Auto merge of #45282 - stjepang:experiment-ordermap, r=<try>

[Experiment] Replace HashMap with OrderMap

Do not merge.

This is just a simple experiment where I modified `FxHashMap` to use `OrderMap` instead of `HashMap`, as explained in #45273. Don't expect the code to look good. :)

cc @Mark-Simulacrum - Can we please run performance tests to see how this PR impacts compile times?
cc @bluss @kennytm

@eddyb said on IRC that we shouldn't blindly swap the implementation just yet - let's investigate a bit further. If changing the hash map implementation affects performance a lot, then we can probably gain even more by using a different data structure.

Author: bors

src/Cargo.lock

@@ -23,6 +23,7 @@ rustc_errors = { path = "../librustc_errors" }
 serialize = { path = "../libserialize" }
 syntax = { path = "../libsyntax" }
 syntax_pos = { path = "../libsyntax_pos" }
+ordermap = "0.3.0"
 
 # Note that these dependencies are a lie, they're just here to get linkage to
 # work.

src/librustc/Cargo.toml

@@ -41,7 +41,7 @@ impl DepGraphQuery {
     }
 
     pub fn contains_node(&self, node: &DepNode) -> bool {
-        self.indices.contains_key(&node)
+        self.indices.contains_key(node)
     }
 
     pub fn nodes(&self) -> Vec<&DepNode> {
@@ -83,7 +83,7 @@ impl DepGraphQuery {
 
     /// Just the outgoing edges from `node`.
     pub fn immediate_successors(&self, node: &DepNode) -> Vec<&DepNode> {
-        if let Some(&index) = self.indices.get(&node) {
+        if let Some(&index) = self.indices.get(node) {
             self.graph.successor_nodes(index)
                       .map(|s| self.graph.node_data(s))
                       .collect()

src/librustc/dep_graph/query.rs

@@ -21,7 +21,7 @@ use session::Session;
 use std::cmp::Ord;
 use std::hash as std_hash;
 use std::cell::RefCell;
-use std::collections::HashMap;
+use ordermap::OrderMap;
 
 use syntax::ast;
 use syntax::attr;
@@ -426,7 +426,7 @@ pub fn hash_stable_trait_impls<'gcx, W, R>(
     hcx: &mut StableHashingContext<'gcx>,
     hasher: &mut StableHasher<W>,
     blanket_impls: &Vec<DefId>,
-    non_blanket_impls: &HashMap<fast_reject::SimplifiedType, Vec<DefId>, R>)
+    non_blanket_impls: &OrderMap<fast_reject::SimplifiedType, Vec<DefId>, R>)
     where W: StableHasherResult,
           R: std_hash::BuildHasher,
 {

src/librustc/ich/hcx.rs

@@ -47,7 +47,7 @@ use ty::subst::Substs;
 use util::nodemap::FxHashMap;
 use hir::def_id::DefId;
 
-use std::collections::hash_map::Entry;
+use ordermap::Entry;
 
 use super::InferCtxt;
 use super::unify_key::ToType;

src/librustc/infer/freshen.rs

@@ -28,7 +28,7 @@ use infer::region_inference::RegionVarBindings;
 use util::nodemap::{FxHashMap, FxHashSet};
 
 use std::borrow::Cow;
-use std::collections::hash_map::Entry::Vacant;
+use ordermap::Entry::Vacant;
 use std::env;
 use std::fs::File;
 use std::io;

src/librustc/infer/region_inference/graphviz.rs

@@ -62,6 +62,7 @@
 
 #![recursion_limit="256"]
 
+extern crate ordermap;
 extern crate arena;
 #[macro_use] extern crate bitflags;
 extern crate core;

src/librustc/lib.rs

@@ -1263,7 +1263,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
         let trait_ref = &cache_fresh_trait_pred.0.trait_ref;
         if self.can_use_global_caches(param_env) {
             let cache = tcx.selection_cache.hashmap.borrow();
-            if let Some(cached) = cache.get(&trait_ref) {
+            if let Some(cached) = cache.get(trait_ref) {
                 return Some(cached.get(tcx));
             }
         }

src/librustc/traits/select.rs

@@ -53,15 +53,16 @@ use rustc_data_structures::accumulate_vec::AccumulateVec;
 use rustc_data_structures::stable_hasher::{HashStable, hash_stable_hashmap,
                                            StableHasher, StableHasherResult,
                                            StableVec};
+use rustc_data_structures;
 use arena::{TypedArena, DroplessArena};
 use rustc_const_math::{ConstInt, ConstUsize};
 use rustc_data_structures::indexed_vec::IndexVec;
 use std::any::Any;
 use std::borrow::Borrow;
 use std::cell::{Cell, RefCell};
 use std::cmp::Ordering;
-use std::collections::hash_map::{self, Entry};
-use std::hash::{Hash, Hasher};
+use ordermap::{self, Entry};
+use std::hash::{BuildHasherDefault, Hash, Hasher};
 use std::mem;
 use std::ops::Deref;
 use std::iter;
@@ -275,7 +276,7 @@ impl<'a, V> LocalTableInContext<'a, V> {
         self.data.get(&id.local_id)
     }
 
