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  24. 03 Nov, 2017 1 commit
    • Benedikt Meurer's avatar
      [turbofan] Generalized OOB support for KeyedLoadIC. · b7168573
      Benedikt Meurer authored
      This extends the support in TurboFan and the ICs for OOB loads to also
      apply to typed arrays and receivers whose prototype chain is protected
      by the "no elements" protector (aka the Array protector). TurboFan will
      generate code to materialize undefined instead when it sees a load that
      has the OOB bit set and add an appropriate code dependency on the global
      protector. For typed arrays it doesn't even need to check the global
      protector since elements are never looked up in the prototype chain
      for typed arrays.
      
      In the simple micro-benchmark from the bug we go from
      
        testInBounds: 103 ms.
        testOutOfBounds: 289 ms.
      
      to
      
        testInBounds: 103 ms.
        testOutOfBounds: 102 ms.
      
      which fixes the 3x slowdown and thus addresses the performance cliff. In
      general it's still beneficial to make sure that you don't access out of
      bounds, especially once we introduce a bounds check elimination pass to
      TurboFan.
      
      This also seems to improve the jQuery benchmark on the Speedometer test
      suite by like 1-2% on average. And the SixSpeed rest benchmarks go from
      
        rest-es5: 25 ms.
        rest-es6: 23 ms.
      
      to
      
        rest-es5: 6 ms.
        rest-es6: 4 ms.
      
      so a solid 5.7x improvement there.
      
      Bug: v8:6936, v8:7014, v8:7027
      Change-Id: Ie99699c69cc40057512e72fd40ae28107216c423
      Reviewed-on: https://chromium-review.googlesource.com/750089
      Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
      Reviewed-by: 's avatarBenedikt Meurer <bmeurer@chromium.org>
      Reviewed-by: 's avatarTobias Tebbi <tebbi@chromium.org>
      Cr-Commit-Position: refs/heads/master@{#49095}
      b7168573
  25. 31 Oct, 2017 1 commit
    • Benedikt Meurer's avatar
      [ic] Add OOB support to KeyedLoadIC. · 6dc35ab4
      Benedikt Meurer authored
      This adds support to the KeyedLoadIC to ignore out of bounds accesses
      for Strings and return undefined instead. We add a dedicated bit to the
      Smi handler to encode the OOB state and have TurboFan generate appropriate
      code for that case as well. This is mostly useful when programs
      accidentially access past the length of a string, which was observed and
      fixed for example in Babel recently, see
      
        https://github.com/babel/babel/pull/6589
      
      for details. The idea is to also extend this mechanism to Arrays and
      maybe other receivers, as reading beyond the length is also often used
      in jQuery and other popular libraries.
      
      Note that this is considered a mitigation for a performance cliff and
      not a general optimization of OOB accesses. These should still be
      avoided and handled properly instead.
      
      This seems to further improve the babel test on the web-tooling-benchmark
      by around 1%, because the OOB access no longer turns the otherwise
      MONOMORPHIC access into MEGAMORPHIC state.
      
      Bug: v8:6936, v8:7014
      Change-Id: I9df03304e056d7001a65da8e9621119f8e9bb55b
      Reviewed-on: https://chromium-review.googlesource.com/744022
      Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
      Reviewed-by: 's avatarCamillo Bruni <cbruni@chromium.org>
      Reviewed-by: 's avatarLeszek Swirski <leszeks@chromium.org>
      Reviewed-by: 's avatarBenedikt Meurer <bmeurer@chromium.org>
      Cr-Commit-Position: refs/heads/master@{#49049}
      6dc35ab4
  26. 30 Oct, 2017 1 commit
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  30. 01 Sep, 2017 3 commits