Auto merge of rust-lang#69808 - cjgillot:vtbl, r=pnkfelix

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 rust-lang#65031

Author: bors

src/librustc_macros/src/query.rs

@@ -365,7 +365,7 @@ fn add_query_description_impl(
             #[allow(unused_variables, unused_braces)]
             fn cache_on_disk(
                 #tcx: TyCtxt<'tcx>,
-                #key: Self::Key,
+                #key: &Self::Key,
                 #value: Option<&Self::Value>
             ) -> bool {
                 #expr
@@ -441,7 +441,7 @@ pub fn rustc_queries(input: TokenStream) -> TokenStream {
                                             .unwrap_or(false));
 
                             let key = <#arg as DepNodeParams<TyCtxt<'_>>>::recover($tcx, $dep_node).unwrap();
-                            if queries::#name::cache_on_disk($tcx, key, None) {
+                            if queries::#name::cache_on_disk($tcx, &key, None) {
                                 let _ = $tcx.#name(key);
                             }
                         }

src/librustc_middle/dep_graph/dep_node.rs

@@ -183,31 +183,10 @@ macro_rules! define_dep_nodes {
                     // tuple args
                     $({
                         erase!($tuple_arg_ty);
-                        let hash = DepNodeParams::to_fingerprint(&arg, _tcx);
-                        let dep_node = DepNode {
-                            kind: DepKind::$variant,
-                            hash
-                        };
-
-                        #[cfg(debug_assertions)]
-                        {
-                            if !dep_node.kind.can_reconstruct_query_key() &&
-                            (_tcx.sess.opts.debugging_opts.incremental_info ||
-                                _tcx.sess.opts.debugging_opts.query_dep_graph)
-                            {
-                                _tcx.dep_graph.register_dep_node_debug_str(dep_node, || {
-                                    arg.to_debug_str(_tcx)
-                                });
-                            }
-                        }
-
-                        return dep_node;
+                        return DepNode::construct(_tcx, DepKind::$variant, &arg)
                     })*
 
-                    DepNode {
-                        kind: DepKind::$variant,
-                        hash: Fingerprint::ZERO,
-                    }
+                    return DepNode::construct(_tcx, DepKind::$variant, &())
                 }
             )*
         }

src/librustc_middle/dep_graph/mod.rs

@@ -98,6 +98,10 @@ impl<'tcx> DepContext for TyCtxt<'tcx> {
     fn debug_dep_tasks(&self) -> bool {
         self.sess.opts.debugging_opts.dep_tasks
     }
+    fn debug_dep_node(&self) -> bool {
+        self.sess.opts.debugging_opts.incremental_info
+            || self.sess.opts.debugging_opts.query_dep_graph
+    }
 
     fn try_force_from_dep_node(&self, dep_node: &DepNode) -> bool {
         // FIXME: This match is just a workaround for incremental bugs and should

src/librustc_middle/ty/query/mod.rs

@@ -1,4 +1,4 @@
-use crate::dep_graph::{self, DepConstructor, DepNode, DepNodeParams};
+use crate::dep_graph::{self, DepNode, DepNodeParams};
 use crate::hir::exports::Export;
 use crate::hir::map;
 use crate::infer::canonical::{self, Canonical};

src/librustc_middle/ty/query/on_disk_cache.rs

@@ -1009,7 +1009,7 @@ where
 
     state.iter_results(|results| {
         for (key, value, dep_node) in results {
-            if Q::cache_on_disk(tcx, key.clone(), Some(&value)) {
+            if Q::cache_on_disk(tcx, &key, Some(&value)) {
                 let dep_node = SerializedDepNodeIndex::new(dep_node.index());
 
                 // Record position of the cache entry.

src/librustc_middle/ty/query/plumbing.rs

@@ -348,12 +348,6 @@ macro_rules! define_queries_inner {
                 &tcx.queries.$name
             }
 
-            #[allow(unused)]
-            #[inline(always)]
-            fn to_dep_node(tcx: TyCtxt<$tcx>, key: &Self::Key) -> DepNode {
-                DepConstructor::$node(tcx, *key)
-            }
-
             #[inline]
             fn compute(tcx: TyCtxt<'tcx>, key: Self::Key) -> Self::Value {
                 let provider = tcx.queries.providers.get(key.query_crate())

src/librustc_query_system/dep_graph/dep_node.rs

@@ -64,6 +64,24 @@ impl<K: DepKind> DepNode<K> {
         debug_assert!(!kind.has_params());
         DepNode { kind, hash: Fingerprint::ZERO }
     }
+
+    pub fn construct<Ctxt, Key>(tcx: Ctxt, kind: K, arg: &Key) -> DepNode<K>
+    where
+        Ctxt: crate::query::QueryContext<DepKind = K>,
+        Key: DepNodeParams<Ctxt>,
+    {
+        let hash = arg.to_fingerprint(tcx);
+        let dep_node = DepNode { kind, hash };
+
+        #[cfg(debug_assertions)]
+        {
+            if !kind.can_reconstruct_query_key() && tcx.debug_dep_node() {
+                tcx.dep_graph().register_dep_node_debug_str(dep_node, || arg.to_debug_str(tcx));
+            }
+        }
+
+        return dep_node;
+    }
 }
 
 impl<K: DepKind> fmt::Debug for DepNode<K> {
@@ -120,6 +138,12 @@ where
     }
 }
 
+impl<Ctxt: DepContext> DepNodeParams<Ctxt> for () {
+    fn to_fingerprint(&self, _: Ctxt) -> Fingerprint {
+        Fingerprint::ZERO
+    }
+}
+
 /// A "work product" corresponds to a `.o` (or other) file that we
 /// save in between runs. These IDs do not have a `DefId` but rather
 /// some independent path or string that persists between runs without

src/librustc_query_system/dep_graph/mod.rs

@@ -28,6 +28,7 @@ pub trait DepContext: Copy {
     fn create_stable_hashing_context(&self) -> Self::StableHashingContext;
 
     fn debug_dep_tasks(&self) -> bool;
+    fn debug_dep_node(&self) -> bool;
 
