From c23a457e72abe608715ac76f076f47dc42af07a5 Mon Sep 17 00:00:00 2001
From: Daniel Baumann <daniel.baumann@progress-linux.org>
Date: Thu, 30 May 2024 20:31:44 +0200
Subject: Merging upstream version 1.74.1+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
---
 compiler/rustc_query_system/src/dep_graph/debug.rs |  14 +-
 .../rustc_query_system/src/dep_graph/dep_node.rs   |  92 ++++-
 compiler/rustc_query_system/src/dep_graph/edges.rs |  73 ++++
 compiler/rustc_query_system/src/dep_graph/graph.rs | 202 +++++-----
 compiler/rustc_query_system/src/dep_graph/mod.rs   |  80 ++--
 compiler/rustc_query_system/src/dep_graph/query.rs |  22 +-
 .../rustc_query_system/src/dep_graph/serialized.rs | 412 ++++++++++++++++++---
 7 files changed, 649 insertions(+), 246 deletions(-)
 create mode 100644 compiler/rustc_query_system/src/dep_graph/edges.rs

(limited to 'compiler/rustc_query_system/src/dep_graph')

diff --git a/compiler/rustc_query_system/src/dep_graph/debug.rs b/compiler/rustc_query_system/src/dep_graph/debug.rs
index c2c9600f5..103a6c01b 100644
--- a/compiler/rustc_query_system/src/dep_graph/debug.rs
+++ b/compiler/rustc_query_system/src/dep_graph/debug.rs
@@ -1,6 +1,6 @@
 //! Code for debugging the dep-graph.
 
-use super::{DepKind, DepNode, DepNodeIndex};
+use super::{DepNode, DepNodeIndex};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sync::Lock;
 use std::error::Error;
@@ -28,7 +28,7 @@ impl DepNodeFilter {
     }
 
     /// Tests whether `node` meets the filter, returning true if so.
-    pub fn test<K: DepKind>(&self, node: &DepNode<K>) -> bool {
+    pub fn test(&self, node: &DepNode) -> bool {
         let debug_str = format!("{node:?}");
         self.text.split('&').map(|s| s.trim()).all(|f| debug_str.contains(f))
     }
@@ -36,14 +36,14 @@ impl DepNodeFilter {
 
 /// A filter like `F -> G` where `F` and `G` are valid dep-node
 /// filters. This can be used to test the source/target independently.
-pub struct EdgeFilter<K: DepKind> {
+pub struct EdgeFilter {
     pub source: DepNodeFilter,
     pub target: DepNodeFilter,
-    pub index_to_node: Lock<FxHashMap<DepNodeIndex, DepNode<K>>>,
+    pub index_to_node: Lock<FxHashMap<DepNodeIndex, DepNode>>,
 }
 
-impl<K: DepKind> EdgeFilter<K> {
-    pub fn new(test: &str) -> Result<EdgeFilter<K>, Box<dyn Error>> {
+impl EdgeFilter {
+    pub fn new(test: &str) -> Result<EdgeFilter, Box<dyn Error>> {
         let parts: Vec<_> = test.split("->").collect();
         if parts.len() != 2 {
             Err(format!("expected a filter like `a&b -> c&d`, not `{test}`").into())
@@ -57,7 +57,7 @@ impl<K: DepKind> EdgeFilter<K> {
     }
 
     #[cfg(debug_assertions)]
-    pub fn test(&self, source: &DepNode<K>, target: &DepNode<K>) -> bool {
+    pub fn test(&self, source: &DepNode, target: &DepNode) -> bool {
         self.source.test(source) && self.target.test(target)
     }
 }
diff --git a/compiler/rustc_query_system/src/dep_graph/dep_node.rs b/compiler/rustc_query_system/src/dep_graph/dep_node.rs
index 39a4cb1b1..17f96896a 100644
--- a/compiler/rustc_query_system/src/dep_graph/dep_node.rs
+++ b/compiler/rustc_query_system/src/dep_graph/dep_node.rs
@@ -42,36 +42,84 @@
 //!   `DefId` it was computed from. In other cases, too much information gets
 //!   lost during fingerprint computation.
 
-use super::{DepContext, DepKind, FingerprintStyle};
+use super::{DepContext, FingerprintStyle};
 use crate::ich::StableHashingContext;
 
 use rustc_data_structures::fingerprint::{Fingerprint, PackedFingerprint};
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher, StableOrd, ToStableHashKey};
+use rustc_data_structures::AtomicRef;
 use rustc_hir::definitions::DefPathHash;
 use std::fmt;
 use std::hash::Hash;
 
-#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Encodable, Decodable)]
-pub struct DepNode<K> {
-    pub kind: K,
+/// This serves as an index into arrays built by `make_dep_kind_array`.
+#[derive(Clone, Copy, PartialEq, Eq, Hash)]
+pub struct DepKind {
+    variant: u16,
+}
+
+impl DepKind {
+    #[inline]
+    pub const fn new(variant: u16) -> Self {
+        Self { variant }
+    }
+
+    #[inline]
+    pub const fn as_inner(&self) -> u16 {
+        self.variant
+    }
+
+    #[inline]
+    pub const fn as_usize(&self) -> usize {
+        self.variant as usize
+    }
+}
+
+static_assert_size!(DepKind, 2);
+
+pub fn default_dep_kind_debug(kind: DepKind, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+    f.debug_struct("DepKind").field("variant", &kind.variant).finish()
+}
+
+pub static DEP_KIND_DEBUG: AtomicRef<fn(DepKind, &mut fmt::Formatter<'_>) -> fmt::Result> =
+    AtomicRef::new(&(default_dep_kind_debug as fn(_, &mut fmt::Formatter<'_>) -> _));
+
+impl fmt::Debug for DepKind {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        (*DEP_KIND_DEBUG)(*self, f)
+    }
+}
+
+#[derive(Clone, Copy, PartialEq, Eq, Hash)]
+pub struct DepNode {
+    pub kind: DepKind,
     pub hash: PackedFingerprint,
 }
 
-impl<K: DepKind> DepNode<K> {
+// We keep a lot of `DepNode`s in memory during compilation. It's not
+// required that their size stay the same, but we don't want to change
+// it inadvertently. This assert just ensures we're aware of any change.
+#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
+static_assert_size!(DepNode, 18);
+
+#[cfg(not(any(target_arch = "x86", target_arch = "x86_64")))]
+static_assert_size!(DepNode, 24);
+
+impl DepNode {
     /// Creates a new, parameterless DepNode. This method will assert
     /// that the DepNode corresponding to the given DepKind actually
     /// does not require any parameters.
-    pub fn new_no_params<Tcx>(tcx: Tcx, kind: K) -> DepNode<K>
+    pub fn new_no_params<Tcx>(tcx: Tcx, kind: DepKind) -> DepNode
     where
-        Tcx: super::DepContext<DepKind = K>,
+        Tcx: super::DepContext,
     {
         debug_assert_eq!(tcx.fingerprint_style(kind), FingerprintStyle::Unit);
         DepNode { kind, hash: Fingerprint::ZERO.into() }
     }
 
-    pub fn construct<Tcx, Key>(tcx: Tcx, kind: K, arg: &Key) -> DepNode<K>
+    pub fn construct<Tcx, Key>(tcx: Tcx, kind: DepKind, arg: &Key) -> DepNode
     where
-        Tcx: super::DepContext<DepKind = K>,
+        Tcx: super::DepContext,
         Key: DepNodeParams<Tcx>,
     {
         let hash = arg.to_fingerprint(tcx);
@@ -93,18 +141,25 @@ impl<K: DepKind> DepNode<K> {
     /// Construct a DepNode from the given DepKind and DefPathHash. This
     /// method will assert that the given DepKind actually requires a
     /// single DefId/DefPathHash parameter.
-    pub fn from_def_path_hash<Tcx>(tcx: Tcx, def_path_hash: DefPathHash, kind: K) -> Self
+    pub fn from_def_path_hash<Tcx>(tcx: Tcx, def_path_hash: DefPathHash, kind: DepKind) -> Self
     where
-        Tcx: super::DepContext<DepKind = K>,
+        Tcx: super::DepContext,
     {
         debug_assert!(tcx.fingerprint_style(kind) == FingerprintStyle::DefPathHash);
         DepNode { kind, hash: def_path_hash.0.into() }
     }
 }
 
-impl<K: DepKind> fmt::Debug for DepNode<K> {
+pub fn default_dep_node_debug(node: DepNode, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+    f.debug_struct("DepNode").field("kind", &node.kind).field("hash", &node.hash).finish()
+}
+
+pub static DEP_NODE_DEBUG: AtomicRef<fn(DepNode, &mut fmt::Formatter<'_>) -> fmt::Result> =
+    AtomicRef::new(&(default_dep_node_debug as fn(_, &mut fmt::Formatter<'_>) -> _));
+
+impl fmt::Debug for DepNode {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        K::debug_node(self, f)
+        (*DEP_NODE_DEBUG)(*self, f)
     }
 }
 
@@ -129,7 +184,7 @@ pub trait DepNodeParams<Tcx: DepContext>: fmt::Debug + Sized {
     /// `fingerprint_style()` is not `FingerprintStyle::Opaque`.
     /// It is always valid to return `None` here, in which case incremental
     /// compilation will treat the query as having changed instead of forcing it.
-    fn recover(tcx: Tcx, dep_node: &DepNode<Tcx::DepKind>) -> Option<Self>;
+    fn recover(tcx: Tcx, dep_node: &DepNode) -> Option<Self>;
 }
 
 impl<Tcx: DepContext, T> DepNodeParams<Tcx> for T
@@ -156,7 +211,7 @@ where
     }
 
