More changes to HashMap/HashSet to use fxhash (#39244)

Moved more functions to fxhash. And provide comments about the choices
when necessary.


Testing: Hash functions shouldn't change functionality.

Signed-off-by: Narfinger <Narfinger@users.noreply.github.com>

components/compositing/compositor.rs

@@ -3,7 +3,6 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 use std::cell::{Cell, Ref, RefCell};
-use std::collections::HashMap;
 use std::collections::hash_map::Entry;
 use std::env;
 use std::fs::create_dir_all;
@@ -1693,9 +1692,9 @@ struct FrameDelayer {
     /// The latest [`Epoch`] of canvas images that have been sent to WebRender. Note
     /// that this only records the `Epoch`s for canvases and only ones that are involved
     /// in "update the rendering".
-    image_epochs: HashMap<ImageKey, Epoch>,
+    image_epochs: FxHashMap<ImageKey, Epoch>,
     /// A map of all pending canvas images
-    pending_canvas_images: HashMap<ImageKey, Epoch>,
+    pending_canvas_images: FxHashMap<ImageKey, Epoch>,
     /// Whether or not we have a pending frame.
     pending_frame: bool,
     /// A list of pipelines that should be notified when we are no longer waiting for

components/net/protocols/mod.rs

@@ -2,7 +2,6 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
-use std::collections::HashMap;
 use std::collections::hash_map::Entry;
 use std::future::Future;
 use std::ops::Bound;
@@ -14,6 +13,7 @@ use log::error;
 use net_traits::filemanager_thread::RelativePos;
 use net_traits::request::Request;
 use net_traits::response::Response;
+use rustc_hash::FxHashMap;
 use servo_url::ServoUrl;
 
 use crate::fetch::methods::{DoneChannel, FetchContext, RangeRequestBounds};
@@ -68,7 +68,7 @@ pub trait ProtocolHandler: Send + Sync {
 
 #[derive(Default)]
 pub struct ProtocolRegistry {
-    pub(crate) handlers: HashMap<String, Box<dyn ProtocolHandler>>, // Maps scheme -> handler
+    pub(crate) handlers: FxHashMap<String, Box<dyn ProtocolHandler>>, // Maps scheme -> handler
 }
 
 #[derive(Clone, Copy, Debug)]
@@ -94,6 +94,7 @@ impl ProtocolRegistry {
         registry
     }
 
+    /// Do not allow users to enter an arbitrary protocol as this can lead to slowdowns.
     pub fn register(
         &mut self,
         scheme: &str,

components/script/dom/html/htmlimageelement.rs

@@ -3,7 +3,6 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 use std::cell::Cell;
-use std::collections::HashSet;
 use std::default::Default;
 use std::rc::Rc;
 use std::sync::{Arc, LazyLock};
@@ -32,6 +31,7 @@ use pixels::{
     CorsStatus, ImageMetadata, PixelFormat, Snapshot, SnapshotAlphaMode, SnapshotPixelFormat,
 };
 use regex::Regex;
+use rustc_hash::FxHashSet;
 use servo_url::ServoUrl;
 use servo_url::origin::MutableOrigin;
 use style::attr::{AttrValue, LengthOrPercentageOrAuto, parse_unsigned_integer};
@@ -840,7 +840,8 @@ impl HTMLImageElement {
         let source_set = self.source_set.borrow();
         let len = source_set.image_sources.len();
 
-        let mut repeat_indices = HashSet::new();
+        // Using FxHash is ok here as the indices are just 0..len
+        let mut repeat_indices = FxHashSet::default();
         for outer_index in 0..len {
             if repeat_indices.contains(&outer_index) {
                 continue;

components/shared/compositing/lib.rs

@@ -12,6 +12,7 @@ use crossbeam_channel::Sender;
 use embedder_traits::{AnimationState, EventLoopWaker, TouchEventResult};
 use log::warn;
 use malloc_size_of_derive::MallocSizeOf;
+use rustc_hash::FxHashMap;
 use smallvec::SmallVec;
 use strum_macros::IntoStaticStr;
 use webrender_api::{DocumentId, FontVariation};
@@ -20,7 +21,6 @@ pub mod display_list;
 pub mod rendering_context;
 pub mod viewport_description;
 
-use std::collections::HashMap;
 use std::sync::{Arc, Mutex};
 
 use base::generic_channel::{self, GenericCallback, GenericSender};
@@ -426,7 +426,7 @@ pub enum WebrenderImageHandlerType {
 #[derive(Default)]
 pub struct WebrenderExternalImageRegistry {
     /// Map of all generated external images.
-    external_images: HashMap<ExternalImageId, WebrenderImageHandlerType>,
+    external_images: FxHashMap<ExternalImageId, WebrenderImageHandlerType>,
     /// Id generator for the next external image identifier.
     next_image_id: u64,
 }

components/shared/net/pub_domains.rs

@@ -14,20 +14,22 @@
 //! we don't need to make the code more complex for it. The `mach` update command makes sure that
 //! those cases are not present.
 
-use std::collections::HashSet;
 use std::iter::FromIterator;
 use std::sync::LazyLock;
 
 use embedder_traits::resources::{self, Resource};
 use malloc_size_of::{MallocSizeOf, MallocSizeOfOps};
 use malloc_size_of_derive::MallocSizeOf;
+use rustc_hash::FxHashSet;
 use servo_url::{Host, ImmutableOrigin, ServoUrl};
 
+// We can use FxHash here.
+// The list is given by publicsuffix.org so an attack is highly unlikely
 #[derive(Clone, Debug, Default, MallocSizeOf)]
 pub struct PubDomainRules {
-    rules: HashSet<String>,
+    rules: FxHashSet<String>,
-    wildcards: HashSet<String>,
+    wildcards: FxHashSet<String>,
-    exceptions: HashSet<String>,
+    exceptions: FxHashSet<String>,
 }
 
 static PUB_DOMAINS: LazyLock<PubDomainRules> = LazyLock::new(load_pub_domains);

components/webgl/webxr.rs

@@ -2,7 +2,6 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
-use std::collections::HashMap;
 use std::num::NonZeroU32;
 
 use canvas_traits::webgl::{
@@ -25,7 +24,7 @@ use crate::webgl_thread::{GLContextData, WebGLThread};
 /// Bridge between WebGL and WebXR
 pub(crate) struct WebXRBridge {
     factory_receiver: crossbeam_channel::Receiver<WebXRLayerManagerFactory<WebXRSurfman>>,
-    managers: HashMap<WebXRLayerManagerId, Box<dyn WebXRLayerManagerAPI<WebXRSurfman>>>,
+    managers: FxHashMap<WebXRLayerManagerId, Box<dyn WebXRLayerManagerAPI<WebXRSurfman>>>,
     next_manager_id: NonZeroU32,
 }
 
@@ -34,7 +33,7 @@ impl WebXRBridge {
         let WebXRBridgeInit {
             factory_receiver, ..
         } = init;
-        let managers = HashMap::new();
+        let managers = FxHashMap::default();
         let next_manager_id = NonZeroU32::MIN;
         WebXRBridge {
             factory_receiver,