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Simplify control flow in _Traits_find_MEOW_not_of #5006

Merged
merged 11 commits into from
Oct 12, 2024
Merged

Simplify control flow in _Traits_find_MEOW_not_of #5006

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703982f
Replace unnecessarily confusing `break`s with immediate `return`s.
StephanTLavavej Oct 9, 2024
e2918bb
Add a `return` instead of relying on fall-through.
StephanTLavavej Oct 9, 2024
e968071
Flip `!_Matches._Mark` tests.
StephanTLavavej Oct 9, 2024
d892ca8
Transform "call self with `_Special=false`" to fall-through.
StephanTLavavej Oct 9, 2024
d11acd0
Extract `_Elem`.
StephanTLavavej Oct 9, 2024
5b2d81a
Extract `_Hay_start`, `_Hay_end`.
StephanTLavavej Oct 10, 2024
e22295f
Fuse `bool _Special` into its usage.
StephanTLavavej Oct 10, 2024
8d902d9
Use early returns to reduce indentation
CaseyCarter Oct 10, 2024
9a248c3
Revert changes to `_Traits_find_last_of`
CaseyCarter Oct 10, 2024
f7a8c35
Elide dead returns
CaseyCarter Oct 10, 2024
e801c71
Merge branch 'main' into transform-find-meow-of
StephanTLavavej Oct 12, 2024
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208 changes: 112 additions & 96 deletions stl/inc/__msvc_string_view.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -628,15 +628,17 @@ constexpr size_t _Traits_rfind(_In_reads_(_Hay_size) const _Traits_ptr_t<_Traits
return (_STD min)(_Start_at, _Hay_size); // empty string always matches
}

if (_Needle_size <= _Hay_size) { // room for match, look for it
for (auto _Match_try = _Haystack + (_STD min)(_Start_at, _Hay_size - _Needle_size);; --_Match_try) {
if (_Traits::eq(*_Match_try, *_Needle) && _Traits::compare(_Match_try, _Needle, _Needle_size) == 0) {
return static_cast<size_t>(_Match_try - _Haystack); // found a match
}
if (_Needle_size > _Hay_size) { // no room for match
return static_cast<size_t>(-1);
}

if (_Match_try == _Haystack) {
break; // at beginning, no more chance for match
}
for (auto _Match_try = _Haystack + (_STD min)(_Start_at, _Hay_size - _Needle_size);; --_Match_try) {
if (_Traits::eq(*_Match_try, *_Needle) && _Traits::compare(_Match_try, _Needle, _Needle_size) == 0) {
return static_cast<size_t>(_Match_try - _Haystack); // found a match
}

if (_Match_try == _Haystack) {
return static_cast<size_t>(-1); // at beginning, no more chance for match
}
}

Expand All @@ -647,15 +649,18 @@ template <class _Traits>
constexpr size_t _Traits_rfind_ch(_In_reads_(_Hay_size) const _Traits_ptr_t<_Traits> _Haystack, const size_t _Hay_size,
const size_t _Start_at, const _Traits_ch_t<_Traits> _Ch) noexcept {
// search [_Haystack, _Haystack + _Hay_size) for _Ch before _Start_at
if (_Hay_size != 0) { // room for match, look for it
for (auto _Match_try = _Haystack + (_STD min)(_Start_at, _Hay_size - 1);; --_Match_try) {
if (_Traits::eq(*_Match_try, _Ch)) {
return static_cast<size_t>(_Match_try - _Haystack); // found a match
}

if (_Match_try == _Haystack) {
break; // at beginning, no more chance for match
}
if (_Hay_size == 0) { // no room for match
return static_cast<size_t>(-1);
}

for (auto _Match_try = _Haystack + (_STD min)(_Start_at, _Hay_size - 1);; --_Match_try) {
if (_Traits::eq(*_Match_try, _Ch)) {
return static_cast<size_t>(_Match_try - _Haystack); // found a match
}

if (_Match_try == _Haystack) {
return static_cast<size_t>(-1); // at beginning, no more chance for match
}
}

