[llvm] [AMDGPU] select v_sat_pk from two i16 or v2i16 (PR #121124)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> Hi @arsenm , maybe we can use TRUNCATE_SSAT_U node for the 2 of i16 case, but the v2i16 case maybe not, since the result of the truncation is v2i8, which causes compilation fail for the current backend I think.

The illegal type doesn't mean you have to throw away the whole thing and implement your own pattern matching. You can still custom lower the illegal type, you'll just need to process it into a wrapper node that does use a legal type plus a cast.






https://github.com/llvm/llvm-project/pull/121124