Minor optimizations around macro parsing by bal-e · Pull Request #164540 · rust-lang/rust

bal-e · 2026-10-18T22:05:59Z

Picked out some standalone commits from my macro matching optimization work. These are independent small optimizations that should add up to a tiny but measurable perf win.

Part of #159951. Best reviewed commit-by-commit. No LLMs used.

r? @nnethercote

It does not have any use, and it is a no-op we have to process on the hot path of macro parsing.

The parsing code is much hotter than `compute_locs()`, so perform the match over there. This might mildly change the debug representation of computed `[MatcherLoc]`s, but it's probably worthwhile for perf.

rustbot · 2026-10-18T22:06:06Z

Thanks for the pull request, and welcome! The Rust Project has assigned @nnethercote (or someone else) to review your changes, you should hear from them (or someone else) within the next two weeks.

Please see the contribution instructions and our LLM policy for more information.

nnethercote · 2026-10-19T06:29:40Z

@bors try @rust-timer queue

Minor optimizations around macro parsing

rust-bors · 2026-10-19T07:34:05Z

☀️ Try build successful (CI)
Build commit: 9d5633d (9d5633d7dfe2a53ced47ac7b1c2ea122fe6ca791)
Base parent: b6eeb93 (b6eeb93c992027a03e1fd120b6652546396b142c)

rust-timer · 2026-10-19T08:44:57Z

Finished benchmarking commit (9d5633d): comparison URL.

Overall result: ✅ improvements - no action needed

Benchmarking means the PR may be perf-sensitive. Consider adding rollup=never if this change is not fit for rolling up.

@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
Improvements ✅ (secondary)	-0.3%	[-0.3%, -0.2%]	2
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (primary 1.5%, secondary 1.2%)

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

	mean	range	count
Regressions ❌ (primary)	1.5%	[1.5%, 1.5%]	1
Regressions ❌ (secondary)	1.2%	[1.2%, 1.2%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.5%	[1.5%, 1.5%]	1

Cycles

Results (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)	-	-	0
Regressions ❌ (secondary)	2.4%	[2.4%, 2.4%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 489.811s -> 492.784s (0.61%)
Artifact size: 408.98 MiB -> 409.03 MiB (0.01%)

nnethercote · 2026-10-20T13:00:38Z

@bors r+ rollup

rust-bors · 2026-10-20T13:00:41Z

📌 Commit 5fc2428 has been approved by nnethercote

It is now in the queue for this repository.

🌲 The tree is currently closed for pull requests below priority 5. This pull request will be tested once the tree is reopened.

Reason for tree closure: spurious failures

@nnethercote

Minor optimizations around macro parsing Picked out some standalone commits from my macro matching optimization work. These are independent small optimizations that should add up to a tiny but measurable perf win. Part of rust-lang#159951. Best reviewed commit-by-commit. No LLMs used. r? @nnethercote

…uwer Rollup of 15 pull requests Successful merges: - #163664 (Add new `RUSTC_BOOTSTRAP=-allow-unstable-compiler-flags` mode for testing stable compiler behavior in UI tests) - #163104 ([debuginfo] Emit `usize` and `isize` as typedefs) - #163338 (MIR move elimination [4/6]: MoveElimination) - #163701 (add ReadDir::dir to get the directory handle of the underlying directory) - #164488 (Don't try to skip anything in `Skip::advance_by(0)`) - #164611 (Improve bit permutation codegen) - #164612 (std: Combine `is_powerpc64_feature_detected` into `is_powerpc_feature_detected`) - #148842 (Avoid incorrect lifetime suggestion involving `sym::anon`) - #162668 (document that `!` does bitwise and logical negation) - #164264 (lint: suggest `fXX::is_nan` for unsuffixed NaN comparisons) - #164509 (layout invariant: turn delayed bug back into proper assertion) - #164540 (Minor optimizations around macro parsing) - #164594 (rustdoc: Correctly handle inner `deprecated` attribute on modules) - #164595 (Allow attributes in function trait parameters) - #164629 (arch::breakpoint: avoid confusing 'equivalent' terminology)

@nnethercote

Minor optimizations around macro parsing Picked out some standalone commits from my macro matching optimization work. These are independent small optimizations that should add up to a tiny but measurable perf win. Part of rust-lang#159951. Best reviewed commit-by-commit. No LLMs used. r? @nnethercote

