bigint.c (lzb): use __builtin_clz() if available.
@@ -329,11 +329,19 @@ mpz_mul_int(mrb_state *mrb, mpz_t *x, mpz_t *y, mrb_int n)
/* number of leading zero bits in digit */
static int
-lzb(mp_limb a)
-{
+lzb(mp_limb x)
+{
+#if (defined(__GNUC__) || __has_builtin(__builtin_clz))
+ /* subtract 2 because DIGITBITS = LONGBITS-2 */
+ if (sizeof(mp_limb) == sizeof(long long))
+ return __builtin_clzll(x)-2;
+ else if (sizeof(mp_limb) == sizeof(int))
+ return __builtin_clz(x)-2;
+#endif
+
mp_limb i; int j=0;
- for (i = ((mp_limb)1 << (DIGITBITS-1)); i && !(a&i) ; j++,i>>=1)
+ for (i = ((mp_limb)1 << (DIGITBITS-1)); i && !(x&i) ; j++,i>>=1)
;
return j;
}
