Auto merge of #35984 - jonas-schievink:reproducible-builds, r=eddyb

Steps towards reproducible builds

cc #34902

Running `make dist` twice will result in a rustc tarball where only `librustc_back.so`, `librustc_llvm.so` and `librustc_trans.so` differ. Building `libstd` and `libcore` twice with the same compiler and flags produces identical artifacts.

The third commit should close #24473

21 files changed, 135 insertions, 133 deletions

diff --git a/src/librustc/infer/freshen.rs b/src/librustc/infer/freshen.rs
index beda734ee0d..f793d489cab 100644
--- a/src/librustc/infer/freshen.rs
+++ b/src/librustc/infer/freshen.rs
@@ -32,7 +32,8 @@
 
 use ty::{self, Ty, TyCtxt, TypeFoldable};
 use ty::fold::TypeFolder;
-use std::collections::hash_map::{self, Entry};
+use util::nodemap::FnvHashMap;
+use std::collections::hash_map::Entry;
 
 use super::InferCtxt;
 use super::unify_key::ToType;
@@ -40,7 +41,7 @@ use super::unify_key::ToType;
 pub struct TypeFreshener<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
     infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
     freshen_count: u32,
-    freshen_map: hash_map::HashMap<ty::InferTy, Ty<'tcx>>,
+    freshen_map: FnvHashMap<ty::InferTy, Ty<'tcx>>,
 }
 
 impl<'a, 'gcx, 'tcx> TypeFreshener<'a, 'gcx, 'tcx> {
@@ -49,7 +50,7 @@ impl<'a, 'gcx, 'tcx> TypeFreshener<'a, 'gcx, 'tcx> {
         TypeFreshener {
             infcx: infcx,
             freshen_count: 0,
-            freshen_map: hash_map::HashMap::new(),
+            freshen_map: FnvHashMap(),
         }
     }
 
diff --git a/src/librustc/middle/dead.rs b/src/librustc/middle/dead.rs
index 37366f38974..f44b149a846 100644
--- a/src/librustc/middle/dead.rs
+++ b/src/librustc/middle/dead.rs
@@ -22,8 +22,8 @@ use ty::{self, TyCtxt};
 use hir::def::Def;
 use hir::def_id::{DefId};
 use lint;
+use util::nodemap::FnvHashSet;
 
-use std::collections::HashSet;
 use syntax::{ast, codemap};
 use syntax::attr;
 use syntax_pos;
@@ -48,7 +48,7 @@ fn should_explore<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 struct MarkSymbolVisitor<'a, 'tcx: 'a> {
     worklist: Vec<ast::NodeId>,
     tcx: TyCtxt<'a, 'tcx, 'tcx>,
-    live_symbols: Box<HashSet<ast::NodeId>>,
+    live_symbols: Box<FnvHashSet<ast::NodeId>>,
     struct_has_extern_repr: bool,
     ignore_non_const_paths: bool,
     inherited_pub_visibility: bool,
@@ -61,7 +61,7 @@ impl<'a, 'tcx> MarkSymbolVisitor<'a, 'tcx> {
         MarkSymbolVisitor {
             worklist: worklist,
             tcx: tcx,
-            live_symbols: box HashSet::new(),
+            live_symbols: box FnvHashSet(),
             struct_has_extern_repr: false,
             ignore_non_const_paths: false,
             inherited_pub_visibility: false,
@@ -162,7 +162,7 @@ impl<'a, 'tcx> MarkSymbolVisitor<'a, 'tcx> {
     }
 
     fn mark_live_symbols(&mut self) {
-        let mut scanned = HashSet::new();
+        let mut scanned = FnvHashSet();
         while !self.worklist.is_empty() {
             let id = self.worklist.pop().unwrap();
             if scanned.contains(&id) {
@@ -395,7 +395,7 @@ fn create_and_seed_worklist<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 fn find_live<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                        access_levels: &privacy::AccessLevels,
                        krate: &hir::Crate)
-                       -> Box<HashSet<ast::NodeId>> {
+                       -> Box<FnvHashSet<ast::NodeId>> {
     let worklist = create_and_seed_worklist(tcx, access_levels, krate);
     let mut symbol_visitor = MarkSymbolVisitor::new(tcx, worklist);
     symbol_visitor.mark_live_symbols();
@@ -413,7 +413,7 @@ fn get_struct_ctor_id(item: &hir::Item) -> Option<ast::NodeId> {
 
 struct DeadVisitor<'a, 'tcx: 'a> {
     tcx: TyCtxt<'a, 'tcx, 'tcx>,
-    live_symbols: Box<HashSet<ast::NodeId>>,
+    live_symbols: Box<FnvHashSet<ast::NodeId>>,
 }
 
 impl<'a, 'tcx> DeadVisitor<'a, 'tcx> {
diff --git a/src/librustc/middle/reachable.rs b/src/librustc/middle/reachable.rs
index 6ea0fa20c57..e29a7cf9d68 100644
--- a/src/librustc/middle/reachable.rs
+++ b/src/librustc/middle/reachable.rs
@@ -22,9 +22,8 @@ use hir::def_id::DefId;
 use ty::{self, TyCtxt};
 use middle::privacy;
 use session::config;
-use util::nodemap::NodeSet;
+use util::nodemap::{NodeSet, FnvHashSet};
 
-use std::collections::HashSet;
 use syntax::abi::Abi;
 use syntax::ast;
 use syntax::attr;
@@ -204,7 +203,7 @@ impl<'a, 'tcx> ReachableContext<'a, 'tcx> {
 
     // Step 2: Mark all symbols that the symbols on the worklist touch.
     fn propagate(&mut self) {
-        let mut scanned = HashSet::new();
+        let mut scanned = FnvHashSet();
         loop {
             let search_item = match self.worklist.pop() {
                 Some(item) => item,
diff --git a/src/librustc_metadata/encoder.rs b/src/librustc_metadata/encoder.rs
index 9a668b69b2e..f99bdf3b890 100644
--- a/src/librustc_metadata/encoder.rs
+++ b/src/librustc_metadata/encoder.rs
@@ -862,8 +862,13 @@ fn encode_xrefs<'a, 'tcx>(ecx: &EncodeContext<'a, 'tcx>,
                           xrefs: FnvHashMap<XRef<'tcx>, u32>)
 {
     let mut xref_positions = vec![0; xrefs.len()];
+
+    // Encode XRefs sorted by their ID
+    let mut sorted_xrefs: Vec<_> = xrefs.into_iter().collect();
+    sorted_xrefs.sort_by_key(|&(_, id)| id);
+
     rbml_w.start_tag(tag_xref_data);
-    for (xref, id) in xrefs.into_iter() {
+    for (xref, id) in sorted_xrefs.into_iter() {
         xref_positions[id as usize] = rbml_w.mark_stable_position() as u32;
         match xref {
             XRef::Predicate(p) => {
diff --git a/src/librustc_metadata/loader.rs b/src/librustc_metadata/loader.rs
index 2345cd9a92a..b2c87db8ef5 100644
--- a/src/librustc_metadata/loader.rs
+++ b/src/librustc_metadata/loader.rs
@@ -221,6 +221,7 @@ use rustc::session::Session;
 use rustc::session::filesearch::{FileSearch, FileMatches, FileDoesntMatch};
 use rustc::session::search_paths::PathKind;
 use rustc::util::common;
+use rustc::util::nodemap::FnvHashMap;
 
 use rustc_llvm as llvm;
 use rustc_llvm::{False, ObjectFile, mk_section_iter};
@@ -230,7 +231,6 @@ use syntax_pos::Span;
 use rustc_back::target::Target;
 
 use std::cmp;
-use std::collections::HashMap;
 use std::fmt;
 use std::fs;
 use std::io;
@@ -413,7 +413,7 @@ impl<'a> Context<'a> {
         let rlib_prefix = format!("lib{}", self.crate_name);
         let staticlib_prefix = format!("{}{}", staticpair.0, self.crate_name);
 
