Skip to content

Simplify option-iterator flattening in the compiler#158627

Open
cuviper wants to merge 2 commits into
rust-lang:mainfrom
cuviper:option-iterator-flattening
Open

Simplify option-iterator flattening in the compiler#158627
cuviper wants to merge 2 commits into
rust-lang:mainfrom
cuviper:option-iterator-flattening

Conversation

@cuviper

@cuviper cuviper commented Jun 30, 2026

Copy link
Copy Markdown
Member

In many cases where we are flattening option::IntoIter<I>, we can use
Option::into_flat_iter() instead for a simpler implementation. A few
other cases have more direct constructs available.

cuviper added 2 commits June 30, 2026 12:21
@cuviper
Use Option::into_flat_iter in the compiler
4480d78 
In many cases where we are flattening `option::IntoIter<I>`, we can use
`into_flat_iter()` instead for a simpler implementation.
@cuviper
Use more direct ways to flatten option-iterators
ef3084c
@rustbot 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. WG-trait-system-refactor The Rustc Trait System Refactor Initiative (-Znext-solver) labels Jun 30, 2026
@cuviper

cuviper commented Jun 30, 2026

Copy link
Copy Markdown
Member Author

@bors try @rust-timer queue

@rust-timer

This comment has been minimized.

Sign in to view
@rustbot rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Jun 30, 2026
@rust-bors

This comment has been minimized.

Sign in to view
rust-bors Bot pushed a commit that referenced this pull request Jun 30, 2026
@bors
Auto merge of #158627 - cuviper:option-iterator-flattening, r=<try>
118fe6f 
Simplify option-iterator flattening in the compiler
@cuviper cuviper removed the WG-trait-system-refactor The Rustc Trait System Refactor Initiative (-Znext-solver) label Jun 30, 2026
@rust-bors

rust-bors Bot commented Jun 30, 2026

Copy link
Copy Markdown
Contributor

☀️ Try build successful (CI)
Build commit: 118fe6f (118fe6fbecfcc44a3d5617a8c99ec3edeb72d5f6)
Base parent: f46ec52 (f46ec5218fe7829ac18323b5ee0b409a63169f27)

@rust-timer

This comment has been minimized.

Sign in to view
@rust-timer

rust-timer commented Jun 30, 2026

Copy link
Copy Markdown
Collaborator

Finished benchmarking commit (118fe6f): 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)		 -0.3% [-0.3%, -0.3%] 2
Improvements ✅
(secondary)		 - - 0
All ❌✅ (primary) -0.3% [-0.3%, -0.3%] 2

Max RSS (memory usage)

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

Cycles

Results (primary 2.3%, secondary -0.9%)

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

mean range count
Regressions ❌
(primary)		 2.3% [2.3%, 2.3%] 1
Regressions ❌
(secondary)		 2.1% [2.1%, 2.1%] 1
Improvements ✅
(primary)		 - - 0
Improvements ✅
(secondary)		 -3.9% [-3.9%, -3.9%] 1
All ❌✅ (primary) 2.3% [2.3%, 2.3%] 1

Binary size

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

Bootstrap: 485.565s -> 488.649s (0.64%)
Artifact size: 393.29 MiB -> 393.15 MiB (-0.04%)

@rustbot rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Jun 30, 2026
@cuviper

cuviper commented Jul 1, 2026

Copy link
Copy Markdown
Member Author

Of course I hoped for more of a perf improvement, but at least it's not bad. :)

@cuviper cuviper marked this pull request as ready for review July 1, 2026 17:02
@rustbot

rustbot commented Jul 1, 2026

Copy link
Copy Markdown
Collaborator

Some changes occurred to the core trait solver

cc @rust-lang/initiative-trait-system-refactor

Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

Some changes occurred in coverage instrumentation.

cc @Zalathar

@rustbot 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 Jul 1, 2026
@rustbot

rustbot commented Jul 1, 2026

Copy link
Copy Markdown
Collaborator

r? @nnethercote

rustbot has assigned @nnethercote.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

Why was this reviewer chosen?

