Stabilize `sse4a` and `tbm` target features #144542

sayantn · 2025-07-27T18:46:27Z

This PR stabilizes the feature flag sse4a_target_feature and tbm_target_feature (tracking issue #44839).

Public API

The 2 x86 target features sse4a and tbm

Also, these were added in LLVM2.6 and LLVM3.4-rc1, respectively, and as the minimum LLVM required for rustc is LLVM19, we are safe in that front too!

As all of the required tasks have been done (adding the target features to rustc, implementing their runtime detection in std_detect and implementing the associated intrinsics in core_arch), these target features can be stabilized now. The intrinsics were stabilized long ago, in 1.27.0

Reference PR:

Add doc for sse4a and tbm reference#1949

cc @rust-lang/lang

@rustbot label I-lang-nominated
r? lang

rustbot · 2025-07-27T18:46:31Z

r? @petrochenkov

rustbot has assigned @petrochenkov.
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

rustbot · 2025-07-27T18:46:33Z

stdarch is developed in its own repository. If possible, consider making this change to rust-lang/stdarch instead.

cc @Amanieu, @folkertdev, @sayantn

traviscross · 2025-07-28T01:09:07Z

Thanks. This needs a PR to the Reference.

cc @tgross35 @RalfJung @Amanieu @workingjubilee @rust-lang/lang-docs

RalfJung · 2025-07-28T06:06:08Z

The usual question for target feature stabilizations:
Are there any ABI concerns? Is there any potential unsoundness or other problems when mixing code built with and without these features?

tmandry · 2025-07-30T15:41:31Z

@rfcbot fcp merge

rfcbot · 2025-07-30T15:41:34Z

Team member @tmandry has proposed to merge this. The next step is review by the rest of the tagged team members:

No concerns currently listed.

Once a majority of reviewers approve (and at most 2 approvals are outstanding), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up!

cc @rust-lang/lang-advisors: FCP proposed for lang, please feel free to register concerns.
See this document for info about what commands tagged team members can give me.

traviscross · 2025-07-30T15:42:03Z

@rfcbot reviewed

rfcbot · 2025-07-30T15:42:12Z

🔔 This is now entering its final comment period, as per the review above. 🔔

Amanieu · 2025-07-30T15:42:52Z

The usual question for target feature stabilizations: Are there any ABI concerns? Is there any potential unsoundness or other problems when mixing code built with and without these features?

No, these just enable a few instructions. They don't expose any additional register or have any impact on ABI.

nikomatsakis · 2025-07-30T15:44:03Z

@rfcbot reviewed

…nieu,traviscross Stabilize `sse4a` and `tbm` target features This PR stabilizes the feature flag `sse4a_target_feature` and `tbm_target_feature` (tracking issue rust-lang#44839). # Public API The 2 `x86` target features `sse4a` and `tbm` Also, these were added in LLVM2.6 and LLVM3.4-rc1, respectively, and as the minimum LLVM required for rustc is LLVM19, we are safe in that front too! As all of the required tasks have been done (adding the target features to rustc, implementing their runtime detection in std_detect and implementing the associated intrinsics in core_arch), these target features can be stabilized now. The intrinsics were stabilized *long* ago, in 1.27.0 Reference PR: - rust-lang/reference#1949 cc `@rust-lang/lang` `@rustbot` label I-lang-nominated r? lang

…nieu,traviscross Stabilize `sse4a` and `tbm` target features This PR stabilizes the feature flag `sse4a_target_feature` and `tbm_target_feature` (tracking issue rust-lang#44839). # Public API The 2 `x86` target features `sse4a` and `tbm` Also, these were added in LLVM2.6 and LLVM3.4-rc1, respectively, and as the minimum LLVM required for rustc is LLVM19, we are safe in that front too! As all of the required tasks have been done (adding the target features to rustc, implementing their runtime detection in std_detect and implementing the associated intrinsics in core_arch), these target features can be stabilized now. The intrinsics were stabilized *long* ago, in 1.27.0 Reference PR: - rust-lang/reference#1949 cc ``@rust-lang/lang`` ``@rustbot`` label I-lang-nominated r? lang

…nieu,traviscross Stabilize `sse4a` and `tbm` target features This PR stabilizes the feature flag `sse4a_target_feature` and `tbm_target_feature` (tracking issue rust-lang#44839). # Public API The 2 `x86` target features `sse4a` and `tbm` Also, these were added in LLVM2.6 and LLVM3.4-rc1, respectively, and as the minimum LLVM required for rustc is LLVM19, we are safe in that front too! As all of the required tasks have been done (adding the target features to rustc, implementing their runtime detection in std_detect and implementing the associated intrinsics in core_arch), these target features can be stabilized now. The intrinsics were stabilized *long* ago, in 1.27.0 Reference PR: - rust-lang/reference#1949 cc ```@rust-lang/lang``` ```@rustbot``` label I-lang-nominated r? lang

