[07/13] Use GCC builtins for nearbyint functions if desired.

Message ID 1575297977-2589-8-git-send-email-stli@linux.ibm.com
State New
Headers show
Series
  • Use GCC builtins for some math functions if desired.
Related show

Commit Message

Stefan Liebler Dec. 2, 2019, 2:46 p.m.
This patch is using the corresponding GCC builtin for nearbyintf, nearbyint,
nearbintl and nearbyintf128 if the USE_FUNCTION_BUILTIN macros are defined to one
in math-use-builtins.h.

This is the case for s390 if build with at least --march=z196 --mzarch.
Otherwise the generic implementation is used.  The code of the generic
implementation is not changed except changes in code style.
---
 sysdeps/generic/math-use-builtins.h         | 29 ++++++++
 sysdeps/ieee754/dbl-64/s_nearbyint.c        |  8 +++
 sysdeps/ieee754/float128/float128_private.h |  4 ++
 sysdeps/ieee754/flt-32/s_nearbyintf.c       | 74 ++++++++++++--------
 sysdeps/ieee754/ldbl-128/s_nearbyintl.c     | 76 ++++++++++++---------
 sysdeps/s390/fpu/math-use-builtins.h        | 45 ++++++++++++
 6 files changed, 175 insertions(+), 61 deletions(-)
 create mode 100644 sysdeps/generic/math-use-builtins.h
 create mode 100644 sysdeps/s390/fpu/math-use-builtins.h

-- 
2.19.1

Comments

Adhemerval Zanella Dec. 5, 2019, 8:40 p.m. | #1
On 02/12/2019 11:46, Stefan Liebler wrote:
> This patch is using the corresponding GCC builtin for nearbyintf, nearbyint,

> nearbintl and nearbyintf128 if the USE_FUNCTION_BUILTIN macros are defined to one

> in math-use-builtins.h.

> 

> This is the case for s390 if build with at least --march=z196 --mzarch.

> Otherwise the generic implementation is used.  The code of the generic

> implementation is not changed except changes in code style.


LGTM with some changes below.

Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>


> ---

>  sysdeps/generic/math-use-builtins.h         | 29 ++++++++

>  sysdeps/ieee754/dbl-64/s_nearbyint.c        |  8 +++

>  sysdeps/ieee754/float128/float128_private.h |  4 ++

>  sysdeps/ieee754/flt-32/s_nearbyintf.c       | 74 ++++++++++++--------

>  sysdeps/ieee754/ldbl-128/s_nearbyintl.c     | 76 ++++++++++++---------

>  sysdeps/s390/fpu/math-use-builtins.h        | 45 ++++++++++++

>  6 files changed, 175 insertions(+), 61 deletions(-)

>  create mode 100644 sysdeps/generic/math-use-builtins.h

>  create mode 100644 sysdeps/s390/fpu/math-use-builtins.h

> 

> diff --git a/sysdeps/generic/math-use-builtins.h b/sysdeps/generic/math-use-builtins.h

> new file mode 100644

> index 0000000000..e12490ed41

> --- /dev/null

> +++ b/sysdeps/generic/math-use-builtins.h

> @@ -0,0 +1,29 @@

> +/* Using math gcc builtins instead of generic implementation.  Generic version.

> +   Copyright (C) 2019 Free Software Foundation, Inc.

> +   This file is part of the GNU C Library.

> +

> +   The GNU C Library is free software; you can redistribute it and/or

> +   modify it under the terms of the GNU Lesser General Public

> +   License as published by the Free Software Foundation; either

> +   version 2.1 of the License, or (at your option) any later version.

> +

> +   The GNU C Library is distributed in the hope that it will be useful,

> +   but WITHOUT ANY WARRANTY; without even the implied warranty of

> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

> +   Lesser General Public License for more details.

> +

> +   You should have received a copy of the GNU Lesser General Public

> +   License along with the GNU C Library; if not, see

> +   <https://www.gnu.org/licenses/>.  */

> +

> +#ifndef MATH_USE_BUILTINS_H

> +#define MATH_USE_BUILTINS_H	1

> +

> +/* Define these macros to 1 to use __builtin_xyz instead of the

> +   generic implementation.  */

> +#define USE_NEARBYINT_BUILTIN 0

> +#define USE_NEARBYINTF_BUILTIN 0

> +#define USE_NEARBYINTL_BUILTIN 0

> +#define USE_NEARBYINTF128_BUILTIN 0

> +

> +#endif /* math-use-builtins.h */


Ok.

