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Call CRT wmemcmp/wmemchr when possible in char_traits for better performance #4873

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merged 6 commits into from
Aug 8, 2024
Merged

Call CRT wmemcmp/wmemchr when possible in char_traits for better performance #4873

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c08decd
Update __msvc_string_view.hpp
mcfi Aug 2, 2024
b334119
Update __msvc_string_view.hpp
mcfi Aug 2, 2024
394eea5
Update __msvc_string_view.hpp
mcfi Aug 2, 2024
d9c1790
Activate optimization for exactly C++17.
StephanTLavavej Aug 2, 2024
ba5b17d
Activate optimization for char16_t, unify wmemcmp/wmemchr calls.
StephanTLavavej Aug 2, 2024
82d2eff
Also make length() fall through to wcslen().
StephanTLavavej Aug 2, 2024
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16 changes: 16 additions & 0 deletions stl/inc/__msvc_string_view.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -221,7 +221,15 @@ struct _WChar_traits : private _Char_traits<_Elem, unsigned short> {
// compare [_First1, _First1 + _Count) with [_First2, ...)
#if _HAS_CXX17
if constexpr (is_same_v<_Elem, wchar_t>) {
#if _HAS_CXX20
if (_STD _Is_constant_evaluated()) {
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return __builtin_wmemcmp(_First1, _First2, _Count);
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} else {
return _CSTD wmemcmp(_First1, _First2, _Count);
}
#else // ^^^ _HAS_CXX20 / !_HAS_CXX20 vvv
return __builtin_wmemcmp(_First1, _First2, _Count);
#endif // ^^^ !_HAS_CXX20 ^^^
} else {
return _Primary_char_traits::compare(_First1, _First2, _Count);
}
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Expand Down Expand Up @@ -249,7 +257,15 @@ struct _WChar_traits : private _Char_traits<_Elem, unsigned short> {
// look for _Ch in [_First, _First + _Count)
#if _HAS_CXX17
if constexpr (is_same_v<_Elem, wchar_t>) {
#if _HAS_CXX20
if (_STD _Is_constant_evaluated()) {
return __builtin_wmemchr(_First, _Ch, _Count);
} else {
return _CSTD wmemchr(_First, _Ch, _Count);
}
#else // ^^^ _HAS_CXX20 / !_HAS_CXX20 vvv
return __builtin_wmemchr(_First, _Ch, _Count);
#endif // ^^^ !_HAS_CXX20 ^^^
} else {
return _Primary_char_traits::find(_First, _Count, _Ch);
}
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