Add SNAN, SNANF, SNANL macros [committed]

[Joseph Myers <joseph at codesourcery dot com>]

TS 18661-1 defines SNAN macros for signaling NaN values, suitable for
use in static initializers.  This patch adds them to glibc's <math.h>
(provided you are building with GCC 3.3 or later; no attempt is made
to provide any kind of nonconforming fallback for older compilers
without the __builtin_nans functions).

Tested for x86_64 and x86.  Committed.

2016-10-28  Joseph Myers  <joseph@codesourcery.com>

	* math/math.h
	[__GLIBC_USE (IEC_60559_BFP_EXT) && __GNUC_PREREQ (3, 3)] (SNANF):
	New macro.
	[__GLIBC_USE (IEC_60559_BFP_EXT) && __GNUC_PREREQ (3, 3)] (SNAN):
	Likewise.
	[__GLIBC_USE (IEC_60559_BFP_EXT) && __GNUC_PREREQ (3, 3)] (SNANL):
	Likewise.
	* manual/arith.texi (Infinity and NaN): Document SNANF, SNAN and
	SNANL.
	* math/test-double.h (snan_value_MACRO): New macro.
	* math/test-float.h (snan_value_MACRO): Likewise.
	* math/test-ldouble.h (snan_value_MACRO): Likewise.
	* math/libm-test.inc (issignaling_test_data): Add tests of
	snan_value_MACRO.

diff --git a/NEWS b/NEWS
index 2da72cd..65184b1 100644
--- a/NEWS
+++ b/NEWS
@@ -51,6 +51,8 @@ Version 2.25
 
 * New <math.h> features are added from TS 18661-1:2014:
 
+  - Signaling NaN macros: SNANF, SNAN, SNANL.
+
   - Comparison macros: iseqsig.
 
   - Classification macros: iscanonical, issubnormal, iszero.
diff --git a/manual/arith.texi b/manual/arith.texi
index a5c04e4..f0f3bb4 100644
--- a/manual/arith.texi
+++ b/manual/arith.texi
@@ -711,6 +711,15 @@ such as by defining @code{_GNU_SOURCE}, and then you must include
 @file{math.h}.)
 @end deftypevr
 
+@comment math.h
+@comment ISO
+@deftypevr Macro float SNANF
+@deftypevrx Macro double SNAN
+@deftypevrx Macro {long double} SNANL
+These macros, defined by TS 18661-1:2014, are constant expressions for
+signaling NaNs.
+@end deftypevr
+
 @w{IEEE 754} also allows for another unusual value: negative zero.  This
 value is produced when you divide a positive number by negative
 infinity, or when a negative result is smaller than the limits of
diff --git a/math/libm-test.inc b/math/libm-test.inc
index 7106338..88420ee 100644
--- a/math/libm-test.inc
+++ b/math/libm-test.inc
@@ -8901,6 +8901,8 @@ static const struct test_f_i_data issignaling_test_data[] =
     TEST_f_b (issignaling, -qnan_value, 0, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
     TEST_f_b (issignaling, snan_value, 1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
     TEST_f_b (issignaling, -snan_value, 1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_b (issignaling, snan_value_MACRO, 1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_b (issignaling, -snan_value_MACRO, 1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
   };
 
 static void
diff --git a/math/math.h b/math/math.h
index 7c0c709..70d9b86 100644
--- a/math/math.h
+++ b/math/math.h
@@ -45,6 +45,15 @@ __BEGIN_DECLS
 # include <bits/nan.h>
 #endif /* __USE_ISOC99 */
 
+#if __GLIBC_USE (IEC_60559_BFP_EXT)
+/* Signaling NaN macros, if supported.  */
+# if __GNUC_PREREQ (3, 3)
+#  define SNANF (__builtin_nansf (""))
+#  define SNAN (__builtin_nans (""))
+#  define SNANL (__builtin_nansl (""))
+# endif
+#endif
+
 /* Get the architecture specific values describing the floating-point
    evaluation.  The following symbols will get defined:
 
diff --git a/math/test-double.h b/math/test-double.h
index b9e8cd8..e172b8f 100644
--- a/math/test-double.h
+++ b/math/test-double.h
@@ -27,3 +27,4 @@
 #define TYPE_STR "double"
 #define LITM(x) x
 #define FTOSTR snprintf
+#define snan_value_MACRO SNAN
diff --git a/math/test-float.h b/math/test-float.h
index e783c09..ea096c8 100644
--- a/math/test-float.h
+++ b/math/test-float.h
@@ -28,3 +28,4 @@
 /* Use the double variants of macro constants.  */
 #define LITM(x) x
 #define FTOSTR snprintf
+#define snan_value_MACRO SNANF
diff --git a/math/test-ldouble.h b/math/test-ldouble.h
index b877711..62c9eb8 100644
--- a/math/test-ldouble.h
+++ b/math/test-ldouble.h
@@ -27,3 +27,4 @@
 #define LIT(x) (x ## L)
 #define LITM(x) x ## l
 #define FTOSTR snprintf
+#define snan_value_MACRO SNANL

-- 
Joseph S. Myers
joseph@codesourcery.com