> diff --git a/sysdeps/ieee754/dbl-64/s_nearbyint.c b/sysdeps/ieee754/dbl-64/s_nearbyint.c

> index c261885c5a..08a148e21e 100644

> --- a/sysdeps/ieee754/dbl-64/s_nearbyint.c

> +++ b/sysdeps/ieee754/dbl-64/s_nearbyint.c

> @@ -26,16 +26,23 @@

>  #include <math_private.h>

>  #include <fenv_private.h>

>  #include <libm-alias-double.h>

> +#include <math-use-builtins.h>

>  

> +#if ! USE_NEARBYINT_BUILTIN

>  static const double

>  TWO52[2] = {

>  	    4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */

>  	    -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */

>  };

> +#endif


You could just move it inside the !USE_NEARBYINT_BUILTIN within the
function.

>  

>  double

>  __nearbyint (double x)

>  {

> +#if USE_NEARBYINT_BUILTIN

> +  return __builtin_nearbyint (x);

> +#else

> +  /* Use generic implementation.  */

>    fenv_t env;

>    int64_t i0, sx;

>    int32_t j0;

> @@ -67,5 +74,6 @@ __nearbyint (double x)

>    math_force_eval (t);

>    libc_fesetenv (&env);

>    return t;

> +#endif /* USE_NEARBYINT_BUILTIN  */

>  }

>  libm_alias_double (__nearbyint, nearbyint)


Ok.

> diff --git a/sysdeps/ieee754/float128/float128_private.h b/sysdeps/ieee754/float128/float128_private.h

> index 4e31ef365b..e96986a968 100644

> --- a/sysdeps/ieee754/float128/float128_private.h

> +++ b/sysdeps/ieee754/float128/float128_private.h

> @@ -139,6 +139,9 @@

>  #undef libm_alias_double_ldouble

>  #define libm_alias_double_ldouble(func) libm_alias_float64_float128 (func)

>  

> +#include <math-use-builtins.h>

> +#undef USE_NEARBYINTL_BUILTIN

> +#define USE_NEARBYINTL_BUILTIN USE_NEARBYINTF128_BUILTIN


Ok.

>  

>  /* IEEE function renames.  */

>  #define __ieee754_acoshl __ieee754_acoshf128

> @@ -342,6 +345,7 @@

>  /* Builtin renames.  */

>  #define __builtin_copysignl __builtin_copysignf128

>  #define __builtin_signbitl __builtin_signbit

> +#define __builtin_nearbyintl __builtin_nearbyintf128

>  

>  /* Get the constant suffix from bits/floatn-compat.h.  */

>  #define L(x) __f128 (x)


Ok.

> diff --git a/sysdeps/ieee754/flt-32/s_nearbyintf.c b/sysdeps/ieee754/flt-32/s_nearbyintf.c

> index acedf34c90..d31bbdd19a 100644

> --- a/sysdeps/ieee754/flt-32/s_nearbyintf.c

> +++ b/sysdeps/ieee754/flt-32/s_nearbyintf.c

> @@ -21,42 +21,56 @@

>  #include <math_private.h>

>  #include <fenv_private.h>

>  #include <libm-alias-float.h>

> +#include <math-use-builtins.h>

>  

> +#if ! USE_NEARBYINTF_BUILTIN

>  static const float

> -TWO23[2]={

> -  8.3886080000e+06, /* 0x4b000000 */

> - -8.3886080000e+06, /* 0xcb000000 */

> +TWO23[2] = {

> +	    8.3886080000e+06, /* 0x4b000000 */

> +	    -8.3886080000e+06, /* 0xcb000000 */

>  };

> +#endif


You could just move it inside the !USE_NEARBYINT_BUILTIN within the
function.

