From sequences of dependent instructions to functions: An approach for improving performance without ILP or speculation

In this article, we present an approach for improv-ing the performance of sequences of dependent instruc-tions. We observe that many sequences of instructions can be interpreted as functions. Unlike sequences of in-structions, functions can be translated into very fast but exponentially costly two-level combinational circuits. We present an approach that exploits this principle, speeds up programs thanks to circuit-level parallelism/redundancy, but avoids the exponential costs. We analyze the potential of this approach, and then we propose an implementation that consists of a super-scalar processor with a large specic functional unit as-sociated with specic back-end transformations. The per-formance of the SpecInt2000 benchmarks and selected programs from the Olden and MiBench benchmark suites improves on average from 2.4 % to 12 % depending on the latency of the functional units, and up to 39.6%; more precisely, the performance of optimized code sections im-proves on average from 3.5 % to 19%, and up to 49%. 1