[PATCH] D68982: [TargetLowering][DAGCombine][MSP430] Shift Amount Threshold in DAGCombine

[Joan LLuch via Phabricator via llvm-commits]

joanlluch added a comment.

Hi @spatel 
Thank you for your support. I'll try to do what you suggest regarding generating of baseline tests and splitting the patch.

My primary interest is proposing LLVM improvements that will benefit targets of the MSP430 kind, but -just to clarify- I only know what I learned online about that particular target. In fact, I have little practical interest on it, except that it allows me to show the validity of my proposed patches. The same can be said about the 'experimental' AVR target. The AVR is even more benefited from this patch, but I am not even showing it. It would be REALLY nice to get some involvement (or just feedback) from people who implemented or worked on these targets in the past, because I am not able to work on them.

So, given the above, I want to ask whether there would be a generic (or target independent) way to show the effects of this patch. Ideally, given some IR input, demonstrate that the output will minimise the generation of expensive shifts, which some targets will benefit of. It's understandable that showing this in the context of a particular trunk target makes it easier to get approval, but as I am relatively new to LLVM development, I still wonder if there's a target independent way to show the same. Any help would be appreciated.

Thanks.


Repository:
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https://reviews.llvm.org/D68982