-        let mut candidates = HashMap::new();
+        let mut candidates = FnvHashMap();
         let mut staticlibs = vec!();
 
         // First, find all possible candidate rlibs and dylibs purely based on
@@ -456,7 +456,7 @@ impl<'a> Context<'a> {
 
             let hash_str = hash.to_string();
             let slot = candidates.entry(hash_str)
-                                 .or_insert_with(|| (HashMap::new(), HashMap::new()));
+                                 .or_insert_with(|| (FnvHashMap(), FnvHashMap()));
             let (ref mut rlibs, ref mut dylibs) = *slot;
             fs::canonicalize(path).map(|p| {
                 if rlib {
@@ -477,7 +477,7 @@ impl<'a> Context<'a> {
         // A Library candidate is created if the metadata for the set of
         // libraries corresponds to the crate id and hash criteria that this
         // search is being performed for.
-        let mut libraries = HashMap::new();
+        let mut libraries = FnvHashMap();
         for (_hash, (rlibs, dylibs)) in candidates {
             let mut slot = None;
             let rlib = self.extract_one(rlibs, CrateFlavor::Rlib, &mut slot);
@@ -527,7 +527,7 @@ impl<'a> Context<'a> {
     // read the metadata from it if `*slot` is `None`. If the metadata couldn't
     // be read, it is assumed that the file isn't a valid rust library (no
     // errors are emitted).
-    fn extract_one(&mut self, m: HashMap<PathBuf, PathKind>, flavor: CrateFlavor,
+    fn extract_one(&mut self, m: FnvHashMap<PathBuf, PathKind>, flavor: CrateFlavor,
                    slot: &mut Option<(Svh, MetadataBlob)>) -> Option<(PathBuf, PathKind)> {
         let mut ret: Option<(PathBuf, PathKind)> = None;
         let mut error = 0;
@@ -669,8 +669,8 @@ impl<'a> Context<'a> {
         // rlibs/dylibs.
         let sess = self.sess;
         let dylibname = self.dylibname();
-        let mut rlibs = HashMap::new();
-        let mut dylibs = HashMap::new();
+        let mut rlibs = FnvHashMap();
+        let mut dylibs = FnvHashMap();
         {
             let locs = locs.map(|l| PathBuf::from(l)).filter(|loc| {
                 if !loc.exists() {
diff --git a/src/librustc_metadata/macro_import.rs b/src/librustc_metadata/macro_import.rs
index b2a2dcf90fa..2cd60f04e69 100644
--- a/src/librustc_metadata/macro_import.rs
+++ b/src/librustc_metadata/macro_import.rs
@@ -14,8 +14,8 @@ use creader::CrateReader;
 use cstore::CStore;
 
 use rustc::session::Session;
+use rustc::util::nodemap::{FnvHashSet, FnvHashMap};
 
-use std::collections::{HashSet, HashMap};
 use syntax::parse::token;
 use syntax::ast;
 use syntax::attr;
@@ -45,13 +45,13 @@ pub fn call_bad_macro_reexport(a: &Session, b: Span) {
     span_err!(a, b, E0467, "bad macro reexport");
 }
 
-pub type MacroSelection = HashMap<token::InternedString, Span>;
+pub type MacroSelection = FnvHashMap<token::InternedString, Span>;
 
 impl<'a> ext::base::MacroLoader for MacroLoader<'a> {
     fn load_crate(&mut self, extern_crate: &ast::Item, allows_macros: bool) -> Vec<ast::MacroDef> {
         // Parse the attributes relating to macros.
-        let mut import = Some(HashMap::new());  // None => load all
-        let mut reexport = HashMap::new();
+        let mut import = Some(FnvHashMap());  // None => load all
+        let mut reexport = FnvHashMap();
 
         for attr in &extern_crate.attrs {
             let mut used = true;
@@ -120,7 +120,7 @@ impl<'a> MacroLoader<'a> {
         }
 
         let mut macros = Vec::new();
-        let mut seen = HashSet::new();
+        let mut seen = FnvHashSet();
 
         for mut def in self.reader.read_exported_macros(vi) {
             let name = def.ident.name.as_str();
diff --git a/src/librustc_resolve/assign_ids.rs b/src/librustc_resolve/assign_ids.rs
index 70e566de8a7..a9e3c6ffe9e 100644
--- a/src/librustc_resolve/assign_ids.rs
+++ b/src/librustc_resolve/assign_ids.rs
@@ -10,6 +10,7 @@
 
 use Resolver;
 use rustc::session::Session;
+use rustc::util::nodemap::FnvHashMap;
 use syntax::ast;
 use syntax::ext::hygiene::Mark;
 use syntax::fold::{self, Folder};
@@ -17,7 +18,6 @@ use syntax::ptr::P;
 use syntax::util::move_map::MoveMap;
 use syntax::util::small_vector::SmallVector;
 
-use std::collections::HashMap;
 use std::mem;
 
 impl<'a> Resolver<'a> {
@@ -31,7 +31,7 @@ impl<'a> Resolver<'a> {
 
 struct NodeIdAssigner<'a> {
     sess: &'a Session,
-    macros_at_scope: &'a mut HashMap<ast::NodeId, Vec<Mark>>,
+    macros_at_scope: &'a mut FnvHashMap<ast::NodeId, Vec<Mark>>,
 }
 
 impl<'a> Folder for NodeIdAssigner<'a> {
diff --git a/src/librustc_resolve/lib.rs b/src/librustc_resolve/lib.rs
index 5641a50ccac..6a4a48377c7 100644
--- a/src/librustc_resolve/lib.rs
+++ b/src/librustc_resolve/lib.rs
@@ -68,7 +68,6 @@ use syntax::ast::{PathSegment, PathParameters, QSelf, TraitItemKind, TraitRef, T
 use syntax_pos::Span;
 use errors::DiagnosticBuilder;
 
-use std::collections::{HashMap, HashSet};
 use std::cell::{Cell, RefCell};
 use std::fmt;
 use std::mem::replace;
@@ -498,7 +497,7 @@ struct BindingInfo {
 }
 
 // Map from the name in a pattern to its binding mode.
-type BindingMap = HashMap<ast::Ident, BindingInfo>;
+type BindingMap = FnvHashMap<ast::Ident, BindingInfo>;
 
