1. 04 Mar, 2019 1 commit
  2. 29 Oct, 2018 1 commit
    • Benedikt Meurer's avatar
      [turbofan] Add support for huge DataViews. · 15c31fe4
      Benedikt Meurer authored
      This introduces Word64 support for the CheckBounds operator, which now
      lowers to either CheckedUint32Bounds or CheckedUint64Bounds after the
      representation selection. The right hand side of CheckBounds can now
      be any positive safe integer on 64-bit architectures, whereas it remains
      Unsigned31 for 32-bit architectures. We only use the extended Word64
      support when the right hand side is outside the Unsigned31 range, so
      for everything except DataViews this means that the performance should
      remain the same. The typing rule for the CheckBounds operator was
      updated to reflect this new behavior.
      
      The CheckBounds with a right hand side outside the Unsigned31 range will
      pass a new Signed64 feedback kind, which is handled with newly introduced
      CheckedFloat64ToInt64 and CheckedTaggedToInt64 operators in representation
      selection.
      
      The JSCallReducer lowering for DataView getType()/setType() methods was
      updated to not smi-check the [[ByteLength]] and [[ByteOffset]] anymore,
      but instead just use the raw uintptr_t values and operate on any value
      (for 64-bit architectures these fields can hold any positive safe
      integer, for 32-bit architectures it's limited to Unsigned31 range as
      before). This means that V8 can now handle huge DataViews fully, without
      falling off a performance cliff.
      
      This refactoring even gave us some performance improvements, on a simple
      micro-benchmark just exercising different DataView accesses we go from
      
        testDataViewGetUint8: 796 ms.
        testDataViewGetUint16: 997 ms.
        testDataViewGetInt32: 994 ms.
        testDataViewGetFloat64: 997 ms.
      
      to
      
        testDataViewGetUint8: 895 ms.
        testDataViewGetUint16: 889 ms.
        testDataViewGetInt32: 888 ms.
        testDataViewGetFloat64: 890 ms.
      
      meaning we lost around 10% on the single byte case, but gained 10% across
      the board for all the other element sizes.
      
      Design-Document: http://bit.ly/turbofan-word64
      Bug: chromium:225811, v8:4153, v8:7881, v8:8171, v8:8383
      Change-Id: Ic9d1bf152e47802c04dcfd679372e5c85e4abc83
      Reviewed-on: https://chromium-review.googlesource.com/c/1303732Reviewed-by: 's avatarSigurd Schneider <sigurds@chromium.org>
      Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
      Cr-Commit-Position: refs/heads/master@{#57095}
      15c31fe4
  3. 17 Sep, 2018 1 commit
    • Benedikt Meurer's avatar
      [turbofan] Initial support to compute NumberAdd/NumberSubtract in Word64. · 0c296cb2
      Benedikt Meurer authored
      This change introduces the necessary conversion operators to convert
      from Word64 to other representations (Tagged, Word32, Float64, etc.),
      and plugs in the Word64 representation for NumberAdd/NumberSubtract,
      such that TurboFan will go to Int64Add/Sub on 64-bit architectures
      when the inputs and the output of the operation is in safe integer
      range. This includes the necessary changes to the Deoptimizer to be
      able to rematerialize Int64 values as Smi/HeapNumber when going back
      to Ignition later.
      
      This change might affect performance, although measurements indicate
      that there should be no noticable performance impact.
      
      The goal is to have TurboFan support Word64 representation to a degree
      that changing the TypedArray length to an uint64_t (for 64-bit archs)
      becomes viable and doesn't have any negative performance implications.
      Independent of that we might get performance improvements in other areas
      such as for crypto code later.
      
      Bug: v8:4153, v8:7881, v8:8171, v8:8178
      Design-Document: bit.ly/turbofan-word64
      Change-Id: I29d56e2a31c1bae61d04a89d29ea73f21fd49c59
      Cq-Include-Trybots: luci.chromium.try:linux_chromium_headless_rel
      Reviewed-on: https://chromium-review.googlesource.com/1225709
      Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
      Reviewed-by: 's avatarJaroslav Sevcik <jarin@chromium.org>
      Cr-Commit-Position: refs/heads/master@{#55937}
      0c296cb2