• Leszek Swirski's avatar
    [maglev] Remove diff encoding of checkpoints · 7b3ede33
    Leszek Swirski authored
    Remove StoreToFrame and the general diff encoding for checkpoints, and
    instead make all Checkpoints immediately copy the live part of the
    interpreter frame state.
    
    This means that we don't need to recreate the frame state during graph
    processing, and we don't have to copy the checkpoint's state for storing
    in the deferred DeoptimizationInfo.
    
    In theory the diff encoding was meant to save zone memory for unused
    checkpoints, and for checkpoints that don't differ much from each other.
    However,
    
      a) We expect to do most checkpoint elimination during graph building,
         so the assumption that many checkpoints will be unused seems less
         probable, and
    
      b) We need to copy the checkpoint's frame state for emitting deopts,
         so we don't actually end up avoiding doing the copies.
    
    So, we can simplify things by removing this complexity.
    
    Bug: v8:7700
    Change-Id: Iff9743fabbf7a017cccf0ece76a797c571764ea6
    Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3545178Reviewed-by: 's avatarToon Verwaest <verwaest@chromium.org>
    Reviewed-by: 's avatarJakob Gruber <jgruber@chromium.org>
    Commit-Queue: Leszek Swirski <leszeks@chromium.org>
    Cr-Commit-Position: refs/heads/main@{#79602}
    7b3ede33
maglev-vreg-allocator.h 1.48 KB