foreign_modules query hash table lookups

compiler/rustc_codegen_llvm/src/attributes.rs

@@ -378,8 +378,8 @@ pub fn provide_both(providers: &mut Providers) {
             .collect::<FxHashMap<_, _>>();
 
         let mut ret = FxHashMap::default();
-        for lib in tcx.foreign_modules(cnum).iter() {
-            let module = def_id_to_native_lib.get(&lib.def_id).and_then(|s| s.wasm_import_module);
+        for (def_id, lib) in tcx.foreign_modules(cnum).iter() {
+            let module = def_id_to_native_lib.get(&def_id).and_then(|s| s.wasm_import_module);
             let module = match module {
                 Some(s) => s,
                 None => continue,

compiler/rustc_codegen_ssa/src/base.rs

@@ -860,8 +860,6 @@ pub fn provide_both(providers: &mut Providers) {
 
     providers.dllimport_foreign_items = |tcx, krate| {
         let module_map = tcx.foreign_modules(krate);
-        let module_map =
-            module_map.iter().map(|lib| (lib.def_id, lib)).collect::<FxHashMap<_, _>>();
 
         let dllimports = tcx
             .native_libraries(krate)

compiler/rustc_metadata/src/rmeta/decoder.rs

@@ -1414,12 +1414,14 @@ impl<'a, 'tcx> CrateMetadataRef<'a> {
         }
     }
 
-    fn get_foreign_modules(&self, tcx: TyCtxt<'tcx>) -> &'tcx [ForeignModule] {
+    fn get_foreign_modules(&self, tcx: TyCtxt<'tcx>) -> Lrc<FxHashMap<DefId, ForeignModule>> {
         if self.root.is_proc_macro_crate() {
             // Proc macro crates do not have any *target* foreign modules.
-            &[]
+            Lrc::new(FxHashMap::default())
         } else {
-            tcx.arena.alloc_from_iter(self.root.foreign_modules.decode((self, tcx.sess)))
+            let modules: FxHashMap<DefId, ForeignModule> =
+                self.root.foreign_modules.decode((self, tcx.sess)).map(|m| (m.def_id, m)).collect();
+            Lrc::new(modules)
         }
     }
 

compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs

@@ -6,12 +6,14 @@ use crate::rmeta::{self, encoder};
 
 use rustc_ast as ast;
 use rustc_ast::expand::allocator::AllocatorKind;
+use rustc_data_structures::stable_map::FxHashMap;
 use rustc_data_structures::svh::Svh;
 use rustc_hir as hir;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::{CrateNum, DefId, DefIdMap, CRATE_DEF_INDEX, LOCAL_CRATE};
 use rustc_hir::definitions::{DefKey, DefPath, DefPathHash};
 use rustc_middle::hir::exports::Export;
+use rustc_middle::middle::cstore::ForeignModule;
 use rustc_middle::middle::cstore::{CrateSource, CrateStore, EncodedMetadata};
 use rustc_middle::middle::exported_symbols::ExportedSymbol;
 use rustc_middle::middle::stability::DeprecationEntry;
@@ -267,9 +269,8 @@ pub fn provide(providers: &mut Providers) {
                         Some(id) => id,
                         None => return false,
                     };
-                    tcx.foreign_modules(id.krate)
-                        .iter()
-                        .find(|m| m.def_id == fm_id)
+                    let map = tcx.foreign_modules(id.krate);
+                    map.get(&fm_id)
                         .expect("failed to find foreign module")
                         .foreign_items
                         .contains(&id)
@@ -282,7 +283,9 @@ pub fn provide(providers: &mut Providers) {
         },
         foreign_modules: |tcx, cnum| {
             assert_eq!(cnum, LOCAL_CRATE);
-            &tcx.arena.alloc(foreign_modules::collect(tcx))[..]
+            let modules: FxHashMap<DefId, ForeignModule> =
+                foreign_modules::collect(tcx).into_iter().map(|m| (m.def_id, m)).collect();
+            Lrc::new(modules)
         },
         link_args: |tcx, cnum| {
             assert_eq!(cnum, LOCAL_CRATE);

compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -1502,7 +1502,7 @@ impl EncodeContext<'a, 'tcx> {
     fn encode_foreign_modules(&mut self) -> Lazy<[ForeignModule]> {
         empty_proc_macro!(self);
         let foreign_modules = self.tcx.foreign_modules(LOCAL_CRATE);
-        self.lazy(foreign_modules.iter().cloned())
+        self.lazy(foreign_modules.iter().map(|(_, m)| m).cloned())
     }
 
     fn encode_hygiene(&mut self) -> (SyntaxContextTable, ExpnDataTable) {

compiler/rustc_middle/src/query/mod.rs

@@ -1168,7 +1168,7 @@ rustc_queries! {
     }
 
     Other {
-        query foreign_modules(_: CrateNum) -> &'tcx [ForeignModule] {
+        query foreign_modules(_: CrateNum) -> Lrc<FxHashMap<DefId, ForeignModule>> {
             desc { "looking up the foreign modules of a linked crate" }
         }
 

compiler/rustc_passes/src/diagnostic_items.rs

@@ -102,7 +102,7 @@ fn collect<'tcx>(tcx: TyCtxt<'tcx>) -> FxHashMap<Symbol, DefId> {
     tcx.hir().krate().visit_all_item_likes(&mut collector);
     // FIXME(visit_all_item_likes): Foreign items are not visited
     // here, so we have to manually look at them for now.
-    for foreign_module in tcx.foreign_modules(LOCAL_CRATE) {
+    for (_, foreign_module) in tcx.foreign_modules(LOCAL_CRATE).iter() {
         for &foreign_item in foreign_module.foreign_items.iter() {
             match tcx.hir().get(tcx.hir().local_def_id_to_hir_id(foreign_item.expect_local())) {
                 hir::Node::ForeignItem(item) => {