Use GCC builtins for copysign functions if desired.

This patch is always using the corresponding GCC builtin for copysignf, copysign,
and is using the builtin for copysignl, copysignf128 if the USE_FUNCTION_BUILTIN
macros are defined to one in math-use-builtins.h.

Altough the long double version is enabled by default we still need
the macro and the alternative implementation as the _Float128 version
of the builtin is not available with all supported GCC versions.

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

sysdeps/generic/math-use-builtins.h

@@ -19,6 +19,8 @@
 #ifndef MATH_USE_BUILTINS_H
 #define MATH_USE_BUILTINS_H	1
 
+#include <features.h> /* For __GNUC_PREREQ.  */
+
 /* Define these macros to 1 to use __builtin_xyz instead of the
    generic implementation.  */
 #define USE_NEARBYINT_BUILTIN 0
@@ -51,4 +53,11 @@
 #define USE_ROUNDL_BUILTIN 0
 #define USE_ROUNDF128_BUILTIN 0
 
+#define USE_COPYSIGNL_BUILTIN 1
+#if __GNUC_PREREQ (7, 0)
+# define USE_COPYSIGNF128_BUILTIN 1
+#else
+# define USE_COPYSIGNF128_BUILTIN 0
+#endif
+
 #endif /* math-use-builtins.h */

sysdeps/ieee754/dbl-64/s_copysign.c

@@ -10,7 +10,7 @@
  * ====================================================
  */
 
-#if defined(LIBM_SCCS) && !defined(lint)
+#if defined (LIBM_SCCS) && ! defined (lint)
 static char rcsid[] = "$NetBSD: s_copysign.c,v 1.8 1995/05/10 20:46:57 jtc Exp $";
 #endif
 
@@ -22,16 +22,11 @@ static char rcsid[] = "$NetBSD: s_copysign.c,v 1.8 1995/05/10 20:46:57 jtc Exp $
 
 #define NO_MATH_REDIRECT
 #include <math.h>
-#include <math_private.h>
 #include <libm-alias-double.h>
 
 double
 __copysign (double x, double y)
 {
-  uint32_t hx, hy;
+  return __builtin_copysign (x, y);
-  GET_HIGH_WORD (hx, x);
-  GET_HIGH_WORD (hy, y);
-  SET_HIGH_WORD (x, (hx & 0x7fffffff) | (hy & 0x80000000));
-  return x;
 }
 libm_alias_double (__copysign, copysign)

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_COPYSIGNL_BUILTIN
+#define USE_COPYSIGNL_BUILTIN USE_COPYSIGNF128_BUILTIN
 
 /* IEEE function renames.  */
 #define __ieee754_acoshl __ieee754_acoshf128
@@ -361,6 +363,7 @@
 #define __builtin_ceill __builtin_ceilf128
 #define __builtin_truncl __builtin_truncf128
 #define __builtin_roundl __builtin_roundf128
+#define __builtin_copysignl __builtin_copysignf128
 
 /* Get the constant suffix from bits/floatn-compat.h.  */
 #define L(x) __f128 (x)

sysdeps/ieee754/flt-32/s_copysignf.c

@@ -13,7 +13,7 @@
  * ====================================================
  */
 
-#if defined(LIBM_SCCS) && !defined(lint)
+#if defined (LIBM_SCCS) && ! defined (lint)
 static char rcsid[] = "$NetBSD: s_copysignf.c,v 1.4 1995/05/10 20:46:59 jtc Exp $";
 #endif
 
@@ -25,15 +25,11 @@ static char rcsid[] = "$NetBSD: s_copysignf.c,v 1.4 1995/05/10 20:46:59 jtc Exp
 
 #define NO_MATH_REDIRECT
 #include <math.h>
-#include <math_private.h>
 #include <libm-alias-float.h>
 
-float __copysignf(float x, float y)
+float
+__copysignf (float x, float y)
 {
-	uint32_t ix,iy;
+  return __builtin_copysignf (x, y);
-	GET_FLOAT_WORD(ix,x);
-	GET_FLOAT_WORD(iy,y);
-	SET_FLOAT_WORD(x,(ix&0x7fffffff)|(iy&0x80000000));
-        return x;
 }
 libm_alias_float (__copysign, copysign)

sysdeps/ieee754/ldbl-128/s_copysignl.c

@@ -27,14 +27,20 @@ static char rcsid[] = "$NetBSD: $";
 #include <math.h>
 #include <math_private.h>
 #include <libm-alias-ldouble.h>
+#include <math-use-builtins.h>
 
 _Float128 __copysignl(_Float128 x, _Float128 y)
 {
+#if USE_COPYSIGNL_BUILTIN
+  return __builtin_copysignl (x, y);
+#else
+  /* Use generic implementation.  */
 	uint64_t hx,hy;
 	GET_LDOUBLE_MSW64(hx,x);
 	GET_LDOUBLE_MSW64(hy,y);
 	SET_LDOUBLE_MSW64(x,(hx&0x7fffffffffffffffULL)
 			    |(hy&0x8000000000000000ULL));
         return x;
+#endif /* ! USE_COPYSIGNL_BUILTIN  */
 }
 libm_alias_ldouble (__copysign, copysign)

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

@@ -101,4 +101,11 @@
 
 #endif /* ! HAVE_S390_MIN_Z196_ZARCH_ASM_SUPPORT  */
 
+#define USE_COPYSIGNL_BUILTIN 1
+#if __GNUC_PREREQ (7, 0)
+# define USE_COPYSIGNF128_BUILTIN 1
+#else
+# define USE_COPYSIGNF128_BUILTIN 0
+#endif
+
 #endif /* math-use-builtins.h */