diff options
Diffstat (limited to 'compiler/rustc_target')
| -rw-r--r-- | compiler/rustc_target/src/target_features.rs | 142 |
1 files changed, 91 insertions, 51 deletions
diff --git a/compiler/rustc_target/src/target_features.rs b/compiler/rustc_target/src/target_features.rs index 3df8f0590a3..eec07a8c351 100644 --- a/compiler/rustc_target/src/target_features.rs +++ b/compiler/rustc_target/src/target_features.rs @@ -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<_, _>>(); 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