[PATCH] D65884: [ARM] MVE Tail Predication

[Sjoerd Meijer via Phabricator via llvm-commits]

SjoerdMeijer added a comment.



> The overall plan is as follows:
> 
> - Enable vectorizer.
> - Teach the vectorizer to produce a predicated loop, using a pragma and a target profitability hook. Think we also need to specify that we support masked load/store intrinsics too.
> - This pass converts some vector icmps to vctp intrinsics.
> - A bit of isel for vctp and final bits for other MVE instructions.
> - The loop is finalised in the LowOverheadLoop pass where we check for validity and remove the VCTP and VPST instructions, as well as their VPT blocks.
> - Beer.

Thanks for this! That's quite a lot of moving parts!
Thinking out loud what the strategy could be so that we properly test the whole flow..... One would be to start with the ground work: enabling the vectorizer is flipping a switch, we can already produce a predicated loop with a pragma (target profitability hook is missing), and a bit of isel should also be easy. With the small(er) and easier groundwork in, we then have the 2 biggies remaining: this patch, and the LowOverheadLoop pass modifications. But when we have these 2 ready, we can test the flow and check if we haven't missed anything (that could change the design/flow).
Another option is to commit this once we're happy with it as it won't be enabled/triggering. Then we will have to see how it behaves when tail predication support is ready in LowOverheadLoop (and the other bits and pieces).


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https://reviews.llvm.org/D65884