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LibJS: Add fast paths in TypedArrayPrototype.fill()

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Filling a typed array with an integer shouldn't have to go through the
generic Set for every element.

This knocks a 7% item down to <1% in profiles of Another World JS at
https://cyxx.github.io/another_js/
This commit is contained in:
Andreas Kling 2024-05-13 12:36:00 +02:00
parent d79353a477
commit 6f5201b759
Notes: sideshowbarker 2024-07-17 03:10:07 +09:00 
Author: https://github.com/awesomekling
Commit: https://github.com/SerenityOS/serenity/commit/6f5201b759
Pull-request: https://github.com/SerenityOS/serenity/pull/24314
1 changed files with 66 additions and 3 deletions
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69
Userland/Libraries/LibJS/Runtime/TypedArrayPrototype.cpp
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@ -469,6 +469,34 @@ JS_DEFINE_NATIVE_FUNCTION(TypedArrayPrototype::every)
return true;
}
// NOTE: This function assumes that the index is valid within the TypedArray,
// and that the TypedArray is not detached.
template<typename T>
inline void fast_typed_array_fill(TypedArrayBase& typed_array, u32 begin, u32 end, T value)
{
Checked<size_t> computed_begin = begin;
computed_begin *= sizeof(T);
computed_begin += typed_array.byte_offset();
Checked<size_t> computed_end = end;
computed_end *= sizeof(T);
computed_end += typed_array.byte_offset();
if (computed_begin.has_overflow() || computed_end.has_overflow()) [[unlikely]] {
return;
}
if (computed_begin.value() >= typed_array.viewed_array_buffer()->byte_length()
|| computed_end.value() > typed_array.viewed_array_buffer()->byte_length()) [[unlikely]] {
return;
}
auto& array_buffer = *typed_array.viewed_array_buffer();
auto* slot = reinterpret_cast<T*>(array_buffer.buffer().offset_pointer(computed_begin.value()));
for (auto i = begin; i < end; ++i)
*(slot++) = value;
}
// 23.2.3.9 %TypedArray%.prototype.fill ( value [ , start [ , end ] ] ), https://tc39.es/ecma262/#sec-%typedarray%.prototype.fill
JS_DEFINE_NATIVE_FUNCTION(TypedArrayPrototype::fill)
{
@ -537,13 +565,48 @@ JS_DEFINE_NATIVE_FUNCTION(TypedArrayPrototype::fill)
// 17. Set final to min(final, len).
final = min(final, length);
if (value.is_int32()) {
switch (typed_array->kind()) {
case TypedArrayBase::Kind::Uint8Array:
fast_typed_array_fill<u8>(*typed_array, k, final, static_cast<u8>(value.as_i32()));
return typed_array;
case TypedArrayBase::Kind::Uint16Array:
fast_typed_array_fill<u16>(*typed_array, k, final, static_cast<u16>(value.as_i32()));
return typed_array;
case TypedArrayBase::Kind::Uint32Array:
fast_typed_array_fill<u32>(*typed_array, k, final, static_cast<u32>(value.as_i32()));
return typed_array;
case TypedArrayBase::Kind::Int8Array:
fast_typed_array_fill<i8>(*typed_array, k, final, static_cast<i8>(value.as_i32()));
return typed_array;
case TypedArrayBase::Kind::Int16Array:
fast_typed_array_fill<i16>(*typed_array, k, final, static_cast<i16>(value.as_i32()));
return typed_array;
case TypedArrayBase::Kind::Int32Array:
fast_typed_array_fill<i32>(*typed_array, k, final, value.as_i32());
return typed_array;
case TypedArrayBase::Kind::Uint8ClampedArray:
fast_typed_array_fill<u8>(*typed_array, k, final, clamp(value.as_i32(), 0, 255));
return typed_array;
default:
// FIXME: Support more TypedArray kinds.
break;
}
}
// 18. Repeat, while k < final,
while (k < final) {
// a. Let Pk be ! ToString(𝔽(k)).
PropertyKey property_key { k };
// b. Perform ! Set(O, Pk, value, true).
MUST(typed_array->set(property_key, value, Object::ShouldThrowExceptions::Yes));
CanonicalIndex canonical_index { CanonicalIndex::Type::Index, k };
switch (typed_array->kind()) {
#define __JS_ENUMERATE(ClassName, snake_name, PrototypeName, ConstructorName, Type) \
case TypedArrayBase::Kind::ClassName: \
(void)typed_array_set_element<Type>(*typed_array, canonical_index, value); \
break;
JS_ENUMERATE_TYPED_ARRAYS
#undef __JS_ENUMERATE
}
// c. Set k to k + 1.
++k;