Make SIMD intrinsics available in `const`-contexts by sayantn · Pull Request #147521 · rust-lang/rust

sayantn · 2025-10-09T11:46:47Z

successor to #146568, this PR actually makes the SIMD intrinsics const, and modifies the tests to test the const-eval implementations

r? @tgross35 ig (although feel free to reassign, this is not anything targeted really)

rustbot · 2025-10-09T11:46:50Z

Some changes occurred to the platform-builtins intrinsics. Make sure the
LLVM backend as well as portable-simd gets adapted for the changes.

cc @antoyo, @GuillaumeGomez, @bjorn3, @calebzulawski, @programmerjake

The Miri subtree was changed

cc @rust-lang/miri

Some changes occurred to the intrinsics. Make sure the CTFE / Miri interpreter
gets adapted for the changes, if necessary.

cc @rust-lang/miri, @RalfJung, @oli-obk, @lcnr

rustbot · 2025-10-09T11:46:53Z

tgross35 is currently at their maximum review capacity.
They may take a while to respond.

RalfJung · 2025-10-09T14:22:07Z

Cc @Amanieu

programmerjake · 2025-10-09T20:26:17Z

tests/ui/simd/intrinsic/generic-reduction-pass.rs

-        let r: f32 = simd_reduce_mul_unordered(x);
-        assert_eq!(r, -24_f32);
+        let x = f32x4::from_array([1., -2., 3., 4.]);
        let r: f32 = simd_reduce_add_ordered(x, 0.);


I know this wasn't there originally, but maybe we should add a test that requires being added in the proper order to return the right result? something like 1.0e20f32 + 1.0 - 1.0e20 - 1.0 == -1.0

that seems like a nice idea, but I really don't want to add new tests in this PR - this is pretty big by itself anyway

programmerjake

other than that idea for a new test, lgtm

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bors · 2025-11-05T11:46:41Z

☔ The latest upstream changes (presumably #148507) made this pull request unmergeable. Please resolve the merge conflicts.

tests/auxiliary/minisimd.rs

rustbot · 2025-11-10T21:58:10Z

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.

sayantn · 2025-11-14T23:12:50Z

@rustbot reroll

Rerolling as @tgross35 is a bit busy

madsmtm

Haven't looked through all the tests, will wait until we figure out whether we can just overwrite assert_eq!, from a quick glance they look fine (they were also reviewed previously in #146568 by @tgross35).

View changes since this review

tests/auxiliary/minisimd.rs

madsmtm · 2025-11-15T16:19:18Z

library/core/src/intrinsics/simd.rs

 #[rustc_intrinsic]
 #[rustc_nounwind]
-pub unsafe fn simd_add<T>(x: T, y: T) -> T;
+pub const unsafe fn simd_add<T>(x: T, y: T) -> T;


I am unsure of the process here: does this need a compiler FCP to confirm that, yes, we do want t-libs to be able to start depending on these intrinsics being const?

#146568 was reviewed by Ralf, so I guess that's close to as good as it gets in terms of "wg-const-eval is fine with this".

I don't know, @Amanieu do we need to do some kind of libs fcp??

The team in charge of intrinsics is t-lang. They will have to be involved when stabilizing any of this, i.e., when adding rustc_intrinsic_const_stable_indirect to an intrinsic.

For the unstable part, notifying @rust-lang/wg-const-eval is enough. From my side this is fine: the only part that needs closer scrutiny is the fact that these are float operations, but we made them behave just like their scalar equivalents which seems right to me.

Ah so we can continue on this 🎉

tests/auxiliary/minisimd.rs

tests/ui/simd/intrinsic/float-math-pass.rs

library/core/src/intrinsics/simd.rs

tests/ui/simd/intrinsic/float-math-pass.rs

tests/ui/simd/intrinsic/generic-arithmetic-pass.rs

RalfJung · 2025-11-16T20:12:17Z

Haven't looked through all the tests, will wait until we figure out whether we can just overwrite assert_eq!, from a quick glance they look fine (they were also reviewed previously in #146568 by @tgross35).

Trevor left two comments but didn't indicate whether they even looked at the entire rest of the PR.

sayantn · 2025-11-16T20:54:01Z

thanks for your suggestion to shadow assert_eq! @madsmtm, it almost halved the diffcount

@rustbot ready

madsmtm

I've reviewed the tests now, generally happy with them.

Trevor left two comments but didn't indicate whether they even looked at the entire rest of the PR.

Yeah, I should've said "skimmed".

