Add float128 support for x86_64, x86.

This patch enables float128 support for x86_64 and x86.  All GCC
versions that can build glibc provide the required support, but since
GCC 6 and before don't provide __builtin_nanq / __builtin_nansq, sNaN
tests and some tests of NaN payloads need to be disabled with such
compilers (this does not affect the generated glibc binaries at all,
just the tests).  bits/floatn.h declares float128 support to be
available for GCC versions that provide the required libgcc support
(4.3 for x86_64, 4.4 for i386 GNU/Linux, 4.5 for i386 GNU/Hurd);
compilation-only support was present some time before then, but not
really useful without the libgcc functions.

fenv_private.h needed updating to avoid trying to put _Float128 values
in registers.  I make no assertion of optimality of the
math_opt_barrier / math_force_eval definitions for this case; they are
simply intended to be sufficient to work correctly.

Tested for x86_64 and x86, with GCC 7 and GCC 6.  (Testing for x32 was
compilation tests only with build-many-glibcs.py to verify the ABI
baseline updates.  I have not done any testing for Hurd, although the
float128 support is enabled there as for GNU/Linux.)

	* sysdeps/i386/Implies: Add ieee754/float128.
	* sysdeps/x86_64/Implies: Likewise.
	* sysdeps/x86/bits/floatn.h: New file.
	* sysdeps/x86/float128-abi.h: Likewise.
	* manual/math.texi (Mathematics): Document support for _Float128
	on x86_64 and x86.
	* sysdeps/i386/fpu/fenv_private.h: Include <bits/floatn.h>.
	(math_opt_barrier): Do not put _Float128 values in floating-point
	registers.
	(math_force_eval): Likewise.
	[__x86_64__] (SET_RESTORE_ROUNDF128): New macro.
	* sysdeps/x86/fpu/Makefile [$(subdir) = math] (CPPFLAGS): Append
	to Makefile variable.
	* sysdeps/x86/fpu/e_sqrtf128.c: New file.
	* sysdeps/x86/fpu/sfp-machine.h: Likewise.  Based on libgcc.
	* sysdeps/x86/math-tests.h: New file.
	* math/libm-test-support.h (XFAIL_FLOAT128_PAYLOAD): New macro.
	* math/libm-test-getpayload.inc (getpayload_test_data): Use
	XFAIL_FLOAT128_PAYLOAD.
	* math/libm-test-setpayload.inc (setpayload_test_data): Likewise.
	* math/libm-test-totalorder.inc (totalorder_test_data): Likewise.
	* math/libm-test-totalordermag.inc (totalordermag_test_data):
	Likewise.
	* sysdeps/unix/sysv/linux/i386/libc.abilist: Update.
	* sysdeps/unix/sysv/linux/i386/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/x86_64/64/libc.abilist: Likewise.
	* sysdeps/unix/sysv/linux/x86_64/64/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist: Likewise.
	* sysdeps/unix/sysv/linux/x86_64/x32/libm.abilist: Likewise.
	* sysdeps/i386/fpu/libm-test-ulps: Likewise.
	* sysdeps/i386/i686/fpu/multiarch/libm-test-ulps: Likewise.
	* sysdeps/x86_64/fpu/libm-test-ulps: Likewise.

1 files changed, 7 insertions, 7 deletions

diff --git a/NEWS b/NEWS
index 027f09b..960c9f8 100644
--- a/NEWS
+++ b/NEWS
@@ -121,13 +121,13 @@ Version 2.26
   C Library is GCC 4.9.  Older GCC versions, and non-GNU compilers, can
   still be used to compile programs using the GNU C Library.
 
-* Support is added, on powerpc64le, for interfaces supporting the _Float128
-  type from ISO/IEC TS 18661-3:2015.  Most of the interfaces are taken from
-  TS 18661-3.  The type-generic macros in <math.h> support this type, but
-  those in <tgmath.h> do not.  The GNU C Library now requires GCC 6.2 or
-  later to build for powerpc64le.  When used with GCC versions before GCC
-  7, these interfaces may be used with the type under the non-standard name
-  __float128.
+* Support is added, on powerpc64le, x86_64 and x86, for interfaces
+  supporting the _Float128 type from ISO/IEC TS 18661-3:2015.  Most of the
+  interfaces are taken from TS 18661-3.  The type-generic macros in <math.h>
+  support this type, but those in <tgmath.h> do not.  The GNU C Library now
+  requires GCC 6.2 or later to build for powerpc64le.  When used with GCC
+  versions before GCC 7, these interfaces may be used with the type under
+  the non-standard name __float128.
 
   New <stdlib.h> functions from ISO/IEC TS 18661-3: