Move fast paths around to gain a bit of new-solver perf by jdonszelmann · Pull Request #158249 · rust-lang/rust

jdonszelmann · 2026-06-22T13:38:31Z

Change in % compared to previous commit on 4 benchmarks. All measured locally on ragdoll (AMD RYZEN 3990X, x86_64). These benchmarks have been quite repeatable in the past, but don't exactly match perf runs. All benchmarks show change in instruction count
First change is compared to baseline
Commit ids may change on rebases, so these links may become outdated.

	nalgebra [check,debug,opt]	serde [check,debug, opt]	syn [check, debug, opt]	wg-grammar [check, debug, opt]
move overflow check	$${\color{green}-0.04\%}$$ $${\color{green}-0.03\%}$$ $${\color{green}-0.02\%}$$	$${\color{green}-0.15\%}$$ $${\color{green}-0.12\%}$$ $${\color{green}-0.11\%}$$	$${\color{green}-0.08\%}$$ $${\color{green}-0.04\%}$$ $${\color{green}-0.01\%}$$	$${\color{green}-0.32\%}$$ $${\color{green}-0.31\%}$$ $${\color{green}-0.29\%}$$
move fast path into evaluate_goal	$${\color{red}+0.61\%}$$ $${\color{red}+0.60\%}$$ $${\color{red}+0.43\%}$$	$${\color{red}+0.75\%}$$ $${\color{red}+0.69\%}$$ $${\color{red}+0.65\%}$$	$${\color{red}+0.55\%}$$ $${\color{red}+0.36\%}$$ $${\color{red}+0.14\%}$$	$${\color{red}+0.13\%}$$ $${\color{red}+0.21\%}$$ $${\color{red}+0.15\%}$$
remove fastpath from fullfilment loop	$${\color{red}+0.56\%}$$ $${\color{red}+0.50\%}$$ $${\color{red}+0.35\%}$$	$${\color{red}+3.33\%}$$ $${\color{red}+2.76\%}$$ $${\color{red}+2.55\%}$$	$${\color{red}+1.65\%}$$ $${\color{red}+0.93\%}$$ $${\color{red}+0.33\%}$$	$${\color{green}-5.06\%}$$ $${\color{green}-5.00\%}$$ $${\color{green}-4.65\%}$$
return stalled info from fast path	$${\color{red}+0.16\%}$$ $${\color{red}+0.16\%}$$ $${\color{red}+0.12\%}$$	$${\color{red}+0.01\%}$$ $${\color{red}+0.01\%}$$ $${\color{red}+0.01\%}$$	$${\color{red}+0.24\%}$$ $${\color{red}+0.15\%}$$ $${\color{red}+0.05\%}$$	$${\color{green}-0.24\%}$$ $${\color{green}-0.24\%}$$ $${\color{green}-0.25\%}$$
move goal fast path into evaluate_goal_cold	$${\color{red}+0.01\%}$$ $${\color{red}+0.01\%}$$ $${\color{red}+0.01\%}$$	$${\color{red}+0.02\%}$$ $${\color{red}+0.02\%}$$ $${\color{red}+0.02\%}$$	$${\color{red}+0.02\%}$$ $${\color{red}+0.02\%}$$ $${\color{red}+0.01\%}$$	$${\color{green}-0.01\%}$$ $${\color{green}-0.01\%}$$ $${\color{green}-0.01\%}$$
shuffle fastpaths around to before creating an evalctxt	$${\color{green}-0.44\%}$$ $${\color{green}-0.41\%}$$ $${\color{green}-0.30\%}$$	$${\color{green}-2.31\%}$$ $${\color{green}-1.93\%}$$ $${\color{green}-1.80\%}$$	$${\color{green}-1.29\%}$$ $${\color{green}-0.77\%}$$ $${\color{green}-0.29\%}$$	$${\color{green}-6.06\%}$$ $${\color{green}-5.90\%}$$ $${\color{green}-5.48\%}$$
fast path when adding goals	$${\color{green}-0.62\%}$$ $${\color{green}-0.58\%}$$ $${\color{green}-0.41\%}$$	$${\color{green}-0.78\%}$$ $${\color{green}-0.66\%}$$ $${\color{green}-0.61\%}$$	$${\color{green}-0.36\%}$$ $${\color{green}-0.28\%}$$ $${\color{green}-0.10\%}$$	$${\color{green}-0.12\%}$$ $${\color{green}-0.09\%}$$ $${\color{green}-0.04\%}$$
overall from baseline	$${\color{red}+0.24\%}$$ $${\color{red}+0.23\%}$$ $${\color{red}+0.16\%}$$	$${\color{red}+0.79\%}$$ $${\color{red}+0.70\%}$$ $${\color{red}+0.66\%}$$	$${\color{red}+0.60\%}$$ $${\color{red}+0.36\%}$$ $${\color{red}+0.13\%}$$	$${\color{green}-11.31\%}$$ $${\color{green}-11.00\%}$$ $${\color{green}-10.27\%}$$

