[PATCH] libgfortran: Fix up LIBGFOR_CHECK_FLOAT128 [PR106137]

[Tobias Burnus]

On 29.06.22 14:13, Jakub Jelinek via Fortran wrote:
> My recent gfortran + libgfortran patch apparently broke (some?) aarch64
> builds.  While it is desirable to use just _Float128 rather than __float128,
> we only want to use it (and e.g. define HAVE_FLOAT128) on targets where
> _Float128 is supported and long double isn't IEEE quad precision.
> Which is targets that support __float128 type which we have been testing
> for before - _Float128 is supported on those targets and on targets where
> long double is IEEE quad precision.
>
> So, the following patch restores check for whether __float128 is supported
> into the LIBGFOR_CHECK_FLOAT128 check which determines whether
> HAVE_FLOAT128 is defined or whether to use libquadmath, so that e.g. on
> aarch64 where long double is IEEE quad we don't do that.
>
> Tested by Tamar on aarch64 and by me on x86_64-linux, ok for trunk?
> 2022-06-29  Jakub Jelinek  <jakub@redhat.com>
>
>       PR bootstrap/106137
>       * acinclude.m4 (LIBGFOR_CHECK_FLOAT128): Also test for __float128.
>       * configure: Regenerated.
>
> --- libgfortran/acinclude.m4.jj       2022-06-28 13:14:45.327799267 +0200
> +++ libgfortran/acinclude.m4  2022-06-29 11:45:19.286551469 +0200
> @@ -276,7 +276,6 @@ AC_DEFUN([LIBGFOR_CHECK_FLOAT128], [
>      GCC_TRY_COMPILE_OR_LINK([
>       _Float128 foo (_Float128 x)

...

> +    __float128 baz (__float128 x)

As now both __float128 and _Float128 is tested, can you also update:

  dnl Check whether we have a __float128 type
  AC_DEFUN([LIBGFOR_CHECK_FLOAT128], [

...
    AC_CACHE_CHECK([whether we have a usable _Float128 type],
                   libgfor_cv_have_float128, [

I note that your follow-up patch adds _Float128 to the dnl comment,
but I think __float128 should also be added to the cache output to
make clear that both _Float128/__float128 are checked.

Otherwise: LGTM.

Thanks,

Tobias

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