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Clarify safety requirements for SIMD shl/shr and masked load/store - #159402

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Clarify safety requirements for SIMD shl/shr and masked load/store#159402
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yilin0518:fix_simd_2

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@yilin0518yilin0518 commented Jul 16, 2026

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This PR fixes some safety documentation of SIMD functions. These functions are talked in Zulip topic: Maybe some safety doc need fixs in intrinsics::simd.

Brief explanation: simd_shl and simd_shr may accept a rhs of negative value, but that value will be interpreted as unsigned and thus violate the requirement that rhs is less than <int>::BITS. So it's better to add a supplement that rhs must be in 0..<int>::BITS. Also, the simd_shl refer that shifting in sign bits for signed types, but left shift always shifts in zero bits.

And simd_masked_load and simd_masked_store need to explicitly state that the corresponding ptr must be readable/writable as if by ptr::read/write, refering to portable-simd::core_simd::load_select_ptr and portable-simd::core_simd::store_select_ptr

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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

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

@rustbotrustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Jul 16, 2026
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programmerjake
programmerjake reviewed Jul 16, 2026
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lgtm

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@bors r+

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📌 Commit cbd88d9 has been approved by programmerjake

It is now in the queue for this repository.

@rust-borsrust-borsBot 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 16, 2026
jhpratt added a commit to jhpratt/rust that referenced this pull request Jul 17, 2026
@jhpratt
Rollup merge ofrust-lang#159402- yilin0518:fix_simd_2, r=programmer…
2a5e3a0
…jake
Clarify safety requirements for SIMD shl/shr and masked load/store
This PR fixes some safety documentation of SIMD functions. These functions are talked in Zulip topic: [Maybe some safety doc need fixs in intrinsics::simd](https://rust-lang.zulipchat.com/#narrow/channel/131828-t-compiler/topic/Maybe.20some.20safety.20doc.20need.20fixs.20in.20intrinsics.3A.3Asimd/with/609693756).
Brief explanation: `simd_shl` and `simd_shr` may accept a `rhs` of negative value, but that value will be interpreted as unsigned and thus violate the requirement that `rhs` is less than `<int>::BITS`. So it's better to add a supplement that `rhs` must be in 0..`<int>::BITS`. Also, the `simd_shl` refer that `shifting in sign bits for signed types`, but left shift always shifts in zero bits.
And `simd_masked_load` and `simd_masked_store` need to explicitly state that the corresponding `ptr` must be readable/writable as if by `ptr::read/write`, refering to [portable-simd::core_simd::load_select_ptr](https://doc.rust-lang.org/src/core/portable-simd/crates/core_simd/src/vector.rs.html#451) and [portable-simd::core_simd::store_select_ptr](https://doc.rust-lang.org/src/core/portable-simd/crates/core_simd/src/vector.rs.html#710)
@jhprattjhpratt mentioned this pull request Jul 17, 2026
Closed
rust-borsBot pushed a commit that referenced this pull request Jul 17, 2026
@bors
Auto merge of#159414- jhpratt:rollup-7nyG9i0, r=jhpratt
ab7f753
Rollup of 10 pull requests
Successful merges:
- #156977 (interpret: properly check for inhabitedness of nested references)
- #159365 (fix: point at method call chain when a return-position `impl Trait` assoc type diverges)
- #159402 (Clarify safety requirements for SIMD shl/shr and masked load/store)
- #159410 (rustdoc: remove old `--emit` types)
- #159302 (Implement `Debug` helpers via `Cell`)
- #159386 (add a fallback for `fmuladdf*`)
- #159391 (Update tests for LLVM 23)
- #159400 (Update books)
- #159401 (Gate `tests/debuginfo/function-call.rs` on min GDB 15.1)
- #159404 ([aarch64][win] Pass oversized c-variadic args indirectly on Arm64EC)
JonathanBrouwer added a commit to JonathanBrouwer/rust that referenced this pull request Jul 17, 2026
@JonathanBrouwer
Rollup merge ofrust-lang#159402- yilin0518:fix_simd_2, r=programmer…
c2c019c
…jake
Clarify safety requirements for SIMD shl/shr and masked load/store