     #[inline(always)]
-    default fn recover(_: Tcx, _: &DepNode<Tcx::DepKind>) -> Option<Self> {
+    default fn recover(_: Tcx, _: &DepNode) -> Option<Self> {
         None
     }
 }
@@ -216,10 +271,13 @@ pub struct DepKindStruct<Tcx: DepContext> {
     /// with kind `MirValidated`, we know that the GUID/fingerprint of the `DepNode`
     /// is actually a `DefPathHash`, and can therefore just look up the corresponding
     /// `DefId` in `tcx.def_path_hash_to_def_id`.
-    pub force_from_dep_node: Option<fn(tcx: Tcx, dep_node: DepNode<Tcx::DepKind>) -> bool>,
+    pub force_from_dep_node: Option<fn(tcx: Tcx, dep_node: DepNode) -> bool>,
 
     /// Invoke a query to put the on-disk cached value in memory.
-    pub try_load_from_on_disk_cache: Option<fn(Tcx, DepNode<Tcx::DepKind>)>,
+    pub try_load_from_on_disk_cache: Option<fn(Tcx, DepNode)>,
+
+    /// The name of this dep kind.
+    pub name: &'static &'static str,
 }
 
 /// A "work product" corresponds to a `.o` (or other) file that we
diff --git a/compiler/rustc_query_system/src/dep_graph/edges.rs b/compiler/rustc_query_system/src/dep_graph/edges.rs
new file mode 100644
index 000000000..6ba3924f6
--- /dev/null
+++ b/compiler/rustc_query_system/src/dep_graph/edges.rs
@@ -0,0 +1,73 @@
+use crate::dep_graph::DepNodeIndex;
+use smallvec::SmallVec;
+use std::hash::{Hash, Hasher};
+use std::iter::Extend;
+use std::ops::Deref;
+
+#[derive(Default, Debug)]
+pub struct EdgesVec {
+    max: u32,
+    edges: SmallVec<[DepNodeIndex; EdgesVec::INLINE_CAPACITY]>,
+}
+
+impl Hash for EdgesVec {
+    #[inline]
+    fn hash<H: Hasher>(&self, hasher: &mut H) {
+        Hash::hash(&self.edges, hasher)
+    }
+}
+
+impl EdgesVec {
+    pub const INLINE_CAPACITY: usize = 8;
+
+    #[inline]
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    #[inline]
+    pub fn push(&mut self, edge: DepNodeIndex) {
+        self.max = self.max.max(edge.as_u32());
+        self.edges.push(edge);
+    }
+
+    #[inline]
+    pub fn max_index(&self) -> u32 {
+        self.max
+    }
+}
+
+impl Deref for EdgesVec {
+    type Target = [DepNodeIndex];
+
+    #[inline]
+    fn deref(&self) -> &Self::Target {
+        self.edges.as_slice()
+    }
+}
+
+impl FromIterator<DepNodeIndex> for EdgesVec {
+    #[inline]
+    fn from_iter<T>(iter: T) -> Self
+    where
+        T: IntoIterator<Item = DepNodeIndex>,
+    {
+        let mut vec = EdgesVec::new();
+        for index in iter {
+            vec.push(index)
+        }
+        vec
+    }
+}
+
+impl Extend<DepNodeIndex> for EdgesVec {
+    #[inline]
+    fn extend<T>(&mut self, iter: T)
+    where
+        T: IntoIterator<Item = DepNodeIndex>,
+    {
+        for elem in iter {
+            self.push(elem);
+        }
+    }
+}
diff --git a/compiler/rustc_query_system/src/dep_graph/graph.rs b/compiler/rustc_query_system/src/dep_graph/graph.rs
index 30422ea11..c7e92d7b2 100644
--- a/compiler/rustc_query_system/src/dep_graph/graph.rs
+++ b/compiler/rustc_query_system/src/dep_graph/graph.rs
@@ -8,7 +8,6 @@ use rustc_data_structures::sync::{AtomicU32, AtomicU64, Lock, Lrc, Ordering};
 use rustc_data_structures::unord::UnordMap;
 use rustc_index::IndexVec;
 use rustc_serialize::opaque::{FileEncodeResult, FileEncoder};
-use smallvec::{smallvec, SmallVec};
 use std::assert_matches::assert_matches;
 use std::collections::hash_map::Entry;
 use std::fmt::Debug;
@@ -18,7 +17,8 @@ use std::sync::atomic::Ordering::Relaxed;
 
 use super::query::DepGraphQuery;
 use super::serialized::{GraphEncoder, SerializedDepGraph, SerializedDepNodeIndex};
-use super::{DepContext, DepKind, DepNode, HasDepContext, WorkProductId};
+use super::{DepContext, DepKind, DepNode, Deps, HasDepContext, WorkProductId};
+use crate::dep_graph::EdgesVec;
 use crate::ich::StableHashingContext;
 use crate::query::{QueryContext, QuerySideEffects};
 
@@ -26,8 +26,8 @@ use crate::query::{QueryContext, QuerySideEffects};
 use {super::debug::EdgeFilter, std::env};
 
 #[derive(Clone)]
-pub struct DepGraph<K: DepKind> {
-    data: Option<Lrc<DepGraphData<K>>>,
+pub struct DepGraph<D: Deps> {
+    data: Option<Lrc<DepGraphData<D>>>,
 
     /// This field is used for assigning DepNodeIndices when running in
     /// non-incremental mode. Even in non-incremental mode we make sure that
@@ -74,16 +74,16 @@ impl DepNodeColor {
     }
 }
 
-pub struct DepGraphData<K: DepKind> {
+pub struct DepGraphData<D: Deps> {
     /// The new encoding of the dependency graph, optimized for red/green
     /// tracking. The `current` field is the dependency graph of only the
     /// current compilation session: We don't merge the previous dep-graph into
     /// current one anymore, but we do reference shared data to save space.
-    current: CurrentDepGraph<K>,
+    current: CurrentDepGraph<D>,
 
     /// The dep-graph from the previous compilation session. It contains all
     /// nodes and edges as well as all fingerprints of nodes that have them.
-    previous: SerializedDepGraph<K>,
+    previous: SerializedDepGraph,
 
     colors: DepNodeColorMap,
 
@@ -95,12 +95,12 @@ pub struct DepGraphData<K: DepKind> {
     /// this map. We can later look for and extract that data.
     previous_work_products: WorkProductMap,
 
-    dep_node_debug: Lock<FxHashMap<DepNode<K>, String>>,
+    dep_node_debug: Lock<FxHashMap<DepNode, 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>>>,
+    debug_loaded_from_disk: Lock<FxHashSet<DepNode>>,
 }
 
 pub fn hash_result<R>(hcx: &mut StableHashingContext<'_>, result: &R) -> Fingerprint
@@ -112,15 +112,15 @@ where
     stable_hasher.finish()
 }
 
-impl<K: DepKind> DepGraph<K> {
+impl<D: Deps> DepGraph<D> {
     pub fn new(
         profiler: &SelfProfilerRef,
-        prev_graph: SerializedDepGraph<K>,
+        prev_graph: SerializedDepGraph,
         prev_work_products: WorkProductMap,
         encoder: FileEncoder,
         record_graph: bool,
         record_stats: bool,
-    ) -> DepGraph<K> {
+    ) -> DepGraph<D> {
         let prev_graph_node_count = prev_graph.node_count();
 
         let current = CurrentDepGraph::new(
@@ -136,8 +136,8 @@ impl<K: DepKind> DepGraph<K> {
         // Instantiate a dependy-less node only once for anonymous queries.
         let _green_node_index = current.intern_new_node(
             profiler,
-            DepNode { kind: DepKind::NULL, hash: current.anon_id_seed.into() },
-            smallvec![],
+            DepNode { kind: D::DEP_KIND_NULL, hash: current.anon_id_seed.into() },
+            EdgesVec::new(),
             Fingerprint::ZERO,
         );
         assert_eq!(_green_node_index, DepNodeIndex::SINGLETON_DEPENDENCYLESS_ANON_NODE);
@@ -146,8 +146,8 @@ impl<K: DepKind> DepGraph<K> {
         let (red_node_index, red_node_prev_index_and_color) = current.intern_node(
             profiler,
             &prev_graph,
-            DepNode { kind: DepKind::RED, hash: Fingerprint::ZERO.into() },
-            smallvec![],
+            DepNode { kind: D::DEP_KIND_RED, hash: Fingerprint::ZERO.into() },
+            EdgesVec::new(),
             None,
             false,
         );
@@ -181,12 +181,12 @@ impl<K: DepKind> DepGraph<K> {
         }
     }
 
-    pub fn new_disabled() -> DepGraph<K> {
+    pub fn new_disabled() -> DepGraph<D> {
         DepGraph { data: None, virtual_dep_node_index: Lrc::new(AtomicU32::new(0)) }
     }
 
     #[inline]
-    pub fn data(&self) -> Option<&DepGraphData<K>> {
+    pub fn data(&self) -> Option<&DepGraphData<D>> {
         self.data.as_deref()
     }
 
@@ -196,7 +196,7 @@ impl<K: DepKind> DepGraph<K> {
         self.data.is_some()
     }
 
-    pub fn with_query(&self, f: impl Fn(&DepGraphQuery<K>)) {
+    pub fn with_query(&self, f: impl Fn(&DepGraphQuery)) {
         if let Some(data) = &self.data {
             data.current.encoder.borrow().with_query(f)
         }
@@ -204,7 +204,7 @@ impl<K: DepKind> DepGraph<K> {
 
     pub fn assert_ignored(&self) {
         if let Some(..) = self.data {
-            K::read_deps(|task_deps| {
+            D::read_deps(|task_deps| {
                 assert_matches!(
                     task_deps,
                     TaskDepsRef::Ignore,
@@ -218,7 +218,7 @@ impl<K: DepKind> DepGraph<K> {
     where
         OP: FnOnce() -> R,
     {
-        K::with_deps(TaskDepsRef::Ignore, op)
+        D::with_deps(TaskDepsRef::Ignore, op)
     }
 
     /// Used to wrap the deserialization of a query result from disk,
@@ -271,13 +271,13 @@ impl<K: DepKind> DepGraph<K> {
     where
         OP: FnOnce() -> R,
     {
-        K::with_deps(TaskDepsRef::Forbid, op)
+        D::with_deps(TaskDepsRef::Forbid, op)
     }
 
