Add nextup and nextdown math functions

TS 18661 adds nextup and nextdown functions alongside nextafter to provide
support for float128 equivalent to it.  This patch adds nextupl, nextup,
nextupf, nextdownl, nextdown and nextdownf to libm before float128 support.

The nextup functions return the next representable value in the direction of
positive infinity and the nextdown functions return the next representable
value in the direction of negative infinity.  These are currently enabled
as GNU extensions.

1 files changed, 7 insertions, 0 deletions

diff --git a/math/bits/mathcalls.h b/math/bits/mathcalls.h
index 9a7b3f0f18..e2cf49f627 100644
--- a/math/bits/mathcalls.h
+++ b/math/bits/mathcalls.h
@@ -294,6 +294,13 @@ __MATHCALLX (nextafter,, (_Mdouble_ __x, _Mdouble_ __y), (__const__));
 __MATHCALLX (nexttoward,, (_Mdouble_ __x, long double __y), (__const__));
 # endif
 
+#ifdef __USE_GNU
+/* Return X - epsilon.  */
+__MATHCALL (nextdown,, (_Mdouble_ __x));
+/* Return X + epsilon.  */
+__MATHCALL (nextup,, (_Mdouble_ __x));
+# endif
+
 /* Return the remainder of integer divison X / Y with infinite precision.  */
 __MATHCALL (remainder,, (_Mdouble_ __x, _Mdouble_ __y));