bjoernager/rust
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explicitly model that certain ABIs require/forbid certain target features

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This commit is contained in:
Ralf Jung 2024-12-26 18:32:22 +01:00
parent 41b579660c
commit 2bf27e09be
18 changed files with 304 additions and 273 deletions
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52
compiler/rustc_codegen_ssa/src/target_features.rs
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@ -32,7 +32,7 @@ pub(crate) fn from_target_feature_attr(
.emit();
};
let rust_features = tcx.features();
let mut added_target_features = Vec::new();
let (_abi_enable, abi_disable) = tcx.sess.target.abi_required_features();
for item in list {
// Only `enable = ...` is accepted in the meta-item list.
if !item.has_name(sym::enable) {
@ -47,7 +47,7 @@ pub(crate) fn from_target_feature_attr(
};
// We allow comma separation to enable multiple features.
added_target_features.extend(value.as_str().split(',').filter_map(|feature| {
for feature in value.as_str().split(',') {
let Some(stability) = rust_target_features.get(feature) else {
let msg = format!("the feature named `{feature}` is not valid for this target");
let mut err = tcx.dcx().struct_span_err(item.span(), msg);
@ -59,7 +59,7 @@ pub(crate) fn from_target_feature_attr(
}
}
err.emit();
return None;
continue;
};
// Only allow target features whose feature gates have been enabled
@ -80,31 +80,25 @@ pub(crate) fn from_target_feature_attr(
format!("the target feature `{feature}` is currently unstable"),
)
.emit();
} else {
// Add this and the implied features.
let feature_sym = Symbol::intern(feature);
for &name in tcx.implied_target_features(feature_sym) {
// But ensure the ABI does not forbid enabling this.
// Here we do assume that LLVM doesn't add even more implied features
// we don't know about, at least no features that would have ABI effects!
if abi_disable.contains(&name.as_str()) {
tcx.dcx().emit_err(errors::ForbiddenTargetFeatureAttr {
span: item.span(),
feature: name.as_str(),
reason: "this feature is incompatible with the target ABI",
});
}
target_features.push(TargetFeature { name, implied: name != feature_sym })
}
}
Some(Symbol::intern(feature))
}));
}
}
// Add explicit features
target_features.extend(
added_target_features.iter().copied().map(|name| TargetFeature { name, implied: false }),
);
// Add implied features
let mut implied_target_features = UnordSet::new();
for feature in added_target_features.iter() {
implied_target_features.extend(tcx.implied_target_features(*feature).clone());
}
for feature in added_target_features.iter() {
implied_target_features.remove(feature);
}
target_features.extend(
implied_target_features
.into_sorted_stable_ord()
.iter()
.copied()
.map(|name| TargetFeature { name, implied: true }),
)
}
/// Computes the set of target features used in a function for the purposes of
@ -163,9 +157,13 @@ pub(crate) fn provide(providers: &mut Providers) {
.collect()
}
},
implied_target_features: |tcx, feature| {
implied_target_features: |tcx, feature: Symbol| {
let feature = feature.as_str();
UnordSet::from(tcx.sess.target.implied_target_features(std::iter::once(feature)))
.into_sorted_stable_ord()
.into_iter()
.map(|s| Symbol::intern(s))
.collect()
},
asm_target_features,
..*providers