-    pub fn iter(&self) -> hash_map::Iter<hir::ItemLocalId, V> {
+    pub fn iter(&self) -> ordermap::Iter<hir::ItemLocalId, V> {
         self.data.iter()
     }
 }
@@ -299,7 +300,10 @@ impl<'a, V> LocalTableInContextMut<'a, V> {
         self.data.get_mut(&id.local_id)
     }
 
-    pub fn entry(&mut self, id: hir::HirId) -> Entry<hir::ItemLocalId, V> {
+    pub fn entry(
+        &mut self,
+        id: hir::HirId
+    ) -> Entry<hir::ItemLocalId, V, BuildHasherDefault<rustc_data_structures::fx::FxHasher>> {
         validate_hir_id_for_typeck_tables(self.local_id_root, id, true);
         self.data.entry(id.local_id)
     }

src/librustc/ty/context.rs

@@ -11,3 +11,4 @@ crate-type = ["dylib"]
 [dependencies]
 log = "0.3"
 serialize = { path = "../libserialize" }
+ordermap = "0.3.0"

src/librustc_data_structures/Cargo.toml

@@ -8,17 +8,20 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use std::collections::{HashMap, HashSet};
+use std::collections::HashSet;
 use std::default::Default;
 use std::hash::{Hasher, Hash, BuildHasherDefault};
 use std::ops::BitXor;
+use ordermap::OrderMap;
 
-pub type FxHashMap<K, V> = HashMap<K, V, BuildHasherDefault<FxHasher>>;
+// pub type FxHashMap<K, V> = HashMap<K, V, BuildHasherDefault<FxHasher>>;
 pub type FxHashSet<V> = HashSet<V, BuildHasherDefault<FxHasher>>;
 
+pub type FxHashMap<K, V> = OrderMap<K, V, BuildHasherDefault<FxHasher>>;
+
 #[allow(non_snake_case)]
 pub fn FxHashMap<K: Hash + Eq, V>() -> FxHashMap<K, V> {
-    HashMap::default()
+    Default::default()
 }
 
 #[allow(non_snake_case)]

src/librustc_data_structures/fx.rs

@@ -40,6 +40,7 @@ extern crate log;
 extern crate serialize as rustc_serialize; // used by deriving
 #[cfg(unix)]
 extern crate libc;
+extern crate ordermap;
 
 pub use rustc_serialize::hex::ToHex;
 

src/librustc_data_structures/lib.rs

@@ -18,7 +18,7 @@
 use fx::{FxHashMap, FxHashSet};
 
 use std::cell::Cell;
-use std::collections::hash_map::Entry;
+use super::ordermap::Entry;
 use std::fmt::Debug;
 use std::hash;
 use std::marker::PhantomData;

src/librustc_data_structures/obligation_forest/mod.rs

@@ -13,6 +13,7 @@ use std::marker::PhantomData;
 use std::mem;
 use blake2b::Blake2bHasher;
 use rustc_serialize::leb128;
+use ordermap::OrderMap;
 
 fn write_unsigned_leb128_to_buf(buf: &mut [u8; 16], value: u64) -> usize {
     leb128::write_unsigned_leb128_to(value as u128, |i, v| buf[i] = v)
@@ -482,7 +483,7 @@ impl<I: ::indexed_vec::Idx, CTX> HashStable<CTX> for ::indexed_set::IdxSetBuf<I>
 impl_stable_hash_via_hash!(::std::path::Path);
 impl_stable_hash_via_hash!(::std::path::PathBuf);
 
-impl<K, V, R, HCX> HashStable<HCX> for ::std::collections::HashMap<K, V, R>
+impl<K, V, R, HCX> HashStable<HCX> for OrderMap<K, V, R>
     where K: ToStableHashKey<HCX> + Eq + Hash,
           V: HashStable<HCX>,
           R: BuildHasher,
@@ -542,7 +543,7 @@ impl<K, HCX> HashStable<HCX> for ::std::collections::BTreeSet<K>
 pub fn hash_stable_hashmap<HCX, K, V, R, SK, F, W>(
     hcx: &mut HCX,
     hasher: &mut StableHasher<W>,
-    map: &::std::collections::HashMap<K, V, R>,
+    map: &OrderMap<K, V, R>,
     to_stable_hash_key: F)
     where K: Eq + Hash,
           V: HashStable<HCX>,

src/librustc_data_structures/stable_hasher.rs

@@ -16,3 +16,4 @@ rustc_back = { path = "../librustc_back" }
 rustc_const_eval = { path = "../librustc_const_eval" }
 syntax = { path = "../libsyntax" }
 syntax_pos = { path = "../libsyntax_pos" }
+ordermap = "0.3.0"

src/librustc_lint/Cargo.toml

@@ -41,6 +41,7 @@ extern crate log;
 extern crate rustc_back;
 extern crate rustc_const_eval;
 extern crate syntax_pos;
+extern crate ordermap;
 
 use rustc::lint;
 use rustc::middle;

src/librustc_lint/lib.rs

@@ -15,7 +15,7 @@ use util::nodemap::FxHashMap;
 use lint::{LateContext, EarlyContext, LintContext, LintArray};
 use lint::{LintPass, EarlyLintPass, LateLintPass};
 
