Re: [PATCH] vect: Don't retry if the previous analysis fails

[Richard Biener <richard.guenther@gmail.com>]

On Wed, May 17, 2023 at 8:06 AM Kewen.Lin <linkw@linux.ibm.com> wrote:
>
> Hi,
>
> When working on a cost tweaking patch, I found that a newly
> added test case has different dumpings with stage-1 and
> bootstrapped gcc.  By looking into it, the apparent reason
> is vect_analyze_loop_2 doesn't get slp_done_for_suggested_uf
> set expectedly, the following retrying will use the garbage
> slp_done_for_suggested_uf instead.  In fact, the setting of
> slp_done_for_suggested_uf only happens when the previous
> analysis succeeds, for the mentioned test case, its previous
> analysis does fail, it's unexpected to use the value of
> slp_done_for_suggested_uf any more.
>
> In function vect_analyze_loop_1, we only return success when
> res is true, which is the result of 1st analysis.  It means
> we never try to vectorize with unroll_vinfo if the previous
> analysis fails.  So this patch shouldn't break anything, and
> just stop some useless analysis early.
>
> Bootstrapped and regtested on x86_64-redhat-linux,
> aarch64-linux-gnu and powerpc64{,le}-linux-gnu.
>
> Is it ok for trunk?

OK for trunk and affected branches.

Richard.

> BR,
> Kewen
> -----
> gcc/ChangeLog:
>
>         * tree-vect-loop.cc (vect_analyze_loop_1): Don't retry analysis with
>         suggested unroll factor once the previous analysis fails.
> ---
>  gcc/tree-vect-loop.cc | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/gcc/tree-vect-loop.cc b/gcc/tree-vect-loop.cc
> index ed0166fedab..905145ae97b 100644
> --- a/gcc/tree-vect-loop.cc
> +++ b/gcc/tree-vect-loop.cc
> @@ -3044,7 +3044,7 @@ vect_analyze_loop_1 (class loop *loop, vec_info_shared *shared,
>                      res ? "succeeded" : " failed",
>                      GET_MODE_NAME (loop_vinfo->vector_mode));
>
> -  if (!main_loop_vinfo && suggested_unroll_factor > 1)
> +  if (res && !main_loop_vinfo && suggested_unroll_factor > 1)
>      {
>        if (dump_enabled_p ())
>         dump_printf_loc (MSG_NOTE, vect_location,
> --
> 2.31.1