diff --git a/ChangeLog b/ChangeLog
index 4a574f52c3..980c5cbaf3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,35 @@
 2018-02-01  Joseph Myers  <joseph@codesourcery.com>
 
+	* include/fenv.h [!_ISOMAC && !FE_TONEAREST]: Give #error.
+	[!_ISOMAC] (FE_HAVE_ROUNDING_MODES): New macro.
+	* sysdeps/generic/math_private.h
+	[!FE_HAVE_ROUNDING_MODES && FE_ALL_EXCEPT == 0] (fegetenv): New
+	inline function.
+	[!FE_HAVE_ROUNDING_MODES && FE_ALL_EXCEPT == 0] (__fegetenv):
+	Likewise.
+	[!FE_HAVE_ROUNDING_MODES && FE_ALL_EXCEPT == 0] (fesetenv):
+	Likewise.
+	[!FE_HAVE_ROUNDING_MODES && FE_ALL_EXCEPT == 0] (__fesetenv):
+	Likewise.
+	[!FE_HAVE_ROUNDING_MODES && FE_ALL_EXCEPT == 0] (feupdateenv):
+	Likewise.
+	[!FE_HAVE_ROUNDING_MODES && FE_ALL_EXCEPT == 0] (__feupdateenv):
+	Likewise.
+	[!FE_HAVE_ROUNDING_MODES] (fegetround): Likewise.
+	[!FE_HAVE_ROUNDING_MODES] (__fegetround): Likewise.
+	[!FE_HAVE_ROUNDING_MODES] (fesetround): Likewise.
+	[!FE_HAVE_ROUNDING_MODES] (__fesetround): Likewise.
+	* sysdeps/tile/math_private.h (fegetenv): Remove inline function.
+	(__fegetenv): Likewise.
+	(fesetenv): Likewise.
+	(__fesetenv): Likewise.
+	(feupdateenv): Likewise.
+	(__feupdateenv): Likewise.
+	(fegetround): Likewise.
+	(__fegetround): Likewise.
+	(fesetround): Likewise.
+	(__fesetround): Likewise.
+
 	* sysdeps/generic/math_private.h [FE_ALL_EXCEPT == 0]
 	(feraiseexcept): New macro.
 	[FE_ALL_EXCEPT == 0] (__feraiseexcept): Likewise.
diff --git a/include/fenv.h b/include/fenv.h
index de4d46f8b7..76679e1e18 100644
--- a/include/fenv.h
+++ b/include/fenv.h
@@ -42,6 +42,21 @@ struct rm_ctx
   fenv_t env;
   bool updated_status;
 };
+
+/* Track whether rounding mode macros were defined, since
+   get-rounding-mode.h may define default versions if they weren't.
+   FE_TONEAREST must always be defined (even if no changes of rounding
+   mode are supported, glibc requires it to be defined to represent
+   the default rounding mode).  */
+# ifndef FE_TONEAREST
+#  error "FE_TONEAREST not defined"
+# endif
+# if defined FE_DOWNWARD || defined FE_TOWARDZERO || defined FE_UPWARD
+#  define FE_HAVE_ROUNDING_MODES 1
+# else
+#  define FE_HAVE_ROUNDING_MODES 0
+# endif
+
 #endif
 
 #endif
diff --git a/sysdeps/generic/math_private.h b/sysdeps/generic/math_private.h
index acfbd9b6cc..f93cf6927e 100644
--- a/sysdeps/generic/math_private.h
+++ b/sysdeps/generic/math_private.h
@@ -654,4 +654,72 @@ libc_feresetround_noex_ctx (struct rm_ctx *ctx)
 # define __feraiseexcept(excepts) ((void) 0)
 #endif
 
+/* Similarly, most <fenv.h> functions have trivial implementations in
+   the absence of support for floating-point exceptions and rounding
+   modes.  */
+
+#if !FE_HAVE_ROUNDING_MODES
+# if FE_ALL_EXCEPT == 0
+extern inline int
+fegetenv (fenv_t *__e)
+{
+  return 0;
+}
+
+extern inline int
+__fegetenv (fenv_t *__e)
+{
+  return 0;
+}
+
+extern inline int
+fesetenv (const fenv_t *__e)
+{
+  return 0;
+}
+
+extern inline int
+__fesetenv (const fenv_t *__e)
+{
+  return 0;
+}
+
+extern inline int
+feupdateenv (const fenv_t *__e)
+{
+  return 0;
+}
+
+extern inline int
+__feupdateenv (const fenv_t *__e)
+{
+  return 0;
+}
+# endif
+
+extern inline int
+fegetround (void)
+{
+  return FE_TONEAREST;
+}
+
+extern inline int
+__fegetround (void)
+{
+  return FE_TONEAREST;
+}
+
+extern inline int
+fesetround (int __d)
+{
+  return 0;
+}
+
+extern inline int
+__fesetround (int __d)
+{
+  return 0;
+}
+#endif
+
 #endif /* _MATH_PRIVATE_H_ */
diff --git a/sysdeps/tile/math_private.h b/sysdeps/tile/math_private.h
index 6dc43f4228..32b549ff4e 100644
--- a/sysdeps/tile/math_private.h
+++ b/sysdeps/tile/math_private.h
@@ -15,9 +15,7 @@
    success in every case.
 
    The overrides for libc_ functions must happen before we include
-   the generic math_private.h, and the overrides for regular
-   <fenv.h> functions must happen afterwards, to avoid clashing with
-   the declarations of those functions.  */
+   the generic math_private.h.  */
 
 #define libc_fesetround(rnd)			({ 0; })
 #define libc_fetestexcept(exc)			({ 0; })
@@ -26,15 +24,4 @@
 
 #include_next <math_private.h>
 
-extern inline int fegetenv (fenv_t *__e)	{ return 0; }
-extern inline int __fegetenv (fenv_t *__e)	{ return 0; }
-extern inline int fesetenv (const fenv_t *__e)	{ return 0; }
-extern inline int __fesetenv (const fenv_t *__e)	{ return 0; }
-extern inline int feupdateenv (const fenv_t *__e) { return 0; }
-extern inline int __feupdateenv (const fenv_t *__e) { return 0; }
-extern inline int fegetround (void)		{ return FE_TONEAREST; }
-extern inline int __fegetround (void)		{ return FE_TONEAREST; }
-extern inline int fesetround (int __d)		{ return 0; }
-extern inline int __fesetround (int __d)	{ return 0; }
-
 #endif