Use FxHash{Map,Set} instead of the default Hash{Map,Set} everywhere in rustc.

src/librustc/hir/lowering.rs

@@ -50,6 +50,7 @@ use hir::GenericArg;
 use lint::builtin::{self, PARENTHESIZED_PARAMS_IN_TYPES_AND_MODULES,
                     ELIDED_LIFETIMES_IN_PATHS};
 use middle::cstore::CrateStore;
+use rustc_data_structures::fx::FxHashSet;
 use rustc_data_structures::indexed_vec::IndexVec;
 use rustc_data_structures::small_vec::OneVector;
 use rustc_data_structures::thin_vec::ThinVec;
@@ -57,7 +58,7 @@ use session::Session;
 use util::common::FN_OUTPUT_NAME;
 use util::nodemap::{DefIdMap, NodeMap};
 
-use std::collections::{BTreeMap, HashSet};
+use std::collections::BTreeMap;
 use std::fmt::Debug;
 use std::iter;
 use std::mem;
@@ -1342,7 +1343,7 @@ impl<'a> LoweringContext<'a> {
             exist_ty_id: NodeId,
             collect_elided_lifetimes: bool,
             currently_bound_lifetimes: Vec<hir::LifetimeName>,
-            already_defined_lifetimes: HashSet<hir::LifetimeName>,
+            already_defined_lifetimes: FxHashSet<hir::LifetimeName>,
             output_lifetimes: Vec<hir::GenericArg>,
             output_lifetime_params: Vec<hir::GenericParam>,
         }
@@ -1476,7 +1477,7 @@ impl<'a> LoweringContext<'a> {
             exist_ty_id,
             collect_elided_lifetimes: true,
             currently_bound_lifetimes: Vec::new(),
-            already_defined_lifetimes: HashSet::new(),
+            already_defined_lifetimes: FxHashSet::default(),
             output_lifetimes: Vec::new(),
             output_lifetime_params: Vec::new(),
         };

src/librustc/middle/weak_lang_items.rs

@@ -13,6 +13,7 @@
 use session::config;
 use middle::lang_items;
 
+use rustc_data_structures::fx::FxHashSet;
 use rustc_target::spec::PanicStrategy;
 use syntax::ast;
 use syntax::symbol::Symbol;
@@ -23,8 +24,6 @@ use hir::intravisit;
 use hir;
 use ty::TyCtxt;
 
-use std::collections::HashSet;
-
 macro_rules! weak_lang_items {
     ($($name:ident, $item:ident, $sym:ident;)*) => (
 
@@ -101,7 +100,7 @@ fn verify<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
         return
     }
 
-    let mut missing = HashSet::new();
+    let mut missing = FxHashSet::default();
     for &cnum in tcx.crates().iter() {
         for &item in tcx.missing_lang_items(cnum).iter() {
             missing.insert(item);

src/librustc/session/config.rs

@@ -37,10 +37,10 @@ use std::collections::btree_map::Iter as BTreeMapIter;
 use std::collections::btree_map::Keys as BTreeMapKeysIter;
 use std::collections::btree_map::Values as BTreeMapValuesIter;
 
+use rustc_data_structures::fx::FxHashSet;
 use std::{fmt, str};
 use std::hash::Hasher;
 use std::collections::hash_map::DefaultHasher;
-use std::collections::HashSet;
 use std::iter::FromIterator;
 use std::path::{Path, PathBuf};
 
@@ -1373,7 +1373,7 @@ pub fn default_configuration(sess: &Session) -> ast::CrateConfig {
     let max_atomic_width = sess.target.target.max_atomic_width();
     let atomic_cas = sess.target.target.options.atomic_cas;
 
-    let mut ret = HashSet::new();
+    let mut ret = FxHashSet::default();
     // Target bindings.
     ret.insert((Symbol::intern("target_os"), Some(Symbol::intern(os))));
     if let Some(ref fam) = sess.target.target.options.target_family {

src/librustc/session/filesearch.rs

@@ -12,8 +12,8 @@
 
 pub use self::FileMatch::*;
 
+use rustc_data_structures::fx::FxHashSet;
 use std::borrow::Cow;
-use std::collections::HashSet;
 use std::env;
 use std::fs;
 use std::path::{Path, PathBuf};
@@ -40,7 +40,7 @@ impl<'a> FileSearch<'a> {
     pub fn for_each_lib_search_path<F>(&self, mut f: F) where
         F: FnMut(&Path, PathKind)
     {
-        let mut visited_dirs = HashSet::new();
+        let mut visited_dirs = FxHashSet::default();
 
         for (path, kind) in self.search_paths.iter(self.kind) {
             f(path, kind);

src/librustc/session/mod.rs

@@ -47,7 +47,6 @@ use jobserver::Client;
 
 use std;
 use std::cell::{self, Cell, RefCell};
-use std::collections::HashMap;
 use std::env;
 use std::fmt;
 use std::io::Write;
@@ -122,7 +121,7 @@ pub struct Session {
     /// Map from imported macro spans (which consist of
     /// the localized span for the macro body) to the
     /// macro name and definition span in the source crate.
-    pub imported_macro_spans: OneThread<RefCell<HashMap<Span, (String, Span)>>>,
+    pub imported_macro_spans: OneThread<RefCell<FxHashMap<Span, (String, Span)>>>,
 
     incr_comp_session: OneThread<RefCell<IncrCompSession>>,
 
@@ -1129,7 +1128,7 @@ pub fn build_session_(
         injected_allocator: Once::new(),
         allocator_kind: Once::new(),
         injected_panic_runtime: Once::new(),
-        imported_macro_spans: OneThread::new(RefCell::new(HashMap::new())),
+        imported_macro_spans: OneThread::new(RefCell::new(FxHashMap::default())),
         incr_comp_session: OneThread::new(RefCell::new(IncrCompSession::NotInitialized)),
         self_profiling: Lock::new(SelfProfiler::new()),
         profile_channel: Lock::new(None),

src/librustc/ty/query/job.rs

@@ -11,6 +11,7 @@
 #![allow(warnings)]
 
