diff options
Diffstat (limited to 'compiler/rustc_target/src/target_features.rs')
| -rw-r--r-- | compiler/rustc_target/src/target_features.rs | 190 |
1 files changed, 164 insertions, 26 deletions
diff --git a/compiler/rustc_target/src/target_features.rs b/compiler/rustc_target/src/target_features.rs index 29d3f826a15..5372437b0d2 100644 --- a/compiler/rustc_target/src/target_features.rs +++ b/compiler/rustc_target/src/target_features.rs @@ -3,7 +3,7 @@ //! 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}; +use rustc_span::{Symbol, sym}; use crate::spec::Target; @@ -20,7 +20,7 @@ pub const RUSTC_SPECIAL_FEATURES: &[&str] = &["backchain"]; /// `Toggleability` is the type storing whether (un)stable features can be toggled: /// this is initially a function since it can depend on `Target`, but for stable hashing /// it needs to be something hashable to we have to make the type generic. -#[derive(Debug, Clone, Copy)] +#[derive(Debug, Clone)] pub enum Stability<Toggleability> { /// This target feature is stable, it can be used in `#[target_feature]` and /// `#[cfg(target_feature)]`. @@ -39,16 +39,26 @@ pub enum Stability<Toggleability> { allow_toggle: Toggleability, }, /// This feature can not be set via `-Ctarget-feature` or `#[target_feature]`, it can only be - /// set in the basic target definition. It is never set in `cfg(target_feature)`. Used in + /// set in the target spec. It is never set in `cfg(target_feature)`. Used in /// particular for features that change the floating-point ABI. Forbidden { reason: &'static str }, } -/// `Stability` where `allow_toggle` has not been computed yet. /// Returns `Ok` if the toggle is allowed, `Err` with an explanation of not. -pub type StabilityUncomputed = Stability<fn(&Target) -> Result<(), &'static str>>; +/// The `bool` indicates whether the feature is being enabled (`true`) or disabled. +pub type AllowToggleUncomputed = fn(&Target, bool) -> Result<(), &'static str>; + +/// The computed result of whether a feature can be enabled/disabled on the current target. +#[derive(Debug, Clone)] +pub struct AllowToggleComputed { + enable: Result<(), &'static str>, + disable: Result<(), &'static str>, +} + +/// `Stability` where `allow_toggle` has not been computed yet. +pub type StabilityUncomputed = Stability<AllowToggleUncomputed>; /// `Stability` where `allow_toggle` has already been computed. -pub type StabilityComputed = Stability<Result<(), &'static str>>; +pub type StabilityComputed = Stability<AllowToggleComputed>; impl<CTX, Toggleability: HashStable<CTX>> HashStable<CTX> for Stability<Toggleability> { #[inline] @@ -69,11 +79,20 @@ impl<CTX, Toggleability: HashStable<CTX>> HashStable<CTX> for Stability<Toggleab } } +impl<CTX> HashStable<CTX> for AllowToggleComputed { + #[inline] + fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) { + let AllowToggleComputed { enable, disable } = self; + enable.hash_stable(hcx, hasher); + disable.hash_stable(hcx, hasher); + } +} + impl<Toggleability> Stability<Toggleability> { /// Returns whether the feature can be used in `cfg(target_feature)` ever. /// (It might still be nightly-only even if this returns `true`, so make sure to also check /// `requires_nightly`.) - pub fn in_cfg(self) -> bool { + pub fn in_cfg(&self) -> bool { !matches!(self, Stability::Forbidden { .. }) } @@ -85,8 +104,8 @@ impl<Toggleability> Stability<Toggleability> { /// Before calling this, ensure the feature is even permitted for this use: /// - for `#[target_feature]`/`-Ctarget-feature`, check `allow_toggle()` /// - for `cfg(target_feature)`, check `in_cfg` - pub fn requires_nightly(self) -> Option<Symbol> { - match self { + pub fn requires_nightly(&self) -> Option<Symbol> { + match *self { Stability::Unstable { nightly_feature, .. } => Some(nightly_feature), Stability::Stable { .. } => None, Stability::Forbidden { .. } => panic!