     /// Try to force a dep node to execute and see if it's green.
     fn try_force_from_dep_node(&self, dep_node: &DepNode<Self::DepKind>) -> bool;

src/librustc_query_system/query/config.rs

@@ -24,6 +24,53 @@ pub trait QueryConfig<CTX> {
     type Stored: Clone;
 }
 
+pub(crate) struct QueryVtable<CTX: QueryContext, K, V> {
+    pub anon: bool,
+    pub dep_kind: CTX::DepKind,
+    pub eval_always: bool,
+
+    // Don't use this method to compute query results, instead use the methods on TyCtxt
+    pub compute: fn(CTX, K) -> V,
+
+    pub hash_result: fn(&mut CTX::StableHashingContext, &V) -> Option<Fingerprint>,
+    pub handle_cycle_error: fn(CTX, CycleError<CTX::Query>) -> V,
+    pub cache_on_disk: fn(CTX, &K, Option<&V>) -> bool,
+    pub try_load_from_disk: fn(CTX, SerializedDepNodeIndex) -> Option<V>,
+}
+
+impl<CTX: QueryContext, K, V> QueryVtable<CTX, K, V> {
+    pub(crate) fn to_dep_node(&self, tcx: CTX, key: &K) -> DepNode<CTX::DepKind>
+    where
+        K: crate::dep_graph::DepNodeParams<CTX>,
+    {
+        DepNode::construct(tcx, self.dep_kind, key)
+    }
+
+    pub(crate) fn compute(&self, tcx: CTX, key: K) -> V {
+        (self.compute)(tcx, key)
+    }
+
+    pub(crate) fn hash_result(
+        &self,
+        hcx: &mut CTX::StableHashingContext,
+        value: &V,
+    ) -> Option<Fingerprint> {
+        (self.hash_result)(hcx, value)
+    }
+
+    pub(crate) fn handle_cycle_error(&self, tcx: CTX, error: CycleError<CTX::Query>) -> V {
+        (self.handle_cycle_error)(tcx, error)
+    }
+
+    pub(crate) fn cache_on_disk(&self, tcx: CTX, key: &K, value: Option<&V>) -> bool {
+        (self.cache_on_disk)(tcx, key, value)
+    }
+
+    pub(crate) fn try_load_from_disk(&self, tcx: CTX, index: SerializedDepNodeIndex) -> Option<V> {
+        (self.try_load_from_disk)(tcx, index)
+    }
+}
+
 pub trait QueryAccessors<CTX: QueryContext>: QueryConfig<CTX> {
     const ANON: bool;
     const EVAL_ALWAYS: bool;
@@ -34,7 +81,12 @@ pub trait QueryAccessors<CTX: QueryContext>: QueryConfig<CTX> {
     // Don't use this method to access query results, instead use the methods on TyCtxt
     fn query_state<'a>(tcx: CTX) -> &'a QueryState<CTX, Self::Cache>;
 
-    fn to_dep_node(tcx: CTX, key: &Self::Key) -> DepNode<CTX::DepKind>;
+    fn to_dep_node(tcx: CTX, key: &Self::Key) -> DepNode<CTX::DepKind>
+    where
+        Self::Key: crate::dep_graph::DepNodeParams<CTX>,
+    {
+        DepNode::construct(tcx, Self::DEP_KIND, key)
+    }
 
     // Don't use this method to compute query results, instead use the methods on TyCtxt
     fn compute(tcx: CTX, key: Self::Key) -> Self::Value;
@@ -51,7 +103,7 @@ pub trait QueryDescription<CTX: QueryContext>: QueryAccessors<CTX> {
     fn describe(tcx: CTX, key: Self::Key) -> Cow<'static, str>;
 
     #[inline]
-    fn cache_on_disk(_: CTX, _: Self::Key, _: Option<&Self::Value>) -> bool {
+    fn cache_on_disk(_: CTX, _: &Self::Key, _: Option<&Self::Value>) -> bool {
         false
     }
 
@@ -60,6 +112,27 @@ pub trait QueryDescription<CTX: QueryContext>: QueryAccessors<CTX> {
     }
 }
 
+pub(crate) trait QueryVtableExt<CTX: QueryContext, K, V> {
+    const VTABLE: QueryVtable<CTX, K, V>;
+}
+
+impl<CTX, Q> QueryVtableExt<CTX, Q::Key, Q::Value> for Q
+where
+    CTX: QueryContext,
+    Q: QueryDescription<CTX>,
+{
+    const VTABLE: QueryVtable<CTX, Q::Key, Q::Value> = QueryVtable {
+        anon: Q::ANON,
+        dep_kind: Q::DEP_KIND,
+        eval_always: Q::EVAL_ALWAYS,
+        compute: Q::compute,
+        hash_result: Q::hash_result,
+        handle_cycle_error: Q::handle_cycle_error,
+        cache_on_disk: Q::cache_on_disk,
+        try_load_from_disk: Q::try_load_from_disk,
+    };
+}
+
 impl<CTX: QueryContext, M> QueryDescription<CTX> for M
 where
     M: QueryAccessors<CTX, Key = DefId>,
@@ -73,7 +146,7 @@ where
         }
     }
 
-    default fn cache_on_disk(_: CTX, _: Self::Key, _: Option<&Self::Value>) -> bool {
+    default fn cache_on_disk(_: CTX, _: &Self::Key, _: Option<&Self::Value>) -> bool {
         false
     }