 use std::mem;
+use rustc_data_structures::fx::FxHashSet;
 use rustc_data_structures::sync::{Lock, LockGuard, Lrc, Weak};
 use rustc_data_structures::OnDrop;
 use syntax_pos::Span;
@@ -21,7 +22,7 @@ use ty::context::TyCtxt;
 use errors::Diagnostic;
 use std::process;
 use std::{fmt, ptr};
-use std::collections::HashSet;
+
 #[cfg(parallel_queries)]
 use {
     rayon_core,
@@ -282,7 +283,7 @@ where
 fn cycle_check<'tcx>(query: Lrc<QueryJob<'tcx>>,
                      span: Span,
                      stack: &mut Vec<(Span, Lrc<QueryJob<'tcx>>)>,
-                     visited: &mut HashSet<*const QueryJob<'tcx>>
+                     visited: &mut FxHashSet<*const QueryJob<'tcx>>
 ) -> Option<Option<Waiter<'tcx>>> {
     if visited.contains(&query.as_ptr()) {
         return if let Some(p) = stack.iter().position(|q| q.1.as_ptr() == query.as_ptr()) {
@@ -321,7 +322,7 @@ fn cycle_check<'tcx>(query: Lrc<QueryJob<'tcx>>,
 #[cfg(parallel_queries)]
 fn connected_to_root<'tcx>(
     query: Lrc<QueryJob<'tcx>>,
-    visited: &mut HashSet<*const QueryJob<'tcx>>
+    visited: &mut FxHashSet<*const QueryJob<'tcx>>
 ) -> bool {
     // We already visited this or we're deliberately ignoring it
     if visited.contains(&query.as_ptr()) {
@@ -357,7 +358,7 @@ fn remove_cycle<'tcx>(
     wakelist: &mut Vec<Lrc<QueryWaiter<'tcx>>>,
     tcx: TyCtxt<'_, 'tcx, '_>
 ) -> bool {
-    let mut visited = HashSet::new();
+    let mut visited = FxHashSet::default();
     let mut stack = Vec::new();
     // Look for a cycle starting with the last query in `jobs`
     if let Some(waiter) = cycle_check(jobs.pop().unwrap(),
@@ -389,7 +390,7 @@ fn remove_cycle<'tcx>(
         // connected to queries outside the cycle
         let entry_points: Vec<Lrc<QueryJob<'tcx>>> = stack.iter().filter_map(|query| {
             // Mark all the other queries in the cycle as already visited
-            let mut visited = HashSet::from_iter(stack.iter().filter_map(|q| {
+            let mut visited = FxHashSet::from_iter(stack.iter().filter_map(|q| {
                 if q.1.as_ptr() != query.1.as_ptr() {
                     Some(q.1.as_ptr())
                 } else {

src/librustc/util/time_graph.rs

@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use std::collections::HashMap;
+use rustc_data_structures::fx::FxHashMap;
 use std::fs::File;
 use std::io::prelude::*;
 use std::marker::PhantomData;
@@ -40,7 +40,7 @@ struct PerThread {
 
 #[derive(Clone)]
 pub struct TimeGraph {
-    data: Arc<Mutex<HashMap<TimelineId, PerThread>>>,
+    data: Arc<Mutex<FxHashMap<TimelineId, PerThread>>>,
 }
 
 #[derive(Clone, Copy)]
@@ -68,7 +68,7 @@ impl Drop for RaiiToken {
 impl TimeGraph {
     pub fn new() -> TimeGraph {
         TimeGraph {
-            data: Arc::new(Mutex::new(HashMap::new()))
+            data: Arc::new(Mutex::new(FxHashMap::default()))
         }
     }
 

src/librustc_codegen_llvm/back/linker.rs

@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use std::collections::HashMap;
+use rustc_data_structures::fx::FxHashMap;
 use std::ffi::{OsStr, OsString};
 use std::fs::{self, File};
 use std::io::prelude::*;
@@ -30,7 +30,7 @@ use serialize::{json, Encoder};
 /// For all the linkers we support, and information they might
 /// need out of the shared crate context before we get rid of it.
 pub struct LinkerInfo {
-    exports: HashMap<CrateType, Vec<String>>,
+    exports: FxHashMap<CrateType, Vec<String>>,
 }
 
 impl LinkerInfo {

src/librustc_codegen_llvm/back/rpath.rs

@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use std::collections::HashSet;
+use rustc_data_structures::fx::FxHashSet;
 use std::env;
 use std::path::{Path, PathBuf};
 use std::fs;
@@ -172,7 +172,7 @@ fn get_install_prefix_rpath(config: &mut RPathConfig) -> String {
 }
 
 fn minimize_rpaths(rpaths: &[String]) -> Vec<String> {
-    let mut set = HashSet::new();
+    let mut set = FxHashSet::default();
     let mut minimized = Vec::new();
     for rpath in rpaths {
         if set.insert(rpath) {

src/librustc_data_structures/graph/test.rs

@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use std::collections::HashMap;
+use fx::FxHashMap;
 use std::cmp::max;
 use std::slice;
 use std::iter;
@@ -18,8 +18,8 @@ use super::*;
 pub struct TestGraph {
     num_nodes: usize,
     start_node: usize,
-    successors: HashMap<usize, Vec<usize>>,
+    successors: FxHashMap<usize, Vec<usize>>,
-    predecessors: HashMap<usize, Vec<usize>>,
+    predecessors: FxHashMap<usize, Vec<usize>>,
 }
 
 impl TestGraph {
@@ -27,8 +27,8 @@ impl TestGraph {
         let mut graph = TestGraph {
             num_nodes: start_node + 1,
             start_node,
-            successors: HashMap::new(),
+            successors: FxHashMap::default(),
-            predecessors: HashMap::new(),
+            predecessors: FxHashMap::default(),
         };
         for &(source, target) in edges {
             graph.num_nodes = max(graph.num_nodes, source + 1);

src/librustc_driver/profile/trace.rs

@@ -10,10 +10,10 @@
 
 use super::*;
 use syntax_pos::SpanData;
+use rustc_data_structures::fx::FxHashMap;
 use rustc::util::common::QueryMsg;
 use std::fs::File;
 use std::time::{Duration, Instant};
-use std::collections::hash_map::HashMap;
 use rustc::dep_graph::{DepNode};
 
 #[derive(Debug, Clone, Eq, PartialEq)]
@@ -149,7 +149,7 @@ fn write_traces_rec(file: &mut File, traces: &[Rec], total: Duration, depth: usi
     }
 }
 
-fn compute_counts_rec(counts: &mut HashMap<String,QueryMetric>, traces: &[Rec]) {
+fn compute_counts_rec(counts: &mut FxHashMap<String,QueryMetric>, traces: &[Rec]) {
     for t in traces.iter() {
         match t.effect {
             Effect::TimeBegin(ref msg) => {
@@ -200,7 +200,7 @@ fn compute_counts_rec(counts: &mut HashMap<String,QueryMetric>, traces: &[Rec])
     }
 }
 
