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Reject unsound toggling of Arm atomics-32 target feature #136170

Merged
merged 1 commit into from
Jan 29, 2025
Merged

Reject unsound toggling of Arm atomics-32 target feature #136170

merged 1 commit into from
Jan 29, 2025

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taiki-e
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@taiki-e taiki-e commented Jan 28, 2025

This target feature has the same semantics as RISC-V forced-atomics target feature that already marked as Forbidden (llvm/llvm-project@f5ed0cb) and toggling it can cause ABI incompatibility.

rust/compiler/rustc_target/src/target_features.rs

Lines 479 to 483 in 2f348cb

(
"forced-atomics",
Stability::Forbidden { reason: "unsound because it changes the ABI of atomic operations" },
&[],
),

Comment on feature definition in LLVM also says:

Code built with this feature is not ABI-compatible with code built without this feature, if atomic variables are exposed across the ABI boundary.

r? @workingjubilee or @RalfJung

@rustbot label +O-Arm

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rustbot commented Jan 28, 2025

Could not assign reviewer from: workingjubilee.
User(s) workingjubilee are either the PR author, already assigned, or on vacation. Please use r? to specify someone else to assign.

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rustbot commented Jan 28, 2025

r? @estebank

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

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@rustbot 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. O-Arm Target: 32-bit Arm processors (armv6, armv7, thumb...), including 64-bit Arm in AArch32 state labels Jan 28, 2025
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taiki-e commented Jan 28, 2025

r? @RalfJung

@rustbot rustbot assigned RalfJung and unassigned estebank Jan 28, 2025
@workingjubilee workingjubilee self-assigned this Jan 28, 2025
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Seems fine? Added to our target defs in 89582e8 so yeah, this was always explicitly for our purposes because we want to be able to assume this.

@bors r+ rollup

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bors commented Jan 28, 2025

📌 Commit 7f83f8a has been approved by workingjubilee

It is now in the queue for this repository.

@bors 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 Jan 28, 2025
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Seems like we should document the atomics ABI of thumbv6m_none_eabi somewhere, probably here?

Cc @nikic

@fmease fmease mentioned this pull request Jan 29, 2025
Merged
bors added a commit to rust-lang-ci/rust that referenced this pull request Jan 29, 2025
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Auto merge of rust-lang#136227 - fmease:rollup-ewpvznh, r=fmease
e384432 
Rollup of 9 pull requests

Successful merges:

 - rust-lang#136121 (Deduplicate operand creation between scalars, non-scalars and string patterns)
 - rust-lang#136134 (Fix SIMD codegen tests on LLVM 20)
 - rust-lang#136153 (Locate asan-odr-win with other sanitizer tests)
 - rust-lang#136161 (rustdoc: add nobuild typescript checking to our JS)
 - rust-lang#136166 (interpret: is_alloc_live: check global allocs last)
 - rust-lang#136168 (GCI: Don't try to eval / collect mono items inside overly generic free const items)
 - rust-lang#136170 (Reject unsound toggling of Arm atomics-32 target feature)
 - rust-lang#136176 (Render pattern types nicely in mir dumps)
 - rust-lang#136186 (uefi: process: Fix args)

r? `@ghost`
`@rustbot` modify labels: rollup
bors added a commit to rust-lang-ci/rust that referenced this pull request Jan 29, 2025
@bors
Auto merge of rust-lang#136227 - fmease:rollup-ewpvznh, r=fmease
a1d7676 
Rollup of 9 pull requests

Successful merges:

 - rust-lang#136121 (Deduplicate operand creation between scalars, non-scalars and string patterns)
 - rust-lang#136134 (Fix SIMD codegen tests on LLVM 20)
 - rust-lang#136153 (Locate asan-odr-win with other sanitizer tests)
 - rust-lang#136161 (rustdoc: add nobuild typescript checking to our JS)
 - rust-lang#136166 (interpret: is_alloc_live: check global allocs last)
 - rust-lang#136168 (GCI: Don't try to eval / collect mono items inside overly generic free const items)
 - rust-lang#136170 (Reject unsound toggling of Arm atomics-32 target feature)
 - rust-lang#136176 (Render pattern types nicely in mir dumps)
 - rust-lang#136186 (uefi: process: Fix args)

r? `@ghost`
`@rustbot` modify labels: rollup
@bors bors merged commit 0b1d717 into rust-lang:master Jan 29, 2025
6 checks passed
@rustbot rustbot added this to the 1.86.0 milestone Jan 29, 2025
rust-timer added a commit to rust-lang-ci/rust that referenced this pull request Jan 29, 2025
@rust-timer
Unrolled build for rust-lang#136170
e406274 
Rollup merge of rust-lang#136170 - taiki-e:atomics-32, r=workingjubilee

Reject unsound toggling of Arm atomics-32 target feature

This target feature has the same semantics as RISC-V `forced-atomics` target feature that already marked as Forbidden  (llvm/llvm-project@f5ed0cb) and toggling it can cause ABI incompatibility.

https://github.com/rust-lang/rust/blob/2f348cb7ce4063fa4eb40038e6ada3c5214717bd/compiler/rustc_target/src/target_features.rs#L479-L483

[Comment on feature definition in LLVM](https://github.com/llvm/llvm-project/blob/7109f521975e9cc2e8ba4f52ac2a8e1140bd49b5/llvm/lib/Target/ARM/ARMFeatures.td#L572-L574) also says:

> Code built with this feature is not ABI-compatible with code built without this feature, if atomic variables are exposed across the ABI boundary.

r? `@workingjubilee` or `@RalfJung`

`@rustbot` label +O-Arm
@taiki-e taiki-e deleted the atomics-32 branch January 29, 2025 14:48
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