Support _Float128 in math-tests.h.

This patch makes math-tests.h, as used to describe support of given
floating-point types for sNaNs, rounding modes and exceptions, handle
distinguishing _Float128 from long double.  This is needed for x86_64,
where if building with GCC 6 or earlier there is no __builtin_nansq,
so no way to get a signaling NaN of _Float128 type, so associated
tests cannot be run (although glibc itself works fine, as there is
never any need to create such an sNaN with a built-in function inside
glibc).

Tested for x86_64 (in conjunction with float128 patches).

	* sysdeps/generic/math-tests.h: Include <bits/floatn.h>.
	(MATH_TESTS_TG): New macro.
	(SNAN_TESTS_float128): Likewise.
	(ROUNDING_TESTS_float128): Likewise.
	(EXCEPTION_TESTS_float128): Likewise.
	(SNAN_TESTS): Define using MATH_TESTS_TG.
	(ROUNDING_TESTS): Likewise.
	(EXCEPTION_TESTS): Likewise.

ChangeLog

@@ -1,5 +1,14 @@
 2017-06-22  Joseph Myers  <joseph@codesourcery.com>
 
+	* sysdeps/generic/math-tests.h: Include <bits/floatn.h>.
+	(MATH_TESTS_TG): New macro.
+	(SNAN_TESTS_float128): Likewise.
+	(ROUNDING_TESTS_float128): Likewise.
+	(EXCEPTION_TESTS_float128): Likewise.
+	(SNAN_TESTS): Define using MATH_TESTS_TG.
+	(ROUNDING_TESTS): Likewise.
+	(EXCEPTION_TESTS): Likewise.
+
 	* sysdeps/ieee754/float128/float128_private.h
 	[SET_RESTORE_ROUNDF128] (SET_RESTORE_ROUNDL): Take an argument and
 	pass it to SET_RESTORE_ROUNDF128.

sysdeps/generic/math-tests.h

@@ -16,6 +16,23 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
+#include <bits/floatn.h>
+
+/* Expand the appropriate macro for whether to enable tests for a
+   given type.  */
+#if __HAVE_DISTINCT_FLOAT128
+# define MATH_TESTS_TG(PREFIX, ARGS, TYPE)				\
+  (sizeof (TYPE) == sizeof (float) ? PREFIX ## float ARGS		\
+   : sizeof (TYPE) == sizeof (double) ? PREFIX ## double ARGS		\
+   : __builtin_types_compatible_p (TYPE, _Float128) ? PREFIX ## float128 ARGS \
+   : PREFIX ## long_double ARGS)
+# else
+# define MATH_TESTS_TG(PREFIX, ARGS, TYPE)				\
+  (sizeof (TYPE) == sizeof (float) ? PREFIX ## float ARGS		\
+   : sizeof (TYPE) == sizeof (double) ? PREFIX ## double ARGS		\
+   : PREFIX ## long_double ARGS)
+#endif
+
 /* Indicate whether to run tests involving sNaN values for the float, double,
    and long double C data types, respectively.  All are run unless
    overridden.  */
@@ -28,12 +45,12 @@
 #ifndef SNAN_TESTS_long_double
 # define SNAN_TESTS_long_double	1
 #endif
+#ifndef SNAN_TESTS_float128
+# define SNAN_TESTS_float128	1
+#endif
 
 /* Return nonzero value if to run tests involving sNaN values for X.  */
-#define SNAN_TESTS(x)							\
-  (sizeof (x) == sizeof (float) ? SNAN_TESTS_float			\
-   : sizeof (x) == sizeof (double) ? SNAN_TESTS_double			\
-   : SNAN_TESTS_long_double)
+#define SNAN_TESTS(x) MATH_TESTS_TG (SNAN_TESTS_, , x)
 
 /* Indicate whether to run tests involving type casts of sNaN values.  These
    are run unless overridden.  */
@@ -61,11 +78,12 @@
 #ifndef ROUNDING_TESTS_long_double
 # define ROUNDING_TESTS_long_double(MODE)	1
 #endif
+#ifndef ROUNDING_TESTS_float128
+# define ROUNDING_TESTS_float128(MODE)	1
+#endif
 
-#define ROUNDING_TESTS(TYPE, MODE)					\
-  (sizeof (TYPE) == sizeof (float) ? ROUNDING_TESTS_float (MODE)	\
-   : sizeof (TYPE) == sizeof (double) ? ROUNDING_TESTS_double (MODE)	\
-   : ROUNDING_TESTS_long_double (MODE))
+#define ROUNDING_TESTS(TYPE, MODE)		\
+  MATH_TESTS_TG (ROUNDING_TESTS_, (MODE), TYPE)
 
 /* Indicate whether to run tests of floating-point exceptions for a
    given floating-point type, given that the exception macros are
@@ -79,11 +97,11 @@
 #ifndef EXCEPTION_TESTS_long_double
 # define EXCEPTION_TESTS_long_double	1
 #endif
+#ifndef EXCEPTION_TESTS_float128
+# define EXCEPTION_TESTS_float128	1
+#endif
 
-#define EXCEPTION_TESTS(TYPE)					\
-  (sizeof (TYPE) == sizeof (float) ? EXCEPTION_TESTS_float	\
-   : sizeof (TYPE) == sizeof (double) ? EXCEPTION_TESTS_double	\
-   : EXCEPTION_TESTS_long_double)
+#define EXCEPTION_TESTS(TYPE) MATH_TESTS_TG (EXCEPTION_TESTS_, , TYPE)
 
 /* Indicate whether the given exception trap(s) can be enabled
    in feenableexcept.  If non-zero, the traps are always supported.