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aarch64-softfloat: forbid enabling the neon target feature #135160
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r? @Noratrieb rustbot has assigned @Noratrieb. Use |
This change looks good to me. On the off chance that a kernel user comes up in the near future, they can use the "be careful" approach you mentioned in #134375 (comment). |
Yeah, separately building some crates with |
Will that mean something like |
I don't think we should allow target features to do that (I was imagining target modifiers would introduce a new flag for overriding ABI-relevant target features, if there's any good use for that), and so far there was no proposal to allow overriding target modifiers on a per-function basis. The text you quoted referred to |
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I'm happy with this as long as we acknowledge that this is a temporary workaround until LLVM starts handling ABI independently of target features. |
Fully agreed, the ideal end state is that we can use the FPU while sticking to a softfloat ABI (what clang and GCC do for |
Was this discussed by T-lang prior to be approved? I assume yes since I see the release notes label, correct? cc @traviscross probably knows |
We are waiting for t-lang approval, hence the "I-lang-nominated" and "S-waiting-on-team" labels. |
@rfcbot fcp merge |
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. |
I would want relnotes to include a workaround (unfortunately, sounds like it's moving code into another crate and doing some cross-target shenanigans that cargo may not support). Since this is hitting an LLVM limitation it sounds like there's not much else we can do. But if there is any significant breakage we should revisit this decision. |
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@rfcbot fcp cancel |
Rollup merge of rust-lang#141337 - RalfJung:stdarch, r=Amanieu bump stdarch This should unblock rust-lang#135160. r? `@Amanieu`
☔ The latest upstream changes (presumably #141379) made this pull request unmergeable. Please resolve the merge conflicts. |
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@bors try |
… r=<try> aarch64-softfloat: forbid enabling the neon target feature This fixes rust-lang#134375 in a rather crude way, by making [the example](https://godbolt.org/z/r56xWo8nT) not build any more on aarch64-unknown-none-softfloat. That is a breaking change since the "neon" aarch64 target feature is stable, but this is justified as a soundness fix. Note that it's not "neon" which is problematic but "fp-armv8"; however, the two are tied together by rustc. `-Ctarget-feature=+neon` still works, it just causes a warning (but one that we do hope to make a hard error eventually). Only `#[target_feature="neon"]` becomes a hard error with this PR. More work on the LLVM side will be needed before we can let people use neon without impacting the ABI of float values (and, in particular, the ABI used by automatically inserted calls to libm functions, e.g. for int-to-float casts, which rustc has no control over). Nominating for `@rust-lang/lang` since it is a breaking change. As-is this PR doesn't have a warning cycle; the hope is that the aarch64-unknown-none-softfloat target is sufficiently niche that there's no huge fallout and we can easily revert if it causes trouble. A warning cycle could be added but would need some dedicated rather hacky check in the target_feature attribute handling logic. try-job: dist-various-1
☀️ Try build successful - checks-actions |
@bors r=Noratrieb rollup=iffy |
@bors p=4 |
☀️ Test successful - checks-actions |
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 912981a (parent) -> e7f4317 (this PR) Test differencesShow 282 test diffsStage 1
Stage 2
Additionally, 279 doctest diffs were found. These are ignored, as they are noisy. Job group index
Test dashboardRun cargo run --manifest-path src/ci/citool/Cargo.toml -- \
test-dashboard e7f4317ea0e891296163414c6f681ccec976abc3 --output-dir test-dashboard And then open Job duration changes
How to interpret the job duration changes?Job durations can vary a lot, based on the actual runner instance |
Finished benchmarking commit (e7f4317): comparison URL. Overall result: no relevant changes - no action needed@rustbot label: -perf-regression Instruction countThis benchmark run did not return any relevant results for this metric. Max RSS (memory usage)Results (primary -0.7%, secondary 2.6%)This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.