 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
 enum PatternSource {
@@ -703,14 +702,14 @@ enum ModulePrefixResult<'a> {
 /// One local scope.
 #[derive(Debug)]
 struct Rib<'a> {
-    bindings: HashMap<ast::Ident, Def>,
+    bindings: FnvHashMap<ast::Ident, Def>,
     kind: RibKind<'a>,
 }
 
 impl<'a> Rib<'a> {
     fn new(kind: RibKind<'a>) -> Rib<'a> {
         Rib {
-            bindings: HashMap::new(),
+            bindings: FnvHashMap(),
             kind: kind,
         }
     }
@@ -773,7 +772,7 @@ pub struct ModuleS<'a> {
     // is the NodeId of the local `extern crate` item (otherwise, `extern_crate_id` is None).
     extern_crate_id: Option<NodeId>,
 
-    resolutions: RefCell<HashMap<(Name, Namespace), &'a RefCell<NameResolution<'a>>>>,
+    resolutions: RefCell<FnvHashMap<(Name, Namespace), &'a RefCell<NameResolution<'a>>>>,
 
     no_implicit_prelude: Cell<bool>,
 
@@ -797,7 +796,7 @@ impl<'a> ModuleS<'a> {
             parent_link: parent_link,
             def: def,
             extern_crate_id: None,
-            resolutions: RefCell::new(HashMap::new()),
+            resolutions: RefCell::new(FnvHashMap()),
             no_implicit_prelude: Cell::new(false),
             glob_importers: RefCell::new(Vec::new()),
             globs: RefCell::new((Vec::new())),
@@ -930,12 +929,12 @@ impl<'a> NameBinding<'a> {
 
 /// Interns the names of the primitive types.
 struct PrimitiveTypeTable {
-    primitive_types: HashMap<Name, PrimTy>,
+    primitive_types: FnvHashMap<Name, PrimTy>,
 }
 
 impl PrimitiveTypeTable {
     fn new() -> PrimitiveTypeTable {
-        let mut table = PrimitiveTypeTable { primitive_types: HashMap::new() };
+        let mut table = PrimitiveTypeTable { primitive_types: FnvHashMap() };
 
         table.intern("bool", TyBool);
         table.intern("char", TyChar);
@@ -969,7 +968,7 @@ pub struct Resolver<'a> {
 
     // Maps the node id of a statement to the expansions of the `macro_rules!`s
     // immediately above the statement (if appropriate).
-    macros_at_scope: HashMap<NodeId, Vec<Mark>>,
+    macros_at_scope: FnvHashMap<NodeId, Vec<Mark>>,
 
     graph_root: Module<'a>,
 
@@ -1043,8 +1042,8 @@ pub struct Resolver<'a> {
     // all imports, but only glob imports are actually interesting).
     pub glob_map: GlobMap,
 
-    used_imports: HashSet<(NodeId, Namespace)>,
-    used_crates: HashSet<CrateNum>,
+    used_imports: FnvHashSet<(NodeId, Namespace)>,
+    used_crates: FnvHashSet<CrateNum>,
     pub maybe_unused_trait_imports: NodeSet,
 
     privacy_errors: Vec<PrivacyError<'a>>,
@@ -1164,7 +1163,7 @@ impl<'a> Resolver<'a> {
             session: session,
 
             definitions: Definitions::new(),
-            macros_at_scope: HashMap::new(),
+            macros_at_scope: FnvHashMap(),
 
             // The outermost module has def ID 0; this is not reflected in the
             // AST.
@@ -1199,8 +1198,8 @@ impl<'a> Resolver<'a> {
             make_glob_map: make_glob_map == MakeGlobMap::Yes,
             glob_map: NodeMap(),
 
-            used_imports: HashSet::new(),
-            used_crates: HashSet::new(),
+            used_imports: FnvHashSet(),
+            used_crates: FnvHashSet(),
             maybe_unused_trait_imports: NodeSet(),
 
             privacy_errors: Vec::new(),
@@ -1729,7 +1728,7 @@ impl<'a> Resolver<'a> {
         match type_parameters {
             HasTypeParameters(generics, rib_kind) => {
                 let mut function_type_rib = Rib::new(rib_kind);
-                let mut seen_bindings = HashMap::new();
+                let mut seen_bindings = FnvHashMap();
                 for type_parameter in &generics.ty_params {
                     let name = type_parameter.ident.name;
                     debug!("with_type_parameter_rib: {}", type_parameter.id);
@@ -1793,7 +1792,7 @@ impl<'a> Resolver<'a> {
         self.label_ribs.push(Rib::new(rib_kind));
 
         // Add each argument to the rib.
-        let mut bindings_list = HashMap::new();
+        let mut bindings_list = FnvHashMap();
         for argument in &declaration.inputs {
             self.resolve_pattern(&argument.pat, PatternSource::FnParam, &mut bindings_list);
 
@@ -1994,7 +1993,7 @@ impl<'a> Resolver<'a> {
         walk_list!(self, visit_expr, &local.init);
 
         // Resolve the pattern.
-        self.resolve_pattern(&local.pat, PatternSource::Let, &mut HashMap::new());
+        self.resolve_pattern(&local.pat, PatternSource::Let, &mut FnvHashMap());
     }
 
     // build a map from pattern identifiers to binding-info's.
@@ -2002,7 +2001,7 @@ impl<'a> Resolver<'a> {
     // that expands into an or-pattern where one 'x' was from the
     // user and one 'x' came from the macro.
     fn binding_mode_map(&mut self, pat: &Pat) -> BindingMap {
-        let mut binding_map = HashMap::new();
+        let mut binding_map = FnvHashMap();
 
         pat.walk(&mut |pat| {
             if let PatKind::Ident(binding_mode, ident, ref sub_pat) = pat.node {
@@ -2062,7 +2061,7 @@ impl<'a> Resolver<'a> {
     fn resolve_arm(&mut self, arm: &Arm) {
         self.value_ribs.push(Rib::new(NormalRibKind));
 
-        let mut bindings_list = HashMap::new();
+        let mut bindings_list = FnvHashMap();
         for pattern in &arm.pats {
             self.resolve_pattern(&pattern, PatternSource::Match, &mut bindings_list);
         }
@@ -2202,7 +2201,7 @@ impl<'a> Resolver<'a> {
                      pat_id: NodeId,
                      outer_pat_id: NodeId,
                      pat_src: PatternSource,
-                     bindings: &mut HashMap<ast::Ident, NodeId>)
+                     bindings: &mut FnvHashMap<ast::Ident, NodeId>)
                      -> PathResolution {
         // Add the binding to the local ribs, if it
         // doesn't already exist in the bindings map. (We
@@ -2303,7 +2302,7 @@ impl<'a> Resolver<'a> {
                        pat_src: PatternSource,
                        // Maps idents to the node ID for the
                        // outermost pattern that binds them.
-                       bindings: &mut HashMap<ast::Ident, NodeId>) {
+                       bindings: &mut FnvHashMap<ast::Ident, NodeId>) {
         // Visit all direct subpatterns of this pattern.
         let outer_pat_id = pat.id;
         pat.walk(&mut |pat| {
@@ -3016,7 +3015,7 @@ impl<'a> Resolver<'a> {
                 self.visit_expr(subexpression);
 
                 self.value_ribs.push(Rib::new(NormalRibKind));
-                self.resolve_pattern(pattern, PatternSource::IfLet, &mut HashMap::new());
+                self.resolve_pattern(pattern, PatternSource::IfLet, &mut FnvHashMap());
                 self.visit_block(if_block);
                 self.value_ribs.pop();
 
