[PATCH] D33673: [Object/RelocVisitor] - Add support for R_X86_64_DTPOFF32 relocation.

[George Rimar via llvm-commits]

>One interesting thing to note is that we don't actually want to relocate
>these sections. What we want is to read the relocation, in a similar
>way that lld does on the scanRelocs. For example, when reading
>DW_AT_low_pc, we don't want the final value, we want what it points to
>(section and offset). With elf_rela we can find that with no knowledge about
>relocations and with elf_rel we only need to know how to read the
>implicit addend.
>
>Cheers,
>Rafael

Yes, for .debug_ranges we do not have to perform relocations and just need
to know the section index.
Though in general it is not clear that it worth to optimize here (we still need to scan relocations).

While we do relocations on DWARF parsers side, LLD code remains clear. Each additional optimization for .gdb_index
will make it more specific. Generally observing MSVS profiling reports I can't say we can win much here.
Sure relocations are generally expensive, but we may probably want to focus on something not so .gdb_index specific,
as far I understand after last commits we are "slow" just because parsers are too generic. (though .gdb_index generation atm is much faster than it was few month ago).

George.