…nieu,traviscross Stabilize `sse4a` and `tbm` target features This PR stabilizes the feature flag `sse4a_target_feature` and `tbm_target_feature` (tracking issue rust-lang#44839). # Public API The 2 `x86` target features `sse4a` and `tbm` Also, these were added in LLVM2.6 and LLVM3.4-rc1, respectively, and as the minimum LLVM required for rustc is LLVM19, we are safe in that front too! As all of the required tasks have been done (adding the target features to rustc, implementing their runtime detection in std_detect and implementing the associated intrinsics in core_arch), these target features can be stabilized now. The intrinsics were stabilized *long* ago, in 1.27.0 Reference PR: - rust-lang/reference#1949 cc ````@rust-lang/lang```` ````@rustbot```` label I-lang-nominated r? lang

Rollup of 15 pull requests Successful merges: - #131477 (Apple: Always pass SDK root when linking with `cc`, and pass it via `SDKROOT` env var) - #139806 (std: sys: pal: uefi: Overhaul Time) - #144386 (Extract TraitImplHeader in AST/HIR) - #144542 (Stabilize `sse4a` and `tbm` target features) - #144921 (Don't emit `rustdoc::broken_intra_doc_links` for GitHub-flavored Markdown admonitions like `[!NOTE]`) - #145155 (Port `#[allow_internal_unsafe]` to the new attribute system (attempt 2)) - #145214 (fix: re-enable self-assignment) - #145216 (rustdoc: correct negative-to-implicit discriminant display) - #145238 (Tweak invalid builtin attribute output) - #145249 (Rename entered trace span variables from `_span` to `_trace`) - #145251 (Support using #[unstable_feature_bound] on trait) - #145253 (Document compiler and stdlib in stage1 in `pr-check-2` CI job) - #145260 (Make explicit guarantees about `Vec`’s allocator) - #145263 (Update books) - #145273 (Account for new `assert!` desugaring in `!condition` suggestion) r? `@ghost` `@rustbot` modify labels: rollup

tests/ui/target-feature/gate.rs

fmease · 2025-08-12T02:37:08Z

#145282 (comment)
@bors r-

- remove some stabilized target features from `gate.rs`

sayantn · 2025-08-13T20:39:44Z

@rustbot ready

traviscross · 2025-08-14T04:56:59Z

@bors r=Amanieu,traviscross rollup=iffy

bors · 2025-08-14T04:57:01Z

📌 Commit 100d19c has been approved by Amanieu,traviscross

It is now in the queue for this repository.

bors · 2025-08-14T14:01:15Z

⌛ Testing commit 100d19c with merge be00ea1...

bors · 2025-08-14T17:56:34Z

☀️ Test successful - checks-actions
Approved by: Amanieu,traviscross
Pushing be00ea1 to master...

github-actions · 2025-08-14T17:59:42Z

What is this?

This is an experimental post-merge analysis report that shows differences in test outcomes between the merged PR and its parent PR.

Comparing 30017c3 (parent) -> be00ea1 (this PR)

Test differences

Show 2 test diffs

2 doctest diffs were found. These are ignored, as they are noisy.

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard be00ea1968d8d5afb5d93d2dedeb97a8bba300cb --output-dir test-dashboard

And then open test-dashboard/index.html in your browser to see an overview of all executed tests.

Job duration changes

dist-apple-various: 5096.0s -> 6748.0s (32.4%)
aarch64-apple: 6672.8s -> 5038.9s (-24.5%)
dist-aarch64-apple: 7662.7s -> 6257.0s (-18.3%)
dist-ohos-x86_64: 4180.1s -> 4781.2s (14.4%)
dist-aarch64-msvc: 5735.5s -> 6545.1s (14.1%)
dist-powerpc64le-linux-gnu: 5208.4s -> 5676.4s (9.0%)
dist-armv7-linux: 5086.3s -> 5491.9s (8.0%)
dist-various-1: 3911.2s -> 4218.5s (7.9%)
dist-loongarch64-musl: 5024.7s -> 5418.0s (7.8%)
x86_64-gnu-nopt: 7688.5s -> 7148.5s (-7.0%)

How to interpret the job duration changes?

