[LLVMdev] specializing hybrid_ls_rr_sort (was: Re: Bottom-Up Scheduling?)

Andrew Trick atrick at apple.com
Mon Dec 19 07:41:11 PST 2011

On Dec 19, 2011, at 6:51 AM, Hal Finkel <hfinkel at anl.gov> wrote:

> On Tue, 2011-10-25 at 21:00 -0700, Andrew Trick wrote:
> Now, to generate the best PPC schedules, there is one thing you may
>> want to override. The scheduler's priority function has a
>> HasReadyFilter attribute (enum). It can be overriden by specializing
>> hybrid_ls_rr_sort. Setting this to "true" enables proper ILP
>> scheduling, and maximizes the instructions that can issue in one
>> group, regardless of register pressure. We still care about register
>> pressure enough in ARM to avoid enabling this. I'm really not sure how
>> much it will help on modern PPC implementations though.
>> hybrid_ls_rr_sort
> Can this be done without modifying common code? It looks like
> hybrid_ls_rr_sort is local to ScheduleDAGRRList.cpp.
> Thanks again,
> Hal

Right. You would need to specialize the priority queue logic. A small amount of common code.

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