CyclesThis benchmark run did not return any relevant results for this metric. Binary sizeThis benchmark run did not return any relevant results for this metric. Bootstrap: 777.508s -> 778.581s (0.14%) |
bump stdarch This should unblock rust-lang#135160. r? `@Amanieu`
Pkgsrc changes: * Adjust patches to adapt to upstream changes and new versions. * assosicated checksums Upstream changes relative to 1.88.0: Version 1.89.0 (2025-08-07) ========================== Language -------- - [Stabilize explicitly inferred const arguments (`feature(generic_arg_infer)`)] (rust-lang/rust#141610) - [Add a warn-by-default `mismatched_lifetime_syntaxes` lint.] (rust-lang/rust#138677) This lint detects when the same lifetime is referred to by different syntax categories between function arguments and return values, which can be confusing to read, especially in unsafe code. This lint supersedes the warn-by-default `elided_named_lifetimes` lint. - [Expand `unpredictable_function_pointer_comparisons` to also lint on function pointer comparisons in external macros] (rust-lang/rust#134536) - [Make the `dangerous_implicit_autorefs` lint deny-by-default] (rust-lang/rust#141661) - [Stabilize the avx512 target features] (rust-lang/rust#138940) - [Stabilize `kl` and `widekl` target features for x86] (rust-lang/rust#140766) - [Stabilize `sha512`, `sm3` and `sm4` target features for x86] (rust-lang/rust#140767) - [Stabilize LoongArch target features `f`, `d`, `frecipe`, `lasx`, `lbt`, `lsx`, and `lvz`] (rust-lang/rust#135015) - [Remove `i128` and `u128` from `improper_ctypes_definitions`] (rust-lang/rust#137306) - [Stabilize `repr128` (`#[repr(u128)]`, `#[repr(i128)]`)] (rust-lang/rust#138285) - [Allow `#![doc(test(attr(..)))]` everywhere] (rust-lang/rust#140560) - [Extend temporary lifetime extension to also go through tuple struct and tuple variant constructors] (rust-lang/rust#140593) Compiler -------- - [Default to non-leaf frame pointers on aarch64-linux] (rust-lang/rust#140832) - [Enable non-leaf frame pointers for Arm64EC Windows] (rust-lang/rust#140862) - [Set Apple frame pointers by architecture] (rust-lang/rust#141797) Platform Support ---------------- - [Add new Tier-3 targets `loongarch32-unknown-none` and `loongarch32-unknown-none-softfloat`] (rust-lang/rust#142053) Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support. [platform-support-doc]: https://doc.rust-lang.org/rustc/platform-support.html Libraries --------- - [Specify the base path for `file!`] (rust-lang/rust#134442) - [Allow storing `format_args!()` in a variable] (rust-lang/rust#140748) - [Add `#[must_use]` to `[T; N]::map`] (rust-lang/rust#140957) - [Implement `DerefMut` for `Lazy{Cell,Lock}`] (rust-lang/rust#129334) - [Implement `Default` for `array::IntoIter`] (rust-lang/rust#141574) - [Implement `Clone` for `slice::ChunkBy`] (rust-lang/rust#138016) - [Implement `io::Seek` for `io::Take`] (rust-lang/rust#138023) Stabilized APIs --------------- - [`NonZero<char>`] (https://doc.rust-lang.org/stable/std/num/struct.NonZero.html) - Many intrinsics for x86, not enumerated here - [AVX512 intrinsics](rust-lang/rust#111137) - [`SHA512`, `SM3` and `SM4` intrinsics] (rust-lang/rust#126624) - [`File::lock`] (https://doc.rust-lang.org/stable/std/fs/struct.File.html#method.lock) - [`File::lock_shared`] (https://doc.rust-lang.org/stable/std/fs/struct.File.html#method.lock_shared) - [`File::try_lock`] (https://doc.rust-lang.org/stable/std/fs/struct.File.html#method.try_lock) - [`File::try_lock_shared`] (https://doc.rust-lang.org/stable/std/fs/struct.File.html#method.try_lock_shared) - [`File::unlock`] (https://doc.rust-lang.org/stable/std/fs/struct.File.html#method.unlock) - [`NonNull::from_ref`] (https://doc.rust-lang.org/stable/std/ptr/struct.NonNull.html#method.from_ref) - [`NonNull::from_mut`] (https://doc.rust-lang.org/stable/std/ptr/struct.NonNull.html#method.from_mut) - [`NonNull::without_provenance`] (https://doc.rust-lang.org/stable/std/ptr/struct.NonNull.html#method.without_provenance) - [`NonNull::with_exposed_provenance`] (https://doc.rust-lang.org/stable/std/ptr/struct.NonNull.html#method.with_exposed_provenance) - [`NonNull::expose_provenance`] (https://doc.rust-lang.org/stable/std/ptr/struct.NonNull.html#method.expose_provenance) - [`OsString::leak`] (https://doc.rust-lang.org/stable/std/ffi/struct.OsString.html#method.leak) - [`PathBuf::leak`] (https://doc.rust-lang.org/stable/std/path/struct.PathBuf.html#method.leak) - [`Result::flatten`] (https://doc.rust-lang.org/stable/std/result/enum.Result.html#method.flatten) - [`std::os::linux::net::TcpStreamExt::quickack`] (https://doc.rust-lang.org/stable/std/os/linux/net/trait.TcpStreamExt.html#tymethod.quickack) - [`std::os::linux::net::TcpStreamExt::set_quickack`] (https://doc.rust-lang.org/stable/std/os/linux/net/trait.TcpStreamExt.html#tymethod.set_quickack) These previously stable APIs are now stable in const contexts: - [`<[T; N]>::as_mut_slice`] (https://doc.rust-lang.org/stable/std/primitive.array.html#method.as_mut_slice) - [`<[u8]>::eq_ignore_ascii_case`] (https://doc.rust-lang.org/stable/std/primitive.slice.html#impl-%5Bu8%5D/method.eq_ignore_ascii_case) - [`str::eq_ignore_ascii_case`] (https://doc.rust-lang.org/stable/std/primitive.str.html#impl-str/method.eq_ignore_ascii_case) Cargo ----- - [`cargo fix` and `cargo clippy --fix` now default to the same Cargo target selection as other build commands.] (rust-lang/cargo#15192) Previously it would apply to all targets (like binaries, examples, tests, etc.). The `--edition` flag still applies to all targets. - [Stabilize doctest-xcompile.] (rust-lang/cargo#15462) Doctests are now tested when cross-compiling. Just like other tests, it will use the [`runner` setting] (https://doc.rust-lang.org/cargo/reference/config.html#targettriplerunner) to run the tests. If you need to disable tests for a target, you can use the [ignore doctest attribute] (https://doc.rust-lang.org/rustdoc/write-documentation/documentation-tests.html#ignoring-targets) to specify the targets to ignore. Rustdoc ----- - [On mobile, make the sidebar full width and linewrap] (rust-lang/rust#139831). This makes long section and item names much easier to deal with on mobile. Compatibility Notes ------------------- - [Make `missing_fragment_specifier` an unconditional error] (rust-lang/rust#128425) - [Enabling the `neon` target feature on `aarch64-unknown-none-softfloat` causes a warning] (rust-lang/rust#135160) because mixing code with and without that target feature is not properly supported by LLVM - [Sized Hierarchy: Part I](rust-lang/rust#137944) - Introduces a small breaking change affecting `?Sized` bounds on impls on recursive types which contain associated type projections. It is not expected to affect any existing published crates. Can be fixed by refactoring the involved types or opting into the `sized_hierarchy` unstable feature. See the [FCP report] (rust-lang/rust#137944 (comment)) for a code example. - The warn-by-default `elided_named_lifetimes` lint is [superseded by the warn-by-default `mismatched_lifetime_syntaxes` lint.] (rust-lang/rust#138677) - [Error on recursive opaque types earlier in the type checker] (rust-lang/rust#139419) - [Type inference side effects from requiring element types of array repeat expressions are `Copy` are now only available at the end of type checking] (rust-lang/rust#139635) - [The deprecated accidentally-stable `std::intrinsics::{copy,copy_nonoverlapping,write_bytes}` are now proper intrinsics] (rust-lang/rust#139916). There are no debug assertions guarding against UB, and they cannot be coerced to function pointers. - [Remove long-deprecated `std::intrinsics::drop_in_place`] (rust-lang/rust#140151) - [Make well-formedness predicates no longer coinductive] (rust-lang/rust#140208) - [Remove hack when checking impl method compatibility] (rust-lang/rust#140557) - [Remove unnecessary type inference due to built-in trait object impls] (rust-lang/rust#141352) - [Lint against "stdcall", "fastcall", and "cdecl" on non-x86-32 targets] (rust-lang/rust#141435) - [Future incompatibility warnings relating to the never type (`!