From 08328d329b5ff791e4ac3f7ddb2293a0ae8a4f23 Mon Sep 17 00:00:00 2001
From: Aman Arora <me@aman-arora.com>
Date: Sat, 19 Sep 2020 22:30:06 -0400
Subject: [PATCH 1/2] Don't allocate DepNode if anon or no dependencies

---
 compiler/rustc_middle/src/dep_graph/mod.rs    |  4 ++++
 .../rustc_query_system/src/dep_graph/graph.rs | 20 +++++++++++++++----
 .../rustc_query_system/src/dep_graph/mod.rs   |  2 ++
 3 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/compiler/rustc_middle/src/dep_graph/mod.rs b/compiler/rustc_middle/src/dep_graph/mod.rs
index 6697524279874..9de7e1bff448e 100644
--- a/compiler/rustc_middle/src/dep_graph/mod.rs
+++ b/compiler/rustc_middle/src/dep_graph/mod.rs
@@ -85,6 +85,10 @@ impl rustc_query_system::dep_graph::DepKind for DepKind {
     fn can_reconstruct_query_key(&self) -> bool {
         DepKind::can_reconstruct_query_key(self)
     }
+
+    fn is_anon(&self) -> bool {
+        DepKind::is_anon(self)
+    }
 }
 
 impl<'tcx> DepContext for TyCtxt<'tcx> {
diff --git a/compiler/rustc_query_system/src/dep_graph/graph.rs b/compiler/rustc_query_system/src/dep_graph/graph.rs
index 85335f0ba50c2..5bdf6c889781b 100644
--- a/compiler/rustc_query_system/src/dep_graph/graph.rs
+++ b/compiler/rustc_query_system/src/dep_graph/graph.rs
@@ -230,7 +230,7 @@ impl<K: DepKind> DepGraph<K> {
             DepNode<K>,
             Fingerprint,
             Option<TaskDeps<K>>,
-        ) -> DepNodeIndex,
+        ) -> Option<DepNodeIndex>,
         hash_result: impl FnOnce(&mut Ctxt::StableHashingContext, &R) -> Option<Fingerprint>,
     ) -> (R, DepNodeIndex) {
         if let Some(ref data) = self.data {
@@ -260,6 +260,13 @@ impl<K: DepKind> DepGraph<K> {
 
             let print_status = cfg!(debug_assertions) && cx.debug_dep_tasks();
 
+            if matches!(dep_node_index, None) {
+                return (result, self.next_virtual_depnode_index());
+            }
+
+            // Handled None case above, safe to unwrap here.
+            let dep_node_index = dep_node_index.unwrap();
+
             // Determine the color of the new DepNode.
             if let Some(prev_index) = data.previous.node_to_index_opt(&key) {
                 let prev_fingerprint = data.previous.fingerprint_by_index(prev_index);
@@ -956,7 +963,7 @@ impl<K: DepKind> CurrentDepGraph<K> {
         node: DepNode<K>,
         task_deps: TaskDeps<K>,
         fingerprint: Fingerprint,
-    ) -> DepNodeIndex {
+    ) -> Option<DepNodeIndex> {
         self.alloc_node(node, task_deps.reads, fingerprint)
     }
 
@@ -989,11 +996,16 @@ impl<K: DepKind> CurrentDepGraph<K> {
         dep_node: DepNode<K>,
         edges: EdgesVec,
         fingerprint: Fingerprint,
-    ) -> DepNodeIndex {
+    ) -> Option<DepNodeIndex> {
         debug_assert!(
             !self.node_to_node_index.get_shard_by_value(&dep_node).lock().contains_key(&dep_node)
         );
-        self.intern_node(dep_node, edges, fingerprint)
+
+        if dep_node.kind.is_anon() || edges.is_empty() {
+            return None;
+        }
+
+        Some(self.intern_node(dep_node, edges, fingerprint))
     }
 
     fn intern_node(
diff --git a/compiler/rustc_query_system/src/dep_graph/mod.rs b/compiler/rustc_query_system/src/dep_graph/mod.rs
index e8d02692f37ba..9a13dfc3debab 100644
--- a/compiler/rustc_query_system/src/dep_graph/mod.rs
+++ b/compiler/rustc_query_system/src/dep_graph/mod.rs
@@ -82,4 +82,6 @@ pub trait DepKind: Copy + fmt::Debug + Eq + Ord + Hash {
         OP: for<'a> FnOnce(Option<&'a Lock<TaskDeps<Self>>>);
 
     fn can_reconstruct_query_key(&self) -> bool;
+
+    fn is_anon(&self) -> bool;
 }

From 6c03fb8dd0535d9131a67a242247cf6f9b9fe1d9 Mon Sep 17 00:00:00 2001
From: Aman Arora <me@aman-arora.com>
Date: Sun, 20 Sep 2020 01:10:49 -0400
Subject: [PATCH 2/2] Don't check edges empty

---
 compiler/rustc_middle/src/dep_graph/mod.rs         |  1 +
 compiler/rustc_query_system/src/dep_graph/graph.rs | 11 +++++------
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/compiler/rustc_middle/src/dep_graph/mod.rs b/compiler/rustc_middle/src/dep_graph/mod.rs
index 9de7e1bff448e..2b4bced34b29d 100644
--- a/compiler/rustc_middle/src/dep_graph/mod.rs
+++ b/compiler/rustc_middle/src/dep_graph/mod.rs
@@ -86,6 +86,7 @@ impl rustc_query_system::dep_graph::DepKind for DepKind {
         DepKind::can_reconstruct_query_key(self)
     }
 
+    #[inline]
     fn is_anon(&self) -> bool {
         DepKind::is_anon(self)
     }
diff --git a/compiler/rustc_query_system/src/dep_graph/graph.rs b/compiler/rustc_query_system/src/dep_graph/graph.rs
index 5bdf6c889781b..ab6a82c82b2ac 100644
--- a/compiler/rustc_query_system/src/dep_graph/graph.rs
+++ b/compiler/rustc_query_system/src/dep_graph/graph.rs
@@ -260,12 +260,11 @@ impl<K: DepKind> DepGraph<K> {
 
             let print_status = cfg!(debug_assertions) && cx.debug_dep_tasks();
 
-            if matches!(dep_node_index, None) {
+            let dep_node_index = if let Some(dep_node_index) = dep_node_index {
+                dep_node_index
+            } else {
                 return (result, self.next_virtual_depnode_index());
-            }
-
-            // Handled None case above, safe to unwrap here.
-            let dep_node_index = dep_node_index.unwrap();
+            };
 
             // Determine the color of the new DepNode.
             if let Some(prev_index) = data.previous.node_to_index_opt(&key) {
@@ -1001,7 +1000,7 @@ impl<K: DepKind> CurrentDepGraph<K> {
             !self.node_to_node_index.get_shard_by_value(&dep_node).lock().contains_key(&dep_node)
         );
 
-        if dep_node.kind.is_anon() || edges.is_empty() {
+        if dep_node.kind.is_anon() {
             return None;
         }