Performance comparison, ULE vs 4BSD and AMD64 vs i386

[Kenneth Culver]

Quoting David O'Brien <obrien at FreeBSD.org>:

> On Wed, Feb 25, 2004 at 11:07:54AM -0500, Kenneth Culver wrote:
>> The buildworld problem could just be because it takes longer for the 
>> compiler to
>> generate amd64 code. In fact, I'm almost willing to bet that's the 
>> case since
>> amd64 has 2x the GPR's that x86 does. It's likely that it's harder 
>> to optimize
>> for it. Does anyone who knows compilers care to comment?
>
> s/harder/slower/
>
> It is defineately easier to optimize for amd64 because if its increased #
> of registers.  But I'm not sure even "slower" is a valid claim -- on the
> i386 the compiler has to do a lot of time figuring out the best way to do
> the spill code (when, where).
>
> --
> -- David  (obrien at FreeBSD.org)


Ok well maybe not with amd64, but I thought that when you add registers it can
be harder/slower/whatever to optimize for since there are many more ways to do
so. Like on PowerPC or Alpha or whatever there are a LOT more GPR's than there
are on even Athlon64... I guess only having 2x the GPR's doesn't make a whole
lot of difference... but it still wouldn't surprise me if the gcc people didn't
have all the kinks worked out yet.

Ken