rustc_mir: hardcode pass list internally and remove premature pluggability.

[eddyb]

Fixes#41712 by moving the MIR pass lists from rustc_driver to rustc_mir.
The application of the passes is done with the rustc_mir::transform::run_passes macro, which is public, as are all the passes AFAIK, and can be used to apply MIR passes outside of rustc_mir.

With the ability to override query providers through the rustc_driver (orthogonal to, and not included in this PR), custom drivers will be able to substitute the entire pass list if they want to.
EDIT: the aforementioned ability is added by #45944.

r? @nikomatsakis

[nikomatsakis]

r? @nikomatsakis

[nikomatsakis]

@bors r+

[bors]

📌 Commit 9eadc36 has been approved by nikomatsakis

[bjorn3]

Please dont do this as this would make it very hard to update holyjit for the latest nightly. Currently it just requires a rustc patch of a few lines.

[eddyb]

@bjorn3 See this PR's description for the appropriate course of action. Being able to replace the provider for, e.g., the optimized_mir query, and then reusing the macro from rustc_mir, with a slightly modified set of passes, should allow pretty much everything.
There are no composition rules for MIR passes, nor is the idea of a MIR pass permanent, so it's not really meaningful to "just add another pass".

[bjorn3]

I see. Should have read the description completely.

[nbp]

@bjorn3 Thanks for your concern for HolyJit. Yes this patch is going to break the ability to simply rebase a patch on top of rustc, but HolyJit is a prototype, and I have been warned and explicitly been suggested against using a plugin approach from the beginning.

I still went with the plugin approach because this is something I understand and which was close enough to what is currently documented for making syntax plugins.

[bors]

☔ The latest upstream changes (presumably #45909) made this pull request unmergeable. Please resolve the merge conflicts.

[eddyb]

@bors r=nikomatsakis

[bors]

📌 Commit d6aa56f has been approved by nikomatsakis

[bors]

⌛ Testing commit d6aa56f with merge 24840da...

[bors]

☀️ Test successful - status-appveyor, status-travis
Approved by: nikomatsakis
Pushing 24840da to master...