Re: Check array indices in object_address_invariant_in_loop_p (PR 84357)

[Richard Biener <richard dot guenther at gmail dot com>]

On Wed, Feb 14, 2018 at 10:44 AM, Richard Sandiford
<richard.sandiford@linaro.org> wrote:
> object_address_invariant_in_loop_p ignored ARRAY_REF indices on
> the basis that:
>
>           /* Index of the ARRAY_REF was zeroed in analyze_indices, thus we only
>              need to check the stride and the lower bound of the reference.  */
>
> That was true back in 2007 when the code was added:
>
> static void
> dr_analyze_indices (struct data_reference *dr, struct loop *nest)
> {
>   [...]
>   while (handled_component_p (aref))
>     {
>       if (TREE_CODE (aref) == ARRAY_REF)
>         {
>           op = TREE_OPERAND (aref, 1);
>           access_fn = analyze_scalar_evolution (loop, op);
>           access_fn = resolve_mixers (nest, access_fn);
>           VEC_safe_push (tree, heap, access_fns, access_fn);
>
>           TREE_OPERAND (aref, 1) = build_int_cst (TREE_TYPE (op), 0);
>         }
>
>       aref = TREE_OPERAND (aref, 0);
>     }
>
> but the assignment was removed a few years ago.

GCC 4.7!

>  We were therefore
> treating "two->arr[i]" and "three->arr[i]" as loop invariant.
>
> Tested on aarch64-linux-gnu, x86_64-linux-gnu and powerpc64le-linux-gnu.
> OK to install?

Ok.

Thanks,
Richard.

> Richard
>
>
> 2018-02-14  Richard Sandiford  <richard.sandiford@linaro.org>
>
> gcc/
>         PR tree-optimization/84357
>         * tree-data-ref.c (object_address_invariant_in_loop_p): Check
>         operand 1 of an ARRAY_REF too.
>
> gcc/testsuite/
>         PR tree-optimization/84357
>         * gcc.dg/vect/pr84357.c: New test.
>
> Index: gcc/tree-data-ref.c
> ===================================================================
> --- gcc/tree-data-ref.c 2018-02-08 15:16:21.784407397 +0000
> +++ gcc/tree-data-ref.c 2018-02-14 09:42:14.801095011 +0000
> @@ -2200,13 +2200,10 @@ object_address_invariant_in_loop_p (cons
>      {
>        if (TREE_CODE (obj) == ARRAY_REF)
>         {
> -         /* Index of the ARRAY_REF was zeroed in analyze_indices, thus we only
> -            need to check the stride and the lower bound of the reference.  */
> -         if (chrec_contains_symbols_defined_in_loop (TREE_OPERAND (obj, 2),
> -                                                     loop->num)
> -             || chrec_contains_symbols_defined_in_loop (TREE_OPERAND (obj, 3),
> -                                                        loop->num))
> -           return false;
> +         for (int i = 1; i < 4; ++i)
> +           if (chrec_contains_symbols_defined_in_loop (TREE_OPERAND (obj, i),
> +                                                       loop->num))
> +             return false;
>         }
>        else if (TREE_CODE (obj) == COMPONENT_REF)
>         {
> Index: gcc/testsuite/gcc.dg/vect/pr84357.c
> ===================================================================
> --- /dev/null   2018-02-10 09:05:46.714416790 +0000
> +++ gcc/testsuite/gcc.dg/vect/pr84357.c 2018-02-14 09:42:14.800095067 +0000
> @@ -0,0 +1,31 @@
> +/* { dg-do compile } */
> +/* { dg-additional-options "-Wall" } */
> +
> +#define COUNT 32
> +
> +typedef struct s1 {
> +    unsigned char c;
> +} s1;
> +
> +typedef struct s2
> +{
> +    char pad;
> +    s1 arr[COUNT];
> +} s2;
> +
> +typedef struct s3 {
> +    s1 arr[COUNT];
> +} s3;
> +
> +s2 * get_s2();
> +s3 * gActiveS3;
> +void foo()
> +{
> +    s3 * three = gActiveS3;
> +    s2 * two = get_s2();
> +
> +    for (int i = 0; i < COUNT; i++)
> +    {
> +        two->arr[i].c = three->arr[i].c;
> +    }
> +}