[llvm] [NVPTX] Don't use stack memory when bitcasting to/from v2i8 (PR #113928)

[via llvm-commits]

peterbell10 wrote:

>> we hit the default legalization rules which perform the bitcast in stack memory

>Do you know where this default legalization rule is implemented?

For bitcast to `v2i8` we hit
https://github.com/llvm/llvm-project/blob/87b6ec3be6b80f8e35d2eaea468e6bca79e79c2e/llvm/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp#L562-L563

And for bitcasts from `v2i8` we hit
https://github.com/llvm/llvm-project/blob/87b6ec3be6b80f8e35d2eaea468e6bca79e79c2e/llvm/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp#L2156


https://github.com/llvm/llvm-project/pull/113928