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LibJS: More properly implement scoping rules in bytecode codegen

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Now we emit CreateVariable and SetVariable with the appropriate
initialization/environment modes, much closer to the spec.
This makes a whole lot of things like let/const variables, function
and variable hoisting and some other things work :^)
This commit is contained in:
Ali Mohammad Pur 2022-02-12 19:48:45 +03:30 • committed by Linus Groh
parent c7e6b65fd2
commit 1bbfaf8627
12 changed files with 503 additions and 38 deletions
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55
Userland/Libraries/LibJS/Bytecode/Generator.h
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@ -24,6 +24,11 @@ namespace JS::Bytecode {
class Generator {
public:
enum class SurroundingScopeKind {
Global,
Function,
Block,
};
static CodeGenerationErrorOr<NonnullOwnPtr<Executable>> generate(ASTNode const&, FunctionKind = FunctionKind::Normal);
Register allocate_register();
@ -117,6 +122,55 @@ public:
bool is_in_generator_function() const { return m_enclosing_function_kind == FunctionKind::Generator; }
bool is_in_async_function() const { return m_enclosing_function_kind == FunctionKind::Async; }
enum class BindingMode {
Lexical,
Var,
Global,
};
struct LexicalScope {
SurroundingScopeKind kind;
BindingMode mode;
HashTable<IdentifierTableIndex> known_bindings;
};
void register_binding(IdentifierTableIndex identifier, BindingMode mode = BindingMode::Lexical)
{
m_variable_scopes.last_matching([&](auto& x) { return x.mode == BindingMode::Global || x.mode == mode; })->known_bindings.set(identifier);
}
bool has_binding(IdentifierTableIndex identifier, Optional<BindingMode> const& specific_binding_mode = {})
{
for (auto index = m_variable_scopes.size(); index > 0; --index) {
auto& scope = m_variable_scopes[index - 1];
if (scope.mode != BindingMode::Global && specific_binding_mode.value_or(scope.mode) != scope.mode)
continue;
if (scope.known_bindings.contains(identifier))
return true;
}
return false;
}
void begin_variable_scope(BindingMode mode = BindingMode::Lexical, SurroundingScopeKind kind = SurroundingScopeKind::Block)
{
m_variable_scopes.append({ kind, mode, {} });
if (mode != BindingMode::Global) {
emit<Bytecode::Op::CreateEnvironment>(
mode == BindingMode::Lexical
? Bytecode::Op::EnvironmentMode::Lexical
: Bytecode::Op::EnvironmentMode::Var);
}
}
void end_variable_scope()
{
auto mode = m_variable_scopes.take_last().mode;
if (mode != BindingMode::Global && !m_current_basic_block->is_terminated()) {
emit<Bytecode::Op::LeaveEnvironment>(
mode == BindingMode::Lexical
? Bytecode::Op::EnvironmentMode::Lexical
: Bytecode::Op::EnvironmentMode::Var);
}
}
private:
Generator();
~Generator();
@ -134,6 +188,7 @@ private:
FunctionKind m_enclosing_function_kind { FunctionKind::Normal };
Vector<Label> m_continuable_scopes;
Vector<Label> m_breakable_scopes;
Vector<LexicalScope> m_variable_scopes;
};
}