Pre-hash visibilities in resolver.

Author: cjgillot

compiler/rustc_middle/src/hir/map.rs

@@ -1177,11 +1177,7 @@ pub(super) fn crate_hash(tcx: TyCtxt<'_>, _: LocalCrate) -> Svh {
         }
         tcx.sess.opts.dep_tracking_hash(true).hash_stable(&mut hcx, &mut stable_hasher);
         tcx.stable_crate_id(LOCAL_CRATE).hash_stable(&mut hcx, &mut stable_hasher);
-        // Hash visibility information since it does not appear in HIR.
-        // FIXME: Figure out how to remove `visibilities_for_hashing` by hashing visibilities on
-        // the fly in the resolver, storing only their accumulated hash in `ResolverGlobalCtxt`,
-        // and combining it with other hashes here.
-        resolutions.visibilities_for_hashing.hash_stable(&mut hcx, &mut stable_hasher);
+        resolutions.visibilities_hash.hash_stable(&mut hcx, &mut stable_hasher);
         with_metavar_spans(|mspans| {
             mspans.freeze_and_get_read_spans().hash_stable(&mut hcx, &mut stable_hasher);
         });

compiler/rustc_middle/src/ty/mod.rs

@@ -29,6 +29,7 @@ use rustc_ast::expand::StrippedCfgItem;
 use rustc_ast::node_id::NodeMap;
 pub use rustc_ast_ir::{Movability, Mutability, try_visit};
 use rustc_attr_data_structures::AttributeKind;
+use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap, FxIndexSet};
 use rustc_data_structures::intern::Interned;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
@@ -178,7 +179,7 @@ pub struct ResolverOutputs {
 
 #[derive(Debug, HashStable)]
 pub struct ResolverGlobalCtxt {
-    pub visibilities_for_hashing: Vec<(LocalDefId, Visibility)>,
+    pub visibilities_hash: Fingerprint,
     /// Item with a given `LocalDefId` was defined during macro expansion with ID `ExpnId`.
     pub expn_that_defined: UnordMap<LocalDefId, ExpnId>,
     pub effective_visibilities: EffectiveVisibilities,

compiler/rustc_resolve/src/lib.rs

@@ -1663,9 +1663,16 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             })
             .collect();
 
+        let visibilities_hash = {
+            let mut hasher = StableHasher::new();
+            let mut hcx = self.create_stable_hashing_context();
+            self.visibilities_for_hashing.hash_stable(&mut hcx, &mut hasher);
+            hasher.finish()
+        };
+
         let global_ctxt = ResolverGlobalCtxt {
             expn_that_defined,
-            visibilities_for_hashing: self.visibilities_for_hashing,
+            visibilities_hash,
             effective_visibilities,
             extern_crate_map,
             module_children: self.module_children,