Code Positioning for VLIW Architectures

Abstract

Several studies have considered reducing instruction cache misses and branch penalty stall cycles by means of various forms of code placement. Most proposed approaches rearrange procedures or basic blocks in order to speed up execution on sequential architectures with branch prediction. Moreover, most works focus mainly on instruction cache performance and disregard execution cycles. To the best of our knowledge, no work has specifically addressed statically scheduled ILP machines like VLIWs, with control-transfer delay slots. We propose a new code positioning algorithm especially designed for VLIW-style architectures, which allows to trade off tighter schedule for program locality. Our measurements indicate that code positioning, as a result of tighter program schedule and removed unconditional jumps, can significantly reduce the number of execution cycles, by up to 21%, while improving program locality and instruction cache performance.