Re: [PR106746] drop cselib addr lookup in debug insn mem

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

On Sat, Jan 14, 2023 at 12:26 PM Alexandre Oliva via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
>
> The testcase used to get scheduled differently depending on the
> presence of debug insns with MEMs.  It's not clear to me why those
> MEMs affected scheduling, but the cselib pre-canonicalization of the
> MEM address is not used at all when analyzing debug insns, so the
> memory allocation and lookup are pure waste.  Somehow, avoiding that
> waste fixes the problem, or makes it go latent.
>
> Regstrapped on x86_64-linux-gnu.  Ok to install?

OK.

Richard.

>
> for  gcc/ChangeLog
>
>         PR debug/106746
>         * sched-deps.cc (sched_analyze_2): Skip cselib address lookup
>         within debug insns.
>
> for  gcc/testsuite/ChangeLog
>
>         PR debug/106746
>         * gcc.dg/target/i386/pr106746.c: New.
> ---
>  gcc/sched-deps.cc                        |   36 +++++++++++++++---------------
>  gcc/testsuite/gcc.target/i386/pr106746.c |   29 ++++++++++++++++++++++++
>  2 files changed, 47 insertions(+), 18 deletions(-)
>  create mode 100644 gcc/testsuite/gcc.target/i386/pr106746.c
>
> diff --git a/gcc/sched-deps.cc b/gcc/sched-deps.cc
> index f9371b81fb41e..a9214f674329a 100644
> --- a/gcc/sched-deps.cc
> +++ b/gcc/sched-deps.cc
> @@ -2605,26 +2605,26 @@ sched_analyze_2 (class deps_desc *deps, rtx x, rtx_insn *insn)
>
>      case MEM:
>        {
> -       /* Reading memory.  */
> -       rtx_insn_list *u;
> -       rtx_insn_list *pending;
> -       rtx_expr_list *pending_mem;
> -       rtx t = x;
> -
> -       if (sched_deps_info->use_cselib)
> -         {
> -           machine_mode address_mode = get_address_mode (t);
> -
> -           t = shallow_copy_rtx (t);
> -           cselib_lookup_from_insn (XEXP (t, 0), address_mode, 1,
> -                                    GET_MODE (t), insn);
> -           XEXP (t, 0)
> -             = cselib_subst_to_values_from_insn (XEXP (t, 0), GET_MODE (t),
> -                                                 insn);
> -         }
> -
>         if (!DEBUG_INSN_P (insn))
>           {
> +           /* Reading memory.  */
> +           rtx_insn_list *u;
> +           rtx_insn_list *pending;
> +           rtx_expr_list *pending_mem;
> +           rtx t = x;
> +
> +           if (sched_deps_info->use_cselib)
> +             {
> +               machine_mode address_mode = get_address_mode (t);
> +
> +               t = shallow_copy_rtx (t);
> +               cselib_lookup_from_insn (XEXP (t, 0), address_mode, 1,
> +                                        GET_MODE (t), insn);
> +               XEXP (t, 0)
> +                 = cselib_subst_to_values_from_insn (XEXP (t, 0), GET_MODE (t),
> +                                                     insn);
> +             }
> +
>             t = canon_rtx (t);
>             pending = deps->pending_read_insns;
>             pending_mem = deps->pending_read_mems;
> diff --git a/gcc/testsuite/gcc.target/i386/pr106746.c b/gcc/testsuite/gcc.target/i386/pr106746.c
> new file mode 100644
> index 0000000000000..14f7dab71d691
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/pr106746.c
> @@ -0,0 +1,29 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fsched2-use-superblocks -fcompare-debug -Wno-psabi" } */
> +
> +typedef char __attribute__((__vector_size__ (64))) U;
> +typedef short __attribute__((__vector_size__ (64))) V;
> +typedef int __attribute__((__vector_size__ (64))) W;
> +
> +char c;
> +U a;
> +U *r;
> +W foo0_v512u32_0;
> +
> +void
> +foo (W)
> +{
> +  U u;
> +  V v;
> +  W w = __builtin_shuffle (foo0_v512u32_0, foo0_v512u32_0);
> +  u =
> +    __builtin_shufflevector (a, u, 3, 0, 4, 9, 9, 6, 7, 8, 5,
> +                            0, 6, 1, 8, 1, 2, 8, 6,
> +                            1, 8, 4, 9, 3, 8, 4, 6, 0, 9, 0, 1, 8, 2, 3, 3,
> +                            0, 4, 9, 9, 6, 7, 8, 5,
> +                            0, 6, 1, 8, 1, 2, 8, 6,
> +                            1, 8, 4, 9, 3, 8, 4, 6, 0, 9, 0, 1, 8, 2, 3);
> +  v *= c;
> +  w &= c;
> +  *r = (U) v + (U) w;
> +}
>
>
> --
> Alexandre Oliva, happy hacker                https://FSFLA.org/blogs/lxo/
>    Free Software Activist                       GNU Toolchain Engineer
> Disinformation flourishes because many people care deeply about injustice
> but very few check the facts.  Ask me about <https://stallmansupport.org>