1 files changed, 61 insertions, 0 deletions
diff --git a/compiler/rustc_query_system/src/dep_graph/prev.rs b/compiler/rustc_query_system/src/dep_graph/prev.rs
new file mode 100644
index 00000000000..29357ce9449
--- /dev/null
+++ b/compiler/rustc_query_system/src/dep_graph/prev.rs
@@ -0,0 +1,61 @@
+use super::serialized::{SerializedDepGraph, SerializedDepNodeIndex};
+use super::{DepKind, DepNode};
+use rustc_data_structures::fingerprint::Fingerprint;
+use rustc_data_structures::fx::FxHashMap;
+
+#[derive(Debug, Encodable, Decodable)]
+pub struct PreviousDepGraph<K: DepKind> {
+    data: SerializedDepGraph<K>,
+    index: FxHashMap<DepNode<K>, SerializedDepNodeIndex>,
+}
+
+impl<K: DepKind> Default for PreviousDepGraph<K> {
+    fn default() -> Self {
+        PreviousDepGraph { data: Default::default(), index: Default::default() }
+    }
+}
+
+impl<K: DepKind> PreviousDepGraph<K> {
+    pub fn new(data: SerializedDepGraph<K>) -> PreviousDepGraph<K> {
+        let index: FxHashMap<_, _> =
+            data.nodes.iter_enumerated().map(|(idx, &dep_node)| (dep_node, idx)).collect();
+        PreviousDepGraph { data, index }
+    }
+
+    #[inline]
+    pub fn edge_targets_from(
+        &self,
+        dep_node_index: SerializedDepNodeIndex,
+    ) -> &[SerializedDepNodeIndex] {
+        self.data.edge_targets_from(dep_node_index)
+    }
+
+    #[inline]
+    pub fn index_to_node(&self, dep_node_index: SerializedDepNodeIndex) -> DepNode<K> {
+        self.data.nodes[dep_node_index]
+    }
+
+    #[inline]
+    pub fn node_to_index(&self, dep_node: &DepNode<K>) -> SerializedDepNodeIndex {
+        self.index[dep_node]
+    }
+
+    #[inline]
+    pub fn node_to_index_opt(&self, dep_node: &DepNode<K>) -> Option<SerializedDepNodeIndex> {
+        self.index.get(dep_node).cloned()
+    }
+
+    #[inline]
+    pub fn fingerprint_of(&self, dep_node: &DepNode<K>) -> Option<Fingerprint> {
+        self.index.get(dep_node).map(|&node_index| self.data.fingerprints[node_index])
+    }
+
+    #[inline]
+    pub fn fingerprint_by_index(&self, dep_node_index: SerializedDepNodeIndex) -> Fingerprint {
+        self.data.fingerprints[dep_node_index]
+    }
+
+    pub fn node_count(&self) -> usize {
+        self.index.len()
+    }
+}