Impact of Register Reservation on the Reliability of Arm Cortex-M Processors under Neutrons

This paper investigates the impact of register reservation techniques on the radiation resilience of Arm Cortex-M7 microprocessors. Using a $32 \times 32$ matrix multiplication workload, we evaluate performance and reliability across several compilation configurations, focusing on standard compilation and versions reserving up to 7 general-purpose registers. Neutron irradiation experiments were conducted at the GENESIS facility to assess fault behavior under realistic space conditions. Additionally, a full instruction-level trace analysis was performed to understand the implications of register reservation. Results show that while reserving a few registers introduces modest execution overhead, it significantly shifts the fault outcome profile without initially degrading overall reliability. However, excessive reservation leads to noticeable reliability degradation. These findings provide insight into the interplay between compiler constraints and system robustness, establishing a foundation for future software-level hardening strategies.