posix/sched_cpucount.c

   1 /* Copyright (C) 2007-2017 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <http://www.gnu.org/licenses/>.  */
  17
  18 #include <limits.h>
  19 #include <sched.h>
  20
  21
  22 int
  23 __sched_cpucount (size_t setsize, const cpu_set_t *setp)
  24 {
  25   int s = 0;
  26   const __cpu_mask *p = setp->__bits;
  27   const __cpu_mask *end = &setp->__bits[setsize / sizeof (__cpu_mask)];
  28
  29   while (p < end)
  30     {
  31       __cpu_mask l = *p++;
  32
  33 #ifdef POPCNT
  34       s += POPCNT (l);
  35 #else
  36       if (l == 0)
  37         continue;
  38
  39 # if LONG_BIT > 32
  40       l = (l & 0x5555555555555555ul) + ((l >> 1) & 0x5555555555555555ul);
  41       l = (l & 0x3333333333333333ul) + ((l >> 2) & 0x3333333333333333ul);
  42       l = (l & 0x0f0f0f0f0f0f0f0ful) + ((l >> 4) & 0x0f0f0f0f0f0f0f0ful);
  43       l = (l & 0x00ff00ff00ff00fful) + ((l >> 8) & 0x00ff00ff00ff00fful);
  44       l = (l & 0x0000ffff0000fffful) + ((l >> 16) & 0x0000ffff0000fffful);
  45       l = (l & 0x00000000fffffffful) + ((l >> 32) & 0x00000000fffffffful);
  46 # else
  47       l = (l & 0x55555555ul) + ((l >> 1) & 0x55555555ul);
  48       l = (l & 0x33333333ul) + ((l >> 2) & 0x33333333ul);
  49       l = (l & 0x0f0f0f0ful) + ((l >> 4) & 0x0f0f0f0ful);
  50       l = (l & 0x00ff00fful) + ((l >> 8) & 0x00ff00fful);
  51       l = (l & 0x0000fffful) + ((l >> 16) & 0x0000fffful);
  52 # endif
  53
  54       s += l;
  55 #endif
  56     }
  57
  58   return s;
  59 }