Do not compute the shallow hash twice.

Author: cjgillot

compiler/rustc_ast_lowering/src/lib.rs

@@ -659,25 +659,28 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         let bodies = SortedMap::from_presorted_elements(bodies);
 
         // Don't hash unless necessary, because it's expensive.
-        let (opt_hash_including_bodies, attrs_hash) = if self.tcx.needs_crate_hash() {
+        let (opt_hash_without_bodies, opt_bodies_hash, attrs_hash) = if self.tcx.needs_crate_hash()
+        {
             self.tcx.with_stable_hashing_context(|mut hcx| {
                 let mut stable_hasher = StableHasher::new();
-                hcx.with_hir_bodies(node.def_id(), &bodies, |hcx| {
-                    node.hash_stable(hcx, &mut stable_hasher)
-                });
+                hcx.without_hir_bodies(|hcx| node.hash_stable(hcx, &mut stable_hasher));
                 let h1 = stable_hasher.finish();
 
                 let mut stable_hasher = StableHasher::new();
-                attrs.hash_stable(&mut hcx, &mut stable_hasher);
+                hcx.without_hir_bodies(|hcx| bodies.hash_stable(hcx, &mut stable_hasher));
                 let h2 = stable_hasher.finish();
 
-                (Some(h1), Some(h2))
+                let mut stable_hasher = StableHasher::new();
+                attrs.hash_stable(&mut hcx, &mut stable_hasher);
+                let h3 = stable_hasher.finish();
+
+                (Some(h1), Some(h2), Some(h3))
             })
         } else {
-            (None, None)
+            (None, None, None)
         };
         let (nodes, parenting) = index::index_hir(self.tcx, node, &bodies);
-        let nodes = hir::OwnerNodes { opt_hash_including_bodies, nodes, bodies };
+        let nodes = hir::OwnerNodes { opt_hash_without_bodies, opt_bodies_hash, nodes, bodies };
         let attrs = hir::AttributeMap { map: attrs, opt_hash: attrs_hash };
 
         self.arena.alloc(hir::OwnerInfo { nodes, parenting, attrs, trait_map })

compiler/rustc_hir/src/hir.rs

@@ -830,7 +830,11 @@ impl<'tcx> AttributeMap<'tcx> {
 pub struct OwnerNodes<'tcx> {
     /// Pre-computed hash of the full HIR. Used in the crate hash. Only present
     /// when incr. comp. is enabled.
-    pub opt_hash_including_bodies: Option<Fingerprint>,
+    pub opt_bodies_hash: Option<Fingerprint>,
+    /// Perform a shallow hash instead using the deep hash saved in `OwnerNodes`. This lets us
+    /// differentiate queries that depend on the full HIR tree from those that only depend on
+    /// the item signature.
+    pub opt_hash_without_bodies: Option<Fingerprint>,
     /// Full HIR for the current owner.
     // The zeroth node's parent should never be accessed: the owner's parent is computed by the
     // hir_owner_parent query. It is set to `ItemLocalId::INVALID` to force an ICE if accidentally
@@ -867,7 +871,8 @@ impl fmt::Debug for OwnerNodes<'_> {
                     .collect::<Vec<_>>(),
             )
             .field("bodies", &self.bodies)
-            .field("opt_hash_including_bodies", &self.opt_hash_including_bodies)
+            .field("opt_hash_without_bodies", &self.opt_hash_without_bodies)
+            .field("opt_bodies_hash", &self.opt_bodies_hash)
             .finish()
     }
 }

compiler/rustc_hir/src/stable_hash_impls.rs

@@ -100,8 +100,9 @@ impl<'tcx, HirCtx: crate::HashStableContext> HashStable<HirCtx> for OwnerNodes<'
         // `local_id_to_def_id` is also ignored because is dependent on the body, then just hashing
         // the body satisfies the condition of two nodes being different have different
         // `hash_stable` results.
-        let OwnerNodes { opt_hash_including_bodies, nodes: _, bodies: _ } = *self;
-        opt_hash_including_bodies.unwrap().hash_stable(hcx, hasher);
+        let OwnerNodes { opt_hash_without_bodies, opt_bodies_hash, nodes: _, bodies: _ } = *self;
+        opt_hash_without_bodies.unwrap().hash_stable(hcx, hasher);
+        opt_bodies_hash.unwrap().hash_stable(hcx, hasher);
     }
 }
 

compiler/rustc_middle/src/hir/mod.rs

@@ -8,6 +8,7 @@ pub mod place;
 
 use crate::query::Providers;
 use crate::ty::{EarlyBinder, ImplSubject, TyCtxt};
+use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_data_structures::sync::{try_par_for_each_in, DynSend, DynSync};
 use rustc_hir::def::DefKind;
@@ -24,15 +25,13 @@ use rustc_span::{ErrorGuaranteed, ExpnId, DUMMY_SP};
 #[derive(Copy, Clone, Debug)]
 pub struct Owner<'tcx> {
     node: OwnerNode<'tcx>,
+    opt_hash_without_bodies: Option<Fingerprint>,
 }
 
 impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for Owner<'tcx> {
     #[inline]
     fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
-        // Perform a shallow hash instead using the deep hash saved in `OwnerNodes`. This lets us
-        // differentiate queries that depend on the full HIR tree from those that only depend on
-        // the item signature.
-        hcx.without_hir_bodies(|hcx| self.node.hash_stable(hcx, hasher));
+        self.opt_hash_without_bodies.hash_stable(hcx, hasher)
     }
 }
 
