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Rollup merge of rust-lang#93147 - nnethercote:interner-cleanups, r=lcnr
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Interner cleanups

Improve some code that I have found confusing.

r? `@lcnr`
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@matthiaskrgr
matthiaskrgr authored Jan 22, 2022
2 parents 514723f + d46ed5d commit 3fa1e2a
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Showing 2 changed files with 69 additions and 44 deletions.
96 changes: 52 additions & 44 deletions compiler/rustc_middle/src/ty/context.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -113,6 +113,12 @@ pub struct CtxtInterners<'tcx> {
bound_variable_kinds: InternedSet<'tcx, List<ty::BoundVariableKind>>,
layout: InternedSet<'tcx, Layout>,
adt_def: InternedSet<'tcx, AdtDef>,

/// `#[stable]` and `#[unstable]` attributes
stability: InternedSet<'tcx, attr::Stability>,

/// `#[rustc_const_stable]` and `#[rustc_const_unstable]` attributes
const_stability: InternedSet<'tcx, attr::ConstStability>,
}

impl<'tcx> CtxtInterners<'tcx> {
Expand All @@ -134,6 +140,8 @@ impl<'tcx> CtxtInterners<'tcx> {
bound_variable_kinds: Default::default(),
layout: Default::default(),
adt_def: Default::default(),
stability: Default::default(),
const_stability: Default::default(),
}
}

Expand Down Expand Up @@ -1035,12 +1043,6 @@ pub struct GlobalCtxt<'tcx> {
/// Data layout specification for the current target.
pub data_layout: TargetDataLayout,

/// `#[stable]` and `#[unstable]` attributes
stability_interner: ShardedHashMap<&'tcx attr::Stability, ()>,

/// `#[rustc_const_stable]` and `#[rustc_const_unstable]` attributes
const_stability_interner: ShardedHashMap<&'tcx attr::ConstStability, ()>,

/// Stores memory for globals (statics/consts).
pub(crate) alloc_map: Lock<interpret::AllocMap<'tcx>>,

Expand Down Expand Up @@ -1092,16 +1094,6 @@ impl<'tcx> TyCtxt<'tcx> {
self.create_memory_alloc(alloc)
}

// FIXME(eddyb) move to `direct_interners!`.
pub fn intern_stability(self, stab: attr::Stability) -> &'tcx attr::Stability {
self.stability_interner.intern(stab, |stab| self.arena.alloc(stab))
}

// FIXME(eddyb) move to `direct_interners!`.
pub fn intern_const_stability(self, stab: attr::ConstStability) -> &'tcx attr::ConstStability {
self.const_stability_interner.intern(stab, |stab| self.arena.alloc(stab))
}

/// Returns a range of the start/end indices specified with the
/// `rustc_layout_scalar_valid_range` attribute.
// FIXME(eddyb) this is an awkward spot for this method, maybe move it?
Expand Down Expand Up @@ -1185,8 +1177,6 @@ impl<'tcx> TyCtxt<'tcx> {
evaluation_cache: Default::default(),
crate_name: Symbol::intern(crate_name),
data_layout,
stability_interner: Default::default(),
const_stability_interner: Default::default(),
alloc_map: Lock::new(interpret::AllocMap::new()),
output_filenames: Arc::new(output_filenames),
}
Expand Down Expand Up @@ -1952,11 +1942,11 @@ impl<'tcx> TyCtxt<'tcx> {

writeln!(fmt, "InternalSubsts interner: #{}", self.0.interners.substs.len())?;
writeln!(fmt, "Region interner: #{}", self.0.interners.region.len())?;
writeln!(fmt, "Stability interner: #{}", self.0.stability_interner.len())?;
writeln!(fmt, "Stability interner: #{}", self.0.interners.stability.len())?;
writeln!(
fmt,
"Const Stability interner: #{}",
self.0.const_stability_interner.len()
self.0.interners.const_stability.len()
)?;
writeln!(
fmt,
Expand All @@ -1973,24 +1963,37 @@ impl<'tcx> TyCtxt<'tcx> {
}
}

