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mark some target features as 'forbidden' so they cannot be (un)set 

For now, this is just a warning, but should become a hard error in the future
This commit is contained in:
Ralf Jung 2024-09-02 11:45:59 +02:00
parent 2dece5bb62
commit ffad9aac27
23 changed files with 372 additions and 158 deletions
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11
compiler/rustc_codegen_gcc/messages.ftl
View File

@ -8,6 +8,9 @@ codegen_gcc_invalid_minimum_alignment =
codegen_gcc_lto_not_supported =
LTO is not supported. You may get a linker error.
codegen_gcc_forbidden_ctarget_feature =
target feature `{$feature}` cannot be toggled with `-Ctarget-feature`
codegen_gcc_unwinding_inline_asm =
GCC backend does not support unwinding from inline asm
@ -24,11 +27,15 @@ codegen_gcc_lto_dylib = lto cannot be used for `dylib` crate type without `-Zdyl
codegen_gcc_lto_bitcode_from_rlib = failed to get bitcode from object file for LTO ({$gcc_err})
codegen_gcc_unknown_ctarget_feature =
unknown feature specified for `-Ctarget-feature`: `{$feature}`
.note = it is still passed through to the codegen backend
unknown and unstable feature specified for `-Ctarget-feature`: `{$feature}`
.note = it is still passed through to the codegen backend, but use of this feature might be unsound and the behavior of this feature can change in the future
.possible_feature = you might have meant: `{$rust_feature}`
.consider_filing_feature_request = consider filing a feature request
codegen_gcc_unstable_ctarget_feature =
unstable feature specified for `-Ctarget-feature`: `{$feature}`
.note = this feature is not stably supported; its behavior can change in the future
codegen_gcc_missing_features =
add the missing features in a `target_feature` attribute

13
compiler/rustc_codegen_gcc/src/errors.rs
View File

@ -17,6 +17,19 @@ pub(crate) struct UnknownCTargetFeature<'a> {
pub rust_feature: PossibleFeature<'a>,
}
#[derive(Diagnostic)]
#[diag(codegen_gcc_unstable_ctarget_feature)]
#[note]
pub(crate) struct UnstableCTargetFeature<'a> {
pub feature: &'a str,
}
#[derive(Diagnostic)]
#[diag(codegen_gcc_forbidden_ctarget_feature)]
pub(crate) struct ForbiddenCTargetFeature<'a> {
pub feature: &'a str,
}
#[derive(Subdiagnostic)]
pub(crate) enum PossibleFeature<'a> {
#[help(codegen_gcc_possible_feature)]

69
compiler/rustc_codegen_gcc/src/gcc_util.rs
View File

@ -5,10 +5,13 @@ use rustc_codegen_ssa::errors::TargetFeatureDisableOrEnable;
use rustc_data_structures::fx::FxHashMap;
use rustc_middle::bug;
use rustc_session::Session;
use rustc_target::target_features::RUSTC_SPECIFIC_FEATURES;
use rustc_target::target_features::{RUSTC_SPECIFIC_FEATURES, Stability};
use smallvec::{SmallVec, smallvec};
use crate::errors::{PossibleFeature, UnknownCTargetFeature, UnknownCTargetFeaturePrefix};
use crate::errors::{
ForbiddenCTargetFeature, PossibleFeature, UnknownCTargetFeature, UnknownCTargetFeaturePrefix,
UnstableCTargetFeature,
};
/// The list of GCC features computed from CLI flags (`-Ctarget-cpu`, `-Ctarget-feature`,
/// `--target` and similar).
@ -43,7 +46,7 @@ pub(crate) fn global_gcc_features(sess: &Session, diagnostics: bool) -> Vec<Stri
);
// -Ctarget-features
let supported_features = sess.target.supported_target_features();
let known_features = sess.target.rust_target_features();
let mut featsmap = FxHashMap::default();
let feats = sess
.opts
@ -62,37 +65,49 @@ pub(crate) fn global_gcc_features(sess: &Session, diagnostics: bool) -> Vec<Stri
}
};
// Get the backend feature name, if any.
// This excludes rustc-specific features, that do not get passed down to GCC.
let feature = backend_feature_name(s)?;
// Warn against use of GCC specific feature names on the CLI.
if diagnostics && !supported_features.iter().any(|&(v, _, _)| v == feature) {
let rust_feature = supported_features.iter().find_map(|&(rust_feature, _, _)| {
let gcc_features = to_gcc_features(sess, rust_feature);
if gcc_features.contains(&feature) && !gcc_features.contains(&rust_feature) {
Some(rust_feature)
} else {
None
}
});
let unknown_feature = if let Some(rust_feature) = rust_feature {
UnknownCTargetFeature {
feature,
rust_feature: PossibleFeature::Some { rust_feature },
}
} else {
UnknownCTargetFeature { feature, rust_feature: PossibleFeature::None }
};
sess.dcx().emit_warn(unknown_feature);
}
if diagnostics {
let feature_state = known_features.iter().find(|&&(v, _, _)| v == feature);
match feature_state {
None => {
let rust_feature =
known_features.iter().find_map(|&(rust_feature, _, _)| {
let gcc_features = to_gcc_features(sess, rust_feature);
if gcc_features.contains(&feature)
&& !gcc_features.contains(&rust_feature)
{
Some(rust_feature)
} else {
None
}
});
let unknown_feature = if let Some(rust_feature) = rust_feature {
UnknownCTargetFeature {
feature,
rust_feature: PossibleFeature::Some { rust_feature },
}
} else {
UnknownCTargetFeature { feature, rust_feature: PossibleFeature::None }
};
sess.dcx().emit_warn(unknown_feature);
}
Some((_, Stability::Stable, _)) => {}
Some((_, Stability::Unstable(_), _)) => {
// An unstable feature. Warn about using it.
sess.dcx().emit_warn(UnstableCTargetFeature { feature });
}
Some((_, Stability::Forbidden { .. }, _)) => {
sess.dcx().emit_err(ForbiddenCTargetFeature { feature });
}
}
// FIXME(nagisa): figure out how to not allocate a full hashset here.
featsmap.insert(feature, enable_disable == '+');
}
// rustc-specific features do not get passed down to GCC…
if RUSTC_SPECIFIC_FEATURES.contains(&feature) {
return None;
}
// ... otherwise though we run through `to_gcc_features` when
// passing requests down to GCC. This means that all in-language
// features also work on the command line instead of having two