Job durations can vary a lot, based on the actual runner instance
that executed the job, system noise, invalidated caches, etc. The table above is provided
mostly for t-infra members, for simpler debugging of potential CI slow-downs.

rust-timer · 2025-08-14T19:08:40Z

Finished benchmarking commit (be00ea1): comparison URL.

Overall result: ❌✅ regressions and improvements - please read the text below

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)	0.6%	[0.3%, 1.7%]	8
Improvements ✅ (primary)	-0.8%	[-0.8%, -0.8%]	1
Improvements ✅ (secondary)	-0.2%	[-0.2%, -0.2%]	2
All ❌✅ (primary)	-0.8%	[-0.8%, -0.8%]	1

Max RSS (memory usage)

This benchmark run did not return any relevant results for this metric.

Cycles

Results (primary 2.3%, secondary 2.6%)

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

	mean	range	count
Regressions ❌ (primary)	2.3%	[2.3%, 2.3%]	1
Regressions ❌ (secondary)	2.6%	[1.2%, 3.8%]	6
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	2.3%	[2.3%, 2.3%]	1

Binary size

Results (secondary -0.2%)

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)	0.4%	[0.1%, 1.0%]	3
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.3%	[-0.8%, -0.1%]	9
All ❌✅ (primary)	-	-	0

Bootstrap: 470.205s -> 471.131s (0.20%)
Artifact size: 377.38 MiB -> 377.44 MiB (0.02%)

rustbot assigned petrochenkov Jul 27, 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. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Jul 27, 2025

rustbot added I-lang-nominated Nominated for discussion during a lang team meeting. T-lang Relevant to the language team labels Jul 27, 2025

rustbot assigned nikomatsakis and unassigned petrochenkov Jul 27, 2025

traviscross added the P-lang-drag-1 Lang team prioritization drag level 1. https://rust-lang.zulipchat.com/#narrow/channel/410516-t-lang label Jul 28, 2025

Amanieu approved these changes Jul 28, 2025

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traviscross added the S-waiting-on-documentation Status: Waiting on approved PRs to documentation before merging label Jul 28, 2025

sayantn mentioned this pull request Jul 28, 2025

Add doc for sse4a and tbm rust-lang/reference#1949

Merged

traviscross removed T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Jul 30, 2025

rfcbot added proposed-final-comment-period Proposed to merge/close by relevant subteam, see T-<team> label. Will enter FCP once signed off. disposition-merge This issue / PR is in PFCP or FCP with a disposition to merge it. labels Jul 30, 2025

rfcbot added final-comment-period In the final comment period and will be merged soon unless new substantive objections are raised. and removed proposed-final-comment-period Proposed to merge/close by relevant subteam, see T-<team> label. Will enter FCP once signed off. labels Jul 30, 2025

traviscross removed the S-waiting-on-documentation Status: Waiting on approved PRs to documentation before merging label Jul 30, 2025

traviscross removed the I-lang-nominated Nominated for discussion during a lang team meeting. label Jul 31, 2025

bors added the S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. label Aug 11, 2025

fmease mentioned this pull request Aug 11, 2025

Rollup of 16 pull requests #145280

Closed

fmease mentioned this pull request Aug 12, 2025

Rollup of 15 pull requests #145281

Closed

fmease mentioned this pull request Aug 12, 2025

Rollup of 15 pull requests #145282

Closed

fmease reviewed Aug 12, 2025

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tests/ui/target-feature/gate.rs Outdated Show resolved Hide resolved

bors 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-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Aug 12, 2025

Stabilize sse4a and tbm target features

100d19c

- remove some stabilized target features from `gate.rs`

sayantn force-pushed the stabilize-sse4a-tbm branch from 3200d1f to 100d19c Compare August 13, 2025 20:38

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 Aug 13, 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-review Status: Awaiting review from the assignee but also interested parties. labels Aug 14, 2025

bors added the merged-by-bors This PR was explicitly merged by bors. label Aug 14, 2025

bors merged commit be00ea1 into rust-lang:master Aug 14, 2025
11 checks passed

rustbot added this to the 1.91.0 milestone Aug 14, 2025

rustbot added the perf-regression Performance regression. label Aug 14, 2025

Stabilize sse4a and tbm target features #144542

Stabilize sse4a and tbm target features #144542

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Test differences

Job duration changes

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rust-timer commented Aug 14, 2025

Overall result: ❌✅ regressions and improvements - please read the text below

Instruction count

Max RSS (memory usage)

Cycles

Binary size

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Stabilize `sse4a` and `tbm` target features #144542

Stabilize `sse4a` and `tbm` target features #144542

sayantn commented Jul 27, 2025 •

edited by traviscross

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