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LibRegex: Pull out the first compare to avoid unnecessary execution

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This adds a fast-path to drop view indices we know will not match
immediately without going through the regex VM.
This commit is contained in:
Ali Mohammad Pur 2025-04-15 21:32:26 +02:00 • committed by Andreas Kling
parent 76f5dce3db
commit 446a453719
Notes: github-actions[bot] 2025-04-18 15:10:31 +00:00
4 changed files with 250 additions and 117 deletions
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35
Libraries/LibRegex/RegexMatcher.cpp
View file

@ -4,6 +4,7 @@
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/BinarySearch.h>
#include <AK/BumpAllocator.h>
#include <AK/ByteString.h>
#include <AK/Debug.h>
@ -208,6 +209,23 @@ RegexResult Matcher<Parser>::match(Vector<RegexStringView> const& views, Optiona
auto single_match_only = input.regex_options.has_flag_set(AllFlags::SingleMatch);
auto only_start_of_line = m_pattern->parser_result.optimization_data.only_start_of_line && !input.regex_options.has_flag_set(AllFlags::Multiline);
auto compare_range = [insensitive = input.regex_options & AllFlags::Insensitive](auto needle, CharRange range) {
auto upper_case_needle = needle;
auto lower_case_needle = needle;
if (insensitive) {
upper_case_needle = to_ascii_uppercase(needle);
lower_case_needle = to_ascii_lowercase(needle);
}
if (lower_case_needle >= range.from && lower_case_needle <= range.to)
return 0;
if (upper_case_needle >= range.from && upper_case_needle <= range.to)
return 0;
if (lower_case_needle > range.to || upper_case_needle > range.to)
return 1;
return -1;
};
for (auto const& view : views) {
if (lines_to_skip != 0) {
++input.line;
@ -253,19 +271,26 @@ RegexResult Matcher<Parser>::match(Vector<RegexStringView> const& views, Optiona
}
for (; view_index <= view_length; ++view_index) {
if (view_index == view_length && input.regex_options.has_flag_set(AllFlags::Multiline))
break;
if (view_index == view_length) {
if (input.regex_options.has_flag_set(AllFlags::Multiline))
break;
}
auto& match_length_minimum = m_pattern->parser_result.match_length_minimum;
// FIXME: More performant would be to know the remaining minimum string
// length needed to match from the current position onwards within
// the vm. Add new OpCode for MinMatchLengthFromSp with the value of
// the remaining string length from the current path. The value though
// has to be filled in reverse. That implies a second run over bytecode
// after generation has finished.
auto const match_length_minimum = m_pattern->parser_result.match_length_minimum;
if (match_length_minimum && match_length_minimum > view_length - view_index)
break;
if (auto& starting_ranges = m_pattern->parser_result.optimization_data.starting_ranges; !starting_ranges.is_empty()) {
if (!binary_search(starting_ranges, input.view.code_unit_at(view_index), nullptr, compare_range))
goto done_matching;
}
input.column = match_count;
input.match_index = match_count;
@ -274,8 +299,7 @@ RegexResult Matcher<Parser>::match(Vector<RegexStringView> const& views, Optiona
state.instruction_position = 0;
state.repetition_marks.clear();
auto success = execute(input, state, operations);
if (success) {
if (execute(input, state, operations)) {
succeeded = true;
if (input.regex_options.has_flag_set(AllFlags::MatchNotEndOfLine) && state.string_position == input.view.length()) {
@ -315,6 +339,7 @@ RegexResult Matcher<Parser>::match(Vector<RegexStringView> const& views, Optiona
break;
}
done_matching:
if (!continue_search || only_start_of_line)
break;
}