@ intra_create_variable_infos (void)
>       varinfo_t p;
>
>       /* For restrict qualified pointers to objects passed by
> -         reference build a real representative for the pointed-to object.  */
> -      if (DECL_BY_REFERENCE (t)
> -         && POINTER_TYPE_P (TREE_TYPE (t))
> -         && TYPE_RESTRICT (TREE_TYPE (t)))
> +         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))
>        {
>          struct constraint_expr lhsc, rhsc;
>          varinfo_t vi;

I don't see why

  f4 (s, s)

would be invalid.  But you would miscompile it.
(I'm not sure that a restrict qualified component is properly defined
by the C standard - we're just making this extension in a very constrained
case to allow Fortran array descriptors to work).

Richard.

> +
> +int
> +f2 (S x)
> +{
> +  x.p[0] = 2;
> +  s.p[0] = 0;
> +// { dg-final { scan-tree-dump-times "return 2" 1 "optimized" } }
> +  return x.p[0];
> +}
> +
> +int
> +f3 (S &__restrict x, S &__restrict y)
> +{
> +  x.p[0] = 3;
> +  y.p[0] = 0;
> +// { dg-final { scan-tree-dump-times "return 3" 1 "optimized" } }
> +  return x.p[0];
> +}
> +
> +int
> +f4 (S &x, S &y)
> +{
> +  x.p[0] = 4;
> +  y.p[0] = 0;
> +// { dg-final { scan-tree-dump-times "return 4" 0 "optimized" } }
> +  return x.p[0];
> +}
> +
> +int
> +f5 (S *__restrict x, S *__restrict y)
> +{
> +  x->p[0] = 5;
> +  y->p[0] = 0;
> +// We might handle this some day
> +// { dg-final { scan-tree-dump-times "return 5" 0 "optimized" } }
> +  return x->p[0];
> +}
> +
> +int
> +f6 (S *x, S *y)
> +{
> +  x->p[0] = 6;
> +  y->p[0] = 0;
> +// { dg-final { scan-tree-dump-times "return 6" 0 "optimized" } }
> +  return x->p[0];
> +}
> +
> +// { dg-final { cleanup-tree-dump "optimized" } }
>
>        Jakub
>