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* [gcc r12-6649] libstdc++: Use fast_float in std::from_chars for binary32/64
@ 2022-01-17 19:33 Patrick Palka
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From: Patrick Palka @ 2022-01-17 19:33 UTC (permalink / raw)
To: gcc-cvs, libstdc++-cvs
https://gcc.gnu.org/g:490e23032baaece71f2ec09fa1805064b150fbc2
commit r12-6649-g490e23032baaece71f2ec09fa1805064b150fbc2
Author: Patrick Palka <ppalka@redhat.com>
Date: Mon Jan 17 14:33:12 2022 -0500
libstdc++: Use fast_float in std::from_chars for binary32/64
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.
Diff:
---
libstdc++-v3/src/c++17/floating_from_chars.cc | 31 +++++++++++++++++++++++----
1 file changed, 27 insertions(+), 4 deletions(-)
diff --git a/libstdc++-v3/src/c++17/floating_from_chars.cc b/libstdc++-v3/src/c++17/floating_from_chars.cc
index 3ad5b409da7..3158a3a96d3 100644
--- a/libstdc++-v3/src/c++17/floating_from_chars.cc
+++ b/libstdc++-v3/src/c++17/floating_from_chars.cc
@@ -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
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