cache types during normalization

Cargo.lock

@@ -3435,6 +3435,7 @@ dependencies = [
 name = "rustc_data_structures"
 version = "0.0.0"
 dependencies = [
+ "arrayvec",
  "bitflags",
  "cfg-if",
  "crossbeam-utils 0.7.2",

compiler/rustc_data_structures/Cargo.toml

@@ -8,6 +8,7 @@ edition = "2018"
 doctest = false
 
 [dependencies]
+arrayvec = { version = "0.5.1", default-features = false }
 ena = "0.14"
 indexmap = "1.5.1"
 tracing = "0.1"

compiler/rustc_data_structures/src/lib.rs

@@ -87,25 +87,27 @@ pub mod sorted_map;
 pub mod stable_set;
 #[macro_use]
 pub mod stable_hasher;
+mod atomic_ref;
+pub mod fingerprint;
+pub mod profiling;
 pub mod sharded;
 pub mod stack;
 pub mod sync;
 pub mod thin_vec;
 pub mod tiny_list;
 pub mod transitive_relation;
-pub use ena::undo_log;
-pub use ena::unify;
-mod atomic_ref;
-pub mod fingerprint;
-pub mod profiling;
 pub mod vec_linked_list;
 pub mod work_queue;
 pub use atomic_ref::AtomicRef;
 pub mod frozen;
+pub mod mini_map;
 pub mod tagged_ptr;
 pub mod temp_dir;
 pub mod unhash;
 
+pub use ena::undo_log;
+pub use ena::unify;
+
 pub struct OnDrop<F: Fn()>(pub F);
 
 impl<F: Fn()> OnDrop<F> {

compiler/rustc_data_structures/src/mini_map.rs

@@ -0,0 +1,61 @@
+use crate::fx::FxHashMap;
+use arrayvec::ArrayVec;
+
+use std::hash::Hash;
+
+/// Small-storage-optimized implementation of a map
+/// made specifically for caching results.
+///
+/// Stores elements in a small array up to a certain length
+/// and switches to `HashMap` when that length is exceeded.
+pub enum MiniMap<K, V> {
+    Array(ArrayVec<[(K, V); 8]>),
+    Map(FxHashMap<K, V>),
+}
+
+impl<K: Eq + Hash, V> MiniMap<K, V> {
+    /// Creates an empty `MiniMap`.
+    pub fn new() -> Self {
+        MiniMap::Array(ArrayVec::new())
+    }
+
+    /// Inserts or updates value in the map.
+    pub fn insert(&mut self, key: K, value: V) {
+        match self {
+            MiniMap::Array(array) => {
+                for pair in array.iter_mut() {
+                    if pair.0 == key {
+                        pair.1 = value;
+                        return;
+                    }
+                }
+                if let Err(error) = array.try_push((key, value)) {
+                    let mut map: FxHashMap<K, V> = array.drain(..).collect();
+                    let (key, value) = error.element();
+                    map.insert(key, value);
+                    *self = MiniMap::Map(map);
+                }
+            }
+            MiniMap::Map(map) => {
+                map.insert(key, value);
+            }
+        }
+    }
+
+    /// Return value by key if any.
+    pub fn get(&self, key: &K) -> Option<&V> {
+        match self {
+            MiniMap::Array(array) => {
+                for pair in array {
+                    if pair.0 == *key {
+                        return Some(&pair.1);
+                    }
+                }
+                return None;
+            }
+            MiniMap::Map(map) => {
+                return map.get(key);
+            }
+        }
+    }
+}

compiler/rustc_index/Cargo.toml

@@ -8,6 +8,6 @@ edition = "2018"
 doctest = false
 
 [dependencies]
-arrayvec = "0.5.1"
+arrayvec = { version = "0.5.1", default-features = false }
 rustc_serialize = { path = "../rustc_serialize" }
 rustc_macros = { path = "../rustc_macros" }

compiler/rustc_infer/src/infer/combine.rs

@@ -31,13 +31,11 @@ use super::unify_key::replace_if_possible;
 use super::unify_key::{ConstVarValue, ConstVariableValue};
 use super::unify_key::{ConstVariableOrigin, ConstVariableOriginKind};
 use super::{InferCtxt, MiscVariable, TypeTrace};
-use arrayvec::ArrayVec;
-use rustc_data_structures::fx::FxHashMap;
-use std::hash::Hash;
 
 use crate::traits::{Obligation, PredicateObligations};
 
 use rustc_ast as ast;
+use rustc_data_structures::mini_map::MiniMap;
 use rustc_hir::def_id::DefId;
 use rustc_middle::traits::ObligationCause;
 use rustc_middle::ty::error::TypeError;
@@ -47,63 +45,6 @@ use rustc_middle::ty::{self, InferConst, ToPredicate, Ty, TyCtxt, TypeFoldable};
 use rustc_middle::ty::{IntType, UintType};
 use rustc_span::DUMMY_SP;
 
