On Thu, May 09, 2002 at 07:51:23PM +0000, Sung N. Cho wrote:
> I was wondering, shouldn't turning on the optimization for gcc make the 
> kernel bigger?

Probably not.  Most of the 'optimisations' that increase code size
(eg loop unrolling and function inlining) are IMHO probably
deoptimisations for modern hardware.  Indeed I don't think O3
enables them.
> 
> I added in my /etc/mk.conf the following lines:
> 
> COPTS+= -O3 -mcpu=i686 -march=i686
> CXXFLAGS+= -O3 -mcpu=i686 -march=i686
> CFLAGS+= -O3 -mcpu=i686 -march=i686
> 
> Then compiled the kernel.  The prior size for the kernel which was compiled 
> with default -O2 option was 2.4M.  This new kernel with -O3 option turned on 
> have now even smaller size, 1.8M!

How are you measuring the size?
You need to use 'size' not 'ls'!

If you are seeing a 25% reduction it might be worth looking at
some of the generated code.  Such a large change probably involves
a major change in the way code has been compiled!

	David

-- 
David Laight: david@l8s.co.uk