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Re: Finding insns to reorder using dataflow


On 08/13/2015 05:06 AM, Kyrill Tkachov wrote:
Hi all,

I'm implementing a target-specific reorg pass, and one thing that I want
to do
is for a given insn in the stream to find an instruction
in the stream that I can swap it with, without violating any dataflow
dependencies.
The candidate instruction could be earlier or later in the stream.

I'm stuck on finding an approach to do this. It seems that using some of
the dataflow
infrastructure is the right way to go, but I can't figure out the details.
can_move_insns_across looks like relevant, but it looks too heavyweight
with quite a lot
of arguments.

I suppose somehow constructing regions of interchangeable instructions
would be the way
to go, but I'm not sure how clean/cheap that would be outside the scheduler

Any ideas would be appreciated.
I think you want all the dependency analysis done by the scheduler.

Which leads to the question, can you model what you're trying to do in the various scheduler hooks -- in particular walking through the ready list seems appropriate.

jeff


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