Port `#[cfg]` and `#[cfg_attr]` trace attributes to the new attribute parsers #150310

JonathanBrouwer · 2025-12-23T15:27:17Z

This PR converts cfg and cfg_trace attributes to the new parsed representation.

The primary challenge is that re-parsing these attributes in the HIR is a performance regression, since these attributes were only used in rustdoc and clippy parsing them in the HIR is extra work that was not done in the compiler before. To solve this, we only parse the attributes once and then store their parsed representation in the AST.

JonathanBrouwer · 2025-12-23T15:31:42Z

@bors try @rust-timer queue

Cfg trace attributes, attempt 2

rust-bors · 2025-12-23T17:49:18Z

☀️ Try build successful (CI)
Build commit: ed1fb29 (ed1fb2931c0b2ef01da69d775ed80af9ece506fe, parent: 0bd13c38df9a9a922bd8ec98ba7a8bc7e111860e)

rust-timer · 2025-12-23T18:30:32Z

Finished benchmarking commit (ed1fb29): comparison URL.

Overall result: ❌✅ regressions and improvements - please read the text below

Benchmarking this pull request means it may be perf-sensitive – we'll automatically label it not fit for rolling up. You can override this, but we strongly advise not to, due to possible changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please do so in sufficient writing along with @rustbot label: +perf-regression-triaged. If not, please fix the regressions and do another perf run. If its results are neutral or positive, the label will be automatically removed.

@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)	0.3%	[0.2%, 0.7%]	6
Regressions ❌ (secondary)	0.3%	[0.1%, 0.8%]	5
Improvements ✅ (primary)	-0.3%	[-0.5%, -0.1%]	15
Improvements ✅ (secondary)	-0.1%	[-0.2%, -0.0%]	15
All ❌✅ (primary)	-0.1%	[-0.5%, 0.7%]	21

Max RSS (memory usage)

Results (primary -0.9%, 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)	0.8%	[0.8%, 0.8%]	1
Regressions ❌ (secondary)	1.3%	[1.2%, 1.3%]	2
Improvements ✅ (primary)	-1.4%	[-2.4%, -0.9%]	3
Improvements ✅ (secondary)	-1.0%	[-1.2%, -0.8%]	3
All ❌✅ (primary)	-0.9%	[-2.4%, 0.8%]	4

Cycles

Results (primary 2.8%, secondary 10.9%)

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

	mean	range	count
Regressions ❌ (primary)	2.8%	[2.3%, 3.3%]	2
Regressions ❌ (secondary)	10.9%	[2.1%, 26.6%]	19
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	2.8%	[2.3%, 3.3%]	2

Binary size

Results (primary -0.4%, secondary -0.2%)

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)	-0.4%	[-1.9%, -0.0%]	78
Improvements ✅ (secondary)	-0.2%	[-0.9%, -0.0%]	16
All ❌✅ (primary)	-0.4%	[-1.9%, -0.0%]	78

Bootstrap: 481.073s -> 480.532s (-0.11%)
Artifact size: 390.31 MiB -> 390.37 MiB (0.02%)

JonathanBrouwer · 2025-12-24T13:02:24Z

@bors try @rust-timer queue

Cfg trace attributes, attempt 2

rust-bors · 2025-12-24T15:16:48Z

☀️ Try build successful (CI)
Build commit: ffa4b1c (ffa4b1ccb2fcb0f68df82b45ec17492d21980eaa, parent: c4aa646f15e40bd3e64ddb5017b7b89b3646ac99)

rust-timer · 2025-12-24T15:58:03Z

Finished benchmarking commit (ffa4b1c): comparison URL.

Overall result: ❌✅ regressions and improvements - please read the text below

Benchmarking this pull request means it may be perf-sensitive – we'll automatically label it not fit for rolling up. You can override this, but we strongly advise not to, due to possible changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please do so in sufficient writing along with @rustbot label: +perf-regression-triaged. If not, please fix the regressions and do another perf run. If its results are neutral or positive, the label will be automatically removed.