     #[inline(always)]
-    pub fn with_task<Ctxt: HasDepContext<DepKind = K>, A: Debug, R>(
+    pub fn with_task<Ctxt: HasDepContext<Deps = D>, A: Debug, R>(
         &self,
-        key: DepNode<K>,
+        key: DepNode,
         cx: Ctxt,
         arg: A,
         task: fn(Ctxt, A) -> R,
@@ -289,10 +289,10 @@ impl<K: DepKind> DepGraph<K> {
         }
     }
 
-    pub fn with_anon_task<Tcx: DepContext<DepKind = K>, OP, R>(
+    pub fn with_anon_task<Tcx: DepContext<Deps = D>, OP, R>(
         &self,
         cx: Tcx,
-        dep_kind: K,
+        dep_kind: DepKind,
         op: OP,
     ) -> (R, DepNodeIndex)
     where
@@ -305,7 +305,7 @@ impl<K: DepKind> DepGraph<K> {
     }
 }
 
-impl<K: DepKind> DepGraphData<K> {
+impl<D: Deps> DepGraphData<D> {
     /// Starts a new dep-graph task. Dep-graph tasks are specified
     /// using a free function (`task`) and **not** a closure -- this
     /// is intentional because we want to exercise tight control over
@@ -334,9 +334,9 @@ impl<K: DepKind> DepGraphData<K> {
     ///
     /// [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/incremental-compilation.html
     #[inline(always)]
-    pub fn with_task<Ctxt: HasDepContext<DepKind = K>, A: Debug, R>(
+    pub fn with_task<Ctxt: HasDepContext<Deps = D>, A: Debug, R>(
         &self,
-        key: DepNode<K>,
+        key: DepNode,
         cx: Ctxt,
         arg: A,
         task: fn(Ctxt, A) -> R,
@@ -354,14 +354,14 @@ impl<K: DepKind> DepGraphData<K> {
                  - dep-node: {key:?}"
         );
 
-        let with_deps = |task_deps| K::with_deps(task_deps, || task(cx, arg));
+        let with_deps = |task_deps| D::with_deps(task_deps, || task(cx, arg));
         let (result, edges) = if cx.dep_context().is_eval_always(key.kind) {
-            (with_deps(TaskDepsRef::EvalAlways), smallvec![])
+            (with_deps(TaskDepsRef::EvalAlways), EdgesVec::new())
         } else {
             let task_deps = Lock::new(TaskDeps {
                 #[cfg(debug_assertions)]
                 node: Some(key),
-                reads: SmallVec::new(),
+                reads: EdgesVec::new(),
                 read_set: Default::default(),
                 phantom_data: PhantomData,
             });
@@ -402,10 +402,10 @@ impl<K: DepKind> DepGraphData<K> {
 
     /// Executes something within an "anonymous" task, that is, a task the
     /// `DepNode` of which is determined by the list of inputs it read from.
-    pub fn with_anon_task<Tcx: DepContext<DepKind = K>, OP, R>(
+    pub fn with_anon_task<Tcx: DepContext<Deps = D>, OP, R>(
         &self,
         cx: Tcx,
-        dep_kind: K,
+        dep_kind: DepKind,
         op: OP,
     ) -> (R, DepNodeIndex)
     where
@@ -414,7 +414,7 @@ impl<K: DepKind> DepGraphData<K> {
         debug_assert!(!cx.is_eval_always(dep_kind));
 
         let task_deps = Lock::new(TaskDeps::default());
-        let result = K::with_deps(TaskDepsRef::Allow(&task_deps), op);
+        let result = D::with_deps(TaskDepsRef::Allow(&task_deps), op);
         let task_deps = task_deps.into_inner();
         let task_deps = task_deps.reads;
 
@@ -461,11 +461,11 @@ impl<K: DepKind> DepGraphData<K> {
     }
 }
 
-impl<K: DepKind> DepGraph<K> {
+impl<D: Deps> DepGraph<D> {
     #[inline]
     pub fn read_index(&self, dep_node_index: DepNodeIndex) {
         if let Some(ref data) = self.data {
-            K::read_deps(|task_deps| {
+            D::read_deps(|task_deps| {
                 let mut task_deps = match task_deps {
                     TaskDepsRef::Allow(deps) => deps.lock(),
                     TaskDepsRef::EvalAlways => {
@@ -486,14 +486,14 @@ impl<K: DepKind> DepGraph<K> {
 
                 // As long as we only have a low number of reads we can avoid doing a hash
                 // insert and potentially allocating/reallocating the hashmap
-                let new_read = if task_deps.reads.len() < TASK_DEPS_READS_CAP {
+                let new_read = if task_deps.reads.len() < EdgesVec::INLINE_CAPACITY {
                     task_deps.reads.iter().all(|other| *other != dep_node_index)
                 } else {
                     task_deps.read_set.insert(dep_node_index)
                 };
                 if new_read {
                     task_deps.reads.push(dep_node_index);
-                    if task_deps.reads.len() == TASK_DEPS_READS_CAP {
+                    if task_deps.reads.len() == EdgesVec::INLINE_CAPACITY {
                         // Fill `read_set` with what we have so far so we can use the hashset
                         // next time
                         task_deps.read_set.extend(task_deps.reads.iter().copied());
@@ -532,9 +532,9 @@ impl<K: DepKind> DepGraph<K> {
     /// FIXME: If the code is changed enough for this node to be marked before requiring the
     /// caller's node, we suppose that those changes will be enough to mark this node red and
     /// force a recomputation using the "normal" way.
-    pub fn with_feed_task<Ctxt: DepContext<DepKind = K>, A: Debug, R: Debug>(
+    pub fn with_feed_task<Ctxt: DepContext<Deps = D>, A: Debug, R: Debug>(
         &self,
-        node: DepNode<K>,
+        node: DepNode,
         cx: Ctxt,
         key: A,
         result: &R,
@@ -572,8 +572,8 @@ impl<K: DepKind> DepGraph<K> {
                 }
             }
 
-            let mut edges = SmallVec::new();
-            K::read_deps(|task_deps| match task_deps {
+            let mut edges = EdgesVec::new();
+            D::read_deps(|task_deps| match task_deps {
                 TaskDepsRef::Allow(deps) => edges.extend(deps.lock().reads.iter().copied()),
                 TaskDepsRef::EvalAlways => {
                     edges.push(DepNodeIndex::FOREVER_RED_NODE);
@@ -623,27 +623,22 @@ impl<K: DepKind> DepGraph<K> {
     }
 }
 
-impl<K: DepKind> DepGraphData<K> {
+impl<D: Deps> DepGraphData<D> {
     #[inline]
-    pub fn dep_node_index_of_opt(&self, dep_node: &DepNode<K>) -> Option<DepNodeIndex> {
+    pub fn dep_node_index_of_opt(&self, dep_node: &DepNode) -> Option<DepNodeIndex> {
         if let Some(prev_index) = self.previous.node_to_index_opt(dep_node) {
             self.current.prev_index_to_index.lock()[prev_index]
         } else {
-            self.current
-                .new_node_to_index
-                .get_shard_by_value(dep_node)
-                .lock()
-                .get(dep_node)
-                .copied()
+            self.current.new_node_to_index.lock_shard_by_value(dep_node).get(dep_node).copied()
         }
     }
 
     #[inline]
-    pub fn dep_node_exists(&self, dep_node: &DepNode<K>) -> bool {
+    pub fn dep_node_exists(&self, dep_node: &DepNode) -> bool {
         self.dep_node_index_of_opt(dep_node).is_some()
     }
 
-    fn node_color(&self, dep_node: &DepNode<K>) -> Option<DepNodeColor> {
+    fn node_color(&self, dep_node: &DepNode) -> Option<DepNodeColor> {
         if let Some(prev_index) = self.previous.node_to_index_opt(dep_node) {
             self.colors.get(prev_index)
         } else {
@@ -665,18 +660,18 @@ impl<K: DepKind> DepGraphData<K> {
     }
 
     #[inline]
-    pub fn prev_node_of(&self, prev_index: SerializedDepNodeIndex) -> DepNode<K> {
+    pub fn prev_node_of(&self, prev_index: SerializedDepNodeIndex) -> DepNode {
         self.previous.index_to_node(prev_index)
     }
 
-    pub fn mark_debug_loaded_from_disk(&self, dep_node: DepNode<K>) {
+    pub fn mark_debug_loaded_from_disk(&self, dep_node: DepNode) {
         self.debug_loaded_from_disk.lock().insert(dep_node);
     }
 }
 
-impl<K: DepKind> DepGraph<K> {
+impl<D: Deps> DepGraph<D> {
     #[inline]
-    pub fn dep_node_exists(&self, dep_node: &DepNode<K>) -> bool {
+    pub fn dep_node_exists(&self, dep_node: &DepNode) -> bool {
         self.data.as_ref().is_some_and(|data| data.dep_node_exists(dep_node))
     }
 
@@ -692,12 +687,12 @@ impl<K: DepKind> DepGraph<K> {
         &self.data.as_ref().unwrap().previous_work_products
     }
 
-    pub fn debug_was_loaded_from_disk(&self, dep_node: DepNode<K>) -> bool {
+    pub fn debug_was_loaded_from_disk(&self, dep_node: DepNode) -> 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)
+    pub fn register_dep_node_debug_str<F>(&self, dep_node: DepNode, debug_str_gen: F)
     where
         F: FnOnce() -> String,
     {
@@ -710,11 +705,11 @@ impl<K: DepKind> DepGraph<K> {
         dep_node_debug.borrow_mut().insert(dep_node, debug_str);
     }
 
-    pub fn dep_node_debug_str(&self, dep_node: DepNode<K>) -> Option<String> {
+    pub fn dep_node_debug_str(&self, dep_node: DepNode) -> Option<String> {
         self.data.as_ref()?.dep_node_debug.borrow().get(&dep_node).cloned()
     }
 
