[llvm] [GlobalISel]: G_UNMERGE_VALUES for vectors with different element sizes (PR #133335)

[Jay Foad via llvm-commits]

jayfoad wrote:

> This commit rejects different source and destination vector elements for G_UNMERGE_VALUES, e.g.: `%1:_(<2 x s8>), %2:_(<2 x s8>) = G_UNMERGE_VALUES %0:_(<2 x s16>)`

That case should already be rejected by MachineVerifier (https://github.com/llvm/llvm-project/blob/b2bf017acd0369fff89b933cf7c653f62b49f8d3/llvm/lib/CodeGen/MachineVerifier.cpp#L1507), therefore it is not legal and nothing should have created it in the first place.

https://github.com/llvm/llvm-project/pull/133335