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Speedup to_string and to_wstring for integers using stack buffer and SSO. Reviewed as https://reviews.llvm.org/D59178 Thanks to ivafanas for all his work on this patch. 

llvm-svn: 362649
This commit is contained in:
Marshall Clow 2019-06-05 21:04:26 +00:00
parent 3975b15dba
commit 7ce7110e6d
1 changed files with 39 additions and 105 deletions
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144
libcxx/src/string.cpp
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@ -7,12 +7,14 @@
//===----------------------------------------------------------------------===// //===----------------------------------------------------------------------===//
#include "string" #include "string"
#include "charconv"
#include "cstdlib" #include "cstdlib"
#include "cwchar" #include "cwchar"
#include "cerrno" #include "cerrno"
#include "limits" #include "limits"
#include "stdexcept" #include "stdexcept"
#include <stdio.h> #include <stdio.h>
#include "__debug"
_LIBCPP_BEGIN_NAMESPACE_STD _LIBCPP_BEGIN_NAMESPACE_STD
@ -171,7 +173,7 @@ as_integer( const string& func, const wstring& s, size_t* idx, int base )
// as_float // as_float
template<typename V, typename S, typename F> template<typename V, typename S, typename F>
inline inline
V V
as_float_helper(const string& func, const S& str, size_t* idx, F f ) as_float_helper(const string& func, const S& str, size_t* idx, F f )
@ -375,11 +377,11 @@ as_string(P sprintf_like, S s, const typename S::value_type* fmt, V a)
return s; return s;
} }
template <class S, class V, bool = is_floating_point<V>::value> template <class S>
struct initial_string; struct initial_string;
template <class V, bool b> template <>
struct initial_string<string, V, b> struct initial_string<string>
{ {
string string
operator()() const operator()() const
@ -390,23 +392,8 @@ struct initial_string<string, V, b>
} }
}; };
template <class V> template <>
struct initial_string<wstring, V, false> struct initial_string<wstring>
{
wstring
operator()() const
{
const size_t n = (numeric_limits<unsigned long long>::digits / 3)
+ ((numeric_limits<unsigned long long>::digits % 3) != 0)
+ 1;
wstring s(n, wchar_t());
s.resize(s.capacity());
return s;
}
};
template <class V>
struct initial_string<wstring, V, true>
{ {
wstring wstring
operator()() const operator()() const
@ -430,95 +417,42 @@ get_swprintf()
#endif #endif
} }
template <typename S, typename V>
S i_to_string(const V v)
{
// numeric_limits::digits10 returns value less on 1 than desired for unsigned numbers.
// For example, for 1-byte unsigned value digits10 is 2 (999 can not be represented),
// so we need +1 here.
constexpr size_t bufsize = numeric_limits<V>::digits10 + 2; // +1 for minus, +1 for digits10
char buf[bufsize];
const auto res = to_chars(buf, buf + bufsize, v);
_LIBCPP_ASSERT(res.ec == errc(), "bufsize must be large enough to accomodate the value");
return S(buf, res.ptr);
}
} // unnamed namespace } // unnamed namespace
string to_string(int val) string to_string (int val) { return i_to_string< string>(val); }
{ string to_string (long val) { return i_to_string< string>(val); }
return as_string(snprintf, initial_string<string, int>()(), "%d", val); string to_string (long long val) { return i_to_string< string>(val); }
} string to_string (unsigned val) { return i_to_string< string>(val); }
string to_string (unsigned long val) { return i_to_string< string>(val); }
string to_string (unsigned long long val) { return i_to_string< string>(val); }
string to_string(unsigned val) wstring to_wstring(int val) { return i_to_string<wstring>(val); }
{ wstring to_wstring(long val) { return i_to_string<wstring>(val); }
return as_string(snprintf, initial_string<string, unsigned>()(), "%u", val); wstring to_wstring(long long val) { return i_to_string<wstring>(val); }
} wstring to_wstring(unsigned val) { return i_to_string<wstring>(val); }
wstring to_wstring(unsigned long val) { return i_to_string<wstring>(val); }
wstring to_wstring(unsigned long long val) { return i_to_string<wstring>(val); }
string to_string(long val)
{
return as_string(snprintf, initial_string<string, long>()(), "%ld", val);
}
string to_string(unsigned long val) string to_string (float val) { return as_string(snprintf, initial_string< string>()(), "%f", val); }
{ string to_string (double val) { return as_string(snprintf, initial_string< string>()(), "%f", val); }
return as_string(snprintf, initial_string<string, unsigned long>()(), "%lu", val); string to_string (long double val) { return as_string(snprintf, initial_string< string>()(), "%Lf", val); }
}
string to_string(long long val) wstring to_wstring(float val) { return as_string(get_swprintf(), initial_string<wstring>()(), L"%f", val); }
{ wstring to_wstring(double val) { return as_string(get_swprintf(), initial_string<wstring>()(), L"%f", val); }
return as_string(snprintf, initial_string<string, long long>()(), "%lld", val); wstring to_wstring(long double val) { return as_string(get_swprintf(), initial_string<wstring>()(), L"%Lf", val); }
}
string to_string(unsigned long long val)
{
return as_string(snprintf, initial_string<string, unsigned long long>()(), "%llu", val);
}
string to_string(float val)
{
return as_string(snprintf, initial_string<string, float>()(), "%f", val);
}
string to_string(double val)
{
return as_string(snprintf, initial_string<string, double>()(), "%f", val);
}
string to_string(long double val)
{
return as_string(snprintf, initial_string<string, long double>()(), "%Lf", val);
}
wstring to_wstring(int val)
{
return as_string(get_swprintf(), initial_string<wstring, int>()(), L"%d", val);
}
wstring to_wstring(unsigned val)
{
return as_string(get_swprintf(), initial_string<wstring, unsigned>()(), L"%u", val);
}
wstring to_wstring(long val)
{
return as_string(get_swprintf(), initial_string<wstring, long>()(), L"%ld", val);
}
wstring to_wstring(unsigned long val)
{
return as_string(get_swprintf(), initial_string<wstring, unsigned long>()(), L"%lu", val);
}
wstring to_wstring(long long val)
{
return as_string(get_swprintf(), initial_string<wstring, long long>()(), L"%lld", val);
}
wstring to_wstring(unsigned long long val)
{
return as_string(get_swprintf(), initial_string<wstring, unsigned long long>()(), L"%llu", val);
}
wstring to_wstring(float val)
{
return as_string(get_swprintf(), initial_string<wstring, float>()(), L"%f", val);
}
wstring to_wstring(double val)
{
return as_string(get_swprintf(), initial_string<wstring, double>()(), L"%f", val);
}
wstring to_wstring(long double val)
{
return as_string(get_swprintf(), initial_string<wstring, long double>()(), L"%Lf", val);
}
_LIBCPP_END_NAMESPACE_STD _LIBCPP_END_NAMESPACE_STD