3
compiler/rustc_codegen_gcc/src/lib.rs
View File

@ -491,8 +491,9 @@ pub fn target_features(
) -> Vec<Symbol> {
// TODO(antoyo): use global_gcc_features.
sess.target
.supported_target_features()
.rust_target_features()
.iter()
.filter(|(_, gate, _)| gate.is_supported())
.filter_map(|&(feature, gate, _)| {
if sess.is_nightly_build() || allow_unstable || gate.is_stable() {
Some(feature)

5
compiler/rustc_codegen_llvm/messages.ftl
View File

@ -7,6 +7,11 @@ codegen_llvm_dynamic_linking_with_lto =
codegen_llvm_fixed_x18_invalid_arch = the `-Zfixed-x18` flag is not supported on the `{$arch}` architecture
codegen_llvm_forbidden_ctarget_feature =
target feature `{$feature}` cannot be toggled with `-Ctarget-feature`: {$reason}
.note = this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
codegen_llvm_forbidden_ctarget_feature_issue = for more information, see issue #116344 <https://github.com/rust-lang/rust/issues/116344>
codegen_llvm_from_llvm_diag = {$message}
codegen_llvm_from_llvm_optimization_diag = {$filename}:{$line}:{$column} {$pass_name} ({$kind}): {$message}

9
compiler/rustc_codegen_llvm/src/errors.rs
View File

@ -31,6 +31,15 @@ pub(crate) struct UnstableCTargetFeature<'a> {
pub feature: &'a str,
}
#[derive(Diagnostic)]
#[diag(codegen_llvm_forbidden_ctarget_feature)]
#[note]
#[note(codegen_llvm_forbidden_ctarget_feature_issue)]
pub(crate) struct ForbiddenCTargetFeature<'a> {
pub feature: &'a str,
pub reason: &'a str,
}
#[derive(Subdiagnostic)]
pub(crate) enum PossibleFeature<'a> {
#[help(codegen_llvm_possible_feature)]