-    fn node_color(&self, dep_node: &DepNode<K>) -> Option<DepNodeColor> {
+    fn node_color(&self, dep_node: &DepNode) -> Option<DepNodeColor> {
         if let Some(ref data) = self.data {
             return data.node_color(dep_node);
         }
@@ -722,25 +717,25 @@ impl<K: DepKind> DepGraph<K> {
         None
     }
 
-    pub fn try_mark_green<Qcx: QueryContext<DepKind = K>>(
+    pub fn try_mark_green<Qcx: QueryContext<Deps = D>>(
         &self,
         qcx: Qcx,
-        dep_node: &DepNode<K>,
+        dep_node: &DepNode,
     ) -> Option<(SerializedDepNodeIndex, DepNodeIndex)> {
         self.data().and_then(|data| data.try_mark_green(qcx, dep_node))
     }
 }
 
-impl<K: DepKind> DepGraphData<K> {
+impl<D: Deps> DepGraphData<D> {
     /// Try to mark a node index for the node dep_node.
     ///
     /// A node will have an index, when it's already been marked green, or when we can mark it
     /// green. This function will mark the current task as a reader of the specified node, when
     /// a node index can be found for that node.
-    pub fn try_mark_green<Qcx: QueryContext<DepKind = K>>(
+    pub fn try_mark_green<Qcx: QueryContext<Deps = D>>(
         &self,
         qcx: Qcx,
-        dep_node: &DepNode<K>,
+        dep_node: &DepNode,
     ) -> Option<(SerializedDepNodeIndex, DepNodeIndex)> {
         debug_assert!(!qcx.dep_context().is_eval_always(dep_node.kind));
 
@@ -762,11 +757,11 @@ impl<K: DepKind> DepGraphData<K> {
     }
 
     #[instrument(skip(self, qcx, parent_dep_node_index, frame), level = "debug")]
-    fn try_mark_parent_green<Qcx: QueryContext<DepKind = K>>(
+    fn try_mark_parent_green<Qcx: QueryContext<Deps = D>>(
         &self,
         qcx: Qcx,
         parent_dep_node_index: SerializedDepNodeIndex,
-        dep_node: &DepNode<K>,
+        dep_node: &DepNode,
         frame: Option<&MarkFrame<'_>>,
     ) -> Option<()> {
         let dep_dep_node_color = self.colors.get(parent_dep_node_index);
@@ -850,11 +845,11 @@ impl<K: DepKind> DepGraphData<K> {
 
     /// Try to mark a dep-node which existed in the previous compilation session as green.
     #[instrument(skip(self, qcx, prev_dep_node_index, frame), level = "debug")]
-    fn try_mark_previous_green<Qcx: QueryContext<DepKind = K>>(
+    fn try_mark_previous_green<Qcx: QueryContext<Deps = D>>(
         &self,
         qcx: Qcx,
         prev_dep_node_index: SerializedDepNodeIndex,
-        dep_node: &DepNode<K>,
+        dep_node: &DepNode,
         frame: Option<&MarkFrame<'_>>,
     ) -> Option<DepNodeIndex> {
         let frame = MarkFrame { index: prev_dep_node_index, parent: frame };
@@ -872,7 +867,7 @@ impl<K: DepKind> DepGraphData<K> {
 
         let prev_deps = self.previous.edge_targets_from(prev_dep_node_index);
 
-        for &dep_dep_node_index in prev_deps {
+        for dep_dep_node_index in prev_deps {
             self.try_mark_parent_green(qcx, dep_dep_node_index, dep_node, Some(&frame))?;
         }
 
@@ -921,7 +916,7 @@ impl<K: DepKind> DepGraphData<K> {
     /// This may be called concurrently on multiple threads for the same dep node.
     #[cold]
     #[inline(never)]
-    fn emit_side_effects<Qcx: QueryContext<DepKind = K>>(
+    fn emit_side_effects<Qcx: QueryContext<Deps = D>>(
         &self,
         qcx: Qcx,
         dep_node_index: DepNodeIndex,
@@ -945,16 +940,16 @@ impl<K: DepKind> DepGraphData<K> {
     }
 }
 
-impl<K: DepKind> DepGraph<K> {
+impl<D: Deps> DepGraph<D> {
     /// Returns true if the given node has been marked as red during the
     /// current compilation session. Used in various assertions
-    pub fn is_red(&self, dep_node: &DepNode<K>) -> bool {
+    pub fn is_red(&self, dep_node: &DepNode) -> bool {
         self.node_color(dep_node) == Some(DepNodeColor::Red)
     }
 
     /// Returns true if the given node has been marked as green during the
     /// current compilation session. Used in various assertions
-    pub fn is_green(&self, dep_node: &DepNode<K>) -> bool {
+    pub fn is_green(&self, dep_node: &DepNode) -> bool {
         self.node_color(dep_node).is_some_and(|c| c.is_green())
     }
 
@@ -966,7 +961,7 @@ impl<K: DepKind> DepGraph<K> {
     ///
     /// This method will only load queries that will end up in the disk cache.
     /// Other queries will not be executed.
-    pub fn exec_cache_promotions<Tcx: DepContext<DepKind = K>>(&self, tcx: Tcx) {
+    pub fn exec_cache_promotions<Tcx: DepContext>(&self, tcx: Tcx) {
         let _prof_timer = tcx.profiler().generic_activity("incr_comp_query_cache_promotion");
 
         let data = self.data.as_ref().unwrap();
@@ -1081,9 +1076,9 @@ rustc_index::newtype_index! {
 /// `new_node_to_index` and `data`, or `prev_index_to_index` and `data`. When
 /// manipulating both, we acquire `new_node_to_index` or `prev_index_to_index`
 /// first, and `data` second.
-pub(super) struct CurrentDepGraph<K: DepKind> {
-    encoder: Steal<GraphEncoder<K>>,
-    new_node_to_index: Sharded<FxHashMap<DepNode<K>, DepNodeIndex>>,
+pub(super) struct CurrentDepGraph<D: Deps> {
+    encoder: Steal<GraphEncoder<D>>,
+    new_node_to_index: Sharded<FxHashMap<DepNode, DepNodeIndex>>,
     prev_index_to_index: Lock<IndexVec<SerializedDepNodeIndex, Option<DepNodeIndex>>>,
 
     /// This is used to verify that fingerprints do not change between the creation of a node
@@ -1094,7 +1089,7 @@ pub(super) struct CurrentDepGraph<K: DepKind> {
     /// Used to trap when a specific edge is added to the graph.
     /// This is used for debug purposes and is only active with `debug_assertions`.
     #[cfg(debug_assertions)]
-    forbidden_edge: Option<EdgeFilter<K>>,
+    forbidden_edge: Option<EdgeFilter>,
 
     /// Anonymous `DepNode`s are nodes whose IDs we compute from the list of
     /// their edges. This has the beneficial side-effect that multiple anonymous
@@ -1121,14 +1116,14 @@ pub(super) struct CurrentDepGraph<K: DepKind> {
     node_intern_event_id: Option<EventId>,
 }
 
-impl<K: DepKind> CurrentDepGraph<K> {
+impl<D: Deps> CurrentDepGraph<D> {
     fn new(
         profiler: &SelfProfilerRef,
         prev_graph_node_count: usize,
         encoder: FileEncoder,
         record_graph: bool,
         record_stats: bool,
-    ) -> CurrentDepGraph<K> {
+    ) -> Self {
         use std::time::{SystemTime, UNIX_EPOCH};
 
         let duration = SystemTime::now().duration_since(UNIX_EPOCH).unwrap();
@@ -1166,7 +1161,7 @@ impl<K: DepKind> CurrentDepGraph<K> {
             )),
             new_node_to_index: Sharded::new(|| {
                 FxHashMap::with_capacity_and_hasher(
-                    new_node_count_estimate / sharded::SHARDS,
+                    new_node_count_estimate / sharded::shards(),
                     Default::default(),
                 )
             }),
@@ -1183,7 +1178,7 @@ impl<K: DepKind> CurrentDepGraph<K> {
     }
 
     #[cfg(debug_assertions)]
-    fn record_edge(&self, dep_node_index: DepNodeIndex, key: DepNode<K>, fingerprint: Fingerprint) {
+    fn record_edge(&self, dep_node_index: DepNodeIndex, key: DepNode, fingerprint: Fingerprint) {
         if let Some(forbidden_edge) = &self.forbidden_edge {
             forbidden_edge.index_to_node.lock().insert(dep_node_index, key);
         }
@@ -1197,12 +1192,11 @@ impl<K: DepKind> CurrentDepGraph<K> {
     fn intern_new_node(
         &self,
         profiler: &SelfProfilerRef,
-        key: DepNode<K>,
+        key: DepNode,
         edges: EdgesVec,
         current_fingerprint: Fingerprint,
     ) -> DepNodeIndex {
-        let dep_node_index = match self.new_node_to_index.get_shard_by_value(&key).lock().entry(key)
-        {
+        let dep_node_index = match self.new_node_to_index.lock_shard_by_value(&key).entry(key) {
             Entry::Occupied(entry) => *entry.get(),
             Entry::Vacant(entry) => {
                 let dep_node_index =
@@ -1221,8 +1215,8 @@ impl<K: DepKind> CurrentDepGraph<K> {
     fn intern_node(
         &self,
         profiler: &SelfProfilerRef,
-        prev_graph: &SerializedDepGraph<K>,
-        key: DepNode<K>,
+        prev_graph: &SerializedDepGraph,
+        key: DepNode,
         edges: EdgesVec,
         fingerprint: Option<Fingerprint>,
         print_status: bool,
@@ -1295,7 +1289,7 @@ impl<K: DepKind> CurrentDepGraph<K> {
     fn promote_node_and_deps_to_current(
         &self,
         profiler: &SelfProfilerRef,
-        prev_graph: &SerializedDepGraph<K>,
+        prev_graph: &SerializedDepGraph,
         prev_index: SerializedDepNodeIndex,
     ) -> DepNodeIndex {
         self.debug_assert_not_in_new_nodes(prev_graph, prev_index);
@@ -1308,8 +1302,7 @@ impl<K: DepKind> CurrentDepGraph<K> {
                 let key = prev_graph.index_to_node(prev_index);
                 let edges = prev_graph
                     .edge_targets_from(prev_index)
-                    .iter()
-                    .map(|i| prev_index_to_index[*i].unwrap())
+                    .map(|i| prev_index_to_index[i].unwrap())
                     .collect();
                 let fingerprint = prev_graph.fingerprint_by_index(prev_index);
                 let dep_node_index = self.encoder.borrow().send(profiler, key, fingerprint, edges);
@@ -1324,27 +1317,23 @@ impl<K: DepKind> CurrentDepGraph<K> {
     #[inline]
     fn debug_assert_not_in_new_nodes(
         &self,
-        prev_graph: &SerializedDepGraph<K>,
+        prev_graph: &SerializedDepGraph,
         prev_index: SerializedDepNodeIndex,
     ) {
         let node = &prev_graph.index_to_node(prev_index);
         debug_assert!(
-            !self.new_node_to_index.get_shard_by_value(node).lock().contains_key(node),
+            !self.new_node_to_index.lock_shard_by_value(node).contains_key(node),
             "node from previous graph present in new node collection"
         );
     }
 }
 
