Re: RFA: patch - tuning gcc for Intel Nocona (64 bit).

[Jan Hubicka <hubicka at ucw dot cz>]

>  The following patch tunes gcc to Nocona Xeon.  The SPEC2000
> results for mainline gcc for 2.8Ghz Nocona Xeon in 64-bit mode (using
> x86_64 insns) are given below.
> 
>  SPECFP2000 is 28% faster with the tuning.  SPECInt2000 is 0.6%
> faster.  The code size (text segment) is also usually smaller.

Interesting.  I have almost equivalent patch I intended to send (but
didn't find time to do it yet) and definitly didn't get 28% specfp
improvement relative to current -march=nocona.  I have to dig into
differences to your tables.
(in fact my patch was causnig few regressions in some tests that made me
to hold it until I find time to investigate it)
> 
>  IMHO, there are still other possibilities to tune the code for
> Nocona.  These ones are only the simplest ones.
> 
>  I see one problem what tunning will be the default for x86_64.  I
> don't think that e.g. Linux distributions will have different code for
> Intel Nocona and AMD Opteron.

I would guess that we can wait until Noconas are out here.  We may want
to invent switch to generate code that runs well on both cora.  m68 port
used to have such a switch and I guess it would make sense nowdays too.

Honza