diff --git a/modules/gdscript/gdscript_byte_codegen.cpp b/modules/gdscript/gdscript_byte_codegen.cpp
new file mode 100644
index 00000000000..8f0ce99de65
--- /dev/null
+++ b/modules/gdscript/gdscript_byte_codegen.cpp
@@ -0,0 +1,736 @@
+/*************************************************************************/
+/*  gdscript_byte_codegen.cpp                                            */
+/*************************************************************************/
+/*                       This file is part of:                           */
+/*                           GODOT ENGINE                                */
+/*                      https://godotengine.org                          */
+/*************************************************************************/
+/* Copyright (c) 2007-2020 Juan Linietsky, Ariel Manzur.                 */
+/* Copyright (c) 2014-2020 Godot Engine contributors (cf. AUTHORS.md).   */
+/*                                                                       */
+/* Permission is hereby granted, free of charge, to any person obtaining */
+/* a copy of this software and associated documentation files (the       */
+/* "Software"), to deal in the Software without restriction, including   */
+/* without limitation the rights to use, copy, modify, merge, publish,   */
+/* distribute, sublicense, and/or sell copies of the Software, and to    */
+/* permit persons to whom the Software is furnished to do so, subject to */
+/* the following conditions:                                             */
+/*                                                                       */
+/* The above copyright notice and this permission notice shall be        */
+/* included in all copies or substantial portions of the Software.       */
+/*                                                                       */
+/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,       */
+/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF    */
+/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
+/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY  */
+/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,  */
+/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE     */
+/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
+/*************************************************************************/
+
+#include "gdscript_byte_codegen.h"
+
+#include "core/debugger/engine_debugger.h"
+#include "gdscript.h"
+
+uint32_t GDScriptByteCodeGenerator::add_parameter(const StringName &p_name, bool p_is_optional, const GDScriptDataType &p_type) {
+#ifdef TOOLS_ENABLED
+	function->arg_names.push_back(p_name);
+#endif
+	function->_argument_count++;
+	function->argument_types.push_back(p_type);
+	if (p_is_optional) {
+		if (function->_default_arg_count == 0) {
+			append(GDScriptFunction::OPCODE_JUMP_TO_DEF_ARGUMENT);
+		}
+		function->default_arguments.push_back(opcodes.size());
+		function->_default_arg_count++;
+	}
+
+	return add_local(p_name, p_type);
+}
+
+uint32_t GDScriptByteCodeGenerator::add_local(const StringName &p_name, const GDScriptDataType &p_type) {
+	int stack_pos = increase_stack();
+	add_stack_identifier(p_name, stack_pos);
+	return stack_pos;
+}
+
+uint32_t GDScriptByteCodeGenerator::add_local_constant(const StringName &p_name, const Variant &p_constant) {
+	int index = add_or_get_constant(p_constant);
+	local_constants[p_name] = index;
+	return index;
+}
+
+uint32_t GDScriptByteCodeGenerator::add_or_get_constant(const Variant &p_constant) {
+	if (constant_map.has(p_constant)) {
+		return constant_map[p_constant];
+	}
+	int index = constant_map.size();
+	constant_map[p_constant] = index;
+	return index;
+}
+
+uint32_t GDScriptByteCodeGenerator::add_or_get_name(const StringName &p_name) {
+	return get_name_map_pos(p_name);
+}
+
+uint32_t GDScriptByteCodeGenerator::add_temporary() {
+	current_temporaries++;
+	return increase_stack();
+}
+
+void GDScriptByteCodeGenerator::pop_temporary() {
+	current_stack_size--;
+	current_temporaries--;
+}
+
+void GDScriptByteCodeGenerator::start_parameters() {}
+
+void GDScriptByteCodeGenerator::end_parameters() {
+	function->default_arguments.invert();
+}
+
+void GDScriptByteCodeGenerator::write_start(GDScript *p_script, const StringName &p_function_name, bool p_static, MultiplayerAPI::RPCMode p_rpc_mode, const GDScriptDataType &p_return_type) {
+	function = memnew(GDScriptFunction);
+	debug_stack = EngineDebugger::is_active();
+
+	function->name = p_function_name;
+	function->_script = p_script;
+	function->source = p_script->get_path();
+
+#ifdef DEBUG_ENABLED
+	function->func_cname = (String(function->source) + " - " + String(p_function_name)).utf8();
+	function->_func_cname = function->func_cname.get_data();
+#endif
+
+	function->_static = p_static;
+	function->return_type = p_return_type;
+	function->rpc_mode = p_rpc_mode;
+	function->_argument_count = 0;
+}
+
+GDScriptFunction *GDScriptByteCodeGenerator::write_end() {
+	append(GDScriptFunction::OPCODE_END);
+
+	if (constant_map.size()) {
+		function->_constant_count = constant_map.size();
+		function->constants.resize(constant_map.size());
+		function->_constants_ptr = function->constants.ptrw();
+		const Variant *K = nullptr;
+		while ((K = constant_map.next(K))) {
+			int idx = constant_map[*K];
+			function->constants.write[idx] = *K;
+		}
+	} else {
+		function->_constants_ptr = nullptr;
+		function->_constant_count = 0;
+	}
+
+	if (name_map.size()) {
+		function->global_names.resize(name_map.size());
+		function->_global_names_ptr = &function->global_names[0];
+		for (Map<StringName, int>::Element *E = name_map.front(); E; E = E->next()) {
+			function->global_names.write[E->get()] = E->key();
+		}
+		function->_global_names_count = function->global_names.size();
+
+	} else {
+		function->_global_names_ptr = nullptr;
+		function->_global_names_count = 0;
+	}
+
+	if (opcodes.size()) {
+		function->code = opcodes;
+		function->_code_ptr = &function->code[0];
+		function->_code_size = opcodes.size();
+
+	} else {
+		function->_code_ptr = nullptr;
+		function->_code_size = 0;
+	}
+
+	if (function->default_arguments.size()) {
+		function->_default_arg_count = function->default_arguments.size();
+		function->_default_arg_ptr = &function->default_arguments[0];
+	} else {
+		function->_default_arg_count = 0;
+		function->_default_arg_ptr = nullptr;
+	}
+
+	if (debug_stack) {
+		function->stack_debug = stack_debug;
+	}
+	function->_stack_size = stack_max;
+	function->_call_size = call_max;
+
+	ended = true;
+	return function;
+}
+
+#ifdef DEBUG_ENABLED
+void GDScriptByteCodeGenerator::set_signature(const String &p_signature) {
+	function->profile.signature = p_signature;
+}
+#endif
+
+void GDScriptByteCodeGenerator::set_initial_line(int p_line) {
+	function->_initial_line = p_line;
+}
+
+void GDScriptByteCodeGenerator::write_operator(const Address &p_target, Variant::Operator p_operator, const Address &p_left_operand, const Address &p_right_operand) {
+	append(GDScriptFunction::OPCODE_OPERATOR);
+	append(p_operator);
+	append(p_left_operand);
+	append(p_right_operand);
+	append(p_target);
+}
+
+void GDScriptByteCodeGenerator::write_type_test(const Address &p_target, const Address &p_source, const Address &p_type) {
+	append(GDScriptFunction::OPCODE_EXTENDS_TEST);
+	append(p_source);
+	append(p_type);
+	append(p_target);
+}
+
+void GDScriptByteCodeGenerator::write_type_test_builtin(const Address &p_target, const Address &p_source, Variant::Type p_type) {
+	append(GDScriptFunction::OPCODE_IS_BUILTIN);
+	append(p_source);
+	append(p_type);
+	append(p_target);
+}
+
+void GDScriptByteCodeGenerator::write_and_left_operand(const Address &p_left_operand) {
+	append(GDScriptFunction::OPCODE_JUMP_IF_NOT);
+	append(p_left_operand);
+	logic_op_jump_pos1.push_back(opcodes.size());
+	append(0); // Jump target, will be patched.