@@ -3026,7 +3025,7 @@ impl<'a> Resolver<'a> {
             ExprKind::WhileLet(ref pattern, ref subexpression, ref block, label) => {
                 self.visit_expr(subexpression);
                 self.value_ribs.push(Rib::new(NormalRibKind));
-                self.resolve_pattern(pattern, PatternSource::WhileLet, &mut HashMap::new());
+                self.resolve_pattern(pattern, PatternSource::WhileLet, &mut FnvHashMap());
 
                 self.resolve_labeled_block(label.map(|l| l.node), expr.id, block);
 
@@ -3036,7 +3035,7 @@ impl<'a> Resolver<'a> {
             ExprKind::ForLoop(ref pattern, ref subexpression, ref block, label) => {
                 self.visit_expr(subexpression);
                 self.value_ribs.push(Rib::new(NormalRibKind));
-                self.resolve_pattern(pattern, PatternSource::For, &mut HashMap::new());
+                self.resolve_pattern(pattern, PatternSource::For, &mut FnvHashMap());
 
                 self.resolve_labeled_block(label.map(|l| l.node), expr.id, block);
 
@@ -3297,7 +3296,7 @@ impl<'a> Resolver<'a> {
 
     fn report_privacy_errors(&self) {
         if self.privacy_errors.len() == 0 { return }
-        let mut reported_spans = HashSet::new();
+        let mut reported_spans = FnvHashSet();
         for &PrivacyError(span, name, binding) in &self.privacy_errors {
             if !reported_spans.insert(span) { continue }
             if binding.is_extern_crate() {
diff --git a/src/librustc_trans/base.rs b/src/librustc_trans/base.rs
index 5e431193a2c..a183fc0858a 100644
--- a/src/librustc_trans/base.rs
+++ b/src/librustc_trans/base.rs
@@ -80,14 +80,13 @@ use type_of;
 use value::Value;
 use Disr;
 use util::sha2::Sha256;
-use util::nodemap::{NodeSet, FnvHashSet};
+use util::nodemap::{NodeSet, FnvHashMap, FnvHashSet};
 
 use arena::TypedArena;
 use libc::c_uint;
 use std::ffi::{CStr, CString};
 use std::borrow::Cow;
 use std::cell::{Cell, RefCell};
-use std::collections::HashMap;
 use std::ptr;
 use std::rc::Rc;
 use std::str;
@@ -1915,7 +1914,7 @@ fn collect_and_partition_translation_items<'a, 'tcx>(scx: &SharedCrateContext<'a
     }
 
     if scx.sess().opts.debugging_opts.print_trans_items.is_some() {
-        let mut item_to_cgus = HashMap::new();
+        let mut item_to_cgus = FnvHashMap();
 
         for cgu in &codegen_units {
             for (&trans_item, &linkage) in cgu.items() {
diff --git a/src/librustc_typeck/check/intrinsic.rs b/src/librustc_typeck/check/intrinsic.rs
index ed3e645eeeb..79b6ae0c83f 100644
--- a/src/librustc_typeck/check/intrinsic.rs
+++ b/src/librustc_typeck/check/intrinsic.rs
@@ -16,9 +16,9 @@ use rustc::infer::TypeOrigin;
 use rustc::ty::subst::Substs;
 use rustc::ty::FnSig;
 use rustc::ty::{self, Ty};
+use rustc::util::nodemap::FnvHashMap;
 use {CrateCtxt, require_same_types};
 
-use std::collections::{HashMap};
 use syntax::abi::Abi;
 use syntax::ast;
 use syntax::parse::token;
@@ -370,7 +370,7 @@ pub fn check_platform_intrinsic_type(ccx: &CrateCtxt,
                         return
                     }
 
-                    let mut structural_to_nomimal = HashMap::new();
+                    let mut structural_to_nomimal = FnvHashMap();
 
                     let sig = tcx.no_late_bound_regions(i_ty.ty.fn_sig()).unwrap();
                     if intr.inputs.len() != sig.inputs.len() {
@@ -410,7 +410,7 @@ fn match_intrinsic_type_to_type<'tcx, 'a>(
         ccx: &CrateCtxt<'a, 'tcx>,
         position: &str,
         span: Span,
-        structural_to_nominal: &mut HashMap<&'a intrinsics::Type, ty::Ty<'tcx>>,
+        structural_to_nominal: &mut FnvHashMap<&'a intrinsics::Type, ty::Ty<'tcx>>,
         expected: &'a intrinsics::Type, t: ty::Ty<'tcx>)
 {
     use intrinsics::Type::*;
diff --git a/src/librustc_typeck/check/method/probe.rs b/src/librustc_typeck/check/method/probe.rs
index a64982cd1bf..29366823fff 100644
--- a/src/librustc_typeck/check/method/probe.rs
+++ b/src/librustc_typeck/check/method/probe.rs
@@ -20,10 +20,10 @@ use rustc::ty::subst::{Subst, Substs};
 use rustc::traits;
 use rustc::ty::{self, Ty, ToPolyTraitRef, TraitRef, TypeFoldable};
 use rustc::infer::{InferOk, TypeOrigin};
+use rustc::util::nodemap::FnvHashSet;
 use syntax::ast;
 use syntax_pos::{Span, DUMMY_SP};
 use rustc::hir;
-use std::collections::HashSet;
 use std::mem;
 use std::ops::Deref;
 use std::rc::Rc;
@@ -40,7 +40,7 @@ struct ProbeContext<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
     opt_simplified_steps: Option<Vec<ty::fast_reject::SimplifiedType>>,
     inherent_candidates: Vec<Candidate<'tcx>>,
     extension_candidates: Vec<Candidate<'tcx>>,
-    impl_dups: HashSet<DefId>,
+    impl_dups: FnvHashSet<DefId>,
     import_id: Option<ast::NodeId>,
 
     /// Collects near misses when the candidate functions are missing a `self` keyword and is only
@@ -255,7 +255,7 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
             item_name: item_name,
             inherent_candidates: Vec::new(),
             extension_candidates: Vec::new(),
-            impl_dups: HashSet::new(),
+            impl_dups: FnvHashSet(),
             import_id: None,
             steps: Rc::new(steps),
             opt_simplified_steps: opt_simplified_steps,
@@ -574,7 +574,7 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
                                                          expr_id: ast::NodeId)
                                                          -> Result<(), MethodError<'tcx>>
     {
-        let mut duplicates = HashSet::new();
+        let mut duplicates = FnvHashSet();
         let opt_applicable_traits = self.tcx.trait_map.get(&expr_id);
         if let Some(applicable_traits) = opt_applicable_traits {
             for trait_candidate in applicable_traits {
@@ -591,7 +591,7 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
     }
 
     fn assemble_extension_candidates_for_all_traits(&mut self) -> Result<(), MethodError<'tcx>> {
-        let mut duplicates = HashSet::new();
+        let mut duplicates = FnvHashSet();
         for trait_info in suggest::all_traits(self.ccx) {
             if duplicates.insert(trait_info.def_id) {
                 self.assemble_extension_candidates_for_trait(trait_info.def_id)?;
diff --git a/src/librustc_typeck/check/mod.rs b/src/librustc_typeck/check/mod.rs
index e972a5ca7fb..fb24971c425 100644
--- a/src/librustc_typeck/check/mod.rs
+++ b/src/librustc_typeck/check/mod.rs
@@ -104,10 +104,9 @@ use CrateCtxt;
 use TypeAndSubsts;
 use lint;
 use util::common::{block_query, ErrorReported, indenter, loop_query};
-use util::nodemap::{DefIdMap, FnvHashMap, NodeMap};
+use util::nodemap::{DefIdMap, FnvHashMap, FnvHashSet, NodeMap};
 
 use std::cell::{Cell, Ref, RefCell};
-use std::collections::{HashSet};
 use std::mem::replace;
 use std::ops::Deref;
 use syntax::abi::Abi;
@@ -2045,7 +2044,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                     .filter_map(|t| self.default(t).map(|d| (t, d)))
                     .collect();
 