-pub fn write_counts(count_file: &mut File, counts: &mut HashMap<String,QueryMetric>) {
+pub fn write_counts(count_file: &mut File, counts: &mut FxHashMap<String,QueryMetric>) {
     use rustc::util::common::duration_to_secs_str;
     use std::cmp::Reverse;
 
@@ -219,7 +219,7 @@ pub fn write_counts(count_file: &mut File, counts: &mut HashMap<String,QueryMetr
 
 pub fn write_traces(html_file: &mut File, counts_file: &mut File, traces: &[Rec]) {
     let capacity = traces.iter().fold(0, |acc, t| acc + 1 + t.extent.len());
-    let mut counts : HashMap<String, QueryMetric> = HashMap::with_capacity(capacity);
+    let mut counts = FxHashMap::with_capacity_and_hasher(capacity, Default::default());
     compute_counts_rec(&mut counts, traces);
     write_counts(counts_file, &mut counts);
 

src/librustc_errors/emitter.rs

@@ -16,12 +16,12 @@ use {Level, CodeSuggestion, DiagnosticBuilder, SubDiagnostic, SourceMapperDyn, D
 use snippet::{Annotation, AnnotationType, Line, MultilineAnnotation, StyledString, Style};
 use styled_buffer::StyledBuffer;
 
+use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sync::Lrc;
 use atty;
 use std::borrow::Cow;
 use std::io::prelude::*;
 use std::io;
-use std::collections::HashMap;
 use std::cmp::{min, Reverse};
 use termcolor::{StandardStream, ColorChoice, ColorSpec, BufferWriter};
 use termcolor::{WriteColor, Color, Buffer};
@@ -1090,7 +1090,7 @@ impl EmitterWriter {
                                             max_line_num_len + 1);
 
                 // Contains the vertical lines' positions for active multiline annotations
-                let mut multilines = HashMap::new();
+                let mut multilines = FxHashMap::default();
 
                 // Next, output the annotate source for this file
                 for line_idx in 0..annotated_file.lines.len() {
@@ -1109,7 +1109,7 @@ impl EmitterWriter {
                                                          width_offset,
                                                          code_offset);
 
-                    let mut to_add = HashMap::new();
+                    let mut to_add = FxHashMap::default();
 
                     for (depth, style) in depths {
                         if multilines.get(&depth).is_some() {

src/librustc_errors/registry.rs

@@ -8,11 +8,11 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use std::collections::HashMap;
+use rustc_data_structures::fx::FxHashMap;
 
 #[derive(Clone)]
 pub struct Registry {
-    descriptions: HashMap<&'static str, &'static str>,
+    descriptions: FxHashMap<&'static str, &'static str>,
 }
 
 impl Registry {

src/librustc_incremental/persist/dirty_clean.rs

@@ -24,7 +24,6 @@
 //! the required condition is not met.
 //!
 
-use std::collections::HashSet;
 use std::iter::FromIterator;
 use std::vec::Vec;
 use rustc::dep_graph::{DepNode, label_strs};
@@ -193,7 +192,7 @@ const LABELS_TRAIT: &[&[&str]] = &[
 //
 //     TypeOfItem for these.
 
-type Labels = HashSet<String>;
+type Labels = FxHashSet<String>;
 
 /// Represents the requested configuration by rustc_clean/dirty
 struct Assertion {
@@ -205,13 +204,13 @@ impl Assertion {
     fn from_clean_labels(labels: Labels) -> Assertion {
         Assertion {
             clean: labels,
-            dirty: Labels::new(),
+            dirty: Labels::default(),
         }
     }
 
     fn from_dirty_labels(labels: Labels) -> Assertion {
         Assertion {
-            clean: Labels::new(),
+            clean: Labels::default(),
             dirty: labels,
         }
     }
@@ -328,7 +327,7 @@ impl<'a, 'tcx> DirtyCleanVisitor<'a, 'tcx> {
             }
         }
         // if no `label` or `except` is given, only the node's group are asserted
-        Labels::new()
+        Labels::default()
     }
 
     /// Return all DepNode labels that should be asserted for this item.
@@ -436,7 +435,7 @@ impl<'a, 'tcx> DirtyCleanVisitor<'a, 'tcx> {
     }
 
     fn resolve_labels(&self, item: &NestedMetaItem, value: &str) -> Labels {
-        let mut out: Labels = HashSet::new();
+        let mut out = Labels::default();
         for label in value.split(',') {
             let label = label.trim();
             if DepNode::has_label_string(label) {

src/librustc_lint/builtin.rs

@@ -39,7 +39,6 @@ use util::nodemap::NodeSet;
 use lint::{LateContext, LintContext, LintArray};
 use lint::{LintPass, LateLintPass, EarlyLintPass, EarlyContext};
 
-use std::collections::HashSet;
 use rustc::util::nodemap::FxHashSet;
 
 use syntax::tokenstream::{TokenTree, TokenStream};
@@ -304,14 +303,14 @@ pub struct MissingDoc {
     doc_hidden_stack: Vec<bool>,
 
     /// Private traits or trait items that leaked through. Don't check their methods.
-    private_traits: HashSet<ast::NodeId>,
+    private_traits: FxHashSet<ast::NodeId>,
 }
 
 impl MissingDoc {
     pub fn new() -> MissingDoc {
         MissingDoc {
             doc_hidden_stack: vec![false],
-            private_traits: HashSet::new(),
+            private_traits: FxHashSet::default(),
         }
     }
 
@@ -908,7 +907,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnconditionalRecursion {
         let mut work_queue = vec![cfg.entry];
         let mut reached_exit_without_self_call = false;
         let mut self_call_spans = vec![];
-        let mut visited = HashSet::new();
+        let mut visited = FxHashSet::default();
 
         while let Some(idx) = work_queue.pop() {
             if idx == cfg.exit {

src/librustc_metadata/locator.rs

@@ -226,6 +226,7 @@ use cstore::{MetadataRef, MetadataBlob};
 use creader::Library;
 use schema::{METADATA_HEADER, rustc_version};
 
