[PATCH] D94964: [LangRef] Describe memory layout for vectors types

[Nuno Lopes via Phabricator via llvm-commits]

nlopes added a comment.

Overall LGTM. Thanks for documenting this! It was painful to reverse-engineer this when implementing it in Alive2..

My only concern is about leaving vector sizes not multiple of a byte as unspecified. Doing so is the same as saying those are illegal; can't be used in practice. Can we define those as being padded, where the padding is poison, like in structs? That allows using vectors where padding isn't easy, like <8 x i3>. How do you store that to memory if the direct store is left unspecified? And with people using weird integer sizes for ML & FPGAs, I think it's a good idea to define this case.
Alive2 is being conservative here and defining the padding as zero, but it should be poison IMHO.


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