>  

>  float

> -__nearbyintf(float x)

> +__nearbyintf (float x)

>  {

> -	fenv_t env;

> -	int32_t i0,j0,sx;

> -	float w,t;

> -	GET_FLOAT_WORD(i0,x);

> -	sx = (i0>>31)&1;

> -	j0 = ((i0>>23)&0xff)-0x7f;

> -	if(j0<23) {

> -	    if(j0<0) {

> -		libc_feholdexceptf (&env);

> -		w = TWO23[sx] + math_opt_barrier (x);

> -		t =  w-TWO23[sx];

> -		math_force_eval (t);

> -		libc_fesetenvf (&env);

> -		GET_FLOAT_WORD(i0,t);

> -		SET_FLOAT_WORD(t,(i0&0x7fffffff)|(sx<<31));

> -		return t;

> -	    }

> -	} else {

> -	    if(__builtin_expect(j0==0x80, 0)) return x+x;	/* inf or NaN */

> -	    else return x;		/* x is integral */

> +#if USE_NEARBYINTF_BUILTIN

> +  return __builtin_nearbyintf (x);

> +#else

> +  /* Use generic implementation.  */

> +  fenv_t env;

> +  int32_t i0, j0, sx;

> +  float w, t;

> +  GET_FLOAT_WORD (i0, x);

> +  sx = (i0 >> 31) & 1;

> +  j0 = ((i0 >> 23) & 0xff) - 0x7f;

> +  if (j0 < 23)

> +    {

> +      if (j0 < 0)

> +	{

> +	  libc_feholdexceptf (&env);

> +	  w = TWO23[sx] + math_opt_barrier (x);

> +	  t =  w - TWO23[sx];

> +	  math_force_eval (t);

> +	  libc_fesetenvf (&env);

> +	  GET_FLOAT_WORD (i0, t);

> +	  SET_FLOAT_WORD (t, (i0 & 0x7fffffff) | (sx << 31));

> +	  return t;

>  	}

> -	libc_feholdexceptf (&env);

> -	w = TWO23[sx] + math_opt_barrier (x);

> -	t = w-TWO23[sx];

> -	math_force_eval (t);

> -	libc_fesetenvf (&env);

> -	return t;

> +    }

> +  else

> +    {

> +      if (__glibc_unlikely (j0 == 0x80))

> +	return x + x;		/* inf or NaN  */

> +      else

> +	return x;		/* x is integral  */

> +  }

> +  libc_feholdexceptf (&env);

> +  w = TWO23[sx] + math_opt_barrier (x);

> +  t = w - TWO23[sx];

> +  math_force_eval (t);

> +  libc_fesetenvf (&env);

> +  return t;

> +#endif /* USE_NEARBYINT_BUILTIN  */

>  }

>  libm_alias_float (__nearbyint, nearbyint)


Ok, but fix the indentation in a separted patch.

> diff --git a/sysdeps/ieee754/ldbl-128/s_nearbyintl.c b/sysdeps/ieee754/ldbl-128/s_nearbyintl.c

> index f044cb4334..8f3a7e8e6b 100644

> --- a/sysdeps/ieee754/ldbl-128/s_nearbyintl.c

> +++ b/sysdeps/ieee754/ldbl-128/s_nearbyintl.c

> @@ -28,42 +28,56 @@

>  #include <math-barriers.h>

>  #include <math_private.h>

>  #include <libm-alias-ldouble.h>

> +#include <math-use-builtins.h>

>  

> +#if ! USE_NEARBYINTL_BUILTIN

>  static const _Float128

> -TWO112[2]={

> -  L(5.19229685853482762853049632922009600E+33), /* 0x406F000000000000, 0 */

> - L(-5.19229685853482762853049632922009600E+33)  /* 0xC06F000000000000, 0 */

> +TWO112[2] = {

> +	     L(5.19229685853482762853049632922009600E+33), /* 0x406F000000000000, 0 */

> +	     L(-5.19229685853482762853049632922009600E+33)  /* 0xC06F000000000000, 0 */

>  };

> +#endif


You could just move it inside the !USE_NEARBYINT_BUILTIN within the
function.

