Add #[rustc_clean(loaded_from_disk)] to assert loading of query result

Currently, you can use `#[rustc_clean]` to assert to that a particular
query (technically, a `DepNode`) is green or red. However, a green
`DepNode` does not mean that the query result was actually deserialized
from disk - we might have never re-run a query that needed the result.

Some incremental tests are written as regression tests for ICEs that
occured during query result decoding. Using
`#[rustc_clean(loaded_from_disk="typeck")]`, you can now assert
that the result of a particular query (e.g. `typeck`) was actually
loaded from disk, in addition to being green.

compiler/rustc_query_system/src/dep_graph/graph.rs

@@ -88,6 +88,11 @@ struct DepGraphData<K: DepKind> {
     previous_work_products: FxHashMap<WorkProductId, WorkProduct>,
 
     dep_node_debug: Lock<FxHashMap<DepNode<K>, String>>,
+
+    /// Used by incremental compilation tests to assert that
+    /// a particular query result was decoded from disk
+    /// (not just marked green)
+    debug_loaded_from_disk: Lock<FxHashSet<DepNode<K>>>,
 }
 
 pub fn hash_result<R>(hcx: &mut StableHashingContext<'_>, result: &R) -> Fingerprint
@@ -135,6 +140,7 @@ impl<K: DepKind> DepGraph<K> {
                 processed_side_effects: Default::default(),
                 previous: prev_graph,
                 colors: DepNodeColorMap::new(prev_graph_node_count),
+                debug_loaded_from_disk: Default::default(),
             })),
             virtual_dep_node_index: Lrc::new(AtomicU32::new(0)),
         }
@@ -438,6 +444,14 @@ impl<K: DepKind> DepGraph<K> {
         &self.data.as_ref().unwrap().previous_work_products
     }
 
+    pub fn mark_debug_loaded_from_disk(&self, dep_node: DepNode<K>) {
+        self.data.as_ref().unwrap().debug_loaded_from_disk.lock().insert(dep_node);
+    }
+
+    pub fn debug_was_loaded_from_disk(&self, dep_node: DepNode<K>) -> bool {
+        self.data.as_ref().unwrap().debug_loaded_from_disk.lock().contains(&dep_node)
+    }
+
     #[inline(always)]
     pub fn register_dep_node_debug_str<F>(&self, dep_node: DepNode<K>, debug_str_gen: F)
     where

compiler/rustc_query_system/src/query/plumbing.rs

@@ -519,6 +519,10 @@ where
         prof_timer.finish_with_query_invocation_id(dep_node_index.into());
 
         if let Some(result) = result {
+            if unlikely!(tcx.dep_context().sess().opts.debugging_opts.query_dep_graph) {
+                dep_graph.mark_debug_loaded_from_disk(*dep_node)
+            }
+
             let prev_fingerprint = tcx
                 .dep_context()
                 .dep_graph()