Also cache the stable hash of interned Predicates

compiler/rustc_middle/src/arena.rs

@@ -89,7 +89,7 @@ macro_rules! arena_types {
 
             // Interned types
             [] tys: rustc_data_structures::intern::WithStableHash<rustc_middle::ty::TyS<'tcx>>,
-            [] predicates: rustc_middle::ty::PredicateS<'tcx>,
+            [] predicates: rustc_data_structures::intern::WithStableHash<rustc_middle::ty::PredicateS<'tcx>>,
             [] consts: rustc_middle::ty::ConstS<'tcx>,
 
             // Note that this deliberately duplicates items in the `rustc_hir::arena`,

compiler/rustc_middle/src/ty/context.rs

@@ -141,7 +141,7 @@ pub struct CtxtInterners<'tcx> {
     canonical_var_infos: InternedSet<'tcx, List<CanonicalVarInfo<'tcx>>>,
     region: InternedSet<'tcx, RegionKind<'tcx>>,
     poly_existential_predicates: InternedSet<'tcx, List<PolyExistentialPredicate<'tcx>>>,
-    predicate: InternedSet<'tcx, PredicateS<'tcx>>,
+    predicate: InternedSet<'tcx, WithStableHash<PredicateS<'tcx>>>,
     predicates: InternedSet<'tcx, List<Predicate<'tcx>>>,
     projs: InternedSet<'tcx, List<ProjectionKind>>,
     place_elems: InternedSet<'tcx, List<PlaceElem<'tcx>>>,
@@ -188,20 +188,8 @@ impl<'tcx> CtxtInterners<'tcx> {
             self.type_
                 .intern(kind, |kind| {
                     let flags = super::flags::FlagComputation::for_kind(&kind);
-
-                    // It's impossible to hash inference variables (and will ICE), so we don't need to try to cache them.
-                    // Without incremental, we rarely stable-hash types, so let's not do it proactively.
-                    let stable_hash = if flags.flags.intersects(TypeFlags::NEEDS_INFER)
-                        || sess.opts.incremental.is_none()
-                    {
-                        Fingerprint::ZERO
-                    } else {
-                        let mut hasher = StableHasher::new();
-                        let mut hcx =
-                            StableHashingContext::new(sess, definitions, cstore, source_span);
-                        kind.hash_stable(&mut hcx, &mut hasher);
-                        hasher.finish()
-                    };
+                    let stable_hash =
+                        self.stable_hash(&flags, sess, definitions, cstore, source_span, &kind);
 
                     let ty_struct = TyS {
                         kind,
@@ -217,20 +205,54 @@ impl<'tcx> CtxtInterners<'tcx> {
         ))
     }
 
+    fn stable_hash<'a, T: HashStable<StableHashingContext<'a>>>(
+        &self,
+        flags: &ty::flags::FlagComputation,
+        sess: &'a Session,
+        definitions: &'a rustc_hir::definitions::Definitions,
+        cstore: &'a CrateStoreDyn,
+        source_span: &'a IndexVec<LocalDefId, Span>,
+        val: &T,
+    ) -> Fingerprint {
+        // It's impossible to hash inference variables (and will ICE), so we don't need to try to cache them.
+        // Without incremental, we rarely stable-hash types, so let's not do it proactively.
+        if flags.flags.intersects(TypeFlags::NEEDS_INFER) || sess.opts.incremental.is_none() {
+            Fingerprint::ZERO
+        } else {
+            let mut hasher = StableHasher::new();
+            let mut hcx = StableHashingContext::new(sess, definitions, cstore, source_span);
+            val.hash_stable(&mut hcx, &mut hasher);
+            hasher.finish()
+        }
+    }
+
     #[inline(never)]
-    fn intern_predicate(&self, kind: Binder<'tcx, PredicateKind<'tcx>>) -> Predicate<'tcx> {
+    fn intern_predicate(
+        &self,
+        kind: Binder<'tcx, PredicateKind<'tcx>>,
+        sess: &Session,
+        definitions: &rustc_hir::definitions::Definitions,
+        cstore: &CrateStoreDyn,
+        source_span: &IndexVec<LocalDefId, Span>,
+    ) -> Predicate<'tcx> {
         Predicate(Interned::new_unchecked(
             self.predicate
                 .intern(kind, |kind| {
                     let flags = super::flags::FlagComputation::for_predicate(kind);
 
