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https://github.com/RGBCube/serenity
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LibJS: Avoid unnecessary ToObject conversion when resolving references
When performing GetValue on a primitive type we do not need to perform the ToObject conversion as it will resolve to a property on the prototype object. To avoid this we skip the initial ToObject conversion on the base value as it only serves to get the primitive's boxed prototype. We further specialize on PrimitiveString in order to get efficient behaviour behaviour for the direct properties. Depending on the tests anywhere from 20 to 60%, with significant loop overhead.
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7 changed files with 77 additions and 24 deletions
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@ -4,9 +4,13 @@
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include "LibJS/Runtime/Value.h"
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#include <AK/CharacterTypes.h>
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#include <AK/Utf16View.h>
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#include <LibJS/Runtime/AbstractOperations.h>
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#include <LibJS/Runtime/GlobalObject.h>
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#include <LibJS/Runtime/PrimitiveString.h>
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#include <LibJS/Runtime/PropertyKey.h>
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#include <LibJS/Runtime/VM.h>
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namespace JS {
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@ -51,6 +55,26 @@ Utf16View PrimitiveString::utf16_string_view() const
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return utf16_string().view();
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}
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Optional<Value> PrimitiveString::get(GlobalObject& global_object, PropertyKey const& property_key) const
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{
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if (property_key.is_symbol())
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return {};
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if (property_key.is_string()) {
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if (property_key.as_string() == global_object.vm().names.length.as_string()) {
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auto length = utf16_string().length_in_code_units();
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return Value(static_cast<double>(length));
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}
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}
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auto index = canonical_numeric_index_string(property_key);
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if (!index.has_value())
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return {};
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auto str = utf16_string_view();
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auto length = str.length_in_code_units();
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if (length <= *index)
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return {};
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return js_string(vm(), str.substring_view(*index, 1));
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}
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PrimitiveString* js_string(Heap& heap, Utf16View const& view)
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{
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return js_string(heap, Utf16String(view));
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