>  

> -_Float128 __nearbyintl(_Float128 x)

> +_Float128 __nearbyintl (_Float128 x)

>  {

> -	fenv_t env;

> -	int64_t i0,j0,sx;

> -	uint64_t i1 __attribute__ ((unused));

> -	_Float128 w,t;

> -	GET_LDOUBLE_WORDS64(i0,i1,x);

> -	sx = (((uint64_t)i0)>>63);

> -	j0 = ((i0>>48)&0x7fff)-0x3fff;

> -	if(j0<112) {

> -	    if(j0<0) {

> -		feholdexcept (&env);

> -	        w = TWO112[sx] + math_opt_barrier (x);

> -	        t = w-TWO112[sx];

> -		math_force_eval (t);

> -	        fesetenv (&env);

> -		GET_LDOUBLE_MSW64(i0,t);

> -		SET_LDOUBLE_MSW64(t,(i0&0x7fffffffffffffffLL)|(sx<<63));

> -	        return t;

> -	    }

> -	} else {

> -	    if(j0==0x4000) return x+x;	/* inf or NaN */

> -	    else return x;		/* x is integral */

> +#if USE_NEARBYINTL_BUILTIN

> +  return __builtin_nearbyintl (x);

> +#else

> +  /* Use generic implementation.  */

> +  fenv_t env;

> +  int64_t i0, j0, sx;

> +  uint64_t i1 __attribute__ ((unused));

> +  _Float128 w, t;

> +  GET_LDOUBLE_WORDS64 (i0, i1, x);

> +  sx = (((uint64_t) i0) >> 63);

> +  j0 = ((i0 >> 48) & 0x7fff) - 0x3fff;

> +  if (j0 < 112)

> +    {

> +      if (j0 < 0)

> +	{

> +	  feholdexcept (&env);

> +	  w = TWO112[sx] + math_opt_barrier (x);

> +	  t = w - TWO112[sx];

> +	  math_force_eval (t);

> +	  fesetenv (&env);

> +	  GET_LDOUBLE_MSW64 (i0, t);

> +	  SET_LDOUBLE_MSW64 (t, (i0 & 0x7fffffffffffffffLL) | (sx << 63));

> +	  return t;

>  	}

> -	feholdexcept (&env);

> -	w = TWO112[sx] + math_opt_barrier (x);

> -	t = w-TWO112[sx];

> -	math_force_eval (t);

> -	fesetenv (&env);

> -	return t;

> +    }

> +  else

> +    {

> +      if (j0 == 0x4000)

> +	return x + x;		/* inf or NaN  */

> +      else

> +	return x;		/* x is integral  */

> +    }

> +  feholdexcept (&env);

> +  w = TWO112[sx] + math_opt_barrier (x);

> +  t = w - TWO112[sx];

> +  math_force_eval (t);

> +  fesetenv (&env);

> +  return t;

> +#endif /* USE_NEARBYINTL_BUILTIN  */

>  }

>  libm_alias_ldouble (__nearbyint, nearbyint)


Ok, but fix the indentation in a separated patch.

> diff --git a/sysdeps/s390/fpu/math-use-builtins.h b/sysdeps/s390/fpu/math-use-builtins.h

> new file mode 100644

> index 0000000000..fd9da8893e

> --- /dev/null

> +++ b/sysdeps/s390/fpu/math-use-builtins.h

> @@ -0,0 +1,45 @@

> +/* Using math gcc builtins instead of generic implementation.  s390/s390x version.

> +   Copyright (C) 2019 Free Software Foundation, Inc.

> +   This file is part of the GNU C Library.

> +

> +   The GNU C Library is free software; you can redistribute it and/or

> +   modify it under the terms of the GNU Lesser General Public

> +   License as published by the Free Software Foundation; either

> +   version 2.1 of the License, or (at your option) any later version.

> +

> +   The GNU C Library is distributed in the hope that it will be useful,

> +   but WITHOUT ANY WARRANTY; without even the implied warranty of

> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

> +   Lesser General Public License for more details.

> +

> +   You should have received a copy of the GNU Lesser General Public

> +   License along with the GNU C Library; if not, see

> +   <https://www.gnu.org/licenses/>.  */

> +

> +#ifndef MATH_USE_BUILTINS_S390_H

> +#define MATH_USE_BUILTINS_S390_H	1

> +

> +#ifdef HAVE_S390_MIN_Z196_ZARCH_ASM_SUPPORT

> +

> +# include <features.h> /* For __GNUC_PREREQ.  */

> +

> +/* GCC emits the z196 zarch "load fp integer" instructions for these

> +   builtins if build with at least --march=z196 -mzarch.  Otherwise a

> +   function call to libc is emitted.  */

> +# define USE_NEARBYINT_BUILTIN 1

> +# define USE_NEARBYINTF_BUILTIN 1

> +# define USE_NEARBYINTL_BUILTIN 1

> +

> +# if __GNUC_PREREQ (8, 1)

> +#  define USE_NEARBYINTF128_BUILTIN 1

> +# else

> +#  define USE_NEARBYINTF128_BUILTIN 0

> +# endif

> +

> +#else

> +

> +# include_next <math-use-builtins.h>

> +

> +#endif

> +

> +#endif /* math-use-builtins.h */

> 


Ok, but since the idea is to just override it by the architecture I think
it should be more clear to just replicate the expected USE_NEARBYINT*
values for !HAVE_S390_MIN_Z196_ZARCH_ASM_SUPPORT.