+use rustc_data_structures::fx::FxHashSet;
 use rustc_data_structures::svh::Svh;
 use rustc::middle::cstore::MetadataLoader;
 use rustc::session::{config, Session};
@@ -239,7 +240,6 @@ use syntax_pos::Span;
 use rustc_target::spec::{Target, TargetTriple};
 
 use std::cmp;
-use std::collections::HashSet;
 use std::fmt;
 use std::fs;
 use std::io::{self, Read};
@@ -308,7 +308,7 @@ impl CratePaths {
 
 impl<'a> Context<'a> {
     pub fn maybe_load_library_crate(&mut self) -> Option<Library> {
-        let mut seen_paths = HashSet::new();
+        let mut seen_paths = FxHashSet::default();
         match self.extra_filename {
             Some(s) => self.find_library_crate(s, &mut seen_paths)
                 .or_else(|| self.find_library_crate("", &mut seen_paths)),
@@ -431,7 +431,7 @@ impl<'a> Context<'a> {
 
     fn find_library_crate(&mut self,
                           extra_prefix: &str,
-                          seen_paths: &mut HashSet<PathBuf>)
+                          seen_paths: &mut FxHashSet<PathBuf>)
                           -> Option<Library> {
         // If an SVH is specified, then this is a transitive dependency that
         // must be loaded via -L plus some filtering.

src/librustc_mir/transform/generator.rs

@@ -67,9 +67,9 @@ use rustc::ty::{self, TyCtxt, AdtDef, Ty};
 use rustc::ty::subst::Substs;
 use util::dump_mir;
 use util::liveness::{self, IdentityMap};
+use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::indexed_vec::Idx;
 use rustc_data_structures::indexed_set::IdxSet;
-use std::collections::HashMap;
 use std::borrow::Cow;
 use std::iter::once;
 use std::mem;
@@ -142,10 +142,12 @@ struct TransformVisitor<'a, 'tcx: 'a> {
     state_field: usize,
 
     // Mapping from Local to (type of local, generator struct index)
-    remap: HashMap<Local, (Ty<'tcx>, usize)>,
+    // FIXME(eddyb) This should use `IndexVec<Local, Option<_>>`.
+    remap: FxHashMap<Local, (Ty<'tcx>, usize)>,
 
     // A map from a suspension point in a block to the locals which have live storage at that point
-    storage_liveness: HashMap<BasicBlock, liveness::LiveVarSet<Local>>,
+    // FIXME(eddyb) This should use `IndexVec<BasicBlock, Option<_>>`.
+    storage_liveness: FxHashMap<BasicBlock, liveness::LiveVarSet<Local>>,
 
     // A list of suspension points, generated during the transform
     suspension_points: Vec<SuspensionPoint>,
@@ -364,12 +366,15 @@ impl<'tcx> Visitor<'tcx> for BorrowedLocals {
     }
 }
 
-fn locals_live_across_suspend_points<'a, 'tcx,>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
+fn locals_live_across_suspend_points(
+    tcx: TyCtxt<'a, 'tcx, 'tcx>,
     mir: &Mir<'tcx>,
     source: MirSource,
-                                               movable: bool) ->
+    movable: bool,
-                                               (liveness::LiveVarSet<Local>,
+) -> (
-                                                HashMap<BasicBlock, liveness::LiveVarSet<Local>>) {
+    liveness::LiveVarSet<Local>,
+    FxHashMap<BasicBlock, liveness::LiveVarSet<Local>>,
+) {
     let dead_unwinds = IdxSet::new_empty(mir.basic_blocks().len());
     let node_id = tcx.hir.as_local_node_id(source.def_id).unwrap();
 
@@ -413,7 +418,7 @@ fn locals_live_across_suspend_points<'a, 'tcx,>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
         &liveness,
     );
 
-    let mut storage_liveness_map = HashMap::new();
+    let mut storage_liveness_map = FxHashMap::default();
 
     for (block, data) in mir.basic_blocks().iter_enumerated() {
         if let TerminatorKind::Yield { .. } = data.terminator().kind {
@@ -477,9 +482,9 @@ fn compute_layout<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                             interior: Ty<'tcx>,
                             movable: bool,
                             mir: &mut Mir<'tcx>)
-    -> (HashMap<Local, (Ty<'tcx>, usize)>,
+    -> (FxHashMap<Local, (Ty<'tcx>, usize)>,
         GeneratorLayout<'tcx>,
-        HashMap<BasicBlock, liveness::LiveVarSet<Local>>)
+        FxHashMap<BasicBlock, liveness::LiveVarSet<Local>>)
 {
     // Use a liveness analysis to compute locals which are live across a suspension point
     let (live_locals, storage_liveness) = locals_live_across_suspend_points(tcx,

src/librustc_plugin/registry.rs

@@ -12,6 +12,7 @@
 
 use rustc::lint::{EarlyLintPassObject, LateLintPassObject, LintId, Lint};
 use rustc::session::Session;
+use rustc::util::nodemap::FxHashMap;
 
 use syntax::ext::base::{SyntaxExtension, NamedSyntaxExtension, NormalTT, IdentTT};
 use syntax::ext::base::MacroExpanderFn;
@@ -21,7 +22,6 @@ use syntax::ast;
 use syntax::feature_gate::AttributeType;
 use syntax_pos::Span;
 
-use std::collections::HashMap;
 use std::borrow::ToOwned;
 
 /// Structure used to register plugins.
@@ -53,7 +53,7 @@ pub struct Registry<'a> {
     pub late_lint_passes: Vec<LateLintPassObject>,
 
     #[doc(hidden)]
-    pub lint_groups: HashMap<&'static str, Vec<LintId>>,
+    pub lint_groups: FxHashMap<&'static str, Vec<LintId>>,
 
     #[doc(hidden)]
     pub llvm_passes: Vec<String>,
@@ -74,7 +74,7 @@ impl<'a> Registry<'a> {
             syntax_exts: vec![],
             early_lint_passes: vec![],
             late_lint_passes: vec![],
-            lint_groups: HashMap::new(),
+            lint_groups: FxHashMap::default(),
             llvm_passes: vec![],
             attributes: vec![],
             whitelisted_custom_derives: Vec::new(),

src/librustc_save_analysis/dump_visitor.rs

@@ -91,7 +91,7 @@ pub struct DumpVisitor<'l, 'tcx: 'l, 'll, O: DumpOutput + 'll> {
     // of macro use (callsite) spans. We store these to ensure
     // we only write one macro def per unique macro definition, and
     // one macro use per unique callsite span.
-    // mac_defs: HashSet<Span>,
+    // mac_defs: FxHashSet<Span>,
     macro_calls: FxHashSet<Span>,
 }
 
