Re: Kernel GCC Optimizations

[scott thomason]

On Saturday 21 December 2002 04:10 pm, [e-mail] wrote:
> > > Is there any risk using -O3 instead of -O2 to compile the
> > > kernel, and why?
> >
> > * It might uncover subtle bugs that would otherwise not occur.
>
> I wonder: for the sake of performance and good use of the precious
> clock- cycles, shouldn't there be made a start of fixing those
> bugs? Assuming that the bugs you're talking about are not
> compiler-bugs, they *are* bugs in the code that should be fixed,
> shouldn't they?
>
> > * Compiling with unusual options means that less people will know
> > about any problems it causes you.
>
> So, let's make it -O6 per default for 2.7.x/3.1.x?

Let's not. I'd rather have the best kernel developers concentrating on 
finishing important kernel features rather than digging their way out 
of esoteric optimizer debugging sessions only to find it was a flaw 
in gcc. The difference in performance boost between -O2 and greater 
levels isn't usually enough to make a significant impact, not as 
significant as the introduction of important new features, for 
example.
---scott