Add more tests for the parallel rustc #145384

ywxt · 2025-08-14T07:31:47Z

At the moment, the parallel frontend test cases are severely lacking. Althought some reported issues have been resolved, they haven't been added into the tests.

This PR arranges the resolved ICE issues and adds tests for them.

Whether it is worthwhile to add a separate test suite for the paralel frontend still requires futher discussion. But we are trying coveraging issues being resolved through capability of the existing UI test suite.

Discussion: Zulip

Related issues:

ice: no index for a field #120760
ICE: 'only variances_of returns &[ty::Variance]' #124423 fixed by Use search_for_cycle_permutation to look for variances_of #140358
ICE: only 'variances_of' returns '&[ty::Variance]' #127971 fxied by Use search_for_cycle_permutation to look for variances_of #140358
ice: Unexpected type for constructor #120601 fixed by Avoid follow-up errors and ICEs after missing lifetime errors on data structures #127311

cc @jieyouxu

rustbot · 2025-08-14T07:31:51Z

r? @davidtwco

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rustbot · 2025-08-14T07:31:55Z

Some changes occurred in src/tools/compiletest

cc @jieyouxu

davidtwco

It would be nice if the tests could have slightly more descriptive names, though I appreciate that might be tricky.

src/tools/compiletest/src/runtest.rs

davidtwco · 2025-08-14T13:08:49Z

src/tools/compiletest/src/runtest.rs

@@ -2749,7 +2749,7 @@ impl<'test> TestCx<'test> {
        // Wrapper tools set by `runner` might provide extra output on failure,
        // for example a WebAssembly runtime might print the stack trace of an
        // `unreachable` instruction by default.
-        let compare_output_by_lines = self.config.runner.is_some();
+        let compare_output_by_lines = self.props.parallel_front_end || self.config.runner.is_some();


If this is the only thing that parallel_front_end enables, maybe exposing //@ compare-output-by-lines would be better?

I think that might be better, it's more direct in telling the test reader what the behavior is.

jieyouxu

Thanks. Some nits

jieyouxu · 2025-08-14T13:08:21Z

src/tools/compiletest/src/runtest.rs

@@ -2749,7 +2749,7 @@ impl<'test> TestCx<'test> {
        // Wrapper tools set by `runner` might provide extra output on failure,
        // for example a WebAssembly runtime might print the stack trace of an
        // `unreachable` instruction by default.
-        let compare_output_by_lines = self.config.runner.is_some();
+        let compare_output_by_lines = self.props.parallel_front_end || self.config.runner.is_some();


Problem: please document this directive and what it does in rustc-dev-guide.

tests/ui/parallel-rustc/cycle_crash.rs

jieyouxu · 2025-08-14T13:15:22Z

src/tools/compiletest/src/runtest.rs

@@ -2749,7 +2749,7 @@ impl<'test> TestCx<'test> {
        // Wrapper tools set by `runner` might provide extra output on failure,
        // for example a WebAssembly runtime might print the stack trace of an
        // `unreachable` instruction by default.
-        let compare_output_by_lines = self.config.runner.is_some();
+        let compare_output_by_lines = self.props.parallel_front_end || self.config.runner.is_some();


Remark: note that this has two potential issues:

This can mask genuine bugs, where a symptom may be diagnostics reordering.

The parallel front-end tests are still potential flaky.

I don't love (2) too much, but I recognize the pragmatic need for having some test coverage, so I don't want to block this.

My reservation is primarily that these tests can potentially fail someone else's PR, or a rollup, and can be rather confusing.

tests/ui/parallel-rustc/ty-variance-issue-127971.rs

tests/ui/parallel-rustc/undefined-function-issue-120760.rs

jieyouxu · 2025-08-14T13:19:41Z

tests/ui/parallel-rustc/undefined-function-issue-120760.rs

Remark: this is one of those that we do not know if it was genuinely fixed.

Should I remove it ?

let's keep it for now, will need to disable it if it's not actually fixed

tests/ui/parallel-rustc/unexpected-type-issue-120601.rs

davidtwco · 2025-08-14T15:08:31Z

Will re-assign to @jieyouxu, feel free to r=davidtwco,jieyouxu when you're happy with these changes

r? @jieyouxu

jieyouxu · 2025-08-14T15:11:58Z

@rustbot author

rustbot · 2025-08-14T15:12:03Z

Reminder, once the PR becomes ready for a review, use @rustbot ready.

rustbot · 2025-08-15T06:05:58Z

The rustc-dev-guide subtree was changed. If this PR only touches the dev guide consider submitting a PR directly to rust-lang/rustc-dev-guide otherwise thank you for updating the dev guide with your changes.

cc @BoxyUwU, @jieyouxu, @Kobzol, @tshepang

ywxt · 2025-08-15T07:21:18Z

@rustbot ready

jieyouxu

Thanks

jieyouxu · 2025-08-21T08:36:24Z

The queue was particularly backed up this week (partly due to outages and bors troubles), but this PR is in reasonably close position to tip of queue.

