IRA performance regressions on PPC

[Vladimir Makarov]

Luis Machado wrote:
>
> This is a Power6 4.7Ghz (altivec supported)
>
>   
Great.  Now I have an access to power6.  So I am going to try it too.
>>   What options (especially march or mtune) you are using?  IRA is very 
>> sensitive to correct times of ld/st/moves in machine description.
>>     
>
> I'm currently using two tuning setups.
>
> base flags: -m64 -O2 -mcpu=power4
> peak flags: -m64 -O3 -mcpu=power4 -ffast-math -ftree-loop-linear -funroll-loops -fpeel-loops
>
>   
>>   What is overall IRA regression on SPEC2000?
>>     
>
> I don't have that information on this box yet. But i'll have it soon and
> will let you know. Right now i only focused on those two degraded
> benchmarks.
>
>   
>> You could use the same version of the compiler with IRA (default) and 
>> old RA (-fno-ira).
>>     
>
> Thanks for the tip. Is it a good idea to go through the ira-merge branch
> as well? Or would this suffice?
>
>
>   

H.J. Lu keeps ira-branch merge more fresh than trunk.  But the lag is 
only 1-3 days usually because gcc community and RA reviewers are very 
responsive.  So I don't see a big difference in using ira-merge and 
trunk.  I'd only recommend to apply patch

http://gcc.gnu.org/ml/gcc-patches/2008-09/msg00427.html

first because it is critical for performance but I don't know when it 
will be approved.