Auto merge of #119192 - michaelwoerister:mcp533-push, r=cjgillot

Replace a number of FxHashMaps/Sets with stable-iteration-order alternatives

This PR replaces almost all of the remaining `FxHashMap`s in query results with either `FxIndexMap` or `UnordMap`. The only case that is missing is the `EffectiveVisibilities` struct which turned out to not be straightforward to transform. Once that is done too, we can remove the `HashStable` implementation from `HashMap`.

The first commit adds the `StableCompare` trait which is a companion trait to `StableOrd`. Some types like `Symbol` can be compared in a cross-session stable way, but their `Ord` implementation is not stable. In such cases, a `StableCompare` implementation can be provided to offer a lightweight way for stable sorting. The more heavyweight option is to sort via `ToStableHashKey`, but then sorting needs to have access to a stable hashing context and `ToStableHashKey` can also be expensive as in the case of `Symbol` where it has to allocate a `String`.

The rest of the commits are rather mechanical and don't overlap, so they are best reviewed individually.

Part of [MCP 533](https://github.com/rust-lang/compiler-team/issues/533).

compiler/rustc_middle/src/arena.rs

@@ -103,7 +103,7 @@ macro_rules! arena_types {
             [] dep_kind: rustc_middle::dep_graph::DepKindStruct<'tcx>,
 
             [decode] trait_impl_trait_tys:
-                rustc_data_structures::fx::FxHashMap<
+                rustc_data_structures::unord::UnordMap<
                     rustc_hir::def_id::DefId,
                     rustc_middle::ty::EarlyBinder<rustc_middle::ty::Ty<'tcx>>
                 >,

compiler/rustc_middle/src/middle/mod.rs

@@ -4,7 +4,7 @@ pub mod dependency_format;
 pub mod exported_symbols;
 pub mod lang_items;
 pub mod lib_features {
-    use rustc_data_structures::fx::FxHashMap;
+    use rustc_data_structures::unord::UnordMap;
     use rustc_span::{symbol::Symbol, Span};
 
     #[derive(Copy, Clone, Debug, PartialEq, Eq)]
@@ -16,15 +16,16 @@ pub mod lib_features {
 
     #[derive(HashStable, Debug, Default)]
     pub struct LibFeatures {
-        pub stability: FxHashMap<Symbol, (FeatureStability, Span)>,
+        pub stability: UnordMap<Symbol, (FeatureStability, Span)>,
     }
 
     impl LibFeatures {
-        pub fn to_vec(&self) -> Vec<(Symbol, FeatureStability)> {
-            let mut all_features: Vec<_> =
-                self.stability.iter().map(|(&sym, &(stab, _))| (sym, stab)).collect();
-            all_features.sort_unstable_by(|(a, _), (b, _)| a.as_str().cmp(b.as_str()));
-            all_features
+        pub fn to_sorted_vec(&self) -> Vec<(Symbol, FeatureStability)> {
+            self.stability
+                .to_sorted_stable_ord()
+                .iter()
+                .map(|(&sym, &(stab, _))| (sym, stab))
+                .collect()
         }
     }
 }

compiler/rustc_middle/src/middle/region.rs

@@ -7,12 +7,11 @@
 //! [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/borrow_check.html
 
 use crate::ty::TyCtxt;
-use rustc_data_structures::fx::{FxHashMap, FxIndexMap};
-use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
+use rustc_data_structures::fx::FxIndexMap;
+use rustc_data_structures::unord::UnordMap;
 use rustc_hir as hir;
 use rustc_hir::{HirIdMap, Node};
 use rustc_macros::HashStable;
-use rustc_query_system::ich::StableHashingContext;
 use rustc_span::{Span, DUMMY_SP};
 
 use std::fmt;
@@ -205,7 +204,7 @@ impl Scope {
 pub type ScopeDepth = u32;
 
