Do not declare _Float128 support for powerpc64le -mlong-double-64 (bug 22402).

The powerpc bits/floatn.h declares _Float128 support to be present
when the compiler supports it for powerpc64le.  However, in the case
where -mlong-double-64 is used, __MATH_TG does not actually support
_Float128; it only supports _Float128 in the distinct-long-double
case.

This shows up as a build failure when building glibc mainline with GCC
mainline, given the recently added sanity check in math.h for
configurations supported by __MATH_TG, as the compat code for
-mlong-double-64 fails to build.  However, the bug was logically
present before that change (including in 2.26), just less visible.

This patch fixes the build failure by declaring _Float128 to be
unsupported in that case.  (Of course this can't actually stop users
calling the type-generic macros with _Float128 arguments with
-mlong-double-64, just as they could be called with other unsupported
types on other platforms, but perhaps makes it less likely by making
all the type-specific _Float128 interfaces invisible in that case.)

Tested compilation for powerpc64le with build-many-glibcs.py.

	[BZ #22402]
	* sysdeps/powerpc/bits/floatn.h: Include <bits/long-double.h>.
	[__NO_LONG_DOUBLE_MATH] (__HAVE_FLOAT128): Define to 0.

1 files changed, 2 insertions, 1 deletions

diff --git a/sysdeps/powerpc/bits/floatn.h b/sysdeps/powerpc/bits/floatn.h
index 44a9434701..a293bfc996 100644
--- a/sysdeps/powerpc/bits/floatn.h
+++ b/sysdeps/powerpc/bits/floatn.h
@@ -20,12 +20,13 @@
 #define _BITS_FLOATN_H
 
 #include <features.h>
+#include <bits/long-double.h>
 
 /* Defined to 1 if the current compiler invocation provides a
    floating-point type with the IEEE 754 binary128 format, and this glibc
    includes corresponding *f128 interfaces for it.  */
 #if defined _ARCH_PWR8 && defined __LITTLE_ENDIAN__ && (_CALL_ELF == 2) \
-    && defined __FLOAT128__
+    && defined __FLOAT128__ && !defined __NO_LONG_DOUBLE_MATH
 # define __HAVE_FLOAT128 1
 #else
 # define __HAVE_FLOAT128 0