Re: Patch proposal: use __builtin_expect

[Anthony Green <green at cygnus dot com>]

Andrew wrote:
> Hmm.  So __builtin_expect means that we expect the result *not* to be
> true; it actually means "expect false". 

Not quite.  You always provide the expected result.  I always gave `0',
so it does mean expect false in those cases.

    __builtin_expect (x, 5)

...means we expect x to be 5.  It seems safest/easiest to just expect 0.
You can also do things like..

  if (__builtin_expect (x, 0) == 5)
  {
    // Handle the unlikely case that x == 5.
  }


AG

-- 
Anthony Green                                                        Red Hat
                                                       Sunnyvale, California