Patch

diff --git a/sysdeps/generic/math-use-builtins.h b/sysdeps/generic/math-use-builtins.h
new file mode 100644
index 0000000000..e12490ed41
--- /dev/null
+++ b/sysdeps/generic/math-use-builtins.h
@@ -0,0 +1,29 @@ 
+/* Using math gcc builtins instead of generic implementation.  Generic version.
+   Copyright (C) 2019 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef MATH_USE_BUILTINS_H
+#define MATH_USE_BUILTINS_H	1
+
+/* Define these macros to 1 to use __builtin_xyz instead of the
+   generic implementation.  */
+#define USE_NEARBYINT_BUILTIN 0
+#define USE_NEARBYINTF_BUILTIN 0
+#define USE_NEARBYINTL_BUILTIN 0
+#define USE_NEARBYINTF128_BUILTIN 0
+
+#endif /* math-use-builtins.h */
diff --git a/sysdeps/ieee754/dbl-64/s_nearbyint.c b/sysdeps/ieee754/dbl-64/s_nearbyint.c
index c261885c5a..08a148e21e 100644
--- a/sysdeps/ieee754/dbl-64/s_nearbyint.c
+++ b/sysdeps/ieee754/dbl-64/s_nearbyint.c
@@ -26,16 +26,23 @@ 
 #include <math_private.h>
 #include <fenv_private.h>
 #include <libm-alias-double.h>
+#include <math-use-builtins.h>
 
+#if ! USE_NEARBYINT_BUILTIN
 static const double
 TWO52[2] = {
 	    4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */
 	    -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */
 };
+#endif
 
 double
 __nearbyint (double x)
 {
+#if USE_NEARBYINT_BUILTIN
+  return __builtin_nearbyint (x);
+#else
+  /* Use generic implementation.  */
   fenv_t env;
   int64_t i0, sx;
   int32_t j0;
@@ -67,5 +74,6 @@  __nearbyint (double x)
   math_force_eval (t);
   libc_fesetenv (&env);
   return t;
+#endif /* USE_NEARBYINT_BUILTIN  */
 }
 libm_alias_double (__nearbyint, nearbyint)
diff --git a/sysdeps/ieee754/float128/float128_private.h b/sysdeps/ieee754/float128/float128_private.h
index 4e31ef365b..e96986a968 100644
--- a/sysdeps/ieee754/float128/float128_private.h
+++ b/sysdeps/ieee754/float128/float128_private.h
@@ -139,6 +139,9 @@ 
 #undef libm_alias_double_ldouble
 #define libm_alias_double_ldouble(func) libm_alias_float64_float128 (func)
 
+#include <math-use-builtins.h>
+#undef USE_NEARBYINTL_BUILTIN
+#define USE_NEARBYINTL_BUILTIN USE_NEARBYINTF128_BUILTIN
 
 /* IEEE function renames.  */
 #define __ieee754_acoshl __ieee754_acoshf128
@@ -342,6 +345,7 @@ 
 /* Builtin renames.  */
 #define __builtin_copysignl __builtin_copysignf128
 #define __builtin_signbitl __builtin_signbit
+#define __builtin_nearbyintl __builtin_nearbyintf128
 
 /* Get the constant suffix from bits/floatn-compat.h.  */
 #define L(x) __f128 (x)
diff --git a/sysdeps/ieee754/flt-32/s_nearbyintf.c b/sysdeps/ieee754/flt-32/s_nearbyintf.c
index acedf34c90..d31bbdd19a 100644
--- a/sysdeps/ieee754/flt-32/s_nearbyintf.c
+++ b/sysdeps/ieee754/flt-32/s_nearbyintf.c
@@ -21,42 +21,56 @@ 
 #include <math_private.h>
 #include <fenv_private.h>
 #include <libm-alias-float.h>
+#include <math-use-builtins.h>
 
