perf: Keep the first macro syntax-context mapping inline by xmakro · Pull Request #162712 · rust-lang/rust

xmakro · 2026-09-13T04:24:49Z

Zalathar · 2026-09-13T04:28:57Z

…ontext, r=<try> perf: Keep the first macro syntax-context mapping inline

rust-bors · 2026-09-13T05:33:08Z

☀️ Try build successful (CI)
Build commit: 9958cb9 (9958cb970a3f7eb804cf6838e055a9ec9658e486)
Base parent: 67e8d9d (67e8d9d65f33118199f9749343782cc287426587)

rust-timer · 2026-09-13T06:17:57Z

Finished benchmarking commit (9958cb9): comparison URL.

Overall result: ✅ improvements - no action needed

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.

@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)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.4%	[-0.9%, -0.1%]	45
Improvements ✅ (secondary)	-0.4%	[-0.9%, -0.1%]	28
All ❌✅ (primary)	-0.4%	[-0.9%, -0.1%]	45

Max RSS (memory usage)

Results (primary -0.4%, secondary 2.3%)

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

	mean	range	count
Regressions ❌ (primary)	0.5%	[0.5%, 0.5%]	1
Regressions ❌ (secondary)	2.3%	[2.3%, 2.3%]	1
Improvements ✅ (primary)	-0.6%	[-0.8%, -0.6%]	3
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.4%	[-0.8%, 0.5%]	4

Cycles

Results (primary -0.5%, 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)	0.8%	[0.8%, 0.8%]	1
Regressions ❌ (secondary)	3.1%	[2.7%, 3.4%]	3
Improvements ✅ (primary)	-0.8%	[-1.3%, -0.5%]	4
Improvements ✅ (secondary)	-2.2%	[-2.2%, -2.2%]	1
All ❌✅ (primary)	-0.5%	[-1.3%, 0.8%]	5

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
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.0%	[-0.0%, -0.0%]	1
Improvements ✅ (secondary)	-0.1%	[-0.1%, -0.0%]	3
All ❌✅ (primary)	-0.0%	[-0.0%, -0.0%]	1

Bootstrap: 493.573s -> 498.36s (0.97%)
Artifact size: 406.95 MiB -> 406.91 MiB (-0.01%)

Zalathar · 2026-09-14T04:38:06Z

@bors try @rust-timer queue

…ontext, r=<try> perf: Keep the first macro syntax-context mapping inline

rust-bors · 2026-09-14T05:37:08Z

☀️ Try build successful (CI)
Build commit: 8b05899 (8b0589988297e22b316bf3a9ad8140a74affbb8c)
Base parent: 4b6d04e (4b6d04e706108ccfeafe2547fbe857dfe8972bad)

rust-timer · 2026-09-14T07:04:54Z

Finished benchmarking commit (8b05899): comparison URL.

Overall result: ✅ improvements - no action needed

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.

@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)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.4%	[-1.0%, -0.1%]	63
Improvements ✅ (secondary)	-0.4%	[-1.0%, -0.2%]	28
All ❌✅ (primary)	-0.4%	[-1.0%, -0.1%]	63

Max RSS (memory usage)

Results (primary 0.5%, secondary -2.0%)

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

	mean	range	count
Regressions ❌ (primary)	3.5%	[3.5%, 3.5%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-2.5%	[-2.5%, -2.5%]	1
Improvements ✅ (secondary)	-2.0%	[-2.0%, -2.0%]	1
All ❌✅ (primary)	0.5%	[-2.5%, 3.5%]	2

Cycles

Results (primary -2.1%, 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%	[2.7%, 2.7%]	1
Improvements ✅ (primary)	-2.1%	[-2.1%, -2.1%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-2.1%	[-2.1%, -2.1%]	1

Binary size

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

Bootstrap: 501.089s -> 493.638s (-1.49%)
Artifact size: 406.85 MiB -> 406.91 MiB (0.01%)

xmakro · 2026-09-14T17:37:53Z

LLM disclosure: used LLM to analyze perf runs and write code that I then simplified

xmakro · 2026-09-16T14:56:59Z

@rustbot ready

petrochenkov · 2026-09-16T15:26:07Z

@bors r+

rust-bors · 2026-09-16T15:26:10Z

📌 Commit 677073f has been approved by petrochenkov

It is now in the queue for this repository.

