Replace bit shift with __builtin_ctzll in HyperLogLog

src/hyperloglog.c

@@ -429,7 +429,7 @@ uint64_t MurmurHash64A (const void * key, int len, unsigned int seed) {
  * of the pattern 000..1 of the element hash. As a side effect 'regp' is
  * set to the register index this element hashes to. */
 int hllPatLen(unsigned char *ele, size_t elesize, long *regp) {
- uint64_t hash, bit, index;
+ uint64_t hash, index;
  int count;
 
  /* Count the number of zeroes starting from bit HLL_REGISTERS
@@ -448,12 +448,10 @@ int hllPatLen(unsigned char *ele, size_t elesize, long *regp) {
  hash >>= HLL_P; /* Remove bits used to address the register. */
  hash |= ((uint64_t)1<<HLL_Q); /* Make sure the loop terminates
  and count will be <= Q+1. */
- bit = 1;
- count = 1; /* Initialized to 1 since we count the "00000...1" pattern. */
- while((hash & bit) == 0) {
- count++;
- bit <<= 1;
- }
+
+ /* Initialized to 1 since we count the "00000...1" pattern. */
+ count = __builtin_ctzll(hash) + 1;
+
  *regp = (int) index;
  return count;
 }