@@ -107,7 +107,7 @@ impl<'l, 'tcx: 'l, 'll, O: DumpOutput + 'll> DumpVisitor<'l, 'tcx, 'll, O> {
             dumper,
             span: span_utils.clone(),
             cur_scope: CRATE_NODE_ID,
-            // mac_defs: HashSet::new(),
+            // mac_defs: FxHashSet::default(),
             macro_calls: FxHashSet(),
         }
     }

src/librustdoc/html/markdown.rs

@@ -29,8 +29,9 @@
 
 #![allow(non_camel_case_types)]
 
+use rustc_data_structures::fx::FxHashMap;
 use std::cell::RefCell;
-use std::collections::{HashMap, VecDeque};
+use std::collections::VecDeque;
 use std::default::Default;
 use std::fmt::{self, Write};
 use std::borrow::Cow;
@@ -417,14 +418,14 @@ impl<'a, I: Iterator<Item = Event<'a>>> Iterator for SummaryLine<'a, I> {
 /// references.
 struct Footnotes<'a, I: Iterator<Item = Event<'a>>> {
     inner: I,
-    footnotes: HashMap<String, (Vec<Event<'a>>, u16)>,
+    footnotes: FxHashMap<String, (Vec<Event<'a>>, u16)>,
 }
 
 impl<'a, I: Iterator<Item = Event<'a>>> Footnotes<'a, I> {
     fn new(iter: I) -> Self {
         Footnotes {
             inner: iter,
-            footnotes: HashMap::new(),
+            footnotes: FxHashMap::default(),
         }
     }
     fn get_entry(&mut self, key: &str) -> &mut (Vec<Event<'a>>, u16) {
@@ -865,7 +866,7 @@ pub fn markdown_links(md: &str) -> Vec<(String, Option<Range<usize>>)> {
 
 #[derive(Default)]
 pub struct IdMap {
-    map: HashMap<String, usize>,
+    map: FxHashMap<String, usize>,
 }
 
 impl IdMap {
@@ -880,7 +881,7 @@ impl IdMap {
     }
 
     pub fn reset(&mut self) {
-        self.map = HashMap::new();
+        self.map = FxHashMap::default();
     }
 
     pub fn derive(&mut self, candidate: String) -> String {

src/librustdoc/html/render.rs

@@ -38,7 +38,7 @@ pub use self::ExternalLocation::*;
 use std::borrow::Cow;
 use std::cell::RefCell;
 use std::cmp::Ordering;
-use std::collections::{BTreeMap, HashSet, VecDeque};
+use std::collections::{BTreeMap, VecDeque};
 use std::default::Default;
 use std::error;
 use std::fmt::{self, Display, Formatter, Write as FmtWrite};
@@ -741,7 +741,7 @@ fn write_shared(cx: &Context,
 
     // To avoid "light.css" to be overwritten, we'll first run over the received themes and only
     // then we'll run over the "official" styles.
-    let mut themes: HashSet<String> = HashSet::new();
+    let mut themes: FxHashSet<String> = FxHashSet::default();
 
     for entry in &cx.shared.themes {
         let mut content = Vec::with_capacity(100000);
@@ -1539,35 +1539,36 @@ impl Ord for ItemEntry {
 
 #[derive(Debug)]
 struct AllTypes {
-    structs: HashSet<ItemEntry>,
+    structs: FxHashSet<ItemEntry>,
-    enums: HashSet<ItemEntry>,
+    enums: FxHashSet<ItemEntry>,
-    unions: HashSet<ItemEntry>,
+    unions: FxHashSet<ItemEntry>,
-    primitives: HashSet<ItemEntry>,
+    primitives: FxHashSet<ItemEntry>,
-    traits: HashSet<ItemEntry>,
+    traits: FxHashSet<ItemEntry>,
-    macros: HashSet<ItemEntry>,
+    macros: FxHashSet<ItemEntry>,
-    functions: HashSet<ItemEntry>,
+    functions: FxHashSet<ItemEntry>,
-    typedefs: HashSet<ItemEntry>,
+    typedefs: FxHashSet<ItemEntry>,
-    existentials: HashSet<ItemEntry>,
+    existentials: FxHashSet<ItemEntry>,
-    statics: HashSet<ItemEntry>,
+    statics: FxHashSet<ItemEntry>,
-    constants: HashSet<ItemEntry>,
+    constants: FxHashSet<ItemEntry>,
-    keywords: HashSet<ItemEntry>,
+    keywords: FxHashSet<ItemEntry>,
 }
 
 impl AllTypes {
     fn new() -> AllTypes {
+        let new_set = |cap| FxHashSet::with_capacity_and_hasher(cap, Default::default());
         AllTypes {
-            structs: HashSet::with_capacity(100),
+            structs: new_set(100),
-            enums: HashSet::with_capacity(100),
+            enums: new_set(100),
-            unions: HashSet::with_capacity(100),
+            unions: new_set(100),
-            primitives: HashSet::with_capacity(26),
+            primitives: new_set(26),
-            traits: HashSet::with_capacity(100),
+            traits: new_set(100),
-            macros: HashSet::with_capacity(100),
+            macros: new_set(100),
-            functions: HashSet::with_capacity(100),
+            functions: new_set(100),
-            typedefs: HashSet::with_capacity(100),
+            typedefs: new_set(100),
-            existentials: HashSet::with_capacity(100),
+            existentials: new_set(100),
-            statics: HashSet::with_capacity(100),
+            statics: new_set(100),
-            constants: HashSet::with_capacity(100),
+            constants: new_set(100),
-            keywords: HashSet::with_capacity(100),
+            keywords: new_set(100),
         }
     }
 
@@ -1595,7 +1596,7 @@ impl AllTypes {
     }
 }
 
-fn print_entries(f: &mut fmt::Formatter, e: &HashSet<ItemEntry>, title: &str,
+fn print_entries(f: &mut fmt::Formatter, e: &FxHashSet<ItemEntry>, title: &str,
                  class: &str) -> fmt::Result {
     if !e.is_empty() {
         let mut e: Vec<&ItemEntry> = e.iter().collect();
@@ -4185,7 +4186,7 @@ fn sidebar_assoc_items(it: &clean::Item) -> String {
                 }
             }
             let format_impls = |impls: Vec<&Impl>| {
-                let mut links = HashSet::new();
+                let mut links = FxHashSet::default();
                 impls.iter()
                            .filter_map(|i| {
                                let is_negative_impl = is_negative_impl(i.inner_impl());

src/librustdoc/theme.rs

@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use std::collections::HashSet;
+use rustc_data_structures::fx::FxHashSet;
 use std::fs::File;
 use std::hash::{Hash, Hasher};
 use std::io::Read;
@@ -31,7 +31,7 @@ macro_rules! try_something {
 #[derive(Debug, Clone, Eq)]
 pub struct CssPath {
     pub name: String,
-    pub children: HashSet<CssPath>,
+    pub children: FxHashSet<CssPath>,
 }
 
