Auto merge of #139410 - Zoxc:fix-dep-graph-no-prev-map, r=oli-obk

Reuse the index from promoted nodes when coloring executed tasks

https://github.com/rust-lang/rust/pull/138824 did not correctly handle the case where a dep node was promoted green, but later or concurrently executed. It resulted in multiple dep nodes being allocated to it. This fixes that by checking that the node was not previously green in the encoder lock.

This also fixes a race when forcing diagnostic nodes introduced in https://github.com/rust-lang/rust/pull/138824.

https://github.com/rust-lang/rust/pull/138824 should get reverted on beta.

This should fix #139110.

r? `@oli-obk`

compiler/rustc_query_system/src/dep_graph/graph.rs

@@ -141,7 +141,7 @@ impl<D: Deps> DepGraph<D> {
         let colors = DepNodeColorMap::new(prev_graph_node_count);
 
         // Instantiate a node with zero dependencies only once for anonymous queries.
-        let _green_node_index = current.alloc_node(
+        let _green_node_index = current.alloc_new_node(
             DepNode { kind: D::DEP_KIND_ANON_ZERO_DEPS, hash: current.anon_id_seed.into() },
             EdgesVec::new(),
             Fingerprint::ZERO,
@@ -149,7 +149,7 @@ impl<D: Deps> DepGraph<D> {
         assert_eq!(_green_node_index, DepNodeIndex::SINGLETON_ZERO_DEPS_ANON_NODE);
 
         // Instantiate a dependy-less red node only once for anonymous queries.
-        let red_node_index = current.alloc_node(
+        let red_node_index = current.alloc_new_node(
             DepNode { kind: D::DEP_KIND_RED, hash: Fingerprint::ZERO.into() },
             EdgesVec::new(),
             Fingerprint::ZERO,
@@ -438,7 +438,7 @@ impl<D: Deps> DepGraphData<D> {
                 // memory impact of this `anon_node_to_index` map remains tolerable, and helps
                 // us avoid useless growth of the graph with almost-equivalent nodes.
                 self.current.anon_node_to_index.get_or_insert_with(target_dep_node, || {
-                    self.current.alloc_node(target_dep_node, task_deps, Fingerprint::ZERO)
+                    self.current.alloc_new_node(target_dep_node, task_deps, Fingerprint::ZERO)
                 })
             }
         };
@@ -680,8 +680,8 @@ impl<D: Deps> DepGraphData<D> {
         qcx: Qcx,
         diagnostic: &DiagInner,
     ) -> DepNodeIndex {
-        // Use `send` so we get an unique index, even though the dep node is not.
+        // Use `send_new` so we get an unique index, even though the dep node is not.
-        let dep_node_index = self.current.encoder.send(
+        let dep_node_index = self.current.encoder.send_new(
             DepNode {
                 kind: D::DEP_KIND_SIDE_EFFECT,
                 hash: PackedFingerprint::from(Fingerprint::ZERO),
@@ -713,20 +713,22 @@ impl<D: Deps> DepGraphData<D> {
                 }
             }
 
-            // Manually recreate the node as `promote_node_and_deps_to_current` expects all
+            // Use `send_and_color` as `promote_node_and_deps_to_current` expects all
-            // green dependencies.
+            // green dependencies. `send_and_color` will also prevent multiple nodes
-            let dep_node_index = self.current.encoder.send(
+            // being encoded for concurrent calls.
+            let dep_node_index = self.current.encoder.send_and_color(
+                prev_index,
+                &self.colors,
                 DepNode {
                     kind: D::DEP_KIND_SIDE_EFFECT,
                     hash: PackedFingerprint::from(Fingerprint::ZERO),
                 },
                 Fingerprint::ZERO,
                 std::iter::once(DepNodeIndex::FOREVER_RED_NODE).collect(),
+                true,
             );
+            // This will just overwrite the same value for concurrent calls.
             qcx.store_side_effect(dep_node_index, side_effect);
-
-            // Mark the node as green.
-            self.colors.insert(prev_index, DepNodeColor::Green(dep_node_index));
         })
     }
 
@@ -736,38 +738,43 @@ impl<D: Deps> DepGraphData<D> {
         edges: EdgesVec,
         fingerprint: Option<Fingerprint>,
     ) -> DepNodeIndex {
-        let dep_node_index =
-            self.current.alloc_node(key, edges, fingerprint.unwrap_or(Fingerprint::ZERO));
-
         if let Some(prev_index) = self.previous.node_to_index_opt(&key) {
             // Determine the color and index of the new `DepNode`.
-            let color = if let Some(fingerprint) = fingerprint {
+            let is_green = if let Some(fingerprint) = fingerprint {
                 if fingerprint == self.previous.fingerprint_by_index(prev_index) {
                     // This is a green node: it existed in the previous compilation,
                     // its query was re-executed, and it has the same result as before.
-                    DepNodeColor::Green(dep_node_index)
+                    true
                 } else {
                     // This is a red node: it existed in the previous compilation, its query
                     // was re-executed, but it has a different result from before.
-                    DepNodeColor::Red
+                    false
                 }
             } else {
                 // This is a red node, effectively: it existed in the previous compilation
                 // session, its query was re-executed, but it doesn't compute a result hash
                 // (i.e. it represents a `no_hash` query), so we have no way of determining
                 // whether or not the result was the same as before.
-                DepNodeColor::Red
+                false
             };
 
