ITR: Compiler Technology for Automatic Parallelization via Thread-Level Speculation

出于许多实际原因（例如，硬件开发成本，功耗等），如果我们可以通过简单地增加更多的处理器来提高计算机系统的有效性能，这将是很有吸引力的。虽然构建这种支持“并行处理”的系统相当简单，但相对而言，今天的程序很少会在这样的机器上获得任何性能提升，因为它们没有在编写时考虑到并行处理。利用并行处理的潜在好处而不给程序员带来很大负担的理想解决方案是编译器自动将顺序程序转换为高效的并行程序。虽然在使用编译器自动“并行化”常规数值程序（通常用FORTRAN编写）方面取得了进展，但在自动并行化更广泛的程序类方面进展甚微。关键的障碍是编译器传统上通过证明潜在的线程总是独立的来创建并行性。为了规避这个限制，最近的硬件建议使编译器能够乐观地创建并行线程，而无需证明独立性。在这个项目中，我们计划开发必要的编译器技术，以充分利用这种利用并行处理器的新潜力。

For many practical reasons (e.g., hardware development cost, powerconsumption, etc.), it would be attractive if we could increase theeffective performance of a computer system by simply adding more processorsto it. While it is reasonably straightforward to build such systems thatsupport "parallel processing", relatively few of today's programs wouldenjoy any performance gain on such machines because they were not writtenwith parallel processing in mind. The ideal solution for harnessing thepotential benefits of parallel processing without placing a large burden onthe programmer would be for the compiler to automatically transform asequential program into an efficient parallel program. While there hasbeen progress on using compilers to automatically "parallelize" regularnumeric programs (typically written in FORTRAN), there has been littleprogress in automatically parallelizing broader classes of programs. Thekey stumbling block has been that compilers have traditionally createdparallelism by proving that potential threads are always independent. Tocircumvent this limitation, recent hardware prooposals enable the compilerto optimistically create parallel threads without proving independence. Inthis project, we plan to develop the compiler technology necessary to fullyexploit this new potential for harnessing parallel processors.