Optimising GCC for a PentiumMMX system?

[John Gay <johngay at eircom dot net>]

I have quite a bit of time on my hands now, so I decided to take the plunge 
and try building a complete GNU/Linux system from source on an idle 
PentiumMMX box I've got. I started by just installing a base Debian system 
and building XFree86 and KDE3 from sources, but considered what else I should 
try to optimise. GlibC was suggested as a bare minimum to optimise, then It 
was suggested that GCC might be another candidate. Eventually I was given a 
pointer the Linx From Scratch adn that got me thinking about just going ahead 
and building the entire thing.

Interestingly, though, the lfs site says do not try to optimise GCC or GlibC? 
Now, it seems to me that, first, the kernel handles most low-level functions, 
so optimising the kernel would yield the largest improvements. Next, GlibC 
provides the next level of interaction between user apps and the kernel 
system calls, so this seems to be a likely candidate for optimising.

While checking possible optimisations for GCC I found PGCC which suggests 
that GCC does not take effective advantage of some of the pipelining features 
provided by the Pentium class. However, the site seems to be out of date. The 
latest patches are for gcc2.95.3 and the front page says it was last updated 
in 2000!

I was wondering if these complaints about GCC were still relevant to the 
3.1.x series now available. The lfs uses gcc2.95.5 but that should not be too 
much trouble to update if it would yield significant inprovements.

I realise that MMX is not something that can be optimised for in the compiler 
so I woun't even ask. However, If I have a generally good experience I am 
considering doing the same wit my regular system, a Dual PII with a 440BX 
chipset, once I can find a match for the PIII I've got waiting to put into 
it. XFree86 and the DRI stuff can be compiled toa take advantage of the SSE 
instructions the PIII provides.

So, my question is, are the PGCC patches still relevant ro should I just 
stick with gcc itself?
Also, should I attempt to optimise GlibC? 
The lfs site says don't try it, but it seems the most likely area for speed 
improvement after the kernel. All of this is just a personal exercise to see 
just how fast I can get this box to run with KDE. Any small speed 
improvements will add up, at least for CPU bound areas.

Thanks for your time and information!

Cheers,

	John Gay