 // This PartialEq implementation IS NOT COMMUTATIVE!!!
@@ -66,7 +66,7 @@ impl CssPath {
     fn new(name: String) -> CssPath {
         CssPath {
             name,
-            children: HashSet::new(),
+            children: FxHashSet::default(),
         }
     }
 }
@@ -211,7 +211,7 @@ fn build_rule(v: &[u8], positions: &[usize]) -> String {
              .join(" ")
 }
 
-fn inner(v: &[u8], events: &[Events], pos: &mut usize) -> HashSet<CssPath> {
+fn inner(v: &[u8], events: &[Events], pos: &mut usize) -> FxHashSet<CssPath> {
     let mut paths = Vec::with_capacity(50);
 
     while *pos < events.len() {

src/libsyntax/ast.rs

@@ -28,8 +28,8 @@ use ThinVec;
 use tokenstream::{ThinTokenStream, TokenStream};
 
 use serialize::{self, Encoder, Decoder};
-use std::collections::HashSet;
 use std::fmt;
+use rustc_data_structures::fx::FxHashSet;
 use rustc_data_structures::sync::Lrc;
 use std::u32;
 
@@ -407,7 +407,7 @@ pub struct WhereEqPredicate {
 
 /// The set of MetaItems that define the compilation environment of the crate,
 /// used to drive conditional compilation
-pub type CrateConfig = HashSet<(Name, Option<Symbol>)>;
+pub type CrateConfig = FxHashSet<(Name, Option<Symbol>)>;
 
 #[derive(Clone, RustcEncodable, RustcDecodable, Debug)]
 pub struct Crate {

src/libsyntax/ext/base.rs

@@ -26,7 +26,7 @@ use OneVector;
 use symbol::{keywords, Ident, Symbol};
 use ThinVec;
 
-use std::collections::HashMap;
+use rustc_data_structures::fx::FxHashMap;
 use std::iter;
 use std::path::PathBuf;
 use std::rc::Rc;
@@ -800,7 +800,7 @@ pub struct ExtCtxt<'a> {
     pub resolver: &'a mut dyn Resolver,
     pub resolve_err_count: usize,
     pub current_expansion: ExpansionData,
-    pub expansions: HashMap<Span, Vec<String>>,
+    pub expansions: FxHashMap<Span, Vec<String>>,
 }
 
 impl<'a> ExtCtxt<'a> {
@@ -821,7 +821,7 @@ impl<'a> ExtCtxt<'a> {
                 directory_ownership: DirectoryOwnership::Owned { relative: None },
                 crate_span: None,
             },
-            expansions: HashMap::new(),
+            expansions: FxHashMap::default(),
         }
     }
 

src/libsyntax/ext/derive.rs

@@ -17,7 +17,7 @@ use parse::parser::PathStyle;
 use symbol::Symbol;
 use syntax_pos::Span;
 
-use std::collections::HashSet;
+use rustc_data_structures::fx::FxHashSet;
 
 pub fn collect_derives(cx: &mut ExtCtxt, attrs: &mut Vec<ast::Attribute>) -> Vec<ast::Path> {
     let mut result = Vec::new();
@@ -48,7 +48,7 @@ pub fn collect_derives(cx: &mut ExtCtxt, attrs: &mut Vec<ast::Attribute>) -> Vec
 pub fn add_derived_markers<T>(cx: &mut ExtCtxt, span: Span, traits: &[ast::Path], item: T) -> T
     where T: HasAttrs,
 {
-    let (mut names, mut pretty_name) = (HashSet::new(), "derive(".to_owned());
+    let (mut names, mut pretty_name) = (FxHashSet::default(), "derive(".to_owned());
     for (i, path) in traits.iter().enumerate() {
         if i > 0 {
             pretty_name.push_str(", ");

src/libsyntax/ext/expand.rs

@@ -34,7 +34,7 @@ use syntax_pos::hygiene::ExpnFormat;
 use tokenstream::{TokenStream, TokenTree};
 use visit::{self, Visitor};
 
-use std::collections::HashMap;
+use rustc_data_structures::fx::FxHashMap;
 use std::fs::File;
 use std::io::Read;
 use std::iter::FromIterator;
@@ -319,7 +319,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
         // Unresolved macros produce dummy outputs as a recovery measure.
         invocations.reverse();
         let mut expanded_fragments = Vec::new();
-        let mut derives: HashMap<Mark, Vec<_>> = HashMap::new();
+        let mut derives: FxHashMap<Mark, Vec<_>> = FxHashMap::default();
         let mut undetermined_invocations = Vec::new();
         let (mut progress, mut force) = (false, !self.monotonic);
         loop {

src/libsyntax/ext/placeholders.rs

@@ -21,7 +21,7 @@ use symbol::keywords;
 use ThinVec;
 use util::move_map::MoveMap;
 
-use std::collections::HashMap;
+use rustc_data_structures::fx::FxHashMap;
 
 pub fn placeholder(kind: AstFragmentKind, id: ast::NodeId) -> AstFragment {
     fn mac_placeholder() -> ast::Mac {
@@ -81,7 +81,7 @@ pub fn placeholder(kind: AstFragmentKind, id: ast::NodeId) -> AstFragment {
 }
 
 pub struct PlaceholderExpander<'a, 'b: 'a> {
-    expanded_fragments: HashMap<ast::NodeId, AstFragment>,
+    expanded_fragments: FxHashMap<ast::NodeId, AstFragment>,
     cx: &'a mut ExtCtxt<'b>,
     monotonic: bool,
 }
@@ -90,7 +90,7 @@ impl<'a, 'b> PlaceholderExpander<'a, 'b> {
     pub fn new(cx: &'a mut ExtCtxt<'b>, monotonic: bool) -> Self {
         PlaceholderExpander {
             cx,
-            expanded_fragments: HashMap::new(),
+            expanded_fragments: FxHashMap::default(),
             monotonic,
         }
     }

src/libsyntax/ext/tt/macro_parser.rs

@@ -96,11 +96,11 @@ use OneVector;
 use symbol::keywords;
 use tokenstream::TokenStream;
 
+use rustc_data_structures::fx::FxHashMap;
+use std::collections::hash_map::Entry::{Occupied, Vacant};
 use std::mem;
 use std::ops::{Deref, DerefMut};
 use std::rc::Rc;
-use std::collections::HashMap;
-use std::collections::hash_map::Entry::{Occupied, Vacant};
 
 // To avoid costly uniqueness checks, we require that `MatchSeq` always has a nonempty body.
 
