An LLVM Compiler for CAL

Sammanfattning: Massively parallel architectures are gaining momentum thanks to the opportunities for both high performance and low-power consumption. After being a matter for experiments in academia, manycores are now in production and industries with products that rely on high performance, for example, in the field of telecom and radar, are in the process of adopting them. In order to encourage adoption, there is a need for compiler technologies that can make appropriate use of the opportunities of these architectures. Programming languages with constructs that the compiler can easily identify as parallel are a reasonable starting point for these technologies. For example, in CAL (Caltrop Actor Language) [1], a program is organized as a network of actors and these actors can be executed in parallel. As a first approach, if there were enough processors for all actors in the network, each actor could be mapped on to one processor. Writing a compiler is a comprehensive software engineering project and there are a number of tools, data structures and algorithms that have to be chosen and that facilitate the task. Some tools are lexer and parser generators, some data structures are abstract syntax trees and intermediate representations for code generation, some of the algorithms are for analyzing properties of the program and for translating between different data structures. LLVM (Low Level Virtual Machine) [7] is a compiler infrastructure that offers a well defined language and target independent intermediate representation for programs. LLVM also provides compile-time, link-time and run-time optimization. This report discusses the front end of a compiler for CAL, including generation of code to LLVM. The work described in this report translates CAL programs into LLVM's intermediate representation and includes a runtime system that handles intercommunication links between actors and actor scheduling. This is an intermediate step in generating LLVM code for parallel architectures. With this compiler, application developers that need to evaluate different parallel platforms will be able to have their applications written in CAL and only the back-end, form LLVM to the platform, will need to be re-programmed.