Re: [PATCH v7 3/3] Use GCC builtins for roundeven functions if desired.

["H.J. Lu" <hjl.tools@gmail.com>]

On Sun, May 23, 2021 at 6:43 PM Shen-Ta Hsieh <ibmibmibm.tw@gmail.com> wrote:
>
> This patch is using the corresponding GCC builtin for roundevenf,
> roundeven and roundevenl if the USE_FUNCTION_BUILTIN macros are defined
> to one in math-use-builtins.h.
>
> These builtin functions is supported since GCC 10.
>
> The code of the generic implementation is not changed.
>
> Signed-off-by: Shen-Ta Hsieh <ibmibmibm.tw@gmail.com>
> ---
>  sysdeps/generic/math-use-builtins-roundeven.h | 4 ++++
>  sysdeps/generic/math-use-builtins.h           | 1 +
>  sysdeps/ieee754/dbl-64/s_roundeven.c          | 5 +++++
>  sysdeps/ieee754/float128/float128_private.h   | 2 ++
>  sysdeps/ieee754/flt-32/s_roundevenf.c         | 5 +++++
>  sysdeps/ieee754/ldbl-128/s_roundevenl.c       | 5 +++++
>  6 files changed, 22 insertions(+)
>  create mode 100644 sysdeps/generic/math-use-builtins-roundeven.h
>
> diff --git a/sysdeps/generic/math-use-builtins-roundeven.h b/sysdeps/generic/math-use-builtins-roundeven.h
> new file mode 100644
> index 0000000000..bd2e84c93f
> --- /dev/null
> +++ b/sysdeps/generic/math-use-builtins-roundeven.h
> @@ -0,0 +1,4 @@
> +#define USE_ROUNDEVEN_BUILTIN 0
> +#define USE_ROUNDEVENF_BUILTIN 0
> +#define USE_ROUNDEVENL_BUILTIN 0
> +#define USE_ROUNDEVENF128_BUILTIN 0
> diff --git a/sysdeps/generic/math-use-builtins.h b/sysdeps/generic/math-use-builtins.h
> index cc3e9f2201..19d2d1cf3c 100644
> --- a/sysdeps/generic/math-use-builtins.h
> +++ b/sysdeps/generic/math-use-builtins.h
> @@ -30,6 +30,7 @@
>  #include <math-use-builtins-ceil.h>
>  #include <math-use-builtins-trunc.h>
>  #include <math-use-builtins-round.h>
> +#include <math-use-builtins-roundeven.h>
>  #include <math-use-builtins-copysign.h>
>  #include <math-use-builtins-sqrt.h>
>  #include <math-use-builtins-fma.h>
> diff --git a/sysdeps/ieee754/dbl-64/s_roundeven.c b/sysdeps/ieee754/dbl-64/s_roundeven.c
> index 5deff3bb8a..88c051e9fe 100644
> --- a/sysdeps/ieee754/dbl-64/s_roundeven.c
> +++ b/sysdeps/ieee754/dbl-64/s_roundeven.c
> @@ -21,6 +21,7 @@
>  #include <math_private.h>
>  #include <libm-alias-double.h>
>  #include <stdint.h>
> +#include <math-use-builtins.h>
>
>  #define BIAS 0x3ff
>  #define MANT_DIG 53
> @@ -29,6 +30,9 @@
>  double
>  __roundeven (double x)
>  {
> +#if USE_ROUNDEVEN_BUILTIN
> +  return __builtin_roundeven (x);
> +#else
>    uint64_t ix, ux;
>    EXTRACT_WORDS64 (ix, x);
>    ux = ix & 0x7fffffffffffffffULL;
> @@ -66,6 +70,7 @@ __roundeven (double x)
