[llvm] [NVPTX] don't erase CopyToRegs when folding movs into loads (PR #149393)

[Artem Belevich via llvm-commits]

Artem-B wrote:

@Prince781 the cerry-pick may not apply cleanly. Would you be able to make a PR with a mergeable patch for the release if the automatic cherrypick fails?

https://github.com/llvm/llvm-project/pull/149393