Re: Using __builtin_expect (likely/unlikely macros)

[Paul Eggert]

Óscar Fuentes wrote:
> > For improvements where the
> > generated code is "obviously" faster (fewer and simpler instructions,
> > say), I typically don't bother with measurements as my own time is
> > limited too.
> You will be surprised.
>
> Modern hardware is complex.

I'm often surprised :-), but I don't expect to be surprised when the generated 
code seems obviously faster to me. Although I'm not as expert as the computer 
architecture researcher whose office sits next to mine, I know how modern 
hardware works reasonably well and regularly give lectures on topics like μops 
and TLBs so I won't be surprised as often as a naive programmer might be.
> If the 1.3% improvement in performance requires non-minimal source code
> complexity growth

It doesn't. In this case the source code shrank slightly. Only very slightly: 
just by 0.001% (this counts all files under Git control). Still, a win's a win.