Expand Down Expand Up @@ -714,62 +719,64 @@ class _String_bitmap<_Elem, false> { // _String_bitmap for wchar_t/unsigned shor
bool _Matches[256] = {};
};

template <class _Traits, bool _Special = _Is_implementation_handled_char_traits<_Traits>>
template <class _Traits>
constexpr size_t _Traits_find_first_of(_In_reads_(_Hay_size) const _Traits_ptr_t<_Traits> _Haystack,
const size_t _Hay_size, const size_t _Start_at, _In_reads_(_Needle_size) const _Traits_ptr_t<_Traits> _Needle,
const size_t _Needle_size) noexcept {
// in [_Haystack, _Haystack + _Hay_size), look for one of [_Needle, _Needle + _Needle_size), at/after _Start_at
if (_Needle_size != 0 && _Start_at < _Hay_size) { // room for match, look for it
const auto _Hay_start = _Haystack + _Start_at;
const auto _Hay_end = _Haystack + _Hay_size;
if (_Needle_size == 0 || _Start_at >= _Hay_size) { // no match possible
return static_cast<size_t>(-1);
}

if constexpr (_Special) {
if (!_STD _Is_constant_evaluated()) {
using _Elem = typename _Traits::char_type;
const auto _Hay_start = _Haystack + _Start_at;
const auto _Hay_end = _Haystack + _Hay_size;

if constexpr (_Is_implementation_handled_char_traits<_Traits>) {
if (!_STD _Is_constant_evaluated()) {
using _Elem = typename _Traits::char_type;

#if _USE_STD_VECTOR_ALGORITHMS
const bool _Try_vectorize = _Hay_size - _Start_at > _Threshold_find_first_of;
const bool _Try_vectorize = _Hay_size - _Start_at > _Threshold_find_first_of;

// Additional condition for when the vectorization outperforms the table lookup
const bool _Use_bitmap = !_Try_vectorize || (sizeof(_Elem) > 1 && sizeof(_Elem) * _Needle_size > 16);
// Additional condition for when the vectorization outperforms the table lookup
const bool _Use_bitmap = !_Try_vectorize || (sizeof(_Elem) > 1 && sizeof(_Elem) * _Needle_size > 16);
#else
const bool _Use_bitmap = true;
const bool _Use_bitmap = true;
#endif // _USE_STD_VECTOR_ALGORITHMS

if (_Use_bitmap) {
_String_bitmap<_Elem> _Matches;
if (_Use_bitmap) {
_String_bitmap<_Elem> _Matches;

if (_Matches._Mark(_Needle, _Needle + _Needle_size)) {
for (auto _Match_try = _Hay_start; _Match_try < _Hay_end; ++_Match_try) {
if (_Matches._Match(*_Match_try)) {
return static_cast<size_t>(_Match_try - _Haystack); // found a match
}
if (_Matches._Mark(_Needle, _Needle + _Needle_size)) {
for (auto _Match_try = _Hay_start; _Match_try < _Hay_end; ++_Match_try) {
if (_Matches._Match(*_Match_try)) {
return static_cast<size_t>(_Match_try - _Haystack); // found a match
}
return static_cast<size_t>(-1); // no match
}

// couldn't put one of the characters into the bitmap, fall back to vectorized or serial algorithms
return static_cast<size_t>(-1); // no match
}

// couldn't put one of the characters into the bitmap, fall back to vectorized or serial algorithms
}

