Programming Research Group

New Member: Sherif Omar as an Exchange Student

Sherif Omar joined our group as an exchange student from Technische Universität Berlin. He will work with us until March. Herzlich willkommen!

New Member: Fathul Asrar Alfansuri

Fathul Asrar Alfansuri joined our group as a new master’s course student under IGP(A). He is the second Indonesian member in the group.  Selamat datang!

New Visiting Member: Paul Leger

Professor Paul Leger at Universidad Católica del Norte, Chile joined our group as a visiting scholar. He will jointly work with us until January 2020.

Paper on Compilation of Functional Languages at ICFP 2019

Youyou Cong will present the following paper at ICFP 2019.

 

Title: Compiling with Continuations, or without? Whatever.

Authors: Youyou Cong, Leo Osvald, Gregory Essertel, and Tiark Rompf

Abstract:

What makes a good compiler IR?  In the context of functional languages, there has been an extensive debate on the advantages and disadvantages of continuation-passing-style (CPS).  The consensus seems to be that some form of explicit continuations is necessary to model jumps in a functional style, but that they should have a 2nd-class status, separate from regular functions, to ensure efficient code generation.  Building on this observation, a recent study from PLDI 2017 proposed a direct-style IR with explicit join points, which essentially represent local continuations, i.e., functions that do not return or escape.  While this IR can work well in practice, as evidenced by the implementation of join points in the Glasgow Haskell Compiler (GHC), there still seems to be room for improvement, especially with regard to the way continuations are handled in the course of optimization.

In this paper, we contribute to the CPS debate by developing a novel IR with the following features.   First, we integrate a control operator that resembles Felleisen’s C, eliminating certain redundant rewrites observed in the previous study.  Second, we treat the non-returning and non-escaping aspects of continuations separately, allowing efficient compilation of well-behaved functions defined by the user.  Third, we define a selective CPS translation of our IR, which erases control operators while preserving the meaning and typing of programs.  These features enable optimizations in both direct style and full CPS, as well as in any intermediate style with selectively exposed continuations.  Thus, we change the spectrum of available options from “CPS yes or no” to “as much or as little CPS as you want, when you want it”.

Final Presentation for Tokyo Tech Summer Program by Chengkai Yang

Chengkai Yang, an exchange student from Georgia Tech, gave the final presentation on his working during the Tokyo Tech Summer Program.  He worked on KaniCUDA, a program synthesis-based optimization tool for CUDA programs, especially on accelerating the synthesizer speed.

• Poster for the final presentation