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jdonszelmann · 2026-06-22T13:44:06Z

This tests a bunch of changes together. I've done diffs locally suggesting ~5% speedup across these 7 commits. Moving fast path checks to evaluate_goal_raw ~2%, making it return stalled_on another 3% or so and using TyOrConstInferVar ~0.5%

@bors try @rust-timer queue

Move fast path checks to `evaluate_goal_raw`

rust-bors · 2026-06-22T16:02:47Z

☀️ Try build successful (CI)
Build commit: 3f4f44d (3f4f44d99c410d3aadeb2731ddd6c5446c89eb72)
Base parent: 9030e34 (9030e345fe92df1ccefd0a8cdf61a9a9a5b73cb0)

rust-timer · 2026-06-22T16:43:44Z

Finished benchmarking commit (3f4f44d): 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
@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)	-	-	0
Regressions ❌ (secondary)	1.1%	[0.1%, 3.7%]	18
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.9%	[-4.9%, -0.0%]	5
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (primary 0.6%, secondary 1.6%)

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

	mean	range	count
Regressions ❌ (primary)	2.7%	[2.7%, 2.7%]	1
Regressions ❌ (secondary)	2.2%	[1.7%, 2.7%]	9
Improvements ✅ (primary)	-1.4%	[-1.4%, -1.4%]	1
Improvements ✅ (secondary)	-1.2%	[-1.2%, -1.1%]	2
All ❌✅ (primary)	0.6%	[-1.4%, 2.7%]	2

Cycles

Results (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)	4.1%	[2.1%, 6.2%]	6
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.3%	[-2.3%, -2.3%]	1
All ❌✅ (primary)	-	-	0

Binary size

Results (primary 0.0%, secondary 0.1%)

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

	mean	range	count
Regressions ❌ (primary)	0.0%	[0.0%, 0.0%]	4
Regressions ❌ (secondary)	0.1%	[0.0%, 0.1%]	20
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.0%	[0.0%, 0.0%]	4

Bootstrap: 503.321s -> 505.38s (0.41%)
Artifact size: 353.40 MiB -> 353.04 MiB (-0.10%)

jdonszelmann · 2026-06-25T13:16:51Z

@bors try @rust-timer queue

Move fast path checks to `evaluate_goal_raw`

rust-bors · 2026-06-25T15:29:23Z

☀️ Try build successful (CI)
Build commit: b2fad67 (b2fad672d15ed85bb352e25461a99b01bf10a0de)
Base parent: 973ad0d (973ad0d0ab149bde2e96422833c1265c7a5be217)

rust-timer · 2026-06-25T21:22:01Z

Finished benchmarking commit (b2fad67): 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
@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)	-	-	0
Regressions ❌ (secondary)	0.6%	[0.2%, 1.2%]	12
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-6.9%	[-11.7%, -2.0%]	6
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (primary 4.0%, secondary 3.3%)

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

	mean	range	count
Regressions ❌ (primary)	4.0%	[3.4%, 4.7%]	2
Regressions ❌ (secondary)	4.8%	[0.9%, 22.7%]	7
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-1.6%	[-2.4%, -0.9%]	2
All ❌✅ (primary)	4.0%	[3.4%, 4.7%]	2

Cycles

Results (secondary -6.6%)

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)	-	-	0
Improvements ✅ (secondary)	-6.6%	[-8.2%, -2.1%]	4
All ❌✅ (primary)	-	-	0

Binary size

Results (secondary 0.0%)

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)	0.0%	[0.0%, 0.0%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Bootstrap: 509.16s -> 507.92s (-0.24%)
Artifact size: 353.81 MiB -> 353.75 MiB (-0.02%)

rustbot · 2026-07-16T09:03:54Z

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

lcnr

r=me after nits

View changes since this review

jdonszelmann · 2026-07-16T09:20:12Z

@bors r=lcnr rollup=never (perf)

rust-bors · 2026-07-16T09:20:15Z

📌 Commit a572787 has been approved by lcnr

It is now in the queue for this repository.

rust-bors · 2026-07-16T15:56:32Z

☀️ Test successful - CI
Approved by: lcnr
Duration: 3h 46m 23s
Pushing a6050b7 to main...

github-actions · 2026-07-16T15:59:58Z

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 d62fb1c (parent) -> a6050b7 (this PR)

