• Jakob Gruber's avatar
    [nci] Share smi feedback and enable related optimizations · 3599cce1
    Jakob Gruber authored
    This CL enables a first batch of feedback-based optimizations in NCI
    code. Specifically, optimizations based on unary, binary, compare,
    for-in-next, and for-in-prepare feedback are now enabled.
    
    This has two main implications:
    
    1. NCI code can now deopt. Deoptimized code is currently thrown away
    permanently and cannot be reused. Now that shared/cached NCI code can
    deopt, this leads to an interesting question of what should happen
    with deoptimized NCI code. The answer in this CL is to remove the
    cache entry (it may later be re-added).
    
    2. Tiering up from NCI to TF still requires feedback; since NCI code,
    starting with this CL, no longer collects full feedback, feedback must
    be created in some other way. This is solved by sharing a
    context-independent encoding of feedback across native contexts.
    
    Feedback is shared through a new SerializedFeedback object type,
    essentially a byte array of serialized feedback. Currently, only
    smi-based feedback is shared, but map-based feedback will be added in
    the future.
    
    SerializedFeedback is kept in the NCI cache alongside NCI Code
    objects.  It is created on NCI cache insertion, and deserialized upon
    NCI cache hits.
    
    Bug: v8:8888
    Change-Id: Ic0d5fbea3aa4d3b0a165624dab9d0283b07dcee7
    Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2531775Reviewed-by: 's avatarUlan Degenbaev <ulan@chromium.org>
    Reviewed-by: 's avatarMythri Alle <mythria@chromium.org>
    Reviewed-by: 's avatarToon Verwaest <verwaest@chromium.org>
    Commit-Queue: Jakob Gruber <jgruber@chromium.org>
    Cr-Commit-Position: refs/heads/master@{#71224}
    3599cce1
serialized-feedback-inl.h 734 Bytes