Register allocation for embedded systems to simultaneously reduce energy and temperature on registers

Energy and thermal issues are two important concerns for embedded system design. Diminished energy dissipation leads to a longer battery life, while reduced temperature hotspots decelerate the physical failure mechanisms. The instruction fetch logic associated with register access has a significant contribution towards the total energy consumption. Meanwhile, the register file has also been previously shown to exhibit the highest temperature compared to the rest of the components in an embedded processor. Therefore, the optimization of energy and the resolution of the thermal issue for register accesses are of great significance. In this article, register allocation techniques are studied to simultaneously reduce energy consumption and heat buildup on register accesses for embedded systems. Contrary to prevailing intuition, we observe that optimizing energy and optimizing temperature on register accesses conflict with each other. We introduce a rotator hardware in the instruction decoder to facilitate a balanced solution for the two conflicting objectives. Algorithms for register allocation and refinement are proposed based on the access patterns and the effects of the rotator. Experimental results show that the proposed algorithms obtain notable improvements of energy and peak temperature for embedded applications.