The reviewer was selected based on:

  • Owners of files modified in this PR: compiler
  • compiler expanded to 73 candidates
  • Random selection from 16 candidates

@nnethercote

nnethercote commented Jul 2, 2026

Copy link
Copy Markdown
Contributor

@bors r+

@rust-bors

rust-bors Bot commented Jul 2, 2026

Copy link
Copy Markdown
Contributor

📌 Commit ef3084c has been approved by nnethercote

It is now in the queue for this repository.

🌲 The tree is currently closed for pull requests below priority 1. This pull request will be tested once the tree is reopened.

@rust-bors 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 Jul 2, 2026
jhpratt added a commit to jhpratt/rust that referenced this pull request Jul 2, 2026
@jhpratt
Rollup merge of rust-lang#158627 - cuviper:option-iterator-flattening…
575fb2d 
…, r=nnethercote

Simplify option-iterator flattening in the compiler

In many cases where we are flattening `option::IntoIter<I>`, we can use
`Option::into_flat_iter()` instead for a simpler implementation. A few
other cases have more direct constructs available.
@jhpratt jhpratt mentioned this pull request Jul 2, 2026
Closed
rust-bors Bot pushed a commit that referenced this pull request Jul 2, 2026
@bors
Auto merge of #158685 - jhpratt:rollup-xurCZHF, r=jhpratt
0625620 
Rollup of 5 pull requests

Successful merges:

 - #155429 (Support `u128`/`i128` c-variadic arguments)
 - #158627 (Simplify option-iterator flattening in the compiler)
 - #158669 (Remove `src/tools/test-float-parse/Cargo.lock`)
 - #158674 (library: Polish transmute's `split_at_stdlib` example)
 - #158682 (Avoid delayed bug for disabled on_type_error arguments)
JonathanBrouwer added a commit to JonathanBrouwer/rust that referenced this pull request Jul 2, 2026
@JonathanBrouwer
Rollup merge of rust-lang#158627 - cuviper:option-iterator-flattening…
17973f2 
…, r=nnethercote

Simplify option-iterator flattening in the compiler

In many cases where we are flattening `option::IntoIter<I>`, we can use
`Option::into_flat_iter()` instead for a simpler implementation. A few
other cases have more direct constructs available.
@JonathanBrouwer JonathanBrouwer mentioned this pull request Jul 2, 2026
Open
rust-bors Bot pushed a commit that referenced this pull request Jul 3, 2026
@bors
Auto merge of #158700 - JonathanBrouwer:rollup-HusuWnV, r=JonathanBro…
34fd20b 
…uwer

Rollup of 22 pull requests

Successful merges:

 - #155429 (Support `u128`/`i128` c-variadic arguments)
 - #158100 (Emit retags in codegen to support BorrowSanitizer (part 4))
 - #158494 (Improve E0277 diagnostics for conditionally implemented traits)
 - #158606 (use ProjectionPredicate instead of AliasRelate)
 - #158627 (Simplify option-iterator flattening in the compiler)
 - #158658 (Update LLVM submodule)
 - #158665 (Revert "Remove redundant dyn-compatibility check.")
 - #158021 (Remove old MinGW workaround)
 - #158473 (Add `riscv32imfc-unknown-none-elf` bare-metal target)
 - #158549 (process::exec: using appropriate exit code on vxworks.)
 - #158585 (Improve diagnostic for too many super keywords)
 - #158637 (hir_ty_lowering: avoid self type lookup for inherent aliases)
 - #158651 (ptr doc: reduce use of unsafe block to where needed)
 - #158669 (Remove `src/tools/test-float-parse/Cargo.lock`)
 - #158674 (library: Polish transmute's `split_at_stdlib` example)
 - #158677 (Add extra splat tests)
 - #158680 (Avoid ICE for `NonZero<char>` in improper_ctypes)
 - #158681 (Remove unnecessary `Hash` derives from MIR types)
 - #158682 (Avoid delayed bug for disabled on_type_error arguments)
 - #158684 (Add missing generic test coverage for ```#[splat]```)
 - #158687 (Streamline `MacEager`)
 - #158688 (Cleanup attribute docs and add links to other mentioned attributes)
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment

Reviewers

@nnethercote nnethercote nnethercote approved these changes

Assignees

@nnethercote nnethercote

Labels

S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.

Projects

None yet

Milestone

No milestone

Development

Successfully merging this pull request may close these issues.

4 participants

@cuviper @rust-timer @rustbot @nnethercote