• Jaroslav Sevcik's avatar
    Map update for integrity level transitions. · 06ba822e
    Jaroslav Sevcik authored
    This adds support for integrity level transitions (preventExtensions,
    seal and freeze) to MapUpdater and Map::TryUpdate.
    
    In both cases, we first try to detect whether there were integrity
    level transitions in the transition tree to the old map and make note
    of the most restrictive integrity transition and the map just before
    the transition (integrity-source-map). Then we find an appropriate root
    (based on integrity-source-map's elements kind) and replay the
    transitions based on the integrity-source-map's descriptor
    array. Finally, if we saw an integrity level transition in
    the beginning, we will find-or-create that transition (on the
    updated version of integrity-source-map).
    
    For the following micro-benchmark, we get about 10x speedup.
    
    ```
    function C() {
      this.x = 1;
      Object.seal(this);
      this.x = 0.1;
    }
    
    const start = Date.now();
    for (let i = 0; i < 1e7; i++) {
      new C();
    }
    console.log("Reconfigure sealed: " + (Date.now() - start));
    ```
    
    Before:
    > Reconfigure sealed: 5202
    
    After:
    > Reconfigure sealed: 479
    
    Bug: v8:8538
    Change-Id: If695be7469d8b6ccd44ac4528be8aa34b65b3e4d
    Reviewed-on: https://chromium-review.googlesource.com/c/1442640
    Commit-Queue: Jaroslav Sevcik <jarin@chromium.org>
    Reviewed-by: 's avatarIgor Sheludko <ishell@chromium.org>
    Cr-Commit-Position: refs/heads/master@{#59295}
    06ba822e
integrity-level-map-update.js 3.19 KB