Characterizing diverse handheld apps for customized hardware acceleration

Current handhelds incorporate a variety of acceler-ators/IPs for improving their performance and energy efficiency. While these IPs are extremely useful for accelerating parts of a computation, the CPU still expends a significant amount of time and energy in the overall execution. Coarse grain customized hardware of Android APIs and methods, though widely useful, is also not an option due to the high hardware costs. Instead, we propose a fine-grain sequence of instructions, called a Load-to-Store (LOST) sequence, for hardware customization. A LOST sequence starts with a load and ends with a store, including dependent instructions in between. Unlike prior approaches to customization, a LOST sequence is defined based on a sequence of opcodes rather than a sequence of PC addresses or operands. We identify such commonly occurring LOST sequences within and across several popular apps and propose a design to integrate these customized hardware sequences as macro functional units into the CPU data-path. Detailed evaluation shows that such customized LOST sequences can provide an average of 25% CPU speedup, or 12% speedup for the entire system.