Use __builtin_popcount in __sched_cpucount [BZ #21696]

posix/sched_cpucount.c assumes that size of __cpu_mask == size of long,
which is incorrect for x32.  This patch uses __builtin_popcount, which
is availabe in GCC 4.9, in posix/sched_cpucount.c.

Tested on i686, x86-64 and x32 with multi-arch disabled.

	[BZ #21696]
	* posix/sched_cpucount.c: Don't include <limits.h>.
	(__sched_cpucount): Use __builtin_popcount.

diff --git a/ChangeLog b/ChangeLog
index 58ce877..4cd5d31 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2017-07-01  Florian Weimer  <fweimer@redhat.com>
+           H.J. Lu  <hongjiu.lu@intel.com>
+
+       [BZ #21696]
+       * posix/sched_cpucount.c: Don't include <limits.h>.
+       (__sched_cpucount): Use __builtin_popcount.
+
 2017-07-01  Ramana Radhakrishnan  <ramana.gcc@googlemail.com>
 
        * sysdeps/unix/sysv/aarch64/cpu-features.c (init_cpu_features):

diff --git a/posix/sched_cpucount.c b/posix/sched_cpucount.c
index eaddf61..ab1ff49 100644 (file)
--- a/posix/sched_cpucount.c
+++ b/posix/sched_cpucount.c
@@ -15,7 +15,6 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
-#include <limits.h>
 #include <sched.h>
 
 
@@ -36,22 +35,16 @@ __sched_cpucount (size_t setsize, const cpu_set_t *setp)
       if (l == 0)
        continue;
 
-# if LONG_BIT > 32
-      l = (l & 0x5555555555555555ul) + ((l >> 1) & 0x5555555555555555ul);
-      l = (l & 0x3333333333333333ul) + ((l >> 2) & 0x3333333333333333ul);
-      l = (l & 0x0f0f0f0f0f0f0f0ful) + ((l >> 4) & 0x0f0f0f0f0f0f0f0ful);
-      l = (l & 0x00ff00ff00ff00fful) + ((l >> 8) & 0x00ff00ff00ff00fful);
-      l = (l & 0x0000ffff0000fffful) + ((l >> 16) & 0x0000ffff0000fffful);
-      l = (l & 0x00000000fffffffful) + ((l >> 32) & 0x00000000fffffffful);
-# else
-      l = (l & 0x55555555ul) + ((l >> 1) & 0x55555555ul);
-      l = (l & 0x33333333ul) + ((l >> 2) & 0x33333333ul);
-      l = (l & 0x0f0f0f0ful) + ((l >> 4) & 0x0f0f0f0ful);
-      l = (l & 0x00ff00fful) + ((l >> 8) & 0x00ff00fful);
-      l = (l & 0x0000fffful) + ((l >> 16) & 0x0000fffful);
-# endif
-
-      s += l;
+      _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
     }