[llvm] [LoopDist] Add metadata for checking post process state of distribute… (PR #153902)

[Michael Berg via llvm-commits]

mcberg2021 wrote:

> Why a count instead of just a flag that marks the loop as already vectorized? `.count` looks like an instruction to the compiler to distribute into that number of os parts (compare `llvm.loop.unroll.count`).
> 
> LoopVectorizer's marker is `llvm.loop.isvectorized`.

Ok, I can do that.  It's functionally equivalent for our purposes.

https://github.com/llvm/llvm-project/pull/153902