Re: Ping: IRA-based register pressure calculation for RTL loop invariant motion

[Vladimir Makarov <vmakarov@redhat.com>]

David Edelsohn wrote:
> On Mon, Oct 19, 2009 at 12:17 PM, Vladimir Makarov <vmakarov@redhat.com> wrote:
>
>   
>>> I think we could switch it on by default at -O3 for a selected group of
>>> targets.  Itanium overall also improves with the new heuristics.  That
>>> would
>>> make it power and Itanium.
>>>       
>> The patch is below.  Ok to commit?
>>     
>>>  Did you try restricting the heuristics to certain
>>> register classes, like SSE registers on x86_64?
>>>
>>>
>>>       
>> No, I did not try.  I am not sure it is worth to do  it.
>>
>>
>> 2009-10-19  Vladimir Makarov  <vmakarov@redhat.com>
>>
>>   * doc/invoke.texi (fira-loop-pressure): Update default value.
>>   * opts.c (decode_options): Remove default value setting for
>>   flag_ira_loop_pressure.
>>   * config/ia64/ia64.c (ia64_override_options): Set
>>   flag_ira_loop_pressure up for -O3.
>>   * config/rs6000/rs6000.c (rs6000_override_options): Ditto.
>>     
>
> Tests inside IBM do not show this IRA feature as an overall win for
> POWER.  If we figure out and fix why artificially limiting
> rs6000_issue_rate to 1 for the first scheduler pass still helps (and
> it does), then this would make sense.  Until then, please do not apply
> this patch to rs6000.
>
>   
David, I think there is some misunderstanding.  It is a different 
patch.  You are probably talking about register pressure sensitive insn 
scheduling (by the way I am still working on its tuning).  This patch is 
about more accurate register pressure calculation to decide 
profitability to do RTL loop invariant motion.  SPEC2000 and polyhedron 
benchmarks for power6 shows that this patch is a clear win.  You could 
test and benchmark this patch internally in IBM to confirm or deny my 
observation if you wish.