Optimize Symbol Propagation (propagateSymbolsUp) (#9337)

Co-authored-by: Niklas Mischkulnig <[email protected]> Co-authored-by: Celina Peralta <[email protected]>
parcel-bundler · Nov 27, 2023 · dc3d92b · dc3d92b
1 parent 65f8e21
commit dc3d92b
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Showing 2 changed files with 71 additions and 13 deletions.
diff --git a/packages/core/core/src/SymbolPropagation.js b/packages/core/core/src/SymbolPropagation.js
@@ -639,21 +639,18 @@ function propagateSymbolsUp(
       assetGraph.rootNodeId,
       'A root node is required to traverse',
     );
-    let visited = new Set([rootNodeId]);
-    const walk = (nodeId: NodeId) => {
+
+    const nodeVisitor = nodeId => {
       let node = nullthrows(assetGraph.getNode(nodeId));
       let outgoing = assetGraph.getNodeIdsConnectedFrom(nodeId);
+
       for (let childId of outgoing) {
-        if (!visited.has(childId)) {
-          visited.add(childId);
-          walk(childId);
-          let child = nullthrows(assetGraph.getNode(childId));
-          if (node.type === 'asset') {
-            invariant(child.type === 'dependency');
-            if (child.usedSymbolsUpDirtyUp) {
-              node.usedSymbolsUpDirty = true;
-              child.usedSymbolsUpDirtyUp = false;
-            }
+        let child = nullthrows(assetGraph.getNode(childId));
+        if (node.type === 'asset') {
+          invariant(child.type === 'dependency');
+          if (child.usedSymbolsUpDirtyUp) {
+            node.usedSymbolsUpDirty = true;
+            child.usedSymbolsUpDirtyUp = false;
           }
         }
       }
@@ -698,7 +695,7 @@ function propagateSymbolsUp(
         }
       }
     };
-    walk(rootNodeId);
+    assetGraph.postOrderDfsFast(nodeVisitor, rootNodeId);
   }
 
   let queue = dirtyDeps ?? changedDepsUsedSymbolsUpDirtyDownAssets;

diff --git a/packages/core/graph/src/Graph.js b/packages/core/graph/src/Graph.js
@@ -388,6 +388,67 @@ export default class Graph<TNode, TEdgeType: number = 1> {
     return null;
   }
 
+  // A post-order implementation of dfsFast
+  postOrderDfsFast(
+    visit: GraphTraversalCallback<NodeId, TraversalActions>,
+    startNodeId: ?NodeId,
+  ): void {
+    let traversalStartNode = nullthrows(
+      startNodeId ?? this.rootNodeId,
+      'A start node is required to traverse',
+    );
+    this._assertHasNodeId(traversalStartNode);
+
+    let visited;
+    if (!this._visited || this._visited.capacity < this.nodes.length) {
+      this._visited = new BitSet(this.nodes.length);
+      visited = this._visited;
+    } else {
+      visited = this._visited;
+      visited.clear();
+    }
+    this._visited = null;
+
+    let stopped = false;
+    let actions: TraversalActions = {
+      stop() {
+        stopped = true;
+      },
+      skipChildren() {
+        throw new Error(
+          'Calling skipChildren inside a post-order traversal is not allowed',
+        );
+      },
+    };
+
+    let queue = [traversalStartNode];
+    while (queue.length !== 0) {
+      let nodeId = queue[queue.length - 1];
+
+      if (!visited.has(nodeId)) {
+        visited.add(nodeId);
+
+        this.adjacencyList.forEachNodeIdConnectedFromReverse(nodeId, child => {
+          if (!visited.has(child)) {
+            queue.push(child);
+          }
+          return false;
+        });
+      } else {
+        queue.pop();
+        visit(nodeId, null, actions);
+
+        if (stopped) {
+          this._visited = visited;
+          return;
+        }
+      }
+    }
+
+    this._visited = visited;
+    return;
+  }
+
   dfs<TContext>({
     visit,
     startNodeId,