Add iszero.

TS 18661-1 adds an iszero classification macro to <math.h>.  This
patch implements it for glibc.  There are no new underlying functions
in libm because the implementation uses fpclassify when sNaN support
is required and a direct comparison otherwise; any optimizations for
this macro should be done through adding __builtin_iszero in GCC and
using it in the header for suitable GCC versions, not through adding
other optimized inline or out-of-line versions to glibc.

Tested for x86_64 and x86.

	* math/math.h [__GLIBC_USE (IEC_60559_BFP_EXT)] (iszero): New
	macro.
	* math/libm-test.inc (iszero_test_data): New array.
	(iszero_test): New function.
	(main): Call iszero_test.
	* manual/arith.texi (Floating Point Classes): Document iszero.
	* manual/libm-err-tab.pl: Update comment on interfaces without
	ulps tabulated.

1 files changed, 1 insertions, 1 deletions

diff --git a/NEWS b/NEWS
index 23ca5abdbe..e29527413e 100644
--- a/NEWS
+++ b/NEWS
@@ -51,7 +51,7 @@ Version 2.25
 
 * New <math.h> features are added from TS 18661-1:2014:
 
-  - Classification macros: issubnormal.
+  - Classification macros: issubnormal, iszero.
 
 * The <sys/quota.h> header now includes the <linux/quota.h> header.  Support
   for the Linux quota interface which predates kernel version 2.4.22 has