-            let mut unbound_tyvars = HashSet::new();
+            let mut unbound_tyvars = FnvHashSet();
 
             debug!("select_all_obligations_and_apply_defaults: defaults={:?}", default_map);
 
@@ -2192,7 +2191,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
     // table then apply defaults until we find a conflict. That default must be the one
     // that caused conflict earlier.
     fn find_conflicting_default(&self,
-                                unbound_vars: &HashSet<Ty<'tcx>>,
+                                unbound_vars: &FnvHashSet<Ty<'tcx>>,
                                 default_map: &FnvHashMap<&Ty<'tcx>, type_variable::Default<'tcx>>,
                                 conflict: Ty<'tcx>)
                                 -> Option<type_variable::Default<'tcx>> {
diff --git a/src/librustc_typeck/check/wfcheck.rs b/src/librustc_typeck/check/wfcheck.rs
index 38ec7ba686f..6b6a688bf1d 100644
--- a/src/librustc_typeck/check/wfcheck.rs
+++ b/src/librustc_typeck/check/wfcheck.rs
@@ -16,8 +16,8 @@ use middle::region::{CodeExtent};
 use rustc::infer::TypeOrigin;
 use rustc::traits;
 use rustc::ty::{self, Ty, TyCtxt};
+use rustc::util::nodemap::FnvHashSet;
 
-use std::collections::HashSet;
 use syntax::ast;
 use syntax_pos::Span;
 use errors::DiagnosticBuilder;
@@ -456,7 +456,7 @@ impl<'ccx, 'gcx> CheckTypeWellFormedVisitor<'ccx, 'gcx> {
         assert_eq!(ty_predicates.parent, None);
         let variances = self.tcx().item_variances(item_def_id);
 
-        let mut constrained_parameters: HashSet<_> =
+        let mut constrained_parameters: FnvHashSet<_> =
             variances[ast_generics.lifetimes.len()..]
                      .iter().enumerate()
                      .filter(|&(_, &variance)| variance != ty::Bivariant)
@@ -519,7 +519,7 @@ impl<'ccx, 'gcx> CheckTypeWellFormedVisitor<'ccx, 'gcx> {
 
 fn reject_shadowing_type_parameters(tcx: TyCtxt, span: Span, generics: &ty::Generics) {
     let parent = tcx.lookup_generics(generics.parent.unwrap());
-    let impl_params: HashSet<_> = parent.types.iter().map(|tp| tp.name).collect();
+    let impl_params: FnvHashSet<_> = parent.types.iter().map(|tp| tp.name).collect();
 
     for method_param in &generics.types {
         if impl_params.contains(&method_param.name) {
diff --git a/src/librustc_typeck/collect.rs b/src/librustc_typeck/collect.rs
index 0074d3930e2..30b9d155870 100644
--- a/src/librustc_typeck/collect.rs
+++ b/src/librustc_typeck/collect.rs
@@ -73,13 +73,12 @@ use rustc::ty::util::IntTypeExt;
 use rscope::*;
 use rustc::dep_graph::DepNode;
 use util::common::{ErrorReported, MemoizationMap};
-use util::nodemap::{NodeMap, FnvHashMap};
+use util::nodemap::{NodeMap, FnvHashMap, FnvHashSet};
 use {CrateCtxt, write_ty_to_tcx};
 
 use rustc_const_math::ConstInt;
 
 use std::cell::RefCell;
-use std::collections::HashSet;
 use std::collections::hash_map::Entry::{Occupied, Vacant};
 use std::rc::Rc;
 
@@ -1927,9 +1926,9 @@ fn compute_object_lifetime_default<'a,'tcx>(ccx: &CrateCtxt<'a,'tcx>,
 {
     let inline_bounds = from_bounds(ccx, param_bounds);
     let where_bounds = from_predicates(ccx, param_id, &where_clause.predicates);
-    let all_bounds: HashSet<_> = inline_bounds.into_iter()
-                                              .chain(where_bounds)
-                                              .collect();
+    let all_bounds: FnvHashSet<_> = inline_bounds.into_iter()
+                                                 .chain(where_bounds)
+                                                 .collect();
     return if all_bounds.len() > 1 {
         ty::ObjectLifetimeDefault::Ambiguous
     } else if all_bounds.len() == 0 {
@@ -2146,7 +2145,7 @@ fn enforce_impl_params_are_constrained<'a, 'tcx>(ccx: &CrateCtxt<'a, 'tcx>,
     // The trait reference is an input, so find all type parameters
     // reachable from there, to start (if this is an inherent impl,
     // then just examine the self type).
-    let mut input_parameters: HashSet<_> =
+    let mut input_parameters: FnvHashSet<_> =
         ctp::parameters_for(&impl_scheme.ty, false).into_iter().collect();
     if let Some(ref trait_ref) = impl_trait_ref {
         input_parameters.extend(ctp::parameters_for(trait_ref, false));
@@ -2175,7 +2174,7 @@ fn enforce_impl_lifetimes_are_constrained<'a, 'tcx>(ccx: &CrateCtxt<'a, 'tcx>,
     let impl_predicates = ccx.tcx.lookup_predicates(impl_def_id);
     let impl_trait_ref = ccx.tcx.impl_trait_ref(impl_def_id);
 
-    let mut input_parameters: HashSet<_> =
+    let mut input_parameters: FnvHashSet<_> =
         ctp::parameters_for(&impl_scheme.ty, false).into_iter().collect();
     if let Some(ref trait_ref) = impl_trait_ref {
         input_parameters.extend(ctp::parameters_for(trait_ref, false));
@@ -2183,7 +2182,7 @@ fn enforce_impl_lifetimes_are_constrained<'a, 'tcx>(ccx: &CrateCtxt<'a, 'tcx>,
     ctp::identify_constrained_type_params(
         &impl_predicates.predicates.as_slice(), impl_trait_ref, &mut input_parameters);
 
-    let lifetimes_in_associated_types: HashSet<_> = impl_items.iter()
+    let lifetimes_in_associated_types: FnvHashSet<_> = impl_items.iter()
         .map(|item| ccx.tcx.impl_or_trait_item(ccx.tcx.map.local_def_id(item.id)))
         .filter_map(|item| match item {
             ty::TypeTraitItem(ref assoc_ty) => assoc_ty.ty,
diff --git a/src/librustc_typeck/constrained_type_params.rs b/src/librustc_typeck/constrained_type_params.rs
index 637df52e3cb..9e5c3a5d575 100644
--- a/src/librustc_typeck/constrained_type_params.rs
+++ b/src/librustc_typeck/constrained_type_params.rs
@@ -10,7 +10,7 @@
 
 use rustc::ty::{self, Ty};
 use rustc::ty::fold::{TypeFoldable, TypeVisitor};
-use std::collections::HashSet;
+use rustc::util::nodemap::FnvHashSet;
 