JonathanBrouwer · 2026-09-16T18:09:31Z

@bors rollup=iffy
Making a rollup of perf-sensitive PRs

…uwer Rollup of 4 perf-sensitive pull requests Successful merges: - #162450 (Cache block seeking results for initialized_at_terminator and _exit) - #162543 ([rustc_resolve] Correctly keep all reexports in `ModChild::reexport_chain`) - #162712 (perf: Keep the first macro syntax-context mapping inline) - #162747 (Lowering cleanups)

Rollup merge of #162712 - xmakro:perf-review-20260907/22-marker-first-context, r=petrochenkov perf: Keep the first macro syntax-context mapping inline

rust-timer · 2026-09-17T09:17:42Z

Note

This PR was benchmarked as part of triage of its containing rollup: triage URL.

Finished benchmarking commit (4395c62): 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)	0.1%	[0.1%, 0.2%]	5
Improvements ✅ (primary)	-0.4%	[-0.9%, -0.2%]	38
Improvements ✅ (secondary)	-0.5%	[-0.9%, -0.2%]	17
All ❌✅ (primary)	-0.4%	[-0.9%, -0.2%]	38

Max RSS (memory usage)

Results (primary -1.2%, secondary -1.3%)

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

	mean	range	count
Regressions ❌ (primary)	1.0%	[1.0%, 1.0%]	1
Regressions ❌ (secondary)	2.7%	[1.1%, 4.7%]	3
Improvements ✅ (primary)	-2.3%	[-2.3%, -2.3%]	2
Improvements ✅ (secondary)	-4.4%	[-4.6%, -4.1%]	4
All ❌✅ (primary)	-1.2%	[-2.3%, 1.0%]	3

Cycles

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

Binary size

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

Bootstrap: missing data
Artifact size: 406.75 MiB -> 408.83 MiB (0.51%)

rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Sep 13, 2026

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rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Sep 13, 2026

rust-bors Bot pushed a commit that referenced this pull request Sep 13, 2026

Auto merge of #162712 - xmakro:perf-review-20260907/22-marker-first-c…

9958cb9

…ontext, r=<try> perf: Keep the first macro syntax-context mapping inline

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rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Sep 13, 2026

ChayimFriedman2 reviewed Sep 14, 2026

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Comment thread compiler/rustc_expand/src/mbe/transcribe.rs Outdated

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rust-bors Bot pushed a commit that referenced this pull request Sep 14, 2026

Auto merge of #162712 - xmakro:perf-review-20260907/22-marker-first-c…

8b05899

…ontext, r=<try> perf: Keep the first macro syntax-context mapping inline

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rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Sep 14, 2026

petrochenkov self-assigned this Sep 14, 2026

petrochenkov 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 Sep 14, 2026

xmakro force-pushed the perf-review-20260907/22-marker-first-context branch from 8460e18 to 0361612 Compare September 14, 2026 16:38

xmakro marked this pull request as ready for review September 14, 2026 17:37

petrochenkov reviewed Sep 15, 2026

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Comment thread compiler/rustc_expand/src/mbe/transcribe.rs Outdated

Comment thread compiler/rustc_expand/src/mbe/transcribe.rs Outdated

petrochenkov removed the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Sep 15, 2026

petrochenkov added the S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. label Sep 15, 2026

Keep the first macro syntax-context mapping inline

677073f

xmakro force-pushed the perf-review-20260907/22-marker-first-context branch from 0361612 to 677073f Compare September 16, 2026 14:29

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 Sep 16, 2026

rust-bors Bot 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 Sep 16, 2026

JonathanBrouwer mentioned this pull request Sep 16, 2026

Rollup of 4 perf-sensitive pull requests #162859

Merged

rust-bors Bot merged commit 867d696 into rust-lang:main Sep 17, 2026
13 checks passed

rustbot added this to the 1.100.0 milestone Sep 17, 2026

rust-bors Bot pushed a commit that referenced this pull request Sep 17, 2026

Unrolled build for #162712 in rollup 162859

4395c62

Rollup merge of #162712 - xmakro:perf-review-20260907/22-marker-first-context, r=petrochenkov perf: Keep the first macro syntax-context mapping inline

rustbot added the perf-regression Performance regression. label Sep 17, 2026

github-actions Bot mentioned this pull request Oct 2, 2026

Toolchain upgrade to nightly-2026-09-25 flux-rs/flux#1803

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rust-timer commented Sep 13, 2026

Overall result: ✅ improvements - no action needed

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Overall result: ✅ improvements - no action needed

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

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xmakro commented Sep 13, 2026 •

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