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LibJS: Optimize IsValidIntegerIndex for TAs with non-resizable buffers

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If we know the TA does not have a resizable ArrayBuffer, we can avoid
most of the heavy lifting that IsValidIntegerIndex performs.

On https://cyxx.github.io/another_js, this reduces the runtime of
IsValidIntegerIndex from 7.1% to 3.7%.
This commit is contained in:
Timothy Flynn 2024-02-28 09:34:07 -05:00 committed by Andreas Kling
parent b821f7b283
commit 08ad2d774e
2 changed files with 31 additions and 12 deletions
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13
Userland/Libraries/LibJS/Runtime/TypedArray.cpp
View file

@ -700,21 +700,12 @@ bool is_typed_array_out_of_bounds_for_known_attached_array(TypedArrayWithBufferW
}
// 10.4.5.14 IsValidIntegerIndex ( O, index ), https://tc39.es/ecma262/#sec-isvalidintegerindex
bool is_valid_integer_index(TypedArrayBase const& typed_array, CanonicalIndex property_index)
bool is_valid_integer_index_slow_case(TypedArrayBase const& typed_array, CanonicalIndex property_index)
{
// 1. If IsDetachedBuffer(O.[[ViewedArrayBuffer]]) is true, return false.
if (typed_array.viewed_array_buffer()->is_detached())
return false;
// 2. If IsIntegralNumber(index) is false, return false.
// 3. If index is -0𝔽, return false.
if (!property_index.is_index())
return false;
// 4. Let taRecord be MakeTypedArrayWithBufferWitnessRecord(O, 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.
// 5. 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_for_known_attached_array(typed_array_record))

30
Userland/Libraries/LibJS/Runtime/TypedArray.h
View file

@ -96,7 +96,6 @@ struct TypedArrayWithBufferWitness {
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);
@ -135,6 +134,35 @@ inline bool is_typed_array_out_of_bounds(TypedArrayWithBufferWitness const& type
return is_typed_array_out_of_bounds_for_known_attached_array(typed_array_record);
}
bool is_valid_integer_index_slow_case(TypedArrayBase const&, CanonicalIndex property_index);
// 10.4.5.14 IsValidIntegerIndex ( O, index ), https://tc39.es/ecma262/#sec-isvalidintegerindex
inline bool is_valid_integer_index(TypedArrayBase const& typed_array, CanonicalIndex property_index)
{
// 1. If IsDetachedBuffer(O.[[ViewedArrayBuffer]]) is true, return false.
if (typed_array.viewed_array_buffer()->is_detached())
return false;
// 2. If IsIntegralNumber(index) is false, return false.
// 3. If index is -0𝔽, return false.
if (!property_index.is_index())
return false;
// OPTIMIZATION: For TypedArrays with non-resizable ArrayBuffers, we can avoid most of the work performed by
// IsValidIntegerIndex. We just need to check whether the array itself is out-of-bounds and if
// the provided index is within the array bounds.
if (auto const& array_length = typed_array.array_length(); !array_length.is_auto()) {
auto byte_length = array_buffer_byte_length(*typed_array.viewed_array_buffer(), ArrayBuffer::Unordered);
auto byte_offset_end = typed_array.byte_offset() + array_length.length() * typed_array.element_size();
return typed_array.byte_offset() <= byte_length
&& byte_offset_end <= byte_length
&& property_index.as_index() < array_length.length();
}
return is_valid_integer_index_slow_case(typed_array, property_index);
}
// 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)