117
compiler/rustc_codegen_llvm/src/llvm_util.rs
View File

@ -16,12 +16,12 @@ use rustc_session::Session;
use rustc_session::config::{PrintKind, PrintRequest};
use rustc_span::symbol::Symbol;
use rustc_target::spec::{MergeFunctions, PanicStrategy, SmallDataThresholdSupport};
use rustc_target::target_features::{RUSTC_SPECIAL_FEATURES, RUSTC_SPECIFIC_FEATURES};
use rustc_target::target_features::{RUSTC_SPECIAL_FEATURES, RUSTC_SPECIFIC_FEATURES, Stability};
use crate::back::write::create_informational_target_machine;
use crate::errors::{
FixedX18InvalidArch, InvalidTargetFeaturePrefix, PossibleFeature, UnknownCTargetFeature,
UnknownCTargetFeaturePrefix, UnstableCTargetFeature,
FixedX18InvalidArch, ForbiddenCTargetFeature, InvalidTargetFeaturePrefix, PossibleFeature,
UnknownCTargetFeature, UnknownCTargetFeaturePrefix, UnstableCTargetFeature,
};
use crate::llvm;
@ -280,19 +280,29 @@ pub(crate) fn to_llvm_features<'a>(sess: &Session, s: &'a str) -> Option<LLVMFea
}
}
/// Used to generate cfg variables and apply features
/// Must express features in the way Rust understands them
/// Used to generate cfg variables and apply features.
/// Must express features in the way Rust understands them.
///
/// We do not have to worry about RUSTC_SPECIFIC_FEATURES here, those are handled outside codegen.
pub fn target_features(sess: &Session, allow_unstable: bool) -> Vec<Symbol> {
let mut features = vec![];
let mut features: FxHashSet<Symbol> = Default::default();
// Add base features for the target
// Add base features for the target.
// We do *not* add the -Ctarget-features there, and instead duplicate the logic for that below.
// The reason is that if LLVM considers a feature implied but we do not, we don't want that to
// show up in `cfg`. That way, `cfg` is entirely under our control -- except for the handling of
// the target CPU, that is still expanded to target features (with all their implied features) by
// LLVM.
let target_machine = create_informational_target_machine(sess, true);
// Compute which of the known target features are enabled in the 'base' target machine.
// We only consider "supported" features; "forbidden" features are not reflected in `cfg` as of now.
features.extend(
sess.target
.supported_target_features()
.rust_target_features()
.iter()
.filter(|(_, gate, _)| gate.is_supported())
.filter(|(feature, _, _)| {
// skip checking special features, as LLVM may not understands them
// skip checking special features, as LLVM may not understand them
if RUSTC_SPECIAL_FEATURES.contains(feature) {
return true;
}
@ -323,7 +333,12 @@ pub fn target_features(sess: &Session, allow_unstable: bool) -> Vec<Symbol> {
if enabled {
features.extend(sess.target.implied_target_features(std::iter::once(feature)));
} else {
// We don't care about the order in `features` since the only thing we use it for is the
// `features.contains` below.
#[allow(rustc::potential_query_instability)]
features.retain(|f| {
// Keep a feature if it does not imply `feature`. Or, equivalently,
// remove the reverse-dependencies of `feature`.
!sess.target.implied_target_features(std::iter::once(*f)).contains(&feature)
});
}
@ -331,8 +346,9 @@ pub fn target_features(sess: &Session, allow_unstable: bool) -> Vec<Symbol> {
// Filter enabled features based on feature gates
sess.target
.supported_target_features()
.rust_target_features()
.iter()
.filter(|(_, gate, _)| gate.is_supported())
.filter_map(|&(feature, gate, _)| {
if sess.is_nightly_build() || allow_unstable || gate.is_stable() {
Some(feature)
@ -392,9 +408,13 @@ fn print_target_features(out: &mut String, sess: &Session, tm: &llvm::TargetMach
let mut known_llvm_target_features = FxHashSet::<&'static str>::default();
let mut rustc_target_features = sess
.target
.supported_target_features()
.rust_target_features()
.iter()
.filter_map(|(feature, _gate, _implied)| {
.filter_map(|(feature, gate, _implied)| {
if !gate.is_supported() {
// Only list (experimentally) supported features.
return None;
}
// LLVM asserts that these are sorted. LLVM and Rust both use byte comparison for these
// strings.
let llvm_feature = to_llvm_features(sess, *feature)?.llvm_feature_name;
@ -567,7 +587,7 @@ pub(crate) fn global_llvm_features(
// -Ctarget-features
if !only_base_features {
let supported_features = sess.target.supported_target_features();
let known_features = sess.target.rust_target_features();
let mut featsmap = FxHashMap::default();
// insert implied features
@ -601,50 +621,53 @@ pub(crate) fn global_llvm_features(
}
};
// Get the backend feature name, if any.
// This excludes rustc-specific features, which do not get passed to LLVM.
let feature = backend_feature_name(sess, s)?;
// Warn against use of LLVM specific feature names and unstable features on the CLI.
if diagnostics {
let feature_state = supported_features.iter().find(|&&(v, _, _)| v == feature);
if feature_state.is_none() {
let rust_feature =
supported_features.iter().find_map(|&(rust_feature, _, _)| {
let llvm_features = to_llvm_features(sess, rust_feature)?;
if llvm_features.contains(feature)
&& !llvm_features.contains(rust_feature)
{
Some(rust_feature)
} else {
None
let feature_state = known_features.iter().find(|&&(v, _, _)| v == feature);
match feature_state {
None => {
let rust_feature =
known_features.iter().find_map(|&(rust_feature, _, _)| {
let llvm_features = to_llvm_features(sess, rust_feature)?;
if llvm_features.contains(feature)
&& !llvm_features.contains(rust_feature)
{
Some(rust_feature)
} else {
None
}
});
let unknown_feature = if let Some(rust_feature) = rust_feature {
UnknownCTargetFeature {
feature,
rust_feature: PossibleFeature::Some { rust_feature },
}
});
let unknown_feature = if let Some(rust_feature) = rust_feature {
UnknownCTargetFeature {
feature,
rust_feature: PossibleFeature::Some { rust_feature },
}
} else {
UnknownCTargetFeature { feature, rust_feature: PossibleFeature::None }
};
sess.dcx().emit_warn(unknown_feature);
} else if feature_state
.is_some_and(|(_name, feature_gate, _implied)| !feature_gate.is_stable())
{
// An unstable feature. Warn about using it.
sess.dcx().emit_warn(UnstableCTargetFeature { feature });
} else {
UnknownCTargetFeature {
feature,
rust_feature: PossibleFeature::None,
}
};
sess.dcx().emit_warn(unknown_feature);
}
Some((_, Stability::Stable, _)) => {}
Some((_, Stability::Unstable(_), _)) => {
// An unstable feature. Warn about using it.
sess.dcx().emit_warn(UnstableCTargetFeature { feature });
}
Some((_, Stability::Forbidden { reason }, _)) => {
sess.dcx().emit_warn(ForbiddenCTargetFeature { feature, reason });
}
}
}
if diagnostics {
// FIXME(nagisa): figure out how to not allocate a full hashset here.
featsmap.insert(feature, enable_disable == '+');
}
// rustc-specific features do not get passed down to LLVM…
if RUSTC_SPECIFIC_FEATURES.contains(&feature) {
return None;
}
// ... otherwise though we run through `to_llvm_features` when
// We run through `to_llvm_features` when
// passing requests down to LLVM. This means that all in-language
// features also work on the command line instead of having two
// different names when the LLVM name and the Rust name differ.

