libbb: add bit counting function, use where appropriate

Although "naive" counting function is not too slow and is smaller,
using it on e.g. each of 1024 words of CPU mask feels wrong.

function                                             old     new   delta
bb_popcnt_32                                           -      52     +52
get_prefix                                           323     321      -2
nproc_main                                           206     199      -7
d4_run_script                                        739     731      -8
ipcalc_main                                          533     507     -26
------------------------------------------------------------------------------
(add/remove: 2/0 grow/shrink: 0/4 up/down: 52/-43)              Total: 9 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/include/libbb.h b/include/libbb.h
index 67d29f843..6914b5882 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -397,6 +397,13 @@ extern int *BB_GLOBAL_CONST bb_errno;
 uint64_t bb_bswap_64(uint64_t x) FAST_FUNC;
 #endif
 
+unsigned FAST_FUNC bb_popcnt_32(uint32_t m);
+#if ULONG_MAX > 0xffffffff
+unsigned FAST_FUNC bb_popcnt_long(unsigned_long m);
+#else
+#define bb_popcnt_long(m) bb_popcnt_32(m)
+#endif
+
 unsigned long FAST_FUNC isqrt(unsigned long long N);
 
 unsigned long long monotonic_ns(void) FAST_FUNC;