Trace-based just-in-time type specialization for dynamic languages

  • Authors:

  • Andreas Gal;Brendan Eich;Mike Shaver;David Anderson;David Mandelin;Mohammad R. Haghighat;Blake Kaplan;Graydon Hoare;Boris Zbarsky;Jason Orendorff;Jesse Ruderman;Edwin W. Smith;Rick Reitmaier;Michael Bebenita;Mason Chang;Michael Franz

  • Affiliations:

  • Mozilla Corporation, Mountain View, CA, USA;Mozilla Corporation, Mountain View, CA, USA;Mozilla Corporation, Mountain View, CA, USA;Mozilla Corporation, Mountain View, CA, USA;Mozilla Corporation, Mountain View, CA, USA;Intel Corporation, Santa Clara, CA, USA;Mozilla Corporation, Mountain View, CA, USA;Mozilla Corporation, Mountain View, CA, USA;Mozilla Corporation, Mountain View, CA, USA;Mozilla Corporation, Mountain View, CA, USA;Mozilla Corporation, Mountain View, CA, USA;Adobe Corportation, San Jose, CA, USA;Adobe Corporation, San Jose, CA, USA;University of California, Irvine, Irvine, CA, USA;University of California, Irvine, Irvine, CA, USA;University of California, Irvine, Irvine, CA, USA

  • Venue:
  • Proceedings of the 2009 ACM SIGPLAN conference on Programming language design and implementation
  • Year:
  • 2009

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Abstract

Dynamic languages such as JavaScript are more difficult to compile than statically typed ones. Since no concrete type information is available, traditional compilers need to emit generic code that can handle all possible type combinations at runtime. We present an alternative compilation technique for dynamically-typed languages that identifies frequently executed loop traces at run-time and then generates machine code on the fly that is specialized for the actual dynamic types occurring on each path through the loop. Our method provides cheap inter-procedural type specialization, and an elegant and efficient way of incrementally compiling lazily discovered alternative paths through nested loops. We have implemented a dynamic compiler for JavaScript based on our technique and we have measured speedups of 10x and more for certain benchmark programs.