Auto merge of #69808 - cjgillot:vtbl, r=<try>

Avoid duplicating code for each query

There are at the moment roughly 170 queries in librustc.
The way `ty::query` is structured, a lot of code is duplicated for each query.
I suspect this to be responsible for a part of librustc'c compile time.

The first part of this PR reduces the amount of code generic on the query,
replacing it by code generic on the key-value types. I can split it out if needed.

In a second part, the non-inlined methods in the `QueryAccessors` and `QueryDescription` traits
are made into a virtual dispatch table. This allows to reduce even more the number of generated
functions.

This allows to save 1.5s on check build, and 10% on the size of the librustc.rlib.
(Attributed roughly half and half).
My computer is not good enough to measure properly compiling time.
I have no idea of the effect on performance. A perf run may be required.

cc #65031

Author: bors

src/librustc/ty/query/caches.rs

@@ -1,82 +1,93 @@
 use crate::dep_graph::DepNodeIndex;
-use crate::ty::query::config::QueryAccessors;
 use crate::ty::query::plumbing::{QueryLookup, QueryState, QueryStateShard};
-use crate::ty::TyCtxt;
 
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sharded::Sharded;
 use std::default::Default;
 use std::hash::Hash;
+use std::marker::PhantomData;
 
 pub(crate) trait CacheSelector<K, V> {
-    type Cache: QueryCache<K, V>;
+    type Cache: QueryCache<Key = K, Value = V>;
 }
 
-pub(crate) trait QueryCache<K, V>: Default {
+pub(crate) trait QueryCache: Default {
+    type Key;
+    type Value;
     type Sharded: Default;
 
     /// Checks if the query is already computed and in the cache.
     /// It returns the shard index and a lock guard to the shard,
     /// which will be used if the query is not in the cache and we need
     /// to compute it.
-    fn lookup<'tcx, R, GetCache, OnHit, OnMiss, Q>(
+    fn lookup<'tcx, R, GetCache, OnHit, OnMiss>(
         &self,
-        state: &'tcx QueryState<'tcx, Q>,
+        state: &'tcx QueryState<'tcx, Self>,
         get_cache: GetCache,
-        key: K,
+        key: Self::Key,
         // `on_hit` can be called while holding a lock to the query state shard.
         on_hit: OnHit,
         on_miss: OnMiss,
     ) -> R
     where
-        Q: QueryAccessors<'tcx>,
-        GetCache: for<'a> Fn(&'a mut QueryStateShard<'tcx, Q>) -> &'a mut Self::Sharded,
-        OnHit: FnOnce(&V, DepNodeIndex) -> R,
-        OnMiss: FnOnce(K, QueryLookup<'tcx, Q>) -> R;
+        GetCache: for<'a> Fn(
+            &'a mut QueryStateShard<'tcx, Self::Key, Self::Sharded>,
+        ) -> &'a mut Self::Sharded,
+        OnHit: FnOnce(&Self::Value, DepNodeIndex) -> R,
+        OnMiss: FnOnce(Self::Key, QueryLookup<'tcx, Self::Key, Self::Sharded>) -> R;
 
     fn complete(
         &self,
-        tcx: TyCtxt<'tcx>,
         lock_sharded_storage: &mut Self::Sharded,
-        key: K,
-        value: V,
+        key: Self::Key,
+        value: Self::Value,
         index: DepNodeIndex,
     );
 
     fn iter<R, L>(
         &self,
         shards: &Sharded<L>,
         get_shard: impl Fn(&mut L) -> &mut Self::Sharded,
-        f: impl for<'a> FnOnce(Box<dyn Iterator<Item = (&'a K, &'a V, DepNodeIndex)> + 'a>) -> R,
+        f: impl for<'a> FnOnce(
+            Box<dyn Iterator<Item = (&'a Self::Key, &'a Self::Value, DepNodeIndex)> + 'a>,
+        ) -> R,
     ) -> R;
 }
 
 pub struct DefaultCacheSelector;
 
 impl<K: Eq + Hash, V: Clone> CacheSelector<K, V> for DefaultCacheSelector {
-    type Cache = DefaultCache;
+    type Cache = DefaultCache<K, V>;
 }
 
-#[derive(Default)]
-pub struct DefaultCache;
+pub struct DefaultCache<K, V>(PhantomData<(K, V)>);
 
-impl<K: Eq + Hash, V: Clone> QueryCache<K, V> for DefaultCache {
+impl<K, V> Default for DefaultCache<K, V> {
+    fn default() -> Self {
+        DefaultCache(PhantomData)
+    }
+}
+
+impl<K: Eq + Hash, V: Clone> QueryCache for DefaultCache<K, V> {
+    type Key = K;
+    type Value = V;
     type Sharded = FxHashMap<K, (V, DepNodeIndex)>;
 
