ceph/src/dpdk/lib/librte_eal/common/include/rte_branch_prediction.h

   1 /*-
   2  *   BSD LICENSE
   3  *
   4  *   Copyright(c) 2010-2014 Intel Corporation. All rights reserved.
   5  *   All rights reserved.
   6  *
   7  *   Redistribution and use in source and binary forms, with or without
   8  *   modification, are permitted provided that the following conditions
   9  *   are met:
  10  *
  11  *     * Redistributions of source code must retain the above copyright
  12  *       notice, this list of conditions and the following disclaimer.
  13  *     * Redistributions in binary form must reproduce the above copyright
  14  *       notice, this list of conditions and the following disclaimer in
  15  *       the documentation and/or other materials provided with the
  16  *       distribution.
  17  *     * Neither the name of Intel Corporation nor the names of its
  18  *       contributors may be used to endorse or promote products derived
  19  *       from this software without specific prior written permission.
  20  *
  21  *   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  22  *   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  23  *   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  24  *   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  25  *   OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  26  *   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  27  *   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  28  *   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  29  *   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  30  *   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  31  *   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  32  */
  33
  34 /**
  35  * @file
  36  * Branch Prediction Helpers in RTE
  37  */
  38
  39 #ifndef _RTE_BRANCH_PREDICTION_H_
  40 #define _RTE_BRANCH_PREDICTION_H_
  41
  42 /**
  43  * Check if a branch is likely to be taken.
  44  *
  45  * This compiler builtin allows the developer to indicate if a branch is
  46  * likely to be taken. Example:
  47  *
  48  *   if (likely(x > 1))
  49  *      do_stuff();
  50  *
  51  */
  52 #ifndef likely
  53 #define likely(x)  __builtin_expect((x),1)
  54 #endif /* likely */
  55
  56 /**
  57  * Check if a branch is unlikely to be taken.
  58  *
  59  * This compiler builtin allows the developer to indicate if a branch is
  60  * unlikely to be taken. Example:
  61  *
  62  *   if (unlikely(x < 1))
  63  *      do_stuff();
  64  *
  65  */
  66 #ifndef unlikely
  67 #define unlikely(x)  __builtin_expect((x),0)
  68 #endif /* unlikely */
  69
  70 #endif /* _RTE_BRANCH_PREDICTION_H_ */