@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)	0.3%	[0.1%, 0.7%]	8
Regressions ❌ (secondary)	0.2%	[0.2%, 0.3%]	3
Improvements ✅ (primary)	-0.3%	[-0.4%, -0.1%]	16
Improvements ✅ (secondary)	-0.1%	[-0.2%, -0.1%]	11
All ❌✅ (primary)	-0.1%	[-0.4%, 0.7%]	24

Max RSS (memory usage)

Results (primary -1.0%, secondary 0.6%)

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)	3.3%	[3.3%, 3.3%]	1
Improvements ✅ (primary)	-1.0%	[-1.1%, -0.9%]	3
Improvements ✅ (secondary)	-0.8%	[-1.1%, -0.5%]	2
All ❌✅ (primary)	-1.0%	[-1.1%, -0.9%]	3

Cycles

Results (secondary 2.7%)

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)	2.7%	[2.0%, 3.4%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Binary size

Results (primary -0.3%, secondary -0.2%)

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)	-0.3%	[-1.8%, -0.0%]	94
Improvements ✅ (secondary)	-0.2%	[-0.9%, -0.0%]	32
All ❌✅ (primary)	-0.3%	[-1.8%, -0.0%]	94

Bootstrap: 483.398s -> 483.821s (0.09%)
Artifact size: 392.47 MiB -> 392.44 MiB (-0.01%)

JonathanBrouwer · 2025-12-25T11:50:36Z

@bors try @rust-timer queue

Cfg trace attributes, attempt 2

GuillaumeGomez · 2025-12-27T11:17:48Z

I'll try to do a review in the next day or two. If this is blocking a lot, then I apologize and feel free to merge

No need to apologize, merge can wait for you. Enjoy you holidays. :)

compiler/rustc_ast/src/attr/mod.rs

bors · 2026-01-05T21:52:02Z

☔ The latest upstream changes (presumably #150700) made this pull request unmergeable. Please resolve the merge conflicts.

rust-bors · 2026-01-05T21:54:03Z

☔ The latest upstream changes made this pull request unmergeable. Please resolve the merge conflicts.

rustbot · 2026-01-06T08:25:35Z

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.

jdonszelmann · 2026-01-06T16:07:54Z

@bors r+ rollup

bors · 2026-01-06T16:07:56Z

📌 Commit e9fdf11 has been approved by jdonszelmann

It is now in the queue for this repository.

jdonszelmann · 2026-01-06T16:08:04Z

oh wait, perf, @bors rollup=never

bors · 2026-01-06T22:59:35Z

⌛ Testing commit e9fdf11 with merge d9617c8...

bors · 2026-01-07T02:16:14Z

☀️ Test successful - checks-actions
Approved by: jdonszelmann
Pushing d9617c8 to main...

github-actions · 2026-01-07T02:19:47Z

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 0aced20 (parent) -> d9617c8 (this PR)

Test differences

Show 40 test diffs

Stage 1

clean::cfg::tests::test_parse_err: pass -> [missing] (J0)
clean::cfg::tests::test_parse_ok: pass -> [missing] (J0)

Additionally, 38 doctest diffs were found. These are ignored, as they are noisy.

Job group index

J0: aarch64-apple, aarch64-gnu, aarch64-gnu-llvm-20-2, aarch64-msvc-2, i686-gnu-2, i686-gnu-nopt-2, i686-msvc-2, x86_64-gnu, x86_64-gnu-llvm-20-1, x86_64-gnu-llvm-20-3, x86_64-gnu-llvm-21-1, x86_64-gnu-llvm-21-3, x86_64-gnu-nopt, x86_64-gnu-stable, x86_64-mingw-2, x86_64-msvc-2

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard d9617c8d9a55773a96b61ba3a4acb107d65615c1 --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-x86_64-apple: 7910.9s -> 9476.2s (+19.8%)
dist-aarch64-msvc: 5611.2s -> 6425.8s (+14.5%)
dist-apple-various: 3928.1s -> 4440.4s (+13.0%)
x86_64-gnu-tools: 3769.2s -> 3420.8s (-9.2%)
dist-x86_64-freebsd: 4897.7s -> 5274.3s (+7.7%)
test-various: 6945.1s -> 7450.5s (+7.3%)
aarch64-msvc-1: 7606.5s -> 7085.0s (-6.9%)
tidy: 173.0s -> 161.5s (-6.7%)
aarch64-apple: 10588.5s -> 11268.6s (+6.4%)
dist-ohos-x86_64: 4294.6s -> 4027.1s (-6.2%)

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 · 2026-01-07T02:58:02Z

Finished benchmarking commit (d9617c8): comparison URL.

