Qualifying non-volatile register files for embedded systems through compiler-directed write minimization and balancing

Recent research shows non-volatile flip-flops can be attached to register files to hold computation state thus enabling fast recovery upon power failure. However, the endurance limitation of NVM cells challenges their usage for holding register values that are frequently updated during program execution. To extend the lifetime of non-volatile register files, we propose two compiler-directed optimizations. First, through analyzing the register access patterns in frequently executed loops, a minimum set of registers is identified to be periodically written to NVM cells, thus minimizing the total number of writes to the NVM register file. Meanwhile, the register mapping is also adjusted to enable an efficient dynamic register rotation to further balance the writes to different NVM registers. Experimental studies show that the proposed two techniques can significantly extend the lifetime of non-volatile registers, thus qualifying them for various embedded systems.