Add more tests for the parallel rustc At the moment, the parallel frontend test cases are severely lacking. Althought some reported issues have been resolved, they haven't been added into the tests. This PR arranges the resolved ICE issues and adds tests for them. Whether it is worthwhile to add a separate test suite for the paralel frontend still requires futher discussion. But we are trying coveraging issues being resolved through capability of the existing UI test suite. Discussion: [Zulip](https://rust-lang.zulipchat.com/#narrow/channel/233931-t-compiler.2Fmajor-changes/topic/Proposal.20for.20a.20dedicated.20test.20suite.20for.20t.E2.80.A6.20compiler-team.23906) Related issues: - #120760 - #124423 fixed by #140358 - #127971 fxied by #140358 - #120601 fixed by #127311 cc `@jieyouxu`

bors · 2025-08-21T16:44:35Z

⌛ Testing commit 36ab1bf with merge 4cd914a...

bors · 2025-08-21T19:49:39Z

💔 Test failed - checks-actions

ywxt · 2025-08-22T01:06:01Z

Do the machines get offline?

jieyouxu · 2025-08-22T01:07:34Z

GitHub Actions had an incident last night (a different one), https://www.githubstatus.com/incidents/c7kq3ctclddp

@bors retry

Add more tests for the parallel rustc At the moment, the parallel frontend test cases are severely lacking. Althought some reported issues have been resolved, they haven't been added into the tests. This PR arranges the resolved ICE issues and adds tests for them. Whether it is worthwhile to add a separate test suite for the paralel frontend still requires futher discussion. But we are trying coveraging issues being resolved through capability of the existing UI test suite. Discussion: [Zulip](https://rust-lang.zulipchat.com/#narrow/channel/233931-t-compiler.2Fmajor-changes/topic/Proposal.20for.20a.20dedicated.20test.20suite.20for.20t.E2.80.A6.20compiler-team.23906) Related issues: - #120760 - #124423 fixed by #140358 - #127971 fxied by #140358 - #120601 fixed by #127311 cc `@jieyouxu`

bors · 2025-08-22T02:06:35Z

⌛ Testing commit 36ab1bf with merge bdc19a9...

rust-log-analyzer · 2025-08-22T04:03:24Z

The job x86_64-gnu-aux failed! Check out the build log: (web) (plain enhanced) (plain)

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

bors · 2025-08-22T04:04:17Z

💔 Test failed - checks-actions

ywxt · 2025-08-22T08:06:15Z

failed in library/std/src/thread/mod.rs , I guess this is unrelated to this PR?

jieyouxu · 2025-08-24T10:57:38Z

Yeah, however that test failing is a bit suspicious, I'll open an issue to track it.

jieyouxu · 2025-08-24T11:01:56Z

@bors retry

bors · 2025-08-24T11:13:18Z

⌛ Testing commit 36ab1bf with merge 41a79f1...

bors · 2025-08-24T14:29:20Z

☀️ Test successful - checks-actions
Approved by: jieyouxu
Pushing 41a79f1 to master...

github-actions · 2025-08-24T14:32:32Z

What is this?

This is an experimental post-merge analysis report that shows differences in test outcomes between the merged PR and its parent PR.

Comparing 93edf9f (parent) -> 41a79f1 (this PR)

Test differences

Show 14 test diffs

Stage 1

[ui] tests/ui/parallel-rustc/cycle_crash-issue-135870.rs: [missing] -> pass (J1)
[ui] tests/ui/parallel-rustc/cycle_crash.rs: pass -> [missing] (J1)
[ui] tests/ui/parallel-rustc/ty-variance-issue-124423.rs: [missing] -> pass (J1)
[ui] tests/ui/parallel-rustc/ty-variance-issue-127971.rs: [missing] -> pass (J1)
[ui] tests/ui/parallel-rustc/undefined-function-issue-120760.rs: [missing] -> pass (J1)
[ui] tests/ui/parallel-rustc/unexpected-type-issue-120601.rs: [missing] -> pass (J1)