+}
+
+void GDScriptByteCodeGenerator::write_and_right_operand(const Address &p_right_operand) {
+	append(GDScriptFunction::OPCODE_JUMP_IF_NOT);
+	append(p_right_operand);
+	logic_op_jump_pos2.push_back(opcodes.size());
+	append(0); // Jump target, will be patched.
+}
+
+void GDScriptByteCodeGenerator::write_end_and(const Address &p_target) {
+	// If here means both operands are true.
+	append(GDScriptFunction::OPCODE_ASSIGN_TRUE);
+	append(p_target);
+	// Jump away from the fail condition.
+	append(GDScriptFunction::OPCODE_JUMP);
+	append(opcodes.size() + 3);
+	// Here it means one of operands is false.
+	patch_jump(logic_op_jump_pos1.back()->get());
+	patch_jump(logic_op_jump_pos2.back()->get());
+	logic_op_jump_pos1.pop_back();
+	logic_op_jump_pos2.pop_back();
+	append(GDScriptFunction::OPCODE_ASSIGN_FALSE);
+	append(p_target);
+}
+
+void GDScriptByteCodeGenerator::write_or_left_operand(const Address &p_left_operand) {
+	append(GDScriptFunction::OPCODE_JUMP_IF);
+	append(p_left_operand);
+	logic_op_jump_pos1.push_back(opcodes.size());
+	append(0); // Jump target, will be patched.
+}
+
+void GDScriptByteCodeGenerator::write_or_right_operand(const Address &p_right_operand) {
+	append(GDScriptFunction::OPCODE_JUMP_IF);
+	append(p_right_operand);
+	logic_op_jump_pos2.push_back(opcodes.size());
+	append(0); // Jump target, will be patched.
+}
+
+void GDScriptByteCodeGenerator::write_end_or(const Address &p_target) {
+	// If here means both operands are false.
+	append(GDScriptFunction::OPCODE_ASSIGN_FALSE);
+	append(p_target);
+	// Jump away from the success condition.
+	append(GDScriptFunction::OPCODE_JUMP);
+	append(opcodes.size() + 3);
+	// Here it means one of operands is false.
+	patch_jump(logic_op_jump_pos1.back()->get());
+	patch_jump(logic_op_jump_pos2.back()->get());
+	logic_op_jump_pos1.pop_back();
+	logic_op_jump_pos2.pop_back();
+	append(GDScriptFunction::OPCODE_ASSIGN_TRUE);
+	append(p_target);
+}
+
+void GDScriptByteCodeGenerator::write_start_ternary(const Address &p_target) {
+	ternary_result.push_back(p_target);
+}
+
+void GDScriptByteCodeGenerator::write_ternary_condition(const Address &p_condition) {
+	append(GDScriptFunction::OPCODE_JUMP_IF_NOT);
+	append(p_condition);
+	ternary_jump_fail_pos.push_back(opcodes.size());
+	append(0); // Jump target, will be patched.
+}
+
+void GDScriptByteCodeGenerator::write_ternary_true_expr(const Address &p_expr) {
+	append(GDScriptFunction::OPCODE_ASSIGN);
+	append(ternary_result.back()->get());
+	append(p_expr);
+	// Jump away from the false path.
+	append(GDScriptFunction::OPCODE_JUMP);
+	ternary_jump_skip_pos.push_back(opcodes.size());
+	append(0);
+	// Fail must jump here.
+	patch_jump(ternary_jump_fail_pos.back()->get());
+	ternary_jump_fail_pos.pop_back();
+}
+
+void GDScriptByteCodeGenerator::write_ternary_false_expr(const Address &p_expr) {
+	append(GDScriptFunction::OPCODE_ASSIGN);
+	append(ternary_result.back()->get());
+	append(p_expr);
+}
+
+void GDScriptByteCodeGenerator::write_end_ternary() {
+	patch_jump(ternary_jump_skip_pos.back()->get());
+	ternary_jump_skip_pos.pop_back();
+}
+
+void GDScriptByteCodeGenerator::write_set(const Address &p_target, const Address &p_index, const Address &p_source) {
+	append(GDScriptFunction::OPCODE_SET);
+	append(p_target);
+	append(p_index);
+	append(p_source);
+}
+
+void GDScriptByteCodeGenerator::write_get(const Address &p_target, const Address &p_index, const Address &p_source) {
+	append(GDScriptFunction::OPCODE_GET);
+	append(p_source);
+	append(p_index);
+	append(p_target);
+}
+
+void GDScriptByteCodeGenerator::write_set_named(const Address &p_target, const StringName &p_name, const Address &p_source) {
+	append(GDScriptFunction::OPCODE_SET_NAMED);
+	append(p_target);
+	append(p_name);
+	append(p_source);
+}
+
+void GDScriptByteCodeGenerator::write_get_named(const Address &p_target, const StringName &p_name, const Address &p_source) {
+	append(GDScriptFunction::OPCODE_GET_NAMED);
+	append(p_source);
+	append(p_name);
+	append(p_target);
+}
+
+void GDScriptByteCodeGenerator::write_set_member(const Address &p_value, const StringName &p_name) {
+	append(GDScriptFunction::OPCODE_SET_MEMBER);
+	append(p_name);
+	append(p_value);
+}
+
+void GDScriptByteCodeGenerator::write_get_member(const Address &p_target, const StringName &p_name) {
+	append(GDScriptFunction::OPCODE_GET_MEMBER);
+	append(p_name);
+	append(p_target);
+}
+
+void GDScriptByteCodeGenerator::write_assign(const Address &p_target, const Address &p_source) {
+	if (p_target.type.has_type && !p_source.type.has_type) {
+		// Typed assignment.
