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LibJS: Reorganize computing of |this| for CallExpressions

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This avoids executing the LHS of the object expression twice when doing
a call on the result of an object expression.
This commit is contained in:
Andreas Kling 2020-04-01 18:51:27 +02:00
parent 021d78f8f7
commit cd9379dca9
2 changed files with 29 additions and 11 deletions
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34
Libraries/LibJS/AST.cpp
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@ -60,9 +60,30 @@ Value ExpressionStatement::execute(Interpreter& interpreter) const
return m_expression->execute(interpreter);
}
CallExpression::ThisAndCallee CallExpression::compute_this_and_callee(Interpreter& interpreter) const
{
if (is_new_expression()) {
// Computing |this| is irrelevant for "new" expression.
return { {}, m_callee->execute(interpreter) };
}
if (m_callee->is_member_expression()) {
auto& member_expression = static_cast<const MemberExpression&>(*m_callee);
auto object_value = member_expression.object().execute(interpreter);
if (interpreter.exception())
return {};
auto* this_value = object_value.to_object(interpreter.heap());
if (interpreter.exception())
return {};
auto callee = this_value->get(member_expression.computed_property_name(interpreter)).value_or({});
return { this_value, callee };
}
return { &interpreter.global_object(), m_callee->execute(interpreter) };
}
Value CallExpression::execute(Interpreter& interpreter) const
{
auto callee = m_callee->execute(interpreter);
auto [this_value, callee] = compute_this_and_callee(interpreter);
if (interpreter.exception())
return {};
@ -89,15 +110,7 @@ Value CallExpression::execute(Interpreter& interpreter) const
new_object->set_prototype(prototype.value().as_object());
call_frame.this_value = new_object;
} else {
if (m_callee->is_member_expression()) {
auto object_value = static_cast<const MemberExpression&>(*m_callee).object().execute(interpreter);
if (interpreter.exception())
return {};
auto this_value = object_value.to_object(interpreter.heap());
if (interpreter.exception())
return {};
call_frame.this_value = this_value;
}
call_frame.this_value = this_value;
}
auto result = function->call(interpreter);
@ -942,5 +955,4 @@ void SwitchCase::dump(int indent) const
statement.dump(indent + 1);
}
}
}