[DO NOT MERGE] next-solver perf test by lcnr · Pull Request #164198 · rust-lang/rust

lcnr · 2026-10-12T09:21:05Z

r? ghost

The rust-analyzer impls of these methods will need to be removed on the next sync.

It's faster than `extend` to initialize these structures.

A lot of work can be skipped if the two values being related are equal. (There are various early-return equality checks like this further down the call chain, this just adds one earlier.)

The former has an early return check and a single call site, so the check can be moved before the call site. Also, in the `Err(NoSolution)` case we can skip the `CandidateHeadUsages::default()` stuff because that's just an empty list and `merge_usages` is a no-op.

Instead of getting it within `fast_reject_assumption`. `fast_reject_assumption` has three call sites. For two of them this change doesn't help perf, but the third call occurs in a loop, and this lets us get the goal lang item once per loop instead of once per loop element.

- Increase the number of preinterned type vars and anon bound types. - Preintern some root-universe placeholder types with anon bounds. - Adjust some comments. - Also rename a lot of the preinterning names for more consistency.

lcnr · 2026-10-12T09:21:13Z

@bors try @rust-timer queue

[DO NOT MERGE] next-solver perf test

rust-log-analyzer · 2026-10-12T09:28:45Z

The job test-tidy failed! Check out the build log: (web) (plain enhanced) (plain)

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

tidy check
x.py completions check
tidy [rustdoc_json (src)]: `rustdoc-json-types` modified, checking format version
tidy: Skipping binary file check, read-only filesystem
tidy [style (tests)]: /checkout/tests/ui/traits/next-solver/assembly/ambiguity-due-to-uniquification-unsoundness.rs: missing trailing newline
tidy [style (tests)]: FAIL
removing old virtual environment
creating virtual environment at '/checkout/obj/build/venv' using 'python3.12' and 'venv'
Requirement already satisfied: pip in ./build/venv/lib/python3.12/site-packages (24.0)
Collecting pip
  Downloading pip-26.2.1-py3-none-any.whl.metadata (4.6 kB)
---
typechecking javascript files
tidy: The following check failed: style (tests)
Bootstrap failed while executing `test src/tools/tidy tidyselftest --extra-checks=py,cpp,js,spellcheck`
Currently active steps:
test::Tidy {  } at src/bootstrap/src/core/build_steps/test.rs:1743
Command `/checkout/obj/build/x86_64-unknown-linux-gnu/stage1-tools-bin/rust-tidy --root-path=/checkout --cargo-path=/checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/cargo --output-dir=/checkout/obj/build --concurrency=4 --npm-path=/node/bin/yarn --ci=true --extra-checks=py,cpp,js,spellcheck` failed with exit code 1
Created at: src/bootstrap/src/core/build_steps/tool.rs:1627:23
Executed at: src/bootstrap/src/core/build_steps/test.rs:1828:24

Command has failed. Rerun with -v to see more details.
Build completed unsuccessfully in 0:02:00
  local time: Mon Oct 12 09:28:33 UTC 2026
  network time: Mon, 12 Oct 2026 09:28:33 GMT
##[error]Process completed with exit code 1.
##[group]Run echo "disk usage:"

rust-bors · 2026-10-12T10:24:48Z

☀️ Try build successful (CI)
Build commit: f1494a8 (f1494a8d7038ea0295a71f4a3805766b8f0b561a)
Base parent: b542750 (b5427502dab50cb27d9327d2893ddf2337dd4388)

rust-timer · 2026-10-12T11:13:02Z

Finished benchmarking commit (f1494a8): comparison URL.

Overall result: ❌✅ regressions and improvements - please read:

Benchmarking means the PR may be perf-sensitive. It's automatically marked not fit for rolling up. Overriding is possible but disadvised: it risks changing compiler perf.

Next, please: If you can, justify the regressions found in this try perf run in writing along with @rustbot label: +perf-regression-triaged. If not, fix the regressions and do another perf run. Neutral or positive results will clear the label automatically.

@bors rollup=never rustc-perf
@rustbot label: -S-waiting-on-perf +perf-regression

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	10.0%	[0.1%, 196.8%]	272
Regressions ❌ (secondary)	8.1%	[0.1%, 90.0%]	234
Improvements ✅ (primary)	-6.9%	[-29.7%, -0.2%]	31
Improvements ✅ (secondary)	-9.8%	[-79.3%, -0.2%]	70
All ❌✅ (primary)	8.2%	[-29.7%, 196.8%]	303

Max RSS (memory usage)

Results (primary 6.0%, secondary 2.4%)

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

	mean	range	count
Regressions ❌ (primary)	6.0%	[0.9%, 28.6%]	196
Regressions ❌ (secondary)	4.3%	[0.8%, 11.2%]	49
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-4.0%	[-6.5%, -1.1%]	14
All ❌✅ (primary)	6.0%	[0.9%, 28.6%]	196

Cycles

Results (primary 10.3%, secondary 4.7%)

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

	mean	range	count
Regressions ❌ (primary)	11.9%	[1.9%, 147.3%]	202
Regressions ❌ (secondary)	11.0%	[2.0%, 52.8%]	119
Improvements ✅ (primary)	-6.9%	[-20.3%, -2.0%]	19
Improvements ✅ (secondary)	-18.7%	[-77.5%, -1.9%]	32
All ❌✅ (primary)	10.3%	[-20.3%, 147.3%]	221

Binary size

This perf run didn't have relevant results for this metric.

Bootstrap: 490.336s -> 488.342s (-0.41%)
Artifact size: 406.60 MiB -> 402.57 MiB (-0.99%)

rust-bors · 2026-10-12T19:48:32Z

☔ The latest upstream changes (presumably #164216) made this pull request unmergeable. Please resolve the merge conflicts by rebasing.

lcnr and others added 11 commits October 12, 2026 11:15

enable -Znext-solver by default

582b01c

do not prefer trivially true candidates

c8db3ab

don't just ignore ambig goals in MIR borrowck

90a0f60

add regression test for old solver unsoundness

00b6019

Remove some unused Interner trait methods

0901176

The rust-analyzer impls of these methods will need to be removed on the next sync.

Use clone_from in canonicalize_param_env

85e70e6

It's faster than `extend` to initialize these structures.

Add early return to unify_query_var_values

9d5cab1

A lot of work can be skipped if the two values being related are equal. (There are various early-return equality checks like this further down the call chain, this just adds one earlier.)

Preintern more types

484375f

- Increase the number of preinterned type vars and anon bound types. - Preintern some root-universe placeholder types with anon bounds. - Adjust some comments. - Also rename a lot of the preinterning names for more consistency.

cool

63ff57c

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rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Oct 12, 2026

rust-bors Bot pushed a commit that referenced this pull request Oct 12, 2026

Auto merge of #164198 - lcnr:perf-test-next, r=<try>

f1494a8

[DO NOT MERGE] next-solver perf test

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rustbot added perf-regression Performance regression. and removed S-waiting-on-perf Status: Waiting on a perf run to be completed. labels Oct 12, 2026

lcnr closed this Oct 13, 2026

rustbot removed the S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. label Oct 13, 2026

lcnr mentioned this pull request Oct 13, 2026

stabilize -Znext-solver=globally #164209

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[DO NOT MERGE] next-solver perf test - #164198

[DO NOT MERGE] next-solver perf test#164198
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rust-timer commented Oct 12, 2026

Overall result: ❌✅ regressions and improvements - please read:

Instruction count

Max RSS (memory usage)

Cycles

Binary size

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rust-bors Bot commented Oct 12, 2026

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