 #[derive(Clone, PartialEq, Eq, Hash, Debug)]
 pub enum Parameter {
@@ -71,7 +71,7 @@ impl<'tcx> TypeVisitor<'tcx> for ParameterCollector {
 
 pub fn identify_constrained_type_params<'tcx>(predicates: &[ty::Predicate<'tcx>],
                                               impl_trait_ref: Option<ty::TraitRef<'tcx>>,
-                                              input_parameters: &mut HashSet<Parameter>)
+                                              input_parameters: &mut FnvHashSet<Parameter>)
 {
     let mut predicates = predicates.to_owned();
     setup_constraining_predicates(&mut predicates, impl_trait_ref, input_parameters);
@@ -120,7 +120,7 @@ pub fn identify_constrained_type_params<'tcx>(predicates: &[ty::Predicate<'tcx>]
 /// think of any.
 pub fn setup_constraining_predicates<'tcx>(predicates: &mut [ty::Predicate<'tcx>],
                                            impl_trait_ref: Option<ty::TraitRef<'tcx>>,
-                                           input_parameters: &mut HashSet<Parameter>)
+                                           input_parameters: &mut FnvHashSet<Parameter>)
 {
     // The canonical way of doing the needed topological sort
     // would be a DFS, but getting the graph and its ownership
diff --git a/src/librustdoc/clean/inline.rs b/src/librustdoc/clean/inline.rs
index 013433336a1..20d4c417655 100644
--- a/src/librustdoc/clean/inline.rs
+++ b/src/librustdoc/clean/inline.rs
@@ -10,7 +10,6 @@
 
 //! Support for inlining external documentation into the current AST.
 
-use std::collections::HashSet;
 use std::iter::once;
 
 use syntax::ast;
@@ -21,6 +20,7 @@ use rustc::hir::def::Def;
 use rustc::hir::def_id::DefId;
 use rustc::hir::print as pprust;
 use rustc::ty::{self, TyCtxt};
+use rustc::util::nodemap::FnvHashSet;
 
 use rustc_const_eval::lookup_const_by_id;
 
@@ -425,7 +425,7 @@ pub fn build_impl<'a, 'tcx>(cx: &DocContext,
                 .into_iter()
                 .map(|meth| meth.name.to_string())
                 .collect()
-    }).unwrap_or(HashSet::new());
+    }).unwrap_or(FnvHashSet());
 
     ret.push(clean::Item {
         inner: clean::ImplItem(clean::Impl {
@@ -461,7 +461,7 @@ fn build_module<'a, 'tcx>(cx: &DocContext, tcx: TyCtxt<'a, 'tcx, 'tcx>,
         // If we're reexporting a reexport it may actually reexport something in
         // two namespaces, so the target may be listed twice. Make sure we only
         // visit each node at most once.
-        let mut visited = HashSet::new();
+        let mut visited = FnvHashSet();
         for item in tcx.sess.cstore.item_children(did) {
             match item.def {
                 cstore::DlDef(Def::ForeignMod(did)) => {
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index c8620254b6f..cd425b7c9eb 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -43,10 +43,10 @@ use rustc::hir::print as pprust;
 use rustc::ty::subst::Substs;
 use rustc::ty;
 use rustc::middle::stability;
+use rustc::util::nodemap::{FnvHashMap, FnvHashSet};
 
 use rustc::hir;
 
-use std::collections::{HashMap, HashSet};
 use std::path::PathBuf;
 use std::rc::Rc;
 use std::sync::Arc;
@@ -121,7 +121,7 @@ pub struct Crate {
     pub access_levels: Arc<AccessLevels<DefId>>,
     // These are later on moved into `CACHEKEY`, leaving the map empty.
     // Only here so that they can be filtered through the rustdoc passes.
-    pub external_traits: HashMap<DefId, Trait>,
+    pub external_traits: FnvHashMap<DefId, Trait>,
 }
 
 struct CrateNum(ast::CrateNum);
@@ -1010,7 +1010,7 @@ impl<'a, 'tcx> Clean<Generics> for (&'a ty::Generics<'tcx>,
         // Note that associated types also have a sized bound by default, but we
         // don't actually know the set of associated types right here so that's
         // handled in cleaning associated types
-        let mut sized_params = HashSet::new();
+        let mut sized_params = FnvHashSet();
         where_predicates.retain(|pred| {
             match *pred {
                 WP::BoundPredicate { ty: Generic(ref g), ref bounds } => {
@@ -1656,9 +1656,9 @@ impl From<ast::FloatTy> for PrimitiveType {
 struct SubstAlias<'a, 'tcx: 'a> {
     tcx: &'a ty::TyCtxt<'a, 'tcx, 'tcx>,
     // Table type parameter definition -> substituted type
-    ty_substs: HashMap<Def, hir::Ty>,
+    ty_substs: FnvHashMap<Def, hir::Ty>,
     // Table node id of lifetime parameter definition -> substituted lifetime
-    lt_substs: HashMap<ast::NodeId, hir::Lifetime>,
+    lt_substs: FnvHashMap<ast::NodeId, hir::Lifetime>,
 }
 
 impl<'a, 'tcx: 'a, 'b: 'tcx> Folder for SubstAlias<'a, 'tcx> {
@@ -1727,8 +1727,8 @@ impl Clean<Type> for hir::Ty {
                                 let item = tcx.map.expect_item(node_id);
                                 if let hir::ItemTy(ref ty, ref generics) = item.node {
                                     let provided_params = &path.segments.last().unwrap().parameters;
-                                    let mut ty_substs = HashMap::new();
-                                    let mut lt_substs = HashMap::new();
+                                    let mut ty_substs = FnvHashMap();
+                                    let mut lt_substs = FnvHashMap();
                                     for (i, ty_param) in generics.ty_params.iter().enumerate() {
                                         let ty_param_def = tcx.expect_def(ty_param.id);
                                         if let Some(ty) = provided_params.types().get(i).cloned()
@@ -2384,7 +2384,7 @@ impl Clean<ImplPolarity> for hir::ImplPolarity {
 pub struct Impl {
     pub unsafety: hir::Unsafety,
     pub generics: Generics,
-    pub provided_trait_methods: HashSet<String>,
+    pub provided_trait_methods: FnvHashSet<String>,
     pub trait_: Option<Type>,
     pub for_: Type,
     pub items: Vec<Item>,
@@ -2410,7 +2410,7 @@ impl Clean<Vec<Item>> for doctree::Impl {
                    .map(|meth| meth.name.to_string())
                    .collect()
             })
-        }).unwrap_or(HashSet::new());
+        }).unwrap_or(FnvHashSet());
 
         ret.push(Item {
             name: None,
diff --git a/src/librustdoc/core.rs b/src/librustdoc/core.rs
index 8032b5c3104..26f792a1fdf 100644
--- a/src/librustdoc/core.rs
+++ b/src/librustdoc/core.rs
@@ -18,6 +18,7 @@ use rustc::middle::privacy::AccessLevels;
 use rustc::ty::{self, TyCtxt};
 use rustc::hir::map as hir_map;
 use rustc::lint;
+use rustc::util::nodemap::{FnvHashMap, FnvHashSet};
 use rustc_trans::back::link;
 use rustc_resolve as resolve;
 use rustc_metadata::cstore::CStore;
@@ -28,7 +29,6 @@ use errors;
 use errors::emitter::ColorConfig;
 
 use std::cell::{RefCell, Cell};
-use std::collections::{HashMap, HashSet};
 use std::rc::Rc;
 
 use visit_ast::RustdocVisitor;
@@ -45,13 +45,13 @@ pub enum MaybeTyped<'a, 'tcx: 'a> {
     NotTyped(&'a session::Session)
 }
 
