[llvm] AMDGPU: Assume true in getVOPNIsSingle helpers (PR #98516)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> I don't think we should be relying on the default behavior. So wouldn't it make sense to mark your instructions of interest as isCodeGenOnly = 0, if they are actually getting printed? 

They are all printed and real instructions, except for the purposes of disassembly. They have ambiguous decodings we need to deal with, so the encoded aliases need to be isCodeGenOnly 

> Or set IsSingle on them? If we don't need a bit in TSFlags, it's better to not use it imo.

It is set, they don't end up in the VOP3InfoTable though because they are isCodeGenOnly 



https://github.com/llvm/llvm-project/pull/98516