[PATCH] D134950: [CodeGen] Allow targets to define vreg flags

[Matt Arsenault via Phabricator via llvm-commits]

arsenm added a comment.

In D134950#3854402 <https://reviews.llvm.org/D134950#3854402>, @qcolombet wrote:

>> much appreciate it if you could give feedback on the vreg flags.
>
> I think that could be fine as long as we specifically say that they can be dropped inadvertently, i.e., you can't rely on them.
>
> That said, I believe that if we put such language, you wouldn't be able to do what you want since in theory the information could be inaccurate and at this point, having this information or no information is pretty much the same. (I would actually argue that no information is probably better!)

They really can't be dropped. Missing information will be just as wrong. What we really want is to establish a dynamic value class. It's like a register class, except it can't map one to one with a physical register since in other contexts the same physical register could be used differently.


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