Re: Using __builtin_expect (likely/unlikely macros)

[Paul Eggert]

Alex Gramiak wrote:
> > These macro calls would not help near calls to emacs_abort, as it should already
> > be obvious to a careful human reader that the jump to emacs_abort is the road
> > less traveled. (That's also obvious to GCC, since emacs_abort is _Noreturn.)

> To human readers, yes, but from what I can tell, GCC is mixed on this.

Then we should fix GCC, if the code it generates has a performance problem 
(whatever it is, it's quite small). That'd be better than littering the Emacs 
source code with __builtin_expect or UNLIKELY calls. The GCC manual recommends 
against manually inserting such calls; performance nerds are supposed to use 
-fprofile-arcs instead. In my experience the calls are typically more trouble 
than they're worth.