On Fri, Aug 4, 2017 at 10:38 AM, Marek Polacek <pola...@redhat.com> wrote:
> We were crashing because size_binop_loc got operands of different types:
> sizetype and ssizetype. Richi suggested performing the computation in
> offset_int which my patch tries to do. Unsure about the sdiv_trunc part,
> what do I use instead of EXACT_DIV_EXPR?
Use wi::divmod_trunc and check for a zero remainder. If the remainder is not
zero we may not fold.
Ok with that change.
Thanks,
Richard.
> Bootstrapped/regtested on x86_64-linux, ok for trunk? Testing on ppc64le
> in progress.
>
> 2017-08-04 Marek Polacek <pola...@redhat.com>
>
> PR middle-end/81695
> * fold-const.c (fold_indirect_ref_1): For ((int *)&a + 4 -> a[1],
> perform the computation in offset_int.
>
> * gcc.dg/pr81695.c: New test.
>
> diff --git gcc/fold-const.c gcc/fold-const.c
> index ed6c289a64b..64a84eb0197 100644
> --- gcc/fold-const.c
> +++ gcc/fold-const.c
> @@ -14106,14 +14106,17 @@ fold_indirect_ref_1 (location_t loc, tree type,
> tree op0)
> && type == TREE_TYPE (op00type))
> {
> tree type_domain = TYPE_DOMAIN (op00type);
> - tree min_val = size_zero_node;
> - if (type_domain && TYPE_MIN_VALUE (type_domain))
> - min_val = TYPE_MIN_VALUE (type_domain);
> - op01 = size_binop_loc (loc, EXACT_DIV_EXPR, op01,
> - TYPE_SIZE_UNIT (type));
> - op01 = size_binop_loc (loc, PLUS_EXPR, op01, min_val);
> - return build4_loc (loc, ARRAY_REF, type, op00, op01,
> - NULL_TREE, NULL_TREE);
> + tree min = TYPE_MIN_VALUE (type_domain);
> + if (min && TREE_CODE (min) == INTEGER_CST)
> + {
> + offset_int off = wi::to_offset (op01);
> + offset_int el_sz = wi::to_offset (TYPE_SIZE_UNIT (type));
> + off = wi::sdiv_trunc (off, el_sz);
> + off = off + wi::to_offset (min);
> + op01 = wide_int_to_tree (sizetype, off);
> + return build4_loc (loc, ARRAY_REF, type, op00, op01,
> + NULL_TREE, NULL_TREE);
> + }
> }
> }
> }
> diff --git gcc/testsuite/gcc.dg/pr81695.c gcc/testsuite/gcc.dg/pr81695.c
> index e69de29bb2d..c3452580f1c 100644
> --- gcc/testsuite/gcc.dg/pr81695.c
> +++ gcc/testsuite/gcc.dg/pr81695.c
> @@ -0,0 +1,11 @@
> +/* PR middle-end/81695 */
> +/* { dg-do compile } */
> +/* { dg-options "" } */
> +
> +int z[] = { };
> +
> +int
> +main (void)
> +{
> + __builtin_printf ("%d\n", *(z + 1));
> +}
>
> Marek
