Use __f128 to define FLT128_* constants in include/float.h for old GCC [committed]

Use __f128 to define FLT128_* constants in include/float.h for old GCC [committed]

[Joseph Myers]

When using compilers before GCC 7, include/float.h provides fallback
definitions of FLT128_* constants.  These definitions use 'Q' constant
suffixes, which works for configurations with _Float128 ABI-distinct
from long double, but not where it has the same ABI as long double.
This patch changes the definitions to use the __f128 macro from
<bits/floatn.h>, so allowing them to work in the non-distinct
_Float128 case (where they are used in building glibc tests, not for
building glibc itself) as well.

Tested (a) with build-many-glibcs.py with GCC 6 (installed stripped
shared libraries unchanged by the patch); (b) with
build-many-glibcs.py with GCC 6 together with the main patch to enable
float128 aliases; (c) for x86_64 with both GCC 6 and GCC 7.  Committed.

2017-10-17  Joseph Myers  <joseph@codesourcery.com>

	* include/float.h [!__GNUC_PREREQ (7, 0) && __HAVE_FLOAT128 &&
	__GLIBC_USE (IEC_60559_TYPES_EXT)] (FLT128_MAX): Define using
	__f128.
	[!__GNUC_PREREQ (7, 0) && __HAVE_FLOAT128 && __GLIBC_USE
	(IEC_60559_TYPES_EXT)] (FLT128_EPSILON): Likewise.
	[!__GNUC_PREREQ (7, 0) && __HAVE_FLOAT128 && __GLIBC_USE
	(IEC_60559_TYPES_EXT)] (FLT128_MIN): Likewise.
	[!__GNUC_PREREQ (7, 0) && __HAVE_FLOAT128 && __GLIBC_USE
	(IEC_60559_TYPES_EXT)] (FLT128_TRUE_MIN): Likewise.

diff --git a/include/float.h b/include/float.h
index 736868f..939c83d 100644
--- a/include/float.h
+++ b/include/float.h
@@ -24,10 +24,14 @@
 # define FLT128_MIN_10_EXP	(-4931)
 # define FLT128_MAX_EXP		16384
 # define FLT128_MAX_10_EXP	4932
-# define FLT128_MAX		1.18973149535723176508575932662800702e+4932Q
-# define FLT128_EPSILON		1.92592994438723585305597794258492732e-34Q
-# define FLT128_MIN		3.36210314311209350626267781732175260e-4932Q
-# define FLT128_TRUE_MIN	6.47517511943802511092443895822764655e-4966Q
+# define FLT128_MAX					\
+  __f128 (1.18973149535723176508575932662800702e+4932)
+# define FLT128_EPSILON					\
+  __f128 (1.92592994438723585305597794258492732e-34)
+# define FLT128_MIN					\
+  __f128 (3.36210314311209350626267781732175260e-4932)
+# define FLT128_TRUE_MIN				\
+  __f128 (6.47517511943802511092443895822764655e-4966)
 #endif
 
 #endif /* _LIBC_FLOAT_H */

-- 
Joseph S. Myers
joseph@codesourcery.com