diff options
Diffstat (limited to 'posix/sched_cpucount.c')
| -rw-r--r-- | posix/sched_cpucount.c | 40 |
1 files changed, 14 insertions, 26 deletions
diff --git a/posix/sched_cpucount.c b/posix/sched_cpucount.c index b0ca4ea..63d0e99 100644 --- a/posix/sched_cpucount.c +++ b/posix/sched_cpucount.c @@ -17,36 +17,24 @@ #include <sched.h> +/* Counting bits set, Brian Kernighan's way. + Using a open-coded routine is slight better for architectures that + do not have a popcount instruction (compiler might emit a library + call). */ +static inline int +countbits (__cpu_mask v) +{ + int s = 0; + for (; v != 0; s++) + v &= v - 1; + return s; +} int __sched_cpucount (size_t setsize, const cpu_set_t *setp) { int s = 0; - const __cpu_mask *p = setp->__bits; - const __cpu_mask *end = &setp->__bits[setsize / sizeof (__cpu_mask)]; - - while (p < end) - { - __cpu_mask l = *p++; - -#ifdef POPCNT - s += POPCNT (l); -#else - if (l == 0) - continue; - - _Static_assert (sizeof (l) == sizeof (unsigned int) - || sizeof (l) == sizeof (unsigned long) - || sizeof (l) == sizeof (unsigned long long), - "sizeof (__cpu_mask"); - if (sizeof (__cpu_mask) == sizeof (unsigned int)) - s += __builtin_popcount (l); - else if (sizeof (__cpu_mask) == sizeof (unsigned long)) - s += __builtin_popcountl (l); - else - s += __builtin_popcountll (l); -#endif - } - + for (int i = 0; i < setsize / sizeof (__cpu_mask); i++) + s += countbits (setp->__bits[i]); return s; } |