• Toon Verwaest's avatar
    Revert "Reland^3 "[runtime] Amortize descriptor array growing for fast-mode prototypes"" · 4911ab95
    Toon Verwaest authored
    This reverts commit 65630850.
    
    Reason for revert: due to failures
    
    Original change's description:
    > Reland^3 "[runtime] Amortize descriptor array growing for fast-mode prototypes"
    > 
    > This CL:
    >  - stops tracking transitions for fast maps that are known to be detached
    >  - reuses descriptor arrays when transitioning detached maps to avoid O(n^2) performance and garbage creation
    > 
    > Fix in reland: check whether the map of the back pointer is the metamap rather than reading the map of the constructor-or-backpointer slot. If the slot contains a constructor, it's possible that the object transitions while the concurrent marker is reading the map (from which it's reading the instance type); and it's possible that the transitioned map isn't set up yet fully when we read the instance type. An acquire load for the constructor-or-backpointer map would also fix it by serializing stores, but is more expensive. Checking the metamap is faster.
    > 
    > Original commit message:
    > > This avoids an O(n^2) algorithm that creates an equal amount of garbage.
    > > Even though the actual final descriptor array might be a little bigger,
    > > it reduces peak memory usage by allocating less.
    > 
    > TBR=ulan@chromium.org,ishell@chromium.org
    > 
    > Change-Id: I57000949debdee2b69dd41e0c5975b3e8a34c6f4
    > No-Presubmit: true
    > No-Tree-Checks: true
    > No-Try: true
    > Bug: b:148346655, v8:10339
    > Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2173363
    > Commit-Queue: Toon Verwaest <verwaest@chromium.org>
    > Reviewed-by: Toon Verwaest <verwaest@chromium.org>
    > Cr-Commit-Position: refs/heads/master@{#67499}
    
    TBR=ulan@chromium.org,clemensb@chromium.org,ishell@chromium.org,verwaest@chromium.org
    
    Change-Id: Ie7018912f591d397c8acede9b31fbf269d225fe4
    No-Presubmit: true
    No-Tree-Checks: true
    No-Try: true
    Bug: b:148346655, v8:10339
    Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2174299Reviewed-by: 's avatarToon Verwaest <verwaest@chromium.org>
    Commit-Queue: Toon Verwaest <verwaest@chromium.org>
    Cr-Commit-Position: refs/heads/master@{#67500}
    4911ab95
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