 /// The region scope tree encodes information about region relationships.
-#[derive(Default, Debug)]
+#[derive(Default, Debug, HashStable)]
 pub struct ScopeTree {
     /// If not empty, this body is the root of this region hierarchy.
     pub root_body: Option<hir::HirId>,
@@ -306,7 +305,7 @@ pub struct ScopeTree {
     /// The reason is that semantically, until the `box` expression returns,
     /// the values are still owned by their containing expressions. So
     /// we'll see that `&x`.
-    pub yield_in_scope: FxHashMap<Scope, Vec<YieldData>>,
+    pub yield_in_scope: UnordMap<Scope, Vec<YieldData>>,
 }
 
 /// Identifies the reason that a given expression is an rvalue candidate
@@ -404,23 +403,3 @@ impl ScopeTree {
         self.yield_in_scope.get(&scope).map(Deref::deref)
     }
 }
-
-impl<'a> HashStable<StableHashingContext<'a>> for ScopeTree {
-    fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
-        let ScopeTree {
-            root_body,
-            ref parent_map,
-            ref var_map,
-            ref destruction_scopes,
-            ref rvalue_candidates,
-            ref yield_in_scope,
-        } = *self;
-
-        root_body.hash_stable(hcx, hasher);
-        parent_map.hash_stable(hcx, hasher);
-        var_map.hash_stable(hcx, hasher);
-        destruction_scopes.hash_stable(hcx, hasher);
-        rvalue_candidates.hash_stable(hcx, hasher);
-        yield_in_scope.hash_stable(hcx, hasher);
-    }
-}

compiler/rustc_middle/src/middle/resolve_bound_vars.rs

@@ -2,7 +2,7 @@
 
 use crate::ty;
 
-use rustc_data_structures::fx::FxHashMap;
+use rustc_data_structures::fx::FxIndexMap;
 use rustc_errors::ErrorGuaranteed;
 use rustc_hir::def_id::DefId;
 use rustc_hir::{ItemLocalId, OwnerId};
@@ -51,7 +51,7 @@ pub enum ObjectLifetimeDefault {
 pub struct ResolveBoundVars {
     /// Maps from every use of a named (not anonymous) lifetime to a
     /// `Region` describing how that region is bound
-    pub defs: FxHashMap<OwnerId, FxHashMap<ItemLocalId, ResolvedArg>>,
+    pub defs: FxIndexMap<OwnerId, FxIndexMap<ItemLocalId, ResolvedArg>>,
 
-    pub late_bound_vars: FxHashMap<OwnerId, FxHashMap<ItemLocalId, Vec<ty::BoundVariableKind>>>,
+    pub late_bound_vars: FxIndexMap<OwnerId, FxIndexMap<ItemLocalId, Vec<ty::BoundVariableKind>>>,
 }

compiler/rustc_middle/src/middle/stability.rs

@@ -8,11 +8,11 @@ use rustc_ast::NodeId;
 use rustc_attr::{
     self as attr, ConstStability, DefaultBodyStability, DeprecatedSince, Deprecation, Stability,
 };
-use rustc_data_structures::fx::FxHashMap;
+use rustc_data_structures::unord::UnordMap;
 use rustc_errors::{Applicability, Diagnostic};
 use rustc_feature::GateIssue;
 use rustc_hir::def::DefKind;
-use rustc_hir::def_id::{DefId, LocalDefId};
+use rustc_hir::def_id::{DefId, LocalDefId, LocalDefIdMap};
 use rustc_hir::{self as hir, HirId};
 use rustc_middle::ty::print::with_no_trimmed_paths;
 use rustc_session::lint::builtin::{DEPRECATED, DEPRECATED_IN_FUTURE, SOFT_UNSTABLE};
@@ -61,10 +61,10 @@ impl DeprecationEntry {
 pub struct Index {
     /// This is mostly a cache, except the stabilities of local items
     /// are filled by the annotator.
-    pub stab_map: FxHashMap<LocalDefId, Stability>,
-    pub const_stab_map: FxHashMap<LocalDefId, ConstStability>,
-    pub default_body_stab_map: FxHashMap<LocalDefId, DefaultBodyStability>,
-    pub depr_map: FxHashMap<LocalDefId, DeprecationEntry>,
+    pub stab_map: LocalDefIdMap<Stability>,
+    pub const_stab_map: LocalDefIdMap<ConstStability>,
+    pub default_body_stab_map: LocalDefIdMap<DefaultBodyStability>,
+    pub depr_map: LocalDefIdMap<DeprecationEntry>,
     /// Mapping from feature name to feature name based on the `implied_by` field of `#[unstable]`
     /// attributes. If a `#[unstable(feature = "implier", implied_by = "impliee")]` attribute
     /// exists, then this map will have a `impliee -> implier` entry.
@@ -77,7 +77,7 @@ pub struct Index {
     /// to know that the feature implies another feature. If it were reversed, and the `#[stable]`
     /// attribute had an `implies` meta item, then a map would be necessary when avoiding a "use of
     /// unstable feature" error for a feature that was implied.
-    pub implications: FxHashMap<Symbol, Symbol>,
+    pub implications: UnordMap<Symbol, Symbol>,
 }
 
