[PATCH] D55301: RegAlloc: Allow targets to split register allocation

[Matt Arsenault via Phabricator via llvm-commits]

arsenm added a comment.

In D55301#1323324 <https://reviews.llvm.org/D55301#1323324>, @qcolombet wrote:

> > I'm not sure I follow this. These aren't spilled with ordinary copies
>
> I would expect that you could use ordinary copies + subreg here and do the proper expansion in the later expand post RA pass like every other copy.


We don't model different lanes as subregisters, and trying to would be a pretty radical change. I can almost see a way to hack it to work, but it would involve adding an enormous number of new subregister indexes. Unless you mean using some kind of RMW copy (since the old single lane view of the register's value needs to be preserved)


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