…uwer Rollup of 14 pull requests Successful merges: - #163664 (Add new `RUSTC_BOOTSTRAP=-allow-unstable-compiler-flags` mode for testing stable compiler behavior in UI tests) - #163104 ([debuginfo] Emit `usize` and `isize` as typedefs) - #163701 (add ReadDir::dir to get the directory handle of the underlying directory) - #164488 (Don't try to skip anything in `Skip::advance_by(0)`) - #164611 (Improve bit permutation codegen) - #164612 (std: Combine `is_powerpc64_feature_detected` into `is_powerpc_feature_detected`) - #148842 (Avoid incorrect lifetime suggestion involving `sym::anon`) - #162668 (document that `!` does bitwise and logical negation) - #164264 (lint: suggest `fXX::is_nan` for unsuffixed NaN comparisons) - #164509 (layout invariant: turn delayed bug back into proper assertion) - #164540 (Minor optimizations around macro parsing) - #164594 (rustdoc: Correctly handle inner `deprecated` attribute on modules) - #164595 (Allow attributes in function trait parameters) - #164629 (arch::breakpoint: avoid confusing 'equivalent' terminology)

@nnethercote

Minor optimizations around macro parsing Picked out some standalone commits from my macro matching optimization work. These are independent small optimizations that should add up to a tiny but measurable perf win. Part of rust-lang#159951. Best reviewed commit-by-commit. No LLMs used. r? @nnethercote

…uwer Rollup of 19 pull requests Successful merges: - #163664 (Add new `RUSTC_BOOTSTRAP=-allow-unstable-compiler-flags` mode for testing stable compiler behavior in UI tests) - #163668 (Remap syntax contexts and expansion ids for det. metadata encoding) - #160404 (fd-views: AsRef<File>&Co. for BorrowedFd) - #163104 ([debuginfo] Emit `usize` and `isize` as typedefs) - #163317 (Stop useless caching of post-LTO artifact caching for fat LTO) - #163701 (add ReadDir::dir to get the directory handle of the underlying directory) - #164488 (Don't try to skip anything in `Skip::advance_by(0)`) - #164507 (Encode HashMap and HashSet in deterministic order when an encoder requires determinism) - #164611 (Improve bit permutation codegen) - #164612 (std: Combine `is_powerpc64_feature_detected` into `is_powerpc_feature_detected`) - #148842 (Avoid incorrect lifetime suggestion involving `sym::anon`) - #162668 (document that `!` does bitwise and logical negation) - #164264 (lint: suggest `fXX::is_nan` for unsuffixed NaN comparisons) - #164509 (layout invariant: turn delayed bug back into proper assertion) - #164540 (Minor optimizations around macro parsing) - #164594 (rustdoc: Correctly handle inner `deprecated` attribute on modules) - #164595 (Allow attributes in function trait parameters) - #164641 (Stabilize `slice_split_once`) - #164646 (Adjust rustfmt subtree sync docs to not use `--allow-noop` for now)

Rollup of 20 pull requests Successful merges: - #163664 (Add new `RUSTC_BOOTSTRAP=-allow-unstable-compiler-flags` mode for testing stable compiler behavior in UI tests) - #163668 (Remap syntax contexts and expansion ids for det. metadata encoding) - #163104 ([debuginfo] Emit `usize` and `isize` as typedefs) - #163317 (Stop useless caching of post-LTO artifact caching for fat LTO) - #163701 (add ReadDir::dir to get the directory handle of the underlying directory) - #164488 (Don't try to skip anything in `Skip::advance_by(0)`) - #164507 (Encode HashMap and HashSet in deterministic order when an encoder requires determinism) - #164611 (Improve bit permutation codegen) - #164612 (std: Combine `is_powerpc64_feature_detected` into `is_powerpc_feature_detected`) - #148842 (Avoid incorrect lifetime suggestion involving `sym::anon`) - #162668 (document that `!` does bitwise and logical negation) - #164264 (lint: suggest `fXX::is_nan` for unsuffixed NaN comparisons) - #164509 (layout invariant: turn delayed bug back into proper assertion) - #164540 (Minor optimizations around macro parsing) - #164594 (rustdoc: Correctly handle inner `deprecated` attribute on modules) - #164595 (Allow attributes in function trait parameters) - #164616 (Add test for VecDeque with a custom allocator) - #164629 (arch::breakpoint: avoid confusing 'equivalent' terminology) - #164641 (Stabilize `slice_split_once`) - #164646 (Adjust rustfmt subtree sync docs to not use `--allow-noop` for now)