-pub type ExternalPaths = HashMap<DefId, (Vec<String>, clean::TypeKind)>;
+pub type ExternalPaths = FnvHashMap<DefId, (Vec<String>, clean::TypeKind)>;
 
 pub struct DocContext<'a, 'tcx: 'a> {
     pub map: &'a hir_map::Map<'tcx>,
     pub maybe_typed: MaybeTyped<'a, 'tcx>,
     pub input: Input,
-    pub populated_crate_impls: RefCell<HashSet<ast::CrateNum>>,
+    pub populated_crate_impls: RefCell<FnvHashSet<ast::CrateNum>>,
     pub deref_trait_did: Cell<Option<DefId>>,
     // Note that external items for which `doc(hidden)` applies to are shown as
     // non-reachable while local items aren't. This is because we're reusing
@@ -61,7 +61,7 @@ pub struct DocContext<'a, 'tcx: 'a> {
     /// Later on moved into `html::render::CACHE_KEY`
     pub renderinfo: RefCell<RenderInfo>,
     /// Later on moved through `clean::Crate` into `html::render::CACHE_KEY`
-    pub external_traits: RefCell<HashMap<DefId, clean::Trait>>,
+    pub external_traits: RefCell<FnvHashMap<DefId, clean::Trait>>,
 }
 
 impl<'b, 'tcx> DocContext<'b, 'tcx> {
@@ -178,10 +178,10 @@ pub fn run_core(search_paths: SearchPaths,
             map: &tcx.map,
             maybe_typed: Typed(tcx),
             input: input,
-            populated_crate_impls: RefCell::new(HashSet::new()),
+            populated_crate_impls: RefCell::new(FnvHashSet()),
             deref_trait_did: Cell::new(None),
             access_levels: RefCell::new(access_levels),
-            external_traits: RefCell::new(HashMap::new()),
+            external_traits: RefCell::new(FnvHashMap()),
             renderinfo: RefCell::new(Default::default()),
         };
         debug!("crate: {:?}", ctxt.map.krate());
diff --git a/src/librustdoc/html/render.rs b/src/librustdoc/html/render.rs
index 6993f85c3d9..5cb5cc05187 100644
--- a/src/librustdoc/html/render.rs
+++ b/src/librustdoc/html/render.rs
@@ -37,7 +37,7 @@ pub use self::ExternalLocation::*;
 use std::ascii::AsciiExt;
 use std::cell::RefCell;
 use std::cmp::Ordering;
-use std::collections::{BTreeMap, HashMap, HashSet};
+use std::collections::BTreeMap;
 use std::default::Default;
 use std::error;
 use std::fmt::{self, Display, Formatter};
@@ -61,6 +61,7 @@ use rustc::middle::privacy::AccessLevels;
 use rustc::middle::stability;
 use rustc::session::config::get_unstable_features_setting;
 use rustc::hir;
+use rustc::util::nodemap::{FnvHashMap, FnvHashSet};
 
 use clean::{self, Attributes, GetDefId};
 use doctree;
@@ -114,9 +115,9 @@ pub struct SharedContext {
     /// `true`.
     pub include_sources: bool,
     /// The local file sources we've emitted and their respective url-paths.
-    pub local_sources: HashMap<PathBuf, String>,
+    pub local_sources: FnvHashMap<PathBuf, String>,
     /// All the passes that were run on this crate.
-    pub passes: HashSet<String>,
+    pub passes: FnvHashSet<String>,
     /// The base-URL of the issue tracker for when an item has been tagged with
     /// an issue number.
     pub issue_tracker_base_url: Option<String>,
@@ -211,7 +212,7 @@ pub struct Cache {
     /// Mapping of typaram ids to the name of the type parameter. This is used
     /// when pretty-printing a type (so pretty printing doesn't have to
     /// painfully maintain a context like this)
-    pub typarams: HashMap<DefId, String>,
+    pub typarams: FnvHashMap<DefId, String>,
 
     /// Maps a type id to all known implementations for that type. This is only
     /// recognized for intra-crate `ResolvedPath` types, and is used to print
@@ -219,35 +220,35 @@ pub struct Cache {
     ///
     /// The values of the map are a list of implementations and documentation
     /// found on that implementation.
-    pub impls: HashMap<DefId, Vec<Impl>>,
+    pub impls: FnvHashMap<DefId, Vec<Impl>>,
 
     /// Maintains a mapping of local crate node ids to the fully qualified name
     /// and "short type description" of that node. This is used when generating
     /// URLs when a type is being linked to. External paths are not located in
     /// this map because the `External` type itself has all the information
     /// necessary.
-    pub paths: HashMap<DefId, (Vec<String>, ItemType)>,
+    pub paths: FnvHashMap<DefId, (Vec<String>, ItemType)>,
 
     /// Similar to `paths`, but only holds external paths. This is only used for
     /// generating explicit hyperlinks to other crates.
-    pub external_paths: HashMap<DefId, (Vec<String>, ItemType)>,
+    pub external_paths: FnvHashMap<DefId, (Vec<String>, ItemType)>,
 
     /// This map contains information about all known traits of this crate.
     /// Implementations of a crate should inherit the documentation of the
     /// parent trait if no extra documentation is specified, and default methods
     /// should show up in documentation about trait implementations.
-    pub traits: HashMap<DefId, clean::Trait>,
+    pub traits: FnvHashMap<DefId, clean::Trait>,
 
     /// When rendering traits, it's often useful to be able to list all
     /// implementors of the trait, and this mapping is exactly, that: a mapping
     /// of trait ids to the list of known implementors of the trait
-    pub implementors: HashMap<DefId, Vec<Implementor>>,
+    pub implementors: FnvHashMap<DefId, Vec<Implementor>>,
 
     /// Cache of where external crate documentation can be found.
-    pub extern_locations: HashMap<ast::CrateNum, (String, ExternalLocation)>,
+    pub extern_locations: FnvHashMap<ast::CrateNum, (String, ExternalLocation)>,
 
     /// Cache of where documentation for primitives can be found.
-    pub primitive_locations: HashMap<clean::PrimitiveType, ast::CrateNum>,
+    pub primitive_locations: FnvHashMap<clean::PrimitiveType, ast::CrateNum>,
 
     // Note that external items for which `doc(hidden)` applies to are shown as
     // non-reachable while local items aren't. This is because we're reusing
@@ -260,7 +261,7 @@ pub struct Cache {
     parent_stack: Vec<DefId>,
     parent_is_trait_impl: bool,
     search_index: Vec<IndexItem>,
-    seen_modules: HashSet<DefId>,
+    seen_modules: FnvHashSet<DefId>,
     seen_mod: bool,
     stripped_mod: bool,
     deref_trait_did: Option<DefId>,
@@ -277,9 +278,9 @@ pub struct Cache {
 /// Later on moved into `CACHE_KEY`.
 #[derive(Default)]
 pub struct RenderInfo {
-    pub inlined: HashSet<DefId>,
+    pub inlined: FnvHashSet<DefId>,
     pub external_paths: ::core::ExternalPaths,
-    pub external_typarams: HashMap<DefId, String>,
+    pub external_typarams: FnvHashMap<DefId, String>,
     pub deref_trait_did: Option<DefId>,
 }
 
