LibJS: Implement SuperCall for the Bytecode-VM

Author: Hendiadyoin1

Userland/Libraries/LibJS/AST.h

@@ -1516,6 +1516,7 @@ class SuperCall final : public Expression {
 
     virtual Completion execute(Interpreter&) const override;
     virtual void dump(int indent) const override;
+    virtual Bytecode::CodeGenerationErrorOr<void> generate_bytecode(Bytecode::Generator&) const override;
 
 private:
     Vector<CallExpression::Argument> const m_arguments;

Userland/Libraries/LibJS/Bytecode/ASTCodegen.cpp

@@ -521,6 +521,34 @@ Bytecode::CodeGenerationErrorOr<void> Identifier::generate_bytecode(Bytecode::Ge
     return {};
 }
 
+Bytecode::CodeGenerationErrorOr<void> SuperCall::generate_bytecode(Bytecode::Generator& generator) const
+{
+    Vector<Bytecode::Register> argument_registers;
+
+    if (m_is_synthetic == IsPartOfSyntheticConstructor::Yes) {
+        // NOTE: This is the case where we have a fake constructor(...args) { super(...args); } which
+        //       shouldn't call @@iterator of %Array.prototype%.
+        VERIFY(m_arguments.size() == 1);
+        VERIFY(m_arguments[0].is_spread);
+        auto const& argument = m_arguments[0];
+        // This generates a single argument, which will be implicitly passed in accumulator
+        MUST(argument.value->generate_bytecode(generator));
+    } else {
+        argument_registers.ensure_capacity(m_arguments.size());
+
+        for (auto const& arg : m_arguments) {
+            TRY(arg.value->generate_bytecode(generator));
+            auto arg_reg = generator.allocate_register();
+            generator.emit<Bytecode::Op::Store>(arg_reg);
+            argument_registers.unchecked_append(arg_reg);
+        }
+    }
+
+    generator.emit_with_extra_register_slots<Bytecode::Op::SuperCall>(argument_registers.size(), m_is_synthetic == IsPartOfSyntheticConstructor::Yes, argument_registers);
+
+    return {};
+}
+
 static Bytecode::CodeGenerationErrorOr<void> generate_binding_pattern_bytecode(Bytecode::Generator& generator, BindingPattern const& pattern, Bytecode::Op::SetVariable::InitializationMode, Bytecode::Register const& value_reg);
 
 Bytecode::CodeGenerationErrorOr<void> AssignmentExpression::generate_bytecode(Bytecode::Generator& generator) const

Userland/Libraries/LibJS/Bytecode/Instruction.h

@@ -80,6 +80,7 @@
     O(StrictlyEquals)                \
     O(StrictlyInequals)              \
     O(Sub)                           \
+    O(SuperCall)                     \
     O(Throw)                         \
     O(Typeof)                        \
     O(TypeofVariable)                \

Userland/Libraries/LibJS/Bytecode/Op.cpp

@@ -15,6 +15,7 @@
 #include <LibJS/Runtime/DeclarativeEnvironment.h>
 #include <LibJS/Runtime/ECMAScriptFunctionObject.h>
 #include <LibJS/Runtime/Environment.h>
+#include <LibJS/Runtime/FunctionEnvironment.h>
 #include <LibJS/Runtime/GlobalEnvironment.h>
 #include <LibJS/Runtime/GlobalObject.h>
 #include <LibJS/Runtime/Iterator.h>
@@ -525,6 +526,60 @@ ThrowCompletionOr<void> Call::execute_impl(Bytecode::Interpreter& interpreter) c
     return {};
 }
 
