perf: remove useless iterator in new code splitting and some allocations (#9821)

perf: fix useless iterator in new code splitting

Author: JSerFeng

crates/rspack_core/src/build_chunk_graph/available_modules.rs

@@ -2,6 +2,7 @@ use std::borrow::Cow;
 
 use rspack_collections::IdentifierMap;
 use rustc_hash::FxHashSet as HashSet;
+use tracing::instrument;
 
 use super::new_code_splitter::{CacheableChunkItem, ChunkDesc, EntryChunkDesc};
 use crate::Compilation;
@@ -78,6 +79,7 @@ impl AvailableModules {
   }
 }
 
+#[instrument(skip_all)]
 #[allow(unused_variables)]
 pub fn remove_available_modules(
   compilation: &Compilation,
@@ -126,11 +128,13 @@ pub fn remove_available_modules(
           continue;
         }
         let res = res.into_owned();
-        *curr = res.clone();
-        res
+        *curr = res;
+        curr
       } else {
-        available_modules[chunk_index] = Some(parent_available_modules.clone());
-        parent_available_modules
+        available_modules[chunk_index] = Some(parent_available_modules);
+        available_modules[chunk_index]
+          .as_ref()
+          .expect("should have available modules")
       };
 
       // we have incomings that are not calculated, wait till we calculated
@@ -175,14 +179,18 @@ pub fn remove_available_modules(
   }
 
   let module_graph = compilation.get_module_graph();
+  let mut removed = HashSet::default();
+  let mut disconnect_children = HashSet::default();
+
   for (chunk_index, available) in available_modules.iter().enumerate() {
+    removed.clear();
+    disconnect_children.clear();
+
     let chunk = &mut chunks[chunk_index].1.chunk_desc;
     let Some(available) = available else {
       continue;
     };
 
-    let mut removed = HashSet::default();
-
     chunk.chunk_modules_mut().retain(|module_identifier| {
       let module = {
         #[cfg(debug_assertions)]
@@ -207,29 +215,30 @@ pub fn remove_available_modules(
       !in_parent
     });
 
+    if removed.is_empty() {
+      continue;
+    }
+
     let chunk = &chunks[chunk_index].1.chunk_desc;
     let outgoings = chunk.outgoings();
-    for removed_block_id in &removed {
-      let mut disconnect_children = HashSet::default();
-
-      chunk_children[chunk_index].iter().for_each(|child| {
-        let child_chunk = &chunks[*child].1.chunk_desc;
-
-        // if all incomings from current chunk are removed, we can remove this child
-        if child_chunk.incomings().iter().all(|incoming| {
-          // if all incomings are not from current chunk, we disconnect them
-          !removed.contains(incoming) && !outgoings.contains(incoming)
-        }) {
-          disconnect_children.insert(*child);
-        }
-      });
 
-      if !disconnect_children.is_empty() {
-        chunk_children[chunk_index].retain(|child| !disconnect_children.contains(child));
+    chunk_children[chunk_index].iter().for_each(|child| {
+      let child_chunk = &chunks[*child].1.chunk_desc;
 
-        for dead_child in disconnect_children {
-          chunk_parents[dead_child].retain(|parent| *parent != chunk_index);
-        }
+      // if all incomings from current chunk are removed, we can remove this child
+      if child_chunk.incomings().iter().all(|incoming| {
+        // if all incomings are not from current chunk, we disconnect them
+        !removed.contains(incoming) && !outgoings.contains(incoming)
+      }) {
+        disconnect_children.insert(*child);
+      }
+    });
+
+    if !disconnect_children.is_empty() {
+      chunk_children[chunk_index].retain(|child| !disconnect_children.contains(child));
+
+      for dead_child in &disconnect_children {
+        chunk_parents[*dead_child].retain(|parent| *parent != chunk_index);
       }
     }
   }

crates/rspack_core/src/build_chunk_graph/new_code_splitter.rs

@@ -14,6 +14,7 @@ use rspack_collections::{
 };
 use rspack_error::{error, Diagnostic, Result};
 use rustc_hash::{FxHashMap as HashMap, FxHashSet as HashSet};
+use tracing::instrument;
 
 use super::available_modules::{remove_available_modules, AvailableModules};
 use crate::{
@@ -389,6 +390,7 @@ impl CodeSplitter {
     }
   }
 
+  #[instrument(skip_all)]
   fn analyze_module_graph(
     &mut self,
     compilation: &mut Compilation,
@@ -1418,6 +1420,7 @@ Or do you want to use the entrypoints '{name}' and '{entry_runtime}' independent
 
   // 1. determine parent child relationship
   // 2. remove modules that exist in all parents
+  #[instrument(skip_all)]
   fn finalize_chunk_desc(
     &mut self,
     mut chunks: Vec<(bool, CacheableChunkItem)>,
@@ -1473,7 +1476,9 @@ Or do you want to use the entrypoints '{name}' and '{entry_runtime}' independent
     }
 
     // 2nd iter, analyze chunk relations
+    let mut parents = HashSet::default();
     for (idx, (_, cache)) in chunks.iter().enumerate() {
+      parents.clear();
       match &cache.chunk_desc {
         ChunkDesc::Entry(entry) => {
           if let Some(depend_on) = &entry.options.depend_on {
@@ -1493,7 +1498,6 @@ Or do you want to use the entrypoints '{name}' and '{entry_runtime}' independent
           }
         }
         ChunkDesc::Chunk(chunk) => {
-          let mut parents = HashSet::default();
           for block in &chunk.incoming_blocks {
             let Some(chunk_parents) = chunks_by_block.get(block) else {
               continue;
@@ -1503,8 +1507,9 @@ Or do you want to use the entrypoints '{name}' and '{entry_runtime}' independent
           }
           chunk_parents.push(
             parents
-              .into_iter()
-              .filter(|parent| *parent != idx)
+              .iter()
+              .filter(|parent| **parent != idx)
+              .copied()
               .collect::<Vec<_>>(),
           );
         }
@@ -1605,6 +1610,7 @@ Or do you want to use the entrypoints '{name}' and '{entry_runtime}' independent
   }
 
   // merge chunks that has the same name on them
+  #[instrument(skip_all)]
   fn merge_same_chunks(
     &mut self,
     chunks: Vec<(bool, CacheableChunkItem)>,