float.h: C2x NaN and Inf macros

C2x adds macros for NaNs and infinities to <float.h>, some of them
previously in <math.h> (and some still in <math.h> as well in C2x as
an obsolescent feature).  Add these macros to GCC's <float.h>
implementation.

This omits the macros for DFP signaling NaNs, leaving those to be
added in a separate patch.  However, it includes the _FloatN /
_FloatNx macros (conditional on __STDC_WANT_IEC_60559_TYPES_EXT__) in
the current draft version of the integration of TS 18661-3 into C2x as
an Annex.

As GCC allows duplicate macro definitions with different expansions in
system headers, it should be OK if <math.h> defines INFINITY or NAN
with a slightly different expansion (e.g. different choice of whether
there is whitespace between tokens); tests are added including
<float.h> and <math.h> in either order.  Because <float.h> uses #undef
on all macros before defining them, even with -Wsystem-headers there
could only ever be issues when <math.h> is included after <float.h>.

Bootstrapped with no regressions on x86_64-pc-linux-gnu.

gcc/
2020-11-17  Joseph Myers  <joseph@codesourcery.com>

	* ginclude/float.h (INFINITY, NAN, FLT_SNAN, DBL_SNAN, LDBL_SNAN)
	(FLT16_SNAN, FLT32_SNAN, FLT64_SNAN, FLT128_SNAN, FLT32X_SNAN)
	(FLT64X_SNAN, FLT128X_SNAN, DEC_INFINITY, DEC_NAN): New C2x
	macros.
	* doc/sourcebuild.texi (Effective-Target Keywords): Document inff.

gcc/testsuite/
2020-11-17  Joseph Myers  <joseph@codesourcery.com>

	* lib/target-supports.exp (check_effective_target_inff): New.
	* gcc.dg/c11-float-4.c, gcc.dg/c11-float-5.c,
	gcc.dg/c11-float-dfp-2.c, gcc.dg/c2x-float-2.c,
	gcc.dg/c2x-float-3.c, gcc.dg/c2x-float-4.c, gcc.dg/c2x-float-5.c,
	gcc.dg/c2x-float-6.c, gcc.dg/c2x-float-7.c, gcc.dg/c2x-float-8.c,
	gcc.dg/c2x-float-9.c, gcc.dg/c2x-float-no-dfp-3.c,
	gcc.dg/c2x-float-no-dfp-4.c, gcc.dg/dfp/c2x-float-dfp-4.c,
	gcc.dg/dfp/c2x-float-dfp-5.c, gcc.dg/dfp/c2x-float-dfp-6.c,
	gcc.dg/torture/float128-nan-floath.c,
	gcc.dg/torture/float128x-nan-floath.c,
	gcc.dg/torture/float16-nan-floath.c,
	gcc.dg/torture/float32-nan-floath.c,
	gcc.dg/torture/float32x-nan-floath.c,
	gcc.dg/torture/float64-nan-floath.c,
	gcc.dg/torture/float64x-nan-floath.c,
	gcc.dg/torture/floatn-nan-floath.h: New tests.

1 files changed, 66 insertions, 0 deletions

diff --git a/gcc/ginclude/float.h b/gcc/ginclude/float.h
index 9c4b038..7744699 100644
--- a/gcc/ginclude/float.h
+++ b/gcc/ginclude/float.h
@@ -248,6 +248,32 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 #define DBL_NORM_MAX	__DBL_NORM_MAX__
 #define LDBL_NORM_MAX	__LDBL_NORM_MAX__
 
+/* Infinity in type float, or overflow if infinity not supported.  */
+#undef INFINITY
+#define INFINITY	(__builtin_inff ())
+
+/* Quiet NaN, if supported for float.  */
+#if __FLT_HAS_QUIET_NAN__
+#undef NAN
+#define NAN		(__builtin_nanf (""))
+#endif
+
+/* Signaling NaN, if supported for each type.  All formats supported
+   by GCC support either both quiet and signaling NaNs, or neither
+   kind of NaN.  */
+#if __FLT_HAS_QUIET_NAN__
+#undef FLT_SNAN
+#define FLT_SNAN	(__builtin_nansf (""))
+#endif
+#if __DBL_HAS_QUIET_NAN__
+#undef DBL_SNAN
+#define DBL_SNAN	(__builtin_nans (""))
+#endif
+#if __LDBL_HAS_QUIET_NAN__
+#undef LDBL_SNAN
+#define LDBL_SNAN	(__builtin_nansl (""))
+#endif
+
 #endif /* C2X */
 
