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Re: Conflicting IRA patches

On 07/13/2010 06:09 PM, Jeff Law wrote:
> On 07/13/10 09:49, Vladimir Makarov wrote:
>> I checked Bernd's patch on SPEC2000 on x86 (32-bit modes) last week. 
>> Code of few benchmarks changed (only vpr, gcc, crafty, parser, eon,
>> vortex, mesa, facerec, sixtrack, apsi).  The codes size for
>> SPECINT2000 was improved by 0.03% with patch and code size for
>> SPECFP2000 was worsen by 0.006%.   There is no visible
>> improvement/degradation on changed benchmarks.  Compilation time
>> increase was quite insignificant (less  than 0.2%).   So as I wrote
>> Ken Zadeck two years ago who tried to solve the problem for the old
>> RA, the complexity of the problem solution does not justify
>> the solution benefits.
> I wouldn't expect huge benefits, particularly since I doubt those
> benchmarks are highly dependent good allocation of double-word values. 
> We have a real benchmarking problem in that we don't have benchmarks
> that are highly dependent on double-word allocations.

Another issue - maybe on x86 most of the DImode regs get eliminated by
lower-subreg?  That's not the case on ARM, which doesn't run the
necessary splitters before reload.  It's probably something we should
fix, but it's made nontrivial by the existence of NEON insns and
registers which can operate on 64 bit values directly.


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