Re: [PATCH] [strub] improve handling of indirected volatile parms [PR112938]

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

On Sat, Mar 9, 2024 at 10:10 AM Alexandre Oliva <oliva@adacore.com> wrote:
>
>
> The earlier patch for PR112938 arranged for volatile parms to be made
> indirect in internal strub wrapped bodies.
>
> The first problem that remained, more evident, was that the indirected
> parameter remained volatile, despite the indirection, but it wasn't
> regimplified, so indirecting it was malformed gimple.
>
> Regimplifying turned out not to be needed.  The best course of action
> was to drop the volatility from the by-reference parm, that was being
> unexpectedly inherited from the original volatile parm.
>
> That exposed another problem: the dereferences would then lose their
> volatile status, so we had to bring volatile back to them.
>
> Regstrapped on x86_64-linux-gnu.  Ok to install?

OK

>
> for  gcc/ChangeLog
>
>         PR middle-end/112938
>         * ipa-strub.cc (pass_ipa_strub::execute): Drop volatility from
>         indirected parm.
>         (maybe_make_indirect): Restore volatility in dereferences.
>
> for  gcc/testsuite/ChangeLog
>
>         PR middle-end/112938
>         * g++.dg/strub-internal-pr112938.cc: New.
> ---
>  gcc/ipa-strub.cc                                |    7 +++++++
>  gcc/testsuite/g++.dg/strub-internal-pr112938.cc |   12 ++++++++++++
>  2 files changed, 19 insertions(+)
>  create mode 100644 gcc/testsuite/g++.dg/strub-internal-pr112938.cc
>
> diff --git a/gcc/ipa-strub.cc b/gcc/ipa-strub.cc
> index dff94222351ad..8fa7bdf530023 100644
> --- a/gcc/ipa-strub.cc
> +++ b/gcc/ipa-strub.cc
> @@ -1940,6 +1940,9 @@ maybe_make_indirect (indirect_parms_t &indirect_parms, tree op, int *rec)
>                           TREE_TYPE (TREE_TYPE (op)),
>                           op,
>                           build_int_cst (TREE_TYPE (op), 0));
> +         if (TYPE_VOLATILE (TREE_TYPE (TREE_TYPE (op)))
> +             && !TREE_THIS_VOLATILE (ret))
> +           TREE_SIDE_EFFECTS (ret) = TREE_THIS_VOLATILE (ret) = 1;
>           return ret;
>         }
>      }
> @@ -2894,6 +2897,10 @@ pass_ipa_strub::execute (function *)
>              probably drop the TREE_ADDRESSABLE and keep the TRUE.  */
>           tree ref_type = build_ref_type_for (nparm);
>
> +         if (TREE_THIS_VOLATILE (nparm)
> +             && TYPE_VOLATILE (TREE_TYPE (nparm))
> +             && !TYPE_VOLATILE (ref_type))
> +           TREE_SIDE_EFFECTS (nparm) = TREE_THIS_VOLATILE (nparm) = 0;
>           DECL_ARG_TYPE (nparm) = TREE_TYPE (nparm) = ref_type;
>           relayout_decl (nparm);
>           TREE_ADDRESSABLE (nparm) = 0;
> diff --git a/gcc/testsuite/g++.dg/strub-internal-pr112938.cc b/gcc/testsuite/g++.dg/strub-internal-pr112938.cc
> new file mode 100644
> index 0000000000000..5a74becc2697e
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/strub-internal-pr112938.cc
> @@ -0,0 +1,12 @@
> +/* { dg-do compile } */
> +/* { dg-options "-fdump-tree-optimized -O2" } */
> +/* { dg-require-effective-target strub } */
> +
> +bool __attribute__ ((__strub__ ("internal")))
> +f(bool i, volatile bool j)
> +{
> +  return (i ^ j) == j;
> +}
> +
> +/* Check for two dereferences of the indirected volatile j parm.  */
> +/* { dg-final { scan-tree-dump-times {={v} \*j_[0-9][0-9]*(D)} 2 "optimized" } } */
>
> --
> Alexandre Oliva, happy hacker            https://FSFLA.org/blogs/lxo/
>    Free Software Activist                   GNU Toolchain Engineer
> More tolerance and less prejudice are key for inclusion and diversity
> Excluding neuro-others for not behaving ""normal"" is *not* inclusive