Auto merge of #53384 - gootorov:use-servo-smallvec, r=michaelwoerister

Use optimized SmallVec implementation

This PR replaces current SmallVec implementation with the one from the Servo project.

Closes #51640

r? @Mark-Simulacrum

src/Cargo.lock

@@ -554,7 +554,7 @@ dependencies = [
  "crossbeam-utils 0.4.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "parking_lot 0.5.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.5.4 (registry+https://github.com/rust-lang/crates.io-index)",
- "smallvec 0.6.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "smallvec 0.6.5 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1488,7 +1488,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "libc 0.2.43 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "smallvec 0.6.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "smallvec 0.6.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -1925,6 +1925,7 @@ dependencies = [
  "rustc_target 0.0.0",
  "scoped-tls 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "serialize 0.0.0",
+ "smallvec 0.6.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "syntax 0.0.0",
  "syntax_pos 0.0.0",
  "tempfile 3.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -2086,6 +2087,7 @@ dependencies = [
  "rustc_data_structures 0.0.0",
  "rustc_errors 0.0.0",
  "rustc_target 0.0.0",
+ "smallvec 0.6.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "syntax 0.0.0",
  "syntax_pos 0.0.0",
 ]
@@ -2172,6 +2174,7 @@ dependencies = [
  "rustc-rayon-core 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc_cratesio_shim 0.0.0",
  "serialize 0.0.0",
+ "smallvec 0.6.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "stable_deref_trait 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -2317,6 +2320,7 @@ dependencies = [
  "rustc_errors 0.0.0",
  "rustc_target 0.0.0",
  "serialize 0.0.0",
+ "smallvec 0.6.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "syntax 0.0.0",
  "syntax_pos 0.0.0",
 ]
@@ -2422,6 +2426,7 @@ dependencies = [
  "log 0.4.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc 0.0.0",
  "rustc_data_structures 0.0.0",
+ "smallvec 0.6.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "syntax 0.0.0",
  "syntax_pos 0.0.0",
 ]
@@ -2597,6 +2602,9 @@ dependencies = [
 [[package]]
 name = "serialize"
 version = "0.0.0"
+dependencies = [
+ "smallvec 0.6.5 (registry+https://github.com/rust-lang/crates.io-index)",
+]
 
 [[package]]
 name = "shell-escape"
@@ -2615,7 +2623,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "smallvec"
-version = "0.6.3"
+version = "0.6.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "unreachable 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -2771,6 +2779,7 @@ dependencies = [
  "rustc_target 0.0.0",
  "scoped-tls 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "serialize 0.0.0",
+ "smallvec 0.6.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "syntax_pos 0.0.0",
 ]
 
@@ -2783,6 +2792,7 @@ dependencies = [
  "rustc_data_structures 0.0.0",
  "rustc_errors 0.0.0",
  "rustc_target 0.0.0",
+ "smallvec 0.6.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "syntax 0.0.0",
  "syntax_pos 0.0.0",
 ]
@@ -3327,7 +3337,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum shell-escape 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)" = "170a13e64f2a51b77a45702ba77287f5c6829375b04a69cf2222acd17d0cfab9"
 "checksum shlex 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "7fdf1b9db47230893d76faad238fd6097fd6d6a9245cd7a4d90dbd639536bbd2"
 "checksum siphasher 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "0df90a788073e8d0235a67e50441d47db7c8ad9debd91cbf43736a2a92d36537"
-"checksum smallvec 0.6.3 (registry+https://github.com/rust-lang/crates.io-index)" = "26df3bb03ca5eac2e64192b723d51f56c1b1e0860e7c766281f4598f181acdc8"
+"checksum smallvec 0.6.5 (registry+https://github.com/rust-lang/crates.io-index)" = "153ffa32fd170e9944f7e0838edf824a754ec4c1fc64746fcc9fe1f8fa602e5d"
 "checksum socket2 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)" = "962a516af4d3a7c272cb3a1d50a8cc4e5b41802e4ad54cfb7bee8ba61d37d703"
 "checksum stable_deref_trait 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "ffbc596e092fe5f598b12ef46cc03754085ac2f4d8c739ad61c4ae266cc3b3fa"
 "checksum string_cache 0.7.3 (registry+https://github.com/rust-lang/crates.io-index)" = "25d70109977172b127fe834e5449e5ab1740b9ba49fa18a2020f509174f25423"

src/librustc/Cargo.toml

@@ -33,6 +33,7 @@ parking_lot = "0.5.5"
 byteorder = { version = "1.1", features = ["i128"]}
 chalk-engine = { version = "0.7.0", default-features=false }
 rustc_fs_util = { path = "../librustc_fs_util" }
+smallvec = { version = "0.6.5", features = ["union"] }
 
