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Refactor UTF-8 decoding to enable use of SIMD.
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@christianparpart
christianparpart committed Jul 14, 2021
1 parent a0f7291 commit 229e1d7
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Showing 7 changed files with 505 additions and 75 deletions.
200 changes: 125 additions & 75 deletions src/unicode/convert.h
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Original file line number Diff line number Diff line change
Expand Up @@ -13,12 +13,29 @@
*/
#pragma once

#include <unicode/detail/convert-common.hpp>
#include <unicode/detail/convert-naive.hpp>
#include <unicode/detail/convert-sse.hpp>
#include <unicode/detail/convert-avx512bw.hpp>
//#include <unicode/detail/convert-avx512.hpp>

#include <string_view>
#include <array>
#include <type_traits>
#include <iterator>
#include <optional>

namespace unicode::accelerator
{
#if defined(__AVX512BW__)
using optimal = avx512bw;
#elif defined(__SSE__)
using optimal = sse;
#else
using optimal = naive;
#endif
}

namespace unicode {

template <typename T> struct decoder;
Expand Down Expand Up @@ -60,7 +77,60 @@ template<> struct decoder<char> // {{{
unsigned expectedLength = 0;
unsigned currentLength = 0;

LIBUNICODE_ALIGNED_FUNC
LIBUNICODE_FORCE_INLINE
decoder_status operator()(uint8_t const* _begin,
uint8_t const* _end,
char32_t* _output)
{
return consume<accelerator::optimal>(_begin, _end, _output);
}

template <typename Accelerator>
LIBUNICODE_ALIGNED_FUNC
LIBUNICODE_FORCE_INLINE
decoder_status consume(uint8_t const* _begin,
uint8_t const* _end,
char32_t* _output)
{
uint8_t const* inputBegin = _begin;
char32_t const* outputBegin = _output;

if (!consumeUntilAligned<Accelerator>(_begin, _end, _output))
return decoder_status{
false,
static_cast<size_t>(_begin - inputBegin),
static_cast<size_t>(_output - outputBegin),
};

// Accelerated processing (128-bit aligned blocks)
while (_begin <= _end - Accelerator::alignment)
{
if (*_begin < 0x80)
detail::convertAsciiBlockOnce<Accelerator>(_begin, _output);
else if (auto const opt = consumeCodepoint(_begin, _end))
*_output++ = *opt;
else
return decoder_status{
false,
static_cast<size_t>(_begin - inputBegin),
static_cast<size_t>(_output - outputBegin),
};
}

return decoder_status{
consumeTrailingBytes(_begin, _end, _output),
static_cast<size_t>(_begin - inputBegin),
static_cast<size_t>(_output - outputBegin),
};
}

constexpr std::optional<char32_t> operator()(uint8_t _byte)
{
return consumeCodeunit(_byte);
}

constexpr std::optional<char32_t> consumeCodeunit(uint8_t _byte)
{
if (!expectedLength)
{
Expand Down Expand Up @@ -88,7 +158,10 @@ template<> struct decoder<char> // {{{
character = _byte & 0b0000'0111;
}
else
{
expectedLength = 0; // reset state
return std::nullopt; // invalid
}
}
else
{
Expand All @@ -106,88 +179,62 @@ template<> struct decoder<char> // {{{

template <
typename InputIterator,
typename InputSentinel,
std::enable_if_t<std::is_convertible_v<decltype(*std::declval<InputIterator>()), char>, int> = 0
>
constexpr std::optional<char32_t> operator()(InputIterator& _input)
constexpr std::optional<char32_t> operator()(InputIterator& _input, InputSentinel _end)
{
using std::nullopt;
return consumeCodepoint(_input, _end);
}

auto const ch0 = uint8_t(*_input++);
if (ch0 < 0x80) // 0xxx_xxxx
return static_cast<char32_t>(ch0);
template <
typename InputIterator,
typename InputSentinel,
std::enable_if_t<std::is_convertible_v<decltype(*std::declval<InputIterator>()), char>, int> = 0
>
LIBUNICODE_FORCE_INLINE
constexpr std::optional<char32_t> consumeCodepoint(InputIterator& _input, InputSentinel _end)
{
while (_input < _end)
if (auto codepoint = consumeCodeunit(*_input++))
return codepoint;