 impl Index {

compiler/rustc_middle/src/query/mod.rs

@@ -57,11 +57,11 @@ use rustc_ast as ast;
 use rustc_ast::expand::{allocator::AllocatorKind, StrippedCfgItem};
 use rustc_attr as attr;
 use rustc_data_structures::fingerprint::Fingerprint;
-use rustc_data_structures::fx::{FxHashMap, FxIndexMap, FxIndexSet};
+use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_data_structures::steal::Steal;
 use rustc_data_structures::svh::Svh;
 use rustc_data_structures::sync::Lrc;
-use rustc_data_structures::unord::UnordSet;
+use rustc_data_structures::unord::{UnordMap, UnordSet};
 use rustc_errors::ErrorGuaranteed;
 use rustc_hir as hir;
 use rustc_hir::def::{DefKind, DocLinkResMap};
@@ -264,7 +264,7 @@ rustc_queries! {
     }
 
     query collect_return_position_impl_trait_in_trait_tys(key: DefId)
-        -> Result<&'tcx FxHashMap<DefId, ty::EarlyBinder<Ty<'tcx>>>, ErrorGuaranteed>
+        -> Result<&'tcx DefIdMap<ty::EarlyBinder<Ty<'tcx>>>, ErrorGuaranteed>
     {
         desc { "comparing an impl and trait method signature, inferring any hidden `impl Trait` types in the process" }
         cache_on_disk_if { key.is_local() }
@@ -611,7 +611,7 @@ rustc_queries! {
         desc { "erasing regions from `{}`", ty }
     }
 
-    query wasm_import_module_map(_: CrateNum) -> &'tcx FxHashMap<DefId, String> {
+    query wasm_import_module_map(_: CrateNum) -> &'tcx DefIdMap<String> {
         arena_cache
         desc { "getting wasm import module map" }
     }
@@ -1537,7 +1537,7 @@ rustc_queries! {
     /// added or removed in any upstream crate. Instead use the narrower
     /// `upstream_monomorphizations_for`, `upstream_drop_glue_for`, or, even
     /// better, `Instance::upstream_monomorphization()`.
-    query upstream_monomorphizations(_: ()) -> &'tcx DefIdMap<FxHashMap<GenericArgsRef<'tcx>, CrateNum>> {
+    query upstream_monomorphizations(_: ()) -> &'tcx DefIdMap<UnordMap<GenericArgsRef<'tcx>, CrateNum>> {
         arena_cache
         desc { "collecting available upstream monomorphizations" }
     }
@@ -1550,7 +1550,7 @@ rustc_queries! {
     /// You likely want to call `Instance::upstream_monomorphization()`
     /// instead of invoking this query directly.
     query upstream_monomorphizations_for(def_id: DefId)
-        -> Option<&'tcx FxHashMap<GenericArgsRef<'tcx>, CrateNum>>
+        -> Option<&'tcx UnordMap<GenericArgsRef<'tcx>, CrateNum>>
     {
         desc { |tcx|
             "collecting available upstream monomorphizations for `{}`",
@@ -1662,7 +1662,7 @@ rustc_queries! {
         desc { "resolving lifetimes" }
     }
     query named_variable_map(_: hir::OwnerId) ->
-        Option<&'tcx FxHashMap<ItemLocalId, ResolvedArg>> {
+        Option<&'tcx FxIndexMap<ItemLocalId, ResolvedArg>> {
         desc { "looking up a named region" }
     }
     query is_late_bound_map(_: hir::OwnerId) -> Option<&'tcx FxIndexSet<ItemLocalId>> {
@@ -1678,7 +1678,7 @@ rustc_queries! {
         separate_provide_extern
     }
     query late_bound_vars_map(_: hir::OwnerId)
-        -> Option<&'tcx FxHashMap<ItemLocalId, Vec<ty::BoundVariableKind>>> {
+        -> Option<&'tcx FxIndexMap<ItemLocalId, Vec<ty::BoundVariableKind>>> {
         desc { "looking up late bound vars" }
     }
 
