[llvm] [DEBUGINFO] Propagate debug metadata for sext SDNode. (PR #135971)

[Alexander Peskov via llvm-commits]

apeskov wrote:

> We only go sext `(sext x) ->sext x` or `sext (zext x) ->zext x`, never `sext (zext x) -> sext x`. Right?

You are right, `sext (zext x) -> sext x` is not the case. In other words, debug data is only transferred between nodes with identical opcode. 

https://github.com/llvm/llvm-project/pull/135971