 #ifdef __STDC_WANT_IEC_60559_BFP_EXT__
@@ -284,6 +310,10 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 #define FLT16_DECIMAL_DIG	__FLT16_DECIMAL_DIG__
 #undef FLT16_TRUE_MIN
 #define FLT16_TRUE_MIN		__FLT16_DENORM_MIN__
+#if defined __STDC_VERSION__ && __STDC_VERSION__ > 201710L
+#undef FLT16_SNAN
+#define FLT16_SNAN	(__builtin_nansf16 (""))
+#endif /* C2X */
 #endif /* __FLT16_MANT_DIG__.  */
 
 #ifdef __FLT32_MANT_DIG__
@@ -309,6 +339,10 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 #define FLT32_DECIMAL_DIG	__FLT32_DECIMAL_DIG__
 #undef FLT32_TRUE_MIN
 #define FLT32_TRUE_MIN		__FLT32_DENORM_MIN__
+#if defined __STDC_VERSION__ && __STDC_VERSION__ > 201710L
+#undef FLT32_SNAN
+#define FLT32_SNAN	(__builtin_nansf32 (""))
+#endif /* C2X */
 #endif /* __FLT32_MANT_DIG__.  */
 
 #ifdef __FLT64_MANT_DIG__
@@ -334,6 +368,10 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 #define FLT64_DECIMAL_DIG	__FLT64_DECIMAL_DIG__
 #undef FLT64_TRUE_MIN
 #define FLT64_TRUE_MIN		__FLT64_DENORM_MIN__
+#if defined __STDC_VERSION__ && __STDC_VERSION__ > 201710L
+#undef FLT64_SNAN
+#define FLT64_SNAN	(__builtin_nansf64 (""))
+#endif /* C2X */
 #endif /* __FLT64_MANT_DIG__.  */
 
 #ifdef __FLT128_MANT_DIG__
@@ -359,6 +397,10 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 #define FLT128_DECIMAL_DIG	__FLT128_DECIMAL_DIG__
 #undef FLT128_TRUE_MIN
 #define FLT128_TRUE_MIN		__FLT128_DENORM_MIN__
+#if defined __STDC_VERSION__ && __STDC_VERSION__ > 201710L
+#undef FLT128_SNAN
+#define FLT128_SNAN	(__builtin_nansf128 (""))
+#endif /* C2X */
 #endif /* __FLT128_MANT_DIG__.  */
 
 #ifdef __FLT32X_MANT_DIG__
@@ -384,6 +426,10 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 #define FLT32X_DECIMAL_DIG	__FLT32X_DECIMAL_DIG__
 #undef FLT32X_TRUE_MIN
 #define FLT32X_TRUE_MIN		__FLT32X_DENORM_MIN__
+#if defined __STDC_VERSION__ && __STDC_VERSION__ > 201710L
+#undef FLT32X_SNAN
+#define FLT32X_SNAN	(__builtin_nansf32x (""))
+#endif /* C2X */
 #endif /* __FLT32X_MANT_DIG__.  */
 
 #ifdef __FLT64X_MANT_DIG__
@@ -409,6 +455,10 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 #define FLT64X_DECIMAL_DIG	__FLT64X_DECIMAL_DIG__
 #undef FLT64X_TRUE_MIN
 #define FLT64X_TRUE_MIN		__FLT64X_DENORM_MIN__
+#if defined __STDC_VERSION__ && __STDC_VERSION__ > 201710L
+#undef FLT64X_SNAN
+#define FLT64X_SNAN	(__builtin_nansf64x (""))
+#endif /* C2X */
 #endif /* __FLT64X_MANT_DIG__.  */
 
 #ifdef __FLT128X_MANT_DIG__
@@ -434,6 +484,10 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 #define FLT128X_DECIMAL_DIG	__FLT128X_DECIMAL_DIG__
 #undef FLT128X_TRUE_MIN
 #define FLT128X_TRUE_MIN	__FLT128X_DENORM_MIN__
+#if defined __STDC_VERSION__ && __STDC_VERSION__ > 201710L
+#undef FLT128X_SNAN
+#define FLT128X_SNAN	(__builtin_nansf128x (""))
+#endif /* C2X */
 #endif /* __FLT128X_MANT_DIG__.  */
 
 #endif /* __STDC_WANT_IEC_60559_TYPES_EXT__.  */
@@ -537,6 +591,18 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 
 #endif /* __STDC_WANT_IEC_60559_DFP_EXT__ || C2X.  */
 
+#if defined __STDC_VERSION__ && __STDC_VERSION__ > 201710L
+
+/* Infinity in type _Decimal32.  */
+#undef DEC_INFINITY
+#define DEC_INFINITY	(__builtin_infd32 ())
+
+/* Quiet NaN in type _Decimal32.  */
+#undef DEC_NAN
+#define DEC_NAN		(__builtin_nand32 (""))
+
+#endif /* C2X */
+
 #endif /* __DEC32_MANT_DIG__ */
 
 #endif /* _FLOAT_H___ */