[llvm] [llvm] Issues found PVS studio static analyzer. LoopUnrollAndJam.cpp (PR #170162)

[Ryotaro Kasuga via llvm-commits]

kasuga-fj wrote:

> When var J = I, then we are checking the dependency of an instruction with itself, is that check even necessary?

Yes, it's necessary.

By the way, this change seems to coincidentally preserve the original behavior, since `checkDependency` immediately returns true for the two same instructions. This is a bug. I created an issue. https://github.com/llvm/llvm-project/issues/170848

https://github.com/llvm/llvm-project/pull/170162