dropck_outlives check whether generator witness needs_drop #117134

lcnr · 2023-10-24T17:19:25Z

see https://rust-lang.zulipchat.com/#narrow/stream/326866-t-types.2Fnominated/topic/.23116242.3A.20Code.20no.20longer.20compiles.20after.20-Zdrop-tracking-mir.20.E2.80.A6/near/398311627 for an explanation.

Fixes #116242 (or well, the repro by @jamuraa in #116242 (comment)). I did not add a regression test as it depends on other crates. We do have 1 test going from fail to pass, showing the intended behavior.

r? types

lcnr · 2023-10-24T17:26:30Z

@bors try

bors · 2023-10-24T17:27:39Z

⌛ Trying commit 2ca4c7e with merge 2cf1c2a...

dropck_outlives check whether generator witness needs_drop see https://rust-lang.zulipchat.com/#narrow/stream/326866-t-types.2Fnominated/topic/.23116242.3A.20Code.20no.20longer.20compiles.20after.20-Zdrop-tracking-mir.20.E2.80.A6/near/398311627 for an explanation. Fixes rust-lang#116242 (or well, the repro by `@jamuraa` in rust-lang#116242 (comment)). I did not add a regression test as it depends on other crates. We do have 1 test going from fail to pass, showing the intended behavior. r? types

lcnr · 2023-10-24T17:27:55Z

compiler/rustc_ty_utils/src/needs_drop.rs

+                    // need to be dropped, and only require the captured types to be live
+                    // if they do.
+                    ty::Coroutine(_, args, _) => {
+                        if self.reveal_coroutine_witnesses {


this is necessary to handle nested futures 🤔 should potentially add a test for it, but I don't feel motivated enough to do so 😅

lcnr · 2023-10-24T17:29:13Z

want to run both crater and perf. Worried that I messed up and we get some weird cycles because of this, I am fairly confident that this is alright.

bors · 2023-10-24T18:49:54Z

☀️ Try build successful - checks-actions
Build commit: 2cf1c2a (2cf1c2a614d6ae3bd50a8df20aeac2f9eceeea87)

cjgillot · 2023-10-25T17:51:00Z

Thanks for figuring this out @lcnr!

lcnr · 2023-10-26T07:38:02Z

@rust-timer queue

@craterbot check

craterbot · 2023-10-26T07:38:08Z

👌 Experiment pr-117134 created and queued.
🤖 Automatically detected try build 2cf1c2a
🔍 You can check out the queue and this experiment's details.

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

lcnr · 2023-10-26T07:49:38Z

assuming that the crater run and perf is acceptable, and to make sure we backport in time:

To quickly summarize again: the change from this PR is in bold

dropping a coroutine witness drops the values stored in its state machine: the content of its CoroutineWitness
computing the CoroutineWitness relies on mir_built
mir_built relies on fn needs_drop, we conservatively assume that all generators have to be dropped
we do not know the exact lifetimes of the values stored in the witness (as they may be self-referential), so for a coroutine to be drop live during mir_borrowck we require anything that could theoretically be accessed by the coroutine to be live.
however, during mir_borrowck we can access the CoroutineWitness, so we only require everything to be live if the coroutine actually contains any field which requires drop. This recursively looks into nested coroutines.

I believe that this does not result in query cycles as the only way needs_drop can access nested coroutines if they are from the same body. Coroutines from other bodies are hidden by an opaque type, which we should not be able to reveal.

@rfcbot fcp merge

rfcbot · 2023-10-26T07:49:39Z

Team member @lcnr has proposed to merge this. The next step is review by the rest of the tagged team members:

No concerns currently listed.

Once a majority of reviewers approve (and at most 2 approvals are outstanding), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up!

See this document for info about what commands tagged team members can give me.

lcnr · 2023-10-26T07:50:44Z

@craterbot p=1

craterbot · 2023-10-26T07:50:46Z

📝 Configuration of the pr-117134 experiment changed.

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

lqd · 2023-10-26T08:12:28Z

@rust-timer build 2cf1c2a

lcnr · 2023-11-02T20:29:55Z

@bors r=compiler-errors

bors · 2023-11-02T20:29:58Z

📌 Commit dda5e32 has been approved by compiler-errors

It is now in the queue for this repository.

bors · 2023-11-02T22:03:41Z

⌛ Testing commit dda5e32 with merge a2f5f96...

bors · 2023-11-03T00:01:37Z

☀️ Test successful - checks-actions
Approved by: compiler-errors
Pushing a2f5f96 to master...

rust-timer · 2023-11-03T02:09:13Z

Finished benchmarking commit (a2f5f96): comparison URL.

Overall result: ❌ regressions - ACTION NEEDED

Next Steps: If you can justify the regressions found in this perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please open an issue or create a new PR that fixes the regressions, add a comment linking to the newly created issue or PR, and then add the perf-regression-triaged label to this PR.

