rational.c: short circuit optimization

* rational.c (nurat_reduce): short circuit when arguments are ONE,
  nothing is needed.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@57299 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

rational.c

@@ -488,7 +488,9 @@ nurat_canonicalize(VALUE *num, VALUE *den)
 static void
 nurat_reduce(VALUE *x, VALUE *y)
 {
-    VALUE gcd = f_gcd(*x, *y);
+    VALUE gcd;
+    if (*x == ONE || *y == ONE) return;
+    gcd = f_gcd(*x, *y);
     *x = f_idiv(*x, gcd);
     *y = f_idiv(*y, gcd);
 }