[llvm] [LICM] Handle conflicting preheader defs (PR #195510)

[Arda Serdar Pektezol via llvm-commits]

pektezol wrote:

@nikic I took another look at this. Changed it to handle it under canSinkOrHoist in LICM, since you already mentioned it. I am planning to improve this on a seperate PR by using the AA from my first iteration. This would also address the FIXMEs inside pointerInvalidatedByLoop.

https://github.com/llvm/llvm-project/pull/195510