[llvm] [MachineLICM] Hoist COPY instruction only when user can be hoisted (PR #81735)

[via llvm-commits]

michaelselehov wrote:

> Do you have a test demonstrating the problem you are running into? We usually prefer that code is accompanied by a test case to make sure we don't accidentally break it again in the future.

I managed to reduce the test as much as I could. It's still 80+ lines of IR but the check is simple: there should be no spill reload in the loop.

https://github.com/llvm/llvm-project/pull/81735