[Mlir-commits] [llvm] [mlir] [mlir][vector] Prevent crashing on bitcast breakdown (PR #206683)

[Andrzej Warzyński]

banach-space wrote:

> I'm not sure I understand what the semantic question or gap is. Vector elements have a packed layout within the vector. What am I missing?

You will be more familiar with the "historical" background, but I actually wasn't able to find anything that would document this. 

I read `assert`s as an indication that the underlying semantics have been left as a TODO (or, that assumptions are made in the implementation that expect no such cases ever being encountered). That an my experience with "narrow type emulation" prompted my reservations regarding this change.

Separately, `Vector` semantics are effectively dictated by lowerings to LLVM and SPIR-V - what should we do with e.g. `vector<7xi3>` and operations on such types? IMHO, with no users, we should just restrict the semantics (so that the restrications/lack-of-support are explicit) and leave this as TBD. 

https://github.com/llvm/llvm-project/pull/206683