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LibJS: Add basic "if" statement support to the bytecode VM :^)

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This also required making Bytecode::Op::Jump support lazy linking
to a target label.

I left a FIXME here about having the "if" statement return the result
value from the taken branch statement. That's what the AST interpreter
does but I'm not sure if it's actually required.
This commit is contained in:
Andreas Kling 2021-06-06 13:26:50 +02:00
parent 80b1604b0a
commit 79eac08f5b
4 changed files with 30 additions and 5 deletions
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22
Userland/Libraries/LibJS/Bytecode/ASTCodegen.cpp
View file

@ -187,4 +187,26 @@ Optional<Bytecode::Register> ReturnStatement::generate_bytecode(Bytecode::Genera
return argument_reg;
}
Optional<Bytecode::Register> IfStatement::generate_bytecode(Bytecode::Generator& generator) const
{
auto predicate_reg = m_predicate->generate_bytecode(generator);
auto& if_jump = generator.emit<Bytecode::Op::JumpIfTrue>(*predicate_reg);
auto& else_jump = generator.emit<Bytecode::Op::JumpIfFalse>(*predicate_reg);
if_jump.set_target(generator.make_label());
(void)m_consequent->generate_bytecode(generator);
auto& end_jump = generator.emit<Bytecode::Op::Jump>();
else_jump.set_target(generator.make_label());
if (m_alternate) {
(void)m_alternate->generate_bytecode(generator);
}
end_jump.set_target(generator.make_label());
// FIXME: Do we need IfStatement to return the consequent/alternate result value?
// (That's what the AST interpreter currently does)
return {};
}
}