Ensure Java Precise Exception Instruction Scheduling

Currently, as a general-purpose programming language, Java has played a more and more important role in many computer application realms. However, the relatively low performance of Java has become a very severe obstacle for its further development. One of the main reason for this problem results from the conflicts between Java precise exception model and instruction scheduling. Java precise exception model involves extremely strict precise-exception-related dependencies. In order to satisfy Java precise exception model and not to break the involved dependencies, many existing instruction scheduling algorithms are severely restricted or disabled in Java compilation due to the frequent exception checks in programs. With the low effectiveness of instruction scheduling, the instruction-level parallelism of programs is substantially reduced, thus causing the low efficiency of program execution.In order to solve the problem, we propose a new method for effective instruction scheduling with the support of Java precise exception model. The proposed method allows compilers to completely ignoring precise-exception-related dependencies when reordering instructions so as to maximize the effectiveness of instruction scheduling. Meanwhile, certain mechanism is adopted to assure the obedience of Java precise exception model when exceptions are thrown during the execution of programs. The proposed method is applicable for most exception checks and most instruction scheduling algorithms. The experiment results show an average speedup of more than 50% for the selected benchmarks, thus proving the feasibility and the high effectiveness of our method.