Test differences

No test diffs found

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
test-dashboard a6050b7ea848e25289bf097c606e0611c58ef4f3 --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-aarch64-apple: 1h 20m -> 2h 9m (+61.3%)
x86_64-msvc-ext2: 1h 22m -> 1h 51m (+35.6%)
i686-gnu-nopt-2: 1h 42m -> 2h 19m (+35.2%)
dist-x86_64-llvm-mingw: 1h 27m -> 1h 57m (+34.8%)
x86_64-mingw-1: 2h 17m -> 3h 2m (+33.4%)
x86_64-gnu-debug: 1h 35m -> 2h 1m (+28.3%)
dist-powerpc-linux: 1h 11m -> 1h 30m (+25.9%)
i686-gnu-nopt-1: 2h 27m -> 1h 49m (-25.2%)
dist-x86_64-msvc: 2h 7m -> 1h 35m (-24.6%)
x86_64-gnu-llvm-21-2: 1h 41m -> 1h 17m (-24.2%)

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 · 2026-07-16T16:38:17Z

Finished benchmarking commit (a6050b7): comparison URL.

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

Our benchmarks found a performance regression caused by this PR.
This might be an actual regression, but it can also be just noise.

Next Steps:

If the regression was expected or you think it can be justified,
please write a comment with sufficient written justification, and add
@rustbot label: +perf-regression-triaged to it, to mark the regression as triaged.
If you think that you know of a way to resolve the regression, try to create
a new PR with a fix for the regression.
If you do not understand the regression or you think that it is just noise,
you can ask the @rust-lang/wg-compiler-performance working group for help (members of this group
were already notified of this PR).

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

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)	-	-	0
Regressions ❌ (secondary)	1.2%	[0.2%, 2.2%]	11
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-5.1%	[-8.4%, -1.5%]	6
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (secondary -1.9%)

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)	1.0%	[0.8%, 1.1%]	4
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-5.7%	[-9.0%, -3.1%]	3
All ❌✅ (primary)	-	-	0

Cycles

Results (secondary -1.8%)

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)	2.9%	[2.2%, 3.6%]	3
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-4.6%	[-6.6%, -2.3%]	5
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 489.85s -> 492.034s (0.45%)
Artifact size: 389.48 MiB -> 390.08 MiB (0.15%)

nnethercote · 2026-07-16T22:10:07Z

(Friendly suggestion for next time: don't put the big table of results in the PR description because it ends up in the merge commit message and looks ugly in git log output :)

Kobzol · 2026-07-21T07:37:08Z

Only affects the next trait solver. Some benchmarks regressed, but there are larger wins.

@rustbot label: +perf-regression-triaged

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rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Jun 22, 2026

rust-borsBot pushed a commit that referenced this pull request Jun 22, 2026
Auto merge of#158249- jdonszelmann:move-checks, r=<try>
3f4f44d
Move fast path checks to `evaluate_goal_raw`

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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 Jun 22, 2026

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Comment threadcompiler/rustc_infer/src/infer/context.rs Outdated

jdonszelmann force-pushed the move-checks branch 2 times, most recently from c340366 to 987b1a0Compare June 25, 2026 13:16

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rust-borsBot pushed a commit that referenced this pull request Jun 25, 2026
Auto merge of#158249- jdonszelmann:move-checks, r=<try>
b2fad67
Move fast path checks to `evaluate_goal_raw`

jdonszelmann force-pushed the move-checks branch from 987b1a0 to bfe02caCompare June 25, 2026 13:54

rustbot added A-tidy Area: The tidy tool T-bootstrap Relevant to the bootstrap subteam: Rust's build system (x.py and src/bootstrap) labels Jun 25, 2026

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fix bug when fast paths aren't rerun when opaques change
1cb6d00

jdonszelmann force-pushed the move-checks branch from 23b11ab to 1cb6d00Compare July 16, 2026 09:03

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Comment threadcompiler/rustc_trait_selection/src/solve/delegate.rs Outdated

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review comments (nits)
a572787

rust-borsBot 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 Jul 16, 2026

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rust-borsBot added merged-by-bors This PR was explicitly merged by bors. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Jul 16, 2026

rust-borsBot merged commit a6050b7 into rust-lang:mainJul 16, 2026
14 checks passed

rustbot added this to the 1.99.0 milestone Jul 16, 2026

rustbot added the perf-regression-triaged The performance regression has been triaged. label Jul 21, 2026

This was referenced Jul 25, 2026
perf: avoid re-running the trait-solver fast path on unchanged obligations rust-lang/rust-analyzer#22910
Closed
performance regression with -Znext-solver=globally #159933
Open

amirHdev mentioned this pull request Aug 19, 2026
Avoid redundant next-solver fulfillment scans #161348
Open

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

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

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Test differences

Job duration changes

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rust-timer commented Jul 16, 2026

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

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