Section: Overall Objectives

Summary of Compsys III Achievements

For Compsys III, the changes in the permanent members (departure of Fabrice Rastello and arrival of Laure Gonnord, while she was only external collaborator of Compsys until Sep. 2013) reduced the forces on back-end code optimizations, and in particular dynamic compilation, but increased (for a short period only) the forces on program analysis. In this context, Compsys III has continued to develop fundamental concepts or techniques whose applicability should go beyond a particular architectural or language trend, as well as stand-alone tools (either as proofs of concepts or to be used as basic blocks in larger tools/compilers developed by others) and our own experimental prototypes. One of the main objectives of Compsys III has been to try to push the polyhedral model beyond its present limits both in terms of analysis techniques (possibly integrating approximation and runtime support) and of applicability (e.g., analysis of parallel or streaming languages, program verification, compilation towards accelerators such as GPU or multicores). The hiring of Tomofumi Yuki supported this new direction. The achievements of Compsys III include work on:

• Back-end code analysis including fast scalar liveness analysis, register spilling analysis, pointer and array analysis.

• Polyhedral code analysis and optimizations, including communication analysis for kernel offloading to FPGA and GPU, analysis of while loops, analysis of parallel and streaming languages (liveness, memory folding, race detection), parametric tiling, polynomial extensions.

Compsys III was positively evaluated in Spring 2016 (with regrets with respect to its undesired stop) in Spring 2016. This evaluation also served as the final evaluation of Compsys after 12 years. The evaluation committee members were Krzystof Czarnecki (University of Waterloo), Benoît Dupont de Dinechin (Kalray), Nikil Dutt (UC Irvine), Walid Najjar (UC Riverside), Kristoffer Rose (Two Sigma Investments, NYW), Christian Schulte (KTH Royal Institute of Technology), Tulika Mitra (NUS), J. (Ram) Ramanujam (Lousiana State Univ.), Kathryn S. McKinley (chair, Microsoft), the last three being directly responsible for Compsys evaluation.

More details on the 2013, 2014, 2015 activities are given in the corresponding annual reports (see also the synthesis report provided for the 2016 evaluation). The new results for this year (2016) are given in Section 5.1 (highlights) and from Section 7.1 to 7.7 (new results).