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Re: [PATCH] i386: Do not align small stack slots to 16 bytes
- From: Uros Bizjak <ubizjak at gmail dot com>
- To: Segher Boessenkool <segher at kernel dot crashing dot org>
- Cc: "gcc-patches at gcc dot gnu dot org" <gcc-patches at gcc dot gnu dot org>, Shmuel Hanoch <shmuel at infinitylabs dot co dot il>
- Date: Tue, 7 Mar 2017 08:23:17 +0100
- Subject: Re: [PATCH] i386: Do not align small stack slots to 16 bytes
- Authentication-results: sourceware.org; auth=none
- References: <7d76131e803aad99c6252fe73eaed43e80ffed40.1488759797.git.segher@kernel.crashing.org>
On Mon, Mar 6, 2017 at 6:51 PM, Segher Boessenkool
<segher@kernel.crashing.org> wrote:
> As Shmuel reported in <https://gcc.gnu.org/ml/gcc-help/2017-03/msg00009.html>,
> on x86-64 small structures in automatic storage are aligned to 16 bytes.
> This seems to be because of a mix-up between bits and bytes in the i386
> target code.
>
> Is this okay for trunk?
>
>
> Segher
>
>
> 2017-03-06 Segher Boessenkool <segher@kernel.crashing.org>
>
> * gcc/config/i386/i386.c (ix86_local_alignment): Align most aggregates
> of 16 bytes and more to 16 bytes, not those of 16 bits and more.
OK for trunk and backports.
Thanks,
Uros.
> ---
> gcc/config/i386/i386.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
> index 754c016..f03e71a 100644
> --- a/gcc/config/i386/i386.c
> +++ b/gcc/config/i386/i386.c
> @@ -30467,7 +30467,7 @@ ix86_local_alignment (tree exp, machine_mode mode,
> != TYPE_MAIN_VARIANT (va_list_type_node)))
> && TYPE_SIZE (type)
> && TREE_CODE (TYPE_SIZE (type)) == INTEGER_CST
> - && wi::geu_p (TYPE_SIZE (type), 16)
> + && wi::geu_p (TYPE_SIZE (type), 128)
> && align < 128)
> return 128;
> }
> --
> 1.9.3
>