+// 13.3.7.1 Runtime Semantics: Evaluation, https://tc39.es/ecma262/#sec-super-keyword-runtime-semantics-evaluation
+ThrowCompletionOr<void> SuperCall::execute_impl(Bytecode::Interpreter& interpreter) const
+{
+    auto& vm = interpreter.vm();
+    // 1. Let newTarget be GetNewTarget().
+    auto new_target = vm.get_new_target();
+
+    // 2. Assert: Type(newTarget) is Object.
+    VERIFY(new_target.is_object());
+
+    // 3. Let func be GetSuperConstructor().
+    auto* func = get_super_constructor(vm);
+
+    // 4. Let argList be ? ArgumentListEvaluation of Arguments.
+    MarkedVector<Value> arg_list { vm.heap() };
+    if (m_is_synthetic) {
+        auto const& value = interpreter.accumulator();
+        VERIFY(value.is_object() && is<Array>(value.as_object()));
+        auto const& array_value = static_cast<Array const&>(value.as_object());
+        auto length = MUST(length_of_array_like(vm, array_value));
+        for (size_t i = 0; i < length; ++i)
+            arg_list.append(array_value.get_without_side_effects(PropertyKey { i }));
+    } else {
+        for (size_t i = 0; i < m_argument_count; ++i)
+            arg_list.append(interpreter.reg(m_arguments[i]));
+    }
+
+    // 5. If IsConstructor(func) is false, throw a TypeError exception.
+    if (!Value(func).is_constructor())
+        return vm.throw_completion<TypeError>(ErrorType::NotAConstructor, "Super constructor");
+
+    // 6. Let result be ? Construct(func, argList, newTarget).
+    auto* result = TRY(construct(vm, static_cast<FunctionObject&>(*func), move(arg_list), &new_target.as_function()));
+
+    // 7. Let thisER be GetThisEnvironment().
+    auto& this_environment = verify_cast<FunctionEnvironment>(get_this_environment(vm));
+
+    // 8. Perform ? thisER.BindThisValue(result).
+    TRY(this_environment.bind_this_value(vm, result));
+
+    // 9. Let F be thisER.[[FunctionObject]].
+    auto& f = this_environment.function_object();
+
+    // 10. Assert: F is an ECMAScript function object.
+    // NOTE: This is implied by the strong C++ type.
+
+    // 11. Perform ? InitializeInstanceElements(result, F).
+    TRY(vm.initialize_instance_elements(*result, f));
+
+    // 12. Return result.
+    interpreter.accumulator() = result;
+    return {};
+}
+
 ThrowCompletionOr<void> NewFunction::execute_impl(Bytecode::Interpreter& interpreter) const
 {
     auto& vm = interpreter.vm();
@@ -1000,6 +1055,20 @@ String Call::to_string_impl(Bytecode::Executable const&) const
     return builder.to_string();
 }
 
+String SuperCall::to_string_impl(Bytecode::Executable const&) const
+{
+    StringBuilder builder;
+    builder.append("SuperCall"sv);
+    if (m_is_synthetic) {
+        builder.append(" arguments:[...acc]"sv);
+    } else if (m_argument_count != 0) {
+        builder.append(" arguments:["sv);
+        builder.join(", "sv, Span<Register const>(m_arguments, m_argument_count));
+        builder.append(']');
+    }
+    return builder.to_string();
+}
+
 String NewFunction::to_string_impl(Bytecode::Executable const&) const
 {
     return "NewFunction";

Userland/Libraries/LibJS/Bytecode/Op.h

@@ -613,6 +613,33 @@ class Call final : public Instruction {
     Register m_arguments[];
 };
 
+// NOTE: This instruction is variable-width depending on the number of arguments!
+class SuperCall : public Instruction {
+public:
+    explicit SuperCall(bool is_synthetic, Vector<Register> const& arguments)
+        : Instruction(Type::SuperCall)
+        , m_is_synthetic(is_synthetic)
+        , m_argument_count(arguments.size())
+    {
+        for (size_t i = 0; i < m_argument_count; ++i)
+            m_arguments[i] = arguments[i];
+    }
+
+    ThrowCompletionOr<void> execute_impl(Bytecode::Interpreter&) const;
+    String to_string_impl(Bytecode::Executable const&) const;
+    void replace_references_impl(BasicBlock const&, BasicBlock const&) { }
+
+    size_t length_impl() const
+    {
+        return sizeof(*this) + sizeof(Register) * m_argument_count;
+    }
+
+private:
+    bool m_is_synthetic;
+    size_t m_argument_count { 0 };
+    Register m_arguments[];
+};
+
 class NewClass final : public Instruction {
 public:
     explicit NewClass(ClassExpression const& class_expression)
@@ -966,9 +993,11 @@ ALWAYS_INLINE size_t Instruction::length() const
 {
     if (type() == Type::Call)
         return static_cast<Op::Call const&>(*this).length_impl();
-    else if (type() == Type::NewArray)
+    if (type() == Type::SuperCall)
+        return static_cast<Op::SuperCall const&>(*this).length_impl();
+    if (type() == Type::NewArray)
         return static_cast<Op::NewArray const&>(*this).length_impl();
-    else if (type() == Type::CopyObjectExcludingProperties)
+    if (type() == Type::CopyObjectExcludingProperties)
         return static_cast<Op::CopyObjectExcludingProperties const&>(*this).length_impl();
 
 #define __BYTECODE_OP(op) \