[LLVMdev] LLD improvement plan

[James Y Knight]

On May 29, 2015, at 10:08 PM, Rui Ueyama <ruiu at google.com> wrote:
> Large part of the difficulties in development of the current LLD comes from over-generalizataion to share code between pretty much different file formats.

ISTM the problem that's been described isn't that code is shared between file formats, but that an internal representation was chosen based on what MachO required, which in the end turned out to be unsuitable for representing the greater generality allowed by the other two file formats.

You state that the goal is to use this new model for ELF too, assuming it proves itself worthy. Will ELF and COFF not share most of the core of the code at that point?

And once COFF and ELF are taken care of, do you not think the new model will be suitable for MachO, too? It seems to me that it ought to be able to handle MachO's needs just fine, with a suitable division of MachO sections into "Chunk"s.

Perhaps once everything is said and done, lld can once again have a single core model. I think that may be what Sean was trying to get at -- not that it's wrong to create a new model as a base, but that the expectation should be that new model will be _the_ model used in LLD, not a second model to be kept permanently alongside the current "single-symbol-per-atom" model, which has been shown insufficient.