Re: [PATCH] strub: avoid lto inlining

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

On Thu, Dec 14, 2023 at 8:53 PM Alexandre Oliva <oliva@adacore.com> wrote:
>
>
> The strub builtins are not suited for cross-unit inlining, they should
> only be inlined by the builtin expanders, if at all.  While testing on
> sparc64, it occurred to me that, if libgcc was built with LTO enabled,
> lto1 might inline them, and that would likely break things.  So, make
> sure they're clearly marked as not inlinable.
>
> Regstrapped on x86_64-linux-gnu, also testing on sparc-solaris2.11.3.
> Ok to install?
>
>
> for  libgcc/ChangeLog
>
>         * strub.c (ATTRIBUTE_NOINLINE): New.
>         (ATTRIBUTE_STRUB_CALLABLE): Add it.
>         (__strub_dummy_force_no_leaf): Drop it.
> ---
>  libgcc/strub.c |    8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/libgcc/strub.c b/libgcc/strub.c
> index b0f990d9deebb..5062554d0e1e6 100644
> --- a/libgcc/strub.c
> +++ b/libgcc/strub.c
> @@ -36,7 +36,12 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
>  # define TOPS <
>  #endif
>
> -#define ATTRIBUTE_STRUB_CALLABLE __attribute__ ((__strub__ ("callable")))
> +/* Make sure these builtins won't be inlined, even with LTO.  */
> +#define ATTRIBUTE_NOINLINE \
> +  __attribute__ ((__noinline__, __noclone__))

I think __noipa__ is more complete and will make the libgcc functions appear
as black boxes to callers.

OK your or this way.

Richard.

> +
> +#define ATTRIBUTE_STRUB_CALLABLE \
> +  __attribute__ ((__strub__ ("callable"))) ATTRIBUTE_NOINLINE
>
>  /* Enter a stack scrubbing context, initializing the watermark to the caller's
>     stack address.  */
> @@ -72,7 +77,6 @@ __strub_update (void **watermark)
>  /* Dummy function, called to force the caller to not be a leaf function, so
>     that it can't use the red zone.  */
>  static void ATTRIBUTE_STRUB_CALLABLE
> -__attribute__ ((__noinline__, __noipa__))
>  __strub_dummy_force_no_leaf (void)>  {
>  }
>
> --
> 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