Don't run various MIR optimizations at mir-opt-level=0 #70073
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@bors r+ |
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📌 Commit d158587eb76428d060bb08170813e8b9ada881aa has been approved by |
bjorn3
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@bors r- |
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src/librustc_mir/transform/mod.rs
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| // Deaggregation isn't technically an optimization but it unlocks opportunities | ||
| // for later optimization passes. | ||
| &deaggregator::Deaggregator, |
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But then why is it not run earlier?
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I don't know but I think the only passes that would be affected by this are CopyPropagation and SimplifyLocals which both run after this one.
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@eddyb said "people just probably didn't care much about it and added passes before and after".
So I'd vote for moving it up to the other lowering passes.
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I recall someone mentioning that drop elaboration relies on aggregates still being intact, and the generator transform performs drop elaboration. Not very sure though.
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@wesleywiser you have conflicts to resolve |
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I can resolve them but we're really waiting on some feedback from @oli-obk 🙂 |
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@bors retry |
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⌛ Testing commit f4dfb99 with merge fadd2a48ae5148f9181745a3956dee1523d291c5... |
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💔 Test failed - checks-azure |
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☀️ Test successful - checks-azure |
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…chievink smoke-test for async fn with mir-opt-level=0 MIR opt levels heavily influence which MIR transformations run, and we barely test non-default opt levels. I am particularly worried about `async fn` lowering and how it might (not) work when the set of preceding MIR passes changes -- see rust-lang#70073. This adds some basic smoke testing, where at least a few `async fn` `run-pass` test are ensured to also work with mir-opt-level=0.
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…leywiser move Deaggregate pass to post_borrowck_cleanup Reopen of rust-lang#71946 Only the second commit is from this PR, the other commit is a bugfix that's in the process of getting merged. I'll rebase once that's done In rust-lang#70073 MIR pass handling got reorganized, but with the goal of not changing behavior (except for disabling some optimizations on opt-level = 0). But there we realized that the Deaggregator pass, while conceptually more of a "cleanup" pass (and one that should be run before optimizations), was run in the middle of the optimization chain. Likely this is an accident of history, so I suggest we try and clean that up by making it a proper cleanup pass. This does change mir-opt output, because deaggregation now runs before const-prop instead of after. r? @wesleywiser @rust-lang/wg-mir-opt cc @RalfJung
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Add missing checks for mir-opt-level to non-essential MIR passes.
I verified that this can still bootstrap even with these passes disabled.
r? @oli-obk cc @RalfJung