factor: tweak gcd_odd performance

* src/factor.c (gcd_odd): Use stdc_trailing_zeros instead of
counting zeros by hand.

diff --git a/src/factor.c b/src/factor.c
index 0e9e703df45e989fda8b7b08855192a15fde27c8..13fb92f8de4dd5d6f63bb40e0cb9b3725dae3cc7 100644 (file)
--- a/src/factor.c
+++ b/src/factor.c
@@ -413,8 +413,8 @@ gcd_odd (uintmax_t a, uintmax_t b)
       uintmax_t t;
       uintmax_t bgta;
 
-      while ((a & 1) == 0)
-        a >>= 1;
+      assume (a);
+      a >>= stdc_trailing_zeros (a);
       a >>= 1;
 
       t = a - b;