This PR fixes some safety documentation of SIMD functions. These functions are talked in Zulip topic: [Maybe some safety doc need fixs in intrinsics::simd](https://rust-lang.zulipchat.com/#narrow/channel/131828-t-compiler/topic/Maybe.20some.20safety.20doc.20need.20fixs.20in.20intrinsics.3A.3Asimd/with/609693756).
Brief explanation: `simd_shl` and `simd_shr` may accept a `rhs` of negative value, but that value will be interpreted as unsigned and thus violate the requirement that `rhs` is less than `<int>::BITS`. So it's better to add a supplement that `rhs` must be in 0..`<int>::BITS`. Also, the `simd_shl` refer that `shifting in sign bits for signed types`, but left shift always shifts in zero bits.
And `simd_masked_load` and `simd_masked_store` need to explicitly state that the corresponding `ptr` must be readable/writable as if by `ptr::read/write`, refering to [portable-simd::core_simd::load_select_ptr](https://doc.rust-lang.org/src/core/portable-simd/crates/core_simd/src/vector.rs.html#451) and [portable-simd::core_simd::store_select_ptr](https://doc.rust-lang.org/src/core/portable-simd/crates/core_simd/src/vector.rs.html#710)
@JonathanBrouwerJonathanBrouwer mentioned this pull request Jul 17, 2026
Closed
rust-borsBot pushed a commit that referenced this pull request Jul 17, 2026
@bors
Auto merge of#159422- JonathanBrouwer:rollup-fyk9b5T, r=JonathanBro…
3ac07ba
…uwer
Rollup of 10 pull requests
Successful merges:
- #159365 (fix: point at method call chain when a return-position `impl Trait` assoc type diverges)
- #159402 (Clarify safety requirements for SIMD shl/shr and masked load/store)
- #159410 (rustdoc: remove old `--emit` types)
- #159302 (Implement `Debug` helpers via `Cell`)
- #159386 (add a fallback for `fmuladdf*`)
- #159391 (Update tests for LLVM 23)
- #159400 (Update books)
- #159401 (Gate `tests/debuginfo/function-call.rs` on min GDB 15.1)
- #159404 ([aarch64][win] Pass oversized c-variadic args indirectly on Arm64EC)
- #159405 (Manually implement Clone for GrowableBitSet)
JonathanBrouwer added a commit to JonathanBrouwer/rust that referenced this pull request Jul 17, 2026
@JonathanBrouwer
Rollup merge ofrust-lang#159402- yilin0518:fix_simd_2, r=programmer…
4c301c1
…jake
Clarify safety requirements for SIMD shl/shr and masked load/store
This PR fixes some safety documentation of SIMD functions. These functions are talked in Zulip topic: [Maybe some safety doc need fixs in intrinsics::simd](https://rust-lang.zulipchat.com/#narrow/channel/131828-t-compiler/topic/Maybe.20some.20safety.20doc.20need.20fixs.20in.20intrinsics.3A.3Asimd/with/609693756).
Brief explanation: `simd_shl` and `simd_shr` may accept a `rhs` of negative value, but that value will be interpreted as unsigned and thus violate the requirement that `rhs` is less than `<int>::BITS`. So it's better to add a supplement that `rhs` must be in 0..`<int>::BITS`. Also, the `simd_shl` refer that `shifting in sign bits for signed types`, but left shift always shifts in zero bits.
And `simd_masked_load` and `simd_masked_store` need to explicitly state that the corresponding `ptr` must be readable/writable as if by `ptr::read/write`, refering to [portable-simd::core_simd::load_select_ptr](https://doc.rust-lang.org/src/core/portable-simd/crates/core_simd/src/vector.rs.html#451) and [portable-simd::core_simd::store_select_ptr](https://doc.rust-lang.org/src/core/portable-simd/crates/core_simd/src/vector.rs.html#710)
@JonathanBrouwerJonathanBrouwer mentioned this pull request Jul 17, 2026
Closed
rust-borsBot pushed a commit that referenced this pull request Jul 17, 2026
@bors
Auto merge of#159437- JonathanBrouwer:rollup-6Vo34je, r=JonathanBro…
d34058c
…uwer
Rollup of 16 pull requests
Successful merges:
- #150732 (Convert `-Ctarget-cpu` into a target-modifier for AVR, AMDGCN and NVPTX )
- #159301 (Update Enzyme to handle LLVM23)
- #159365 (fix: point at method call chain when a return-position `impl Trait` assoc type diverges)
- #159402 (Clarify safety requirements for SIMD shl/shr and masked load/store)
- #159410 (rustdoc: remove old `--emit` types)
- #158398 (Comment about empty run_passes, fixup of #158040)
- #158843 (Fix ICE in `write_interface` when the interface file can't be written)
- #159302 (Implement `Debug` helpers via `Cell`)
- #159332 (Honor field-level lint attributes in non_snake_case)
- #159386 (add a fallback for `fmuladdf*`)
- #159391 (Update tests for LLVM 23)
- #159400 (Update books)
- #159401 (Gate `tests/debuginfo/function-call.rs` on min GDB 15.1)
- #159404 ([aarch64][win] Pass oversized c-variadic args indirectly on Arm64EC)
