Restore simpler Encode/Decode impls for u32 and (on 64bit systems) usize by bjorn3 · Pull Request #157182 · rust-lang/rust

bjorn3 · 2026-05-31T09:32:35Z

This fixes the perf regression in #157076.

rustbot · 2026-05-31T09:32:40Z

rustbot has assigned @petrochenkov.
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Owners of files modified in this PR: @petrochenkov

bjorn3 · 2026-05-31T11:03:05Z

@bors try @rust-timer queue

Revert "Implement Encode and Decode for proc_macro::TokenStream wrapper type"

rust-bors · 2026-05-31T13:13:12Z

☀️ Try build successful (CI)
Build commit: a7931ec (a7931ecedd0a736e4d0bb8bf01d3cdc41cc9c59a, parent: c315891193c35827c2d789adce686f8a5481778f)

rust-timer · 2026-05-31T14:06:53Z

Finished benchmarking commit (a7931ec): comparison URL.

Overall result: ❌ regressions - 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)	0.4%	[0.4%, 0.4%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.4%	[0.4%, 0.4%]	1

Max RSS (memory usage)

Results (primary 6.6%, secondary -6.2%)

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

	mean	range	count
Regressions ❌ (primary)	6.6%	[3.4%, 8.5%]	4
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-6.2%	[-6.2%, -6.2%]	1
All ❌✅ (primary)	6.6%	[3.4%, 8.5%]	4

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: 509.639s -> 511.772s (0.42%)
Artifact size: 400.69 MiB -> 400.75 MiB (0.02%)

rustbot · 2026-05-31T15:11:28Z

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.

bjorn3 · 2026-05-31T15:11:42Z

@bors try @rust-timer queue

Revert "Implement Encode and Decode for proc_macro::TokenStream wrapper type"

rust-bors · 2026-05-31T17:21:12Z

☀️ Try build successful (CI)
Build commit: 23e5f23 (23e5f230eeb49af7959b165167c00a7d3f38ac9b, parent: 9e293ae9f8abecb0be5105787d181518c9012a19)

rust-timer · 2026-05-31T18:02:23Z

Finished benchmarking commit (23e5f23): 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)	-0.6%	[-0.9%, -0.3%]	6
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (primary -1.1%)

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

	mean	range	count
Regressions ❌ (primary)	2.2%	[2.2%, 2.2%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-4.3%	[-4.3%, -4.3%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-1.1%	[-4.3%, 2.2%]	2

Cycles

Results (primary 2.6%)

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

	mean	range	count
Regressions ❌ (primary)	2.6%	[2.6%, 2.6%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	2.6%	[2.6%, 2.6%]	1

Binary size

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

Bootstrap: 508.947s -> 512.149s (0.63%)
Artifact size: 400.66 MiB -> 400.68 MiB (0.00%)

bjorn3 · 2026-05-31T18:45:46Z

I'm surprised this didn't get optimized away on 64bit. This commit is required for ensuring 32bit wasm proc-macros encode/decode usize the same way as a 64bit rustc host. Maybe codegening the original code on 64bit and using the new code on 32bit would work? Should also be fine to revert back to the old code for u32.

bjorn3 · 2026-06-02T12:34:53Z

@bors try @rust-timer queue

Revert "Use platform independent encoding for integers in proc-macro RPC"

rust-bors · 2026-06-02T14:45:20Z

☀️ Try build successful (CI)
Build commit: f248d0e (f248d0e17bc99781e30fce8a93824a3023e320bc, parent: 4f84d9fac456d973d592cf3fb48db958ecf22506)

rust-timer · 2026-06-02T15:47:38Z

Finished benchmarking commit (f248d0e): 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)	-0.6%	[-0.9%, -0.3%]	6
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (primary 1.5%)

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

	mean	range	count
Regressions ❌ (primary)	3.9%	[2.0%, 6.2%]	3
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-5.6%	[-5.6%, -5.6%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.5%	[-5.6%, 6.2%]	4

Cycles

Results (primary 2.5%, secondary 12.9%)

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

	mean	range	count
Regressions ❌ (primary)	2.5%	[2.5%, 2.5%]	1
Regressions ❌ (secondary)	20.5%	[18.9%, 22.0%]	4
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.3%	[-2.8%, -1.7%]	2
All ❌✅ (primary)	2.5%	[2.5%, 2.5%]	1

Binary size

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

Bootstrap: 510.625s -> 512.605s (0.39%)
Artifact size: 400.75 MiB -> 400.70 MiB (-0.01%)

bjorn3 · 2026-06-02T15:53:48Z

@rustbot ready

petrochenkov · 2026-06-02T16:07:02Z

@bors r+

rust-bors · 2026-06-02T16:07:05Z

📌 Commit 936f0ce has been approved by petrochenkov

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.

…ochenkov Restore simpler Encode/Decode impls for u32 and (on 64bit systems) usize This fixes the perf regression in rust-lang#157076.

…uwer Rollup of 9 pull requests Successful merges: - #157035 (`LivenessValues`: use dedicated enum rather than mutually exclusive `Option`s) - #157182 (Restore simpler Encode/Decode impls for u32 and (on 64bit systems) usize) - #157310 (rustdoc: Render `impl` restriction) - #157070 (Remove `skip_arg` attribute from `Diagnostic` and `Subdiagnostic` proc-macros) - #157137 (rustc_target: Use +spe for powerpcspe targets) - #157215 (Implement argument-dependent target checking for the `#[repr]` parser) - #157235 (additional changes for issue-144595) - #157321 (Remove unnecessary arm in `handle_res`) - #157324 (Add test for undefined EII static error)

Rollup merge of #157182 - bjorn3:fix_perf_regression, r=petrochenkov Restore simpler Encode/Decode impls for u32 and (on 64bit systems) usize This fixes the perf regression in #157076.

rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label May 31, 2026

rustbot assigned petrochenkov May 31, 2026