 # Note that these dependencies are a lie, they're just here to get linkage to
 # work.

src/librustc/dep_graph/graph.rs

@@ -12,7 +12,7 @@ use errors::DiagnosticBuilder;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_data_structures::indexed_vec::{Idx, IndexVec};
-use rustc_data_structures::small_vec::SmallVec;
+use smallvec::SmallVec;
 use rustc_data_structures::sync::{Lrc, Lock};
 use std::env;
 use std::hash::Hash;
@@ -1025,7 +1025,7 @@ impl CurrentDepGraph {
         } = task {
             debug_assert_eq!(node, key);
             let krate_idx = self.node_to_node_index[&DepNode::new_no_params(DepKind::Krate)];
-            self.alloc_node(node, SmallVec::one(krate_idx))
+            self.alloc_node(node, smallvec![krate_idx])
         } else {
             bug!("complete_eval_always_task() - Expected eval always task to be popped");
         }

src/librustc/hir/lowering.rs

@@ -3178,26 +3178,26 @@ impl<'a> LoweringContext<'a> {
     fn lower_item_id(&mut self, i: &Item) -> OneVector<hir::ItemId> {
         match i.node {
             ItemKind::Use(ref use_tree) => {
-                let mut vec = OneVector::one(hir::ItemId { id: i.id });
+                let mut vec = smallvec![hir::ItemId { id: i.id }];
                 self.lower_item_id_use_tree(use_tree, i.id, &mut vec);
                 vec
             }
             ItemKind::MacroDef(..) => OneVector::new(),
             ItemKind::Fn(ref decl, ref header, ..) => {
-                let mut ids = OneVector::one(hir::ItemId { id: i.id });
+                let mut ids = smallvec![hir::ItemId { id: i.id }];
                 self.lower_impl_trait_ids(decl, header, &mut ids);
                 ids
             },
             ItemKind::Impl(.., None, _, ref items) => {
-                let mut ids = OneVector::one(hir::ItemId { id: i.id });
+                let mut ids = smallvec![hir::ItemId { id: i.id }];
                 for item in items {
                     if let ImplItemKind::Method(ref sig, _) = item.node {
                         self.lower_impl_trait_ids(&sig.decl, &sig.header, &mut ids);
                     }
                 }
                 ids
             },
-            _ => OneVector::one(hir::ItemId { id: i.id }),
+            _ => smallvec![hir::ItemId { id: i.id }],
         }
     }
 
@@ -4297,7 +4297,7 @@ impl<'a> LoweringContext<'a> {
     }
 
     fn lower_stmt(&mut self, s: &Stmt) -> OneVector<hir::Stmt> {
-        OneVector::one(match s.node {
+        smallvec![match s.node {
             StmtKind::Local(ref l) => Spanned {
                 node: hir::StmtKind::Decl(
                     P(Spanned {
@@ -4336,7 +4336,7 @@ impl<'a> LoweringContext<'a> {
                 span: s.span,
             },
             StmtKind::Mac(..) => panic!("Shouldn't exist here"),
-        })
+        }]
     }
 
     fn lower_capture_clause(&mut self, c: CaptureBy) -> hir::CaptureClause {

src/librustc/infer/canonical/canonicalizer.rs

@@ -27,7 +27,7 @@ use ty::{self, CanonicalVar, Lift, List, Ty, TyCtxt, TypeFlags};
 
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::indexed_vec::Idx;
-use rustc_data_structures::small_vec::SmallVec;
+use smallvec::SmallVec;
 
 impl<'cx, 'gcx, 'tcx> InferCtxt<'cx, 'gcx, 'tcx> {
     /// Canonicalizes a query value `V`. When we canonicalize a query,
@@ -380,7 +380,7 @@ impl<'cx, 'gcx, 'tcx> Canonicalizer<'cx, 'gcx, 'tcx> {
         // avoid allocations in those cases. We also don't use `indices` to
         // determine if a kind has been seen before until the limit of 8 has
         // been exceeded, to also avoid allocations for `indices`.
-        if var_values.is_array() {
+        if !var_values.spilled() {
             // `var_values` is stack-allocated. `indices` isn't used yet. Do a
             // direct linear search of `var_values`.
             if let Some(idx) = var_values.iter().position(|&k| k == kind) {
@@ -395,7 +395,7 @@ impl<'cx, 'gcx, 'tcx> Canonicalizer<'cx, 'gcx, 'tcx> {
 
