[PATCH] D73317: [GISelKnownBits] Add support for PHIs

[Amara Emerson via Phabricator via llvm-commits]

aemerson added a comment.



In D73317#1839841 <https://reviews.llvm.org/D73317#1839841>, @qcolombet wrote:

> Thanks @arsenm for the review!
>
> > You could potentially want to write code that relied on an instruction definitely being inserted
>
> As long as it doesn't need to be a new one, we could return the definition of the source.
>  But agree, some places actually expect that we produce a new register and that's not going to be an easy fix.


I'm not fond of the idea of doing something like:

  MIB.setInsertPt(Insn);
  MI = MIB.buildOp(...)

and having the builder silently ignore the explicitly setInsertPt. I think that behavior should be opt-in only to CSE, and obvious when it's being done.


Repository:
  rG LLVM Github Monorepo

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https://reviews.llvm.org/D73317