3
compiler/rustc_codegen_ssa/messages.ftl
View File

@ -58,6 +58,9 @@ codegen_ssa_failed_to_write = failed to write {$path}: {$error}
codegen_ssa_field_associated_value_expected = associated value expected for `{$name}`
codegen_ssa_forbidden_target_feature_attr =
target feature `{$feature}` cannot be toggled with `#[target_feature]`: {$reason}
codegen_ssa_ignoring_emit_path = ignoring emit path because multiple .{$extension} files were produced
codegen_ssa_ignoring_output = ignoring -o because multiple .{$extension} files were produced

14
compiler/rustc_codegen_ssa/src/codegen_attrs.rs
View File

@ -20,8 +20,8 @@ use rustc_span::symbol::Ident;
use rustc_span::{Span, sym};
use rustc_target::spec::{SanitizerSet, abi};
use crate::errors::{self, MissingFeatures, TargetFeatureDisableOrEnable};
use crate::target_features::{check_target_feature_trait_unsafe, from_target_feature};
use crate::errors;
use crate::target_features::{check_target_feature_trait_unsafe, from_target_feature_attr};
fn linkage_by_name(tcx: TyCtxt<'_>, def_id: LocalDefId, name: &str) -> Linkage {
use rustc_middle::mir::mono::Linkage::*;
@ -73,7 +73,7 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_BUILTINS;
}
let supported_target_features = tcx.supported_target_features(LOCAL_CRATE);
let rust_target_features = tcx.rust_target_features(LOCAL_CRATE);
let mut inline_span = None;
let mut link_ordinal_span = None;
@ -281,10 +281,10 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
check_target_feature_trait_unsafe(tcx, did, attr.span);
}
}
from_target_feature(
from_target_feature_attr(
tcx,
attr,
supported_target_features,
rust_target_features,
&mut codegen_fn_attrs.target_features,
);
}
@ -676,10 +676,10 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
.next()
.map_or_else(|| tcx.def_span(did), |a| a.span);
tcx.dcx()
.create_err(TargetFeatureDisableOrEnable {
.create_err(errors::TargetFeatureDisableOrEnable {
features,
span: Some(span),
missing_features: Some(MissingFeatures),
missing_features: Some(errors::MissingFeatures),
})
.emit();
}

9
compiler/rustc_codegen_ssa/src/errors.rs
View File

@ -1018,6 +1018,15 @@ pub(crate) struct TargetFeatureSafeTrait {
pub def: Span,
}
#[derive(Diagnostic)]
#[diag(codegen_ssa_forbidden_target_feature_attr)]
pub struct ForbiddenTargetFeatureAttr<'a> {
#[primary_span]
pub span: Span,
pub feature: &'a str,
pub reason: &'a str,
}
#[derive(Diagnostic)]
#[diag(codegen_ssa_failed_to_get_layout)]
pub struct FailedToGetLayout<'tcx> {

