[clang] [lld] [llvm] [DTLTO] Refactor the DTLTO code. (PR #192629)

[Teresa Johnson via cfe-commits]

teresajohnson wrote:

> @teresajohnson , I had divided `DTLTO.cpp` into three source files for easier review:
> 
> 1. `DTLTOInputFiles.cpp` : input files/archive members handling logic.
> 2. `DTLTO.cpp`:  invokes ThinLink, collects necessary information and prepares compilation jobs.
> 3. `DTLTODistributionDriver.cpp` : serializes compilation jobs into JSON format and invokes of a script that is responsible for passing compilation jobs to a specific distributed build system.

I meant break up in terms of different PRs, but I'll review it as is if that isn't possible.

However, the PR seems to be in an odd state? I don't see these files and a ton of reviewers got added, and I also see some fixes that seem to have been undone (e.g. the change to CleanUp in LTO::run is back).

Also, if you can avoid force pushing that would make reviewing significantly easier - with force pushing I can't compare to prior versions of the PR in github, so I have to restart the review from scratch after every force push which for a PR this large makes the review take even longer.

https://github.com/llvm/llvm-project/pull/192629