#if _USE_STD_VECTOR_ALGORITHMS
if (_Try_vectorize) {
const _Traits_ptr_t<_Traits> _Found =
_STD _Find_first_of_vectorized(_Hay_start, _Hay_end, _Needle, _Needle + _Needle_size);

if (_Found != _Hay_end) {
return static_cast<size_t>(_Found - _Haystack); // found a match
} else {
return static_cast<size_t>(-1); // no match
}
if (_Try_vectorize) {
const _Traits_ptr_t<_Traits> _Found =
_STD _Find_first_of_vectorized(_Hay_start, _Hay_end, _Needle, _Needle + _Needle_size);

if (_Found != _Hay_end) {
return static_cast<size_t>(_Found - _Haystack); // found a match
} else {
return static_cast<size_t>(-1); // no match
}
#endif // _USE_STD_VECTOR_ALGORITHMS
}
#endif // _USE_STD_VECTOR_ALGORITHMS
}
}

for (auto _Match_try = _Hay_start; _Match_try < _Hay_end; ++_Match_try) {
if (_Traits::find(_Needle, _Needle_size, *_Match_try)) {
return static_cast<size_t>(_Match_try - _Haystack); // found a match
}
for (auto _Match_try = _Hay_start; _Match_try < _Hay_end; ++_Match_try) {
if (_Traits::find(_Needle, _Needle_size, *_Match_try)) {
return static_cast<size_t>(_Match_try - _Haystack); // found a match
}
}

Expand Down Expand Up @@ -814,33 +821,36 @@ constexpr size_t _Traits_find_last_of(_In_reads_(_Hay_size) const _Traits_ptr_t<
return static_cast<size_t>(-1); // no match
}

template <class _Traits, bool _Special = _Is_implementation_handled_char_traits<_Traits>>
template <class _Traits>
constexpr size_t _Traits_find_first_not_of(_In_reads_(_Hay_size) const _Traits_ptr_t<_Traits> _Haystack,
const size_t _Hay_size, const size_t _Start_at, _In_reads_(_Needle_size) const _Traits_ptr_t<_Traits> _Needle,
const size_t _Needle_size) noexcept {
// in [_Haystack, _Haystack + _Hay_size), look for none of [_Needle, _Needle + _Needle_size), at/after _Start_at
if (_Start_at < _Hay_size) { // room for match, look for it
if constexpr (_Special) {
_String_bitmap<typename _Traits::char_type> _Matches;
if (!_Matches._Mark(_Needle, _Needle + _Needle_size)) { // couldn't put one of the characters into the
// bitmap, fall back to the serial algorithm
return _Traits_find_first_not_of<_Traits, false>(
_Haystack, _Hay_size, _Start_at, _Needle, _Needle_size);
}
if (_Start_at >= _Hay_size) { // no room for match
return static_cast<size_t>(-1);
}

const auto _Hay_start = _Haystack + _Start_at;
const auto _Hay_end = _Haystack + _Hay_size;

const auto _End = _Haystack + _Hay_size;
for (auto _Match_try = _Haystack + _Start_at; _Match_try < _End; ++_Match_try) {
if constexpr (_Is_implementation_handled_char_traits<_Traits>) {
using _Elem = typename _Traits::char_type;
_String_bitmap<_Elem> _Matches;
if (_Matches._Mark(_Needle, _Needle + _Needle_size)) {
for (auto _Match_try = _Hay_start; _Match_try < _Hay_end; ++_Match_try) {
if (!_Matches._Match(*_Match_try)) {
return static_cast<size_t>(_Match_try - _Haystack); // found a match
}
}
} else {
const auto _End = _Haystack + _Hay_size;
for (auto _Match_try = _Haystack + _Start_at; _Match_try < _End; ++_Match_try) {
if (!_Traits::find(_Needle, _Needle_size, *_Match_try)) {
return static_cast<size_t>(_Match_try - _Haystack); // found a match
}
}
return static_cast<size_t>(-1); // no match
}

// couldn't put one of the characters into the bitmap, fall back to the serial algorithm
}

for (auto _Match_try = _Hay_start; _Match_try < _Hay_end; ++_Match_try) {
if (!_Traits::find(_Needle, _Needle_size, *_Match_try)) {
return static_cast<size_t>(_Match_try - _Haystack); // found a match
}
}