/// An entry in an interner.
// This type holds a `T` in the interner. The `T` is stored in the arena and
// this type just holds a pointer to it, but it still effectively owns it. It
// impls `Borrow` so that it can be looked up using the original
// (non-arena-memory-owning) types.
struct Interned<'tcx, T: ?Sized>(&'tcx T);

impl<'tcx, T: 'tcx + ?Sized> Clone for Interned<'tcx, T> {
fn clone(&self) -> Self {
Interned(self.0)
}
}

impl<'tcx, T: 'tcx + ?Sized> Copy for Interned<'tcx, T> {}

impl<'tcx, T: 'tcx + ?Sized> IntoPointer for Interned<'tcx, T> {
fn into_pointer(&self) -> *const () {
self.0 as *const _ as *const ()
}
}
// N.B., an `Interned<Ty>` compares and hashes as a `TyKind`.

#[allow(rustc::usage_of_ty_tykind)]
impl<'tcx> Borrow<TyKind<'tcx>> for Interned<'tcx, TyS<'tcx>> {
fn borrow<'a>(&'a self) -> &'a TyKind<'tcx> {
&self.0.kind()
}
}

impl<'tcx> PartialEq for Interned<'tcx, TyS<'tcx>> {
fn eq(&self, other: &Interned<'tcx, TyS<'tcx>>) -> bool {
// The `Borrow` trait requires that `x.borrow() == y.borrow()` equals
// `x == y`.
self.0.kind() == other.0.kind()
}
}
Expand All @@ -1999,19 +2002,21 @@ impl<'tcx> Eq for Interned<'tcx, TyS<'tcx>> {}

impl<'tcx> Hash for Interned<'tcx, TyS<'tcx>> {
fn hash<H: Hasher>(&self, s: &mut H) {
// The `Borrow` trait requires that `x.borrow().hash(s) == x.hash(s)`.
self.0.kind().hash(s)
}
}

#[allow(rustc::usage_of_ty_tykind)]
impl<'tcx> Borrow<TyKind<'tcx>> for Interned<'tcx, TyS<'tcx>> {
fn borrow<'a>(&'a self) -> &'a TyKind<'tcx> {
&self.0.kind()
impl<'tcx> Borrow<Binder<'tcx, PredicateKind<'tcx>>> for Interned<'tcx, PredicateInner<'tcx>> {
fn borrow<'a>(&'a self) -> &'a Binder<'tcx, PredicateKind<'tcx>> {
&self.0.kind
}
}
// N.B., an `Interned<PredicateInner>` compares and hashes as a `PredicateKind`.

impl<'tcx> PartialEq for Interned<'tcx, PredicateInner<'tcx>> {
fn eq(&self, other: &Interned<'tcx, PredicateInner<'tcx>>) -> bool {
// The `Borrow` trait requires that `x.borrow() == y.borrow()` equals
// `x == y`.
self.0.kind == other.0.kind
}
}
Expand All @@ -2020,19 +2025,21 @@ impl<'tcx> Eq for Interned<'tcx, PredicateInner<'tcx>> {}

impl<'tcx> Hash for Interned<'tcx, PredicateInner<'tcx>> {
fn hash<H: Hasher>(&self, s: &mut H) {
// The `Borrow` trait requires that `x.borrow().hash(s) == x.hash(s)`.
self.0.kind.hash(s)
}
}

impl<'tcx> Borrow<Binder<'tcx, PredicateKind<'tcx>>> for Interned<'tcx, PredicateInner<'tcx>> {
fn borrow<'a>(&'a self) -> &'a Binder<'tcx, PredicateKind<'tcx>> {
&self.0.kind
impl<'tcx, T> Borrow<[T]> for Interned<'tcx, List<T>> {
fn borrow<'a>(&'a self) -> &'a [T] {
&self.0[..]
}
}