- #159405 (Manually implement Clone for GrowableBitSet)
- #159415 (rustdoc: rename the doc parts metadata params)
@JonathanBrouwerJonathanBrouwer mentioned this pull request Jul 17, 2026
Merged
rust-borsBot pushed a commit that referenced this pull request Jul 17, 2026
@bors
Auto merge of#159444- JonathanBrouwer:rollup-sLmd8Fq, r=JonathanBro…
421875f
…uwer
Rollup of 17 pull requests
Successful merges:
- #159301 (Update Enzyme to handle LLVM23)
- #159365 (fix: point at method call chain when a return-position `impl Trait` assoc type diverges)
- #159402 (Clarify safety requirements for SIMD shl/shr and masked load/store)
- #159408 (rustc_data_structures: Expand documentation for rustc jobserver APIs)
- #159410 (rustdoc: remove old `--emit` types)
- #158398 (Comment about empty run_passes, fixup of #158040)
- #158843 (Fix ICE in `write_interface` when the interface file can't be written)
- #159302 (Implement `Debug` helpers via `Cell`)
- #159332 (Honor field-level lint attributes in non_snake_case)
- #159340 (Rename `errors.rs` file to `diagnostics.rs` (14/N))
- #159386 (add a fallback for `fmuladdf*`)
- #159391 (Update tests for LLVM 23)
- #159400 (Update books)
- #159401 (Gate `tests/debuginfo/function-call.rs` on min GDB 15.1)
- #159404 ([aarch64][win] Pass oversized c-variadic args indirectly on Arm64EC)
- #159405 (Manually implement Clone for GrowableBitSet)
- #159415 (rustdoc: rename the doc parts metadata params)
@rust-bors
rust-borsBot merged commit 6369474 into rust-lang:mainJul 17, 2026
13 checks passed
@rustbotrustbot added this to the 1.99.0 milestone Jul 17, 2026
rust-timer added a commit that referenced this pull request Jul 17, 2026
@rust-timer
Unrolled build for#159402
928fc44
Rollup merge of #159402 - yilin0518:fix_simd_2, r=programmerjake
Clarify safety requirements for SIMD shl/shr and masked load/store
This PR fixes some safety documentation of SIMD functions. These functions are talked in Zulip topic: [Maybe some safety doc need fixs in intrinsics::simd](https://rust-lang.zulipchat.com/#narrow/channel/131828-t-compiler/topic/Maybe.20some.20safety.20doc.20need.20fixs.20in.20intrinsics.3A.3Asimd/with/609693756).
Brief explanation: `simd_shl` and `simd_shr` may accept a `rhs` of negative value, but that value will be interpreted as unsigned and thus violate the requirement that `rhs` is less than `<int>::BITS`. So it's better to add a supplement that `rhs` must be in 0..`<int>::BITS`. Also, the `simd_shl` refer that `shifting in sign bits for signed types`, but left shift always shifts in zero bits.
And `simd_masked_load` and `simd_masked_store` need to explicitly state that the corresponding `ptr` must be readable/writable as if by `ptr::read/write`, refering to [portable-simd::core_simd::load_select_ptr](https://doc.rust-lang.org/src/core/portable-simd/crates/core_simd/src/vector.rs.html#451) and [portable-simd::core_simd::store_select_ptr](https://doc.rust-lang.org/src/core/portable-simd/crates/core_simd/src/vector.rs.html#710)
Kobzol pushed a commit to Kobzol/rustc_codegen_cranelift that referenced this pull request Jul 23, 2026
@bors
Auto merge of #159444 - JonathanBrouwer:rollup-sLmd8Fq, r=JonathanBro…
f8e65ac
…uwer
Rollup of 17 pull requests
Successful merges:
- rust-lang/rust#159301 (Update Enzyme to handle LLVM23)
- rust-lang/rust#159365 (fix: point at method call chain when a return-position `impl Trait` assoc type diverges)
- rust-lang/rust#159402 (Clarify safety requirements for SIMD shl/shr and masked load/store)
- rust-lang/rust#159408 (rustc_data_structures: Expand documentation for rustc jobserver APIs)
- rust-lang/rust#159410 (rustdoc: remove old `--emit` types)
- rust-lang/rust#158398 (Comment about empty run_passes, fixup of rust-lang/rust#158040)
- rust-lang/rust#158843 (Fix ICE in `write_interface` when the interface file can't be written)
- rust-lang/rust#159302 (Implement `Debug` helpers via `Cell`)
- rust-lang/rust#159332 (Honor field-level lint attributes in non_snake_case)
- rust-lang/rust#159340 (Rename `errors.rs` file to `diagnostics.rs` (14/N))
- rust-lang/rust#159386 (add a fallback for `fmuladdf*`)
- rust-lang/rust#159391 (Update tests for LLVM 23)
- rust-lang/rust#159400 (Update books)
- rust-lang/rust#159401 (Gate `tests/debuginfo/function-call.rs` on min GDB 15.1)
- rust-lang/rust#159404 ([aarch64][win] Pass oversized c-variadic args indirectly on Arm64EC)
- rust-lang/rust#159405 (Manually implement Clone for GrowableBitSet)
- rust-lang/rust#159415 (rustdoc: rename the doc parts metadata params)
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