+#if ! USE_NEARBYINTF_BUILTIN
 static const float
-TWO23[2]={
-  8.3886080000e+06, /* 0x4b000000 */
- -8.3886080000e+06, /* 0xcb000000 */
+TWO23[2] = {
+	    8.3886080000e+06, /* 0x4b000000 */
+	    -8.3886080000e+06, /* 0xcb000000 */
 };
+#endif
 
 float
-__nearbyintf(float x)
+__nearbyintf (float x)
 {
-	fenv_t env;
-	int32_t i0,j0,sx;
-	float w,t;
-	GET_FLOAT_WORD(i0,x);
-	sx = (i0>>31)&1;
-	j0 = ((i0>>23)&0xff)-0x7f;
-	if(j0<23) {
-	    if(j0<0) {
-		libc_feholdexceptf (&env);
-		w = TWO23[sx] + math_opt_barrier (x);
-		t =  w-TWO23[sx];
-		math_force_eval (t);
-		libc_fesetenvf (&env);
-		GET_FLOAT_WORD(i0,t);
-		SET_FLOAT_WORD(t,(i0&0x7fffffff)|(sx<<31));
-		return t;
-	    }
-	} else {
-	    if(__builtin_expect(j0==0x80, 0)) return x+x;	/* inf or NaN */
-	    else return x;		/* x is integral */
+#if USE_NEARBYINTF_BUILTIN
+  return __builtin_nearbyintf (x);
+#else
+  /* Use generic implementation.  */
+  fenv_t env;
+  int32_t i0, j0, sx;
+  float w, t;
+  GET_FLOAT_WORD (i0, x);
+  sx = (i0 >> 31) & 1;
+  j0 = ((i0 >> 23) & 0xff) - 0x7f;
+  if (j0 < 23)
+    {
+      if (j0 < 0)
+	{
+	  libc_feholdexceptf (&env);
+	  w = TWO23[sx] + math_opt_barrier (x);
+	  t =  w - TWO23[sx];
+	  math_force_eval (t);
+	  libc_fesetenvf (&env);
+	  GET_FLOAT_WORD (i0, t);
+	  SET_FLOAT_WORD (t, (i0 & 0x7fffffff) | (sx << 31));
+	  return t;
 	}
-	libc_feholdexceptf (&env);
-	w = TWO23[sx] + math_opt_barrier (x);
-	t = w-TWO23[sx];
-	math_force_eval (t);
-	libc_fesetenvf (&env);
-	return t;
+    }
+  else
+    {
+      if (__glibc_unlikely (j0 == 0x80))
+	return x + x;		/* inf or NaN  */
+      else
+	return x;		/* x is integral  */
+  }
+  libc_feholdexceptf (&env);
+  w = TWO23[sx] + math_opt_barrier (x);
+  t = w - TWO23[sx];
+  math_force_eval (t);
+  libc_fesetenvf (&env);
+  return t;
+#endif /* USE_NEARBYINT_BUILTIN  */
 }
 libm_alias_float (__nearbyint, nearbyint)
diff --git a/sysdeps/ieee754/ldbl-128/s_nearbyintl.c b/sysdeps/ieee754/ldbl-128/s_nearbyintl.c
index f044cb4334..8f3a7e8e6b 100644
--- a/sysdeps/ieee754/ldbl-128/s_nearbyintl.c
+++ b/sysdeps/ieee754/ldbl-128/s_nearbyintl.c
@@ -28,42 +28,56 @@ 
 #include <math-barriers.h>
 #include <math_private.h>
 #include <libm-alias-ldouble.h>
+#include <math-use-builtins.h>
 
+#if ! USE_NEARBYINTL_BUILTIN
 static const _Float128
-TWO112[2]={
-  L(5.19229685853482762853049632922009600E+33), /* 0x406F000000000000, 0 */
- L(-5.19229685853482762853049632922009600E+33)  /* 0xC06F000000000000, 0 */
+TWO112[2] = {
+	     L(5.19229685853482762853049632922009600E+33), /* 0x406F000000000000, 0 */
+	     L(-5.19229685853482762853049632922009600E+33)  /* 0xC06F000000000000, 0 */
 };
+#endif
 