>      ix &= 0x8000000000000000ULL;
>    INSERT_WORDS64 (x, ix);
>    return x;
> +#endif /* ! USE_ROUNDEVEN_BUILTIN  */
>  }
>  #ifndef __roundeven
>  libm_alias_double (__roundeven, roundeven)
> diff --git a/sysdeps/ieee754/float128/float128_private.h b/sysdeps/ieee754/float128/float128_private.h
> index 979138851b..b6b6d3d5fd 100644
> --- a/sysdeps/ieee754/float128/float128_private.h
> +++ b/sysdeps/ieee754/float128/float128_private.h
> @@ -152,6 +152,8 @@
>  #define USE_TRUNCL_BUILTIN USE_TRUNCF128_BUILTIN
>  #undef USE_ROUNDL_BUILTIN
>  #define USE_ROUNDL_BUILTIN USE_ROUNDF128_BUILTIN
> +#undef USE_ROUNDEVENL_BUILTIN
> +#define USE_ROUNDEVENL_BUILTIN USE_ROUNDEVENF128_BUILTIN
>  #undef USE_COPYSIGNL_BUILTIN
>  #define USE_COPYSIGNL_BUILTIN USE_COPYSIGNF128_BUILTIN
>  #undef USE_FMAL_BUILTIN
> diff --git a/sysdeps/ieee754/flt-32/s_roundevenf.c b/sysdeps/ieee754/flt-32/s_roundevenf.c
> index 2cc0d7b001..4f568579d8 100644
> --- a/sysdeps/ieee754/flt-32/s_roundevenf.c
> +++ b/sysdeps/ieee754/flt-32/s_roundevenf.c
> @@ -21,6 +21,7 @@
>  #include <math.h>
>  #include <math_private.h>
>  #include <libm-alias-float.h>
> +#include <math-use-builtins.h>
>  #include <stdint.h>
>
>  #define BIAS 0x7f
> @@ -30,6 +31,9 @@
>  float
>  __roundevenf (float x)
>  {
> +#if USE_ROUNDEVENF_BUILTIN
> +  return __builtin_roundevenf (x);
> +#else
>    uint32_t ix, ux;
>    GET_FLOAT_WORD (ix, x);
>    ux = ix & 0x7fffffff;
> @@ -67,6 +71,7 @@ __roundevenf (float x)
>      ix &= 0x80000000;
>    SET_FLOAT_WORD (x, ix);
>    return x;
> +#endif /* ! USE_ROUNDEVENF_BUILTIN  */
>  }
>  #ifndef __roundevenf
>  libm_alias_float (__roundeven, roundeven)
> diff --git a/sysdeps/ieee754/ldbl-128/s_roundevenl.c b/sysdeps/ieee754/ldbl-128/s_roundevenl.c
> index 7c9c11fad2..afbf13d4f2 100644
> --- a/sysdeps/ieee754/ldbl-128/s_roundevenl.c
> +++ b/sysdeps/ieee754/ldbl-128/s_roundevenl.c
> @@ -21,6 +21,7 @@
>  #include <math.h>
>  #include <math_private.h>
>  #include <libm-alias-ldouble.h>
> +#include <math-use-builtins.h>
>  #include <stdint.h>
>
>  #define BIAS 0x3fff
> @@ -30,6 +31,9 @@
>  _Float128
>  __roundevenl (_Float128 x)
>  {
> +#if USE_ROUNDEVENL_BUILTIN
> +  return __builtin_roundevenl (x);
> +#else
>    uint64_t hx, lx, uhx;
>    GET_LDOUBLE_WORDS64 (hx, lx, x);
>    uhx = hx & 0x7fffffffffffffffULL;
> @@ -101,5 +105,6 @@ __roundevenl (_Float128 x)
>      }
>    SET_LDOUBLE_WORDS64 (x, hx, lx);
>    return x;
> +#endif /* ! USE_ROUNDEVENL_BUILTIN  */
>  }
>  libm_alias_ldouble (__roundeven, roundeven)
> --
> 2.31.1
>

LGTM.

Reviewed-by: H.J. Lu <hjl.tools@gmail.com>

Thanks.

-- 
H.J.