Auto merge of #122156 - Zoxc:side-effect-dep-node, r=oli-obk

Represent diagnostic side effects as dep nodes

This changes diagnostic to be tracked as a special dep node (`SideEffect`) instead of having a list of side effects associated with each dep node. `SideEffect` is always red and when forced, it emits the diagnostic and marks itself green. Each emitted diagnostic generates a new `SideEffect` with an unique dep node index.

Some implications of this:

- Diagnostic may now be emitted more than once as they can be emitted once when the `SideEffect` gets marked green and again if the task it depends on needs to be re-executed due to another node being red. It relies on deduplicating of diagnostics to avoid that.

- Anon tasks which emits diagnostics will no longer *incorrectly* be merged with other anon tasks.

- Reusing a CGU will now emit diagnostics from the task generating it.

4 files changed, 19 insertions, 45 deletions

diff --git a/compiler/rustc_middle/src/dep_graph/dep_node.rs b/compiler/rustc_middle/src/dep_graph/dep_node.rs
index 7525aeb9227..f967d8b92c7 100644
--- a/compiler/rustc_middle/src/dep_graph/dep_node.rs
+++ b/compiler/rustc_middle/src/dep_graph/dep_node.rs
@@ -79,6 +79,7 @@ rustc_query_append!(define_dep_nodes![
     [] fn Null() -> (),
     /// We use this to create a forever-red node.
     [] fn Red() -> (),
+    [] fn SideEffect() -> (),
     [] fn TraitSelect() -> (),
     [] fn CompileCodegenUnit() -> (),
     [] fn CompileMonoItem() -> (),
diff --git a/compiler/rustc_middle/src/dep_graph/mod.rs b/compiler/rustc_middle/src/dep_graph/mod.rs
index 2090c3e6da6..c927538b4cf 100644
--- a/compiler/rustc_middle/src/dep_graph/mod.rs
+++ b/compiler/rustc_middle/src/dep_graph/mod.rs
@@ -46,6 +46,7 @@ impl Deps for DepsType {
 
     const DEP_KIND_NULL: DepKind = dep_kinds::Null;
     const DEP_KIND_RED: DepKind = dep_kinds::Red;
+    const DEP_KIND_SIDE_EFFECT: DepKind = dep_kinds::SideEffect;
     const DEP_KIND_MAX: u16 = dep_node::DEP_KIND_VARIANTS - 1;
 }
 
diff --git a/compiler/rustc_middle/src/query/on_disk_cache.rs b/compiler/rustc_middle/src/query/on_disk_cache.rs
index e66958dfcb8..14e3ce8bef6 100644
--- a/compiler/rustc_middle/src/query/on_disk_cache.rs
+++ b/compiler/rustc_middle/src/query/on_disk_cache.rs
@@ -11,7 +11,7 @@ use rustc_hir::def_id::{CrateNum, DefId, DefIndex, LOCAL_CRATE, LocalDefId, Stab
 use rustc_hir::definitions::DefPathHash;
 use rustc_index::{Idx, IndexVec};
 use rustc_macros::{Decodable, Encodable};
-use rustc_query_system::query::QuerySideEffects;
+use rustc_query_system::query::QuerySideEffect;
 use rustc_serialize::opaque::{FileEncodeResult, FileEncoder, IntEncodedWithFixedSize, MemDecoder};
 use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
 use rustc_session::Session;
@@ -55,9 +55,9 @@ pub struct OnDiskCache {
     // The complete cache data in serialized form.
     serialized_data: RwLock<Option<Mmap>>,
 
-    // Collects all `QuerySideEffects` created during the current compilation
+    // Collects all `QuerySideEffect` created during the current compilation
     // session.
-    current_side_effects: Lock<FxHashMap<DepNodeIndex, QuerySideEffects>>,
+    current_side_effects: Lock<FxHashMap<DepNodeIndex, QuerySideEffect>>,
 
     file_index_to_stable_id: FxHashMap<SourceFileIndex, EncodedSourceFileId>,
 
@@ -68,7 +68,7 @@ pub struct OnDiskCache {
     // `serialized_data`.
     query_result_index: FxHashMap<SerializedDepNodeIndex, AbsoluteBytePos>,
 
-    // A map from dep-node to the position of any associated `QuerySideEffects` in
+    // A map from dep-node to the position of any associated `QuerySideEffect` in
     // `serialized_data`.
     prev_side_effects_index: FxHashMap<SerializedDepNodeIndex, AbsoluteBytePos>,
 
