• jarin@chromium.org's avatar
    The current · 99ce5a24
    jarin@chromium.org authored
    version is passing all the existing test + a bunch of new tests
    (packaged in the change list, too).
    
    The patch extends the SlotRef object to describe captured and duplicated
    objects. Since the SlotRefs are not independent of each other anymore,
    there is a new SlotRefValueBuilder class that stores the SlotRefs and
    later materializes the objects from the SlotRefs.
    
    Note that unlike the previous implementation of SlotRefs, we now build
    the SlotRef entries for the entire frame, not just the particular
    function.  This is because duplicate objects might refer to previous
    captured objects (that might live inside other inlined function's part
    of the frame).
    
    We also need to store the materialized objects between other potential
    invocations of the same arguments object so that we materialize each
    captured object at most once.  The materialized objects of frames live
    in the new MaterielizedObjectStore object (contained in Isolate),
    indexed by the frame's FP address.  Each argument materialization (and
    deoptimization) tries to lookup its captured objects in the store before
    building new ones.  Deoptimization also removes the materialized objects
    from the store. We also schedule a lazy deopt to be sure that we always
    get rid of the materialized objects and that the optmized function
    adopts the materialized objects (instead of happily computing with its
    captured representations).
    
    Concerns:
    
    - Is the FP address the right key for a frame? (Note that deoptimizer's
    representation of frame is different from the argument object
    materializer's one - it is not easy to find common ground.)
    
    - Performance is suboptimal in several places, but a quick local run of
    benchmarks does not seem to show a perf hit. Examples of possible
    improvements: smarter generation of SlotRefs (build other functions'
    SlotRefs only for captured objects and only if necessary), smarter
    lookup of stored materialized objects.
    
    - Ideally, we would like to share the code for argument materialization
    with deoptimizer's materializer.  However, the supporting data structures
    (mainly the frame descriptor) are quite different in each case, so it
    looks more like a separate project.
    
    Thanks for any feedback.
    
    R=danno@chromium.org, mstarzinger@chromium.org
    LOG=N
    BUG=
    
    Committed: https://code.google.com/p/v8/source/detail?r=18918
    
    Review URL: https://codereview.chromium.org/103243005
    
    git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@18936 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
    99ce5a24
escape-analysis-arguments.js 4.44 KB