                 // If `var_values` has become big enough to be heap-allocated,
                 // fill up `indices` to facilitate subsequent lookups.
-                if !var_values.is_array() {
+                if var_values.spilled() {
                     assert!(indices.is_empty());
                     *indices =
                         var_values.iter()

src/librustc/infer/canonical/mod.rs

@@ -33,7 +33,7 @@
 
 use infer::{InferCtxt, RegionVariableOrigin, TypeVariableOrigin};
 use rustc_data_structures::indexed_vec::IndexVec;
-use rustc_data_structures::small_vec::SmallVec;
+use smallvec::SmallVec;
 use rustc_data_structures::sync::Lrc;
 use serialize::UseSpecializedDecodable;
 use std::ops::Index;

src/librustc/lib.rs

@@ -108,6 +108,9 @@ extern crate rustc_apfloat;
 extern crate byteorder;
 extern crate backtrace;
 
+#[macro_use]
+extern crate smallvec;
+
 // Note that librustc doesn't actually depend on these crates, see the note in
 // `Cargo.toml` for this crate about why these are here.
 #[allow(unused_extern_crates)]

src/librustc/mir/mod.rs

@@ -24,7 +24,7 @@ use rustc_apfloat::Float;
 use rustc_data_structures::graph::dominators::{dominators, Dominators};
 use rustc_data_structures::graph::{self, GraphPredecessors, GraphSuccessors};
 use rustc_data_structures::indexed_vec::{Idx, IndexVec};
-use rustc_data_structures::small_vec::SmallVec;
+use smallvec::SmallVec;
 use rustc_data_structures::sync::Lrc;
 use rustc_data_structures::sync::ReadGuard;
 use rustc_serialize as serialize;

src/librustc/traits/query/dropck_outlives.rs

@@ -10,7 +10,7 @@
 
 use infer::at::At;
 use infer::InferOk;
-use rustc_data_structures::small_vec::SmallVec;
+use smallvec::SmallVec;
 use std::iter::FromIterator;
 use syntax::source_map::Span;
 use ty::subst::Kind;

src/librustc/traits/query/evaluate_obligation.rs

@@ -9,7 +9,7 @@
 // except according to those terms.
 
 use infer::InferCtxt;
-use rustc_data_structures::small_vec::SmallVec;
+use smallvec::SmallVec;
 use traits::{EvaluationResult, PredicateObligation, SelectionContext,
              TraitQueryMode, OverflowError};
 

src/librustc/traits/query/normalize.rs

@@ -15,7 +15,7 @@
 use infer::at::At;
 use infer::{InferCtxt, InferOk};
 use mir::interpret::{ConstValue, GlobalId};
-use rustc_data_structures::small_vec::SmallVec;
+use smallvec::SmallVec;
 use traits::project::Normalized;
 use traits::{Obligation, ObligationCause, PredicateObligation, Reveal};
 use ty::fold::{TypeFoldable, TypeFolder};

src/librustc/traits/query/outlives_bounds.rs

@@ -11,7 +11,7 @@
 use infer::InferCtxt;
 use syntax::ast;
 use syntax::source_map::Span;
-use rustc_data_structures::small_vec::SmallVec;
+use smallvec::SmallVec;
 use traits::{FulfillmentContext, ObligationCause, TraitEngine, TraitEngineExt};
 use traits::query::NoSolution;
 use ty::{self, Ty, TyCtxt};

src/librustc/traits/query/type_op/mod.rs

@@ -11,7 +11,7 @@
 use infer::canonical::{Canonical, Canonicalized, CanonicalizedQueryResult, QueryRegionConstraint,
                        QueryResult};
 use infer::{InferCtxt, InferOk};
-use rustc_data_structures::small_vec::SmallVec;
+use smallvec::SmallVec;
 use std::fmt;
 use std::rc::Rc;
 use traits::query::Fallible;

src/librustc/ty/inhabitedness/def_id_forest.rs

@@ -9,7 +9,7 @@
 // except according to those terms.
 
