[lld] [lld] Merge GOT entries for symbols that have been ICFed (PR #131630)

[Reid Kleckner via llvm-commits]

rnk wrote:

I chatted more about this Pranav, and I think maybe the right way to think about this change is that it is merging duplicate GOT entries for non-preemptible symbols pointing to the same offset with the same type.

If I have 15 protected visibility aliases that all point to the same symbol (no ICF involved), I only need one GOT entry, not 15. This is not just a corner case correctness fix, it's an optimization. To make that clearer, maybe the next step is to move this map of {section, offset, type} to got-index over to Relocations.cpp so that it's clearer what the purpose and lifetime of this data is.

https://github.com/llvm/llvm-project/pull/131630