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LibJS: Compile ScriptFunctions into bytecode and run them that way :^)

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If there's a current Bytecode::Interpreter in action, ScriptFunction
will now compile itself into bytecode and execute in that context.

This patch also adds the Return bytecode instruction so that we can
actually return values from called functions. :^)

Return values are propagated from callee to caller via the caller's
$0 register. Bytecode::Interpreter now keeps a stack of register
"windows". These are not very efficient, but it should be pretty
straightforward to convert them to e.g a sliding register window
architecture later on.

This is pretty dang cool! :^)
This commit is contained in:
Andreas Kling 2021-06-05 15:53:36 +02:00
parent b609fc6d51
commit 80b1604b0a
7 changed files with 150 additions and 49 deletions
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59
Userland/Libraries/LibJS/Bytecode/Interpreter.cpp
View file

@ -11,32 +11,46 @@
namespace JS::Bytecode {
static Interpreter* s_current;
Interpreter* Interpreter::current()
{
return s_current;
}
Interpreter::Interpreter(GlobalObject& global_object)
: m_vm(global_object.vm())
, m_global_object(global_object)
{
VERIFY(!s_current);
s_current = this;
}
Interpreter::~Interpreter()
{
VERIFY(s_current == this);
s_current = nullptr;
}
void Interpreter::run(Bytecode::Block const& block)
Value Interpreter::run(Bytecode::Block const& block)
{
dbgln("Bytecode::Interpreter will run block {:p}", &block);
CallFrame global_call_frame;
global_call_frame.this_value = &global_object();
static FlyString global_execution_context_name = "(*BC* global execution context)";
global_call_frame.function_name = global_execution_context_name;
global_call_frame.scope = &global_object();
VERIFY(!vm().exception());
// FIXME: How do we know if we're in strict mode? Maybe the Bytecode::Block should know this?
// global_call_frame.is_strict_mode = ???;
vm().push_call_frame(global_call_frame, global_object());
VERIFY(!vm().exception());
if (vm().call_stack().is_empty()) {
CallFrame global_call_frame;
global_call_frame.this_value = &global_object();
static FlyString global_execution_context_name = "(*BC* global execution context)";
global_call_frame.function_name = global_execution_context_name;
global_call_frame.scope = &global_object();
VERIFY(!vm().exception());
// FIXME: How do we know if we're in strict mode? Maybe the Bytecode::Block should know this?
// global_call_frame.is_strict_mode = ???;
vm().push_call_frame(global_call_frame, global_object());
VERIFY(!vm().exception());
}
m_registers.resize(block.register_count());
m_register_windows.append(make<RegisterWindow>());
registers().resize(block.register_count());
size_t pc = 0;
while (pc < block.instructions().size()) {
@ -46,18 +60,33 @@ void Interpreter::run(Bytecode::Block const& block)
pc = m_pending_jump.release_value();
continue;
}
if (!m_return_value.is_empty())
break;
++pc;
}
dbgln("Bytecode::Interpreter did run block {:p}", &block);
for (size_t i = 0; i < m_registers.size(); ++i) {
for (size_t i = 0; i < registers().size(); ++i) {
String value_string;
if (m_registers[i].is_empty())
if (registers()[i].is_empty())
value_string = "(empty)";
else
value_string = m_registers[i].to_string_without_side_effects();
value_string = registers()[i].to_string_without_side_effects();
dbgln("[{:3}] {}", i, value_string);
}
m_register_windows.take_last();
m_return_value = m_return_value.value_or(js_undefined());
// NOTE: The return value from a called function is put into $0 in the caller context.
if (!m_register_windows.is_empty())
m_register_windows.last()[0] = m_return_value;
if (vm().call_stack().size() == 1)
vm().pop_call_frame();
return m_return_value;
}
}