Re: [PATCH V2 1/2] x86: Don't add crtfastmath.o for -shared

[Uros Bizjak <ubizjak@gmail.com>]

On Thu, Dec 15, 2022 at 7:23 AM liuhongt <hongtao.liu@intel.com> wrote:
>
> Update in V2:
> Split -shared change into a separate commit and add some documentation
> for it.
> Bootstrapped and regtested on x86_64-pc-linu-gnu{-m32,}.
> Ok of trunk?
>
> Don't add crtfastmath.o for -shared to avoid changing the MXCSR register
> when loading a shared library.  crtfastmath.o will be used only when
> building executables.
>
>          PR target/55522
>         * config/i386/gnu-user-common.h (GNU_USER_TARGET_MATHFILE_SPEC):
>         Don't add crtfastmath.o for -shared.
>         * doc/invoke.texi (-shared): Add related documentation.

OK.

Thanks,
Uros.

> ---
>  gcc/config/i386/gnu-user-common.h | 2 +-
>  gcc/doc/invoke.texi               | 3 ++-
>  2 files changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/gcc/config/i386/gnu-user-common.h b/gcc/config/i386/gnu-user-common.h
> index cab9be2bfb7..9910cd64363 100644
> --- a/gcc/config/i386/gnu-user-common.h
> +++ b/gcc/config/i386/gnu-user-common.h
> @@ -47,7 +47,7 @@ along with GCC; see the file COPYING3.  If not see
>
>  /* Similar to standard GNU userspace, but adding -ffast-math support.  */
>  #define GNU_USER_TARGET_MATHFILE_SPEC \
> -  "%{Ofast|ffast-math|funsafe-math-optimizations:crtfastmath.o%s} \
> +  "%{Ofast|ffast-math|funsafe-math-optimizations:%{!shared:crtfastmath.o%s}} \
>     %{mpc32:crtprec32.o%s} \
>     %{mpc64:crtprec64.o%s} \
>     %{mpc80:crtprec80.o%s}"
> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> index cb40b38b73a..cba4f19f4f4 100644
> --- a/gcc/doc/invoke.texi
> +++ b/gcc/doc/invoke.texi
> @@ -17656,7 +17656,8 @@ needs to build supplementary stub code for constructors to work.  On
>  multi-libbed systems, @samp{gcc -shared} must select the correct support
>  libraries to link against.  Failing to supply the correct flags may lead
>  to subtle defects.  Supplying them in cases where they are not necessary
> -is innocuous.}
> +is innocuous. For x86, crtfastmath.o will not be added when
> +@option{-shared} is specified. }
>
>  @item -shared-libgcc
>  @itemx -static-libgcc
> --
> 2.27.0
>