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LibJS: Add a fast path for checking if attached TAs are out of bounds

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

On https://cyxx.github.io/another_js, this reduces the runtime of
IsValidIntegerIndex from 11.5% to 10.7%.
This commit is contained in:
Timothy Flynn 2024-02-27 10:35:41 -05:00 committed by Andreas Kling
parent 84936c9ab6
commit 5fd53652b7
Notes: sideshowbarker 2024-07-17 04:49:48 +09:00 
Author: https://github.com/trflynn89
Commit: https://github.com/SerenityOS/serenity/commit/5fd53652b7
Pull-request: https://github.com/SerenityOS/serenity/pull/23374
2 changed files with 14 additions and 6 deletions
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8
Userland/Libraries/LibJS/Runtime/TypedArray.cpp
View File

@ -668,7 +668,7 @@ u32 typed_array_length_with_known_valid_bounds(TypedArrayWithBufferWitness const
}
// 10.4.5.13 IsTypedArrayOutOfBounds ( taRecord ), https://tc39.es/ecma262/#sec-istypedarrayoutofbounds
bool is_typed_array_out_of_bounds(TypedArrayWithBufferWitness const& typed_array_record)
bool is_typed_array_out_of_bounds_for_known_attached_array(TypedArrayWithBufferWitness const& typed_array_record)
{
// 1. Let O be taRecord.[[Object]].
auto object = typed_array_record.object;
@ -677,11 +677,7 @@ bool is_typed_array_out_of_bounds(TypedArrayWithBufferWitness const& typed_array
auto const& buffer_byte_length = typed_array_record.cached_buffer_byte_length;
// 3. Assert: IsDetachedBuffer(O.[[ViewedArrayBuffer]]) is true if and only if bufferByteLength is detached.
VERIFY(object->viewed_array_buffer()->is_detached() == buffer_byte_length.is_detached());
// 4. If bufferByteLength is detached, return true.
if (buffer_byte_length.is_detached())
return true;
// 5. Let byteOffsetStart be O.[[ByteOffset]].
auto byte_offset_start = object->byte_offset();
@ -728,7 +724,7 @@ bool is_valid_integer_index(TypedArrayBase const& typed_array, CanonicalIndex pr
// NOTE: Bounds checking is not a synchronizing operation when O's backing buffer is a growable SharedArrayBuffer.
// 6. If IsTypedArrayOutOfBounds(taRecord) is true, return false.
if (is_typed_array_out_of_bounds(typed_array_record))
if (is_typed_array_out_of_bounds_for_known_attached_array(typed_array_record))
return false;
// 7. Let length be TypedArrayLength(taRecord).

12
Userland/Libraries/LibJS/Runtime/TypedArray.h
View File

@ -110,6 +110,18 @@ inline u32 typed_array_length(TypedArrayWithBufferWitness const& typed_array_rec
return typed_array_length_with_known_valid_bounds(typed_array_record);
}
// Fast-path version of IsTypedArrayOutOfBounds when you already know the TA is not detached.
bool is_typed_array_out_of_bounds_for_known_attached_array(TypedArrayWithBufferWitness const&);
// 10.4.5.13 IsTypedArrayOutOfBounds ( taRecord ), https://tc39.es/ecma262/#sec-istypedarrayoutofbounds
inline bool is_typed_array_out_of_bounds(TypedArrayWithBufferWitness const& typed_array_record)
{
if (typed_array_record.cached_buffer_byte_length.is_detached())
return true;
return is_typed_array_out_of_bounds_for_known_attached_array(typed_array_record);
}
// 10.4.5.15 TypedArrayGetElement ( O, index ), https://tc39.es/ecma262/#sec-typedarraygetelement
template<typename T>
inline ThrowCompletionOr<Value> typed_array_get_element(TypedArrayBase const& typed_array, CanonicalIndex property_index)