The Optimization of IF-conversion in Whole Function Vectorization

In order to get better performance, lots of optimization methods are used in code transformation. When migrating SPMD to multi-core platform, vectorization is one key optimization to improve performance. Control flow is the main challenge for vectorization and IF-conversion is usually used to transform control flow into data flow. In most researches, after IF-conversion both the two branch vector codes have to be executed even the predications in scalar lane for one branch are all false. This study proposes code bypass technology to improve this situation in whole function vectorization of SSA from. The region of consecutive instructions guarded by the same predicate is first identified. Then detecting operation is added to identify if predications in scalar lane are all false and a jump operation followed to bypass the consecutive instructions region. For loop structure, we add loop mask to indicate which lane is not alive in loop which could help to treat iteration in loop. The experiment shows our method could improve performance by 6.8%.