On Mon, 20 Jul 2015, Kyrill Tkachov wrote:
> Hi all,
>
> This patch fixes the PR in question which is a miscompilation of
> gcc.dg/fixed-point/unary.c on arm.
> It just restricts the A - B -> A + (-B) transformation when the type is
> fixed-point.
>
> This fixes the testcase for me.
> Is this the right approach?
>
> Bootstrap and test on arm and x86 running.
>
> Ok if testing is clean?
Ok, but I think the fold-const.c code has the same issue, no:
/* A - B -> A + (-B) if B is easily negatable. */
if (negate_expr_p (arg1)
&& !TYPE_OVERFLOW_SANITIZED (type)
&& ((FLOAT_TYPE_P (type)
/* Avoid this transformation if B is a positive REAL_CST.
*/
&& (TREE_CODE (arg1) != REAL_CST
|| REAL_VALUE_NEGATIVE (TREE_REAL_CST (arg1))))
|| INTEGRAL_TYPE_P (type)))
return fold_build2_loc (loc, PLUS_EXPR, type,
fold_convert_loc (loc, type, arg0),
fold_convert_loc (loc, type,
negate_expr (arg1)));
ah, no. The above only applies to float-type and integral-types.
Thus yes, your patch is ok. Can you double-check the other pattern,
/* -(A + B) -> (-B) - A. */
(simplify
(negate (plus:c @0 negate_expr_p@1))
(if (!HONOR_SIGN_DEPENDENT_ROUNDING (element_mode (type))
&& !HONOR_SIGNED_ZEROS (element_mode (type)))
(minus (negate @1) @0)))
?
Thanks,
Richard.
> Thanks,
> Kyrill
>
>
> 2015-07-20 Kyrylo Tkachov <kyrylo.tkac...@arm.com>
>
> PR middle-end/66915
> * match.pd (A - B -> A + (-B)): Don't allow folding
> when type if a fixed-point type.
>
--
Richard Biener <rguent...@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Dilip Upmanyu, Graham
Norton, HRB 21284 (AG Nuernberg)
