• bmeurer's avatar
    [compiler] Properly guard the speculative optimizations for instanceof. · a0484bc6
    bmeurer authored
    Add a general feedback slot for instanceof similar to what we already have
    for for-in, which basically has a fast (indicated by the uninitialized
    sentinel) and a slow (indicated by the megamorphic sentinel) mode. Now
    we can only take the fast path when the feedback slot says it hasn't
    seen any funky inputs and nothing funky appeared in the prototype chain.
    In the TurboFan code we also deoptimize whenever we see a funky object
    (i.e. a proxy or an object that requires access checks) in the prototype
    chain (similar to what Crankshaft already did).
    
    Drive-by-fix: Also make Crankshaft respect the mode and therefore
    address the deopt loop in Crankshaft around instanceof.
    
    We might want to introduce an InstanceOfIC mechanism at some point and
    track the map of the right-hand side.
    
    BUG=v8:5267
    R=mvstanton@chromium.org
    
    Review-Url: https://codereview.chromium.org/2370693002
    Cr-Commit-Position: refs/heads/master@{#39718}
    a0484bc6
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