platform_bionic/libc/bionic/c16rtomb.cpp
Elliott Hughes 2c96639eb2 Optimize the mbs fast path slightly.
From a logcat profile:
```
     |--95.06%-- convertPrintable(char*, char const*, unsigned long)
     |    |--13.95%-- [hit in function]
     |    |
     |    |--35.96%-- mbrtoc32
     |    |    |--82.72%-- [hit in function]
     |    |    |
     |    |    |--11.07%-- mbsinit
     |    |    |
     |    |    |--5.96%-- @plt
```
I think we'd assumed that mbsinit() would be inlined, but since these
functions aren't all in wchar.cpp it wasn't being. This change moves the
implementation into a (more clearly named) inline function so we can
trivially reclaim that 11%+6%.

Benchmarks before:
```
-------------------------------------------------------------------
Benchmark                         Time             CPU   Iterations
-------------------------------------------------------------------
BM_stdlib_mbrtowc_1            8.03 ns         7.95 ns     87144997
BM_stdlib_mbrtowc_2            22.0 ns         21.8 ns     32002437
BM_stdlib_mbrtowc_3            30.0 ns         29.7 ns     23517699
BM_stdlib_mbrtowc_4            37.4 ns         37.1 ns     18895204
BM_stdlib_mbstowcs_ascii     792373 ns       782484 ns          890 bytes_per_second=609.389M/s
BM_stdlib_mbstowcs_wide    15836785 ns     15678316 ns           44 bytes_per_second=30.4138M/s
```

Benchmarks after:
```
-------------------------------------------------------------------
Benchmark                         Time             CPU   Iterations
-------------------------------------------------------------------
BM_stdlib_mbrtowc_1            5.76 ns         5.72 ns    121863813
BM_stdlib_mbrtowc_2            17.1 ns         16.9 ns     41487260
BM_stdlib_mbrtowc_3            24.2 ns         24.0 ns     29141629
BM_stdlib_mbrtowc_4            30.3 ns         30.1 ns     23229291
BM_stdlib_mbstowcs_ascii     783506 ns       775389 ns          903 bytes_per_second=614.965M/s
BM_stdlib_mbstowcs_wide    12787003 ns     12672642 ns           55 bytes_per_second=37.6273M/s
```

Bug: http://b/206523398
Test: treehugger
Change-Id: If8c6c39880096ddd2cbd323c68dca82e9849ace6
2021-11-16 11:03:19 -08:00

67 lines
2.6 KiB
C++

/*
* Copyright (C) 2014 The Android Open Source Project
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <errno.h>
#include <uchar.h>
#include <wchar.h>
#include "private/bionic_mbstate.h"
static inline constexpr bool is_high_surrogate(char16_t c16) {
return c16 >= 0xd800 && c16 < 0xdc00;
}
static inline constexpr bool is_low_surrogate(char16_t c16) {
return c16 >= 0xdc00 && c16 < 0xe000;
}
size_t c16rtomb(char* s, char16_t c16, mbstate_t* ps) {
static mbstate_t __private_state;
mbstate_t* state = (ps == nullptr) ? &__private_state : ps;
if (mbstate_is_initial(state)) {
if (is_high_surrogate(c16)) {
char32_t c32 = (c16 & ~0xd800) << 10;
mbstate_set_byte(state, 3, (c32 & 0xff0000) >> 16);
mbstate_set_byte(state, 2, (c32 & 0x00ff00) >> 8);
return 0;
} else if (is_low_surrogate(c16)) {
return mbstate_reset_and_return_illegal(EINVAL, state);
} else {
return c32rtomb(s, static_cast<char32_t>(c16), state);
}
} else {
if (!is_low_surrogate(c16)) {
return mbstate_reset_and_return_illegal(EINVAL, state);
}
char32_t c32 = ((mbstate_get_byte(state, 3) << 16) |
(mbstate_get_byte(state, 2) << 8) |
(c16 & ~0xdc00)) + 0x10000;
return mbstate_reset_and_return(c32rtomb(s, c32, nullptr), state);
}
}