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LibJS/Bytecode: Keep saved return value in call frame register

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This fixes an issue where returning inside a `try` block and then
calling a function inside `finally` would clobber the saved return
value from the `try` block.

Note that we didn't need to change the base of register allocation,
since it was already 1 too high.

With this fixed, https://microsoft.com/edge loads in bytecode mode. :^)

Thanks to Luke for reducing the issue!
This commit is contained in:
Andreas Kling 2023-07-21 17:30:07 +02:00
parent 475f1b6083
commit 9f06e130a2
4 changed files with 26 additions and 10 deletions
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16
Userland/Libraries/LibJS/Bytecode/Interpreter.cpp
View file

@ -46,8 +46,6 @@ void Interpreter::visit_edges(Cell::Visitor& visitor)
{
if (m_return_value.has_value())
visitor.visit(*m_return_value);
if (m_saved_return_value.has_value())
visitor.visit(*m_saved_return_value);
if (m_saved_exception.has_value())
visitor.visit(*m_saved_exception);
for (auto& frame : m_call_frames) {
@ -277,8 +275,7 @@ Interpreter::ValueAndFrame Interpreter::run_and_return_frame(Realm& realm, Execu
if (!unwind_contexts().is_empty() && !will_yield) {
auto& unwind_context = unwind_contexts().last();
if (unwind_context.executable == m_current_executable && unwind_context.finalizer) {
m_saved_return_value = m_return_value;
m_return_value = {};
reg(Register::saved_return_value()) = m_return_value.release_value();
m_current_block = unwind_context.finalizer;
// the unwind_context will be pop'ed when entering the finally block
continue;
@ -308,13 +305,15 @@ Interpreter::ValueAndFrame Interpreter::run_and_return_frame(Realm& realm, Execu
}
}
auto saved_return_value = reg(Register::saved_return_value());
auto frame = pop_call_frame();
Value return_value = js_undefined();
if (m_return_value.has_value()) {
return_value = m_return_value.release_value();
} else if (m_saved_return_value.has_value() && !m_saved_exception.has_value()) {
return_value = m_saved_return_value.release_value();
} else if (!saved_return_value.is_empty()) {
return_value = saved_return_value;
}
// NOTE: The return value from a called function is put into $0 in the caller context.
@ -335,7 +334,6 @@ Interpreter::ValueAndFrame Interpreter::run_and_return_frame(Realm& realm, Execu
if (m_saved_exception.has_value()) {
Value thrown_value = m_saved_exception.value();
m_saved_exception = {};
m_saved_return_value = {};
if (auto* call_frame = frame.get_pointer<NonnullOwnPtr<CallFrame>>())
return { throw_completion(thrown_value), move(*call_frame) };
return { throw_completion(thrown_value), nullptr };
@ -366,8 +364,8 @@ ThrowCompletionOr<void> Interpreter::continue_pending_unwind(Label const& resume
return throw_completion(m_saved_exception.release_value());
}
if (m_saved_return_value.has_value()) {
do_return(m_saved_return_value.release_value());
if (!saved_return_value().is_empty()) {
do_return(saved_return_value());
return {};
}

2
Userland/Libraries/LibJS/Bytecode/Interpreter.h
View file

@ -61,6 +61,7 @@ public:
ValueAndFrame run_and_return_frame(Realm&, Bytecode::Executable&, Bytecode::BasicBlock const* entry_point, CallFrame* = nullptr);
ALWAYS_INLINE Value& accumulator() { return reg(Register::accumulator()); }
ALWAYS_INLINE Value& saved_return_value() { return reg(Register::saved_return_value()); }
Value& reg(Register const& r) { return registers()[r.index()]; }
auto& saved_lexical_environment_stack() { return call_frame().saved_lexical_environments; }
@ -119,7 +120,6 @@ private:
Optional<BasicBlock const*> m_pending_jump;
BasicBlock const* m_scheduled_jump { nullptr };
Optional<Value> m_return_value;
Optional<Value> m_saved_return_value;
Optional<Value> m_saved_exception;
Executable* m_current_executable { nullptr };
OwnPtr<JS::Interpreter> m_ast_interpreter;

7
Userland/Libraries/LibJS/Bytecode/Register.h
View file

@ -19,6 +19,13 @@ public:
return Register(accumulator_index);
}
constexpr static u32 saved_return_value_index = 1;
static constexpr Register saved_return_value()
{
return Register(saved_return_value_index);
}
constexpr explicit Register(u32 index)
: m_index(index)
{