The technique called thread-level speculation (TLS) seeks to allow sequential code to be executed in parallel without prior analysis of compile-time dependence. This noteworthy survey paper includes the technique, a taxonomy of TLS approaches, and a summary of significant advances.

The brief introductory section serves as an effective overview of the paper and its organization, and the second section addresses sources of TLS and design options. In particular, the second section includes the role of loops, possible drawbacks of TLS, three primary types of TLS techniques, and an overview of design choices. Next comes a brief section on earlier approaches that were attempted. Sections 4 and 5 carefully consider proposed hardware and software implementations, respectively. The last three sections look at other settings for TLS, TLS limits (both practical and theoretical), and conclusions. There are twelve-and-a-half pages of references for this extensively researched survey!

This carefully prepared survey is a valuable resource for TLS researchers. It is written in an easy-to-read manner that is almost conversational while being quite appropriate to this context. Surprisingly, there is only one figure in the lengthy article, but that reflects the encyclopedic coverage of TLS and doesn’t really distract from the overall excellence of the survey.