Towards a Compiler Framework for Thread-Level Speculation

Abstract

Speculative parallelization techniques allow to extract parallelism of fragments of code that can not be analyzed at compile time. However, research on software-based, thread-level speculation will greatly benefit from an appropriate compiler framework for easy prototyping and further development of new techniques. This paper presents an experimental XML-based compilation framework to handle speculative parallelization of C code. The framework extends Cetus, a source-to-source C compiler, to build an XML tree based on the Cetus Internal Representation of the source code. Other modules of our framework rely on XPath and XSLT capabilities to process the XML tree generated, to perform analysis on the use of variables and to augment the original code for software-based, speculative parallel execution. The use of the current version of our framework allows a fast prototyping of new analysis and transformation solutions, with a reduction of around 83% on the number of code lines needed with respect to the direct use of Cetus for the same purpose. To show the possibilities of this framework, we present an automatically-generated classification of loops for several SPEC CPU2006 C benchmarks. This classification is useful to better understand the potential benefits derived from the use of speculative parallelization techniques. The development framework presented here is freely available under request.