`) are now reported in dependencies] (rust-lang/rust#141937) - [Ensure `std::ptr::copy_*` intrinsics also perform the static self-init checks] (rust-lang/rust#142575) Internal Changes ---------------- These changes do not affect any public interfaces of Rust, but they represent significant improvements to the performance or internals of rustc and related tools. - [Correctly un-remap compiler sources paths with the `rustc-dev` component] (rust-lang/rust#142377)
This MR contains the following updates: | Package | Update | Change | |---|---|---| | [rust](https://github.com/rust-lang/rust) | minor | `1.88.0` -> `1.89.0` | MR created with the help of [el-capitano/tools/renovate-bot](https://gitlab.com/el-capitano/tools/renovate-bot). **Proposed changes to behavior should be submitted there as MRs.** --- ### Release Notes <details> <summary>rust-lang/rust (rust)</summary> ### [`v1.89.0`](https://github.com/rust-lang/rust/blob/HEAD/RELEASES.md#Version-1890-2025-08-07) [Compare Source](rust-lang/rust@1.88.0...1.89.0) \========================== <a id="1.89.0-Language"></a> ## Language - [Stabilize explicitly inferred const arguments (`feature(generic_arg_infer)`)](rust-lang/rust#141610) - [Add a warn-by-default `mismatched_lifetime_syntaxes` lint.](rust-lang/rust#138677) This lint detects when the same lifetime is referred to by different syntax categories between function arguments and return values, which can be confusing to read, especially in unsafe code. This lint supersedes the warn-by-default `elided_named_lifetimes` lint. - [Expand `unpredictable_function_pointer_comparisons` to also lint on function pointer comparisons in external macros](rust-lang/rust#134536) - [Make the `dangerous_implicit_autorefs` lint deny-by-default](rust-lang/rust#141661) - [Stabilize the avx512 target features](rust-lang/rust#138940) - [Stabilize `kl` and `widekl` target features for x86](rust-lang/rust#140766) - [Stabilize `sha512`, `sm3` and `sm4` target features for x86](rust-lang/rust#140767) - [Stabilize LoongArch target features `f`, `d`, `frecipe`, `lasx`, `lbt`, `lsx`, and `lvz`](rust-lang/rust#135015) - [Remove `i128` and `u128` from `improper_ctypes_definitions`](rust-lang/rust#137306) - [Stabilize `repr128` (`#[repr(u128)]`, `#[repr(i128)]`)](rust-lang/rust#138285) - [Allow `#![doc(test(attr(..)))]` everywhere](rust-lang/rust#140560) - [Extend temporary lifetime extension to also go through tuple struct and tuple variant constructors](rust-lang/rust#140593) - [`extern "C"` functions on the `wasm32-unknown-unknown` target now have a standards compliant ABI](https://blog.rust-lang.org/2025/04/04/c-abi-changes-for-wasm32-unknown-unknown/) <a id="1.89.0-Compiler"></a> ## Compiler - [Default to non-leaf frame pointers on aarch64-linux](rust-lang/rust#140832) - [Enable non-leaf frame pointers for Arm64EC Windows](rust-lang/rust#140862) - [Set Apple frame pointers by architecture](rust-lang/rust#141797) <a id="1.89.0-Platform-Support"></a> ## Platform Support - [Add new Tier-3 targets `loongarch32-unknown-none` and `loongarch32-unknown-none-softfloat`](rust-lang/rust#142053) - [`x86_64-apple-darwin` is in the process of being demoted to Tier 2 with host tools](rust-lang/rfcs#3841) Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support. [platform-support-doc]: https://doc.rust-lang.org/rustc/platform-support.html <a id="1.89.0-Libraries"></a> ## Libraries - [Specify the base path for `file!`](rust-lang/rust#134442) - [Allow storing `format_args!