+                    let stable_hash =
+                        self.stable_hash(&flags, sess, definitions, cstore, source_span, &kind);
+
                     let predicate_struct = PredicateS {
                         kind,
                         flags: flags.flags,
                         outer_exclusive_binder: flags.outer_exclusive_binder,
                     };
 
-                    InternedInSet(self.arena.alloc(predicate_struct))
+                    InternedInSet(
+                        self.arena
+                            .alloc(WithStableHash { internee: predicate_struct, stable_hash }),
+                    )
                 })
                 .0,
         ))
@@ -2158,23 +2180,25 @@ impl<'tcx> Hash for InternedInSet<'tcx, WithStableHash<TyS<'tcx>>> {
     }
 }
 
-impl<'tcx> Borrow<Binder<'tcx, PredicateKind<'tcx>>> for InternedInSet<'tcx, PredicateS<'tcx>> {
+impl<'tcx> Borrow<Binder<'tcx, PredicateKind<'tcx>>>
+    for InternedInSet<'tcx, WithStableHash<PredicateS<'tcx>>>
+{
     fn borrow<'a>(&'a self) -> &'a Binder<'tcx, PredicateKind<'tcx>> {
         &self.0.kind
     }
 }
 
-impl<'tcx> PartialEq for InternedInSet<'tcx, PredicateS<'tcx>> {
-    fn eq(&self, other: &InternedInSet<'tcx, PredicateS<'tcx>>) -> bool {
+impl<'tcx> PartialEq for InternedInSet<'tcx, WithStableHash<PredicateS<'tcx>>> {
+    fn eq(&self, other: &InternedInSet<'tcx, WithStableHash<PredicateS<'tcx>>>) -> bool {
         // The `Borrow` trait requires that `x.borrow() == y.borrow()` equals
         // `x == y`.
         self.0.kind == other.0.kind
     }
 }
 
-impl<'tcx> Eq for InternedInSet<'tcx, PredicateS<'tcx>> {}
+impl<'tcx> Eq for InternedInSet<'tcx, WithStableHash<PredicateS<'tcx>>> {}
 
-impl<'tcx> Hash for InternedInSet<'tcx, PredicateS<'tcx>> {
+impl<'tcx> Hash for InternedInSet<'tcx, WithStableHash<PredicateS<'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)
@@ -2373,7 +2397,14 @@ impl<'tcx> TyCtxt<'tcx> {
 
     #[inline]
     pub fn mk_predicate(self, binder: Binder<'tcx, PredicateKind<'tcx>>) -> Predicate<'tcx> {
-        self.interners.intern_predicate(binder)
+        self.interners.intern_predicate(
+            binder,
+            self.sess,
+            &self.definitions.read(),
+            &*self.untracked_resolutions.cstore,
+            // This is only used to create a stable hashing context.
+            &self.untracked_resolutions.source_span,
+        )
     }
 
     #[inline]

compiler/rustc_middle/src/ty/mod.rs

@@ -546,9 +546,9 @@ pub(crate) struct PredicateS<'tcx> {
 }
 
 /// Use this rather than `PredicateS`, whenever possible.
-#[derive(Clone, Copy, PartialEq, Eq, Hash)]
+#[derive(Clone, Copy, PartialEq, Eq, Hash, HashStable)]
 #[rustc_pass_by_value]
-pub struct Predicate<'tcx>(Interned<'tcx, PredicateS<'tcx>>);
+pub struct Predicate<'tcx>(Interned<'tcx, WithStableHash<PredicateS<'tcx>>>);
 
 impl<'tcx> Predicate<'tcx> {
     /// Gets the inner `Binder<'tcx, PredicateKind<'tcx>>`.
@@ -627,7 +627,7 @@ impl<'tcx> Predicate<'tcx> {
     }
 }
 
-impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for Predicate<'tcx> {
+impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for PredicateS<'tcx> {
     fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
         let PredicateS {
             ref kind,
@@ -636,7 +636,7 @@ impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for Predicate<'tcx> {
             // also contained in `kind`, so no need to hash them.
             flags: _,
             outer_exclusive_binder: _,
-        } = self.0.0;
+        } = self;
 
         kind.hash_stable(hcx, hasher);
     }