http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53090
--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #4)
> Sth like
>
> Index: gcc/c-family/c-common.c
> ===================================================================
> --- gcc/c-family/c-common.c (revision 209018)
> +++ gcc/c-family/c-common.c (working copy)
> @@ -4415,19 +4415,21 @@ pointer_int_sum (location_t loc, enum tr
>
> /* Convert the integer argument to a type the same size as sizetype
> so the multiply won't overflow spuriously. */
> + enum tree_code code = MULT_EXPR;
> if (TYPE_PRECISION (TREE_TYPE (intop)) != TYPE_PRECISION (sizetype)
> || TYPE_UNSIGNED (TREE_TYPE (intop)) != TYPE_UNSIGNED (sizetype))
> - intop = convert (c_common_type_for_size (TYPE_PRECISION (sizetype),
> - TYPE_UNSIGNED (sizetype)),
> intop);
> + code = WIDEN_MULT_EXPR;
>
> /* Replace the integer argument with a suitable product by the object
> size.
> Do this multiplication as signed, then convert to the appropriate type
> for the pointer operation and disregard an overflow that occurred only
> because of the sign-extension change in the latter conversion. */
> {
> - tree t = build_binary_op (loc,
> - MULT_EXPR, intop,
> - convert (TREE_TYPE (intop), size_exp), 1);
> + tree t = fold_build2_loc (loc, code,
> + c_common_type_for_size (TYPE_PRECISION
> (sizetype),
> + TYPE_UNSIGNED
> (sizetype)),
> + intop,
> + convert (TREE_TYPE (intop), size_exp));
> intop = convert (sizetype, t);
> if (TREE_OVERFLOW_P (intop) && !TREE_OVERFLOW (t))
> intop = build_int_cst_wide (TREE_TYPE (intop), TREE_INT_CST_LOW
> (intop),
>
>
> but then you notice that for example SCEV doesn't handle WIDEN_MULT_EXPR.
But for example SCEV could be teached to _create_ the WIDEN_MULT_EXPRs
in the first place ... thus analyze for example _14 instead of as
(set_scalar_evolution
instantiated_below = 4
(scalar = _14)
(scalar_evolution = {perm_9(D) + (sizetype) ((long unsigned int) j_5 * 4), +,
18446744073709551612}_1))
as
(set_scalar_evolution
instantiated_below = 4
(scalar = _14)
(scalar_evolution = {perm_9(D) + (sizetype) (j_5 w* 4), +,
18446744073709551612}_1))