@@ -1734,7 +1734,7 @@ rustc_queries! {
         separate_provide_extern
         arena_cache
     }
-    query stability_implications(_: CrateNum) -> &'tcx FxHashMap<Symbol, Symbol> {
+    query stability_implications(_: CrateNum) -> &'tcx UnordMap<Symbol, Symbol> {
         arena_cache
         desc { "calculating the implications between `#[unstable]` features defined in a crate" }
         separate_provide_extern
@@ -1786,7 +1786,7 @@ rustc_queries! {
     }
     /// Collects the "trimmed", shortest accessible paths to all items for diagnostics.
     /// See the [provider docs](`rustc_middle::ty::print::trimmed_def_paths`) for more info.
-    query trimmed_def_paths(_: ()) -> &'tcx FxHashMap<DefId, Symbol> {
+    query trimmed_def_paths(_: ()) -> &'tcx DefIdMap<Symbol> {
         arena_cache
         desc { "calculating trimmed def paths" }
     }
@@ -2077,7 +2077,7 @@ rustc_queries! {
         desc { "computing autoderef types for `{}`", goal.value.value }
     }
 
-    query supported_target_features(_: CrateNum) -> &'tcx FxHashMap<String, Option<Symbol>> {
+    query supported_target_features(_: CrateNum) -> &'tcx UnordMap<String, Option<Symbol>> {
         arena_cache
         eval_always
         desc { "looking up supported target features" }

compiler/rustc_middle/src/query/on_disk_cache.rs

@@ -2,7 +2,7 @@ use rustc_data_structures::fx::{FxHashMap, FxIndexSet};
 use rustc_data_structures::memmap::Mmap;
 use rustc_data_structures::sync::{HashMapExt, Lock, Lrc, RwLock};
 use rustc_data_structures::unhash::UnhashMap;
-use rustc_data_structures::unord::UnordSet;
+use rustc_data_structures::unord::{UnordMap, UnordSet};
 use rustc_hir::def_id::{CrateNum, DefId, DefIndex, LocalDefId, StableCrateId, LOCAL_CRATE};
 use rustc_hir::definitions::DefPathHash;
 use rustc_index::{Idx, IndexVec};
@@ -764,7 +764,7 @@ impl<'a, 'tcx> Decodable<CacheDecoder<'a, 'tcx>> for &'tcx UnordSet<LocalDefId>
 }
 
 impl<'a, 'tcx> Decodable<CacheDecoder<'a, 'tcx>>
-    for &'tcx FxHashMap<DefId, ty::EarlyBinder<Ty<'tcx>>>
+    for &'tcx UnordMap<DefId, ty::EarlyBinder<Ty<'tcx>>>
 {
     #[inline]
     fn decode(d: &mut CacheDecoder<'a, 'tcx>) -> Self {

compiler/rustc_middle/src/ty/mod.rs

@@ -38,6 +38,7 @@ use rustc_data_structures::intern::Interned;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_data_structures::steal::Steal;
 use rustc_data_structures::tagged_ptr::CopyTaggedPtr;
+use rustc_data_structures::unord::UnordMap;
 use rustc_errors::{DiagnosticBuilder, ErrorGuaranteed, StashKey};
 use rustc_hir as hir;
 use rustc_hir::def::{CtorKind, CtorOf, DefKind, DocLinkResMap, LifetimeRes, Res};
@@ -655,7 +656,7 @@ pub struct CratePredicatesMap<'tcx> {
     /// For each struct with outlive bounds, maps to a vector of the
     /// predicate of its outlive bounds. If an item has no outlives
     /// bounds, it will have no entry.
-    pub predicates: FxHashMap<DefId, &'tcx [(Clause<'tcx>, Span)]>,
+    pub predicates: DefIdMap<&'tcx [(Clause<'tcx>, Span)]>,
 }
 