Overall result: ❌✅ regressions and improvements - please read the text below

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)	0.3%	[0.2%, 0.6%]	5
Regressions ❌ (secondary)	0.1%	[0.1%, 0.1%]	1
Improvements ✅ (primary)	-0.3%	[-0.4%, -0.1%]	13
Improvements ✅ (secondary)	-0.2%	[-0.3%, -0.1%]	11
All ❌✅ (primary)	-0.1%	[-0.4%, 0.6%]	18

Max RSS (memory usage)

Results (primary -0.2%, 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)	0.8%	[0.7%, 0.9%]	2
Regressions ❌ (secondary)	2.6%	[1.4%, 5.0%]	3
Improvements ✅ (primary)	-2.0%	[-2.0%, -2.0%]	1
Improvements ✅ (secondary)	-1.3%	[-2.9%, -0.8%]	6
All ❌✅ (primary)	-0.2%	[-2.0%, 0.9%]	3

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)	4.3%	[4.3%, 4.3%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-3.0%	[-4.3%, -2.1%]	5
All ❌✅ (primary)	-	-	0

Binary size

Results (primary -0.5%, secondary -0.2%)

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)	-0.5%	[-1.7%, -0.0%]	48
Improvements ✅ (secondary)	-0.2%	[-0.8%, -0.0%]	14
All ❌✅ (primary)	-0.5%	[-1.7%, -0.0%]	48

Bootstrap: 474.51s -> 474.542s (0.01%)
Artifact size: 390.85 MiB -> 390.84 MiB (-0.00%)

rust-log-analyzer · 2026-01-07T11:54:20Z

A job failed! Check out the build log: (web) (plain enhanced) (plain)

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

  TOOLSTATE_PUBLISH: 1
  DEPLOY: 1
  IMAGE: dist-aarch64-linux
##[endgroup]
error: PRs changing the `nightly` channel should be sent to the `main` branch!
##[error]Process completed with exit code 1.
##[group]Run echo "disk usage:"
echo "disk usage:"
df -h
shell: /usr/bin/bash --noprofile --norc -e -o pipefail {0}

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rust-bors bot added a commit that referenced this pull request Dec 23, 2025

Auto merge of #150310 - JonathanBrouwer:cfg_trace2, r=<try>

ed1fb29

Cfg trace attributes, attempt 2

rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Dec 23, 2025

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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 Dec 23, 2025

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rust-bors bot added a commit that referenced this pull request Dec 24, 2025

Auto merge of #150310 - JonathanBrouwer:cfg_trace2, r=<try>

ffa4b1c

Cfg trace attributes, attempt 2

rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Dec 24, 2025

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rust-bors bot added a commit that referenced this pull request Dec 25, 2025

Auto merge of #150310 - JonathanBrouwer:cfg_trace2, r=<try>

080a3da

Cfg trace attributes, attempt 2

JonathanBrouwer force-pushed the cfg_trace2 branch from bc26d33 to 1c5c2df Compare December 27, 2025 12:39

jdonszelmann reviewed Jan 5, 2026

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compiler/rustc_ast/src/attr/mod.rs Outdated Show resolved Hide resolved

JonathanBrouwer force-pushed the cfg_trace2 branch from 1c5c2df to f3d6d74 Compare January 5, 2026 17:27

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JonathanBrouwer force-pushed the cfg_trace2 branch from f3d6d74 to 5c7eff8 Compare January 5, 2026 17:38

JonathanBrouwer added 4 commits January 6, 2026 09:03

Create a rustc_ast representation for parsed attributes

03fb7ee

Make cfg and cfg_attr trace attributes into early parsed attributes

5590fc0

Convert librustdoc to use the new parsed representation

4429814

Convert clippy to use the new parsed representation

e9fdf11

JonathanBrouwer force-pushed the cfg_trace2 branch from 5c7eff8 to e9fdf11 Compare January 6, 2026 08:25

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 Jan 6, 2026

bors mentioned this pull request Jan 6, 2026

naked functions: emit .private_extern on macos #148339

Merged

bors added the merged-by-bors This PR was explicitly merged by bors. label Jan 7, 2026

bors merged commit d9617c8 into rust-lang:main Jan 7, 2026
12 checks passed

rustbot added this to the 1.94.0 milestone Jan 7, 2026

jdonszelmann mentioned this pull request Jan 10, 2026

Tracking issue: Attribute refactor #131229

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Mark-Simulacrum added the perf-regression-triaged The performance regression has been triaged. label Jan 12, 2026

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Port #[cfg] and #[cfg_attr] trace attributes to the new attribute parsers #150310

Port #[cfg] and #[cfg_attr] trace attributes to the new attribute parsers #150310

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Overall result: ❌✅ regressions and improvements - please read the text below

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Overall result: ❌✅ regressions and improvements - please read the text below

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Test differences

Stage 1

Job duration changes

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Overall result: ❌✅ regressions and improvements - please read the text below

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Port `#[cfg]` and `#[cfg_attr]` trace attributes to the new attribute parsers #150310

Port `#[cfg]` and `#[cfg_attr]` trace attributes to the new attribute parsers #150310

JonathanBrouwer commented Dec 23, 2025 •

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