// N.B., an `Interned<List<T>>` compares and hashes as its elements.
impl<'tcx, T: PartialEq> PartialEq for Interned<'tcx, List<T>> {
fn eq(&self, other: &Interned<'tcx, List<T>>) -> bool {
// The `Borrow` trait requires that `x.borrow() == y.borrow()` equals
// `x == y`.
self.0[..] == other.0[..]
}
}
Expand All @@ -2041,20 +2048,23 @@ impl<'tcx, T: Eq> Eq for Interned<'tcx, List<T>> {}

impl<'tcx, T: Hash> Hash for Interned<'tcx, List<T>> {
fn hash<H: Hasher>(&self, s: &mut H) {
// The `Borrow` trait requires that `x.borrow().hash(s) == x.hash(s)`.
self.0[..].hash(s)
}
}

impl<'tcx, T> Borrow<[T]> for Interned<'tcx, List<T>> {
fn borrow<'a>(&'a self) -> &'a [T] {
&self.0[..]
}
}

macro_rules! direct_interners {
($($name:ident: $method:ident($ty:ty),)+) => {
$(impl<'tcx> PartialEq for Interned<'tcx, $ty> {
$(impl<'tcx> Borrow<$ty> for Interned<'tcx, $ty> {
fn borrow<'a>(&'a self) -> &'a $ty {
&self.0
}
}

impl<'tcx> PartialEq for Interned<'tcx, $ty> {
fn eq(&self, other: &Self) -> bool {
// The `Borrow` trait requires that `x.borrow() == y.borrow()`
// equals `x == y`.
self.0 == other.0
}
}
Expand All @@ -2063,16 +2073,12 @@ macro_rules! direct_interners {

impl<'tcx> Hash for Interned<'tcx, $ty> {
fn hash<H: Hasher>(&self, s: &mut H) {
// The `Borrow` trait requires that `x.borrow().hash(s) ==
// x.hash(s)`.
self.0.hash(s)
}
}

impl<'tcx> Borrow<$ty> for Interned<'tcx, $ty> {
fn borrow<'a>(&'a self) -> &'a $ty {
&self.0
}
}

impl<'tcx> TyCtxt<'tcx> {
pub fn $method(self, v: $ty) -> &'tcx $ty {
self.interners.$name.intern(v, |v| {
Expand All @@ -2089,6 +2095,8 @@ direct_interners! {
const_allocation: intern_const_alloc(Allocation),
layout: intern_layout(Layout),
adt_def: intern_adt_def(AdtDef),
stability: intern_stability(attr::Stability),
const_stability: intern_const_stability(attr::ConstStability),
}

macro_rules! slice_interners {
Expand Down
17 changes: 17 additions & 0 deletions compiler/rustc_middle/src/ty/mod.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -376,15 +376,28 @@ pub struct CReaderCacheKey {
pub pos: usize,
}

/// Represents a type.
///
/// IMPORTANT: Every `TyS` is *required* to have unique contents. The type's
/// correctness relies on this, *but it does not enforce it*. Therefore, any
/// code that creates a `TyS` must ensure uniqueness itself. In practice this
/// is achieved by interning.
#[allow(rustc::usage_of_ty_tykind)]
pub struct TyS<'tcx> {
/// This field shouldn't be used directly and may be removed in the future.
/// Use `TyS::kind()` instead.
kind: TyKind<'tcx>,

/// This field provides fast access to information that is also contained
/// in `kind`.
///
/// This field shouldn't be used directly and may be removed in the future.
/// Use `TyS::flags()` instead.
flags: TypeFlags,

/// This field provides fast access to information that is also contained
/// in `kind`.
///
/// This is a kind of confusing thing: it stores the smallest
/// binder such that
///
Expand Down Expand Up @@ -436,13 +449,17 @@ impl<'tcx> PartialOrd for TyS<'tcx> {
impl<'tcx> PartialEq for TyS<'tcx> {
#[inline]
fn eq(&self, other: &TyS<'tcx>) -> bool {
// Pointer equality implies equality (due to the unique contents
// assumption).
ptr::eq(self, other)
}
}
impl<'tcx> Eq for TyS<'tcx> {}

impl<'tcx> Hash for TyS<'tcx> {
fn hash<H: Hasher>(&self, s: &mut H) {
// Pointer hashing is sufficient (due to the unique contents
// assumption).
(self as *const TyS<'_>).hash(s)
}
}
Expand Down

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