[llvm] [SelectionDAG] Salvage debuginfo when combining load and z|s ext instrs. (PR #188544)

[Orlando Cazalet-Hyams via llvm-commits]

https://github.com/OCHyams requested changes to this pull request.

Latest change looks good but you missed a comment in one of the tests. Bringing the question into the not-inline comments:

Is the from/to cast the wrong way around in the DIExpressions? Since we want to undo the effect of the ext for the variable location (opposite to usual salvaging, which wants to preserve the effect of an instruction that is deleted).

https://github.com/llvm/llvm-project/pull/188544