-            debug_assert!(
+            let fingerprint = fingerprint.unwrap_or(Fingerprint::ZERO);
-                self.colors.get(prev_index).is_none(),
+
-                "DepGraph::with_task() - Duplicate DepNodeColor insertion for {key:?}",
+            let dep_node_index = self.current.encoder.send_and_color(
+                prev_index,
+                &self.colors,
+                key,
+                fingerprint,
+                edges,
+                is_green,
             );
 
-            self.colors.insert(prev_index, color);
+            self.current.record_node(dep_node_index, key, fingerprint);
-        }
 
-        dep_node_index
+            dep_node_index
+        } else {
+            self.current.alloc_new_node(key, edges, fingerprint.unwrap_or(Fingerprint::ZERO))
+        }
     }
 
     fn promote_node_and_deps_to_current(&self, prev_index: SerializedDepNodeIndex) -> DepNodeIndex {
@@ -1246,19 +1253,15 @@ impl<D: Deps> CurrentDepGraph<D> {
         assert_eq!(previous, fingerprint, "Unstable fingerprints for {:?}", key);
     }
 
-    /// Writes the node to the current dep-graph and allocates a `DepNodeIndex` for it.
-    /// Assumes that this is a node that has no equivalent in the previous dep-graph.
     #[inline(always)]
-    fn alloc_node(
+    fn record_node(
         &self,
+        dep_node_index: DepNodeIndex,
         key: DepNode,
-        edges: EdgesVec,
+        _current_fingerprint: Fingerprint,
-        current_fingerprint: Fingerprint,
+    ) {
-    ) -> DepNodeIndex {
-        let dep_node_index = self.encoder.send(key, current_fingerprint, edges);
-
         #[cfg(debug_assertions)]
-        self.record_edge(dep_node_index, key, current_fingerprint);
+        self.record_edge(dep_node_index, key, _current_fingerprint);
 
         if let Some(ref nodes_in_current_session) = self.nodes_in_current_session {
             outline(|| {
@@ -1267,6 +1270,20 @@ impl<D: Deps> CurrentDepGraph<D> {
                 }
             });
         }
+    }
+
+    /// Writes the node to the current dep-graph and allocates a `DepNodeIndex` for it.
+    /// Assumes that this is a node that has no equivalent in the previous dep-graph.
+    #[inline(always)]
+    fn alloc_new_node(
+        &self,
+        key: DepNode,
+        edges: EdgesVec,
+        current_fingerprint: Fingerprint,
+    ) -> DepNodeIndex {
+        let dep_node_index = self.encoder.send_new(key, current_fingerprint, edges);
+
+        self.record_node(dep_node_index, key, current_fingerprint);
 
         dep_node_index
     }

compiler/rustc_query_system/src/dep_graph/serialized.rs

@@ -707,7 +707,8 @@ impl<D: Deps> GraphEncoder<D> {
         }
     }
 
-    pub(crate) fn send(
+    /// Encodes a node that does not exists in the previous graph.
+    pub(crate) fn send_new(
         &self,
         node: DepNode,
         fingerprint: Fingerprint,
@@ -718,6 +719,40 @@ impl<D: Deps> GraphEncoder<D> {
         self.status.lock().as_mut().unwrap().encode_node(&node, &self.record_graph)
     }
 
+    /// Encodes a node that exists in the previous graph, but was re-executed.
+    ///
+    /// This will also ensure the dep node is colored either red or green.
+    pub(crate) fn send_and_color(
+        &self,
+        prev_index: SerializedDepNodeIndex,
+        colors: &DepNodeColorMap,
+        node: DepNode,
+        fingerprint: Fingerprint,
+        edges: EdgesVec,
+        is_green: bool,
+    ) -> DepNodeIndex {
+        let _prof_timer = self.profiler.generic_activity("incr_comp_encode_dep_graph");
+        let node = NodeInfo { node, fingerprint, edges };
+
+        let mut status = self.status.lock();
+        let status = status.as_mut().unwrap();
+
+        // Check colors inside the lock to avoid racing when `send_promoted` is called concurrently
+        // on the same index.
+        match colors.get(prev_index) {
+            None => {
+                let dep_node_index = status.encode_node(&node, &self.record_graph);
+                colors.insert(
+                    prev_index,
+                    if is_green { DepNodeColor::Green(dep_node_index) } else { DepNodeColor::Red },
+                );
+                dep_node_index
+            }
+            Some(DepNodeColor::Green(dep_node_index)) => dep_node_index,
+            Some(DepNodeColor::Red) => panic!(),
+        }
+    }
+
     /// Encodes a node that was promoted from the previous graph. It reads the information directly from
     /// the previous dep graph and expects all edges to already have a new dep node index assigned.
     ///
@@ -733,8 +768,8 @@ impl<D: Deps> GraphEncoder<D> {
         let mut status = self.status.lock();
         let status = status.as_mut().unwrap();
 
-        // Check colors inside the lock to avoid racing when `send_promoted` is called concurrently
+        // Check colors inside the lock to avoid racing when `send_promoted` or `send_and_color`
-        // on the same index.
+        // is called concurrently on the same index.
         match colors.get(prev_index) {
             None => {
                 let dep_node_index =