rust/compiler/rustc_span
Matthias Krüger 7d63382000
Rollup merge of #145656 - folkertdev:stabilize-s390x-vector, r=Amanieu
Stabilize s390x `vector` target feature and `is_s390x_feature_detected!` macro

closes https://github.com/rust-lang/rust/issues/145649
closes https://github.com/rust-lang/rust/issues/135413
cc: https://github.com/rust-lang/rust/issues/130869
reference PR: https://github.com/rust-lang/reference/pull/1972

# Stabilization report

## Summary

This PR stabilizes the following s390x target features:

- `vector`
- `vector-enhancements-1`
- `vector-enhancements-2`
- `vector-enhancements-3`
- `vector-packed-decimal`
- `vector-packed-decimal-enhancement`
- `vector-packed-decimal-enhancement-2`
- `vector-packed-decimal-enhancement-3`
- `nnp-assist`
- `miscellaneous-extensions-2`
- `miscellaneous-extensions-3`
- `miscellaneous-extensions-4`

Additionally, it stabilizes the `std::arch::is_s390x_feature_detected!` macro itself and stably accepts the target features listed above.

## Tests & ABI details

Only the `vector` target feature changes the ABI, much like e.g. `avx2` it will, depending on the ABI, pass vector types in vector registers. This behavior is tested extensively:

- [tests/assembly-llvm/s390x-vector-abi.rs](22a86f8280/tests/assembly-llvm/s390x-vector-abi.rs)
- [tests/codegen-llvm/s390x-simd.rs](22a86f8280/tests/assembly-llvm/s390x-vector-abi.rs)
- [tests/ui/abi/simd-abi-checks-s390x.rs ](22a86f8280/tests/ui/abi/simd-abi-checks-s390x.rs )

The remaining features don't influence the ABI, they only influence instruction selection. In stdarch we test that the expected instructions are in fact generated when the target feature is enabled.

## Implementation history

For `is_s390x_feature_detected!`:

- https://github.com/rust-lang/stdarch/pull/1699
- https://github.com/rust-lang/rust/pull/138275
- https://github.com/rust-lang/stdarch/pull/1720
- https://github.com/rust-lang/stdarch/pull/1832

For `vector` and friends

- https://github.com/rust-lang/rust/pull/127506
- https://github.com/rust-lang/rust/pull/135630
- https://github.com/rust-lang/rust/pull/141250

## Unresolved questions

There is a fixme in [tests/ui/abi/simd-abi-checks-s390x.rs](22a86f8280/tests/ui/abi/simd-abi-checks-s390x.rs):

```
// FIXME: +soft-float itself doesn't set -vector
//`@[z13_soft_float]` compile-flags: --target s390x-unknown-linux-gnu -C target-cpu=z13 -C target-feature=-vector,+soft-float
//`@[z13_soft_float]` needs-llvm-components: systemz
```

I'm not sure whether that blocks stabilization?

---

The implementation first extracts the listed target features into their own `s390x_target_feature_vector` rust feature, and then stabilizes that. best reviewed commit-by-commit

r? `@Amanieu`
cc `@uweigand`  `@taiki-e`
2025-11-08 15:42:19 +01:00
..
src Rollup merge of #145656 - folkertdev:stabilize-s390x-vector, r=Amanieu 2025-11-08 15:42:19 +01:00
Cargo.toml Revert introduction of [workspace.dependencies]. 2025-09-02 19:12:54 +10:00