[lld] [lld][ELF] Demote symbols in discarded sections to Undefined. (PR #68777)

[Bevin Hansson via llvm-commits]

bevin-hansson wrote:

Your alternate approach seems good, I was also worried about the performance impact of looking through all the symbols like that.

The TLS case was a bit unexpected to me. I wouldn't have thought that the demotion could cause any issues related to --gc-sections, since sections with references to them cannot be discarded by it.

https://github.com/llvm/llvm-project/pull/68777