54
compiler/rustc_codegen_ssa/src/target_features.rs
View File

@ -11,13 +11,16 @@ use rustc_middle::ty::TyCtxt;
use rustc_session::parse::feature_err;
use rustc_span::Span;
use rustc_span::symbol::{Symbol, sym};
use rustc_target::target_features::{self, Stability};
use crate::errors;
pub(crate) fn from_target_feature(
/// Compute the enabled target features from the `#[target_feature]` function attribute.
/// Enabled target features are added to `target_features`.
pub(crate) fn from_target_feature_attr(
tcx: TyCtxt<'_>,
attr: &ast::Attribute,
supported_target_features: &UnordMap<String, Option<Symbol>>,
rust_target_features: &UnordMap<String, target_features::Stability>,
target_features: &mut Vec<TargetFeature>,
) {
let Some(list) = attr.meta_item_list() else { return };
@ -46,12 +49,12 @@ pub(crate) fn from_target_feature(
// We allow comma separation to enable multiple features.
added_target_features.extend(value.as_str().split(',').filter_map(|feature| {
let Some(feature_gate) = supported_target_features.get(feature) else {
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);
err.span_label(item.span(), format!("`{feature}` is not valid for this target"));
if let Some(stripped) = feature.strip_prefix('+') {
let valid = supported_target_features.contains_key(stripped);
let valid = rust_target_features.contains_key(stripped);
if valid {
err.help("consider removing the leading `+` in the feature name");
}
@ -61,18 +64,31 @@ pub(crate) fn from_target_feature(
};
// Only allow target features whose feature gates have been enabled.
let allowed = match feature_gate.as_ref().copied() {
Some(name) => rust_features.enabled(name),
None => true,
let allowed = match stability {
Stability::Forbidden { .. } => false,
Stability::Stable => true,
Stability::Unstable(name) => rust_features.enabled(*name),
};
if !allowed {
feature_err(
&tcx.sess,
feature_gate.unwrap(),
item.span(),
format!("the target feature `{feature}` is currently unstable"),
)
.emit();
match stability {
Stability::Stable => unreachable!(),
&Stability::Unstable(lang_feature_name) => {
feature_err(
&tcx.sess,
lang_feature_name,
item.span(),
format!("the target feature `{feature}` is currently unstable"),
)
.emit();
}
Stability::Forbidden { reason } => {
tcx.dcx().emit_err(errors::ForbiddenTargetFeatureAttr {
span: item.span(),
feature,
reason,
});
}
}
}
Some(Symbol::intern(feature))
}));
@ -138,20 +154,20 @@ pub(crate) fn check_target_feature_trait_unsafe(tcx: TyCtxt<'_>, id: LocalDefId,
pub(crate) fn provide(providers: &mut Providers) {
*providers = Providers {
supported_target_features: |tcx, cnum| {
rust_target_features: |tcx, cnum| {
assert_eq!(cnum, LOCAL_CRATE);
if tcx.sess.opts.actually_rustdoc {
// rustdoc needs to be able to document functions that use all the features, so
// whitelist them all
rustc_target::target_features::all_known_features()
.map(|(a, b)| (a.to_string(), b.as_feature_name()))
rustc_target::target_features::all_rust_features()
.map(|(a, b)| (a.to_string(), b))
.collect()
} else {
tcx.sess
.target
.supported_target_features()
.rust_target_features()
.iter()
.map(|&(a, b, _)| (a.to_string(), b.as_feature_name()))
.map(|&(a, b, _)| (a.to_string(), b))
.collect()
}
},

5
compiler/rustc_middle/src/query/mod.rs
View File

@ -2185,10 +2185,11 @@ rustc_queries! {
desc { "computing autoderef types for `{}`", goal.canonical.value.value }
}
query supported_target_features(_: CrateNum) -> &'tcx UnordMap<String, Option<Symbol>> {
/// Returns the Rust target features for the current target. These are not always the same as LLVM target features!
query rust_target_features(_: CrateNum) -> &'tcx UnordMap<String, rustc_target::target_features::Stability> {
arena_cache
eval_always
desc { "looking up supported target features" }
desc { "looking up Rust target features" }
}
query implied_target_features(feature: Symbol) -> &'tcx Vec<Symbol> {

5
compiler/rustc_session/src/config/cfg.rs
View File

@ -370,8 +370,9 @@ impl CheckCfg {
ins!(sym::sanitizer_cfi_normalize_integers, no_values);
ins!(sym::target_feature, empty_values).extend(
rustc_target::target_features::all_known_features()
.map(|(f, _sb)| f)
rustc_target::target_features::all_rust_features()
.filter(|(_, s)| s.is_supported())
.map(|(f, _s)| f)
.chain(rustc_target::target_features::RUSTC_SPECIFIC_FEATURES.iter().cloned())
.map(Symbol::intern),
);