@@ -263,7 +263,7 @@ pub enum ParseResult<T> {
 
 /// A `ParseResult` where the `Success` variant contains a mapping of `Ident`s to `NamedMatch`es.
 /// This represents the mapping of metavars to the token trees they bind to.
-pub type NamedParseResult = ParseResult<HashMap<Ident, Rc<NamedMatch>>>;
+pub type NamedParseResult = ParseResult<FxHashMap<Ident, Rc<NamedMatch>>>;
 
 /// Count how many metavars are named in the given matcher `ms`.
 pub fn count_names(ms: &[TokenTree]) -> usize {
@@ -351,7 +351,7 @@ fn nameize<I: Iterator<Item = NamedMatch>>(
         sess: &ParseSess,
         m: &TokenTree,
         res: &mut I,
-        ret_val: &mut HashMap<Ident, Rc<NamedMatch>>,
+        ret_val: &mut FxHashMap<Ident, Rc<NamedMatch>>,
     ) -> Result<(), (syntax_pos::Span, String)> {
         match *m {
             TokenTree::Sequence(_, ref seq) => for next_m in &seq.tts {
@@ -382,7 +382,7 @@ fn nameize<I: Iterator<Item = NamedMatch>>(
         Ok(())
     }
 
-    let mut ret_val = HashMap::new();
+    let mut ret_val = FxHashMap::default();
     for m in ms {
         match n_rec(sess, m, res.by_ref(), &mut ret_val) {
             Ok(_) => {}

src/libsyntax/ext/tt/macro_rules.rs

@@ -27,8 +27,8 @@ use parse::token::Token::*;
 use symbol::Symbol;
 use tokenstream::{TokenStream, TokenTree};
 
+use rustc_data_structures::fx::FxHashMap;
 use std::borrow::Cow;
-use std::collections::HashMap;
 use std::collections::hash_map::Entry;
 
 use rustc_data_structures::sync::Lrc;
@@ -451,14 +451,14 @@ struct FirstSets {
     // If two sequences have the same span in a matcher, then map that
     // span to None (invalidating the mapping here and forcing the code to
     // use a slow path).
-    first: HashMap<Span, Option<TokenSet>>,
+    first: FxHashMap<Span, Option<TokenSet>>,
 }
 
 impl FirstSets {
     fn new(tts: &[quoted::TokenTree]) -> FirstSets {
         use self::quoted::TokenTree;
 
-        let mut sets = FirstSets { first: HashMap::new() };
+        let mut sets = FirstSets { first: FxHashMap::default() };
         build_recur(&mut sets, tts);
         return sets;
 

src/libsyntax/ext/tt/transcribe.rs

@@ -19,11 +19,11 @@ use OneVector;
 use syntax_pos::{Span, DUMMY_SP};
 use tokenstream::{TokenStream, TokenTree, Delimited};
 
-use std::rc::Rc;
+use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sync::Lrc;
 use std::mem;
 use std::ops::Add;
-use std::collections::HashMap;
+use std::rc::Rc;
 
 // An iterator over the token trees in a delimited token tree (`{ ... }`) or a sequence (`$(...)`).
 enum Frame {
@@ -67,11 +67,11 @@ impl Iterator for Frame {
 /// `src` contains no `TokenTree::{Sequence, MetaVar, MetaVarDecl}`s, `interp` can
 /// (and should) be None.
 pub fn transcribe(cx: &ExtCtxt,
-                  interp: Option<HashMap<Ident, Rc<NamedMatch>>>,
+                  interp: Option<FxHashMap<Ident, Rc<NamedMatch>>>,
                   src: Vec<quoted::TokenTree>)
                   -> TokenStream {
     let mut stack: OneVector<Frame> = smallvec![Frame::new(src)];
-    let interpolations = interp.unwrap_or_else(HashMap::new); /* just a convenience */
+    let interpolations = interp.unwrap_or_else(FxHashMap::default); /* just a convenience */
     let mut repeats = Vec::new();
     let mut result: Vec<TokenStream> = Vec::new();
     let mut result_stack = Vec::new();
@@ -187,7 +187,7 @@ pub fn transcribe(cx: &ExtCtxt,
 }
 
 fn lookup_cur_matched(ident: Ident,
-                      interpolations: &HashMap<Ident, Rc<NamedMatch>>,
+                      interpolations: &FxHashMap<Ident, Rc<NamedMatch>>,
                       repeats: &[(usize, usize)])
                       -> Option<Rc<NamedMatch>> {
     interpolations.get(&ident).map(|matched| {
@@ -234,7 +234,7 @@ impl Add for LockstepIterSize {
 }
 
 fn lockstep_iter_size(tree: &quoted::TokenTree,
-                      interpolations: &HashMap<Ident, Rc<NamedMatch>>,
+                      interpolations: &FxHashMap<Ident, Rc<NamedMatch>>,
                       repeats: &[(usize, usize)])
                       -> LockstepIterSize {
     use self::quoted::TokenTree;

src/libsyntax/parse/lexer/mod.rs

@@ -1831,10 +1831,10 @@ mod tests {
     use errors;
     use feature_gate::UnstableFeatures;
     use parse::token;
-    use std::collections::HashSet;
     use std::io;
     use std::path::PathBuf;
     use diagnostics::plugin::ErrorMap;
+    use rustc_data_structures::fx::FxHashSet;
     use rustc_data_structures::sync::Lock;
     use with_globals;
     fn mk_sess(cm: Lrc<SourceMap>) -> ParseSess {
@@ -1845,10 +1845,10 @@ mod tests {
         ParseSess {
             span_diagnostic: errors::Handler::with_emitter(true, false, Box::new(emitter)),
             unstable_features: UnstableFeatures::from_environment(),
-            config: CrateConfig::new(),
+            config: CrateConfig::default(),
             included_mod_stack: Lock::new(Vec::new()),
             code_map: cm,
-            missing_fragment_specifiers: Lock::new(HashSet::new()),
+            missing_fragment_specifiers: Lock::new(FxHashSet::default()),
             raw_identifier_spans: Lock::new(Vec::new()),
             registered_diagnostics: Lock::new(ErrorMap::new()),
             non_modrs_mods: Lock::new(vec![]),

src/libsyntax/parse/mod.rs

@@ -24,8 +24,8 @@ use symbol::Symbol;
 use tokenstream::{TokenStream, TokenTree};
 use diagnostics::plugin::ErrorMap;
 