@@ -152,7 +151,7 @@ pub fn provide(providers: &mut Providers) {
     providers.hir_owner = |tcx, id| {
         let owner = tcx.hir_crate(()).owners.get(id.def_id)?.as_owner()?;
         let node = owner.node();
-        Some(Owner { node })
+        Some(Owner { node, opt_hash_without_bodies: owner.nodes.opt_hash_without_bodies })
     };
     providers.opt_local_def_id_to_hir_id = |tcx, id| {
         let owner = tcx.hir_crate(()).owners[id].map(|_| ());

compiler/rustc_mir_transform/src/coverage/mod.rs

@@ -13,6 +13,7 @@ use self::spans::{BcbMapping, BcbMappingKind, CoverageSpans};
 
 use crate::MirPass;
 
+use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_middle::hir;
 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use rustc_middle::mir::coverage::*;
@@ -419,12 +420,9 @@ fn get_body_span<'tcx>(
 }
 
 fn hash_mir_source<'tcx>(tcx: TyCtxt<'tcx>, hir_body: &'tcx rustc_hir::Body<'tcx>) -> u64 {
-    // FIXME(cjgillot) Stop hashing HIR manually here.
     let owner = hir_body.id().hir_id.owner;
-    tcx.hir_owner_nodes(owner)
-        .unwrap()
-        .opt_hash_including_bodies
-        .unwrap()
+    let owner = tcx.hir_owner_nodes(owner).unwrap();
+    Fingerprint::combine(owner.opt_hash_without_bodies.unwrap(), owner.opt_bodies_hash.unwrap())
         .to_smaller_hash()
         .as_u64()
 }

compiler/rustc_query_system/src/ich/hcx.rs

@@ -1,10 +1,8 @@
 use crate::ich;
 
 use rustc_ast as ast;
-use rustc_data_structures::sorted_map::SortedMap;
 use rustc_data_structures::stable_hasher::{HashStable, HashingControls, StableHasher};
 use rustc_data_structures::sync::Lrc;
-use rustc_hir as hir;
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_hir::definitions::DefPathHash;
 use rustc_session::cstore::Untracked;
@@ -23,7 +21,7 @@ pub struct StableHashingContext<'a> {
     // The value of `-Z incremental-ignore-spans`.
     // This field should only be used by `unstable_opts_incremental_ignore_span`
     incremental_ignore_spans: bool,
-    pub(super) body_resolver: BodyResolver<'a>,
+    pub(super) body_resolver: BodyResolver,
     // Very often, we are hashing something that does not need the
     // `CachingSourceMapView`, so we initialize it lazily.
     raw_source_map: &'a SourceMap,
@@ -35,13 +33,9 @@ pub struct StableHashingContext<'a> {
 /// We could also just store a plain reference to the `hir::Crate` but we want
 /// to avoid that the crate is used to get untracked access to all of the HIR.
 #[derive(Clone, Copy)]
-pub(super) enum BodyResolver<'tcx> {
+pub(super) enum BodyResolver {
     Forbidden,
     Ignore,
-    Traverse {
-        owner: hir::OwnerId,
-        bodies: &'tcx SortedMap<hir::ItemLocalId, &'tcx hir::Body<'tcx>>,
-    },
 }
 
 impl<'a> StableHashingContext<'a> {
@@ -64,19 +58,6 @@ impl<'a> StableHashingContext<'a> {
         f(&mut StableHashingContext { body_resolver: BodyResolver::Ignore, ..self.clone() });
     }
 
-    #[inline]
-    pub fn with_hir_bodies(
-        &mut self,
-        owner: hir::OwnerId,
-        bodies: &SortedMap<hir::ItemLocalId, &hir::Body<'_>>,
-        f: impl FnOnce(&mut StableHashingContext<'_>),
-    ) {
-        f(&mut StableHashingContext {
-            body_resolver: BodyResolver::Traverse { owner, bodies },
-            ..self.clone()
-        });
-    }
-
     #[inline]
     pub fn while_hashing_spans<F: FnOnce(&mut Self)>(&mut self, hash_spans: bool, f: F) {
         let prev_hash_spans = self.hashing_controls.hash_spans;

compiler/rustc_query_system/src/ich/impls_hir.rs

@@ -8,15 +8,11 @@ use rustc_hir as hir;
 
 impl<'ctx> rustc_hir::HashStableContext for StableHashingContext<'ctx> {
     #[inline]
-    fn hash_body_id(&mut self, id: hir::BodyId, hasher: &mut StableHasher) {
+    fn hash_body_id(&mut self, hir::BodyId { hir_id }: hir::BodyId, hasher: &mut StableHasher) {
         let hcx = self;
         match hcx.body_resolver {
             BodyResolver::Forbidden => panic!("Hashing HIR bodies is forbidden."),
-            BodyResolver::Ignore => {}
-            BodyResolver::Traverse { owner, bodies } => {
-                assert_eq!(id.hir_id.owner, owner);
-                bodies[&id.hir_id.local_id].hash_stable(hcx, hasher);
-            }
+            BodyResolver::Ignore => hir_id.hash_stable(hcx, hasher),
         }
     }
 }