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LibJS: Add a localCompare() fast path for ASCII strings

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When comparing ASCII strings we now use our own collation tables rather
than invoking ICU.
This commit is contained in:
Tim Ledbetter 2025-11-23 20:54:34 +00:00 • committed by Jelle Raaijmakers
parent f268458aa4
commit 999656a7d3
Notes: github-actions[bot] 2025-11-23 23:23:19 +00:00
1 changed files with 61 additions and 0 deletions
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61
Libraries/LibJS/Runtime/StringPrototype.cpp
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@ -547,6 +547,62 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::last_index_of)
return *result;
}
// clang-format off
static constexpr AK::Array<u8, 128> ascii_collation_primary_weights {
0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 4, 5, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
6, 12, 16, 28, 38, 29, 27, 15, 17, 18, 24, 32, 9, 8, 14, 25,
39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 11, 10, 33, 34, 35, 13,
23, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63,
64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 19, 26, 20, 31, 7,
30, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63,
64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 21, 36, 22, 37, 0,
};
static constexpr AK::Array<u8, 128> ascii_collation_tertiary_weights {
0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0,
};
// clang-format on
static Optional<int> try_fast_ascii_string_compare(StringView a, StringView b)
{
auto len = min(a.length(), b.length());
for (size_t i = 0; i < len; i++) {
auto a_character = a[i];
auto b_character = b[i];
if (a_character != b_character) {
auto a_primary_weight = ascii_collation_primary_weights[a_character];
// We bail for control characters so that we don't have to compare secondary weights.
if (a_primary_weight == 0)
return {};
auto b_primary_weight = ascii_collation_primary_weights[b_character];
if (b_primary_weight == 0)
return {};
if (a_primary_weight != b_primary_weight)
return a_primary_weight < b_primary_weight ? -1 : 1;
if (a.length() != b.length())
return a.length() < b.length() ? -1 : 1;
auto a_tertiary_weight = ascii_collation_tertiary_weights[a_character];
auto b_tertiary_weight = ascii_collation_tertiary_weights[b_character];
if (a_tertiary_weight != b_tertiary_weight)
return a_tertiary_weight < b_tertiary_weight ? -1 : 1;
}
}
if (a.length() != b.length())
return a.length() < b.length() ? -1 : 1;
return 0;
}
// 22.1.3.12 String.prototype.localeCompare ( that [ , reserved1 [ , reserved2 ] ] ), https://tc39.es/ecma262/#sec-string.prototype.localecompare
// 20.1.1 String.prototype.localeCompare ( that [ , locales [ , options ] ] ), https://tc39.es/ecma402/#sup-String.prototype.localeCompare
JS_DEFINE_NATIVE_FUNCTION(StringPrototype::locale_compare)
@ -572,6 +628,11 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::locale_compare)
// OPTIMIZATION: Identical strings are equal with the default options.
if (string == that_value)
return Value(0);
// OPTIMIZATION: If both strings are ASCII, use a comparison that doesn't invoke ICU.
if (string.has_ascii_storage() && that_value.has_ascii_storage()) {
if (auto maybe_result = try_fast_ascii_string_compare(string.ascii_view(), that_value.ascii_view()); maybe_result.has_value())
return Value(*maybe_result);
}
collator = realm.intrinsics().default_collator();
} else {
collator = TRY(construct(vm, realm.intrinsics().intl_collator_constructor(), locales, options));