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Re: Live range shrinkage in pre-reload scheduling


On May 15, 2014, at 6:46 PM, Ramana Radhakrishnan <ramana.gcc@googlemail.com> wrote:
> 
>> 
>> I'm not claiming it's a great heuristic or anything.  There's bound to
>> be room for improvement.  But it was based on "reality" and real results.
>> 
>> Of course, if it turns out not be a win for ARM or s390x any more then it
>> should be disabled.
> 
> The current situation that Kyrill is investigating is a case where we
> notice the first scheduler pass being a bit too aggressive with
> creating ILP opportunities with the A15 scheduler that causes
> performance differences with not turning on the first scheduler pass
> vs using the defaults.

Charles has a work-in-progress patch that fixes a bug in SCHED_PRESSURE_MODEL that causes the above symptoms.  The bug causes 1st scheduler to unnecessarily increase live ranges of pseudo registers when there are a lot of instructions in the ready list.

Charles, can you finish your patch in the next several days and post it for review?

Thank you,

--
Maxim Kuvyrkov
www.linaro.org



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