()` in a variable](rust-lang/rust#140748) - [Add `#[must_use]` to `[T; N]::map`](rust-lang/rust#140957) - [Implement `DerefMut` for `Lazy{Cell,Lock}`](rust-lang/rust#129334) - [Implement `Default` for `array::IntoIter`](rust-lang/rust#141574) - [Implement `Clone` for `slice::ChunkBy`](rust-lang/rust#138016) - [Implement `io::Seek` for `io::Take`](rust-lang/rust#138023) <a id="1.89.0-Stabilized-APIs"></a> ## Stabilized APIs - [`NonZero<char>`](https://doc.rust-lang.org/stable/std/num/struct.NonZero.html) - Many intrinsics for x86, not enumerated here - [AVX512 intrinsics](rust-lang/rust#111137) - [`SHA512`, `SM3` and `SM4` intrinsics](rust-lang/rust#126624) - [`File::lock`](https://doc.rust-lang.org/stable/std/fs/struct.File.html#method.lock) - [`File::lock_shared`](https://doc.rust-lang.org/stable/std/fs/struct.File.html#method.lock_shared) - [`File::try_lock`](https://doc.rust-lang.org/stable/std/fs/struct.File.html#method.try_lock) - [`File::try_lock_shared`](https://doc.rust-lang.org/stable/std/fs/struct.File.html#method.try_lock_shared) - [`File::unlock`](https://doc.rust-lang.org/stable/std/fs/struct.File.html#method.unlock) - [`NonNull::from_ref`](https://doc.rust-lang.org/stable/std/ptr/struct.NonNull.html#method.from_ref) - [`NonNull::from_mut`](https://doc.rust-lang.org/stable/std/ptr/struct.NonNull.html#method.from_mut) - [`NonNull::without_provenance`](https://doc.rust-lang.org/stable/std/ptr/struct.NonNull.html#method.without_provenance) - [`NonNull::with_exposed_provenance`](https://doc.rust-lang.org/stable/std/ptr/struct.NonNull.html#method.with_exposed_provenance) - [`NonNull::expose_provenance`](https://doc.rust-lang.org/stable/std/ptr/struct.NonNull.html#method.expose_provenance) - [`OsString::leak`](https://doc.rust-lang.org/stable/std/ffi/struct.OsString.html#method.leak) - [`PathBuf::leak`](https://doc.rust-lang.org/stable/std/path/struct.PathBuf.html#method.leak) - [`Result::flatten`](https://doc.rust-lang.org/stable/std/result/enum.Result.html#method.flatten) - [`std::os::linux::net::TcpStreamExt::quickack`](https://doc.rust-lang.org/stable/std/os/linux/net/trait.TcpStreamExt.html#tymethod.quickack) - [`std::os::linux::net::TcpStreamExt::set_quickack`](https://doc.rust-lang.org/stable/std/os/linux/net/trait.TcpStreamExt.html#tymethod.set_quickack) These previously stable APIs are now stable in const contexts: - [`<[T; N]>::as_mut_slice`](https://doc.rust-lang.org/stable/std/primitive.array.html#method.as_mut_slice) - [`<[u8]>::eq_ignore_ascii_case`](https://doc.rust-lang.org/stable/std/primitive.slice.html#impl-%5Bu8%5D/method.eq_ignore_ascii_case) - [`str::eq_ignore_ascii_case`](https://doc.rust-lang.org/stable/std/primitive.str.html#impl-str/method.eq_ignore_ascii_case) <a id="1.89.0-Cargo"></a> ## Cargo - [`cargo fix` and `cargo clippy --fix` now default to the same Cargo target selection as other build commands.](rust-lang/cargo#15192) Previously it would apply to all targets (like binaries, examples, tests, etc.). The `--edition` flag still applies to all targets. - [Stabilize doctest-xcompile.](rust-lang/cargo#15462) Doctests are now tested when cross-compiling. Just like other tests, it will use the [`runner` setting](https://doc.rust-lang.org/cargo/reference/config.html#targettriplerunner) to run the tests. If you need to disable tests for a target, you can use the [ignore doctest attribute](https://doc.rust-lang.org/rustdoc/write-documentation/documentation-tests.html#ignoring-targets) to specify the targets to ignore. <a id="1.89.0-Rustdoc"></a> ## Rustdoc - [On mobile, make the sidebar full width and linewrap](rust-lang/rust#139831). This makes long section and item names much easier to deal with on mobile. <a id="1.89.0-Compatibility-Notes"></a> ## Compatibility Notes - [Make `missing_fragment_specifier` an unconditional error](rust-lang/rust#128425) - [Enabling the `neon` target feature on `aarch64-unknown-none-softfloat` causes a warning](rust-lang/rust#135160) because mixing code with and without that target feature is not properly supported by LLVM - [Sized Hierarchy: Part I](rust-lang/rust#137944) - Introduces a small breaking change affecting `?Sized` bounds on impls on recursive types which contain associated type