Remove PackedFingerprint

Author: tgnottingham

compiler/rustc_data_structures/src/fingerprint.rs

@@ -159,61 +159,3 @@ impl FingerprintDecoder for opaque::Decoder<'_> {
         Fingerprint::decode_opaque(self)
     }
 }
-
-// `PackedFingerprint` wraps a `Fingerprint`. Its purpose is to, on certain
-// architectures, behave like a `Fingerprint` without alignment requirements.
-// This behavior is only enabled on x86 and x86_64, where the impact of
-// unaligned accesses is tolerable in small doses.
-//
-// This may be preferable to use in large collections of structs containing
-// fingerprints, as it can reduce memory consumption by preventing the padding
-// that the more strictly-aligned `Fingerprint` can introduce. An application of
-// this is in the query dependency graph, which contains a large collection of
-// `DepNode`s. As of this writing, the size of a `DepNode` decreases by ~30%
-// (from 24 bytes to 17) by using the packed representation here, which
-// noticeably decreases total memory usage when compiling large crates.
-//
-// The wrapped `Fingerprint` is private to reduce the chance of a client
-// invoking undefined behavior by taking a reference to the packed field.
-#[cfg_attr(any(target_arch = "x86", target_arch = "x86_64"), repr(packed))]
-#[derive(Eq, PartialEq, Ord, PartialOrd, Debug, Clone, Copy, Hash)]
-pub struct PackedFingerprint(Fingerprint);
-
-impl std::fmt::Display for PackedFingerprint {
-    #[inline]
-    fn fmt(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        // Copy to avoid taking reference to packed field.
-        let copy = self.0;
-        copy.fmt(formatter)
-    }
-}
-
-impl<E: rustc_serialize::Encoder> Encodable<E> for PackedFingerprint {
-    #[inline]
-    fn encode(&self, s: &mut E) -> Result<(), E::Error> {
-        // Copy to avoid taking reference to packed field.
-        let copy = self.0;
-        copy.encode(s)
-    }
-}
-
-impl<D: rustc_serialize::Decoder> Decodable<D> for PackedFingerprint {
-    #[inline]
-    fn decode(d: &mut D) -> Result<Self, D::Error> {
-        Fingerprint::decode(d).map(PackedFingerprint)
-    }
-}
-
-impl From<Fingerprint> for PackedFingerprint {
-    #[inline]
-    fn from(f: Fingerprint) -> PackedFingerprint {
-        PackedFingerprint(f)
-    }
-}
-
-impl From<PackedFingerprint> for Fingerprint {
-    #[inline]
-    fn from(f: PackedFingerprint) -> Fingerprint {
-        f.0
-    }
-}

compiler/rustc_data_structures/src/lib.rs

@@ -31,7 +31,6 @@
 #![feature(once_cell)]
 #![feature(maybe_uninit_uninit_array)]
 #![allow(rustc::default_hash_types)]
-#![deny(unaligned_references)]
 
 #[macro_use]
 extern crate tracing;

compiler/rustc_middle/src/dep_graph/dep_node.rs

@@ -359,10 +359,6 @@ pub type DepNode = rustc_query_system::dep_graph::DepNode<DepKind>;
 // 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, 17);
-
-#[cfg(not(any(target_arch = "x86", target_arch = "x86_64")))]
 static_assert_size!(DepNode, 24);
 
 pub trait DepNodeExt: Sized {
@@ -396,7 +392,7 @@ impl DepNodeExt for DepNode {
     /// single DefId/DefPathHash parameter.
     fn from_def_path_hash(def_path_hash: DefPathHash, kind: DepKind) -> DepNode {
         debug_assert!(kind.can_reconstruct_query_key() && kind.has_params);
-        DepNode { kind, hash: def_path_hash.0.into() }
+        DepNode { kind, hash: def_path_hash.0 }
     }
 
     /// Extracts the DefId corresponding to this DepNode. This will work
@@ -411,10 +407,7 @@ impl DepNodeExt for DepNode {
     /// has been removed.
     fn extract_def_id(&self, tcx: TyCtxt<'tcx>) -> Option<DefId> {
         if self.kind.can_reconstruct_query_key() {
-            tcx.queries
-                .on_disk_cache
-                .as_ref()?
-                .def_path_hash_to_def_id(tcx, DefPathHash(self.hash.into()))
+            tcx.queries.on_disk_cache.as_ref()?.def_path_hash_to_def_id(tcx, DefPathHash(self.hash))
         } else {
             None
         }

compiler/rustc_query_system/src/dep_graph/dep_node.rs

@@ -44,7 +44,7 @@
 
 use super::{DepContext, DepKind};
 
-use rustc_data_structures::fingerprint::{Fingerprint, PackedFingerprint};
+use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 
 use std::fmt;
@@ -65,7 +65,7 @@ pub struct DepNode<K> {
     //
     // FIXME: Enforce this by preventing manual construction of `DefNode`
     // (e.g. add a `_priv: ()` field)
-    pub hash: PackedFingerprint,
+    pub hash: Fingerprint,
 }
 
 impl<K: DepKind> DepNode<K> {
@@ -74,7 +74,7 @@ impl<K: DepKind> DepNode<K> {
     /// does not require any parameters.
     pub fn new_no_params(kind: K) -> DepNode<K> {
         debug_assert!(!kind.has_params());
-        DepNode { kind, hash: Fingerprint::ZERO.into() }
+        DepNode { kind, hash: Fingerprint::ZERO }
     }
 
     pub fn construct<Ctxt, Key>(tcx: Ctxt, kind: K, arg: &Key) -> DepNode<K>
@@ -83,7 +83,7 @@ impl<K: DepKind> DepNode<K> {
         Key: DepNodeParams<Ctxt>,
     {
         let hash = arg.to_fingerprint(tcx);
-        let dep_node = DepNode { kind, hash: hash.into() };
+        let dep_node = DepNode { kind, hash: hash };
 
         #[cfg(debug_assertions)]
         {

compiler/rustc_query_system/src/dep_graph/graph.rs

@@ -390,7 +390,7 @@ impl<K: DepKind> DepGraph<K> {
                 // Fingerprint::combine() is faster than sending Fingerprint
                 // through the StableHasher (at least as long as StableHasher
                 // is so slow).
-                hash: data.current.anon_id_seed.combine(hasher.finish()).into(),
+                hash: data.current.anon_id_seed.combine(hasher.finish()),
             };
 
             let dep_node_index = data.current.intern_new_node(