 use std::mem;
-use rustc_data_structures::small_vec::SmallVec;
+use smallvec::SmallVec;
 use syntax::ast::CRATE_NODE_ID;
 use ty::context::TyCtxt;
 use ty::{DefId, DefIdTree};
@@ -83,14 +83,14 @@ impl<'a, 'gcx, 'tcx> DefIdForest {
         let mut next_ret = SmallVec::new();
         let mut old_ret: SmallVec<[DefId; 1]> = SmallVec::new();
         for next_forest in iter {
-            for id in ret.root_ids.drain(..) {
+            for id in ret.root_ids.drain() {
                 if next_forest.contains(tcx, id) {
                     next_ret.push(id);
                 } else {
                     old_ret.push(id);
                 }
             }
-            ret.root_ids.extend(old_ret.drain(..));
+            ret.root_ids.extend(old_ret.drain());
 
             for id in next_forest.root_ids {
                 if ret.contains(tcx, id) {
@@ -99,7 +99,7 @@ impl<'a, 'gcx, 'tcx> DefIdForest {
             }
 
             mem::swap(&mut next_ret, &mut ret.root_ids);
-            next_ret.drain(..);
+            next_ret.drain();
         }
         ret
     }
@@ -112,7 +112,7 @@ impl<'a, 'gcx, 'tcx> DefIdForest {
         let mut ret = DefIdForest::empty();
         let mut next_ret = SmallVec::new();
         for next_forest in iter {
-            for id in ret.root_ids.drain(..) {
+            for id in ret.root_ids.drain() {
                 if !next_forest.contains(tcx, id) {
                     next_ret.push(id);
                 }
@@ -125,7 +125,7 @@ impl<'a, 'gcx, 'tcx> DefIdForest {
             }
 
             mem::swap(&mut next_ret, &mut ret.root_ids);
-            next_ret.drain(..);
+            next_ret.drain();
         }
         ret
     }

src/librustc/ty/mod.rs

@@ -55,7 +55,7 @@ use syntax::ext::hygiene::Mark;
 use syntax::symbol::{keywords, Symbol, LocalInternedString, InternedString};
 use syntax_pos::{DUMMY_SP, Span};
 
-use rustc_data_structures::accumulate_vec::IntoIter as AccIntoIter;
+use smallvec;
 use rustc_data_structures::stable_hasher::{StableHasher, StableHasherResult,
                                            HashStable};
 
@@ -2382,7 +2382,7 @@ impl<'tcx> TyS<'tcx> {
     /// Iterator that walks the immediate children of `self`.  Hence
     /// `Foo<Bar<i32>, u32>` yields the sequence `[Bar<i32>, u32]`
     /// (but not `i32`, like `walk`).
-    pub fn walk_shallow(&'tcx self) -> AccIntoIter<walk::TypeWalkerArray<'tcx>> {
+    pub fn walk_shallow(&'tcx self) -> smallvec::IntoIter<walk::TypeWalkerArray<'tcx>> {
         walk::walk_shallow(self)
     }
 

src/librustc/ty/walk.rs

@@ -13,8 +13,7 @@
 
 use mir::interpret::ConstValue;
 use ty::{self, Ty};
-use rustc_data_structures::small_vec::SmallVec;
-use rustc_data_structures::accumulate_vec::IntoIter as AccIntoIter;
+use smallvec::{self, SmallVec};
 
 // The TypeWalker's stack is hot enough that it's worth going to some effort to
 // avoid heap allocations.
@@ -28,7 +27,7 @@ pub struct TypeWalker<'tcx> {
 
 impl<'tcx> TypeWalker<'tcx> {
     pub fn new(ty: Ty<'tcx>) -> TypeWalker<'tcx> {
-        TypeWalker { stack: SmallVec::one(ty), last_subtree: 1, }
+        TypeWalker { stack: smallvec![ty], last_subtree: 1, }
     }
 
     /// Skips the subtree of types corresponding to the last type
@@ -67,7 +66,7 @@ impl<'tcx> Iterator for TypeWalker<'tcx> {
     }
 }
 
-pub fn walk_shallow<'tcx>(ty: Ty<'tcx>) -> AccIntoIter<TypeWalkerArray<'tcx>> {
+pub fn walk_shallow<'tcx>(ty: Ty<'tcx>) -> smallvec::IntoIter<TypeWalkerArray<'tcx>> {
     let mut stack = SmallVec::new();
     push_subtypes(&mut stack, ty);
     stack.into_iter()

src/librustc_allocator/Cargo.toml

@@ -16,3 +16,4 @@ rustc_target = { path = "../librustc_target" }
 syntax = { path = "../libsyntax" }
 syntax_pos = { path = "../libsyntax_pos" }
 log = "0.4"
+smallvec = { version = "0.6.5", features = ["union"] }