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LibJS/Bytecode: Make constant deduplication a bit smarter

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Instead of scanning through the list of seen constants, we now have a
more structured storage of the constants true, false, null, undefined,
and every possible Int32 value.

This fixes an O(n^2) issue found by Kraken/json-stringify-tinderbox.js
This commit is contained in:
Andreas Kling 2024-05-14 14:28:22 +02:00
parent 044539c60b
commit ae90e26315
Notes: sideshowbarker 2024-07-16 20:21:48 +09:00 
Author: https://github.com/awesomekling
Commit: https://github.com/SerenityOS/serenity/commit/ae90e26315
Pull-request: https://github.com/SerenityOS/serenity/pull/24524
3 changed files with 54 additions and 15 deletions
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8
Userland/Libraries/LibJS/Bytecode/ASTCodegen.cpp
View File

@ -383,7 +383,7 @@ Bytecode::CodeGenerationErrorOr<Optional<ScopedOperand>> UnaryExpression::genera
Bytecode::CodeGenerationErrorOr<Optional<ScopedOperand>> NumericLiteral::generate_bytecode(Bytecode::Generator& generator, [[maybe_unused]] Optional<ScopedOperand> preferred_dst) const
{
Bytecode::Generator::SourceLocationScope scope(generator, *this);
return generator.add_constant(Value(m_value), Bytecode::Generator::DeduplicateConstant::No);
return generator.add_constant(Value(m_value));
}
Bytecode::CodeGenerationErrorOr<Optional<ScopedOperand>> BooleanLiteral::generate_bytecode(Bytecode::Generator& generator, [[maybe_unused]] Optional<ScopedOperand> preferred_dst) const
@ -412,13 +412,13 @@ Bytecode::CodeGenerationErrorOr<Optional<ScopedOperand>> BigIntLiteral::generate
return MUST(Crypto::SignedBigInteger::from_base(2, m_value.substring(2, m_value.length() - 3)));
return MUST(Crypto::SignedBigInteger::from_base(10, m_value.substring(0, m_value.length() - 1)));
}();
return generator.add_constant(BigInt::create(generator.vm(), move(integer)), Bytecode::Generator::DeduplicateConstant::No);
return generator.add_constant(BigInt::create(generator.vm(), move(integer)));
}
Bytecode::CodeGenerationErrorOr<Optional<ScopedOperand>> StringLiteral::generate_bytecode(Bytecode::Generator& generator, [[maybe_unused]] Optional<ScopedOperand> preferred_dst) const
{
Bytecode::Generator::SourceLocationScope scope(generator, *this);
return generator.add_constant(PrimitiveString::create(generator.vm(), m_value), Bytecode::Generator::DeduplicateConstant::No);
return generator.add_constant(PrimitiveString::create(generator.vm(), m_value));
}
Bytecode::CodeGenerationErrorOr<Optional<ScopedOperand>> RegExpLiteral::generate_bytecode(Bytecode::Generator& generator, Optional<ScopedOperand> preferred_dst) const
@ -1283,7 +1283,7 @@ static Bytecode::CodeGenerationErrorOr<void> generate_object_binding_pattern_byt
if (name.has<NonnullRefPtr<Identifier const>>()) {
auto const& identifier = name.get<NonnullRefPtr<Identifier const>>()->string();
if (has_rest) {
excluded_property_names.append(generator.add_constant(PrimitiveString::create(generator.vm(), identifier), Bytecode::Generator::DeduplicateConstant::No));
excluded_property_names.append(generator.add_constant(PrimitiveString::create(generator.vm(), identifier)));
}
generator.emit_get_by_id(value, object, generator.intern_identifier(identifier));
} else {

42
Userland/Libraries/LibJS/Bytecode/Generator.cpp
View File

@ -1191,4 +1191,46 @@ ScopedOperand Generator::copy_if_needed_to_preserve_evaluation_order(ScopedOpera
return new_register;
}
ScopedOperand Generator::add_constant(Value value)
{
auto append_new_constant = [&] {
m_constants.append(value);
return ScopedOperand { *this, Operand(Operand::Type::Constant, m_constants.size() - 1) };
};
if (value.is_boolean()) {
if (value.as_bool()) {
if (!m_true_constant.has_value())
m_true_constant = append_new_constant();
return m_true_constant.value();
} else {
if (!m_false_constant.has_value())
m_false_constant = append_new_constant();
return m_false_constant.value();
}
}
if (value.is_undefined()) {
if (!m_undefined_constant.has_value())
m_undefined_constant = append_new_constant();
return m_undefined_constant.value();
}
if (value.is_null()) {
if (!m_null_constant.has_value())
m_null_constant = append_new_constant();
return m_null_constant.value();
}
if (value.is_empty()) {
if (!m_empty_constant.has_value())
m_empty_constant = append_new_constant();
return m_empty_constant.value();
}
if (value.is_int32()) {
auto as_int32 = value.as_i32();
return m_int32_constants.ensure(as_int32, [&] {
return append_new_constant();
});
}
return append_new_constant();
}
}

19
Userland/Libraries/LibJS/Bytecode/Generator.h
View File

@ -326,17 +326,7 @@ public:
Yes,
No,
};
[[nodiscard]] ScopedOperand add_constant(Value value, DeduplicateConstant deduplicate_constant = DeduplicateConstant::Yes)
{
if (deduplicate_constant == DeduplicateConstant::Yes) {
for (size_t i = 0; i < m_constants.size(); ++i) {
if (m_constants[i] == value)
return ScopedOperand(*this, Operand(Operand::Type::Constant, i));
}
}
m_constants.append(value);
return ScopedOperand(*this, Operand(Operand::Type::Constant, m_constants.size() - 1));
}
[[nodiscard]] ScopedOperand add_constant(Value);
[[nodiscard]] Value get_constant(ScopedOperand const& operand) const
{
@ -385,6 +375,13 @@ private:
NonnullOwnPtr<RegexTable> m_regex_table;
MarkedVector<Value> m_constants;
mutable Optional<ScopedOperand> m_true_constant;
mutable Optional<ScopedOperand> m_false_constant;
mutable Optional<ScopedOperand> m_null_constant;
mutable Optional<ScopedOperand> m_undefined_constant;
mutable Optional<ScopedOperand> m_empty_constant;
mutable HashMap<i32, ScopedOperand> m_int32_constants;
ScopedOperand m_accumulator;
ScopedOperand m_this_value;
Vector<Register> m_free_registers;