@@ -377,10 +378,10 @@ impl ToJson for IndexItemFunctionType {
 thread_local!(static CACHE_KEY: RefCell<Arc<Cache>> = Default::default());
 thread_local!(pub static CURRENT_LOCATION_KEY: RefCell<Vec<String>> =
                     RefCell::new(Vec::new()));
-thread_local!(static USED_ID_MAP: RefCell<HashMap<String, usize>> =
+thread_local!(static USED_ID_MAP: RefCell<FnvHashMap<String, usize>> =
                     RefCell::new(init_ids()));
 
-fn init_ids() -> HashMap<String, usize> {
+fn init_ids() -> FnvHashMap<String, usize> {
     [
      "main",
      "search",
@@ -407,7 +408,7 @@ pub fn reset_ids(embedded: bool) {
         *s.borrow_mut() = if embedded {
             init_ids()
         } else {
-            HashMap::new()
+            FnvHashMap()
         };
     });
 }
@@ -432,7 +433,7 @@ pub fn derive_id(candidate: String) -> String {
 pub fn run(mut krate: clean::Crate,
            external_html: &ExternalHtml,
            dst: PathBuf,
-           passes: HashSet<String>,
+           passes: FnvHashSet<String>,
            css_file_extension: Option<PathBuf>,
            renderinfo: RenderInfo) -> Result<(), Error> {
     let src_root = match krate.src.parent() {
@@ -443,7 +444,7 @@ pub fn run(mut krate: clean::Crate,
         src_root: src_root,
         passes: passes,
         include_sources: true,
-        local_sources: HashMap::new(),
+        local_sources: FnvHashMap(),
         issue_tracker_base_url: None,
         layout: layout::Layout {
             logo: "".to_string(),
@@ -513,22 +514,22 @@ pub fn run(mut krate: clean::Crate,
         .collect();
 
     let mut cache = Cache {
-        impls: HashMap::new(),
+        impls: FnvHashMap(),
         external_paths: external_paths,
-        paths: HashMap::new(),
-        implementors: HashMap::new(),
+        paths: FnvHashMap(),
+        implementors: FnvHashMap(),
         stack: Vec::new(),
         parent_stack: Vec::new(),
         search_index: Vec::new(),
         parent_is_trait_impl: false,
-        extern_locations: HashMap::new(),
-        primitive_locations: HashMap::new(),
-        seen_modules: HashSet::new(),
+        extern_locations: FnvHashMap(),
+        primitive_locations: FnvHashMap(),
+        seen_modules: FnvHashSet(),
         seen_mod: false,
         stripped_mod: false,
         access_levels: krate.access_levels.clone(),
         orphan_methods: Vec::new(),
-        traits: mem::replace(&mut krate.external_traits, HashMap::new()),
+        traits: mem::replace(&mut krate.external_traits, FnvHashMap()),
         deref_trait_did: deref_trait_did,
         typarams: external_typarams,
     };
@@ -574,7 +575,7 @@ pub fn run(mut krate: clean::Crate,
 
 /// Build the search index from the collected metadata
 fn build_index(krate: &clean::Crate, cache: &mut Cache) -> String {
-    let mut nodeid_to_pathid = HashMap::new();
+    let mut nodeid_to_pathid = FnvHashMap();
     let mut crate_items = Vec::with_capacity(cache.search_index.len());
     let mut crate_paths = Vec::<Json>::new();
 
@@ -2515,7 +2516,7 @@ fn render_struct(w: &mut fmt::Formatter, it: &clean::Item,
 #[derive(Copy, Clone)]
 enum AssocItemLink<'a> {
     Anchor(Option<&'a str>),
-    GotoSource(DefId, &'a HashSet<String>),
+    GotoSource(DefId, &'a FnvHashSet<String>),
 }
 
 impl<'a> AssocItemLink<'a> {
diff --git a/src/librustdoc/test.rs b/src/librustdoc/test.rs
index 7d1dbbe5dc0..e7edf8d1cab 100644
--- a/src/librustdoc/test.rs
+++ b/src/librustdoc/test.rs
@@ -9,7 +9,6 @@
 // except according to those terms.
 
 use std::cell::{RefCell, Cell};
-use std::collections::{HashMap, HashSet};
 use std::env;
 use std::ffi::OsString;
 use std::io::prelude::*;
@@ -29,6 +28,7 @@ use rustc::session::{self, config};
 use rustc::session::config::{get_unstable_features_setting, OutputType,
                              OutputTypes, Externs};
 use rustc::session::search_paths::{SearchPaths, PathKind};
+use rustc::util::nodemap::{FnvHashMap, FnvHashSet};
 use rustc_back::dynamic_lib::DynamicLibrary;
 use rustc_back::tempdir::TempDir;
 use rustc_driver::{driver, Compilation};
@@ -107,8 +107,8 @@ pub fn run(input: &str,
         map: &map,
         maybe_typed: core::NotTyped(&sess),
         input: input,
-        external_traits: RefCell::new(HashMap::new()),
-        populated_crate_impls: RefCell::new(HashSet::new()),
+        external_traits: RefCell::new(FnvHashMap()),
+        populated_crate_impls: RefCell::new(FnvHashSet()),
         deref_trait_did: Cell::new(None),
         access_levels: Default::default(),
         renderinfo: Default::default(),
diff --git a/src/librustdoc/visit_ast.rs b/src/librustdoc/visit_ast.rs
index 0334c5ef5c4..f6084180f0b 100644
--- a/src/librustdoc/visit_ast.rs
+++ b/src/librustdoc/visit_ast.rs
@@ -11,7 +11,6 @@
 //! Rust AST Visitor. Extracts useful information and massages it into a form
 //! usable for clean
 
-use std::collections::HashSet;
 use std::mem;
 
 use syntax::abi;
@@ -23,6 +22,7 @@ use syntax_pos::Span;
 use rustc::hir::map as hir_map;
 use rustc::hir::def::Def;
 use rustc::middle::privacy::AccessLevel;
+use rustc::util::nodemap::FnvHashSet;
 
 use rustc::hir;
 
@@ -42,14 +42,14 @@ pub struct RustdocVisitor<'a, 'tcx: 'a> {
     pub module: Module,
     pub attrs: hir::HirVec<ast::Attribute>,
     pub cx: &'a core::DocContext<'a, 'tcx>,
-    view_item_stack: HashSet<ast::NodeId>,
+    view_item_stack: FnvHashSet<ast::NodeId>,
     inlining_from_glob: bool,
 }
 
 impl<'a, 'tcx> RustdocVisitor<'a, 'tcx> {
     pub fn new(cx: &'a core::DocContext<'a, 'tcx>) -> RustdocVisitor<'a, 'tcx> {
         // If the root is reexported, terminate all recursion.
-        let mut stack = HashSet::new();
+        let mut stack = FnvHashSet();
         stack.insert(ast::CRATE_NODE_ID);
         RustdocVisitor {
             module: Module::new(None),