View changes since this review

tests/auxiliary/minisimd.rs

tests/ui/simd/intrinsic/generic-bitmask-pass.rs

tests/ui/simd/intrinsic/generic-cast-pointer-width.rs

tests/ui/simd/intrinsic/generic-gather-scatter-pass.rs

madsmtm · 2025-11-17T00:55:49Z

Thanks for the answers, feel free to r=me when you've rebased, and when we've figured out if we've followed the right process.

sayantn · 2025-11-18T21:16:05Z

@madsmtm what do you think now? @RalfJung said that only wg-const-eval should be pinged for these, and he had no problems with these.

Also, I have squashed the commits, so it should be ready to go now

madsmtm · 2025-11-19T07:52:11Z

I had forgotten about rustc_intrinsic_const_stable_indirect, so I'm fine with this now.

@bors r+ rollup

bors · 2025-11-19T07:52:14Z

📌 Commit 82ff614 has been approved by madsmtm

It is now in the queue for this repository.

Rollup of 7 pull requests Successful merges: - #147171 (recommend using a HashMap if a HashSet's second generic parameter doesn't implement BuildHasher) - #147421 (Add check if span is from macro expansion) - #147521 (Make SIMD intrinsics available in `const`-contexts) - #148201 (Start documenting autodiff activities) - #148797 (feat: Add `bit_width` for unsigned `NonZero<T>`) - #148798 (Match <OsString as Debug>::fmt to that of str) - #149082 (autodiff: update formating, improve examples for the unstable-book) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of #147521 - sayantn:simd-const-intrinsics, r=madsmtm Make SIMD intrinsics available in `const`-contexts successor to #146568, this PR actually makes the SIMD intrinsics `const`, and modifies the tests to test the const-eval implementations r? `@tgross35` ig (although feel free to reassign, this is not anything targeted really)

Rollup of 7 pull requests Successful merges: - rust-lang/rust#147171 (recommend using a HashMap if a HashSet's second generic parameter doesn't implement BuildHasher) - rust-lang/rust#147421 (Add check if span is from macro expansion) - rust-lang/rust#147521 (Make SIMD intrinsics available in `const`-contexts) - rust-lang/rust#148201 (Start documenting autodiff activities) - rust-lang/rust#148797 (feat: Add `bit_width` for unsigned `NonZero<T>`) - rust-lang/rust#148798 (Match <OsString as Debug>::fmt to that of str) - rust-lang/rust#149082 (autodiff: update formating, improve examples for the unstable-book) r? `@ghost` `@rustbot` modify labels: rollup

…adsmtm Make SIMD intrinsics available in `const`-contexts successor to rust-lang#146568, this PR actually makes the SIMD intrinsics `const`, and modifies the tests to test the const-eval implementations r? `@tgross35` ig (although feel free to reassign, this is not anything targeted really)

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 Oct 9, 2025

rustbot assigned tgross35 Oct 9, 2025

sayantn mentioned this pull request Oct 9, 2025

Port the remaining SIMD intrinsics to const-eval #147520

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sayantn force-pushed the simd-const-intrinsics branch from 8c71ce0 to 48324c2 Compare November 3, 2025 22:06

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sayantn mentioned this pull request Nov 3, 2025

Implement SIMD funnel shifts in const-eval/Miri #147534

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oli-obk reviewed Nov 5, 2025

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sayantn force-pushed the simd-const-intrinsics branch from 48324c2 to 76ddb6f Compare November 5, 2025 21:00

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sayantn force-pushed the simd-const-intrinsics branch from 76ddb6f to d1b2151 Compare November 10, 2025 11:14

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Make X86 intrinsics const rust-lang/stdarch#1925

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Make SIMD intrinsics available in const-contexts

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sayantn force-pushed the simd-const-intrinsics branch from d1b2151 to 8715316 Compare November 10, 2025 21:58

rustbot assigned madsmtm and unassigned tgross35 Nov 14, 2025

madsmtm added A-SIMD Area: SIMD (Single Instruction Multiple Data) A-const-eval Area: Constant evaluation, covers all const contexts (static, const fn, ...) labels Nov 15, 2025

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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 Nov 15, 2025

sayantn force-pushed the simd-const-intrinsics branch from 8715316 to e48c21b Compare November 16, 2025 20:52

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 Nov 16, 2025

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Enable const-testing for the ported SIMD intrinsics

82ff614

sayantn force-pushed the simd-const-intrinsics branch from 24bfe49 to 82ff614 Compare November 17, 2025 14:40

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 Nov 19, 2025

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matthiaskrgr mentioned this pull request Nov 19, 2025

Rollup of 7 pull requests #149085

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bors merged commit 714f1ce into rust-lang:main Nov 19, 2025
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rustbot added this to the 1.93.0 milestone Nov 19, 2025

sayantn deleted the simd-const-intrinsics branch November 19, 2025 15:33

sayantn mentioned this pull request Dec 4, 2025

Mark const SIMD intrinsics as indirectly stable #149648

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