Extending old languages for new architectures

Architectures evolve quickly. The number of transistors available to chip designers doubles every 18 months, allowing increasingly complex architectures to be developed on a single chip. Power dissipation issues have forced chip designers to look for new ways to use the transistors at their disposal. This situation inevitably leads to new architectural features on a fairly regular basis. Enabling programmers to benefit from these new architectural features can be problematic. Since architectures change frequently, and compilers last for a long time, it is clear that compilers should be designed to be extensible. This thesis argues that to support evolving architectures a compiler should support the creation of high-level language extensions. In particular, it must support extending the compiler's middle-end. We describe the design of EMCC, a C compiler that allows extension of its front-, middle- and back-ends. OpenMP is an extension to the C programming language to support parallelism. It has recently added support for task-based parallelism, a dynamic form of parallelism made popular by Cilk. However, implementing task-based parallelism efficiently requires much more involved program transformation than the simple static parallelism originally supported by OpenMP. We use EMCC to create an implementation of OpenMP, with particular focus on efficient implementation of task-based parallelism. We also demonstrate the benefits of supporting high-level analysis through an extended middle-end, by developing and implementing an interprocedural analysis that improves the performance of task-based parallelism by allowing tasks to share stacks. We develop a novel generalisation of logic programming that we use to concisely express this analysis, and use this formalism to demonstrate that the analysis can be executed in polynomial time. Finally, we design extensions to OpenMP to support heterogeneous architectures