("forbidden features should not reach this far"), @@ -95,35 +114,49 @@ impl<Toggleability> Stability<Toggleability> { } impl StabilityUncomputed { - pub fn compute_toggleability(self, target: &Target) -> StabilityComputed { + pub fn compute_toggleability(&self, target: &Target) -> StabilityComputed { use Stability::*; - match self { - Stable { allow_toggle } => Stable { allow_toggle: allow_toggle(target) }, + let compute = |f: AllowToggleUncomputed| AllowToggleComputed { + enable: f(target, true), + disable: f(target, false), + }; + match *self { + Stable { allow_toggle } => Stable { allow_toggle: compute(allow_toggle) }, Unstable { nightly_feature, allow_toggle } => { - Unstable { nightly_feature, allow_toggle: allow_toggle(target) } + Unstable { nightly_feature, allow_toggle: compute(allow_toggle) } } Forbidden { reason } => Forbidden { reason }, } } + + pub fn toggle_allowed(&self, target: &Target, enable: bool) -> Result<(), &'static str> { + use Stability::*; + match *self { + Stable { allow_toggle } => allow_toggle(target, enable), + Unstable { allow_toggle, .. } => allow_toggle(target, enable), + Forbidden { reason } => Err(reason), + } + } } impl StabilityComputed { /// Returns whether the feature may be toggled via `#[target_feature]` or `-Ctarget-feature`. /// (It might still be nightly-only even if this returns `true`, so make sure to also check /// `requires_nightly`.) - pub fn allow_toggle(self) -> Result<(), &'static str> { - match self { + pub fn toggle_allowed(&self, enable: bool) -> Result<(), &'static str> { + let allow_toggle = match self { Stability::Stable { allow_toggle } => allow_toggle, Stability::Unstable { allow_toggle, .. } => allow_toggle, - Stability::Forbidden { reason } => Err(reason), - } + Stability::Forbidden { reason } => return Err(reason), + }; + if enable { allow_toggle.enable } else { allow_toggle.disable } } } // Constructors for the list below, defaulting to "always allow toggle". -const STABLE: StabilityUncomputed = Stability::Stable { allow_toggle: |_target| Ok(()) }; +const STABLE: StabilityUncomputed = Stability::Stable { allow_toggle: |_target, _enable| Ok(()) }; const fn unstable(nightly_feature: Symbol) -> StabilityUncomputed { - Stability::Unstable { nightly_feature, allow_toggle: |_target| Ok(()) } + Stability::Unstable { nightly_feature, allow_toggle: |_target, _enable| Ok(()) } } // Here we list target features that rustc "understands": they can be used in `#[target_feature]` @@ -184,7 +217,7 @@ const ARM_FEATURES: &[(&str, StabilityUncomputed, ImpliedFeatures)] = &[ "fpregs", Stability::Unstable { nightly_feature: sym::arm_target_feature, - allow_toggle: |target: &Target| { + allow_toggle: |target: &Target, _enable| { // Only allow toggling this if the target has `soft-float` set. With `soft-float`, // `fpregs` isn't needed so changing it cannot affect the ABI. if target.has_feature("soft-float") { @@ -257,6 +290,7 @@ const AARCH64_FEATURES: &[(&str, StabilityUncomputed, ImpliedFeatures)] = &[ ("flagm", STABLE, &[]), // FEAT_FLAGM2 ("flagm2", unstable(sym::aarch64_unstable_target_feature), &[]), + ("fp-armv8", Stability::Forbidden { reason: "Rust ties `fp-armv8` to `neon`" }, &[]), // FEAT_FP16 // Rust ties FP and Neon: https://github.com/rust-lang/rust/pull/91608 ("fp16", STABLE, &["neon"]), @@ -292,7 +326,28 @@ const AARCH64_FEATURES: &[(&str, StabilityUncomputed, ImpliedFeatures)] = &[ // FEAT_MTE & FEAT_MTE2 ("mte", STABLE, &[]), // FEAT_AdvSimd & FEAT_FP - ("neon", STABLE, &[]), + ( + "neon", + Stability::Stable { + allow_toggle: |target, enable| { + if target.abi == "softfloat" { + // `neon` has no ABI implications for softfloat targets, we can allow this. + Ok(()) + } else if enable + && !target.has_neg_feature("fp-armv8") + && !target.has_neg_feature("neon") + { + // neon is enabled by default, and has not been disabled, so enabling it again + // is redundant and we can permit it. Forbidding this would be a breaking change + // since this feature is stable. + Ok(()) + } else { + Err("unsound on hard-float targets because it changes float ABI") + } + }, + }, + &[], + ), // FEAT_PAUTH (address authentication) ("paca", STABLE, &[]), // FEAT_PAUTH (generic authentication) @@ -481,7 +536,7 @@ const X86_FEATURES: &[(&str, StabilityUncomputed, ImpliedFeatures)] = &[ "x87", Stability::Unstable { nightly_feature: sym::x87_target_feature, - allow_toggle: |target: &Target| { + allow_toggle: |target: &Target, _enable| { // Only allow toggling this if the target has `soft-float` set. With `soft-float`, // `fpregs` isn't needed so changing it cannot affect the ABI. if target.has_feature("soft-float") { @@ -535,9 +590,76 @@ const RISCV_FEATURES: &[(&str, StabilityUncomputed, ImpliedFeatures)] = &[ // tidy-alphabetical-start ("a", STABLE, &["zaamo", "zalrsc"]), ("c", STABLE, &[]), - ("d", unstable(sym::riscv_target_feature), &["f"]), - ("e", unstable(sym::riscv_target_feature), &[]), - ("f", unstable(sym::riscv_target_feature), &[]), + ( + "d", + Stability::Unstable { + nightly_feature: sym::riscv_target_feature, + allow_toggle: |target, enable| match &*target.llvm_abiname { + "ilp32d" | "lp64d" if !enable => { + // The ABI requires the `d` feature, so it cannot be disabled. + Err("feature is required by ABI") + } + "ilp32e" if enable => { + // ilp32e is incompatible with features that need aligned load/stores > 32 bits, + // like `d`. + Err("feature is incompatible with ABI") + } + _ => Ok(()), + }, + }, + &["f"], + ), + ( + "e", + Stability::Unstable { + // Given that this is a negative feature, consider this before stabilizing: + // does it really make sense to enable this feature in an individual + // function with `#[target_feature]`? + nightly_feature: sym::riscv_target_feature, + allow_toggle: |target, enable| { + match &*target.llvm_abiname { + _ if !enable => { + // Disabling this feature means we can use more registers (x16-x31). + // The "e" ABIs treat them as caller-save, so it is safe to use them only + // in some parts of a program while the rest doesn't know they even exist. + // On other ABIs, the feature is already disabled anyway. + Ok(()) + } + "ilp32e" | "lp64e" => { + // Embedded ABIs should already have the feature anyway, it's fine to enable + // it again from an ABI perspective. + Ok(()) + } + _ => { + // *Not* an embedded ABI. Enabling `e` is invalid. + Err("feature is incompatible with ABI") + } + } + }, + }, + &[], + ), + ( + "f", + Stability::Unstable { + nightly_feature: sym::riscv_target_feature, + allow_toggle: |target, enable| { + match &*target.llvm_abiname { + "ilp32f" | "ilp32d" | "lp64f" | "lp64d" if !enable => { + // The ABI requires the `f` feature, so it cannot be disabled. + Err("feature is required by ABI") + } + _ => Ok(()), + } + }, + }, + &[], + ), + ( + "forced-atomics", + Stability::Forbidden { reason: "unsound because it changes the ABI of atomic operations" }, + &[], + ), ("m", STABLE, &[]), ("relax", unstable(sym::riscv_target_feature), &[]), ("unaligned-scalar-mem", unstable(sym::riscv_target_feature), &[]), @@ -668,6 +790,20 @@ const SPARC_FEATURES: &[(&str, StabilityUncomputed, ImpliedFeatures)] = &[ // tidy-alphabetical-end ]; +const M68K_FEATURES: &[(&str, StabilityUncomputed, ImpliedFeatures)] = &[ + // tidy-alphabetical-start + ("isa-68000", unstable(sym::m68k_target_feature), &[]), + ("isa-68010", unstable(sym::m68k_target_feature), &["isa-68000"]), + ("isa-68020", unstable(sym::m68k_target_feature), &["isa-68010"]), + ("isa-68030", unstable(sym::m68k_target_feature), &["isa-68020"]), + ("isa-68040", unstable(sym::m68k_target_feature), &["isa-68030", "isa-68882"]), + ("isa-68060", unstable(sym::m68k_target_feature), &["isa-68040"]), + // FPU + ("isa-68881", unstable(sym::m68k_target_feature), &[]), + ("isa-68882", unstable(sym::m68k_target_feature), &["isa-68881"]), + // tidy-alphabetical-end +]; + /// When rustdoc is running, provide a list of all known features so that all their respective /// primitives may be documented. /// @@ -687,6 +823,7 @@ pub fn all_rust_features() -> impl Iterator<Item = (&'static str, StabilityUncom .chain(LOONGARCH_FEATURES) .chain(IBMZ_FEATURES) .chain(SPARC_FEATURES) + .chain(M68K_FEATURES) .cloned() .map(|(f, s, _)| (f, s)) } @@ -734,6 +871,7 @@ impl Target { "loongarch64" => LOONGARCH_FEATURES, "s390x" => IBMZ_FEATURES, "sparc" | "sparc64" => SPARC_FEATURES, + "m68k" => M68K_FEATURES, _ => &[], } } @@ -751,7 +889,7 @@ impl Target { "sparc" | "sparc64" => SPARC_FEATURES_FOR_CORRECT_VECTOR_ABI, "hexagon" => HEXAGON_FEATURES_FOR_CORRECT_VECTOR_ABI, "mips" | "mips32r6" | "mips64" | "mips64r6" => MIPS_FEATURES_FOR_CORRECT_VECTOR_ABI, - "bpf" => &[], // no vector ABI + "bpf" | "m68k" => &[], // no vector ABI "csky" => CSKY_FEATURES_FOR_CORRECT_VECTOR_ABI, // FIXME: for some tier3 targets, we are overly cautious and always give warnings // when passing args in vector registers. |