+		switch (p_target.type.kind) {
+			case GDScriptDataType::BUILTIN: {
+				append(GDScriptFunction::OPCODE_ASSIGN_TYPED_BUILTIN);
+				append(p_target.type.builtin_type);
+				append(p_target);
+				append(p_source);
+			} break;
+			case GDScriptDataType::NATIVE: {
+				int class_idx = GDScriptLanguage::get_singleton()->get_global_map()[p_target.type.native_type];
+				class_idx |= (GDScriptFunction::ADDR_TYPE_GLOBAL << GDScriptFunction::ADDR_BITS);
+				append(GDScriptFunction::OPCODE_ASSIGN_TYPED_NATIVE);
+				append(class_idx);
+				append(p_target);
+				append(p_source);
+			} break;
+			case GDScriptDataType::SCRIPT:
+			case GDScriptDataType::GDSCRIPT: {
+				Variant script = p_target.type.script_type;
+				int idx = get_constant_pos(script);
+
+				append(GDScriptFunction::OPCODE_ASSIGN_TYPED_SCRIPT);
+				append(idx);
+				append(p_target);
+				append(p_source);
+			} break;
+			default: {
+				ERR_PRINT("Compiler bug: unresolved assign.");
+
+				// Shouldn't get here, but fail-safe to a regular assignment
+				append(GDScriptFunction::OPCODE_ASSIGN);
+				append(p_target);
+				append(p_source);
+			}
+		}
+	} else {
+		if (p_target.type.kind == GDScriptDataType::BUILTIN && p_source.type.kind == GDScriptDataType::BUILTIN && p_target.type.builtin_type != p_source.type.builtin_type) {
+			// Need conversion..
+			append(GDScriptFunction::OPCODE_ASSIGN_TYPED_BUILTIN);
+			append(p_target.type.builtin_type);
+			append(p_target);
+			append(p_source);
+		} else {
+			// Either untyped assignment or already type-checked by the parser
+			append(GDScriptFunction::OPCODE_ASSIGN);
+			append(p_target);
+			append(p_source);
+		}
+	}
+}
+
+void GDScriptByteCodeGenerator::write_assign_true(const Address &p_target) {
+	append(GDScriptFunction::OPCODE_ASSIGN_TRUE);
+	append(p_target);
+}
+
+void GDScriptByteCodeGenerator::write_assign_false(const Address &p_target) {
+	append(GDScriptFunction::OPCODE_ASSIGN_FALSE);
+	append(p_target);
+}
+
+void GDScriptByteCodeGenerator::write_cast(const Address &p_target, const Address &p_source, const GDScriptDataType &p_type) {
+	switch (p_type.kind) {
+		case GDScriptDataType::BUILTIN: {
+			append(GDScriptFunction::OPCODE_CAST_TO_BUILTIN);
+			append(p_type.builtin_type);
+		} break;
+		case GDScriptDataType::NATIVE: {
+			int class_idx = GDScriptLanguage::get_singleton()->get_global_map()[p_type.native_type];
+			class_idx |= (GDScriptFunction::ADDR_TYPE_GLOBAL << GDScriptFunction::ADDR_BITS);
+			append(GDScriptFunction::OPCODE_CAST_TO_NATIVE);
+			append(class_idx);
+		} break;
+		case GDScriptDataType::SCRIPT:
+		case GDScriptDataType::GDSCRIPT: {
+			Variant script = p_type.script_type;
+			int idx = get_constant_pos(script);
+
+			append(GDScriptFunction::OPCODE_CAST_TO_SCRIPT);
+			append(idx);
+		} break;
+		default: {
+			return;
+		}
+	}
+
+	append(p_source);
+	append(p_target);
+}
+
+void GDScriptByteCodeGenerator::write_call(const Address &p_target, const Address &p_base, const StringName &p_function_name, const Vector<Address> &p_arguments) {
+	append(p_target.mode == Address::NIL ? GDScriptFunction::OPCODE_CALL : GDScriptFunction::OPCODE_CALL_RETURN);
+	append(p_arguments.size());
+	append(p_base);
+	append(p_function_name);
+	for (int i = 0; i < p_arguments.size(); i++) {
+		append(p_arguments[i]);
+	}
+	append(p_target);
+	alloc_call(p_arguments.size());
+}
+
+void GDScriptByteCodeGenerator::write_super_call(const Address &p_target, const StringName &p_function_name, const Vector<Address> &p_arguments) {
+	append(GDScriptFunction::OPCODE_CALL_SELF_BASE);
+	append(p_function_name);
+	append(p_arguments.size());
+	for (int i = 0; i < p_arguments.size(); i++) {
+		append(p_arguments[i]);
+	}
+	append(p_target);
+	alloc_call(p_arguments.size());
+}
+
+void GDScriptByteCodeGenerator::write_call_async(const Address &p_target, const Address &p_base, const StringName &p_function_name, const Vector<Address> &p_arguments) {
+	append(GDScriptFunction::OPCODE_CALL_ASYNC);
+	append(p_arguments.size());
+	append(p_base);
+	append(p_function_name);
+	for (int i = 0; i < p_arguments.size(); i++) {
+		append(p_arguments[i]);
+	}
+	append(p_target);
+	alloc_call(p_arguments.size());
+}
+
+void GDScriptByteCodeGenerator::write_call_builtin(const Address &p_target, GDScriptFunctions::Function p_function, const Vector<Address> &p_arguments) {
+	append(GDScriptFunction::OPCODE_CALL_BUILT_IN);
+	append(p_function);
+	append(p_arguments.size());
+	for (int i = 0; i < p_arguments.size(); i++) {
+		append(p_arguments[i]);
+	}
+	append(p_target);
+	alloc_call(p_arguments.size());
+}
+
+void GDScriptByteCodeGenerator::write_call_method_bind(const Address &p_target, const Address &p_base, const MethodBind *p_method, const Vector<Address> &p_arguments) {
+	append(p_target.mode == Address::NIL ? GDScriptFunction::OPCODE_CALL : GDScriptFunction::OPCODE_CALL_RETURN);
+	append(p_arguments.size());
+	append(p_base);
+	append(p_method->get_name());
+	for (int i = 0; i < p_arguments.size(); i++) {
+		append(p_arguments[i]);
+	}
+	append(p_target);
+	alloc_call(p_arguments.size());
+}
+
