Performance Optimization of Hyperblock Using Predicate Compilation Technique

Abstract

Predicate execution provides a large number of opportunities to enhance and expose ILP in the presence of branches. However, as with speculative execution, an aggressive compiler is required to realize most of the performance advantages. Compiler Optimization and transformation techniques focus on eliminating branches from the instruction stream and overlapping the execution of multiple control flow paths using the conditional execution capabilities provided by predication. The compiler support for predicated execution is based on a new structure referred to as the hyperblock. . Hyperblocks are a generalized form of Superblock that takes advantage of both predicated and speculative execution. This paper discusses the hyperblock compilation techniques. The formation procedure of hyperblock is described first. Secondly, the extensions to traditional optimization, instruction scheduling, and register allocation techniques to enable them to work on hyperblocks. The presence of predicates introduces new challenges into the compiler backend to understand the meaning of predicates, take the advantage of the relations among predicates, and perform transformations in the presence of predicates. Finally, a set of four new optimizations designed specially for improving the performance of predicated code.