2010-10-23 (í), 18:21 +0100, Al Viro: > On Sun, Oct 24, 2010 at 02:06:15AM +0900, Namhyung Kim wrote: > > Convert bitwise-OR operator to logical-OR in favor of short-circuit > > evaluation. The end result would be same. > > It'll cost _more_. > > Think of it: > v = atomic_read(...) > w = bh->b_state > w &= constant > v |= w > return v > vs. > v = atomic_read() > branch to l if not equal to 0 > w = bh->b_state > if w & constant is not 0, branch to l > v = 0 > return v > l: v = 1 > return v > > That short-circuit won't win anything here. I see. It adds expensive branch insns. I just checked that patched code generated longer code, Cool. But what if I exchange the order of evaluation, check the bitmask before atomic_read()? Isn't it helpful either? Thanks. -- Regards, Namhyung Kim -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html