+void GDScriptByteCodeGenerator::write_call_ptrcall(const Address &p_target, const Address &p_base, const MethodBind *p_method, const Vector<Address> &p_arguments) {
+	append(p_target.mode == Address::NIL ? GDScriptFunction::OPCODE_CALL : GDScriptFunction::OPCODE_CALL_RETURN);
+	append(p_arguments.size());
+	append(p_base);
+	append(p_method->get_name());
+	for (int i = 0; i < p_arguments.size(); i++) {
+		append(p_arguments[i]);
+	}
+	append(p_target);
+	alloc_call(p_arguments.size());
+}
+
+void GDScriptByteCodeGenerator::write_call_self(const Address &p_target, const StringName &p_function_name, const Vector<Address> &p_arguments) {
+	append(p_target.mode == Address::NIL ? GDScriptFunction::OPCODE_CALL : GDScriptFunction::OPCODE_CALL_RETURN);
+	append(p_arguments.size());
+	append(GDScriptFunction::ADDR_TYPE_SELF << GDScriptFunction::ADDR_BITS);
+	append(p_function_name);
+	for (int i = 0; i < p_arguments.size(); i++) {
+		append(p_arguments[i]);
+	}
+	append(p_target);
+	alloc_call(p_arguments.size());
+}
+
+void GDScriptByteCodeGenerator::write_call_script_function(const Address &p_target, const Address &p_base, const StringName &p_function_name, const Vector<Address> &p_arguments) {
+	append(p_target.mode == Address::NIL ? GDScriptFunction::OPCODE_CALL : GDScriptFunction::OPCODE_CALL_RETURN);
+	append(p_arguments.size());
+	append(p_base);
+	append(p_function_name);
+	for (int i = 0; i < p_arguments.size(); i++) {
+		append(p_arguments[i]);
+	}
+	append(p_target);
+	alloc_call(p_arguments.size());
+}
+
+void GDScriptByteCodeGenerator::write_construct(const Address &p_target, Variant::Type p_type, const Vector<Address> &p_arguments) {
+	append(GDScriptFunction::OPCODE_CONSTRUCT);
+	append(p_type);
+	append(p_arguments.size());
+	for (int i = 0; i < p_arguments.size(); i++) {
+		append(p_arguments[i]);
+	}
+	append(p_target);
+}
+
+void GDScriptByteCodeGenerator::write_construct_array(const Address &p_target, const Vector<Address> &p_arguments) {
+	append(GDScriptFunction::OPCODE_CONSTRUCT_ARRAY);
+	append(p_arguments.size());
+	for (int i = 0; i < p_arguments.size(); i++) {
+		append(p_arguments[i]);
+	}
+	append(p_target);
+}
+
+void GDScriptByteCodeGenerator::write_construct_dictionary(const Address &p_target, const Vector<Address> &p_arguments) {
+	append(GDScriptFunction::OPCODE_CONSTRUCT_DICTIONARY);
+	append(p_arguments.size() / 2); // This is number of key-value pairs, so only half of actual arguments.
+	for (int i = 0; i < p_arguments.size(); i++) {
+		append(p_arguments[i]);
+	}
+	append(p_target);
+}
+
+void GDScriptByteCodeGenerator::write_await(const Address &p_target, const Address &p_operand) {
+	append(GDScriptFunction::OPCODE_AWAIT);
+	append(p_operand);
+	append(GDScriptFunction::OPCODE_AWAIT_RESUME);
+	append(p_target);
+}
+
+void GDScriptByteCodeGenerator::write_if(const Address &p_condition) {
+	append(GDScriptFunction::OPCODE_JUMP_IF_NOT);
+	append(p_condition);
+	if_jmp_addrs.push_back(opcodes.size());
+	append(0); // Jump destination, will be patched.
+}
+
+void GDScriptByteCodeGenerator::write_else() {
+	append(GDScriptFunction::OPCODE_JUMP); // Jump from true if block;
+	int else_jmp_addr = opcodes.size();
+	append(0); // Jump destination, will be patched.
+
+	patch_jump(if_jmp_addrs.back()->get());
+	if_jmp_addrs.pop_back();
+	if_jmp_addrs.push_back(else_jmp_addr);
+}
+
+void GDScriptByteCodeGenerator::write_endif() {
+	patch_jump(if_jmp_addrs.back()->get());
+	if_jmp_addrs.pop_back();
+}
+
+void GDScriptByteCodeGenerator::write_for(const Address &p_variable, const Address &p_list) {
+	int counter_pos = increase_stack() | (GDScriptFunction::ADDR_TYPE_STACK << GDScriptFunction::ADDR_BITS);
+	int container_pos = increase_stack() | (GDScriptFunction::ADDR_TYPE_STACK << GDScriptFunction::ADDR_BITS);
+
+	current_breaks_to_patch.push_back(List<int>());
+
+	// Assign container.
+	append(GDScriptFunction::OPCODE_ASSIGN);
+	append(container_pos);
+	append(p_list);
+
+	// Begin loop.
+	append(GDScriptFunction::OPCODE_ITERATE_BEGIN);
+	append(counter_pos);
+	append(container_pos);
+	for_jmp_addrs.push_back(opcodes.size());
+	append(0); // End of loop address, will be patched.
+	append(p_variable);
+	append(GDScriptFunction::OPCODE_JUMP);
+	append(opcodes.size() + 6); // Skip over 'continue' code.
+
+	// Next iteration.
+	int continue_addr = opcodes.size();
+	continue_addrs.push_back(continue_addr);
+	append(GDScriptFunction::OPCODE_ITERATE);
+	append(counter_pos);
+	append(container_pos);
+	for_jmp_addrs.push_back(opcodes.size());
+	append(0); // Jump destination, will be patched.
+	append(p_variable);
+}
+
+void GDScriptByteCodeGenerator::write_endfor() {
+	// Jump back to loop check.
+	append(GDScriptFunction::OPCODE_JUMP);
+	append(continue_addrs.back()->get());
+	continue_addrs.pop_back();
+
+	// Patch end jumps (two of them).
+	for (int i = 0; i < 2; i++) {
+		patch_jump(for_jmp_addrs.back()->get());
+		for_jmp_addrs.pop_back();
+	}
+
+	// Patch break statements.
+	for (const List<int>::Element *E = current_breaks_to_patch.back()->get().front(); E; E = E->next()) {
+		patch_jump(E->get());
+	}
+	current_breaks_to_patch.pop_back();
+
+	current_stack_size -= 2; // Remove loop temporaries.
