The Tor Browser: js/src/builtin/ParallelUtilities.js@6474c204b198

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

     1 /* This Source Code Form is subject to the terms of the Mozilla Public

     2  * License, v. 2.0. If a copy of the MPL was not distributed with this

     3  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

     5 // Shared utility functions for and macros parallel operations in `Array.js`

     6 // and `TypedObject.js`.

     8 #ifdef ENABLE_PARALLEL_JS

    10 /* The mode asserts options object. */

    11 #define TRY_PARALLEL(MODE) \

    12   ((!MODE || MODE.mode !== "seq"))

    13 #define ASSERT_SEQUENTIAL_IS_OK(MODE) \

    14   do { if (MODE) AssertSequentialIsOK(MODE) } while(false)

    16 /**

    17  * The ParallelSpew intrinsic is only defined in debug mode, so define a dummy

    18  * if debug is not on.

    19  */

    20 #ifndef DEBUG

    21 #define ParallelSpew(args)

    22 #endif

    24 #define MAX_SLICE_SHIFT 6

    25 #define MAX_SLICE_SIZE 64

    26 #define MAX_SLICES_PER_WORKER 8

    28 /**

    29  * Macros to help compute the start and end indices of slices based on id. Use

    30  * with the object returned by ComputeSliceInfo.

    31  */

    32 #define SLICE_START_INDEX(shift, id) \

    33     (id << shift)

    34 #define SLICE_END_INDEX(shift, start, length) \

    35     std_Math_min(start + (1 << shift), length)

    37 /**

    38  * ForkJoinGetSlice acts as identity when we are not in a parallel section, so

    39  * pass in the next sequential value when we are in sequential mode. The

    40  * reason for this odd API is because intrinsics *need* to be called during

    41  * ForkJoin's warmup to fill the TI info.

    42  */

    43 #define GET_SLICE(sliceStart, sliceEnd, id) \

    44     ((id = ForkJoinGetSlice((InParallelSection() ? -1 : sliceStart++) | 0)) < sliceEnd)

    46 /**

    47  * Determine the number and size of slices. The info object has the following

    48  * properties:

    49  *

    50  *  - shift: amount to shift by to compute indices

    51  *  - count: number of slices

    52  */

    53 function ComputeSlicesInfo(length) {

    54   var count = length >>> MAX_SLICE_SHIFT;

    55   var numWorkers = ForkJoinNumWorkers();

    56   if (count < numWorkers)

    57     count = numWorkers;

    58   else if (count >= numWorkers * MAX_SLICES_PER_WORKER)

    59     count = numWorkers * MAX_SLICES_PER_WORKER;

    61   // Round the slice size to be a power of 2.

    62   var shift = std_Math_max(std_Math_log2(length / count) | 0, 1);

    64   // Recompute count with the rounded size.

    65   count = length >>> shift;

    66   if (count << shift !== length)

    67     count += 1;

    69   return { shift: shift, count: count };

    70 }

    72 #endif // ENABLE_PARALLEL_JS

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