Get rid of redundant HashSet

src/librustc/mir/interpret/mod.rs

@@ -178,7 +178,7 @@ pub fn specialized_encode_alloc_id<
         AllocKind::Fn.encode(encoder)?;
         fn_instance.encode(encoder)?;
     } else if let Some(did) = tcx.interpret_interner.get_static(alloc_id) {
-        // referring to statics doesn't need to know about their allocations, just hash the DefId
+        // referring to statics doesn't need to know about their allocations, just about its DefId
         AllocKind::Static.encode(encoder)?;
         did.encode(encoder)?;
     } else {

src/librustc/ty/maps/on_disk_cache.rs

@@ -201,7 +201,6 @@ impl<'sess> OnDiskCache<'sess> {
                 predicate_shorthands: FxHashMap(),
                 expn_info_shorthands: FxHashMap(),
                 interpret_allocs: FxHashMap(),
-                interpret_alloc_ids: FxHashSet(),
                 interpret_allocs_inverse: Vec::new(),
                 codemap: CachingCodemapView::new(tcx.sess.codemap()),
                 file_to_file_index,
@@ -284,7 +283,12 @@ impl<'sess> OnDiskCache<'sess> {
                 let mut interpret_alloc_index = Vec::new();
                 let mut n = 0;
                 loop {
-                    let new_n = encoder.interpret_alloc_ids.len();
+                    let new_n = encoder.interpret_allocs_inverse.len();
+                    // if we have found new ids, serialize those, too
+                    if n == new_n {
+                        // otherwise, abort
+                        break;
+                    }
                     for idx in n..new_n {
                         let id = encoder.interpret_allocs_inverse[idx];
                         let pos = AbsoluteBytePos::new(encoder.position());
@@ -295,11 +299,6 @@ impl<'sess> OnDiskCache<'sess> {
                             id,
                         )?;
                     }
-                    // if we have found new ids, serialize those, too
-                    if n == new_n {
-                        // otherwise, abort
-                        break;
-                    }
                     n = new_n;
                 }
                 interpret_alloc_index
@@ -802,7 +801,6 @@ struct CacheEncoder<'enc, 'a, 'tcx, E>
     expn_info_shorthands: FxHashMap<Mark, AbsoluteBytePos>,
     interpret_allocs: FxHashMap<interpret::AllocId, usize>,
     interpret_allocs_inverse: Vec<interpret::AllocId>,
-    interpret_alloc_ids: FxHashSet<interpret::AllocId>,
     codemap: CachingCodemapView<'tcx>,
     file_to_file_index: FxHashMap<*const FileMap, FileMapIndex>,
 }
@@ -839,14 +837,15 @@ impl<'enc, 'a, 'tcx, E> SpecializedEncoder<interpret::AllocId> for CacheEncoder<
     where E: 'enc + ty_codec::TyEncoder
 {
     fn specialized_encode(&mut self, alloc_id: &interpret::AllocId) -> Result<(), Self::Error> {
-        let index = if self.interpret_alloc_ids.insert(*alloc_id) {
-            let idx = self.interpret_alloc_ids.len() - 1;
-            assert_eq!(idx, self.interpret_allocs_inverse.len());
-            self.interpret_allocs_inverse.push(*alloc_id);
-            assert!(self.interpret_allocs.insert(*alloc_id, idx).is_none());
-            idx
-        } else {
-            self.interpret_allocs[alloc_id]
+        use std::collections::hash_map::Entry;
+        let index = match self.interpret_allocs.entry(*alloc_id) {
+            Entry::Occupied(e) => *e.get(),
+            Entry::Vacant(e) => {
+                let idx = self.interpret_allocs_inverse.len();
+                self.interpret_allocs_inverse.push(*alloc_id);
+                e.insert(idx);
+                idx
+            },
         };
 
         index.encode(self)

src/librustc_metadata/encoder.rs

@@ -29,7 +29,7 @@ use rustc::ty::{self, Ty, TyCtxt, ReprOptions, SymbolName};
 use rustc::ty::codec::{self as ty_codec, TyEncoder};
 
 use rustc::session::config::{self, CrateTypeProcMacro};
-use rustc::util::nodemap::{FxHashMap, FxHashSet};
+use rustc::util::nodemap::FxHashMap;
 
 use rustc_data_structures::stable_hasher::StableHasher;
 use rustc_serialize::{Encodable, Encoder, SpecializedEncoder, opaque};
@@ -62,7 +62,6 @@ pub struct EncodeContext<'a, 'tcx: 'a> {
 
     interpret_allocs: FxHashMap<interpret::AllocId, usize>,
     interpret_allocs_inverse: Vec<interpret::AllocId>,
-    interpret_alloc_ids: FxHashSet<interpret::AllocId>,
 
     // This is used to speed up Span encoding.
     filemap_cache: Lrc<FileMap>,
@@ -199,14 +198,15 @@ impl<'a, 'tcx> SpecializedEncoder<Ty<'tcx>> for EncodeContext<'a, 'tcx> {
 
 impl<'a, 'tcx> SpecializedEncoder<interpret::AllocId> for EncodeContext<'a, 'tcx> {
     fn specialized_encode(&mut self, alloc_id: &interpret::AllocId) -> Result<(), Self::Error> {
-        let index = if self.interpret_alloc_ids.insert(*alloc_id) {
-            let idx = self.interpret_alloc_ids.len() - 1;
-            assert_eq!(idx, self.interpret_allocs_inverse.len());
-            self.interpret_allocs_inverse.push(*alloc_id);
-            assert!(self.interpret_allocs.insert(*alloc_id, idx).is_none());
-            idx
-        } else {
-            self.interpret_allocs[alloc_id]
+        use std::collections::hash_map::Entry;
+        let index = match self.interpret_allocs.entry(*alloc_id) {
+            Entry::Occupied(e) => *e.get(),
+            Entry::Vacant(e) => {
+                let idx = self.interpret_allocs_inverse.len();
+                self.interpret_allocs_inverse.push(*alloc_id);
+                e.insert(idx);
+                idx
+            },
         };
 
         index.encode(self)
@@ -456,7 +456,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
             let mut n = 0;
             trace!("beginning to encode alloc ids");
             loop {
-                let new_n = self.interpret_alloc_ids.len();
+                let new_n = self.interpret_allocs_inverse.len();
                 // if we have found new ids, serialize those, too
                 if n == new_n {
                     // otherwise, abort
@@ -487,7 +487,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
         let is_proc_macro = tcx.sess.crate_types.borrow().contains(&CrateTypeProcMacro);
         let has_default_lib_allocator =
             attr::contains_name(tcx.hir.krate_attrs(), "default_lib_allocator");
-        let has_global_allocator = tcx.sess.has_global_allocator.get();
+        let has_global_allocator = *tcx.sess.has_global_allocator.get();
 
         let root = self.lazy(&CrateRoot {
             name: tcx.crate_name(LOCAL_CRATE),
@@ -1792,7 +1792,6 @@ pub fn encode_metadata<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
             filemap_cache: tcx.sess.codemap().files()[0].clone(),
             interpret_allocs: Default::default(),
             interpret_allocs_inverse: Default::default(),
-            interpret_alloc_ids: Default::default(),
         };
 
         // Encode the rustc version string in a predictable location.