@rustbot label: +perf-regression
cc @rust-lang/wg-compiler-performance

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	0.3%	[0.2%, 0.3%]	5
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.3%	[0.2%, 0.3%]	5

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	5.8%	[5.8%, 5.8%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.9%	[-2.9%, -2.9%]	1
All ❌✅ (primary)	5.8%	[5.8%, 5.8%]	1

Cycles

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-1.1%	[-1.1%, -1.1%]	1
All ❌✅ (primary)	-	-	0

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 636.864s -> 635.107s (-0.28%)
Artifact size: 304.51 MiB -> 304.48 MiB (-0.01%)

82: Automated pull from upstream `master` r=tshepang a=github-actions[bot] This PR pulls the following changes from the upstream repository: * rust-lang/rust#117313 * rust-lang/rust#117131 * rust-lang/rust#117134 * rust-lang/rust#117471 * rust-lang/rust#117521 * rust-lang/rust#117513 * rust-lang/rust#117512 * rust-lang/rust#117509 * rust-lang/rust#117495 * rust-lang/rust#117394 * rust-lang/rust#117466 * rust-lang/rust#117204 * rust-lang/rust#117386 * rust-lang/rust#117506 Co-authored-by: Nicholas Nethercote <n.nethercote@gmail.com> Co-authored-by: roblabla <unfiltered@roblab.la> Co-authored-by: Michael Goulet <michael@errs.io> Co-authored-by: massivebird <gdrakemail@gmail.com> Co-authored-by: bors <bors@rust-lang.org> Co-authored-by: Zalathar <Zalathar@users.noreply.github.com> Co-authored-by: lcnr <rust@lcnr.de> Co-authored-by: Joshua Liebow-Feeser <joshlf@users.noreply.github.com> Co-authored-by: Matthias Krüger <matthias.krueger@famsik.de>

pnkfelix · 2023-11-07T16:14:53Z

regressed ripgrep check for incr-patched:println (0.35%), incr-full (0.26%), and full (0.21%); regressed regex check for incr-patched:Job (0.29%) and incr-patched:println (0.24%).
this is easily justified; it is fixing a code-acceptance regression
marking as triaged

@rustbot label: +perf-regression-triaged

wesleywiser · 2023-11-08T16:11:05Z

Accepting for beta backport as discussed during a previous compiler team triage meeting.

[beta] backports - dropck_outlives check whether generator witness needs_drop rust-lang#117134 - Make sure that predicates with unmentioned bound vars are still considered global in the old solver rust-lang#117589 - Check binders with bound vars for global bounds that don't hold rust-lang#117637 - generator layout: ignore fake borrows rust-lang#117712 r? ghost

rustbot assigned compiler-errors Oct 24, 2023

lcnr added the beta-nominated Nominated for backporting to the compiler in the beta channel. label Oct 24, 2023

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Oct 24, 2023

lcnr force-pushed the dropck_outlives-coroutine branch from cb8123f to 063cca2 Compare October 24, 2023 17:24

lcnr added the T-types Relevant to the types team, which will review and decide on the PR/issue. label Oct 24, 2023

lcnr force-pushed the dropck_outlives-coroutine branch from 063cca2 to 2ca4c7e Compare October 24, 2023 17:26

lcnr commented Oct 24, 2023

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rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Oct 26, 2023

craterbot added S-waiting-on-crater Status: Waiting on a crater run to be completed. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. S-waiting-on-perf Status: Waiting on a perf run to be completed. labels Oct 26, 2023

lcnr removed the T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. label Oct 26, 2023

rfcbot added proposed-final-comment-period Proposed to merge/close by relevant subteam, see T-<team> label. Will enter FCP once signed off. disposition-merge This issue / PR is in PFCP or FCP with a disposition to merge it. labels Oct 26, 2023

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review + add tests

dda5e32

lcnr force-pushed the dropck_outlives-coroutine branch from 41a674e to dda5e32 Compare November 2, 2023 17:16

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Nov 2, 2023

bors added the merged-by-bors This PR was explicitly merged by bors. label Nov 3, 2023

bors merged commit a2f5f96 into rust-lang:master Nov 3, 2023
11 checks passed

rustbot added this to the 1.75.0 milestone Nov 3, 2023

github-actions bot mentioned this pull request Nov 3, 2023

Automated pull from upstream master ferrocene/ferrocene#82

Merged

lcnr added the T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. label Nov 3, 2023

lcnr deleted the dropck_outlives-coroutine branch November 3, 2023 09:28

rustbot added the perf-regression-triaged The performance regression has been triaged. label Nov 7, 2023

wesleywiser added the beta-accepted Accepted for backporting to the compiler in the beta channel. label Nov 8, 2023

cuviper mentioned this pull request Nov 9, 2023

[beta] backports #117764

Merged

cuviper modified the milestones: 1.75.0, 1.74.0 Nov 9, 2023

cuviper removed the beta-nominated Nominated for backporting to the compiler in the beta channel. label Nov 9, 2023

rfcbot added finished-final-comment-period The final comment period is finished for this PR / Issue. to-announce Announce this issue on triage meeting and removed final-comment-period In the final comment period and will be merged soon unless new substantive objections are raised. labels Nov 9, 2023

apiraino removed the to-announce Announce this issue on triage meeting label Dec 14, 2023

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dropck_outlives check whether generator witness needs_drop #117134

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dropck_outlives check whether generator witness needs_drop #117134

dropck_outlives check whether generator witness needs_drop #117134

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Overall result: ❌ regressions - ACTION NEEDED

Instruction count

Max RSS (memory usage)

Cycles

Binary size

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