142
compiler/rustc_target/src/target_features.rs
View File

@ -1,10 +1,17 @@
//! Declares Rust's target feature names for each target.
//! Note that these are similar to but not always identical to LLVM's feature names,
//! and Rust adds some features that do not correspond to LLVM features at all.
use rustc_data_structures::fx::{FxHashMap, FxHashSet};
use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
use rustc_span::symbol::{Symbol, sym};
/// Features that control behaviour of rustc, rather than the codegen.
/// These exist globally and are not in the target-specific lists below.
pub const RUSTC_SPECIFIC_FEATURES: &[&str] = &["crt-static"];
/// Features that require special handling when passing to LLVM.
/// Features that require special handling when passing to LLVM:
/// these are target-specific (i.e., must also be listed in the target-specific list below)
/// but do not correspond to an LLVM target feature.
pub const RUSTC_SPECIAL_FEATURES: &[&str] = &["backchain"];
/// Stability information for target features.
@ -16,26 +23,47 @@ pub enum Stability {
/// This target feature is unstable; using it in `#[target_feature]` or `#[cfg(target_feature)]`
/// requires enabling the given nightly feature.
Unstable(Symbol),
/// This feature can not be set via `-Ctarget-feature` or `#[target_feature]`, it can only be set in the basic
/// target definition. Used in particular for features that change the floating-point ABI.
Forbidden { reason: &'static str },
}
use Stability::*;
impl Stability {
pub fn as_feature_name(self) -> Option<Symbol> {
impl<CTX> HashStable<CTX> for Stability {
#[inline]
fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
std::mem::discriminant(self).hash_stable(hcx, hasher);
match self {
Stable => None,
Unstable(s) => Some(s),
Stable => {}
Unstable(sym) => {
sym.hash_stable(hcx, hasher);
}
Forbidden { .. } => {}
}
}
}
impl Stability {
pub fn is_stable(self) -> bool {
matches!(self, Stable)
}
/// Forbidden features are not supported.
pub fn is_supported(self) -> bool {
!matches!(self, Forbidden { .. })
}
}
// Here we list target features that rustc "understands": they can be used in `#[target_feature]`
// and `#[cfg(target_feature)]`. They also do not trigger any warnings when used with
// `-Ctarget-feature`.
//
// Note that even unstable (and even entirely unlisted) features can be used with `-Ctarget-feature`
// on stable. Using a feature not on the list of Rust target features only emits a warning.
// Only `cfg(target_feature)` and `#[target_feature]` actually do any stability gating.
// `cfg(target_feature)` for unstable features just works on nightly without any feature gate.
// `#[target_feature]` requires a feature gate.
//
// When adding features to the below lists
// check whether they're named already elsewhere in rust
// e.g. in stdarch and whether the given name matches LLVM's
@ -46,17 +74,27 @@ impl Stability {
// per-function level, since we would then allow safe calls from functions with `+soft-float` to
// functions without that feature!
//
// When adding a new feature, be particularly mindful of features that affect function ABIs. Those
// need to be treated very carefully to avoid introducing unsoundness! This often affects features
// that enable/disable hardfloat support (see https://github.com/rust-lang/rust/issues/116344 for an
// example of this going wrong), but features enabling new SIMD registers are also a concern (see
// https://github.com/rust-lang/rust/issues/116558 for an example of this going wrong).
// It is important for soundness that features allowed here do *not* change the function call ABI.
// For example, disabling the `x87` feature on x86 changes how scalar floats are passed as
// arguments, so enabling toggling that feature would be unsound. In fact, since `-Ctarget-feature`
// will just allow unknown features (with a warning), we have to explicitly list features that change
// the ABI as `Forbidden` to ensure using them causes an error. Note that this is only effective if
// such features can never be toggled via `-Ctarget-cpu`! If that is ever a possibility, we will need
// extra checks ensuring that the LLVM-computed target features for a CPU did not (un)set a
// `Forbidden` feature. See https://github.com/rust-lang/rust/issues/116344 for some more context.
// FIXME: add such "forbidden" features for non-x86 targets.
//
// The one exception to features that change the ABI is features that enable larger vector
// registers. Those are permitted to be listed here. This is currently unsound (see
// https://github.com/rust-lang/rust/issues/116558); in the future we will have to ensure that
// functions can only use such vectors as arguments/return types if the corresponding target feature
// is enabled.
//
// Stabilizing a target feature requires t-lang approval.
type ImpliedFeatures = &'static [&'static str];
const ARM_ALLOWED_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
const ARM_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
// tidy-alphabetical-start
("aclass", Unstable(sym::arm_target_feature), &[]),
("aes", Unstable(sym::arm_target_feature), &["neon"]),
@ -70,6 +108,7 @@ const ARM_ALLOWED_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
("neon", Unstable(sym::arm_target_feature), &["vfp3"]),
("rclass", Unstable(sym::arm_target_feature), &[]),
("sha2", Unstable(sym::arm_target_feature), &["neon"]),
("soft-float", Forbidden { reason: "unsound because it changes float ABI" }, &[]),
// This is needed for inline assembly, but shouldn't be stabilized as-is
// since it should be enabled per-function using #[instruction_set], not
// #[target_feature].
@ -87,9 +126,10 @@ const ARM_ALLOWED_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
("vfp4", Unstable(sym::arm_target_feature), &["vfp3"]),
("virtualization", Unstable(sym::arm_target_feature), &[]),
// tidy-alphabetical-end
// FIXME: need to also forbid turning off `fpregs` on hardfloat targets
];
const AARCH64_ALLOWED_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
const AARCH64_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
// tidy-alphabetical-start
// FEAT_AES & FEAT_PMULL
("aes", Stable, &["neon"]),
@ -277,7 +317,7 @@ const AARCH64_TIED_FEATURES: &[&[&str]] = &[
&["paca", "pacg"], // Together these represent `pauth` in LLVM
];
const X86_ALLOWED_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
const X86_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
// tidy-alphabetical-start
("adx", Stable, &[]),
