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Auto merge of #132173 - veluca93:abi_checks, r=RalfJung,compiler-errors

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Emit warning when calling/declaring functions with unavailable vectors.

On some architectures, vector types may have a different ABI depending on whether the relevant target features are enabled. (The ABI when the feature is disabled is often not specified, but LLVM implements some de-facto ABI.)

As discussed in rust-lang/lang-team#235, this turns out to very easily lead to unsound code.

This commit makes it a post-monomorphization future-incompat warning to declare or call functions using those vector types in a context in which the corresponding target features are disabled, if using an ABI for which the difference is relevant. This ensures that these functions are always called with a consistent ABI.

See the [nomination comment](https://github.com/rust-lang/rust/pull/127731#issuecomment-2288558187) for more discussion.

Part of #116558

r? RalfJung
This commit is contained in:
bors 2024-11-10 02:52:25 +00:00
commit 7660aed73d
17 changed files with 514 additions and 61 deletions
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17
compiler/rustc_target/src/target_features.rs
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@ -576,6 +576,13 @@ pub fn all_rust_features() -> impl Iterator<Item = (&'static str, Stability)> {
.map(|(f, s, _)| (f, s))
}
// These arrays represent the least-constraining feature that is required for vector types up to a
// certain size to have their "proper" ABI on each architecture.
// Note that they must be kept sorted by vector size.
const X86_FEATURES_FOR_CORRECT_VECTOR_ABI: &'static [(u64, &'static str)] =
&[(128, "sse"), (256, "avx"), (512, "avx512f")];
const AARCH64_FEATURES_FOR_CORRECT_VECTOR_ABI: &'static [(u64, &'static str)] = &[(128, "neon")];
impl super::spec::Target {
pub fn rust_target_features(&self) -> &'static [(&'static str, Stability, ImpliedFeatures)] {
match &*self.arch {
@ -596,6 +603,16 @@ impl super::spec::Target {
}
}
// Returns None if we do not support ABI checks on the given target yet.
pub fn features_for_correct_vector_abi(&self) -> Option<&'static [(u64, &'static str)]> {
match &*self.arch {
"x86" | "x86_64" => Some(X86_FEATURES_FOR_CORRECT_VECTOR_ABI),
"aarch64" => Some(AARCH64_FEATURES_FOR_CORRECT_VECTOR_ABI),
// FIXME: add support for non-tier1 architectures
_ => None,
}
}
pub fn tied_target_features(&self) -> &'static [&'static [&'static str]] {
match &*self.arch {
"aarch64" | "arm64ec" => AARCH64_TIED_FEATURES,