1. 13 Feb, 2018 1 commit
    • Benedikt Meurer's avatar
      [builtins] Optimize PromiseResolveThenableJob for the common case. · 1f8dcc5d
      Benedikt Meurer authored
      The idea here is that in case the `thenable` is a JSPromise and `then`
      is the initial `Promise.prototype.then` method, and the @@species lookup
      chain is intact, we can skip creating the temporary promise and the
      closures (with the shared context), and instead directly call into our
      PerformPromiseThen. This is sound since - given above mentioned
      conditions - our short-cut
      
        PerformPromiseThen(thenable, undefined, undefined, promise_to_resolve)
      
      is not observably different from the actual
      
        resolve, reject = CreateResolvingFunctions(promise_to_resolve)
        result_capability = NewPromiseCapability(%Promise%)
        PerformPromiseThen(thenable, resolve, reject, result_capability)
      
      except through PromiseHooks (and potentially via the async stack
      traces). So we disable the fast-path if either promise hooks are enabled
      or the debugger is active for now.
      
      This improves the performance on the wikipedia benchmark by 20-25% and
      the bluebird-doxbee benchmark by around 20%.
      
      Bug: v8:7253
      Change-Id: I23c92ad365c2b71d65057573f2d8febe2afe00b0
      Reviewed-on: https://chromium-review.googlesource.com/911800
      Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
      Reviewed-by: 's avatarSathya Gunasekaran <gsathya@chromium.org>
      Cr-Commit-Position: refs/heads/master@{#51261}
      1f8dcc5d