-/// The capacity of the `reads` field `SmallVec`
-const TASK_DEPS_READS_CAP: usize = 8;
-type EdgesVec = SmallVec<[DepNodeIndex; TASK_DEPS_READS_CAP]>;
-
 #[derive(Debug, Clone, Copy)]
-pub enum TaskDepsRef<'a, K: DepKind> {
+pub enum TaskDepsRef<'a> {
     /// New dependencies can be added to the
     /// `TaskDeps`. This is used when executing a 'normal' query
     /// (no `eval_always` modifier)
-    Allow(&'a Lock<TaskDeps<K>>),
+    Allow(&'a Lock<TaskDeps>),
     /// This is used when executing an `eval_always` query. We don't
     /// need to track dependencies for a query that's always
     /// re-executed -- but we need to know that this is an `eval_always`
@@ -1361,15 +1350,15 @@ pub enum TaskDepsRef<'a, K: DepKind> {
 }
 
 #[derive(Debug)]
-pub struct TaskDeps<K: DepKind> {
+pub struct TaskDeps {
     #[cfg(debug_assertions)]
-    node: Option<DepNode<K>>,
+    node: Option<DepNode>,
     reads: EdgesVec,
     read_set: FxHashSet<DepNodeIndex>,
-    phantom_data: PhantomData<DepNode<K>>,
+    phantom_data: PhantomData<DepNode>,
 }
 
-impl<K: DepKind> Default for TaskDeps<K> {
+impl Default for TaskDeps {
     fn default() -> Self {
         Self {
             #[cfg(debug_assertions)]
@@ -1421,10 +1410,7 @@ impl DepNodeColorMap {
 
 #[inline(never)]
 #[cold]
-pub(crate) fn print_markframe_trace<K: DepKind>(
-    graph: &DepGraph<K>,
-    frame: Option<&MarkFrame<'_>>,
-) {
+pub(crate) fn print_markframe_trace<D: Deps>(graph: &DepGraph<D>, frame: Option<&MarkFrame<'_>>) {
     let data = graph.data.as_ref().unwrap();
 
     eprintln!("there was a panic while trying to force a dep node");
diff --git a/compiler/rustc_query_system/src/dep_graph/mod.rs b/compiler/rustc_query_system/src/dep_graph/mod.rs
index 0fd9e35d6..624ae680a 100644
--- a/compiler/rustc_query_system/src/dep_graph/mod.rs
+++ b/compiler/rustc_query_system/src/dep_graph/mod.rs
@@ -1,10 +1,12 @@
 pub mod debug;
-mod dep_node;
+pub mod dep_node;
+mod edges;
 mod graph;
 mod query;
 mod serialized;
 
-pub use dep_node::{DepKindStruct, DepNode, DepNodeParams, WorkProductId};
+pub use dep_node::{DepKind, DepKindStruct, DepNode, DepNodeParams, WorkProductId};
+pub use edges::EdgesVec;
 pub use graph::{
     hash_result, DepGraph, DepGraphData, DepNodeColor, DepNodeIndex, TaskDeps, TaskDepsRef,
     WorkProduct, WorkProductMap,
@@ -14,22 +16,20 @@ pub use serialized::{SerializedDepGraph, SerializedDepNodeIndex};
 
 use crate::ich::StableHashingContext;
 use rustc_data_structures::profiling::SelfProfilerRef;
-use rustc_serialize::{opaque::FileEncoder, Encodable};
 use rustc_session::Session;
 
-use std::hash::Hash;
-use std::{fmt, panic};
+use std::panic;
 
 use self::graph::{print_markframe_trace, MarkFrame};
 
 pub trait DepContext: Copy {
-    type DepKind: self::DepKind;
+    type Deps: Deps;
 
     /// Create a hashing context for hashing new results.
     fn with_stable_hashing_context<R>(self, f: impl FnOnce(StableHashingContext<'_>) -> R) -> R;
 
     /// Access the DepGraph.
-    fn dep_graph(&self) -> &DepGraph<Self::DepKind>;
+    fn dep_graph(&self) -> &DepGraph<Self::Deps>;
 
     /// Access the profiler.
     fn profiler(&self) -> &SelfProfilerRef;
@@ -37,10 +37,10 @@ pub trait DepContext: Copy {
     /// Access the compiler session.
     fn sess(&self) -> &Session;
 
-    fn dep_kind_info(&self, dep_node: Self::DepKind) -> &DepKindStruct<Self>;
+    fn dep_kind_info(&self, dep_node: DepKind) -> &DepKindStruct<Self>;
 
     #[inline(always)]
-    fn fingerprint_style(self, kind: Self::DepKind) -> FingerprintStyle {
+    fn fingerprint_style(self, kind: DepKind) -> FingerprintStyle {
         let data = self.dep_kind_info(kind);
         if data.is_anon {
             return FingerprintStyle::Opaque;
@@ -50,18 +50,14 @@ pub trait DepContext: Copy {
 
     #[inline(always)]
     /// Return whether this kind always require evaluation.
-    fn is_eval_always(self, kind: Self::DepKind) -> bool {
+    fn is_eval_always(self, kind: DepKind) -> bool {
         self.dep_kind_info(kind).is_eval_always
     }
 
     /// Try to force a dep node to execute and see if it's green.
     #[inline]
     #[instrument(skip(self, frame), level = "debug")]
-    fn try_force_from_dep_node(
-        self,
-        dep_node: DepNode<Self::DepKind>,
-        frame: Option<&MarkFrame<'_>>,
-    ) -> bool {
+    fn try_force_from_dep_node(self, dep_node: DepNode, frame: Option<&MarkFrame<'_>>) -> bool {
         let cb = self.dep_kind_info(dep_node.kind);
         if let Some(f) = cb.force_from_dep_node {
             if let Err(value) = panic::catch_unwind(panic::AssertUnwindSafe(|| {
@@ -79,7 +75,7 @@ pub trait DepContext: Copy {
     }
 
     /// Load data from the on-disk cache.
-    fn try_load_from_on_disk_cache(self, dep_node: DepNode<Self::DepKind>) {
+    fn try_load_from_on_disk_cache(self, dep_node: DepNode) {
         let cb = self.dep_kind_info(dep_node.kind);
         if let Some(f) = cb.try_load_from_on_disk_cache {
             f(self, dep_node)
@@ -87,15 +83,37 @@ pub trait DepContext: Copy {
     }
 }
 
+pub trait Deps {
+    /// Execute the operation with provided dependencies.
+    fn with_deps<OP, R>(deps: TaskDepsRef<'_>, op: OP) -> R
+    where
+        OP: FnOnce() -> R;
+
+    /// Access dependencies from current implicit context.
+    fn read_deps<OP>(op: OP)
+    where
+        OP: for<'a> FnOnce(TaskDepsRef<'a>);
+
+    /// We use this for most things when incr. comp. is turned off.
+    const DEP_KIND_NULL: DepKind;
+
+    /// We use this to create a forever-red node.
+    const DEP_KIND_RED: DepKind;
+
+    /// This is the highest value a `DepKind` can have. It's used during encoding to
+    /// pack information into the unused bits.
+    const DEP_KIND_MAX: u16;
+}
+
 pub trait HasDepContext: Copy {
-    type DepKind: self::DepKind;
-    type DepContext: self::DepContext<DepKind = Self::DepKind>;
+    type Deps: self::Deps;
+    type DepContext: self::DepContext<Deps = Self::Deps>;
 
     fn dep_context(&self) -> &Self::DepContext;
 }
 
 impl<T: DepContext> HasDepContext for T {
-    type DepKind = T::DepKind;
+    type Deps = T::Deps;
     type DepContext = Self;
 
     fn dep_context(&self) -> &Self::DepContext {
@@ -104,7 +122,7 @@ impl<T: DepContext> HasDepContext for T {
 }
 
 impl<T: HasDepContext, Q: Copy> HasDepContext for (T, Q) {
-    type DepKind = T::DepKind;
+    type Deps = T::Deps;
     type DepContext = T::DepContext;
 
     fn dep_context(&self) -> &Self::DepContext {
@@ -136,25 +154,3 @@ impl FingerprintStyle {
         }
     }
 }
-
-/// Describe the different families of dependency nodes.
-pub trait DepKind: Copy + fmt::Debug + Eq + Hash + Send + Encodable<FileEncoder> + 'static {
-    /// DepKind to use when incr. comp. is turned off.
-    const NULL: Self;
-
-    /// DepKind to use to create the initial forever-red node.
-    const RED: Self;
-
-    /// Implementation of `std::fmt::Debug` for `DepNode`.
-    fn debug_node(node: &DepNode<Self>, f: &mut fmt::Formatter<'_>) -> fmt::Result;
-
-    /// Execute the operation with provided dependencies.
-    fn with_deps<OP, R>(deps: TaskDepsRef<'_, Self>, op: OP) -> R
-    where
-        OP: FnOnce() -> R;
-
-    /// Access dependencies from current implicit context.
-    fn read_deps<OP>(op: OP)
-    where
-        OP: for<'a> FnOnce(TaskDepsRef<'a, Self>);
-}
diff --git a/compiler/rustc_query_system/src/dep_graph/query.rs b/compiler/rustc_query_system/src/dep_graph/query.rs
index 5cbc6bf8f..5969e5fbe 100644
--- a/compiler/rustc_query_system/src/dep_graph/query.rs
+++ b/compiler/rustc_query_system/src/dep_graph/query.rs
@@ -2,16 +2,16 @@ use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::graph::implementation::{Direction, Graph, NodeIndex, INCOMING};
 use rustc_index::IndexVec;
 
