[PATCH] D93818: [LangRef] Update shufflevector's semantics to return poison if the mask is undef

[Juneyoung Lee via Phabricator via llvm-commits]

aqjune added inline comments.


================
Comment at: llvm/docs/LangRef.rst:9453
 literals for a vector with a length unknown at compile time.
 
 Example:
----------------
aqjune wrote:
> jdoerfert wrote:
> > Don't we need  to talk about both poison and undef now? Sufflemask, for example, can still be undef, no?
> Combined with D103874, a mask value is constrained to either a constant integer or poison value.
> This is to avoid confusion - an undef mask and a poison mask have no difference. 
I was wrong, it can still be undef because the patch is not fixing the parser.

Allowing undef masks helps avoid parsing errors that will happen if the frontend emits a shufflevector with an undef mask.
I will explicitly state that shufflevector is still accepting an undef mask, but it will be printed as a poison mask.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D93818/new/

https://reviews.llvm.org/D93818