-use std::collections::hash_map::Entry::{Occupied, Vacant};
+use ordermap::Entry::{Occupied, Vacant};
 
 use syntax::ast;
 use syntax::attr;

src/librustc_lint/unused.rs

@@ -21,3 +21,4 @@ serialize = { path = "../libserialize" }
 syntax = { path = "../libsyntax" }
 syntax_ext = { path = "../libsyntax_ext" }
 syntax_pos = { path = "../libsyntax_pos" }
+ordermap = "0.3.0"

src/librustc_metadata/Cargo.toml

@@ -290,7 +290,7 @@ pub fn provide_local<'tcx>(providers: &mut Providers<'tcx>) {
         // external item to be parents).
         visible_parent_map: |tcx, cnum| {
             use std::collections::vec_deque::VecDeque;
-            use std::collections::hash_map::Entry;
+            use ordermap::Entry;
 
             assert_eq!(cnum, LOCAL_CRATE);
             let mut visible_parent_map: DefIdMap<DefId> = DefIdMap();
@@ -313,7 +313,7 @@ pub fn provide_local<'tcx>(providers: &mut Providers<'tcx>) {
                     }
 
                     match visible_parent_map.entry(child) {
-                        Entry::Occupied(mut entry) => {
+                        Entry::Occupied(entry) => {
                             // If `child` is defined in crate `cnum`, ensure
                             // that it is mapped to a parent in `cnum`.
                             if child.krate == cnum && entry.get().krate != cnum {

src/librustc_metadata/cstore_impl.rs

@@ -39,6 +39,7 @@ extern crate proc_macro;
 extern crate rustc;
 extern crate rustc_back;
 extern crate rustc_data_structures;
+extern crate ordermap;
 
 mod diagnostics;
 

src/librustc_metadata/lib.rs

@@ -20,3 +20,4 @@ rustc_errors = { path = "../librustc_errors" }
 serialize = { path = "../libserialize" }
 syntax = { path = "../libsyntax" }
 syntax_pos = { path = "../libsyntax_pos" }
+ordermap = "0.3.0"

src/librustc_mir/Cargo.toml

@@ -117,7 +117,7 @@ impl<'a, 'tcx> Borrows<'a, 'tcx> {
     }
 
     pub fn region_span(&self, region: &Region) -> Span {
-        let opt_span = self.region_span_map.get(region);
+        let opt_span = self.region_span_map.get(*region);
         assert!(opt_span.is_some(), "end region not found for {:?}", region);
         *opt_span.unwrap()
     }

src/librustc_mir/dataflow/impls/borrows.rs

@@ -16,7 +16,7 @@ use rustc_data_structures::indexed_vec::{IndexVec};
 
 use syntax::codemap::DUMMY_SP;
 
-use std::collections::hash_map::Entry;
+use ordermap::Entry;
 use std::mem;
 
 use super::abs_domain::Lift;

src/librustc_mir/dataflow/move_paths/builder.rs

@@ -41,6 +41,7 @@ extern crate syntax_pos;
 extern crate rustc_const_math;
 extern crate rustc_const_eval;
 extern crate core; // for NonZero
+extern crate ordermap;
 
 mod diagnostics;
 

src/librustc_mir/lib.rs

@@ -16,3 +16,4 @@ rustc_const_math = { path = "../librustc_const_math" }
 syntax = { path = "../libsyntax" }
 syntax_pos = { path = "../libsyntax_pos" }
 rustc_errors = { path = "../librustc_errors" }
+ordermap = "0.3.0"

src/librustc_passes/Cargo.toml

@@ -50,7 +50,7 @@ use syntax::ast;
 use syntax_pos::{Span, DUMMY_SP};
 use rustc::hir::intravisit::{self, Visitor, NestedVisitorMap};
 
-use std::collections::hash_map::Entry;
+use ordermap::Entry;
 use std::cmp::Ordering;
 
 struct CheckCrateVisitor<'a, 'tcx: 'a> {

src/librustc_passes/consts.rs

@@ -32,6 +32,7 @@ extern crate log;
 extern crate syntax;
 extern crate syntax_pos;
 extern crate rustc_errors as errors;
+extern crate ordermap;
 
 mod diagnostics;
 

src/librustc_passes/lib.rs

@@ -30,6 +30,7 @@ rustc_trans_utils = { path = "../librustc_trans_utils" }
 serialize = { path = "../libserialize" }
 syntax = { path = "../libsyntax" }
 syntax_pos = { path = "../libsyntax_pos" }
+ordermap = "0.3.0"
 
 [target."cfg(windows)".dependencies]
 cc = "1.0"