Method emit_exit_handler

src/vm_codegen.cpp:865–897

    }

    void VMCodeGen::emit_exit_handler(X64Emitter& e) {
        off_.exit_handler = e.size();
        const auto& cfg = vm_.dispatcher_regs();
        const auto& st  = vm_.state_layout();

        e.mov_reg_mem(
            rx::rsp,
            cfg.state_ptr,
            static_cast<std::int32_t>(st.saved_native_rsp),
            true
        );

        // return value: VM_AX into rax
        e.mov_reg_mem(
            rx::rax,
            cfg.state_ptr,
            static_cast<std::int32_t>(st.regs_base + vm_.slot_of_xreg(XReg::AX) * 8),
            true
        );

        const std::uint32_t frame_size = static_cast<std::uint32_t>(vm_.state_layout().total_size) + vm_.shadow_stack_bytes() + vm_.frame_padding();
        const std::uint32_t aligned = (frame_size + 15) & ~15u;
        e.add_reg_imm32(rx::rsp, static_cast<std::int32_t>(aligned));
        e.popfq();
        auto it = g_prologue_orders.find(&e);
        if (it == g_prologue_orders.end()) throw Error("emit_exit_handler: missing prologue order");

        for (auto rit = it->second.order.rbegin(); rit != it->second.order.rend(); ++rit) {
            e.pop_reg(*rit);
        }

        e.ret();
    }
}