[lld] [lld][AArch64][ELF][PAC] Support `.relr.auth.dyn` section (PR #87635)

[via llvm-commits]

zeroomega wrote:

> > Since this patch introduced an issue that lld fail to link the file it generated. Could we revert this change? Other people who uses relocatable linking on aarch64 will likely hit the same issue once they upgrade their lld.
> 
> Well, it is great that this issue was found. So, it should be treated as normal bug / missed functionality. Normally per developer policy we do not revert unless it breaks the bot or is known regression wrt some test existing in the mainline.

I don't think the revert policy you mentioned is correct.
Per https://www.llvm.org/docs/DeveloperPolicy.html

> The changes should not cause performance or correctness regressions in code compiled by LLVM on all applicable targets.

In this particular case. lld now generates invalid output (it rejects its output as its input) on AArch64 (a supported target) with relocatable linking (a supported feature). We happened to discovered it in field. This should have covered by lld tests but it such tests did not exist in the current LLVM. I think it is a valid request to revert this change, fix it, combined with additional testing and re-land it. It is a correctness issue which is now observed and validated.


https://github.com/llvm/llvm-project/pull/87635