-/// Small-storage-optimized implementation of a map
-/// made specifically for caching results.
-///
-/// Stores elements in a small array up to a certain length
-/// and switches to `HashMap` when that length is exceeded.
-enum MiniMap<K, V> {
-    Array(ArrayVec<[(K, V); 8]>),
-    Map(FxHashMap<K, V>),
-}
-
-impl<K: Eq + Hash, V> MiniMap<K, V> {
-    /// Creates an empty `MiniMap`.
-    pub fn new() -> Self {
-        MiniMap::Array(ArrayVec::new())
-    }
-
-    /// Inserts or updates value in the map.
-    pub fn insert(&mut self, key: K, value: V) {
-        match self {
-            MiniMap::Array(array) => {
-                for pair in array.iter_mut() {
-                    if pair.0 == key {
-                        pair.1 = value;
-                        return;
-                    }
-                }
-                if let Err(error) = array.try_push((key, value)) {
-                    let mut map: FxHashMap<K, V> = array.drain(..).collect();
-                    let (key, value) = error.element();
-                    map.insert(key, value);
-                    *self = MiniMap::Map(map);
-                }
-            }
-            MiniMap::Map(map) => {
-                map.insert(key, value);
-            }
-        }
-    }
-
-    /// Return value by key if any.
-    pub fn get(&self, key: &K) -> Option<&V> {
-        match self {
-            MiniMap::Array(array) => {
-                for pair in array {
-                    if pair.0 == *key {
-                        return Some(&pair.1);
-                    }
-                }
-                return None;
-            }
-            MiniMap::Map(map) => {
-                return map.get(key);
-            }
-        }
-    }
-}
-
 #[derive(Clone)]
 pub struct CombineFields<'infcx, 'tcx> {
     pub infcx: &'infcx InferCtxt<'infcx, 'tcx>,

compiler/rustc_trait_selection/src/traits/query/normalize.rs

@@ -7,6 +7,7 @@ use crate::infer::canonical::OriginalQueryValues;
 use crate::infer::{InferCtxt, InferOk};
 use crate::traits::error_reporting::InferCtxtExt;
 use crate::traits::{Obligation, ObligationCause, PredicateObligation, Reveal};
+use rustc_data_structures::mini_map::MiniMap;
 use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_infer::traits::Normalized;
 use rustc_middle::ty::fold::{TypeFoldable, TypeFolder};
@@ -57,6 +58,7 @@ impl<'cx, 'tcx> AtExt<'tcx> for At<'cx, 'tcx> {
             param_env: self.param_env,
             obligations: vec![],
             error: false,
+            cache: MiniMap::new(),
             anon_depth: 0,
         };
 
@@ -85,6 +87,7 @@ struct QueryNormalizer<'cx, 'tcx> {
     cause: &'cx ObligationCause<'tcx>,
     param_env: ty::ParamEnv<'tcx>,
     obligations: Vec<PredicateObligation<'tcx>>,
+    cache: MiniMap<Ty<'tcx>, Ty<'tcx>>,
     error: bool,
     anon_depth: usize,
 }
@@ -99,8 +102,12 @@ impl<'cx, 'tcx> TypeFolder<'tcx> for QueryNormalizer<'cx, 'tcx> {
             return ty;
         }
 
+        if let Some(ty) = self.cache.get(&ty) {
+            return ty;
+        }
+
         let ty = ty.super_fold_with(self);
-        match *ty.kind() {
+        let res = (|| match *ty.kind() {
             ty::Opaque(def_id, substs) => {
                 // Only normalize `impl Trait` after type-checking, usually in codegen.
                 match self.param_env.reveal() {
@@ -197,7 +204,9 @@ impl<'cx, 'tcx> TypeFolder<'tcx> for QueryNormalizer<'cx, 'tcx> {
             }
 
             _ => ty,
-        }
+        })();
+        self.cache.insert(ty, res);
+        res
     }
 
     fn fold_const(&mut self, constant: &'tcx ty::Const<'tcx>) -> &'tcx ty::Const<'tcx> {