Use GCC builtins for rint functions if desired.

This patch is using the corresponding GCC builtin for rintf, rint,
rintl and rintf128 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.

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

sysdeps/generic/math-use-builtins.h

@@ -26,4 +26,9 @@
 #define USE_NEARBYINTL_BUILTIN 0
 #define USE_NEARBYINTF128_BUILTIN 0
 
+#define USE_RINT_BUILTIN 0
+#define USE_RINTF_BUILTIN 0
+#define USE_RINTL_BUILTIN 0
+#define USE_RINTF128_BUILTIN 0
+
 #endif /* math-use-builtins.h */

sysdeps/ieee754/dbl-64/s_rint.c

@@ -23,16 +23,20 @@
 #include <math.h>
 #include <math_private.h>
 #include <libm-alias-double.h>
+#include <math-use-builtins.h>
 
+double
+__rint (double x)
+{
+#if USE_RINT_BUILTIN
+  return __builtin_rint (x);
+#else
+  /* Use generic implementation.  */
   static const double
     TWO52[2] = {
 		4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */
 		-4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */
   };
-
-double
-__rint (double x)
-{
   int64_t i0, sx;
   int32_t j0;
   EXTRACT_WORDS64 (i0, x);
@@ -59,6 +63,7 @@ __rint (double x)
     }
   double w = TWO52[sx] + x;
   return w - TWO52[sx];
+#endif /* ! USE_RINT_BUILTIN  */
 }
 #ifndef __rint
 libm_alias_double (__rint, rint)

sysdeps/ieee754/float128/float128_private.h

@@ -142,6 +142,8 @@
 #include <math-use-builtins.h>
 #undef USE_NEARBYINTL_BUILTIN
 #define USE_NEARBYINTL_BUILTIN USE_NEARBYINTF128_BUILTIN
+#undef USE_RINTL_BUILTIN
+#define USE_RINTL_BUILTIN USE_RINTF128_BUILTIN
 
 /* IEEE function renames.  */
 #define __ieee754_acoshl __ieee754_acoshf128
@@ -346,6 +348,7 @@
 #define __builtin_copysignl __builtin_copysignf128
 #define __builtin_signbitl __builtin_signbit
 #define __builtin_nearbyintl __builtin_nearbyintf128
+#define __builtin_rintl __builtin_rintf128
 
 /* Get the constant suffix from bits/floatn-compat.h.  */
 #define L(x) __f128 (x)

sysdeps/ieee754/flt-32/s_rintf.c

@@ -17,16 +17,20 @@
 #include <math.h>
 #include <math_private.h>
 #include <libm-alias-float.h>
+#include <math-use-builtins.h>
 
+float
+__rintf(float x)
+{
+#if USE_RINTF_BUILTIN
+  return __builtin_rintf (x);
+#else
+  /* Use generic implementation.  */
   static const float
     TWO23[2] = {
 		8.3886080000e+06, /* 0x4b000000 */
 		-8.3886080000e+06, /* 0xcb000000 */
   };
-
-float
-__rintf(float x)
-{
 	int32_t i0,j0,sx;
 	float w,t;
 	GET_FLOAT_WORD(i0,x);
@@ -46,6 +50,7 @@ __rintf(float x)
 	}
 	w = TWO23[sx]+x;
 	return w-TWO23[sx];
+#endif /* ! USE_RINTF_BUILTIN  */
 }
 #ifndef __rintf
 libm_alias_float (__rint, rint)

sysdeps/ieee754/ldbl-128/s_rintl.c

@@ -31,15 +31,19 @@ static char rcsid[] = "$NetBSD: $";
 #include <math.h>
 #include <math_private.h>
 #include <libm-alias-ldouble.h>
+#include <math-use-builtins.h>
 
+_Float128 __rintl(_Float128 x)
+{
+#if USE_RINTL_BUILTIN
+  return __builtin_rintl (x);
+#else
+  /* Use generic implementation.  */
   static const _Float128
     TWO112[2] = {
 		 5.19229685853482762853049632922009600E+33L, /* 0x406F000000000000, 0 */
 		 -5.19229685853482762853049632922009600E+33L  /* 0xC06F000000000000, 0 */
   };
-
-_Float128 __rintl(_Float128 x)
-{
 	int64_t i0,j0,sx;
 	uint64_t i1 __attribute__ ((unused));
 	_Float128 w,t;
@@ -60,5 +64,6 @@ _Float128 __rintl(_Float128 x)
 	}
 	w = TWO112[sx]+x;
 	return w-TWO112[sx];
+#endif /* ! USE_RINTL_BUILTIN  */
 }
 libm_alias_ldouble (__rint, rint)

sysdeps/s390/fpu/math-use-builtins.h

@@ -30,10 +30,16 @@
 # define USE_NEARBYINTF_BUILTIN 1
 # define USE_NEARBYINTL_BUILTIN 1
 
+# define USE_RINT_BUILTIN 1
+# define USE_RINTF_BUILTIN 1
+# define USE_RINTL_BUILTIN 1
+
 # if __GNUC_PREREQ (8, 0)
 #  define USE_NEARBYINTF128_BUILTIN 1
+#  define USE_RINTF128_BUILTIN 1
 # else
 #  define USE_NEARBYINTF128_BUILTIN 0
+#  define USE_RINTF128_BUILTIN 0
 # endif
 
 #else
@@ -44,6 +50,11 @@
 # define USE_NEARBYINTL_BUILTIN 0
 # define USE_NEARBYINTF128_BUILTIN 0
 
+# define USE_RINT_BUILTIN 0
+# define USE_RINTF_BUILTIN 0
+# define USE_RINTL_BUILTIN 0
+# define USE_RINTF128_BUILTIN 0
+
 #endif /* ! HAVE_S390_MIN_Z196_ZARCH_ASM_SUPPORT  */
 
 #endif /* math-use-builtins.h */