Re: [PATCH] i386: Save/restore recog_data in ix86_vector_duplicate_value [PR106577]

[Uros Bizjak <ubizjak@gmail.com>]

On Fri, Dec 2, 2022 at 10:39 AM Jakub Jelinek <jakub@redhat.com> wrote:
>
> Hi!
>
> On Tue, Aug 16, 2022 at 09:14:06AM +0100, Richard Sandiford via Gcc-patches wrote:
> > IMO the correct low-effort fix is to save and restore recog_data
> > in ix86_vector_duplicate_value.  It's a relatively big copy,
> > but the current code is pretty wasteful anyway (allocating at
> > least a new SET and INSN for every query).  Compared to the
> > overhead of doing that, a copy to and from the stack shouldn't
> > be too bad.
>
> The following patch does that.
> It isn't the first spot in the compiler that does that, not even the first
> spot in the i386 backend.
> In i386-expand.cc beyond these 2 recog_memoized calls there is one in
> expand_vselect, but I think it is unlikely we'd run into these issues trying
> to expand new permutations from splitters.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
>
> 2022-12-02  Jakub Jelinek  <jakub@redhat.com>
>
>         PR target/106577
>         * config/i386/i386-expand.cc (ix86_vector_duplicate_value): Save/restore
>         recog_data around recog_memoized calls.
>
>         * gcc.target/i386/pr106577.c: New test.

OK.

Thanks,
Uros.

>
> --- gcc/config/i386/i386-expand.cc.jj   2022-12-01 09:29:15.233466321 +0100
> +++ gcc/config/i386/i386-expand.cc      2022-12-01 14:05:55.901157211 +0100
> @@ -15187,6 +15187,10 @@ ix86_vector_duplicate_value (machine_mod
>    bool ok;
>    rtx_insn *insn;
>    rtx dup;
> +  /* Save/restore recog_data in case this is called from splitters
> +     or other routines where recog_data needs to stay valid across
> +     force_reg.  See PR106577.  */
> +  recog_data_d recog_data_save = recog_data;
>
>    /* First attempt to recognize VAL as-is.  */
>    dup = gen_vec_duplicate (mode, val);
> @@ -15212,6 +15216,7 @@ ix86_vector_duplicate_value (machine_mod
>        ok = recog_memoized (insn) >= 0;
>        gcc_assert (ok);
>      }
> +  recog_data = recog_data_save;
>    return true;
>  }
>
> --- gcc/testsuite/gcc.target/i386/pr106577.c.jj 2022-12-01 14:13:03.973872383 +0100
> +++ gcc/testsuite/gcc.target/i386/pr106577.c    2022-12-01 14:13:03.973872383 +0100
> @@ -0,0 +1,10 @@
> +/* PR target/106577 */
> +/* { dg-do compile { target int128 } } */
> +/* { dg-options "-O2 -mavx" } */
> +
> +int i;
> +void
> +foo (void)
> +{
> +  i ^= !(((unsigned __int128)0xf0f0f0f0f0f0f0f0 << 64 | 0xf0f0f0f0f0f0f0f0) & i);
> +}
>
>
>         Jakub
>