[PATCH] D103874: [IR] Rename the shufflevector's undef mask to poison

[Eli Friedman via Phabricator via llvm-commits]

efriedma added a comment.

> In practice, the frozen element won't be used in most of the cases; the middle-end's demanded elements analysis will trigger instcombine to almost always remove the freeze.

Well, in the cases it gets removed, it doesn't really matter what we use.  It's likely if someone is reaching for these more obscure constructs, they're seeing that the compiler isn't doing what they want with more normal code, though.

> What do you think? If people agree with the shufflevector+freeze lowering, I'll create a separate patch that lowers this to the new freeze+shufflevector format (since it is already incorrect).

Using "freeze poison" seems reasonable.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D103874/new/

https://reviews.llvm.org/D103874