+use rustc_data_structures::fx::FxHashSet;
 use std::borrow::Cow;
-use std::collections::HashSet;
 use std::iter;
 use std::path::{Path, PathBuf};
 use std::str;
@@ -46,7 +46,7 @@ pub struct ParseSess {
     pub span_diagnostic: Handler,
     pub unstable_features: UnstableFeatures,
     pub config: CrateConfig,
-    pub missing_fragment_specifiers: Lock<HashSet<Span>>,
+    pub missing_fragment_specifiers: Lock<FxHashSet<Span>>,
     /// Places where raw identifiers were used. This is used for feature gating
     /// raw identifiers
     pub raw_identifier_spans: Lock<Vec<Span>>,
@@ -75,8 +75,8 @@ impl ParseSess {
         ParseSess {
             span_diagnostic: handler,
             unstable_features: UnstableFeatures::from_environment(),
-            config: HashSet::new(),
+            config: FxHashSet::default(),
-            missing_fragment_specifiers: Lock::new(HashSet::new()),
+            missing_fragment_specifiers: Lock::new(FxHashSet::default()),
             raw_identifier_spans: Lock::new(Vec::new()),
             registered_diagnostics: Lock::new(ErrorMap::new()),
             included_mod_stack: Lock::new(vec![]),

src/libsyntax_ext/format.rs

@@ -24,9 +24,9 @@ use syntax::tokenstream;
 use syntax_pos::{MultiSpan, Span, DUMMY_SP};
 use errors::Applicability;
 
+use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use std::borrow::Cow;
 use std::collections::hash_map::Entry;
-use std::collections::{HashMap, HashSet};
 
 #[derive(PartialEq)]
 enum ArgumentType {
@@ -65,7 +65,7 @@ struct Context<'a, 'b: 'a> {
     /// Unique format specs seen for each argument.
     arg_unique_types: Vec<Vec<ArgumentType>>,
     /// Map from named arguments to their resolved indices.
-    names: HashMap<String, usize>,
+    names: FxHashMap<String, usize>,
 
     /// The latest consecutive literal strings, or empty if there weren't any.
     literal: String,
@@ -104,7 +104,7 @@ struct Context<'a, 'b: 'a> {
     /// * `count_args`: `vec![Exact(0), Exact(5), Exact(3)]`
     count_args: Vec<Position>,
     /// Relative slot numbers for count arguments.
-    count_positions: HashMap<usize, usize>,
+    count_positions: FxHashMap<usize, usize>,
     /// Number of count slots assigned.
     count_positions_count: usize,
 
@@ -134,9 +134,9 @@ struct Context<'a, 'b: 'a> {
 fn parse_args(ecx: &mut ExtCtxt,
               sp: Span,
               tts: &[tokenstream::TokenTree])
-              -> Option<(P<ast::Expr>, Vec<P<ast::Expr>>, HashMap<String, usize>)> {
+              -> Option<(P<ast::Expr>, Vec<P<ast::Expr>>, FxHashMap<String, usize>)> {
     let mut args = Vec::<P<ast::Expr>>::new();
-    let mut names = HashMap::<String, usize>::new();
+    let mut names = FxHashMap::<String, usize>::default();
 
     let mut p = ecx.new_parser_from_tts(tts);
 
@@ -768,7 +768,7 @@ pub fn expand_preparsed_format_args(ecx: &mut ExtCtxt,
                                     sp: Span,
                                     efmt: P<ast::Expr>,
                                     args: Vec<P<ast::Expr>>,
-                                    names: HashMap<String, usize>,
+                                    names: FxHashMap<String, usize>,
                                     append_newline: bool)
                                     -> P<ast::Expr> {
     // NOTE: this verbose way of initializing `Vec<Vec<ArgumentType>>` is because
@@ -852,7 +852,7 @@ pub fn expand_preparsed_format_args(ecx: &mut ExtCtxt,
         curpiece: 0,
         arg_index_map: Vec::new(),
         count_args: Vec::new(),
-        count_positions: HashMap::new(),
+        count_positions: FxHashMap::default(),
         count_positions_count: 0,
         count_args_index_offset: 0,
         literal: String::new(),
@@ -952,7 +952,7 @@ pub fn expand_preparsed_format_args(ecx: &mut ExtCtxt,
 
             // The set of foreign substitutions we've explained.  This prevents spamming the user
             // with `%d should be written as {}` over and over again.
-            let mut explained = HashSet::new();
+            let mut explained = FxHashSet::default();
 
             macro_rules! check_foreign {
                 ($kind:ident) => {{

src/libsyntax_pos/hygiene.rs

@@ -21,8 +21,7 @@ use edition::Edition;
 use symbol::Symbol;
 
 use serialize::{Encodable, Decodable, Encoder, Decoder};
-use std::collections::HashMap;
+use rustc_data_structures::fx::{FxHashMap, FxHashSet};
-use rustc_data_structures::fx::FxHashSet;
 use std::fmt;
 
 /// A SyntaxContext represents a chain of macro expansions (represented by marks).
@@ -190,7 +189,7 @@ impl Mark {
 crate struct HygieneData {
     marks: Vec<MarkData>,
     syntax_contexts: Vec<SyntaxContextData>,
-    markings: HashMap<(SyntaxContext, Mark, Transparency), SyntaxContext>,
+    markings: FxHashMap<(SyntaxContext, Mark, Transparency), SyntaxContext>,
     default_edition: Edition,
 }
 
@@ -212,7 +211,7 @@ impl HygieneData {
                 opaque: SyntaxContext(0),
                 opaque_and_semitransparent: SyntaxContext(0),
             }],
-            markings: HashMap::new(),
+            markings: FxHashMap::default(),
             default_edition: Edition::Edition2015,
         }
     }
@@ -231,7 +230,7 @@ pub fn set_default_edition(edition: Edition) {
 }
 
 pub fn clear_markings() {
-    HygieneData::with(|data| data.markings = HashMap::new());
+    HygieneData::with(|data| data.markings = FxHashMap::default());
 }
 
 impl SyntaxContext {