enabling instrumentation for stage 3 compilers

[nobellium1997]

This commit allows users to instrument their stage 3 compilers.

This PR is a revival of the following PR: #101744

The aim is to break up the PR into smaller chunks and merge these changes in piecemeal. The PR here is to allow us to instrument stage 3 rust compilers as stage 3 instrumentation is part of how we create profiles for guided optimization later on.

[rustbot]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @jieyouxu (or someone else) some time within the next two weeks.

Please see the contribution instructions for more information. Namely, in order to ensure the minimum review times lag, PR authors and assigned reviewers should ensure that the review label (S-waiting-on-review and S-waiting-on-author) stays updated, invoking these commands when appropriate:

• @rustbot author: the review is finished, PR author should check the comments and take action accordingly
• @rustbot review: the author is ready for a review, this PR will be queued again in the reviewer's queue

Why was this reviewer chosen?

The reviewer was selected based on:

• Owners of files modified in this PR: bootstrap
• bootstrap expanded to 6 candidates
• Random selection from Mark-Simulacrum, clubby789, jieyouxu

[Kobzol]

Hi, could you say more about the use-case please? (the change looks simple enough though)

[jieyouxu]

I'm curious to hear more on ^ as well, but the change itself seems reasonable indeed.

[nobellium1997]

许杰友 Jieyou Xu (Joe) ***@***.***> writes:

jieyouxu left a comment (rust-lang/rust#157930) I'm curious to hear more on ^ as well, but the change itself seems reasonable indeed. -- Reply to this email directly or view it on GitHub: #157930 (comment) You are receiving this because you authored the thread. Message ID: ***@***.***>

Hi sorry honestly I'm trying to figure out why we instrument the stage 3 compiler myself. Our optimization pipeline is quite complex so it's taking me a while to understand it. I think for now we can simply un-assign this PR while I try to understand things better.