Do not require the DefPathTable to construct the on-disk cache.

compiler/rustc_hir/src/definitions.rs

@@ -94,15 +94,6 @@ impl DefPathTable {
             .iter_enumerated()
             .map(move |(index, key)| (index, key, &self.def_path_hashes[index]))
     }
-
-    pub fn all_def_path_hashes_and_def_ids(
-        &self,
-        krate: CrateNum,
-    ) -> impl Iterator<Item = (DefPathHash, DefId)> + '_ {
-        self.def_path_hashes
-            .iter_enumerated()
-            .map(move |(index, hash)| (*hash, DefId { krate, index }))
-    }
 }
 
 /// The definition table containing node definitions.
@@ -440,6 +431,14 @@ impl Definitions {
     pub fn iter_local_def_id(&self) -> impl Iterator<Item = LocalDefId> + '_ {
         self.def_id_to_hir_id.iter_enumerated().map(|(k, _)| k)
     }
+
+    #[inline(always)]
+    pub fn local_def_path_hash_to_def_id(&self, hash: DefPathHash) -> Option<LocalDefId> {
+        self.table
+            .def_path_hash_to_index
+            .get(&hash)
+            .map(|&local_def_index| LocalDefId { local_def_index })
+    }
 }
 
 #[derive(Copy, Clone, PartialEq, Debug)]

compiler/rustc_incremental/src/persist/load.rs

@@ -1,7 +1,6 @@
 //! Code to save/load the dep-graph from files.
 
 use rustc_data_structures::fx::FxHashMap;
-use rustc_hir::definitions::DefPathTable;
 use rustc_middle::dep_graph::{SerializedDepGraph, WorkProduct, WorkProductId};
 use rustc_middle::ty::query::OnDiskCache;
 use rustc_serialize::opaque::Decoder;
@@ -196,10 +195,7 @@ pub fn load_dep_graph(sess: &Session) -> DepGraphFuture {
 /// If we are not in incremental compilation mode, returns `None`.
 /// Otherwise, tries to load the query result cache from disk,
 /// creating an empty cache if it could not be loaded.
-pub fn load_query_result_cache<'a>(
-    sess: &'a Session,
-    def_path_table: &DefPathTable,
-) -> Option<OnDiskCache<'a>> {
+pub fn load_query_result_cache<'a>(sess: &'a Session) -> Option<OnDiskCache<'a>> {
     if sess.opts.incremental.is_none() {
         return None;
     }
@@ -212,7 +208,7 @@ pub fn load_query_result_cache<'a>(
         sess.is_nightly_build(),
     ) {
         LoadResult::Ok { data: (bytes, start_pos) } => {
-            Some(OnDiskCache::new(sess, bytes, start_pos, def_path_table))
+            Some(OnDiskCache::new(sess, bytes, start_pos))
         }
         _ => Some(OnDiskCache::new_empty(sess.source_map())),
     }

compiler/rustc_interface/src/passes.rs

@@ -765,9 +765,7 @@ pub fn create_global_ctxt<'tcx>(
 ) -> QueryContext<'tcx> {
     let sess = &compiler.session();
 
-    let def_path_table = resolver_outputs.definitions.def_path_table();
-    let query_result_on_disk_cache =
-        rustc_incremental::load_query_result_cache(sess, def_path_table);
+    let query_result_on_disk_cache = rustc_incremental::load_query_result_cache(sess);
 
     let codegen_backend = compiler.codegen_backend();
     let mut local_providers = *DEFAULT_QUERY_PROVIDERS;

compiler/rustc_middle/src/ty/query/on_disk_cache.rs

@@ -10,7 +10,7 @@ use rustc_data_structures::thin_vec::ThinVec;
 use rustc_data_structures::unhash::UnhashMap;
 use rustc_errors::Diagnostic;
 use rustc_hir::def_id::{CrateNum, DefId, DefIndex, LocalDefId, LOCAL_CRATE};
-use rustc_hir::definitions::{DefPathHash, DefPathTable};
+use rustc_hir::definitions::DefPathHash;
 use rustc_index::vec::{Idx, IndexVec};
 use rustc_query_system::dep_graph::DepContext;
 use rustc_query_system::query::QueryContext;
@@ -27,7 +27,6 @@ use rustc_span::source_map::{SourceMap, StableSourceFileId};
 use rustc_span::CachingSourceMapView;
 use rustc_span::{BytePos, ExpnData, SourceFile, Span, DUMMY_SP};
 use std::collections::hash_map::Entry;
-use std::iter::FromIterator;
 use std::mem;
 
 const TAG_FILE_FOOTER: u128 = 0xC0FFEE_C0FFEE_C0FFEE_C0FFEE_C0FFEE;
@@ -103,12 +102,6 @@ pub struct OnDiskCache<'sess> {
     // during the next compilation session.
     latest_foreign_def_path_hashes: Lock<UnhashMap<DefPathHash, RawDefId>>,
 
-    // Maps `DefPathHashes` to their corresponding `LocalDefId`s for all
-    // local items in the current compilation session. This is only populated
-    // when we are in incremental mode and have loaded a pre-existing cache
-    // from disk, since this map is only used when deserializing a `DefPathHash`
-    // from the incremental cache.
-    local_def_path_hash_to_def_id: UnhashMap<DefPathHash, LocalDefId>,
     // Caches all lookups of `DefPathHashes`, both for local and foreign
     // definitions. A definition from the previous compilation session
     // may no longer exist in the current compilation session, so
@@ -168,12 +161,7 @@ crate struct RawDefId {
 
 impl<'sess> OnDiskCache<'sess> {
     /// Creates a new `OnDiskCache` instance from the serialized data in `data`.
-    pub fn new(
-        sess: &'sess Session,
-        data: Vec<u8>,
-        start_pos: usize,
-        def_path_table: &DefPathTable,
-    ) -> Self {
+    pub fn new(sess: &'sess Session, data: Vec<u8>, start_pos: usize) -> Self {
         debug_assert!(sess.opts.incremental.is_some());
 
         // Wrap in a scope so we can borrow `data`.
@@ -210,11 +198,6 @@ impl<'sess> OnDiskCache<'sess> {
             hygiene_context: Default::default(),
             foreign_def_path_hashes: footer.foreign_def_path_hashes,
             latest_foreign_def_path_hashes: Default::default(),
-            local_def_path_hash_to_def_id: UnhashMap::from_iter(
-                def_path_table
-                    .all_def_path_hashes_and_def_ids(LOCAL_CRATE)
-                    .map(|(hash, def_id)| (hash, def_id.as_local().unwrap())),
-            ),
             def_path_hash_to_def_id_cache: Default::default(),
         }
     }
@@ -236,7 +219,6 @@ impl<'sess> OnDiskCache<'sess> {
             hygiene_context: Default::default(),
             foreign_def_path_hashes: Default::default(),
             latest_foreign_def_path_hashes: Default::default(),
-            local_def_path_hash_to_def_id: Default::default(),
             def_path_hash_to_def_id_cache: Default::default(),
         }
     }
@@ -616,7 +598,7 @@ impl<'sess> OnDiskCache<'sess> {
                 debug!("def_path_hash_to_def_id({:?})", hash);
                 // Check if the `DefPathHash` corresponds to a definition in the current
                 // crate
-                if let Some(def_id) = self.local_def_path_hash_to_def_id.get(&hash).cloned() {
+                if let Some(def_id) = tcx.definitions.local_def_path_hash_to_def_id(hash) {
                     let def_id = def_id.to_def_id();
                     e.insert(Some(def_id));
                     return Some(def_id);