+}
+
+void GDScriptByteCodeGenerator::start_while_condition() {
+	current_breaks_to_patch.push_back(List<int>());
+	continue_addrs.push_back(opcodes.size());
+}
+
+void GDScriptByteCodeGenerator::write_while(const Address &p_condition) {
+	// Condition check.
+	append(GDScriptFunction::OPCODE_JUMP_IF_NOT);
+	append(p_condition);
+	while_jmp_addrs.push_back(opcodes.size());
+	append(0); // End of loop address, will be patched.
+}
+
+void GDScriptByteCodeGenerator::write_endwhile() {
+	// Jump back to loop check.
+	append(GDScriptFunction::OPCODE_JUMP);
+	append(continue_addrs.back()->get());
+	continue_addrs.pop_back();
+
+	// Patch end jump.
+	patch_jump(while_jmp_addrs.back()->get());
+	while_jmp_addrs.pop_back();
+
+	// Patch break statements.
+	for (const List<int>::Element *E = current_breaks_to_patch.back()->get().front(); E; E = E->next()) {
+		patch_jump(E->get());
+	}
+	current_breaks_to_patch.pop_back();
+}
+
+void GDScriptByteCodeGenerator::start_match() {
+	match_continues_to_patch.push_back(List<int>());
+}
+
+void GDScriptByteCodeGenerator::start_match_branch() {
+	// Patch continue statements.
+	for (const List<int>::Element *E = match_continues_to_patch.back()->get().front(); E; E = E->next()) {
+		patch_jump(E->get());
+	}
+	match_continues_to_patch.pop_back();
+	// Start a new list for next branch.
+	match_continues_to_patch.push_back(List<int>());
+}
+
+void GDScriptByteCodeGenerator::end_match() {
+	// Patch continue statements.
+	for (const List<int>::Element *E = match_continues_to_patch.back()->get().front(); E; E = E->next()) {
+		patch_jump(E->get());
+	}
+	match_continues_to_patch.pop_back();
+}
+
+void GDScriptByteCodeGenerator::write_break() {
+	append(GDScriptFunction::OPCODE_JUMP);
+	current_breaks_to_patch.back()->get().push_back(opcodes.size());
+	append(0);
+}
+
+void GDScriptByteCodeGenerator::write_continue() {
+	append(GDScriptFunction::OPCODE_JUMP);
+	append(continue_addrs.back()->get());
+}
+
+void GDScriptByteCodeGenerator::write_continue_match() {
+	append(GDScriptFunction::OPCODE_JUMP);
+	match_continues_to_patch.back()->get().push_back(opcodes.size());
+	append(0);
+}
+
+void GDScriptByteCodeGenerator::write_breakpoint() {
+	append(GDScriptFunction::OPCODE_BREAKPOINT);
+}
+
+void GDScriptByteCodeGenerator::write_newline(int p_line) {
+	append(GDScriptFunction::OPCODE_LINE);
+	append(p_line);
+	current_line = p_line;
+}
+
+void GDScriptByteCodeGenerator::write_return(const Address &p_return_value) {
+	append(GDScriptFunction::OPCODE_RETURN);
+	append(p_return_value);
+}
+
+void GDScriptByteCodeGenerator::write_assert(const Address &p_test, const Address &p_message) {
+	append(GDScriptFunction::OPCODE_ASSERT);
+	append(p_test);
+	append(p_message);
+}
+
+void GDScriptByteCodeGenerator::start_block() {
+	push_stack_identifiers();
+}
+
+void GDScriptByteCodeGenerator::end_block() {
+	pop_stack_identifiers();
+}
+
+GDScriptByteCodeGenerator::~GDScriptByteCodeGenerator() {
+	if (!ended && function != nullptr) {
+		memdelete(function);
+	}
+}
diff --git a/modules/gdscript/gdscript_byte_codegen.h b/modules/gdscript/gdscript_byte_codegen.h
new file mode 100644
index 00000000000..62438b6dd2e
--- /dev/null
+++ b/modules/gdscript/gdscript_byte_codegen.h
@@ -0,0 +1,277 @@
+/*************************************************************************/
+/*  gdscript_byte_codegen.h                                              */
+/*************************************************************************/
+/*                       This file is part of:                           */
+/*                           GODOT ENGINE                                */
+/*                      https://godotengine.org                          */
+/*************************************************************************/
+/* Copyright (c) 2007-2020 Juan Linietsky, Ariel Manzur.                 */
+/* Copyright (c) 2014-2020 Godot Engine contributors (cf. AUTHORS.md).   */
+/*                                                                       */
+/* Permission is hereby granted, free of charge, to any person obtaining */
+/* a copy of this software and associated documentation files (the       */
+/* "Software"), to deal in the Software without restriction, including   */
+/* without limitation the rights to use, copy, modify, merge, publish,   */
+/* distribute, sublicense, and/or sell copies of the Software, and to    */
+/* permit persons to whom the Software is furnished to do so, subject to */
+/* the following conditions:                                             */
+/*                                                                       */
+/* The above copyright notice and this permission notice shall be        */
+/* included in all copies or substantial portions of the Software.       */
+/*                                                                       */
+/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,       */
+/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF    */
+/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
+/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY  */
+/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,  */
+/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE     */
+/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
+/*************************************************************************/
+
+#ifndef GDSCRIPT_BYTE_CODEGEN
+#define GDSCRIPT_BYTE_CODEGEN
+
+#include "gdscript_codegen.h"
+
+class GDScriptByteCodeGenerator : public GDScriptCodeGenerator {
+	bool ended = false;
+	GDScriptFunction *function = nullptr;
+	bool debug_stack = false;
+
+	Vector<int> opcodes;
+	List<Map<StringName, int>> stack_id_stack;
+	Map<StringName, int> stack_identifiers;
+	Map<StringName, int> local_constants;
+
+	List<GDScriptFunction::StackDebug> stack_debug;
+	List<Map<StringName, int>> block_identifier_stack;
+	Map<StringName, int> block_identifiers;
+
+	int current_stack_size = 0;
+	int current_temporaries = 0;
+
+	HashMap<Variant, int, VariantHasher, VariantComparator> constant_map;
+	Map<StringName, int> name_map;
+#ifdef TOOLS_ENABLED
+	Vector<StringName> named_globals;
+#endif
+	int current_line = 0;
+	int stack_max = 0;
+	int call_max = 0;
+
+	List<int> if_jmp_addrs; // List since this can be nested.
+	List<int> for_jmp_addrs;
+	List<int> while_jmp_addrs;
+	List<int> continue_addrs;
+
+	// Used to patch jumps with `and` and `or` operators with short-circuit.
