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libstdc++: Use fast_float in std::from_chars for binary32/64

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This makes our std::from_chars implementation use fast_float for decimal
parsing of binary32/64 numbers.  For other floating-point formats we
still use the fallback implementation that goes through the strtod family
of functions.

libstdc++-v3/ChangeLog:

	* src/c++17/floating_from_chars.cc: (USE_LIB_FAST_FLOAT):
	Conditionally define, and use it to conditionally include
	fast_float.
	(from_chars): Use fast_float for float and double when
	USE_LIB_FAST_FLOAT.
This commit is contained in:
Patrick Palka
2022-01-17 14:33:12 -05:00
parent 40b0d4472a
commit 490e23032b
1 changed files with 27 additions and 4 deletions
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31
libstdc++-v3/src/c++17/floating_from_chars.cc
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@@ -35,6 +35,7 @@
#include <string>
#include <memory_resource>
#include <cfenv>
#include <cfloat>
#include <cmath>
#include <cstdlib>
#include <cstring>
@@ -53,6 +54,18 @@
extern "C" __ieee128 __strtoieee128(const char*, char**);
#endif
#if _GLIBCXX_FLOAT_IS_IEEE_BINARY32 && _GLIBCXX_DOUBLE_IS_IEEE_BINARY64
# define USE_LIB_FAST_FLOAT 1
#endif
#if USE_LIB_FAST_FLOAT
# define FASTFLOAT_DEBUG_ASSERT __glibcxx_assert
namespace
{
# include "fast_float/fast_float.h"
} // anon namespace
#endif
#if _GLIBCXX_HAVE_USELOCALE
namespace std _GLIBCXX_VISIBILITY(default)
{
@@ -773,8 +786,12 @@ from_chars(const char* first, const char* last, float& value,
#if _GLIBCXX_FLOAT_IS_IEEE_BINARY32 && _GLIBCXX_DOUBLE_IS_IEEE_BINARY64
if (fmt == chars_format::hex)
return __floating_from_chars_hex(first, last, value);
#endif
else
{
static_assert(USE_LIB_FAST_FLOAT);
return fast_float::from_chars(first, last, value, fmt);
}
#else
errc ec = errc::invalid_argument;
#if _GLIBCXX_USE_CXX11_ABI
buffer_resource mr;
@@ -795,6 +812,7 @@ from_chars(const char* first, const char* last, float& value,
fmt = chars_format{};
}
return make_result(first, len, fmt, ec);
#endif
}
from_chars_result
@@ -804,8 +822,12 @@ from_chars(const char* first, const char* last, double& value,
#if _GLIBCXX_FLOAT_IS_IEEE_BINARY32 && _GLIBCXX_DOUBLE_IS_IEEE_BINARY64
if (fmt == chars_format::hex)
return __floating_from_chars_hex(first, last, value);
#endif
else
{
static_assert(USE_LIB_FAST_FLOAT);
return fast_float::from_chars(first, last, value, fmt);
}
#else
errc ec = errc::invalid_argument;
#if _GLIBCXX_USE_CXX11_ABI
buffer_resource mr;
@@ -826,6 +848,7 @@ from_chars(const char* first, const char* last, double& value,
fmt = chars_format{};
}
return make_result(first, len, fmt, ec);
#endif
}
from_chars_result