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LibJS: Add a fast path for creating a TA witness record for attached TAs

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In IsValidIntegerIndex, we check if the TA is detached before invoking
MakeTypedArrayWithBufferWitnessRecord. There's no need to check it
again.

On https://cyxx.github.io/another_js, this reduces the runtime of
IsValidIntegerIndex from 10.7% to 9.9%.
This commit is contained in:
Timothy Flynn 2024-02-27 10:53:09 -05:00 committed by Andreas Kling
parent 5fd53652b7
commit 72cee4c88b
2 changed files with 18 additions and 14 deletions
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19
Userland/Libraries/LibJS/Runtime/TypedArray.cpp
View file

@ -588,26 +588,19 @@ JS_ENUMERATE_TYPED_ARRAYS
#undef __JS_ENUMERATE
// 10.4.5.9 MakeTypedArrayWithBufferWitnessRecord ( obj, order ), https://tc39.es/ecma262/#sec-maketypedarraywithbufferwitnessrecord
TypedArrayWithBufferWitness make_typed_array_with_buffer_witness_record(TypedArrayBase const& typed_array, ArrayBuffer::Order order)
TypedArrayWithBufferWitness make_typed_array_with_buffer_witness_record_for_known_attached_array(TypedArrayBase const& typed_array, ArrayBuffer::Order order)
{
// 1. Let buffer be obj.[[ViewedArrayBuffer]].
auto* buffer = typed_array.viewed_array_buffer();
ByteLength byte_length { 0 };
// 2. If IsDetachedBuffer(buffer) is true, then
if (buffer->is_detached()) {
// a. Let byteLength be detached.
byte_length = ByteLength::detached();
}
// a. Let byteLength be detached.
// 3. Else,
else {
// a. Let byteLength be ArrayBufferByteLength(buffer, order).
byte_length = array_buffer_byte_length(*buffer, order);
}
// a. Let byteLength be ArrayBufferByteLength(buffer, order).
auto byte_length = array_buffer_byte_length(*buffer, order);
// 4. Return the TypedArray With Buffer Witness Record { [[Object]]: obj, [[CachedBufferByteLength]]: byteLength }.
return { .object = typed_array, .cached_buffer_byte_length = move(byte_length) };
return { .object = typed_array, .cached_buffer_byte_length = byte_length };
}
// 10.4.5.11 TypedArrayByteLength ( taRecord ), https://tc39.es/ecma262/#sec-typedarraybytelength
@ -719,7 +712,7 @@ bool is_valid_integer_index(TypedArrayBase const& typed_array, CanonicalIndex pr
return false;
// 4. Let taRecord be MakeTypedArrayWithBufferWitnessRecord(O, unordered).
auto typed_array_record = make_typed_array_with_buffer_witness_record(typed_array, ArrayBuffer::Unordered);
auto typed_array_record = make_typed_array_with_buffer_witness_record_for_known_attached_array(typed_array, ArrayBuffer::Unordered);
// NOTE: Bounds checking is not a synchronizing operation when O's backing buffer is a growable SharedArrayBuffer.

13
Userland/Libraries/LibJS/Runtime/TypedArray.h
View file

@ -92,11 +92,22 @@ struct TypedArrayWithBufferWitness {
ByteLength cached_buffer_byte_length; // [[CachedBufferByteLength]]
};
TypedArrayWithBufferWitness make_typed_array_with_buffer_witness_record(TypedArrayBase const&, ArrayBuffer::Order);
u32 typed_array_byte_length(TypedArrayWithBufferWitness const&);
bool is_typed_array_out_of_bounds(TypedArrayWithBufferWitness const&);
bool is_valid_integer_index(TypedArrayBase const&, CanonicalIndex);
// Fast-path version of MakeTypedArrayWithBufferWitnessRecord when you already know the TA is not detached.
TypedArrayWithBufferWitness make_typed_array_with_buffer_witness_record_for_known_attached_array(TypedArrayBase const&, ArrayBuffer::Order);
// 10.4.5.9 MakeTypedArrayWithBufferWitnessRecord ( obj, order ), https://tc39.es/ecma262/#sec-maketypedarraywithbufferwitnessrecord
inline TypedArrayWithBufferWitness make_typed_array_with_buffer_witness_record(TypedArrayBase const& typed_array, ArrayBuffer::Order order)
{
if (typed_array.viewed_array_buffer()->is_detached())
return { .object = typed_array, .cached_buffer_byte_length = ByteLength::detached() };
return make_typed_array_with_buffer_witness_record_for_known_attached_array(typed_array, order);
}
// Fast-path version of TypedArrayLength when you already know the TA is within its bounds,
// i.e. you previously checked IsTypedArrayOutOfBounds.
u32 typed_array_length_with_known_valid_bounds(TypedArrayWithBufferWitness const&);