 impl<'tcx> Clause<'tcx> {
@@ -2658,7 +2659,7 @@ pub fn provide(providers: &mut Providers) {
 #[derive(Clone, Debug, Default, HashStable)]
 pub struct CrateInherentImpls {
     pub inherent_impls: LocalDefIdMap<Vec<DefId>>,
-    pub incoherent_impls: FxHashMap<SimplifiedType, Vec<LocalDefId>>,
+    pub incoherent_impls: UnordMap<SimplifiedType, Vec<LocalDefId>>,
 }
 
 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, HashStable)]

compiler/rustc_middle/src/ty/parameterized.rs

@@ -1,6 +1,7 @@
-use rustc_data_structures::fx::FxHashMap;
+use rustc_data_structures::unord::UnordMap;
 use rustc_hir::def_id::DefIndex;
 use rustc_index::{Idx, IndexVec};
+use std::hash::Hash;
 
 use crate::ty;
 
@@ -24,8 +25,8 @@ impl<I: Idx + 'static, T: ParameterizedOverTcx> ParameterizedOverTcx for IndexVe
     type Value<'tcx> = IndexVec<I, T::Value<'tcx>>;
 }
 
-impl<I: 'static, T: ParameterizedOverTcx> ParameterizedOverTcx for FxHashMap<I, T> {
-    type Value<'tcx> = FxHashMap<I, T::Value<'tcx>>;
+impl<I: Hash + Eq + 'static, T: ParameterizedOverTcx> ParameterizedOverTcx for UnordMap<I, T> {
+    type Value<'tcx> = UnordMap<I, T::Value<'tcx>>;
 }
 
 impl<T: ParameterizedOverTcx> ParameterizedOverTcx for ty::Binder<'static, T> {

compiler/rustc_middle/src/ty/print/pretty.rs

@@ -12,7 +12,7 @@ use rustc_apfloat::Float;
 use rustc_data_structures::fx::{FxHashMap, FxIndexMap};
 use rustc_hir as hir;
 use rustc_hir::def::{self, CtorKind, DefKind, Namespace};
-use rustc_hir::def_id::{DefIdSet, ModDefId, CRATE_DEF_ID, LOCAL_CRATE};
+use rustc_hir::def_id::{DefIdMap, DefIdSet, ModDefId, CRATE_DEF_ID, LOCAL_CRATE};
 use rustc_hir::definitions::{DefKey, DefPathDataName};
 use rustc_hir::LangItem;
 use rustc_session::config::TrimmedDefPaths;
@@ -3049,8 +3049,8 @@ fn for_each_def(tcx: TyCtxt<'_>, mut collect_fn: impl for<'b> FnMut(&'b Ident, N
 ///
 /// See also [`DelayDm`](rustc_error_messages::DelayDm) and [`with_no_trimmed_paths!`].
 // this is pub to be able to intra-doc-link it
-pub fn trimmed_def_paths(tcx: TyCtxt<'_>, (): ()) -> FxHashMap<DefId, Symbol> {
-    let mut map: FxHashMap<DefId, Symbol> = FxHashMap::default();
+pub fn trimmed_def_paths(tcx: TyCtxt<'_>, (): ()) -> DefIdMap<Symbol> {
+    let mut map: DefIdMap<Symbol> = Default::default();
 
     if let TrimmedDefPaths::GoodPath = tcx.sess.opts.trimmed_def_paths {
         // Trimming paths is expensive and not optimized, since we expect it to only be used for error reporting.

compiler/rustc_middle/src/ty/typeck_results.rs

@@ -527,7 +527,7 @@ impl<'a, V> LocalTableInContext<'a, V> {
     }
 
     pub fn items_in_stable_order(&self) -> Vec<(ItemLocalId, &'a V)> {
-        self.data.to_sorted_stable_ord()
+        self.data.items().map(|(&k, v)| (k, v)).into_sorted_stable_ord_by_key(|(k, _)| k)
     }
 }