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libstdc++: Small extended float support tweaks

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The following patch
1) enables the std::float128_t overloads for x86 with glibc 2.26+
2) makes std::nextafter(std::float16_t, std::float16_t) and
   std::nextafter(std::bfloat16_t, std::bfloat16_t) constexpr
3) adds (small) testsuite coverage for that

2022-10-21  Jakub Jelinek  <jakub@redhat.com>

	* config/os/gnu-linux/os_defines.h (_GLIBCXX_HAVE_FLOAT128_MATH):
	Uncomment.
	* include/c_global/cmath (nextafter(_Float16, _Float16)): Make it constexpr.
	If std::__is_constant_evaluated() call __builtin_nextafterf16.
	(nextafter(__gnu_cxx::__bfloat16_t, __gnu_cxx::__bfloat16_t)): Similarly
	but call __builtin_nextafterf16b.
	* testsuite/26_numerics/headers/cmath/nextafter_c++23.cc (test): Add
	static assertions to test constexpr nextafter.
This commit is contained in:
Jakub Jelinek 2022-10-31 16:47:23 +01:00
parent 1b07d37476
commit cbf56503d5
3 changed files with 9 additions and 3 deletions
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2
libstdc++-v3/config/os/gnu-linux/os_defines.h
View file

@ -57,7 +57,7 @@
|| (defined(__powerpc__) && defined(_ARCH_PWR8) \
&& defined(__LITTLE_ENDIAN__) && (_CALL_ELF == 2) \
&& defined(__FLOAT128__)))
//# define _GLIBCXX_HAVE_FLOAT128_MATH 1
# define _GLIBCXX_HAVE_FLOAT128_MATH 1
#endif
#if __GLIBC_PREREQ(2, 27)

8
libstdc++-v3/include/c_global/cmath
View file

@ -2755,9 +2755,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
nearbyint(_Float16 __x)
{ return _Float16(__builtin_nearbyintf(__x)); }
inline _Float16
constexpr _Float16
nextafter(_Float16 __x, _Float16 __y)
{
if (std::__is_constant_evaluated())
return __builtin_nextafterf16(__x, __y);
#ifdef __INT16_TYPE__
using __float16_int_type = __INT16_TYPE__;
#else
@ -3471,9 +3473,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
nearbyint(__gnu_cxx::__bfloat16_t __x)
{ return __gnu_cxx::__bfloat16_t(__builtin_nearbyintf(__x)); }
inline __gnu_cxx::__bfloat16_t
constexpr __gnu_cxx::__bfloat16_t
nextafter(__gnu_cxx::__bfloat16_t __x, __gnu_cxx::__bfloat16_t __y)
{
if (std::__is_constant_evaluated())
return __builtin_nextafterf16b(__x, __y);
#ifdef __INT16_TYPE__
using __bfloat16_int_type = __INT16_TYPE__;
#else

2
libstdc++-v3/testsuite/26_numerics/headers/cmath/nextafter_c++23.cc
View file

@ -100,6 +100,8 @@ test ()
VERIFY(std::fpclassify(t36) == FP_NAN);
T t37 = std::nextafter(T(-0.0), T());
VERIFY(t37 == T() && !std::signbit(t37));
static_assert(std::nextafter(T(1.0), T(2.0)) > T(1.0));
static_assert(std::nextafter(std::nextafter(T(1.0), T(5.0)), T(0.0)) == T(1.0));
}
int