[llvm] [X86] combineTruncate - trunc(srl(load(p),amt)) -> load(p+amt/8) - ensure there isn't an interdependency between the load and amt (PR #165850)

[Simon Pilgrim via llvm-commits]

https://github.com/RKSimon auto_merge_enabled https://github.com/llvm/llvm-project/pull/165850