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

rfcbot · 2025-08-09T15:42:58Z

The final comment period, with a disposition to merge, as per the review above, is now complete.

As the automated representative of the governance process, I would like to thank the author for their work and everyone else who contributed.

This will be merged soon.

compiler/rustc_feature/src/accepted.rs

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

traviscross · 2025-08-11T21:49:00Z

OK, based on @Amanieu's approval, the completed FCP, and the approved Reference PR,

Add doc for sse4a and tbm reference#1949

we can go ahead and...

@bors r=Amanieu,traviscross rollup

Thanks to @sayantn for pushing this forward.

bors · 2025-08-11T21:49:04Z

📌 Commit 3200d1f has been approved by Amanieu,traviscross

It is now in the queue for this repository.

…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

fmease · 2025-08-12T02:36:50Z

tests/ui/target-feature/gate.rs

Needs --bless'ing due to line number changes.

fmease · 2025-08-12T02:37:08Z

#145282 (comment)
@bors r-

rustbot assigned petrochenkov Jul 27, 2025

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

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traviscross added I-lang-radar Items that are on lang's radar and will need eventual work or consideration. and removed P-lang-drag-1 Lang team prioritization drag level 1. https://rust-lang.zulipchat.com/#narrow/channel/410516-t-lang labels Jul 31, 2025

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Tracking issue for release notes of #144542: Stabilize sse4a and tbm target features #145172

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traviscross requested changes Aug 9, 2025

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sayantn force-pushed the stabilize-sse4a-tbm branch from 3b3c16e to 8d97b08 Compare August 9, 2025 20:49

Stabilize sse4a and tbm target features

3200d1f

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

sayantn force-pushed the stabilize-sse4a-tbm branch from 8d97b08 to 3200d1f Compare August 11, 2025 16:29

sayantn requested a review from traviscross August 11, 2025 16:29

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fmease mentioned this pull request Aug 11, 2025

Rollup of 16 pull requests #145280

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Rollup of 15 pull requests #145281

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Rollup of 15 pull requests #145282

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tests/ui/target-feature/gate.rs

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Needs --bless'ing due to line number changes.

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 #144542

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

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