4 files changed, 60 insertions, 1 deletions
diff --git a/sysdeps/ia64/bits/floatn.h b/sysdeps/ia64/bits/floatn.h
index c7b1df6d2c..dbb6eb2325 100644
--- a/sysdeps/ia64/bits/floatn.h
+++ b/sysdeps/ia64/bits/floatn.h
@@ -89,6 +89,14 @@ typedef __float128 _Float128;
 #  define __builtin_nansf128(x) ((_Float128) __builtin_nans (x))
 # endif
 
+/* In math/math.h, __MATH_TG will expand signbit to __builtin_signbit*,
+   e.g.: __builtin_signbitf128, before GCC 6.  However, there has never
+   been a __builtin_signbitf128 in GCC and the type-generic builtin is
+   only available since GCC 6.  */
+# if !__GNUC_PREREQ (6, 0)
+#  define __builtin_signbitf128 __signbitf128
+# endif
+
 #endif
 
 #endif /* _BITS_FLOATN_H */
diff --git a/sysdeps/ieee754/float128/s_signbitf128.c b/sysdeps/ieee754/float128/s_signbitf128.c
index 71c1ca3a34..4ea010365a 100644
--- a/sysdeps/ieee754/float128/s_signbitf128.c
+++ b/sysdeps/ieee754/float128/s_signbitf128.c
@@ -1,2 +1,37 @@
+/* Return nonzero value if number is negative.
+   Copyright (C) 2017 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
+   <http://www.gnu.org/licenses/>.  */
+
 #include <float128_private.h>
-#include "../ldbl-128/s_signbitl.c"
+#include <math.h>
+#include <math_private.h>
+
+/* Once GCC >= 6.0 is required for building glibc, this implementation can
+   be removed and replaced with an inclusion of ldbl-128/s_signbitl.c.  */
+int
+__signbitf128 (_Float128 x)
+{
+#if __GNUC_PREREQ (6, 0)
+  return __builtin_signbit (x);
+#else
+  int64_t e;
+
+  GET_FLOAT128_MSW64 (e, x);
+  return e < 0;
+#endif
+}
+hidden_def (__signbitf128)
diff --git a/sysdeps/powerpc/bits/floatn.h b/sysdeps/powerpc/bits/floatn.h
index be57e7015f..0ce997c68c 100644
--- a/sysdeps/powerpc/bits/floatn.h
+++ b/sysdeps/powerpc/bits/floatn.h
@@ -87,6 +87,14 @@ typedef __float128 _Float128;
 #  define __builtin_nansf128 __builtin_nansq
 # endif
 
+/* In math/math.h, __MATH_TG will expand signbit to __builtin_signbit*,
+   e.g.: __builtin_signbitf128, before GCC 6.  However, there has never
+   been a __builtin_signbitf128 in GCC and the type-generic builtin is
+   only available since GCC 6.  */
+# if !__GNUC_PREREQ (6, 0)
+#  define __builtin_signbitf128 __signbitf128
+# endif
+
 #endif
 
 #endif /* _BITS_FLOATN_H */
diff --git a/sysdeps/x86/bits/floatn.h b/sysdeps/x86/bits/floatn.h
index 23f74782ea..f93a9f8dbb 100644
--- a/sysdeps/x86/bits/floatn.h
+++ b/sysdeps/x86/bits/floatn.h
@@ -91,6 +91,14 @@ typedef __float128 _Float128;
 #  define __builtin_nansf128(x) ((_Float128) __builtin_nans (x))
 # endif
 
+/* In math/math.h, __MATH_TG will expand signbit to __builtin_signbit*,
+   e.g.: __builtin_signbitf128, before GCC 6.  However, there has never
+   been a __builtin_signbitf128 in GCC and the type-generic builtin is
+   only available since GCC 6.  */
+# if !__GNUC_PREREQ (6, 0)
+#  define __builtin_signbitf128 __signbitf128
+# endif
+
 #endif
 
 #endif /* _BITS_FLOATN_H */