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LibJS/Bytecode: Move bytecode operand rewriting to a separate pass

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This way we don't have to do it whenever performing some kind of
instruction rewrite.
This commit is contained in:
Andreas Kling 2024-06-01 10:19:28 +02:00
parent 97983275bc
commit 7971cfdd89
2 changed files with 37 additions and 33 deletions
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64
Userland/Libraries/LibJS/Bytecode/Generator.cpp
View file

@ -275,12 +275,14 @@ CodeGenerationErrorOr<NonnullGCPtr<Executable>> Generator::compile(VM& vm, ASTNo
HashMap<size_t, SourceRecord> source_map;
Optional<ScopedOperand> undefined_constant;
for (auto& block : generator.m_root_basic_blocks) {
if (!block->is_terminated()) {
// NOTE: We must ensure that the "undefined" constant, which will be used by the not yet
// emitted End instruction, is taken into account while shifting local operands by the
// number of constants.
(void)generator.add_constant(js_undefined());
undefined_constant = generator.add_constant(js_undefined());
break;
}
}
@ -288,6 +290,35 @@ CodeGenerationErrorOr<NonnullGCPtr<Executable>> Generator::compile(VM& vm, ASTNo
auto number_of_registers = generator.m_next_register;
auto number_of_constants = generator.m_constants.size();
// Pass: Rewrite the bytecode to use the correct register and constant indices.
for (auto& block : generator.m_root_basic_blocks) {
Bytecode::InstructionStreamIterator it(block->instruction_stream());
while (!it.at_end()) {
auto& instruction = const_cast<Instruction&>(*it);
instruction.visit_operands([number_of_registers, number_of_constants](Operand& operand) {
switch (operand.type()) {
case Operand::Type::Register:
break;
case Operand::Type::Local:
operand.offset_index_by(number_of_registers + number_of_constants);
break;
case Operand::Type::Constant:
operand.offset_index_by(number_of_registers);
break;
default:
VERIFY_NOT_REACHED();
}
});
++it;
}
}
// Also rewrite the `undefined` constant if we have one for inserting End.
if (undefined_constant.has_value())
undefined_constant.value().operand().offset_index_by(number_of_registers);
for (auto& block : generator.m_root_basic_blocks) {
basic_block_start_offsets.append(bytecode.size());
if (block->handler() || block->finalizer()) {
@ -309,21 +340,6 @@ CodeGenerationErrorOr<NonnullGCPtr<Executable>> Generator::compile(VM& vm, ASTNo
while (!it.at_end()) {
auto& instruction = const_cast<Instruction&>(*it);
instruction.visit_operands([number_of_registers, number_of_constants](Operand& operand) {
switch (operand.type()) {
case Operand::Type::Register:
break;
case Operand::Type::Local:
operand.offset_index_by(number_of_registers + number_of_constants);
break;
case Operand::Type::Constant:
operand.offset_index_by(number_of_registers);
break;
default:
VERIFY_NOT_REACHED();
}
});
// OPTIMIZATION: Don't emit jumps that just jump to the next block.
if (instruction.type() == Instruction::Type::Jump) {
auto& jump = static_cast<Bytecode::Op::Jump&>(instruction);
@ -369,21 +385,7 @@ CodeGenerationErrorOr<NonnullGCPtr<Executable>> Generator::compile(VM& vm, ASTNo
++it;
}
if (!block->is_terminated()) {
Op::End end(generator.add_constant(js_undefined()));
end.visit_operands([number_of_registers, number_of_constants](Operand& operand) {
switch (operand.type()) {
case Operand::Type::Register:
break;
case Operand::Type::Local:
operand.offset_index_by(number_of_registers + number_of_constants);
break;
case Operand::Type::Constant:
operand.offset_index_by(number_of_registers);
break;
default:
VERIFY_NOT_REACHED();
}
});
Op::End end(*undefined_constant);
bytecode.append(reinterpret_cast<u8 const*>(&end), end.length());
}
if (block->handler() || block->finalizer()) {

6
Userland/Libraries/LibJS/Bytecode/ScopedOperand.h
View file

@ -21,7 +21,8 @@ public:
~ScopedOperandImpl();
[[nodiscard]] Operand operand() const { return m_operand; }
[[nodiscard]] Operand const& operand() const { return m_operand; }
[[nodiscard]] Operand& operand() { return m_operand; }
private:
Generator& m_generator;
@ -35,7 +36,8 @@ public:
{
}
[[nodiscard]] Operand operand() const { return m_impl->operand(); }
[[nodiscard]] Operand const& operand() const { return m_impl->operand(); }
[[nodiscard]] Operand& operand() { return m_impl->operand(); }
operator Operand() const { return operand(); }
[[nodiscard]] bool operator==(ScopedOperand const& other) const { return operand() == other.operand(); }