@@ -270,10 +270,10 @@ impl OnDiskCache {
                 .current_side_effects
                 .borrow()
                 .iter()
-                .map(|(dep_node_index, side_effects)| {
+                .map(|(dep_node_index, side_effect)| {
                     let pos = AbsoluteBytePos::new(encoder.position());
                     let dep_node_index = SerializedDepNodeIndex::new(dep_node_index.index());
-                    encoder.encode_tagged(dep_node_index, side_effects);
+                    encoder.encode_tagged(dep_node_index, side_effect);
 
                     (dep_node_index, pos)
                 })
@@ -352,24 +352,23 @@ impl OnDiskCache {
         })
     }
 
-    /// Loads a `QuerySideEffects` created during the previous compilation session.
-    pub fn load_side_effects(
+    /// Loads a `QuerySideEffect` created during the previous compilation session.
+    pub fn load_side_effect(
         &self,
         tcx: TyCtxt<'_>,
         dep_node_index: SerializedDepNodeIndex,
-    ) -> QuerySideEffects {
-        let side_effects: Option<QuerySideEffects> =
+    ) -> Option<QuerySideEffect> {
+        let side_effect: Option<QuerySideEffect> =
             self.load_indexed(tcx, dep_node_index, &self.prev_side_effects_index);
-
-        side_effects.unwrap_or_default()
+        side_effect
     }
 
-    /// Stores a `QuerySideEffects` emitted during the current compilation session.
-    /// Anything stored like this will be available via `load_side_effects` in
+    /// Stores a `QuerySideEffect` emitted during the current compilation session.
+    /// Anything stored like this will be available via `load_side_effect` in
     /// the next compilation session.
-    pub fn store_side_effects(&self, dep_node_index: DepNodeIndex, side_effects: QuerySideEffects) {
+    pub fn store_side_effect(&self, dep_node_index: DepNodeIndex, side_effect: QuerySideEffect) {
         let mut current_side_effects = self.current_side_effects.borrow_mut();
-        let prev = current_side_effects.insert(dep_node_index, side_effects);
+        let prev = current_side_effects.insert(dep_node_index, side_effect);
         debug_assert!(prev.is_none());
     }
 
@@ -395,21 +394,6 @@ impl OnDiskCache {
         opt_value
     }
 
-    /// Stores side effect emitted during computation of an anonymous query.
-    /// Since many anonymous queries can share the same `DepNode`, we aggregate
-    /// them -- as opposed to regular queries where we assume that there is a
-    /// 1:1 relationship between query-key and `DepNode`.
-    pub fn store_side_effects_for_anon_node(
-        &self,
-        dep_node_index: DepNodeIndex,
-        side_effects: QuerySideEffects,
-    ) {
-        let mut current_side_effects = self.current_side_effects.borrow_mut();
-
-        let x = current_side_effects.entry(dep_node_index).or_default();
-        x.append(side_effects);
-    }
-
     fn load_indexed<'tcx, T>(
         &self,
         tcx: TyCtxt<'tcx>,
diff --git a/compiler/rustc_middle/src/ty/context/tls.rs b/compiler/rustc_middle/src/ty/context/tls.rs
index eaab8474dd2..5fc80bc7936 100644
--- a/compiler/rustc_middle/src/ty/context/tls.rs
+++ b/compiler/rustc_middle/src/ty/context/tls.rs
@@ -1,8 +1,6 @@
 use std::{mem, ptr};
 
-use rustc_data_structures::sync::{self, Lock};
-use rustc_errors::DiagInner;
-use thin_vec::ThinVec;
+use rustc_data_structures::sync;
 
 use super::{GlobalCtxt, TyCtxt};
 use crate::dep_graph::TaskDepsRef;
@@ -22,10 +20,6 @@ pub struct ImplicitCtxt<'a, 'tcx> {
     /// `ty::query::plumbing` when executing a query.
     pub query: Option<QueryJobId>,
 
-    /// Where to store diagnostics for the current query job, if any.
-    /// This is updated by `JobOwner::start` in `ty::query::plumbing` when executing a query.
-    pub diagnostics: Option<&'a Lock<ThinVec<DiagInner>>>,
-
     /// Used to prevent queries from calling too deeply.
     pub query_depth: usize,
 
@@ -37,13 +31,7 @@ pub struct ImplicitCtxt<'a, 'tcx> {
 impl<'a, 'tcx> ImplicitCtxt<'a, 'tcx> {
     pub fn new(gcx: &'tcx GlobalCtxt<'tcx>) -> Self {
         let tcx = TyCtxt { gcx };
-        ImplicitCtxt {
-            tcx,
-            query: None,
-            diagnostics: None,
-            query_depth: 0,
-            task_deps: TaskDepsRef::Ignore,
-        }
+        ImplicitCtxt { tcx, query: None, query_depth: 0, task_deps: TaskDepsRef::Ignore }
     }
 }