("aes", Stable, &["sse2"]),
@ -328,6 +368,7 @@ const X86_ALLOWED_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
("sha512", Unstable(sym::sha512_sm_x86), &["avx2"]),
("sm3", Unstable(sym::sha512_sm_x86), &["avx"]),
("sm4", Unstable(sym::sha512_sm_x86), &["avx2"]),
("soft-float", Forbidden { reason: "unsound because it changes float ABI" }, &[]),
("sse", Stable, &[]),
("sse2", Stable, &["sse"]),
("sse3", Stable, &["sse2"]),
@ -344,16 +385,17 @@ const X86_ALLOWED_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
("xsaveopt", Stable, &["xsave"]),
("xsaves", Stable, &["xsave"]),
// tidy-alphabetical-end
// FIXME: need to also forbid turning off `x87` on hardfloat targets
];
const HEXAGON_ALLOWED_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
const HEXAGON_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
// tidy-alphabetical-start
("hvx", Unstable(sym::hexagon_target_feature), &[]),
("hvx-length128b", Unstable(sym::hexagon_target_feature), &["hvx"]),
// tidy-alphabetical-end
];
const POWERPC_ALLOWED_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
const POWERPC_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
// tidy-alphabetical-start
("altivec", Unstable(sym::powerpc_target_feature), &[]),
("partword-atomics", Unstable(sym::powerpc_target_feature), &[]),
@ -367,7 +409,7 @@ const POWERPC_ALLOWED_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
// tidy-alphabetical-end
];
const MIPS_ALLOWED_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
const MIPS_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
// tidy-alphabetical-start
("fp64", Unstable(sym::mips_target_feature), &[]),
("msa", Unstable(sym::mips_target_feature), &[]),
@ -375,7 +417,7 @@ const MIPS_ALLOWED_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
// tidy-alphabetical-end
];
const RISCV_ALLOWED_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
const RISCV_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
// tidy-alphabetical-start
("a", Stable, &["zaamo", "zalrsc"]),
("c", Stable, &[]),
@ -415,7 +457,7 @@ const RISCV_ALLOWED_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
// tidy-alphabetical-end
];
const WASM_ALLOWED_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
const WASM_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
// tidy-alphabetical-start
("atomics", Unstable(sym::wasm_target_feature), &[]),
("bulk-memory", Stable, &[]),
@ -431,10 +473,10 @@ const WASM_ALLOWED_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
// tidy-alphabetical-end
];
const BPF_ALLOWED_FEATURES: &[(&str, Stability, ImpliedFeatures)] =
const BPF_FEATURES: &[(&str, Stability, ImpliedFeatures)] =
&[("alu32", Unstable(sym::bpf_target_feature), &[])];
const CSKY_ALLOWED_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
const CSKY_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
// tidy-alphabetical-start
("10e60", Unstable(sym::csky_target_feature), &["7e10"]),
("2e3", Unstable(sym::csky_target_feature), &["e2"]),
@ -481,7 +523,7 @@ const CSKY_ALLOWED_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
// tidy-alphabetical-end
];
const LOONGARCH_ALLOWED_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
const LOONGARCH_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
// tidy-alphabetical-start
("d", Unstable(sym::loongarch_target_feature), &["f"]),
("f", Unstable(sym::loongarch_target_feature), &[]),
@ -495,7 +537,7 @@ const LOONGARCH_ALLOWED_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
// tidy-alphabetical-end
];
const IBMZ_ALLOWED_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
const IBMZ_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
// tidy-alphabetical-start
("backchain", Unstable(sym::s390x_target_feature), &[]),
("vector", Unstable(sym::s390x_target_feature), &[]),
@ -506,41 +548,39 @@ const IBMZ_ALLOWED_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
/// primitives may be documented.
///
/// IMPORTANT: If you're adding another feature list above, make sure to add it to this iterator!
pub fn all_known_features() -> impl Iterator<Item = (&'static str, Stability)> {
pub fn all_rust_features() -> impl Iterator<Item = (&'static str, Stability)> {
std::iter::empty()
.chain(ARM_ALLOWED_FEATURES.iter())
.chain(AARCH64_ALLOWED_FEATURES.iter())
.chain(X86_ALLOWED_FEATURES.iter())
.chain(HEXAGON_ALLOWED_FEATURES.iter())
.chain(POWERPC_ALLOWED_FEATURES.iter())
.chain(MIPS_ALLOWED_FEATURES.iter())
.chain(RISCV_ALLOWED_FEATURES.iter())
.chain(WASM_ALLOWED_FEATURES.iter())
.chain(BPF_ALLOWED_FEATURES.iter())
.chain(CSKY_ALLOWED_FEATURES)
.chain(LOONGARCH_ALLOWED_FEATURES)
.chain(IBMZ_ALLOWED_FEATURES)
.chain(ARM_FEATURES.iter())
.chain(AARCH64_FEATURES.iter())
.chain(X86_FEATURES.iter())
.chain(HEXAGON_FEATURES.iter())
.chain(POWERPC_FEATURES.iter())
.chain(MIPS_FEATURES.iter())
.chain(RISCV_FEATURES.iter())
.chain(WASM_FEATURES.iter())
.chain(BPF_FEATURES.iter())
.chain(CSKY_FEATURES)
.chain(LOONGARCH_FEATURES)
.chain(IBMZ_FEATURES)
.cloned()
.map(|(f, s, _)| (f, s))
}
impl super::spec::Target {
pub fn supported_target_features(
&self,
) -> &'static [(&'static str, Stability, ImpliedFeatures)] {
pub fn rust_target_features(&self) -> &'static [(&'static str, Stability, ImpliedFeatures)] {
match &*self.arch {
"arm" => ARM_ALLOWED_FEATURES,
"aarch64" | "arm64ec" => AARCH64_ALLOWED_FEATURES,
"x86" | "x86_64" => X86_ALLOWED_FEATURES,
"hexagon" => HEXAGON_ALLOWED_FEATURES,
"mips" | "mips32r6" | "mips64" | "mips64r6" => MIPS_ALLOWED_FEATURES,
"powerpc" | "powerpc64" => POWERPC_ALLOWED_FEATURES,
"riscv32" | "riscv64" => RISCV_ALLOWED_FEATURES,
"wasm32" | "wasm64" => WASM_ALLOWED_FEATURES,
"bpf" => BPF_ALLOWED_FEATURES,
"csky" => CSKY_ALLOWED_FEATURES,
"loongarch64" => LOONGARCH_ALLOWED_FEATURES,
"s390x" => IBMZ_ALLOWED_FEATURES,
"arm" => ARM_FEATURES,
"aarch64" | "arm64ec" => AARCH64_FEATURES,
"x86" | "x86_64" => X86_FEATURES,
"hexagon" => HEXAGON_FEATURES,
"mips" | "mips32r6" | "mips64" | "mips64r6" => MIPS_FEATURES,
"powerpc" | "powerpc64" => POWERPC_FEATURES,
"riscv32" | "riscv64" => RISCV_FEATURES,
"wasm32" | "wasm64" => WASM_FEATURES,
"bpf" => BPF_FEATURES,
"csky" => CSKY_FEATURES,
"loongarch64" => LOONGARCH_FEATURES,
"s390x" => IBMZ_FEATURES,
_ => &[],
}
}
@ -557,7 +597,7 @@ impl super::spec::Target {
base_features: impl Iterator<Item = Symbol>,
) -> FxHashSet<Symbol> {
let implied_features = self
.supported_target_features()
.rust_target_features()
.iter()
.map(|(f, _, i)| (Symbol::intern(f), i))
.collect::<FxHashMap<_, _>>();

