Add a MIR pass manager, take 2

[ecstatic-morse]

A more powerful version of #77665.

The goal is to allow fine-grained ordering constraints between passes and to make violating those constraints a compile-time error (and partly to motivate #90488 😏). The compile-time part would be very hard when enforcing constraints across queries, so we continue to rely on MirPhase for things like "optimizations run after drop elaboration". However, it works okay within a single invocation of run_passes (e.g. all the optimizations), where adding a few constraints to each pass is less of a pain than adding a bunch of variants to MirPhase. Since constraints are declared explicitly, we can do cool stuff like check that they hold for all possible opt-levels, -Z flags, etc.

For now it's just a proof of concept, and a silly one at that. I don't know that we ultimately want to go in this direction, but it was pretty fun. It turns out writing nested for loops in a const-context leads to some pretty ugly code. @oli-obk might be into it at least 😄. I only translated one small section of MIR passes so that people could get a feel for how it would look. We probably will want a different interface; the batch of associated constants is pretty unpleasant to look at IMO.

All the interesting stuff is in the last few commits. The rest are refactorings or const-eval stuff to get everything working. Ideally, each pass would declare which cleanup passes it needs, but for that I'll need to move all the MIR passes back into rustc_mir_transform.

[ecstatic-morse]

r? @ghost

[rust-log-analyzer]

The job mingw-check failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

    Checking rustc_mir_transform v0.0.0 (/checkout/compiler/rustc_mir_transform)
error: unused import: `Lint`
  --> compiler/rustc_mir_transform/src/lib.rs:41:26
   |
41 | use self::pass_manager::{Lint, MirPassC};
   |
   |
   = note: `-D unused-imports` implied by `-D warnings`
error: could not compile `rustc_mir_transform` due to previous error
warning: build failed, waiting for other jobs to finish...
error: build failed
Build completed unsuccessfully in 0:02:51

[bjorn3]

This changes the condition. Before it would always run if -Zinline-mir=yes is used, never if -Zinline-mir=no is used and only for mir opt level >= 3 if -Zinline-mir is not specified. After it will only run when -Zinline-mir=yes and mir opt level >= 3 is combined.

[ecstatic-morse]

Ah. I'm sorry. I understand the Option<bool> now.

[bors]

☔ The latest upstream changes (presumably #91469) made this pull request unmergeable. Please resolve the merge conflicts.

[ecstatic-morse]

Closing in favor of the more minimal #91475. I'd like to explore some of these ideas in the future, though.