Monomorphize in check mode to report (almost) all PMEs #107510
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@bors try @rust-timer queue |
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Awaiting bors try build completion. @rustbot label: +S-waiting-on-perf |
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⌛ Trying commit b99639861e05bb61a3235429a82a8c232233c751 with merge f792b4425823c469a96cdaff35d25590fe0e5970... |
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What's the "almost" about? |
codegen backends can still bail out if they don't support something (like some huge array size limits that are very target dependent) |
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We do check for "types can't be larger than 2^48" somewhere on the MIR level already -- so this is a separate check? Anyway, would be good to have a concrete example and an issue tracking that, but doesn't sound high priority to fix. |
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We have tests for
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And const-eval errors, I presume? |
those all get emitted in |
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☔ The latest upstream changes (presumably #100754) made this pull request unmergeable. Please resolve the merge conflicts. |
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I personally think whether optimised mir is used or for collection or not is orthogonal to whether instances are collected eagerly/lazily. Also, wouldn't this approach cause |
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cc @tmandry |
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Thanks for putting this up, I'm very curious to see the perf results! I think the use of PME here is slightly confusing – if I understand correctly we would still have errors that depend on which generic parameters are used, like the example in #104087 (comment). |
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@oli-obk another implementation strategy that we should consider here is adding a new field to Part of the reason that I bring this up is because I knew the topic of this issue was a possibility, but thought it was a non-issue specifically because I was under the impression that the |
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How is required_consts not already doing that?
The trouble is that we don't have required_fns so we might not transitively monomorphize functions even though they were mentioned by the user.
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Well, what I didn't realize was that required_consts only contains consts that are unevaluated by the time we do borrowck. What I thought happened is that all consts are put into there, specifically to ensure that things like this don't happen Edit: Oh, I realize what the confusion might have been. I was implicitly assuming that if we put a FnDef-typed constant into the list of constants, that we'd then go and actually mono that function (at least enough to go set off any PMEs) |
Ah -- no, all we do with that list is evaluate constants, we don't monomorphize any further functions. |
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If we want to make |
That's quite a big new feature that requires an RFC IMO. I don't think there is currently a plan to implement this. |
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Yeah, agreed. That kind of feature would also definitely need explicit Mir support |
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There's a lang team meeting that will touch on this PR next week (Feb 22). @oli-obk Do you think you could get it fixed up with a perf run by then? 🙏 |
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The |
I think we can avoid it. We only need to care about generic functions, and those have their MIR encoded no matter what |
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The job Click to see the possible cause of the failure (guessed by this bot) |
bjorn3
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| pub enum MonoItemCollectionMode { | ||
| Eager, | ||
| Eager { | ||
| /// Whether to use optimized mir for collection or just analyis MIR. |
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| /// Whether to use optimized mir for collection or just analyis MIR. | |
| /// Whether to use optimized mir for collection or just analysis MIR. |
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☔ The latest upstream changes (presumably #108872) made this pull request unmergeable. Please resolve the merge conflicts. |
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Closing this as it was an experiment |
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This never got far enough to get a perf result, did it? Would have been nice to get some numbers, though I think they'd be devastating.^^ |
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fixes #99682
see #104087 (comment) for discussion
r? @ghost