     #[inline(always)]
-    fn lookup<'tcx, R, GetCache, OnHit, OnMiss, Q>(
+    fn lookup<'tcx, R, GetCache, OnHit, OnMiss>(
         &self,
-        state: &'tcx QueryState<'tcx, Q>,
+        state: &'tcx QueryState<'tcx, Self>,
         get_cache: GetCache,
         key: K,
+        // `on_hit` can be called while holding a lock to the query state shard.
         on_hit: OnHit,
         on_miss: OnMiss,
     ) -> R
     where
-        Q: QueryAccessors<'tcx>,
-        GetCache: for<'a> Fn(&'a mut QueryStateShard<'tcx, Q>) -> &'a mut Self::Sharded,
+        GetCache:
+            for<'a> Fn(&'a mut QueryStateShard<'tcx, K, Self::Sharded>) -> &'a mut Self::Sharded,
         OnHit: FnOnce(&V, DepNodeIndex) -> R,
-        OnMiss: FnOnce(K, QueryLookup<'tcx, Q>) -> R,
+        OnMiss: FnOnce(K, QueryLookup<'tcx, K, Self::Sharded>) -> R,
     {
         let mut lookup = state.get_lookup(&key);
         let lock = &mut *lookup.lock;
@@ -89,7 +100,6 @@ impl<K: Eq + Hash, V: Clone> QueryCache<K, V> for DefaultCache {
     #[inline]
     fn complete(
         &self,
-        _: TyCtxt<'tcx>,
         lock_sharded_storage: &mut Self::Sharded,
         key: K,
         value: V,

src/librustc/ty/query/config.rs

@@ -3,7 +3,7 @@ use crate::dep_graph::{DepKind, DepNode};
 use crate::ty::query::caches::QueryCache;
 use crate::ty::query::plumbing::CycleError;
 use crate::ty::query::queries;
-use crate::ty::query::{Query, QueryState};
+use crate::ty::query::QueryState;
 use crate::ty::TyCtxt;
 use rustc_data_structures::profiling::ProfileCategory;
 use rustc_hir::def_id::{CrateNum, DefId};
@@ -26,23 +26,65 @@ pub trait QueryConfig<'tcx> {
     type Value: Clone;
 }
 
+pub(crate) struct QueryVtable<'tcx, K, V> {
+    pub anon: bool,
+    pub dep_kind: DepKind,
+    pub eval_always: bool,
+    pub name: &'static str,
+
+    // Don't use this method to compute query results, instead use the methods on TyCtxt
+    pub compute: fn(TyCtxt<'tcx>, K) -> V,
+
+    pub hash_result: fn(&mut StableHashingContext<'_>, &V) -> Option<Fingerprint>,
+    pub handle_cycle_error: fn(TyCtxt<'tcx>, CycleError<'tcx>) -> V,
+    pub cache_on_disk: fn(TyCtxt<'tcx>, K, Option<&V>) -> bool,
+    pub try_load_from_disk: fn(TyCtxt<'tcx>, SerializedDepNodeIndex) -> Option<V>,
+}
+
+impl<'tcx, K, V> QueryVtable<'tcx, K, V> {
+    pub(crate) fn compute(&self, tcx: TyCtxt<'tcx>, key: K) -> V {
+        (self.compute)(tcx, key)
+    }
+
+    pub(crate) fn hash_result(
+        &self,
+        hcx: &mut StableHashingContext<'_>,
+        value: &V,
+    ) -> Option<Fingerprint> {
+        (self.hash_result)(hcx, value)
+    }
+
+    pub(crate) fn handle_cycle_error(&self, tcx: TyCtxt<'tcx>, error: CycleError<'tcx>) -> V {
+        (self.handle_cycle_error)(tcx, error)
+    }
+
+    pub(crate) fn cache_on_disk(&self, tcx: TyCtxt<'tcx>, key: K, value: Option<&V>) -> bool {
+        (self.cache_on_disk)(tcx, key, value)
+    }
+
+    pub(crate) fn try_load_from_disk(
+        &self,
+        tcx: TyCtxt<'tcx>,
+        index: SerializedDepNodeIndex,
+    ) -> Option<V> {
+        (self.try_load_from_disk)(tcx, index)
+    }
+}
+
 pub(crate) trait QueryAccessors<'tcx>: QueryConfig<'tcx> {
     const ANON: bool;
     const EVAL_ALWAYS: bool;
+    const DEP_KIND: DepKind;
 
-    type Cache: QueryCache<Self::Key, Self::Value>;
-
-    fn query(key: Self::Key) -> Query<'tcx>;
+    type Cache: QueryCache<Key = Self::Key, Value = Self::Value>;
 
     // Don't use this method to access query results, instead use the methods on TyCtxt
-    fn query_state<'a>(tcx: TyCtxt<'tcx>) -> &'a QueryState<'tcx, Self>;
+    fn query_state<'a>(tcx: TyCtxt<'tcx>) -> &'a QueryState<'tcx, Self::Cache>;
 
     fn to_dep_node(tcx: TyCtxt<'tcx>, key: &Self::Key) -> DepNode;
 