-use super::{DepKind, DepNode, DepNodeIndex};
+use super::{DepNode, DepNodeIndex};
 
-pub struct DepGraphQuery<K> {
-    pub graph: Graph<DepNode<K>, ()>,
-    pub indices: FxHashMap<DepNode<K>, NodeIndex>,
+pub struct DepGraphQuery {
+    pub graph: Graph<DepNode, ()>,
+    pub indices: FxHashMap<DepNode, NodeIndex>,
     pub dep_index_to_index: IndexVec<DepNodeIndex, Option<NodeIndex>>,
 }
 
-impl<K: DepKind> DepGraphQuery<K> {
-    pub fn new(prev_node_count: usize) -> DepGraphQuery<K> {
+impl DepGraphQuery {
+    pub fn new(prev_node_count: usize) -> DepGraphQuery {
         let node_count = prev_node_count + prev_node_count / 4;
         let edge_count = 6 * node_count;
 
@@ -22,7 +22,7 @@ impl<K: DepKind> DepGraphQuery<K> {
         DepGraphQuery { graph, indices, dep_index_to_index }
     }
 
-    pub fn push(&mut self, index: DepNodeIndex, node: DepNode<K>, edges: &[DepNodeIndex]) {
+    pub fn push(&mut self, index: DepNodeIndex, node: DepNode, edges: &[DepNodeIndex]) {
         let source = self.graph.add_node(node);
         self.dep_index_to_index.insert(index, source);
         self.indices.insert(node, source);
@@ -37,11 +37,11 @@ impl<K: DepKind> DepGraphQuery<K> {
         }
     }
 
-    pub fn nodes(&self) -> Vec<&DepNode<K>> {
+    pub fn nodes(&self) -> Vec<&DepNode> {
         self.graph.all_nodes().iter().map(|n| &n.data).collect()
     }
 
-    pub fn edges(&self) -> Vec<(&DepNode<K>, &DepNode<K>)> {
+    pub fn edges(&self) -> Vec<(&DepNode, &DepNode)> {
         self.graph
             .all_edges()
             .iter()
@@ -50,7 +50,7 @@ impl<K: DepKind> DepGraphQuery<K> {
             .collect()
     }
 
-    fn reachable_nodes(&self, node: &DepNode<K>, direction: Direction) -> Vec<&DepNode<K>> {
+    fn reachable_nodes(&self, node: &DepNode, direction: Direction) -> Vec<&DepNode> {
         if let Some(&index) = self.indices.get(node) {
             self.graph.depth_traverse(index, direction).map(|s| self.graph.node_data(s)).collect()
         } else {
@@ -59,7 +59,7 @@ impl<K: DepKind> DepGraphQuery<K> {
     }
 
     /// All nodes that can reach `node`.
-    pub fn transitive_predecessors(&self, node: &DepNode<K>) -> Vec<&DepNode<K>> {
+    pub fn transitive_predecessors(&self, node: &DepNode) -> Vec<&DepNode> {
         self.reachable_nodes(node, INCOMING)
     }
 }
diff --git a/compiler/rustc_query_system/src/dep_graph/serialized.rs b/compiler/rustc_query_system/src/dep_graph/serialized.rs
index edddfda62..fcf46be6e 100644
--- a/compiler/rustc_query_system/src/dep_graph/serialized.rs
+++ b/compiler/rustc_query_system/src/dep_graph/serialized.rs
@@ -1,6 +1,6 @@
 //! The data that we will serialize and deserialize.
 //!
-//! The dep-graph is serialized as a sequence of NodeInfo, with the dependencies
+//! Notionally, the dep-graph is a sequence of NodeInfo with the dependencies
 //! specified inline. The total number of nodes and edges are stored as the last
 //! 16 bytes of the file, so we can find them easily at decoding time.
 //!
@@ -11,17 +11,44 @@
 //! sequence of NodeInfos to the different arrays in SerializedDepGraph. Since the
 //! node and edge count are stored at the end of the file, all the arrays can be
 //! pre-allocated with the right length.
+//!
+//! The encoding of the de-pgraph is generally designed around the fact that fixed-size
+//! reads of encoded data are generally faster than variable-sized reads. Ergo we adopt
+//! essentially the same varint encoding scheme used in the rmeta format; the edge lists
+//! for each node on the graph store a 2-bit integer which is the number of bytes per edge
+//! index in that node's edge list. We effectively ignore that an edge index of 0 could be
+//! encoded with 0 bytes in order to not require 3 bits to store the byte width of the edges.
+//! The overhead of calculating the correct byte width for each edge is mitigated by
+//! building edge lists with [`EdgesVec`] which keeps a running max of the edges in a node.
+//!
+//! When we decode this data, we do not immediately create [`SerializedDepNodeIndex`] and
+//! instead keep the data in its denser serialized form which lets us turn our on-disk size
+//! efficiency directly into a peak memory reduction. When we convert these encoded-in-memory
+//! values into their fully-deserialized type, we use a fixed-size read of the encoded array
+//! then mask off any errant bytes we read. The array of edge index bytes is padded to permit this.
+//!
+//! We also encode and decode the entire rest of each node using [`SerializedNodeHeader`]
+//! to let this encoding and decoding be done in one fixed-size operation. These headers contain
+//! two [`Fingerprint`]s along with the serialized [`DepKind`], and the number of edge indices
+//! in the node and the number of bytes used to encode the edge indices for this node. The
+//! [`DepKind`], number of edges, and bytes per edge are all bit-packed together, if they fit.
+//! If the number of edges in this node does not fit in the bits available in the header, we
+//! store it directly after the header with leb128.
 
 use super::query::DepGraphQuery;
-use super::{DepKind, DepNode, DepNodeIndex};
+use super::{DepKind, DepNode, DepNodeIndex, Deps};
+use crate::dep_graph::EdgesVec;
 use rustc_data_structures::fingerprint::Fingerprint;
+use rustc_data_structures::fingerprint::PackedFingerprint;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::profiling::SelfProfilerRef;
 use rustc_data_structures::sync::Lock;
+use rustc_data_structures::unhash::UnhashMap;
 use rustc_index::{Idx, IndexVec};
 use rustc_serialize::opaque::{FileEncodeResult, FileEncoder, IntEncodedWithFixedSize, MemDecoder};
-use rustc_serialize::{Decodable, Decoder, Encodable};
-use smallvec::SmallVec;
+use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
+use std::iter;
+use std::marker::PhantomData;
 
 // The maximum value of `SerializedDepNodeIndex` leaves the upper two bits
 // unused so that we can store multiple index types in `CompressedHybridIndex`,
@@ -31,26 +58,37 @@ rustc_index::newtype_index! {
     pub struct SerializedDepNodeIndex {}
 }
 
+const DEP_NODE_SIZE: usize = std::mem::size_of::<SerializedDepNodeIndex>();
+/// Amount of padding we need to add to the edge list data so that we can retrieve every
+/// SerializedDepNodeIndex with a fixed-size read then mask.
+const DEP_NODE_PAD: usize = DEP_NODE_SIZE - 1;
+/// Number of bits we need to store the number of used bytes in a SerializedDepNodeIndex.
+/// Note that wherever we encode byte widths like this we actually store the number of bytes used
+/// minus 1; for a 4-byte value we technically would have 5 widths to store, but using one byte to
+/// store zeroes (which are relatively rare) is a decent tradeoff to save a bit in our bitfields.
+const DEP_NODE_WIDTH_BITS: usize = DEP_NODE_SIZE / 2;
+
 /// Data for use when recompiling the **current crate**.
 #[derive(Debug)]
-pub struct SerializedDepGraph<K: DepKind> {
+pub struct SerializedDepGraph {
     /// The set of all DepNodes in the graph
-    nodes: IndexVec<SerializedDepNodeIndex, DepNode<K>>,
+    nodes: IndexVec<SerializedDepNodeIndex, DepNode>,
     /// The set of all Fingerprints in the graph. Each Fingerprint corresponds to
     /// the DepNode at the same index in the nodes vector.
     fingerprints: IndexVec<SerializedDepNodeIndex, Fingerprint>,
     /// For each DepNode, stores the list of edges originating from that
     /// DepNode. Encoded as a [start, end) pair indexing into edge_list_data,
     /// which holds the actual DepNodeIndices of the target nodes.
-    edge_list_indices: IndexVec<SerializedDepNodeIndex, (u32, u32)>,
-    /// A flattened list of all edge targets in the graph. Edge sources are
-    /// implicit in edge_list_indices.
-    edge_list_data: Vec<SerializedDepNodeIndex>,
-    /// Reciprocal map to `nodes`.
-    index: FxHashMap<DepNode<K>, SerializedDepNodeIndex>,
+    edge_list_indices: IndexVec<SerializedDepNodeIndex, EdgeHeader>,
+    /// A flattened list of all edge targets in the graph, stored in the same
+    /// varint encoding that we use on disk. Edge sources are implicit in edge_list_indices.
+    edge_list_data: Vec<u8>,
+    /// Stores a map from fingerprints to nodes per dep node kind.
+    /// This is the reciprocal of `nodes`.
+    index: Vec<UnhashMap<PackedFingerprint, SerializedDepNodeIndex>>,
 }
 
