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Re: Fwd: [PATCH] Scheduling result adjustment to enable macro-fusion


On Wed, Sep 4, 2013 at 12:33 PM, Alexander Monakov <amonakov@ispras.ru> wrote:
> On Wed, Sep 4, 2013 at 9:53 PM, Steven Bosscher <stevenb.gcc@gmail.com> wrote:
>>
>> On Wed, Sep 4, 2013 at 10:58 AM, Alexander Monakov wrote:
>> > Hello,
>> >
>> > Could you use the existing facilities instead, such as adjust_priority hook,
>> > or making the compare-branch insn sequence a SCHED_GROUP?
>>
>>
>> Or a define_bypass?
>
> Hm, I don't think define_bypass would work: it still leaves the
> scheduler freedom to move the compare up.

Even though it allows the scheduler freedom to move the compare up,
the schedule does due to the schedule model not being correct for the
processor.  I have done the same for Octeon2 where it is able to
combine the compare and the branch and found the resulting schedule is
much better than even what this hack could do due to the instructions
still take a issue slot.  Is it true that for these two processors it
takes an issue slot or is it being done before issue?

Thanks,
Andrew Pinski

>
> IMO adjust_priority would be preferable if it allows to achieve the goal.
>
> Alexander


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