Create a forever red node and use it to force side effects.

Author: cjgillot

compiler/rustc_middle/src/query/mod.rs

@@ -20,12 +20,6 @@ rustc_queries! {
         desc { "trigger a delay span bug" }
     }
 
-    /// Create a new definition within the incr. comp. engine.
-    query register_def(_: ty::RawLocalDefId) -> LocalDefId {
-        eval_always
-        desc { "register a DefId with the incr. comp. engine" }
-    }
-
     query resolutions(_: ()) -> &'tcx ty::ResolverOutputs {
         eval_always
         no_hash

compiler/rustc_middle/src/ty/context.rs

@@ -123,9 +123,6 @@ impl<'tcx> Interner for TyCtxt<'tcx> {
     type PlaceholderRegion = ty::PlaceholderRegion;
 }
 
-#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, HashStable)]
-pub struct RawLocalDefId(LocalDefId);
-
 /// A type that is not publicly constructable. This prevents people from making [`TyKind::Error`]s
 /// except through the error-reporting functions on a [`tcx`][TyCtxt].
 #[derive(Copy, Clone, Debug, Eq, Hash, PartialEq, PartialOrd, Ord)]
@@ -1477,23 +1474,15 @@ impl<'tcx> TyCtxt<'tcx> {
         let def_id = self.definitions.write().create_def(parent, data);
 
         // We need to ensure that these side effects are re-run by the incr. comp. engine.
-        // When the incr. comp. engine considers marking this query as green, eval_always requires
-        // we run the function to run.  To invoke it, the parameter cannot be reconstructed from
-        // the DepNode, so the caller query is run.  Luckily, we are inside the caller query,
-        // therefore the definition is properly created.
-        debug_assert!({
-            use rustc_query_system::dep_graph::{DepContext, DepNodeParams};
-            self.is_eval_always(crate::dep_graph::DepKind::register_def)
-                && !<RawLocalDefId as DepNodeParams<TyCtxt<'_>>>::fingerprint_style()
-                    .reconstructible()
-        });
+        use rustc_query_system::dep_graph::DepNodeIndex;
+        self.dep_graph.read_index(DepNodeIndex::FOREVER_RED_NODE);
 
         // Any LocalDefId which is used within queries, either as key or result, either:
         // - has been created before the construction of the TyCtxt;
-        // - has been created by this call to `register_def`.
+        // - has been created by this call to `create_def`.
         // As a consequence, this LocalDefId is always re-created before it is needed by the incr.
         // comp. engine itself.
-        self.register_def(RawLocalDefId(def_id))
+        def_id
     }
 
     pub fn iter_local_def_id(self) -> impl Iterator<Item = LocalDefId> + 'tcx {
@@ -3033,5 +3022,4 @@ pub fn provide(providers: &mut ty::query::Providers) {
         // We want to check if the panic handler was defined in this crate
         tcx.lang_items().panic_impl().map_or(false, |did| did.is_local())
     };
-    providers.register_def = |_, raw_id| raw_id.0;
 }

compiler/rustc_middle/src/ty/mod.rs

@@ -72,8 +72,8 @@ pub use self::consts::{
 pub use self::context::{
     tls, CanonicalUserType, CanonicalUserTypeAnnotation, CanonicalUserTypeAnnotations,
     CtxtInterners, DelaySpanBugEmitted, FreeRegionInfo, GeneratorDiagnosticData,
-    GeneratorInteriorTypeCause, GlobalCtxt, Lift, OnDiskCache, RawLocalDefId, TyCtxt,
-    TypeckResults, UserType, UserTypeAnnotationIndex,
+    GeneratorInteriorTypeCause, GlobalCtxt, Lift, OnDiskCache, TyCtxt, TypeckResults, UserType,
+    UserTypeAnnotationIndex,
 };
 pub use self::instance::{Instance, InstanceDef};
 pub use self::list::List;

compiler/rustc_query_impl/src/keys.rs

@@ -39,17 +39,6 @@ impl Key for () {
     }
 }
 
-impl Key for ty::RawLocalDefId {
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        true
-    }
-
-    fn default_span(&self, _: TyCtxt<'_>) -> Span {
-        DUMMY_SP
-    }
-}
-
 impl<'tcx> Key for ty::InstanceDef<'tcx> {
     #[inline(always)]
     fn query_crate_is_local(&self) -> bool {

compiler/rustc_query_system/src/dep_graph/graph.rs

@@ -43,6 +43,7 @@ rustc_index::newtype_index! {
 impl DepNodeIndex {
     pub const INVALID: DepNodeIndex = DepNodeIndex::MAX;
     pub const SINGLETON_DEPENDENCYLESS_ANON_NODE: DepNodeIndex = DepNodeIndex::from_u32(0);
+    pub const FOREVER_RED_NODE: DepNodeIndex = DepNodeIndex::from_u32(1);
 }
 
 impl std::convert::From<DepNodeIndex> for QueryInvocationId {
@@ -124,6 +125,8 @@ impl<K: DepKind> DepGraph<K> {
             record_stats,
         );
 
+        let colors = DepNodeColorMap::new(prev_graph_node_count);
+
         // Instantiate a dependy-less node only once for anonymous queries.
         let _green_node_index = current.intern_new_node(
             profiler,
@@ -133,14 +136,26 @@ impl<K: DepKind> DepGraph<K> {
         );
         debug_assert_eq!(_green_node_index, DepNodeIndex::SINGLETON_DEPENDENCYLESS_ANON_NODE);
 
+        // Instantiate a dependy-less red node only once for anonymous queries.
+        let (_red_node_index, _prev_and_index) = current.intern_node(
+            profiler,
+            &prev_graph,
+            DepNode { kind: DepKind::NULL, hash: Fingerprint::ZERO.into() },
+            smallvec![],
+            None,
+            false,
+        );
+        debug_assert_eq!(_red_node_index, DepNodeIndex::FOREVER_RED_NODE);
+        debug_assert!(matches!(_prev_and_index, None | Some((_, DepNodeColor::Red))));
+
         DepGraph {
             data: Some(Lrc::new(DepGraphData {
                 previous_work_products: prev_work_products,
                 dep_node_debug: Default::default(),
                 current,
                 processed_side_effects: Default::default(),
                 previous: prev_graph,
-                colors: DepNodeColorMap::new(prev_graph_node_count),
+                colors,
                 debug_loaded_from_disk: Default::default(),
             })),
             virtual_dep_node_index: Lrc::new(AtomicU32::new(0)),
@@ -965,6 +980,9 @@ impl<K: DepKind> CurrentDepGraph<K> {
         let nanos = duration.as_secs() * 1_000_000_000 + duration.subsec_nanos() as u64;
         let mut stable_hasher = StableHasher::new();
         nanos.hash(&mut stable_hasher);
+        let anon_id_seed = stable_hasher.finish();
+        // We rely on the fact that `anon_id_seed` is not zero when creating static nodes.
+        debug_assert_ne!(anon_id_seed, Fingerprint::ZERO);
 
         #[cfg(debug_assertions)]
         let forbidden_edge = match env::var("RUST_FORBID_DEP_GRAPH_EDGE") {
@@ -1000,7 +1018,7 @@ impl<K: DepKind> CurrentDepGraph<K> {
                 )
             }),
             prev_index_to_index: Lock::new(IndexVec::from_elem_n(None, prev_graph_node_count)),
-            anon_id_seed: stable_hasher.finish(),
+            anon_id_seed,
             #[cfg(debug_assertions)]
             forbidden_edge,
             total_read_count: AtomicU64::new(0),