[PATCH] D123587: [SLP] Generate shuffles if we can reorder an existing node

Tue Apr 19 05:52:19 PDT 2022

ABataev added a comment.

In D123587#3458777 <https://reviews.llvm.org/D123587#3458777>, @dmgreen wrote:

> Oh yeah. I'm not sure about the first, but D110978 <https://reviews.llvm.org/D110978> seems like it might be a larger change that handles this case and a lot more. Apparently it's 1200 lines of changes? That sounds like a lot! It tries to re-build the shuffles after from the extracts?
> In this case I "just" need vector combine to see the shuffle, not the insert/extract, as instcombine doesn't run between the two.

No, it tries to do the same as your patch - find reused scalars in the previously build nodes and emit shuffles, if possible, instead of bunch of extracts.
The problem is that we need to track the dependencies between nodes, that's why it is so big.

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https://reviews.llvm.org/D123587