An SLP Vectorization Method Based on Equivalent Extended Transformation

Abstract

SIMD extensions provide an efficient energy consumption platform to support mobile systems. How to use SIMD instructions to improve program performance is a challenge. SLP (superword level parallelism) is an efficient solution to exploit the parallelism, oriented to SIMD, between statements in the basic blocks, and it has been widely used in almost all the mainstream compilers. SLP relies on finding isomorphic statements to pack together into vectors. However, the capability of autovectorization for nonisomorphic statements is insufficient. In this paper, we introduce SLP-E, a novel autovectorization method that can automatically vectorize the codes which contain nonisomorphic statements, translate the nonisomorphic statements into the isomorphic statements by equivalent extended transformation of expressions, and vectorize the isomorphic statements. SLP-E improves the application scope and benefits of SLP. We implement the SLP-E in LLVM and compare it with prior approaches. A set of applications that benefit from autovectorization are taken from the SPEC CPU 2017 benchmark to compare our approach and prior techniques. Experimental results show that SLP-E achieves more than 43.9% speedup, on average, over other similar methods.