0
tests/ui/auxiliary/using-target-feature-unstable.rs → tests/ui/target-feature/auxiliary/using-target-feature-unstable.rs
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12
tests/ui/target-feature/forbidden-target-feature-attribute.rs Normal file
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@ -0,0 +1,12 @@
//@ compile-flags: --target=x86_64-unknown-linux-gnu --crate-type=lib
//@ needs-llvm-components: x86
#![feature(no_core, lang_items)]
#![no_std]
#![no_core]
#[lang = "sized"]
pub trait Sized {}
#[target_feature(enable = "soft-float")]
//~^ERROR: cannot be toggled with
pub unsafe fn my_fun() {}

8
tests/ui/target-feature/forbidden-target-feature-attribute.stderr Normal file
View File

@ -0,0 +1,8 @@
error: target feature `soft-float` cannot be toggled with `#[target_feature]`: unsound because it changes float ABI
--> $DIR/forbidden-target-feature-attribute.rs:10:18
|
LL | #[target_feature(enable = "soft-float")]
| ^^^^^^^^^^^^^^^^^^^^^
error: aborting due to 1 previous error

15
tests/ui/target-feature/forbidden-target-feature-cfg.rs Normal file
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@ -0,0 +1,15 @@
//@ compile-flags: --target=x86_64-unknown-none --crate-type=lib
//@ needs-llvm-components: x86
//@ check-pass
#![feature(no_core, lang_items)]
#![no_std]
#![no_core]
#![allow(unexpected_cfgs)]
#[lang = "sized"]
pub trait Sized {}
// The compile_error macro does not exist, so if the `cfg` evaluates to `true` this
// complains about the missing macro rather than showing the error... but that's good enough.
#[cfg(target_feature = "soft-float")]
compile_error!("the soft-float feature should not be exposed in `cfg`");

11
tests/ui/target-feature/forbidden-target-feature-flag-disable.rs Normal file
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@ -0,0 +1,11 @@
//@ compile-flags: --target=x86_64-unknown-linux-gnu --crate-type=lib
//@ needs-llvm-components: x86
//@ compile-flags: -Ctarget-feature=-soft-float
// For now this is just a warning.
//@ build-pass
#![feature(no_core, lang_items)]
#![no_std]
#![no_core]
#[lang = "sized"]
pub trait Sized {}

7
tests/ui/target-feature/forbidden-target-feature-flag-disable.stderr Normal file
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@ -0,0 +1,7 @@
warning: target feature `soft-float` cannot be toggled with `-Ctarget-feature`: unsound because it changes float ABI
|
= note: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
= note: for more information, see issue #116344 <https://github.com/rust-lang/rust/issues/116344>
warning: 1 warning emitted

11
tests/ui/target-feature/forbidden-target-feature-flag.rs Normal file
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@ -0,0 +1,11 @@
//@ compile-flags: --target=x86_64-unknown-linux-gnu --crate-type=lib
//@ needs-llvm-components: x86
//@ compile-flags: -Ctarget-feature=+soft-float
// For now this is just a warning.
//@ build-pass
#![feature(no_core, lang_items)]
#![no_std]
#![no_core]
#[lang = "sized"]
pub trait Sized {}

7
tests/ui/target-feature/forbidden-target-feature-flag.stderr Normal file
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@ -0,0 +1,7 @@
warning: target feature `soft-float` cannot be toggled with `-Ctarget-feature`: unsound because it changes float ABI
|
= note: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
= note: for more information, see issue #116344 <https://github.com/rust-lang/rust/issues/116344>
warning: 1 warning emitted

0
tests/ui/using-target-feature-unstable.rs → tests/ui/target-feature/using-target-feature-unstable.rs
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