refactor: remove ReturnValue instruction

furc/src/back/furvm.cpp

@@ -143,11 +143,7 @@ void furvm_generator::generate_instruction(furvm::mod& mod,
         generate_jump(mod, ctx, branch.else_block(), false);
     } break;
     case furlang::ir::instruction_t::Return: {
-        if (instr.sources().empty()) {
         mod.bytecode().push_back(static_cast<furvm::byte>(furvm::instruction_t::Return));
-        } else {
-            mod.bytecode().push_back(static_cast<furvm::byte>(furvm::instruction_t::ReturnValue));
-        }
     } break;
     case furlang::ir::instruction_t::Call: {
         const auto& call = dynamic_cast<const furlang::ir::call_instruction&>(instr);

furvm/include/furvm/instruction.hpp

@@ -170,11 +170,6 @@ enum class instruction_t : byte {
      * @brief Pops the current call frame.
      */
     Return,
-
-    /**
-     * @brief Pops the current call frame and pushes the first element from the previous stack onto the new stack.
-     */
-    ReturnValue,
 };
 
 struct instruction {

furvm/src/executor.cpp

@@ -297,11 +297,6 @@ void executor::step() {
         pop_frame();
         if (m_frames.empty()) m_flags = m_flags | executor_flags::Done;
     } break;
-    case instruction_t::ReturnValue: {
-        auto value = pop_thing();
-        pop_frame();
-        push_thing(std::move(value));
-    } break;
     case instruction_t::PushConstant: throw std::runtime_error("unimplemented");
     default: throw std::runtime_error("unknown instruction");
     }