-impl<K: DepKind> Default for SerializedDepGraph<K> {
+impl Default for SerializedDepGraph {
     fn default() -> Self {
         SerializedDepGraph {
             nodes: Default::default(),
@@ -62,21 +100,47 @@ impl<K: DepKind> Default for SerializedDepGraph<K> {
     }
 }
 
-impl<K: DepKind> SerializedDepGraph<K> {
+impl SerializedDepGraph {
     #[inline]
-    pub fn edge_targets_from(&self, source: SerializedDepNodeIndex) -> &[SerializedDepNodeIndex] {
-        let targets = self.edge_list_indices[source];
-        &self.edge_list_data[targets.0 as usize..targets.1 as usize]
+    pub fn edge_targets_from(
+        &self,
+        source: SerializedDepNodeIndex,
+    ) -> impl Iterator<Item = SerializedDepNodeIndex> + '_ {
+        let header = self.edge_list_indices[source];
+        let mut raw = &self.edge_list_data[header.start()..];
+        // Figure out where the edge list for `source` ends by getting the start index of the next
+        // edge list, or the end of the array if this is the last edge.
+        let end = self
+            .edge_list_indices
+            .get(source + 1)
+            .map(|h| h.start())
+            .unwrap_or_else(|| self.edge_list_data.len() - DEP_NODE_PAD);
+
+        // The number of edges for this node is implicitly stored in the combination of the byte
+        // width and the length.
+        let bytes_per_index = header.bytes_per_index();
+        let len = (end - header.start()) / bytes_per_index;
+
+        // LLVM doesn't hoist EdgeHeader::mask so we do it ourselves.
+        let mask = header.mask();
+        (0..len).map(move |_| {
+            // Doing this slicing in this order ensures that the first bounds check suffices for
+            // all the others.
+            let index = &raw[..DEP_NODE_SIZE];
+            raw = &raw[bytes_per_index..];
+            let index = u32::from_le_bytes(index.try_into().unwrap()) & mask;
+            SerializedDepNodeIndex::from_u32(index)
+        })
     }
 
     #[inline]
-    pub fn index_to_node(&self, dep_node_index: SerializedDepNodeIndex) -> DepNode<K> {
+    pub fn index_to_node(&self, dep_node_index: SerializedDepNodeIndex) -> DepNode {
         self.nodes[dep_node_index]
     }
 
     #[inline]
-    pub fn node_to_index_opt(&self, dep_node: &DepNode<K>) -> Option<SerializedDepNodeIndex> {
-        self.index.get(dep_node).cloned()
+    pub fn node_to_index_opt(&self, dep_node: &DepNode) -> Option<SerializedDepNodeIndex> {
+        self.index.get(dep_node.kind.as_usize())?.get(&dep_node.hash).cloned()
     }
 
     #[inline]
@@ -84,16 +148,45 @@ impl<K: DepKind> SerializedDepGraph<K> {
         self.fingerprints[dep_node_index]
     }
 
+    #[inline]
     pub fn node_count(&self) -> usize {
-        self.index.len()
+        self.nodes.len()
+    }
+}
+
+/// A packed representation of an edge's start index and byte width.
+///
+/// This is packed by stealing 2 bits from the start index, which means we only accomodate edge
+/// data arrays up to a quarter of our address space. Which seems fine.
+#[derive(Debug, Clone, Copy)]
+struct EdgeHeader {
+    repr: usize,
+}
+
+impl EdgeHeader {
+    #[inline]
+    fn start(self) -> usize {
+        self.repr >> DEP_NODE_WIDTH_BITS
+    }
+
+    #[inline]
+    fn bytes_per_index(self) -> usize {
+        (self.repr & mask(DEP_NODE_WIDTH_BITS)) + 1
     }
+
+    #[inline]
+    fn mask(self) -> u32 {
+        mask(self.bytes_per_index() * 8) as u32
+    }
+}
+
+fn mask(bits: usize) -> usize {
+    usize::MAX >> ((std::mem::size_of::<usize>() * 8) - bits)
 }
 
-impl<'a, K: DepKind + Decodable<MemDecoder<'a>>> Decodable<MemDecoder<'a>>
-    for SerializedDepGraph<K>
-{
+impl SerializedDepGraph {
     #[instrument(level = "debug", skip(d))]
-    fn decode(d: &mut MemDecoder<'a>) -> SerializedDepGraph<K> {
+    pub fn decode<D: Deps>(d: &mut MemDecoder<'_>) -> SerializedDepGraph {
         // The last 16 bytes are the node count and edge count.
         debug!("position: {:?}", d.position());
         let (node_count, edge_count) =
@@ -107,76 +200,261 @@ impl<'a, K: DepKind + Decodable<MemDecoder<'a>>> Decodable<MemDecoder<'a>>
 
         debug!(?node_count, ?edge_count);
 
+        let graph_bytes = d.len() - (2 * IntEncodedWithFixedSize::ENCODED_SIZE) - d.position();
+
         let mut nodes = IndexVec::with_capacity(node_count);
         let mut fingerprints = IndexVec::with_capacity(node_count);
         let mut edge_list_indices = IndexVec::with_capacity(node_count);
-        let mut edge_list_data = Vec::with_capacity(edge_count);
+        // This estimation assumes that all of the encoded bytes are for the edge lists or for the
+        // fixed-size node headers. But that's not necessarily true; if any edge list has a length
+        // that spills out of the size we can bit-pack into SerializedNodeHeader then some of the
+        // total serialized size is also used by leb128-encoded edge list lengths. Neglecting that
+        // contribution to graph_bytes means our estimation of the bytes needed for edge_list_data
+        // slightly overshoots. But it cannot overshoot by much; consider that the worse case is
+        // for a node with length 64, which means the spilled 1-byte leb128 length is 1 byte of at
+        // least (34 byte header + 1 byte len + 64 bytes edge data), which is ~1%. A 2-byte leb128
+        // length is about the same fractional overhead and it amortizes for yet greater lengths.
+        let mut edge_list_data = Vec::with_capacity(
+            graph_bytes - node_count * std::mem::size_of::<SerializedNodeHeader<D>>(),
+        );
 
         for _index in 0..node_count {
-            let dep_node: DepNode<K> = Decodable::decode(d);
-            let _i: SerializedDepNodeIndex = nodes.push(dep_node);
+            // Decode the header for this edge; the header packs together as many of the fixed-size
+            // fields as possible to limit the number of times we update decoder state.
+            let node_header =
+                SerializedNodeHeader::<D> { bytes: d.read_array(), _marker: PhantomData };
+
+            let _i: SerializedDepNodeIndex = nodes.push(node_header.node());
             debug_assert_eq!(_i.index(), _index);
 
-            let fingerprint: Fingerprint = Decodable::decode(d);
-            let _i: SerializedDepNodeIndex = fingerprints.push(fingerprint);
+            let _i: SerializedDepNodeIndex = fingerprints.push(node_header.fingerprint());
             debug_assert_eq!(_i.index(), _index);
 
-            // Deserialize edges -- sequence of DepNodeIndex
-            let len = d.read_usize();
-            let start = edge_list_data.len().try_into().unwrap();
-            for _ in 0..len {
-                let edge = Decodable::decode(d);
-                edge_list_data.push(edge);
-            }
-            let end = edge_list_data.len().try_into().unwrap();
-            let _i: SerializedDepNodeIndex = edge_list_indices.push((start, end));
+            // If the length of this node's edge list is small, the length is stored in the header.
+            // If it is not, we fall back to another decoder call.
+            let num_edges = node_header.len().unwrap_or_else(|| d.read_usize());
+
+            // The edges index list uses the same varint strategy as rmeta tables; we select the
+            // number of byte elements per-array not per-element. This lets us read the whole edge
+            // list for a node with one decoder call and also use the on-disk format in memory.
+            let edges_len_bytes = node_header.bytes_per_index() * num_edges;
+            // The in-memory structure for the edges list stores the byte width of the edges on
+            // this node with the offset into the global edge data array.
+            let edges_header = node_header.edges_header(&edge_list_data);
+
+            edge_list_data.extend(d.read_raw_bytes(edges_len_bytes));
+
+            let _i: SerializedDepNodeIndex = edge_list_indices.push(edges_header);
             debug_assert_eq!(_i.index(), _index);
         }
 
-        let index: FxHashMap<_, _> =
-            nodes.iter_enumerated().map(|(idx, &dep_node)| (dep_node, idx)).collect();
+        // When we access the edge list data, we do a fixed-size read from the edge list data then
+        // mask off the bytes that aren't for that edge index, so the last read may dangle off the
+        // end of the array. This padding ensure it doesn't.
+        edge_list_data.extend(&[0u8; DEP_NODE_PAD]);
+
+        // Read the number of each dep kind and use it to create an hash map with a suitable size.
+        let mut index: Vec<_> = (0..(D::DEP_KIND_MAX + 1))
+            .map(|_| UnhashMap::with_capacity_and_hasher(d.read_u32() as usize, Default::default()))
+            .collect();
+
+        for (idx, node) in nodes.iter_enumerated() {
+            index[node.kind.as_usize()].insert(node.hash, idx);
+        }
 
         SerializedDepGraph { nodes, fingerprints, edge_list_indices, edge_list_data, index }
     }
 }
 
-#[derive(Debug, Encodable, Decodable)]
-pub struct NodeInfo<K: DepKind> {
-    node: DepNode<K>,
+/// A packed representation of all the fixed-size fields in a `NodeInfo`.
+///
+/// This stores in one byte array:
+/// * The `Fingerprint` in the `NodeInfo`
+/// * The `Fingerprint` in `DepNode` that is in this `NodeInfo`
+/// * The `DepKind`'s discriminant (a u16, but not all bits are used...)
+/// * The byte width of the encoded edges for this node
+/// * In whatever bits remain, the length of the edge list for this node, if it fits
+struct SerializedNodeHeader<D> {
+    // 2 bytes for the DepNode
+    // 16 for Fingerprint in DepNode
+    // 16 for Fingerprint in NodeInfo
+    bytes: [u8; 34],
+    _marker: PhantomData<D>,
+}
+
+// The fields of a `SerializedNodeHeader`, this struct is an implementation detail and exists only
+// to make the implementation of `SerializedNodeHeader` simpler.
+struct Unpacked {
+    len: Option<usize>,
+    bytes_per_index: usize,
+    kind: DepKind,
+    hash: PackedFingerprint,
     fingerprint: Fingerprint,
-    edges: SmallVec<[DepNodeIndex; 8]>,
 }
 
