[llvm] [DSE] Stop double-counting the dead slice offset in shortenAssignment (PR #216227)

[Orlando Cazalet-Hyams via llvm-commits]

https://github.com/OCHyams approved this pull request.

I do enjoy a descriptive test comment, and I think these look good now. LGTM! thanks



https://github.com/llvm/llvm-project/pull/216227