if (ch0 < 0xC0)
return nullopt;
return std::nullopt;
}

if (ch0 < 0xE0) // 110x_xxxx 10xx_xxxx
private:
template <typename Accelerator>
LIBUNICODE_FORCE_INLINE
bool consumeUntilAligned(uint8_t const*& _begin,
uint8_t const* _end,
char32_t*& _output)
{
// Consume until 128-bit aligned.
while (_begin < _end && !detail::is_aligned(_begin, Accelerator::alignment))
{
auto const ch1 = uint8_t(*_input++);
if ((ch1 >> 6) != 2)
return nullopt;
return static_cast<char32_t>((ch0 << 6) + ch1 - 0x3080);
if (auto const opt = consumeCodepoint(_begin, _end))
*_output++ = *opt;
else
return false;
}
return true;
}

if (ch0 < 0xF0) // 1110_xxxx 10xx_xxxx 10xx_xxxx
{
auto const ch1 = uint8_t(*_input++);
if (ch1 >> 6 != 2)
return nullopt;
auto const ch2 = uint8_t(*_input++);
if (ch2 >> 6 != 2)
return nullopt;
return static_cast<char32_t>((ch0 << 12) + (ch1 << 6) + ch2 - 0xE2080);
}
if (ch0 < 0xF8) // 1111_0xxx 10xx_xxxx 10xx_xxxx 10xx_xxxx
{
auto const ch1 = uint8_t(*_input++);
if (ch1 >> 6 != 2)
return nullopt;
auto const ch2 = uint8_t(*_input++);
if (ch2 >> 6 != 2)
return nullopt;
auto const ch3 = uint8_t(*_input++);
if (ch3 >> 6 != 2)
return nullopt;
return static_cast<char32_t>((ch0 << 18) + (ch1 << 12) + (ch2 << 6) + ch3 - 0x3C82080);
}
if (ch0 < 0xFC) // 1111_10xx 10xx_xxxx 10xx_xxxx 10xx_xxxx 10xx_xxxx
{
auto const ch1 = uint8_t(*_input++);
if (ch1 >> 6 != 2)
return nullopt;
auto const ch2 = uint8_t(*_input++);
if (ch2 >> 6 != 2)
return nullopt;
auto const ch3 = uint8_t(*_input++);
if (ch3 >> 6 != 2)
return nullopt;
auto const ch4 = uint8_t(*_input++);
if (ch4 >> 6 != 2)
return nullopt;
auto const a = static_cast<uint32_t>((ch0 << 24u) + (ch1 << 18u) + (ch2 << 12u) + (ch3 << 6u) + ch4);
return static_cast<char32_t>(a - 0xFA082080lu);
}
if (ch0 < 0xFE) // 1111_110x 10xx_xxxx 10xx_xxxx 10xx_xxxx 10xx_xxxx 10xx_xxxx
LIBUNICODE_FORCE_INLINE
bool consumeTrailingBytes(uint8_t const*& _begin,
uint8_t const* _end,
char32_t*& _output)
{
while (_begin < _end)
{
auto const ch1 = uint8_t(*_input++);
if (ch1 >> 6 != 2)
return nullopt;
auto const ch2 = uint8_t(*_input++);
if (ch2 >> 6 != 2)
return nullopt;
auto const ch3 = uint8_t(*_input++);
if (ch3 >> 6 != 2)
return nullopt;
auto const ch4 = uint8_t(*_input++);
if (ch4 >> 6 != 2)
return nullopt;
auto const ch5 = uint8_t(*_input++);
if (ch5 >> 6 != 2)
return nullopt;
auto const a = static_cast<uint32_t>((ch0 << 30) + (ch1 << 24) + (ch2 << 18) + (ch3 << 12) + (ch4 << 6) + ch5);
return static_cast<char32_t>(a - 0x82082080);
if (*_begin < 0x80)
*_output++ = *_begin++;
else if (auto const opt = consumeCodepoint(_begin, _end))
*_output++ = *opt;
else
return false;
}
return nullopt;
return true;
}
}; // }}}
template<> struct encoder<char16_t> // {{{
Expand Down Expand Up @@ -261,10 +308,13 @@ template<> struct encoder<char32_t> // {{{ (no-op)
template<> struct decoder<char32_t> // {{{ (no-op)
{

template <typename InputIterator>
constexpr std::optional<char32_t> operator()(InputIterator& _input)
template <typename InputIterator, typename InputSentinel>
constexpr std::optional<char32_t> operator()(InputIterator& _input, InputSentinel _end)
{
return *_input++;
if (_input != _end)
return *_input++;
else
return std::nullopt;
}
}; // }}}
template<> struct encoder<wchar_t> // {{{
Expand Down Expand Up @@ -321,7 +371,7 @@ OutputIterator convert_to(std::basic_string_view<S> _input, OutputIterator _outp
encoder<T> write{};
while (i != e)
{
auto const outChar = read(i);
auto const outChar = read(i, e);
if (outChar.has_value())
_output = write(outChar.value(), _output);
}
Expand Down
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