bitmap: introduce bitmap_count_one()

Count how many bits set in the bitmap.

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>

include/qemu/bitmap.h

@@ -82,6 +82,7 @@ int slow_bitmap_andnot(unsigned long *dst, const unsigned long *bitmap1,
                        const unsigned long *bitmap2, long bits);
 int slow_bitmap_intersects(const unsigned long *bitmap1,
                            const unsigned long *bitmap2, long bits);
+long slow_bitmap_count_one(const unsigned long *bitmap, long nbits);
 
 static inline unsigned long *bitmap_try_new(long nbits)
 {
@@ -216,6 +217,15 @@ static inline int bitmap_intersects(const unsigned long *src1,
     }
 }
 
+static inline long bitmap_count_one(const unsigned long *bitmap, long nbits)
+{
+    if (small_nbits(nbits)) {
+        return ctpopl(*bitmap & BITMAP_LAST_WORD_MASK(nbits));
+    } else {
+        return slow_bitmap_count_one(bitmap, nbits);
+    }
+}
+
 void bitmap_set(unsigned long *map, long i, long len);
 void bitmap_set_atomic(unsigned long *map, long i, long len);
 void bitmap_clear(unsigned long *map, long start, long nr);