+	List<int> logic_op_jump_pos1;
+	List<int> logic_op_jump_pos2;
+
+	List<Address> ternary_result;
+	List<int> ternary_jump_fail_pos;
+	List<int> ternary_jump_skip_pos;
+
+	List<List<int>> current_breaks_to_patch;
+	List<List<int>> match_continues_to_patch;
+
+	void add_stack_identifier(const StringName &p_id, int p_stackpos) {
+		stack_identifiers[p_id] = p_stackpos;
+		if (debug_stack) {
+			block_identifiers[p_id] = p_stackpos;
+			GDScriptFunction::StackDebug sd;
+			sd.added = true;
+			sd.line = current_line;
+			sd.identifier = p_id;
+			sd.pos = p_stackpos;
+			stack_debug.push_back(sd);
+		}
+	}
+
+	void push_stack_identifiers() {
+		stack_id_stack.push_back(stack_identifiers);
+		if (debug_stack) {
+			block_identifier_stack.push_back(block_identifiers);
+			block_identifiers.clear();
+		}
+	}
+
+	void pop_stack_identifiers() {
+		stack_identifiers = stack_id_stack.back()->get();
+		current_stack_size = stack_identifiers.size() + current_temporaries;
+		stack_id_stack.pop_back();
+
+		if (debug_stack) {
+			for (Map<StringName, int>::Element *E = block_identifiers.front(); E; E = E->next()) {
+				GDScriptFunction::StackDebug sd;
+				sd.added = false;
+				sd.identifier = E->key();
+				sd.line = current_line;
+				sd.pos = E->get();
+				stack_debug.push_back(sd);
+			}
+			block_identifiers = block_identifier_stack.back()->get();
+			block_identifier_stack.pop_back();
+		}
+	}
+
+	int get_name_map_pos(const StringName &p_identifier) {
+		int ret;
+		if (!name_map.has(p_identifier)) {
+			ret = name_map.size();
+			name_map[p_identifier] = ret;
+		} else {
+			ret = name_map[p_identifier];
+		}
+		return ret;
+	}
+
+	int get_constant_pos(const Variant &p_constant) {
+		if (constant_map.has(p_constant))
+			return constant_map[p_constant];
+		int pos = constant_map.size();
+		constant_map[p_constant] = pos;
+		return pos;
+	}
+
+	void alloc_stack(int p_level) {
+		if (p_level >= stack_max)
+			stack_max = p_level + 1;
+	}
+
+	void alloc_call(int p_params) {
+		if (p_params >= call_max)
+			call_max = p_params;
+	}
+
+	int increase_stack() {
+		int top = current_stack_size++;
+		alloc_stack(current_stack_size);
+		return top;
+	}
+
+	int address_of(const Address &p_address) {
+		switch (p_address.mode) {
+			case Address::SELF:
+				return GDScriptFunction::ADDR_TYPE_SELF << GDScriptFunction::ADDR_BITS;
+			case Address::CLASS:
+				return GDScriptFunction::ADDR_TYPE_CLASS << GDScriptFunction::ADDR_BITS;
+			case Address::MEMBER:
+				return p_address.address | (GDScriptFunction::ADDR_TYPE_MEMBER << GDScriptFunction::ADDR_BITS);
+			case Address::CLASS_CONSTANT:
+				return p_address.address | (GDScriptFunction::ADDR_TYPE_CLASS_CONSTANT << GDScriptFunction::ADDR_BITS);
+			case Address::LOCAL_CONSTANT:
+			case Address::CONSTANT:
+				return p_address.address | (GDScriptFunction::ADDR_TYPE_LOCAL_CONSTANT << GDScriptFunction::ADDR_BITS);
+			case Address::LOCAL_VARIABLE:
+			case Address::TEMPORARY:
+			case Address::FUNCTION_PARAMETER:
+				return p_address.address | (GDScriptFunction::ADDR_TYPE_STACK << GDScriptFunction::ADDR_BITS);
+			case Address::GLOBAL:
+				return p_address.address | (GDScriptFunction::ADDR_TYPE_GLOBAL << GDScriptFunction::ADDR_BITS);
+			case Address::NAMED_GLOBAL:
+				return p_address.address | (GDScriptFunction::ADDR_TYPE_NAMED_GLOBAL << GDScriptFunction::ADDR_BITS);
+			case Address::NIL:
+				return GDScriptFunction::ADDR_TYPE_NIL << GDScriptFunction::ADDR_BITS;
+		}
+		return -1; // Unreachable.
+	}
+
+	void append(int code) {
+		opcodes.push_back(code);
+	}
+
+	void append(const Address &p_address) {
+		opcodes.push_back(address_of(p_address));
+	}
+
+	void append(const StringName &p_name) {
+		opcodes.push_back(get_name_map_pos(p_name));
+	}
+
+	void patch_jump(int p_address) {
+		opcodes.write[p_address] = opcodes.size();
+	}
+
+public:
+	virtual uint32_t add_parameter(const StringName &p_name, bool p_is_optional, const GDScriptDataType &p_type) override;
+	virtual uint32_t add_local(const StringName &p_name, const GDScriptDataType &p_type) override;
+	virtual uint32_t add_local_constant(const StringName &p_name, const Variant &p_constant) override;
+	virtual uint32_t add_or_get_constant(const Variant &p_constant) override;
+	virtual uint32_t add_or_get_name(const StringName &p_name) override;
+	virtual uint32_t add_temporary() override;
+	virtual void pop_temporary() override;
+
+	virtual void start_parameters() override;
+	virtual void end_parameters() override;
+
+	virtual void start_block() override;
+	virtual void end_block() override;
+
+	virtual void write_start(GDScript *p_script, const StringName &p_function_name, bool p_static, MultiplayerAPI::RPCMode p_rpc_mode, const GDScriptDataType &p_return_type) override;
+	virtual GDScriptFunction *write_end() override;
+
+#ifdef DEBUG_ENABLED
+	virtual void set_signature(const String &p_signature) override;
+#endif
+	virtual void set_initial_line(int p_line) override;
+
+	virtual void write_operator(const Address &p_target, Variant::Operator p_operator, const Address &p_left_operand, const Address &p_right_operand) override;
+	virtual void write_type_test(const Address &p_target, const Address &p_source, const Address &p_type) override;
+	virtual void write_type_test_builtin(const Address &p_target, const Address &p_source, Variant::Type p_type) override;
+	virtual void write_and_left_operand(const Address &p_left_operand) override;
+	virtual void write_and_right_operand(const Address &p_right_operand) override;
+	virtual void write_end_and(const Address &p_target) override;
+	virtual void write_or_left_operand(const Address &p_left_operand) override;
+	virtual void write_or_right_operand(const Address &p_right_operand) override;
+	virtual void write_end_or(const Address &p_target) override;
+	virtual void write_start_ternary(const Address &p_target) override;
+	virtual void write_ternary_condition(const Address &p_condition) override;
+	virtual void write_ternary_true_expr(const Address &p_expr) override;
+	virtual void write_ternary_false_expr(const Address &p_expr) override;
+	virtual void write_end_ternary() override;
+	virtual void write_set(const Address &p_target, const Address &p_index, const Address &p_source) override;
+	virtual void write_get(const Address &p_target, const Address &p_index, const Address &p_source) override;
+	virtual void write_set_named(const Address &p_target, const StringName &p_name, const Address &p_source) override;
+	virtual void write_get_named(const Address &p_target, const StringName &p_name, const Address &p_source) override;
+	virtual void write_set_member(const Address &p_value, const StringName &p_name) override;
+	virtual void write_get_member(const Address &p_target, const StringName &p_name) override;
+	virtual void write_assign(const Address &p_target, const Address &p_source) override;
+	virtual void write_assign_true(const Address &p_target) override;
+	virtual void write_assign_false(const Address &p_target) override;
+	virtual void write_cast(const Address &p_target, const Address &p_source, const GDScriptDataType &p_type) override;