-_Float128 __nearbyintl(_Float128 x)
+_Float128 __nearbyintl (_Float128 x)
 {
-	fenv_t env;
-	int64_t i0,j0,sx;
-	uint64_t i1 __attribute__ ((unused));
-	_Float128 w,t;
-	GET_LDOUBLE_WORDS64(i0,i1,x);
-	sx = (((uint64_t)i0)>>63);
-	j0 = ((i0>>48)&0x7fff)-0x3fff;
-	if(j0<112) {
-	    if(j0<0) {
-		feholdexcept (&env);
-	        w = TWO112[sx] + math_opt_barrier (x);
-	        t = w-TWO112[sx];
-		math_force_eval (t);
-	        fesetenv (&env);
-		GET_LDOUBLE_MSW64(i0,t);
-		SET_LDOUBLE_MSW64(t,(i0&0x7fffffffffffffffLL)|(sx<<63));
-	        return t;
-	    }
-	} else {
-	    if(j0==0x4000) return x+x;	/* inf or NaN */
-	    else return x;		/* x is integral */
+#if USE_NEARBYINTL_BUILTIN
+  return __builtin_nearbyintl (x);
+#else
+  /* Use generic implementation.  */
+  fenv_t env;
+  int64_t i0, j0, sx;
+  uint64_t i1 __attribute__ ((unused));
+  _Float128 w, t;
+  GET_LDOUBLE_WORDS64 (i0, i1, x);
+  sx = (((uint64_t) i0) >> 63);
+  j0 = ((i0 >> 48) & 0x7fff) - 0x3fff;
+  if (j0 < 112)
+    {
+      if (j0 < 0)
+	{
+	  feholdexcept (&env);
+	  w = TWO112[sx] + math_opt_barrier (x);
+	  t = w - TWO112[sx];
+	  math_force_eval (t);
+	  fesetenv (&env);
+	  GET_LDOUBLE_MSW64 (i0, t);
+	  SET_LDOUBLE_MSW64 (t, (i0 & 0x7fffffffffffffffLL) | (sx << 63));
+	  return t;
 	}
-	feholdexcept (&env);
-	w = TWO112[sx] + math_opt_barrier (x);
-	t = w-TWO112[sx];
-	math_force_eval (t);
-	fesetenv (&env);
-	return t;
+    }
+  else
+    {
+      if (j0 == 0x4000)
+	return x + x;		/* inf or NaN  */
+      else
+	return x;		/* x is integral  */
+    }
+  feholdexcept (&env);
+  w = TWO112[sx] + math_opt_barrier (x);
+  t = w - TWO112[sx];
+  math_force_eval (t);
+  fesetenv (&env);
+  return t;
+#endif /* USE_NEARBYINTL_BUILTIN  */
 }
 libm_alias_ldouble (__nearbyint, nearbyint)
diff --git a/sysdeps/s390/fpu/math-use-builtins.h b/sysdeps/s390/fpu/math-use-builtins.h
new file mode 100644
index 0000000000..fd9da8893e
--- /dev/null
+++ b/sysdeps/s390/fpu/math-use-builtins.h
@@ -0,0 +1,45 @@ 
+/* Using math gcc builtins instead of generic implementation.  s390/s390x version.
+   Copyright (C) 2019 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef MATH_USE_BUILTINS_S390_H
+#define MATH_USE_BUILTINS_S390_H	1
+
+#ifdef HAVE_S390_MIN_Z196_ZARCH_ASM_SUPPORT
+
+# include <features.h> /* For __GNUC_PREREQ.  */
+
+/* GCC emits the z196 zarch "load fp integer" instructions for these
+   builtins if build with at least --march=z196 -mzarch.  Otherwise a
+   function call to libc is emitted.  */
+# define USE_NEARBYINT_BUILTIN 1
+# define USE_NEARBYINTF_BUILTIN 1
+# define USE_NEARBYINTL_BUILTIN 1
+
+# if __GNUC_PREREQ (8, 1)
+#  define USE_NEARBYINTF128_BUILTIN 1
+# else
+#  define USE_NEARBYINTF128_BUILTIN 0
+# endif
+
+#else
+
+# include_next <math-use-builtins.h>
+
+#endif
+
+#endif /* math-use-builtins.h */