@nnethercote

Rollup merge of #164540 - bal-e:mini-macro-opts, r=nnethercote Minor optimizations around macro parsing Picked out some standalone commits from my macro matching optimization work. These are independent small optimizations that should add up to a tiny but measurable perf win. Part of #159951. Best reviewed commit-by-commit. No LLMs used. r? @nnethercote

Rollup of 20 pull requests Successful merges: - rust-lang/rust#163664 (Add new `RUSTC_BOOTSTRAP=-allow-unstable-compiler-flags` mode for testing stable compiler behavior in UI tests) - rust-lang/rust#163668 (Remap syntax contexts and expansion ids for det. metadata encoding) - rust-lang/rust#163104 ([debuginfo] Emit `usize` and `isize` as typedefs) - rust-lang/rust#163317 (Stop useless caching of post-LTO artifact caching for fat LTO) - rust-lang/rust#163701 (add ReadDir::dir to get the directory handle of the underlying directory) - rust-lang/rust#164488 (Don't try to skip anything in `Skip::advance_by(0)`) - rust-lang/rust#164507 (Encode HashMap and HashSet in deterministic order when an encoder requires determinism) - rust-lang/rust#164611 (Improve bit permutation codegen) - rust-lang/rust#164612 (std: Combine `is_powerpc64_feature_detected` into `is_powerpc_feature_detected`) - rust-lang/rust#148842 (Avoid incorrect lifetime suggestion involving `sym::anon`) - rust-lang/rust#162668 (document that `!` does bitwise and logical negation) - rust-lang/rust#164264 (lint: suggest `fXX::is_nan` for unsuffixed NaN comparisons) - rust-lang/rust#164509 (layout invariant: turn delayed bug back into proper assertion) - rust-lang/rust#164540 (Minor optimizations around macro parsing) - rust-lang/rust#164594 (rustdoc: Correctly handle inner `deprecated` attribute on modules) - rust-lang/rust#164595 (Allow attributes in function trait parameters) - rust-lang/rust#164616 (Add test for VecDeque with a custom allocator) - rust-lang/rust#164629 (arch::breakpoint: avoid confusing 'equivalent' terminology) - rust-lang/rust#164641 (Stabilize `slice_split_once`) - rust-lang/rust#164646 (Adjust rustfmt subtree sync docs to not use `--allow-noop` for now)

arya dradjica added 3 commits October 18, 2026 23:04

Remove MatcherLoc::Delimited

0b7a2d9

It does not have any use, and it is a no-op we have to process on the hot path of macro parsing.

Strip doc-comment tokens in compute_locs()

b012329

The parsing code is much hotter than `compute_locs()`, so perform the match over there. This might mildly change the debug representation of computed `[MatcherLoc]`s, but it's probably worthwhile for perf.

Remove redundant return value in try_match_*()

5fc2428

rustbot assigned nnethercote Oct 18, 2026

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Oct 18, 2026

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rust-bors Bot pushed a commit that referenced this pull request Oct 19, 2026

Auto merge of #164540 - bal-e:mini-macro-opts, r=<try>

9d5633d

Minor optimizations around macro parsing

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rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Oct 19, 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 Oct 20, 2026

JonathanBrouwer mentioned this pull request Oct 20, 2026

Rollup of 15 pull requests #164639

Closed

JonathanBrouwer mentioned this pull request Oct 20, 2026

Rollup of 14 pull requests #164640

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JonathanBrouwer mentioned this pull request Oct 20, 2026

Rollup of 19 pull requests #164658

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jhpratt mentioned this pull request Oct 21, 2026

Rollup of 20 pull requests #164662

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rust-bors Bot merged commit 2013a33 into rust-lang:main Oct 21, 2026
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rustbot added this to the 1.101.0 milestone Oct 21, 2026

bal-e mentioned this pull request Oct 21, 2026

Tracking issue (ish) for some declarative macro optimizations #159951

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github-actions Bot mentioned this pull request Oct 22, 2026

Toolchain upgrade to nightly-2026-10-22 flux-rs/flux#1847

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Minor optimizations around macro parsing - #164540

Minor optimizations around macro parsing#164540
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rust-timer commented Oct 19, 2026

Overall result: ✅ improvements - no action needed

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bal-e commented Oct 18, 2026 •

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