[llvm] [DecoderEmitter] Eliminate `DecodeComplete` parameter to `decodeToMCInst` (PR #159130)

[Sergei Barannikov via llvm-commits]

s-barannikov wrote:

> Currently, the code generated by decoder emitter always set `DeocdeComplete` to false when returning Fail from `decodeToMCInst`.

As I noted in the other PR, this is not exactly true. It only sets it to false when `TryDecode` fails. If `Decode` fails, it does not change the value of `DecodeComplete` and it remains `true` (initialized at the beginning of `decodeToMCInst`).

We should be careful here not to break downstream targets without providing a working replacement.


https://github.com/llvm/llvm-project/pull/159130