[llvm] [ARM] Update IsRestored for LR based on all returns (PR #82745)

[Florian Hahn via llvm-commits]

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

LGTM, thanks for fixing!

Would be good to pre-commit the test case separately. Also, it looks like the title of the PR is also included in the description, please make sure the title isn't duplicated in the final commit message.

https://github.com/llvm/llvm-project/pull/82745