+	virtual void write_call(const Address &p_target, const Address &p_base, const StringName &p_function_name, const Vector<Address> &p_arguments) override;
+	virtual void write_super_call(const Address &p_target, const StringName &p_function_name, const Vector<Address> &p_arguments) override;
+	virtual void write_call_async(const Address &p_target, const Address &p_base, const StringName &p_function_name, const Vector<Address> &p_arguments) override;
+	virtual void write_call_builtin(const Address &p_target, GDScriptFunctions::Function p_function, const Vector<Address> &p_arguments) override;
+	virtual void write_call_method_bind(const Address &p_target, const Address &p_base, const MethodBind *p_method, const Vector<Address> &p_arguments) override;
+	virtual void write_call_ptrcall(const Address &p_target, const Address &p_base, const MethodBind *p_method, const Vector<Address> &p_arguments) override;
+	virtual void write_call_self(const Address &p_target, const StringName &p_function_name, const Vector<Address> &p_arguments) override;
+	virtual void write_call_script_function(const Address &p_target, const Address &p_base, const StringName &p_function_name, const Vector<Address> &p_arguments) override;
+	virtual void write_construct(const Address &p_target, Variant::Type p_type, const Vector<Address> &p_arguments) override;
+	virtual void write_construct_array(const Address &p_target, const Vector<Address> &p_arguments) override;
+	virtual void write_construct_dictionary(const Address &p_target, const Vector<Address> &p_arguments) override;
+	virtual void write_await(const Address &p_target, const Address &p_operand) override;
+	virtual void write_if(const Address &p_condition) override;
+	virtual void write_else() override;
+	virtual void write_endif() override;
+	virtual void write_for(const Address &p_variable, const Address &p_list) override;
+	virtual void write_endfor() override;
+	virtual void start_while_condition() override;
+	virtual void write_while(const Address &p_condition) override;
+	virtual void write_endwhile() override;
+	virtual void start_match() override;
+	virtual void start_match_branch() override;
+	virtual void end_match() override;
+	virtual void write_break() override;
+	virtual void write_continue() override;
+	virtual void write_continue_match() override;
+	virtual void write_breakpoint() override;
+	virtual void write_newline(int p_line) override;
+	virtual void write_return(const Address &p_return_value) override;
+	virtual void write_assert(const Address &p_test, const Address &p_message) override;
+
+	virtual ~GDScriptByteCodeGenerator();
+};
+
+#endif // GDSCRIPT_BYTE_CODEGEN
diff --git a/modules/gdscript/gdscript_codegen.h b/modules/gdscript/gdscript_codegen.h
new file mode 100644
index 00000000000..31e1e6ba23c
--- /dev/null
+++ b/modules/gdscript/gdscript_codegen.h
@@ -0,0 +1,160 @@
+/*************************************************************************/
+/*  gdscript_codegen.h                                                   */
+/*************************************************************************/
+/*                       This file is part of:                           */
+/*                           GODOT ENGINE                                */
+/*                      https://godotengine.org                          */
+/*************************************************************************/
+/* Copyright (c) 2007-2020 Juan Linietsky, Ariel Manzur.                 */
+/* Copyright (c) 2014-2020 Godot Engine contributors (cf. AUTHORS.md).   */
+/*                                                                       */
+/* Permission is hereby granted, free of charge, to any person obtaining */
+/* a copy of this software and associated documentation files (the       */
+/* "Software"), to deal in the Software without restriction, including   */
+/* without limitation the rights to use, copy, modify, merge, publish,   */
+/* distribute, sublicense, and/or sell copies of the Software, and to    */
+/* permit persons to whom the Software is furnished to do so, subject to */
+/* the following conditions:                                             */
+/*                                                                       */
+/* The above copyright notice and this permission notice shall be        */
+/* included in all copies or substantial portions of the Software.       */
+/*                                                                       */
+/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,       */
+/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF    */
+/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
+/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY  */
+/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,  */
+/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE     */
+/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
+/*************************************************************************/
+
+#ifndef GDSCRIPT_CODEGEN
+#define GDSCRIPT_CODEGEN
+
+#include "core/io/multiplayer_api.h"
+#include "core/string_name.h"
+#include "core/variant.h"
+#include "gdscript_function.h"
+#include "gdscript_functions.h"
+
+class GDScriptCodeGenerator {
+public:
+	struct Address {
+		enum AddressMode {
+			SELF,
+			CLASS,
+			MEMBER,
+			CONSTANT,
+			CLASS_CONSTANT,
+			LOCAL_CONSTANT,
+			LOCAL_VARIABLE,
+			FUNCTION_PARAMETER,
+			TEMPORARY,
+			GLOBAL,
+			NAMED_GLOBAL,
+			NIL,
+		};
+		AddressMode mode = NIL;
+		uint32_t address = 0;
+		GDScriptDataType type;
+
+		Address() {}
+		Address(AddressMode p_mode, const GDScriptDataType &p_type = GDScriptDataType()) {
+			mode = p_mode;
+			type = p_type;
+		}
+		Address(AddressMode p_mode, uint32_t p_address, const GDScriptDataType &p_type = GDScriptDataType()) {
+			mode = p_mode,
+			address = p_address;
+			type = p_type;
+		}
+	};
+
+	virtual uint32_t add_parameter(const StringName &p_name, bool p_is_optional, const GDScriptDataType &p_type) = 0;
+	virtual uint32_t add_local(const StringName &p_name, const GDScriptDataType &p_type) = 0;
+	virtual uint32_t add_local_constant(const StringName &p_name, const Variant &p_constant) = 0;
+	virtual uint32_t add_or_get_constant(const Variant &p_constant) = 0;
+	virtual uint32_t add_or_get_name(const StringName &p_name) = 0;
+	virtual uint32_t add_temporary() = 0;
+	virtual void pop_temporary() = 0;
+
+	virtual void start_parameters() = 0;
+	virtual void end_parameters() = 0;
+
+	virtual void start_block() = 0;
+	virtual void end_block() = 0;
+
+	// virtual int get_max_stack_level() = 0;
+	// virtual int get_max_function_arguments() = 0;
+
+	virtual void write_start(GDScript *p_script, const StringName &p_function_name, bool p_static, MultiplayerAPI::RPCMode p_rpc_mode, const GDScriptDataType &p_return_type) = 0;
+	virtual GDScriptFunction *write_end() = 0;
+
+#ifdef DEBUG_ENABLED
+	virtual void set_signature(const String &p_signature) = 0;
+#endif
+	virtual void set_initial_line(int p_line) = 0;
+
+	// virtual void alloc_stack(int p_level) = 0; // Is this needed?
