[llvm-dev] llvm-reduce for MIR

[Arthur Eubanks via llvm-dev]

+1, this would be a cool addition to llvm-reduce.

On Tue, Aug 17, 2021 at 1:08 PM Quentin Colombet via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> Hi Markus,
>
> On Aug 17, 2021, at 2:04 AM, Markus Lavin via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
> Has anyone thought about extending llvm-reduce to also be able to do
> reduction on MIR?
>
>
> Thought about it, yes, doing anything about it, no :).
>
>
> The current tool itself seems quite modular and nicely structured with the
> delta-algorithm separated from the actual IR specific reductions.
> When reducing IR instructions (ReduceInstructions.cpp) it just does RAUW
> undef and then eraseFromParent so in theory it seems it would be possible
> to do a similar thing for MIR. At least while on SSA form one could either
> RAUW $noreg or perhaps a dominating definition of the same register class.
> So maybe it would not be too much work to add a set of MIR specific
> reducers (at least for MBB and MI) and generalize the remaining part of the
> tool (module import and verification) to able to handle both IR and MIR.
>
> At least for me manually reducing MIR is quite slow an painful so any
> automation here would be appreciated.
>
> Of course in general MIR is more constrained that IR so it may be “a bit”
> more complicated than outlined here, but still seems worth a try.
>
> Any thoughts on this?
>
>
> Having such tool would be super useful!
>
> On a somewhat related note, I built a tool to extract a basic block from
> MIR (i.e., like llvm-extract but on MIR). I’ve never bothered cleaning it
> up and open sourcing it, but if there is interest for that I could
> certainly push that out.
>
> Cheers,
> -Quentin
>
>
> -Markus
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