expand: Micro-optimize prelude injection #144587

petrochenkov · 2025-07-28T14:37:45Z

Use splice to avoid shifting the other items twice.
Put extern crate std; first so it's already resolved when we resolve ::std::prelude::rust_20XX.

Use `splice` to avoid shifting the other items twice. Put `extern crate std;` first so it's already resolved when we resolve `::std::prelude::rust_20XX`.

rustbot · 2025-07-28T14:37:50Z

r? @lcnr

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rustbot · 2025-07-28T14:37:54Z

Changes to the code generated for builtin derived traits.

cc @nnethercote

petrochenkov · 2025-07-28T14:38:49Z

It's probably within the noise, but let's try.
@bors2 try @rust-timer queue

expand: Micro-optimize prelude injection

rust-bors · 2025-07-28T14:38:54Z

⌛ Trying commit c56f49d with merge 50660dc…

To cancel the try build, run the command @bors try cancel.

rust-bors · 2025-07-28T16:54:43Z

☀️ Try build successful (CI)
Build commit: 50660dc (50660dca656b745763302a57e270bfff7163a885, parent: 65b6cdb6a6d33987b9d642a4882283c71fbe3957)

rust-timer · 2025-07-28T18:54:44Z

Finished benchmarking commit (50660dc): comparison URL.

Overall result: ❌✅ regressions and improvements - no action needed

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.

@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)	0.0%	[0.0%, 0.0%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.8%	[-1.0%, -0.0%]	7
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (primary 1.3%, 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)	1.3%	[1.3%, 1.3%]	1
Regressions ❌ (secondary)	2.3%	[2.3%, 2.3%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.3%	[1.3%, 1.3%]	1

Cycles

Results (primary -2.2%, secondary -1.1%)

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)	3.6%	[3.6%, 3.6%]	1
Improvements ✅ (primary)	-2.2%	[-2.2%, -2.2%]	1
Improvements ✅ (secondary)	-2.7%	[-3.4%, -2.2%]	3
All ❌✅ (primary)	-2.2%	[-2.2%, -2.2%]	1

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: 468.035s -> 467.096s (-0.20%)
Artifact size: 376.82 MiB -> 376.87 MiB (0.01%)

nnethercote · 2025-07-29T04:16:18Z

Why not, it's a tiny bit cleaner, and I like the pp output more.

@bors r+

bors · 2025-07-29T04:16:21Z

📌 Commit c56f49d has been approved by nnethercote

It is now in the queue for this repository.

bors · 2025-07-29T06:14:46Z

⌛ Testing commit c56f49d with merge 0410836...

expand: Micro-optimize prelude injection Use `splice` to avoid shifting the other items twice. Put `extern crate std;` first so it's already resolved when we resolve `::std::prelude::rust_20XX`.

bors · 2025-07-29T06:22:47Z

💔 Test failed - checks-actions

rust-log-analyzer · 2025-07-29T06:26:26Z

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)


  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
  0     0    0     0    0     0      0      0 --:--:--  0:01:16 --:--:--     0
curl: (35) schannel: next InitializeSecurityContext failed: CRYPT_E_REVOCATION_OFFLINE (0x80092013) - The revocation function was unable to check revocation because the revocation server was offline.
##[error]Process completed with exit code 35.
Post job cleanup.
[command]"C:\Program Files\Git\bin\git.exe" version
git version 2.50.1.windows.1
Copying 'C:\Users\runneradmin\.gitconfig' to 'D:\a\_temp\beb53847-a574-402d-9380-f03b5d4479b3\.gitconfig'
Temporarily overriding HOME='D:\a\_temp\beb53847-a574-402d-9380-f03b5d4479b3' before making global git config changes

petrochenkov · 2025-07-29T06:30:50Z

I want to check the cachegrind diff first, the perf results are a bit weird.
@rustbot author

rustbot · 2025-07-29T06:30:54Z

Reminder, once the PR becomes ready for a review, use @rustbot ready.

lqd · 2025-07-29T06:39:51Z

I want to check the cachegrind diff first, the perf results are a bit weird.

match-stress was noisy very recently

petrochenkov · 2025-07-29T12:47:22Z

r? @nnethercote
@bors r=nnethercote rollup

bors · 2025-07-29T12:47:25Z

💡 This pull request was already approved, no need to approve it again.

This pull request previously failed. You should add more commits to fix the bug, or use retry to trigger a build again.
There's another pull request that is currently being tested, blocking this pull request: Rollup of 13 pull requests #144633

bors · 2025-07-29T12:47:26Z

📌 Commit c56f49d has been approved by nnethercote

It is now in the queue for this repository.

rustbot · 2025-07-29T12:47:27Z

nnethercote is not on the review rotation at the moment.
They may take a while to respond.

Rollup of 6 pull requests Successful merges: - #144560 (coverage: Treat `#[automatically_derived]` as `#[coverage(off)]`) - #144566 (Simplify `align_of_val::<[T]>(…)` → `align_of::<T>()`) - #144587 (expand: Micro-optimize prelude injection) - #144589 (Account for `.yield` in illegal postfix operator message) - #144615 (Make resolve_fn_signature responsible for its own rib.) - #144634 (Fix typo in `DropGuard` doc) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of #144587 - petrochenkov:optstdprel, r=nnethercote expand: Micro-optimize prelude injection Use `splice` to avoid shifting the other items twice. Put `extern crate std;` first so it's already resolved when we resolve `::std::prelude::rust_20XX`.

expand: Micro-optimize prelude injection

c56f49d

Use `splice` to avoid shifting the other items twice. Put `extern crate std;` first so it's already resolved when we resolve `::std::prelude::rust_20XX`.

rustbot assigned lcnr Jul 28, 2025

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 Jul 28, 2025

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rust-bors bot added a commit that referenced this pull request Jul 28, 2025

Auto merge of #144587 - petrochenkov:optstdprel, r=<try>

50660dc

expand: Micro-optimize prelude injection

rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Jul 28, 2025

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rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Jul 28, 2025

petrochenkov added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jul 28, 2025

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-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jul 29, 2025

bors added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Jul 29, 2025

rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jul 29, 2025

rustbot assigned nnethercote Jul 29, 2025

rustbot unassigned lcnr Jul 29, 2025

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-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jul 29, 2025

Zalathar mentioned this pull request Jul 29, 2025

Rollup of 6 pull requests #144637

Merged

bors merged commit 3d5e2fa into rust-lang:master Jul 29, 2025
11 of 12 checks passed

rustbot added this to the 1.90.0 milestone Jul 29, 2025

expand: Micro-optimize prelude injection #144587

expand: Micro-optimize prelude injection #144587

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petrochenkov commented Jul 28, 2025

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rust-timer commented Jul 28, 2025

Overall result: ❌✅ regressions and improvements - no action needed

Instruction count

Max RSS (memory usage)

Cycles

Binary size

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nnethercote commented Jul 29, 2025

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