Compiling and Optimizing Real-world Programs for STRAIGHT ISA

The renaming unit of a superscalar processor is a very expensive module. It consumes large amounts of power and limits the front-end bandwidth. To overcome this problem, an instruction set architecture called STRAIGHT has been proposed. Owing to its unique manner of referencing operands, STRAIGHT does not cause false dependencies and allows out-of-order execution without register renaming. However, the compiler optimization techniques for STRAIGHT are still immature, and we found that the naive code generators currently available can generate inefficient code with additional instructions. In this paper, we propose two novel compiler optimization techniques and a novel calling convention for STRAIGHT to reduce the number of instructions. We compiled real-world programs with a compiler that implemented these techniques and measured their performance through simulation. The evaluation results show that the proposed methods reduced the number of executed instructions by 15% and improved the performance by 17%.