projections. It is not expected to affect any existing published crates. Can be fixed by refactoring the involved types or opting into the `sized_hierarchy` unstable feature. See the [FCP report](rust-lang/rust#137944 (comment)) for a code example. - The warn-by-default `elided_named_lifetimes` lint is [superseded by the warn-by-default `mismatched_lifetime_syntaxes` lint.](rust-lang/rust#138677) - [Error on recursive opaque types earlier in the type checker](rust-lang/rust#139419) - [Type inference side effects from requiring element types of array repeat expressions are `Copy` are now only available at the end of type checking](rust-lang/rust#139635) - [The deprecated accidentally-stable `std::intrinsics::{copy,copy_nonoverlapping,write_bytes}` are now proper intrinsics](rust-lang/rust#139916). There are no debug assertions guarding against UB, and they cannot be coerced to function pointers. - [Remove long-deprecated `std::intrinsics::drop_in_place`](rust-lang/rust#140151) - [Make well-formedness predicates no longer coinductive](rust-lang/rust#140208) - [Remove hack when checking impl method compatibility](rust-lang/rust#140557) - [Remove unnecessary type inference due to built-in trait object impls](rust-lang/rust#141352) - [Lint against "stdcall", "fastcall", and "cdecl" on non-x86-32 targets](rust-lang/rust#141435) - [Future incompatibility warnings relating to the never type (`!`) are now reported in dependencies](rust-lang/rust#141937) - [Ensure `std::ptr::copy_*` intrinsics also perform the static self-init checks](rust-lang/rust#142575) - [`extern "C"` functions on the `wasm32-unknown-unknown` target now have a standards compliant ABI](https://blog.rust-lang.org/2025/04/04/c-abi-changes-for-wasm32-unknown-unknown/) <a id="1.89.0-Internal-Changes"></a> ## Internal Changes These changes do not affect any public interfaces of Rust, but they represent significant improvements to the performance or internals of rustc and related tools. - [Correctly un-remap compiler sources paths with the `rustc-dev` component](rust-lang/rust#142377) </details> --- ### Configuration 📅 **Schedule**: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined). 🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied. ♻ **Rebasing**: Whenever MR becomes conflicted, or you tick the rebase/retry checkbox. 🔕 **Ignore**: Close this MR and you won't be reminded about this update again. --- - [ ] <!-- rebase-check -->If you want to rebase/retry this MR, check this box --- This MR has been generated by [Renovate Bot](https://github.com/renovatebot/renovate). <!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiI0MS41NS4yIiwidXBkYXRlZEluVmVyIjoiNDEuNTUuMiIsInRhcmdldEJyYW5jaCI6Im1haW4iLCJsYWJlbHMiOlsiUmVub3ZhdGUgQm90Il19-->
This fixes #134375 in a rather crude way, by making the example not build any more on aarch64-unknown-none-softfloat. That is a breaking change since the "neon" aarch64 target feature is stable, but this is justified as a soundness fix. Note that it's not "neon" which is problematic but "fp-armv8"; however, the two are tied together by rustc.
-Ctarget-feature=+neon
still works, it just causes a warning (but one that we do hope to make a hard error eventually). Only#[target_feature="neon"]
becomes a hard error with this PR.More work on the LLVM side will be needed before we can let people use neon without impacting the ABI of float values (and, in particular, the ABI used by automatically inserted calls to libm functions, e.g. for int-to-float casts, which rustc has no control over).
Nominating for @rust-lang/lang since it is a breaking change. As-is this PR doesn't have a warning cycle; the hope is that the aarch64-unknown-none-softfloat target is sufficiently niche that there's no huge fallout and we can easily revert if it causes trouble. A warning cycle could be added but would need some dedicated rather hacky check in the target_feature attribute handling logic.
try-job: dist-various-1