Stage 2

[ui] tests/ui/parallel-rustc/cycle_crash-issue-135870.rs: [missing] -> pass (J0)
[ui] tests/ui/parallel-rustc/cycle_crash.rs: pass -> [missing] (J0)
[ui] tests/ui/parallel-rustc/ty-variance-issue-124423.rs: [missing] -> pass (J0)
[ui] tests/ui/parallel-rustc/ty-variance-issue-127971.rs: [missing] -> pass (J0)
[ui] tests/ui/parallel-rustc/undefined-function-issue-120760.rs: [missing] -> pass (J0)
[ui] tests/ui/parallel-rustc/unexpected-type-issue-120601.rs: [missing] -> pass (J0)

Additionally, 2 doctest diffs were found. These are ignored, as they are noisy.

Job group index

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard 41a79f1862aa6b81bac674598e275e80e9f09eb9 --output-dir test-dashboard

And then open test-dashboard/index.html in your browser to see an overview of all executed tests.

Job duration changes

dist-apple-various: 4043.7s -> 5897.5s (45.8%)
dist-x86_64-apple: 6896.8s -> 8097.7s (17.4%)
pr-check-1: 1612.4s -> 1353.1s (-16.1%)
i686-gnu-2: 6348.7s -> 5492.5s (-13.5%)
x86_64-gnu-llvm-19: 2800.5s -> 2425.1s (-13.4%)
dist-loongarch64-linux: 6244.5s -> 7049.7s (12.9%)
x86_64-gnu-stable: 7649.4s -> 6815.5s (-10.9%)
x86_64-rust-for-linux: 2855.4s -> 2575.5s (-9.8%)
i686-gnu-nopt-1: 8190.2s -> 7404.0s (-9.6%)
x86_64-gnu-miri: 5090.9s -> 4628.2s (-9.1%)

How to interpret the job duration changes?

Job durations can vary a lot, based on the actual runner instance
that executed the job, system noise, invalidated caches, etc. The table above is provided
mostly for t-infra members, for simpler debugging of potential CI slow-downs.

rust-timer · 2025-08-24T15:38:34Z

Finished benchmarking commit (41a79f1): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

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

Max RSS (memory usage)

Results (primary -5.5%, secondary -3.2%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-5.5%	[-5.5%, -5.5%]	1
Improvements ✅ (secondary)	-3.2%	[-3.2%, -3.2%]	1
All ❌✅ (primary)	-5.5%	[-5.5%, -5.5%]	1

Cycles

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

Binary size

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

Bootstrap: 468.299s -> 468.201s (-0.02%)
Artifact size: 378.33 MiB -> 378.32 MiB (-0.00%)

rustbot assigned davidtwco Aug 14, 2025

davidtwco reviewed Aug 14, 2025

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src/tools/compiletest/src/runtest.rs Outdated Show resolved Hide resolved

ywxt force-pushed the parallel-tests branch from 99d7555 to 4c49822 Compare August 14, 2025 10:33

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jieyouxu requested changes Aug 14, 2025

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rustbot assigned jieyouxu and unassigned davidtwco Aug 14, 2025

rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Aug 14, 2025

ywxt force-pushed the parallel-tests branch from 4c49822 to 02c764a Compare August 15, 2025 06:05

rustbot added the A-rustc-dev-guide Area: rustc-dev-guide label Aug 15, 2025

ywxt force-pushed the parallel-tests branch from 02c764a to 28962e3 Compare August 15, 2025 06:12

ywxt added 2 commits August 15, 2025 14:16

Add the directive compare-output-by-lines

e17989e

Add more tests

36ab1bf

ywxt force-pushed the parallel-tests branch from 28962e3 to 36ab1bf Compare August 15, 2025 06:17

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Aug 15, 2025

jieyouxu approved these changes Aug 15, 2025

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bors added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Aug 21, 2025

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 Aug 22, 2025

bors added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Aug 22, 2025

jieyouxu mentioned this pull request Aug 24, 2025

std thread::Thread::unpark test deadlocked when run under miri #145816

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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 Aug 24, 2025

bors added the merged-by-bors This PR was explicitly merged by bors. label Aug 24, 2025

bors merged commit 41a79f1 into rust-lang:master Aug 24, 2025
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rustbot added this to the 1.91.0 milestone Aug 24, 2025

bors mentioned this pull request Aug 24, 2025

[EXPERIMENT] Introduce TypingMode::Codegen to avoid layout cycles #145477

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Add more tests for the parallel rustc #145384

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