[PATCH v2] x86: Define __HAVE_FLOAT128 for Clang and use __builtin_*f128 code path

[H.J. Lu]

On Thu, Dec 19, 2024 at 3:00 AM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> From: Fangrui Song <i@maskray.me>
>
> Clang supports __builtin_fabsf128 (despite not supporting _Float128) but
> it does not support __builtin_fabsq.  Fallback to back to
> `typedef __float128 _Float128;` it clang is used.
>
> Authored-by: Fangrui Song <maskray@google.com>
> ---
>  sysdeps/x86/bits/floatn.h | 21 ++++++++++++++-------
>  1 file changed, 14 insertions(+), 7 deletions(-)
>
> diff --git a/sysdeps/x86/bits/floatn.h b/sysdeps/x86/bits/floatn.h
> index e661abaea4..8849b811bc 100644
> --- a/sysdeps/x86/bits/floatn.h
> +++ b/sysdeps/x86/bits/floatn.h
> @@ -28,7 +28,8 @@
>     support, for x86_64 and x86.  */
>  #if (defined __x86_64__                                                        \
>       ? __GNUC_PREREQ (4, 3)                                            \
> -     : (defined __GNU__ ? __GNUC_PREREQ (4, 5) : __GNUC_PREREQ (4, 4)))
> +     : (defined __GNU__ ? __GNUC_PREREQ (4, 5) : __GNUC_PREREQ (4, 4))) \
> +    || defined __clang__
>  # define __HAVE_FLOAT128 1

__float128 was added to Clang 3.4.

>  #else
>  # define __HAVE_FLOAT128 0
> @@ -58,7 +59,9 @@
>  /* Defined to concatenate the literal suffix to be used with _Float128
>     types, if __HAVE_FLOAT128 is 1. */
>  # if __HAVE_FLOAT128
> -#  if !__GNUC_PREREQ (7, 0) || (defined __cplusplus && !__GNUC_PREREQ (13, 0))
> +#  if !__GNUC_PREREQ (7, 0) \
> +      || (defined __cplusplus && !__GNUC_PREREQ (13, 0)) \
> +      || defined __clang__
>  /* The literal suffix f128 exists only since GCC 7.0.  */
>  #   define __f128(x) x##q
>  #  else
> @@ -68,7 +71,9 @@
>
>  /* Defined to a complex binary128 type if __HAVE_FLOAT128 is 1.  */
>  # if __HAVE_FLOAT128
> -#  if !__GNUC_PREREQ (7, 0) || (defined __cplusplus && !__GNUC_PREREQ (13, 0))
> +#  if !__GNUC_PREREQ (7, 0) \
> +      || (defined __cplusplus && !__GNUC_PREREQ (13, 0)) \
> +      || defined __clang__
>  /* Add a typedef for older GCC compilers which don't natively support
>     _Complex _Float128.  */
>  typedef _Complex float __cfloat128 __attribute__ ((__mode__ (__TC__)));
> @@ -82,12 +87,14 @@ typedef _Complex float __cfloat128 __attribute__ ((__mode__ (__TC__)));
>  # if __HAVE_FLOAT128
>
>  /* The type _Float128 exists only since GCC 7.0.  */
> -#  if !__GNUC_PREREQ (7, 0) || (defined __cplusplus && !__GNUC_PREREQ (13, 0))
> +#  if !__GNUC_PREREQ (7, 0) \
> +      || (defined __cplusplus && !__GNUC_PREREQ (13, 0)) \
> +      || defined __clang__

__float128 was added to Clang 3.4.

>  typedef __float128 _Float128;
>  #  endif
>
>  /* __builtin_huge_valf128 doesn't exist before GCC 7.0.  */
> -#  if !__GNUC_PREREQ (7, 0)
> +#  if !__GNUC_PREREQ (7, 0) && !defined __clang__

__builtin_huge_valf128 was added to Clang 7.0.

>  #   define __builtin_huge_valf128() ((_Float128) __builtin_huge_val ())
>  #  endif
>
> @@ -96,7 +103,7 @@ typedef __float128 _Float128;
>     Converting a narrower sNaN to _Float128 produces a quiet NaN, so
>     attempts to use _Float128 sNaNs will not work properly with older
>     compilers.  */
> -#  if !__GNUC_PREREQ (7, 0)
> +#  if !__GNUC_PREREQ (7, 0) && !defined __clang__

These are also added to Clang 7.0.

>  #   define __builtin_copysignf128 __builtin_copysignq
>  #   define __builtin_fabsf128 __builtin_fabsq
>  #   define __builtin_inff128() ((_Float128) __builtin_inf ())
> @@ -108,7 +115,7 @@ typedef __float128 _Float128;
>     e.g.: __builtin_signbitf128, before GCC 6.  However, there has never
>     been a __builtin_signbitf128 in GCC and the type-generic builtin is
>     only available since GCC 6.  */
> -#  if !__GNUC_PREREQ (6, 0)
> +#  if !__GNUC_PREREQ (6, 0) && !defined __clang__
>  #   define __builtin_signbitf128 __signbitf128
>  #  endif
>
> --
> 2.47.1
>


-- 
H.J.