-    fn dep_kind() -> DepKind;
-
     // Don't use this method to compute query results, instead use the methods on TyCtxt
-    fn compute(tcx: TyCtxt<'tcx>, key: Self::Key) -> Self::Value;
+    const COMPUTE_FN: fn(TyCtxt<'tcx>, Self::Key) -> Self::Value;
 
     fn hash_result(hcx: &mut StableHashingContext<'_>, result: &Self::Value)
     -> Option<Fingerprint>;
@@ -61,12 +103,21 @@ pub(crate) trait QueryDescription<'tcx>: QueryAccessors<'tcx> {
     fn try_load_from_disk(_: TyCtxt<'tcx>, _: SerializedDepNodeIndex) -> Option<Self::Value> {
         bug!("QueryDescription::load_from_disk() called for an unsupported query.")
     }
+
+    const VTABLE: QueryVtable<'tcx, Self::Key, Self::Value> = QueryVtable {
+        anon: Self::ANON,
+        dep_kind: Self::DEP_KIND,
+        eval_always: Self::EVAL_ALWAYS,
+        name: Self::NAME,
+        compute: Self::COMPUTE_FN,
+        hash_result: Self::hash_result,
+        handle_cycle_error: Self::handle_cycle_error,
+        cache_on_disk: Self::cache_on_disk,
+        try_load_from_disk: Self::try_load_from_disk,
+    };
 }
 
-impl<'tcx, M: QueryAccessors<'tcx, Key = DefId>> QueryDescription<'tcx> for M
-where
-    <M as QueryAccessors<'tcx>>::Cache: QueryCache<DefId, <M as QueryConfig<'tcx>>::Value>,
-{
+impl<'tcx, M: QueryAccessors<'tcx, Key = DefId>> QueryDescription<'tcx> for M {
     default fn describe(tcx: TyCtxt<'_>, def_id: DefId) -> Cow<'static, str> {
         if !tcx.sess.verbose() {
             format!("processing `{}`", tcx.def_path_str(def_id)).into()

src/librustc/ty/query/mod.rs

@@ -54,7 +54,6 @@ use rustc_attr as attr;
 use rustc_span::symbol::Symbol;
 use rustc_span::{Span, DUMMY_SP};
 use std::borrow::Cow;
-use std::convert::TryFrom;
 use std::ops::Deref;
 use std::sync::Arc;
 

src/librustc/ty/query/on_disk_cache.rs

@@ -6,6 +6,7 @@ use crate::mir::{self, interpret};
 use crate::session::{CrateDisambiguator, Session};
 use crate::ty::codec::{self as ty_codec, TyDecoder, TyEncoder};
 use crate::ty::context::TyCtxt;
+use crate::ty::query::config::{QueryAccessors, QueryDescription, QueryVtable};
 use crate::ty::{self, Ty};
 use rustc_ast::ast::Ident;
 use rustc_data_structures::fx::FxHashMap;
@@ -205,8 +206,10 @@ impl<'sess> OnDiskCache<'sess> {
                 macro_rules! encode_queries {
                     ($($query:ident,)*) => {
                         $(
-                            encode_query_results::<ty::query::queries::$query<'_>, _>(
+                            encode_query_results(
                                 tcx,
+                                ty::query::queries::$query::query_state(tcx),
+                                &ty::query::queries::$query::VTABLE,
                                 enc,
                                 qri
                             )?;
@@ -1022,26 +1025,27 @@ impl<'a> SpecializedDecoder<IntEncodedWithFixedSize> for opaque::Decoder<'a> {
     }
 }
 
-fn encode_query_results<'a, 'tcx, Q, E>(
+fn encode_query_results<'a, 'tcx, C, E>(
     tcx: TyCtxt<'tcx>,
+    state: &'a super::plumbing::QueryState<'tcx, C>,
+    query: &QueryVtable<'tcx, C::Key, C::Value>,
     encoder: &mut CacheEncoder<'a, 'tcx, E>,
     query_result_index: &mut EncodedQueryResultIndex,
 ) -> Result<(), E::Error>
 where
-    Q: super::config::QueryDescription<'tcx, Value: Encodable>,
+    C: super::caches::QueryCache,
     E: 'a + TyEncoder,
+    C::Key: Clone,
+    C::Value: Encodable,
 {
-    let _timer = tcx
-        .sess
-        .prof
-        .extra_verbose_generic_activity("encode_query_results_for", ::std::any::type_name::<Q>());
+    let _timer =
+        tcx.sess.prof.extra_verbose_generic_activity("encode_query_results_for", query.name);
 
-    let state = Q::query_state(tcx);
     assert!(state.all_inactive());
 
     state.iter_results(|results| {
         for (key, value, dep_node) in results {
-            if Q::cache_on_disk(tcx, key.clone(), Some(&value)) {
+            if query.cache_on_disk(tcx, key.clone(), Some(&value)) {
                 let dep_node = SerializedDepNodeIndex::new(dep_node.index());
 
                 // Record position of the cache entry.