-struct Stat<K: DepKind> {
-    kind: K,
+// Bit fields, where
+// M: bits used to store the length of a node's edge list
+// N: bits used to store the byte width of elements of the edge list
+// are
+// 0..M    length of the edge
+// M..M+N  bytes per index
+// M+N..16 kind
+impl<D: Deps> SerializedNodeHeader<D> {
+    const TOTAL_BITS: usize = std::mem::size_of::<DepKind>() * 8;
+    const LEN_BITS: usize = Self::TOTAL_BITS - Self::KIND_BITS - Self::WIDTH_BITS;
+    const WIDTH_BITS: usize = DEP_NODE_WIDTH_BITS;
+    const KIND_BITS: usize = Self::TOTAL_BITS - D::DEP_KIND_MAX.leading_zeros() as usize;
+    const MAX_INLINE_LEN: usize = (u16::MAX as usize >> (Self::TOTAL_BITS - Self::LEN_BITS)) - 1;
+
+    #[inline]
+    fn new(node_info: &NodeInfo) -> Self {
+        debug_assert_eq!(Self::TOTAL_BITS, Self::LEN_BITS + Self::WIDTH_BITS + Self::KIND_BITS);
+
+        let NodeInfo { node, fingerprint, edges } = node_info;
+
+        let mut head = node.kind.as_inner();
+
+        let free_bytes = edges.max_index().leading_zeros() as usize / 8;
+        let bytes_per_index = (DEP_NODE_SIZE - free_bytes).saturating_sub(1);
+        head |= (bytes_per_index as u16) << Self::KIND_BITS;
+
+        // Encode number of edges + 1 so that we can reserve 0 to indicate that the len doesn't fit
+        // in this bitfield.
+        if edges.len() <= Self::MAX_INLINE_LEN {
+            head |= (edges.len() as u16 + 1) << (Self::KIND_BITS + Self::WIDTH_BITS);
+        }
+
+        let hash: Fingerprint = node.hash.into();
+
+        // Using half-open ranges ensures an unconditional panic if we get the magic numbers wrong.
+        let mut bytes = [0u8; 34];
+        bytes[..2].copy_from_slice(&head.to_le_bytes());
+        bytes[2..18].copy_from_slice(&hash.to_le_bytes());
+        bytes[18..].copy_from_slice(&fingerprint.to_le_bytes());
+
+        #[cfg(debug_assertions)]
+        {
+            let res = Self { bytes, _marker: PhantomData };
+            assert_eq!(node_info.fingerprint, res.fingerprint());
+            assert_eq!(node_info.node, res.node());
+            if let Some(len) = res.len() {
+                assert_eq!(node_info.edges.len(), len);
+            }
+        }
+        Self { bytes, _marker: PhantomData }
+    }
+
+    #[inline]
+    fn unpack(&self) -> Unpacked {
+        let head = u16::from_le_bytes(self.bytes[..2].try_into().unwrap());
+        let hash = self.bytes[2..18].try_into().unwrap();
+        let fingerprint = self.bytes[18..].try_into().unwrap();
+
+        let kind = head & mask(Self::KIND_BITS) as u16;
+        let bytes_per_index = (head >> Self::KIND_BITS) & mask(Self::WIDTH_BITS) as u16;
+        let len = (head as usize) >> (Self::WIDTH_BITS + Self::KIND_BITS);
+
+        Unpacked {
+            len: len.checked_sub(1),
+            bytes_per_index: bytes_per_index as usize + 1,
+            kind: DepKind::new(kind),
+            hash: Fingerprint::from_le_bytes(hash).into(),
+            fingerprint: Fingerprint::from_le_bytes(fingerprint),
+        }
+    }
+
+    #[inline]
+    fn len(&self) -> Option<usize> {
+        self.unpack().len
+    }
+
+    #[inline]
+    fn bytes_per_index(&self) -> usize {
+        self.unpack().bytes_per_index
+    }
+
+    #[inline]
+    fn fingerprint(&self) -> Fingerprint {
+        self.unpack().fingerprint
+    }
+
+    #[inline]
+    fn node(&self) -> DepNode {
+        let Unpacked { kind, hash, .. } = self.unpack();
+        DepNode { kind, hash }
+    }
+
+    #[inline]
+    fn edges_header(&self, edge_list_data: &[u8]) -> EdgeHeader {
+        EdgeHeader {
+            repr: (edge_list_data.len() << DEP_NODE_WIDTH_BITS) | (self.bytes_per_index() - 1),
+        }
+    }
+}
+
+#[derive(Debug)]
+struct NodeInfo {
+    node: DepNode,
+    fingerprint: Fingerprint,
+    edges: EdgesVec,
+}
+
+impl NodeInfo {
+    fn encode<D: Deps>(&self, e: &mut FileEncoder) {
+        let header = SerializedNodeHeader::<D>::new(self);
+        e.write_array(header.bytes);
+
+        if header.len().is_none() {
+            e.emit_usize(self.edges.len());
+        }
+
+        let bytes_per_index = header.bytes_per_index();
+        for node_index in self.edges.iter() {
+            e.write_with(|dest| {
+                *dest = node_index.as_u32().to_le_bytes();
+                bytes_per_index
+            });
+        }
+    }
+}
+
+struct Stat {
+    kind: DepKind,
     node_counter: u64,
     edge_counter: u64,
 }
 
-struct EncoderState<K: DepKind> {
+struct EncoderState<D: Deps> {
     encoder: FileEncoder,
     total_node_count: usize,
     total_edge_count: usize,
-    stats: Option<FxHashMap<K, Stat<K>>>,
+    stats: Option<FxHashMap<DepKind, Stat>>,
+
+    /// Stores the number of times we've encoded each dep kind.
+    kind_stats: Vec<u32>,
+    marker: PhantomData<D>,
 }
 
-impl<K: DepKind> EncoderState<K> {
+impl<D: Deps> EncoderState<D> {
     fn new(encoder: FileEncoder, record_stats: bool) -> Self {
         Self {
             encoder,
             total_edge_count: 0,
             total_node_count: 0,
             stats: record_stats.then(FxHashMap::default),
+            kind_stats: iter::repeat(0).take(D::DEP_KIND_MAX as usize + 1).collect(),
+            marker: PhantomData,
         }
     }
 
     fn encode_node(
         &mut self,
-        node: &NodeInfo<K>,
-        record_graph: &Option<Lock<DepGraphQuery<K>>>,
+        node: &NodeInfo,
+        record_graph: &Option<Lock<DepGraphQuery>>,
     ) -> DepNodeIndex {
         let index = DepNodeIndex::new(self.total_node_count);
         self.total_node_count += 1;
+        self.kind_stats[node.node.kind.as_usize()] += 1;
 
         let edge_count = node.edges.len();
         self.total_edge_count += edge_count;
@@ -197,16 +475,28 @@ impl<K: DepKind> EncoderState<K> {
         }
 
         let encoder = &mut self.encoder;
-        node.encode(encoder);
+        node.encode::<D>(encoder);
         index
     }
 
     fn finish(self, profiler: &SelfProfilerRef) -> FileEncodeResult {
-        let Self { mut encoder, total_node_count, total_edge_count, stats: _ } = self;
+        let Self {
+            mut encoder,
+            total_node_count,
+            total_edge_count,
+            stats: _,
+            kind_stats,
+            marker: _,
+        } = self;
 
         let node_count = total_node_count.try_into().unwrap();
         let edge_count = total_edge_count.try_into().unwrap();
 
+        // Encode the number of each dep kind encountered
+        for count in kind_stats.iter() {
+            count.encode(&mut encoder);
+        }
+
         debug!(?node_count, ?edge_count);
         debug!("position: {:?}", encoder.position());
         IntEncodedWithFixedSize(node_count).encode(&mut encoder);
@@ -223,12 +513,12 @@ impl<K: DepKind> EncoderState<K> {
     }
 }
 
-pub struct GraphEncoder<K: DepKind> {
-    status: Lock<EncoderState<K>>,
-    record_graph: Option<Lock<DepGraphQuery<K>>>,
+pub struct GraphEncoder<D: Deps> {
+    status: Lock<EncoderState<D>>,
+    record_graph: Option<Lock<DepGraphQuery>>,
 }
 
-impl<K: DepKind + Encodable<FileEncoder>> GraphEncoder<K> {
+impl<D: Deps> GraphEncoder<D> {
     pub fn new(
         encoder: FileEncoder,
         prev_node_count: usize,
@@ -240,7 +530,7 @@ impl<K: DepKind + Encodable<FileEncoder>> GraphEncoder<K> {
         GraphEncoder { status, record_graph }
     }
 
-    pub(crate) fn with_query(&self, f: impl Fn(&DepGraphQuery<K>)) {
+    pub(crate) fn with_query(&self, f: impl Fn(&DepGraphQuery)) {
         if let Some(record_graph) = &self.record_graph {
             f(&record_graph.lock())
         }
@@ -301,9 +591,9 @@ impl<K: DepKind + Encodable<FileEncoder>> GraphEncoder<K> {
     pub(crate) fn send(
         &self,
         profiler: &SelfProfilerRef,
-        node: DepNode<K>,
+        node: DepNode,
         fingerprint: Fingerprint,
-        edges: SmallVec<[DepNodeIndex; 8]>,
+        edges: EdgesVec,
     ) -> DepNodeIndex {
         let _prof_timer = profiler.generic_activity("incr_comp_encode_dep_graph");
         let node = NodeInfo { node, fingerprint, edges };
-- 
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