Expand All @@ -863,38 +873,42 @@ constexpr size_t _Traits_find_not_ch(_In_reads_(_Hay_size) const _Traits_ptr_t<_
return static_cast<size_t>(-1); // no match
}

template <class _Traits, bool _Special = _Is_implementation_handled_char_traits<_Traits>>
template <class _Traits>
constexpr size_t _Traits_find_last_not_of(_In_reads_(_Hay_size) const _Traits_ptr_t<_Traits> _Haystack,
const size_t _Hay_size, const size_t _Start_at, _In_reads_(_Needle_size) const _Traits_ptr_t<_Traits> _Needle,
const size_t _Needle_size) noexcept {
// in [_Haystack, _Haystack + _Hay_size), look for none of [_Needle, _Needle + _Needle_size), before _Start_at
if (_Hay_size != 0) { // worth searching, do it
if constexpr (_Special) {
_String_bitmap<typename _Traits::char_type> _Matches;
if (!_Matches._Mark(_Needle, _Needle + _Needle_size)) { // couldn't put one of the characters into the
// bitmap, fall back to the serial algorithm
return _Traits_find_last_not_of<_Traits, false>(_Haystack, _Hay_size, _Start_at, _Needle, _Needle_size);
}
if (_Hay_size == 0) { // no match possible
return static_cast<size_t>(-1);
}

for (auto _Match_try = _Haystack + (_STD min)(_Start_at, _Hay_size - 1);; --_Match_try) {
const auto _Hay_start = (_STD min)(_Start_at, _Hay_size - 1);

if constexpr (_Is_implementation_handled_char_traits<_Traits>) {
using _Elem = typename _Traits::char_type;
_String_bitmap<_Elem> _Matches;
if (_Matches._Mark(_Needle, _Needle + _Needle_size)) {
for (auto _Match_try = _Haystack + _Hay_start;; --_Match_try) {
if (!_Matches._Match(*_Match_try)) {
return static_cast<size_t>(_Match_try - _Haystack); // found a match
}

if (_Match_try == _Haystack) {
break; // at beginning, no more chance for match
return static_cast<size_t>(-1); // at beginning, no more chance for match
}
}
} else {
for (auto _Match_try = _Haystack + (_STD min)(_Start_at, _Hay_size - 1);; --_Match_try) {
if (!_Traits::find(_Needle, _Needle_size, *_Match_try)) {
return static_cast<size_t>(_Match_try - _Haystack); // found a match
}
}

if (_Match_try == _Haystack) {
break; // at beginning, no more chance for match
}
}
// couldn't put one of the characters into the bitmap, fall back to the serial algorithm
}

for (auto _Match_try = _Haystack + _Hay_start;; --_Match_try) {
if (!_Traits::find(_Needle, _Needle_size, *_Match_try)) {
return static_cast<size_t>(_Match_try - _Haystack); // found a match
}

if (_Match_try == _Haystack) {
return static_cast<size_t>(-1); // at beginning, no more chance for match
}
}

Expand All @@ -905,15 +919,17 @@ template <class _Traits>
constexpr size_t _Traits_rfind_not_ch(_In_reads_(_Hay_size) const _Traits_ptr_t<_Traits> _Haystack,
const size_t _Hay_size, const size_t _Start_at, const _Traits_ch_t<_Traits> _Ch) noexcept {
// search [_Haystack, _Haystack + _Hay_size) for any value other than _Ch before _Start_at
if (_Hay_size != 0) { // room for match, look for it
for (auto _Match_try = _Haystack + (_STD min)(_Start_at, _Hay_size - 1);; --_Match_try) {
if (!_Traits::eq(*_Match_try, _Ch)) {
return static_cast<size_t>(_Match_try - _Haystack); // found a match
}
if (_Hay_size == 0) { // no room for match
return static_cast<size_t>(-1);
}

if (_Match_try == _Haystack) {
break; // at beginning, no more chance for match
}
for (auto _Match_try = _Haystack + (_STD min)(_Start_at, _Hay_size - 1);; --_Match_try) {
if (!_Traits::eq(*_Match_try, _Ch)) {
return static_cast<size_t>(_Match_try - _Haystack); // found a match
}

if (_Match_try == _Haystack) {
return static_cast<size_t>(-1); // at beginning, no more chance for match
}
}

Expand Down