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LibJS: Emit GetById instead of GetByValue when key is string literal

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Basically convert o["foo"] into o.foo when emitting bytecode. These are
effectively the same thing, and the latter format opts into using an
inline cache for the property lookups.
This commit is contained in:
Andreas Kling 2025-04-03 14:18:24 +02:00 • committed by Andreas Kling
commit 4426c50a18
Notes: github-actions[bot] 2025-04-03 16:48:37 +00:00
3 changed files with 33 additions and 6 deletions
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28
Libraries/LibJS/Bytecode/Generator.cpp
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@ -687,7 +687,7 @@ CodeGenerationErrorOr<Generator::ReferenceOperands> Generator::emit_load_from_re
if (super_reference.referenced_name.has_value()) {
// 5. Let propertyKey be ? ToPropertyKey(propertyNameValue).
// FIXME: This does ToPropertyKey out of order, which is observable by Symbol.toPrimitive!
emit<Bytecode::Op::GetByValueWithThis>(dst, *super_reference.base, *super_reference.referenced_name, *super_reference.this_value);
emit_get_by_value_with_this(dst, *super_reference.base, *super_reference.referenced_name, *super_reference.this_value);
} else {
// 3. Let propertyKey be StringValue of IdentifierName.
auto identifier_table_ref = intern_identifier(as<Identifier>(expression.property()).string());
@ -706,7 +706,7 @@ CodeGenerationErrorOr<Generator::ReferenceOperands> Generator::emit_load_from_re
auto saved_property = allocate_register();
emit<Bytecode::Op::Mov>(saved_property, property);
auto dst = preferred_dst.has_value() ? preferred_dst.value() : allocate_register();
emit<Bytecode::Op::GetByValue>(dst, base, property, move(base_identifier));
emit_get_by_value(dst, base, property, move(base_identifier));
return ReferenceOperands {
.base = base,
.referenced_name = saved_property,
@ -1122,6 +1122,30 @@ void Generator::emit_get_by_id_with_this(ScopedOperand dst, ScopedOperand base,
emit<Op::GetByIdWithThis>(dst, base, id, this_value, m_next_property_lookup_cache++);
}
void Generator::emit_get_by_value(ScopedOperand dst, ScopedOperand base, ScopedOperand property, Optional<IdentifierTableIndex> base_identifier)
{
if (property.operand().is_constant() && get_constant(property).is_string()) {
auto property_key = MUST(get_constant(property).to_property_key(vm()));
if (property_key.is_string()) {
emit_get_by_id(dst, base, intern_identifier(property_key.as_string()), base_identifier);
return;
}
}
emit<Op::GetByValue>(dst, base, property, base_identifier);
}
void Generator::emit_get_by_value_with_this(ScopedOperand dst, ScopedOperand base, ScopedOperand property, ScopedOperand this_value)
{
if (property.operand().is_constant() && get_constant(property).is_string()) {
auto property_key = MUST(get_constant(property).to_property_key(vm()));
if (property_key.is_string()) {
emit_get_by_id_with_this(dst, base, intern_identifier(property_key.as_string()), this_value);
return;
}
}
emit<Op::GetByValueWithThis>(dst, base, property, this_value);
}
void Generator::emit_iterator_value(ScopedOperand dst, ScopedOperand result)
{
emit_get_by_id(dst, result, intern_identifier("value"_fly_string));