+	// virtual void alloc_call(int p_arg_count) = 0; // This might be automatic from other functions.
+
+	virtual void write_operator(const Address &p_target, Variant::Operator p_operator, const Address &p_left_operand, const Address &p_right_operand) = 0;
+	virtual void write_type_test(const Address &p_target, const Address &p_source, const Address &p_type) = 0;
+	virtual void write_type_test_builtin(const Address &p_target, const Address &p_source, Variant::Type p_type) = 0;
+	virtual void write_and_left_operand(const Address &p_left_operand) = 0;
+	virtual void write_and_right_operand(const Address &p_right_operand) = 0;
+	virtual void write_end_and(const Address &p_target) = 0;
+	virtual void write_or_left_operand(const Address &p_left_operand) = 0;
+	virtual void write_or_right_operand(const Address &p_right_operand) = 0;
+	virtual void write_end_or(const Address &p_target) = 0;
+	virtual void write_start_ternary(const Address &p_target) = 0;
+	virtual void write_ternary_condition(const Address &p_condition) = 0;
+	virtual void write_ternary_true_expr(const Address &p_expr) = 0;
+	virtual void write_ternary_false_expr(const Address &p_expr) = 0;
+	virtual void write_end_ternary() = 0;
+	virtual void write_set(const Address &p_target, const Address &p_index, const Address &p_source) = 0;
+	virtual void write_get(const Address &p_target, const Address &p_index, const Address &p_source) = 0;
+	virtual void write_set_named(const Address &p_target, const StringName &p_name, const Address &p_source) = 0;
+	virtual void write_get_named(const Address &p_target, const StringName &p_name, const Address &p_source) = 0;
+	virtual void write_set_member(const Address &p_value, const StringName &p_name) = 0;
+	virtual void write_get_member(const Address &p_target, const StringName &p_name) = 0;
+	virtual void write_assign(const Address &p_target, const Address &p_source) = 0;
+	virtual void write_assign_true(const Address &p_target) = 0;
+	virtual void write_assign_false(const Address &p_target) = 0;
+	virtual void write_cast(const Address &p_target, const Address &p_source, const GDScriptDataType &p_type) = 0;
+	virtual void write_call(const Address &p_target, const Address &p_base, const StringName &p_function_name, const Vector<Address> &p_arguments) = 0;
+	virtual void write_super_call(const Address &p_target, const StringName &p_function_name, const Vector<Address> &p_arguments) = 0;
+	virtual void write_call_async(const Address &p_target, const Address &p_base, const StringName &p_function_name, const Vector<Address> &p_arguments) = 0;
+	virtual void write_call_builtin(const Address &p_target, GDScriptFunctions::Function p_function, const Vector<Address> &p_arguments) = 0;
+	virtual void write_call_method_bind(const Address &p_target, const Address &p_base, const MethodBind *p_method, const Vector<Address> &p_arguments) = 0;
+	virtual void write_call_ptrcall(const Address &p_target, const Address &p_base, const MethodBind *p_method, const Vector<Address> &p_arguments) = 0;
+	virtual void write_call_self(const Address &p_target, const StringName &p_function_name, const Vector<Address> &p_arguments) = 0;
+	virtual void write_call_script_function(const Address &p_target, const Address &p_base, const StringName &p_function_name, const Vector<Address> &p_arguments) = 0;
+	virtual void write_construct(const Address &p_target, Variant::Type p_type, const Vector<Address> &p_arguments) = 0;
+	virtual void write_construct_array(const Address &p_target, const Vector<Address> &p_arguments) = 0;
+	virtual void write_construct_dictionary(const Address &p_target, const Vector<Address> &p_arguments) = 0;
+	virtual void write_await(const Address &p_target, const Address &p_operand) = 0;
+	virtual void write_if(const Address &p_condition) = 0;
+	// virtual void write_elseif(const Address &p_condition) = 0; This kind of makes things more difficult for no real benefit.
+	virtual void write_else() = 0;
+	virtual void write_endif() = 0;
+	virtual void write_for(const Address &p_variable, const Address &p_list) = 0;
+	virtual void write_endfor() = 0;
+	virtual void start_while_condition() = 0; // Used to allow a jump to the expression evaluation.
+	virtual void write_while(const Address &p_condition) = 0;
+	virtual void write_endwhile() = 0;
+	virtual void start_match() = 0;
+	virtual void start_match_branch() = 0;
+	virtual void end_match() = 0;
+	virtual void write_break() = 0;
+	virtual void write_continue() = 0;
+	virtual void write_continue_match() = 0;
+	virtual void write_breakpoint() = 0;
+	virtual void write_newline(int p_line) = 0;
+	virtual void write_return(const Address &p_return_value) = 0;
+	virtual void write_assert(const Address &p_test, const Address &p_message) = 0;
+
+	virtual ~GDScriptCodeGenerator() {}
+};
+
+#endif // GDSCRIPT_CODEGEN
diff --git a/modules/gdscript/gdscript_function.h b/modules/gdscript/gdscript_function.h
index 771baf6a085..187d4207017 100644
--- a/modules/gdscript/gdscript_function.h
+++ b/modules/gdscript/gdscript_function.h
@@ -224,6 +224,7 @@ public:
 
 private:
 	friend class GDScriptCompiler;
+	friend class GDScriptByteCodeGenerator;
 
 	StringName source;