Remove Clone Staring Me In the Face

wgpu-core/src/track/buffer.rs

@@ -11,8 +11,8 @@ use crate::{
     resource::{Buffer, Trackable},
     snatch::SnatchGuard,
     track::{
-        invalid_resource_state, skip_barrier, ResourceMetadata, ResourceMetadataProvider,
-        ResourceUsageCompatibilityError, ResourceUses,
+        invalid_resource_state, metadata::ArcEq, skip_barrier, ResourceMetadata,
+        ResourceMetadataProvider, ResourceUsageCompatibilityError, ResourceUses,
     },
 };
 use hal::{BufferBarrier, BufferUses};
@@ -681,7 +681,7 @@ impl BufferStateProvider<'_> {
 }
 
 #[inline(always)]
-unsafe fn insert<T: Clone>(
+unsafe fn insert<T: Clone + ArcEq>(
     start_states: Option<&mut [BufferUses]>,
     current_states: &mut [BufferUses],
     resource_metadata: &mut ResourceMetadata<T>,
@@ -706,7 +706,7 @@ unsafe fn insert<T: Clone>(
         *current_states.get_unchecked_mut(index) = new_end_state;
 
         let resource = metadata_provider.get(index);
-        resource_metadata.insert(index, resource.clone());
+        resource_metadata.insert(index, resource);
     }
 }
 

wgpu-core/src/track/metadata.rs

@@ -1,8 +1,26 @@
 //! The `ResourceMetadata` type.
 
+use std::sync::{Arc, Weak};
+
 use bit_vec::BitVec;
 use wgt::strict_assert;
 
+pub(super) trait ArcEq {
+    fn arc_eq(&self, other: &Self) -> bool;
+}
+
+impl<T> ArcEq for Arc<T> {
+    fn arc_eq(&self, other: &Self) -> bool {
+        Arc::ptr_eq(self, other)
+    }
+}
+
+impl<T> ArcEq for Weak<T> {
+    fn arc_eq(&self, _other: &Self) -> bool {
+        true
+    }
+}
+
 /// A set of resources, holding a `Arc<T>` and epoch for each member.
 ///
 /// Testing for membership is fast, and iterating over members is
@@ -11,15 +29,15 @@ use wgt::strict_assert;
 /// members, but a bit vector tracks occupancy, so iteration touches
 /// only occupied elements.
 #[derive(Debug)]
-pub(super) struct ResourceMetadata<T: Clone> {
+pub(super) struct ResourceMetadata<T: Clone + ArcEq> {
     /// If the resource with index `i` is a member, `owned[i]` is `true`.
     owned: BitVec<usize>,
 
     /// A vector holding clones of members' `T`s.
     resources: Vec<Option<T>>,
 }
 
-impl<T: Clone> ResourceMetadata<T> {
+impl<T: Clone + ArcEq> ResourceMetadata<T> {
     pub(super) fn new() -> Self {
         Self {
             owned: BitVec::default(),
@@ -88,10 +106,15 @@ impl<T: Clone> ResourceMetadata<T> {
     /// The given `index` must be in bounds for this `ResourceMetadata`'s
     /// existing tables. See `tracker_assert_in_bounds`.
     #[inline(always)]
-    pub(super) unsafe fn insert(&mut self, index: usize, resource: T) -> &T {
+    pub(super) unsafe fn insert(&mut self, index: usize, new_resource: &T) {
         self.owned.set(index, true);
         let resource_dst = unsafe { self.resources.get_unchecked_mut(index) };
-        resource_dst.insert(resource)
+        match resource_dst {
+            Some(old_resource) => debug_assert!(old_resource.arc_eq(new_resource)),
+            None => {
+                *resource_dst = Some(new_resource.clone());
+            }
+        }
     }
 
     /// Get the resource with the given index.
@@ -142,13 +165,13 @@ impl<T: Clone> ResourceMetadata<T> {
 ///
 /// This is used to abstract over the various places
 /// trackers can get new resource metadata from.
-pub(super) enum ResourceMetadataProvider<'a, T: Clone> {
+pub(super) enum ResourceMetadataProvider<'a, T: Clone + ArcEq> {
     /// Comes directly from explicit values.
     Direct { resource: &'a T },
     /// Comes from another metadata tracker.
     Indirect { metadata: &'a ResourceMetadata<T> },
 }
-impl<T: Clone> ResourceMetadataProvider<'_, T> {
+impl<T: Clone + ArcEq> ResourceMetadataProvider<'_, T> {
     /// Get a reference to the resource from this.
     ///
     /// # Safety

wgpu-core/src/track/texture.rs

@@ -23,8 +23,7 @@ use crate::{
     resource::{Texture, TextureInner, TextureView, Trackable},
     snatch::SnatchGuard,
     track::{
-        invalid_resource_state, skip_barrier, ResourceMetadata, ResourceMetadataProvider,
-        ResourceUsageCompatibilityError, ResourceUses,
+        invalid_resource_state, metadata::ArcEq, skip_barrier, ResourceMetadata, ResourceMetadataProvider, ResourceUsageCompatibilityError, ResourceUses
     },
 };
 use hal::{TextureBarrier, TextureUses};
@@ -1082,7 +1081,7 @@ unsafe fn insert_or_barrier_update(
 }
 
 #[inline(always)]
-unsafe fn insert<T: Clone>(
+unsafe fn insert<T: Clone + ArcEq>(
     texture_selector: Option<&TextureSelector>,
     start_state: Option<&mut TextureStateSet>,
     end_state: &mut TextureStateSet,
@@ -1152,7 +1151,7 @@ unsafe fn insert<T: Clone>(
 
     unsafe {
         let resource = metadata_provider.get(index);
-        resource_metadata.insert(index, resource.clone());
+        resource_metadata.insert(index, resource);
     }
 }