Non-volatile registers aware instruction selection for embedded systems

It is common that embedded systems are powered by limited and unstable power supply. In order to improve the reliability of embedded systems against unstable power supply, non-volatile memory (e.g. FRAM) based registers are proposed for embedded processors. FRAM-based registers have many advantages over traditional CMOS-based volatile registers such as non-volatility and power-economy. However, similar to other non-volatile memories (NVM), write operations to FRAM consume more time and power compared with read operations and limit the lifetime of the registers. Existing compiler optimization techniques never take the writes to registers into consideration. Therefore, code generated by a traditional compiler has an adverse effect on processors with non-volatile registers. This paper aims at improving the lifetime and efficiency of non-volatile registers based embedded processors by generating NV register friendly code. To achieve the goal, in this paper, we investigate the usage of memory access instructions and propose the NV Register Aware Instruction Selection (NAIS) algorithm to reduce the write operations on non-volatile registers. According to the experimental results, the proposed algorithm can reduce the writes on NV registers by 66.89% on average when compared with GCC [1]. Thus the lifetime of NV registers is extended to 2 times as long as before on average. The time cost is reduced by 56.68% and the energy consumption is reduced by 59.76% on average.