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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/244308">244308</a></dd>
<dt>Author</dt> <dd>drousso@apple.com</dd>
<dt>Date</dt> <dd>2019-04-15 16:48:57 -0700 (Mon, 15 Apr 2019)</dd>
</dl>

<h3>Log Message</h3>
<pre>Web Inspector: Heap: don't use recursion when calculating root paths
https://bugs.webkit.org/show_bug.cgi?id=196890
<rdar://problem/49870751>

Reviewed by Joseph Pecoraro.

* UserInterface/Workers/HeapSnapshot/HeapSnapshot.js:
(HeapSnapshot.prototype.shortestGCRootPath):
(HeapSnapshot.prototype._determineGCRootPaths):
(HeapSnapshot.prototype._gcRootPathes.visitNode): Deleted.
(HeapSnapshot.prototype._gcRootPathes): Deleted.</pre>

<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceWebInspectorUIChangeLog">trunk/Source/WebInspectorUI/ChangeLog</a></li>
<li><a href="#trunkSourceWebInspectorUIUserInterfaceWorkersHeapSnapshotHeapSnapshotjs">trunk/Source/WebInspectorUI/UserInterface/Workers/HeapSnapshot/HeapSnapshot.js</a></li>
</ul>

</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceWebInspectorUIChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebInspectorUI/ChangeLog (244307 => 244308)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebInspectorUI/ChangeLog    2019-04-15 23:48:55 UTC (rev 244307)
+++ trunk/Source/WebInspectorUI/ChangeLog       2019-04-15 23:48:57 UTC (rev 244308)
</span><span class="lines">@@ -1,3 +1,17 @@
</span><ins>+2019-04-15  Devin Rousso  <drousso@apple.com>
+
+        Web Inspector: Heap: don't use recursion when calculating root paths
+        https://bugs.webkit.org/show_bug.cgi?id=196890
+        <rdar://problem/49870751>
+
+        Reviewed by Joseph Pecoraro.
+
+        * UserInterface/Workers/HeapSnapshot/HeapSnapshot.js:
+        (HeapSnapshot.prototype.shortestGCRootPath):
+        (HeapSnapshot.prototype._determineGCRootPaths):
+        (HeapSnapshot.prototype._gcRootPathes.visitNode): Deleted.
+        (HeapSnapshot.prototype._gcRootPathes): Deleted.
+
</ins><span class="cx"> 2019-04-15  Joseph Pecoraro  <pecoraro@apple.com>
</span><span class="cx"> 
</span><span class="cx">         Web Inspector: SameSite parsing should be stricter
</span></span></pre></div>
<a id="trunkSourceWebInspectorUIUserInterfaceWorkersHeapSnapshotHeapSnapshotjs"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebInspectorUI/UserInterface/Workers/HeapSnapshot/HeapSnapshot.js (244307 => 244308)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebInspectorUI/UserInterface/Workers/HeapSnapshot/HeapSnapshot.js   2019-04-15 23:48:55 UTC (rev 244307)
+++ trunk/Source/WebInspectorUI/UserInterface/Workers/HeapSnapshot/HeapSnapshot.js      2019-04-15 23:48:57 UTC (rev 244308)
</span><span class="lines">@@ -278,7 +278,7 @@
</span><span class="cx">         // Internal nodes are avoided, so if the path is empty this
</span><span class="cx">         // node is either a gcRoot or only reachable via Internal nodes.
</span><span class="cx"> 
</span><del>-        let paths = this._gcRootPathes(nodeIdentifier);
</del><ins>+        let paths = this._determineGCRootPaths(nodeIdentifier);
</ins><span class="cx">         if (!paths.length)
</span><span class="cx">             return [];
</span><span class="cx"> 
</span><span class="lines">@@ -734,7 +734,7 @@
</span><span class="cx">             || className === "GlobalObject";
</span><span class="cx">     }
</span><span class="cx"> 
</span><del>-    _gcRootPathes(nodeIdentifier)
</del><ins>+    _determineGCRootPaths(nodeIdentifier)
</ins><span class="cx">     {
</span><span class="cx">         let targetNodeOrdinal = this._nodeIdentifierToOrdinal.get(nodeIdentifier);
</span><span class="cx"> 
</span><span class="lines">@@ -743,22 +743,34 @@
</span><span class="cx"> 
</span><span class="cx">         // FIXME: Array push/pop can affect performance here, but in practice it hasn't been an issue.
</span><span class="cx"> 
</span><del>-        let paths = [];
-        let currentPath = [];
</del><ins>+        let gcRootPaths = [];
</ins><span class="cx">         let visited = new Uint8Array(this._nodeCount);
</span><span class="cx"> 
</span><del>-        function visitNode(nodeOrdinal)
-        {
</del><ins>+        let pathsBeingProcessed = [
+            {
+                currentPath: [],
+                nodeOrdinal: targetNodeOrdinal,
+            },
+        ];
+        for (let i = 0; i < pathsBeingProcessed.length; ++i) {
+            let {currentPath, nodeOrdinal} = pathsBeingProcessed[i];
+
+            // Rather than use `Array.prototype.unshift`, which may be very expensive, keep track of
+            // the "current" position as `i` and "delete" the values already processed by clearing
+            // the value at that index.
+            pathsBeingProcessed[i] = undefined;
+
</ins><span class="cx">             if (this._nodeOrdinalIsGCRoot[nodeOrdinal]) {
</span><span class="cx">                 let fullPath = currentPath.slice();
</span><span class="cx">                 let nodeIndex = nodeOrdinal * this._nodeFieldCount;
</span><span class="cx">                 fullPath.push({node: nodeIndex});
</span><del>-                paths.push(fullPath);
-                return;
</del><ins>+                gcRootPaths.push(fullPath);
+                continue;
</ins><span class="cx">             }
</span><span class="cx"> 
</span><span class="cx">             if (visited[nodeOrdinal])
</span><del>-                return;
</del><ins>+                continue;
+
</ins><span class="cx">             visited[nodeOrdinal] = 1;
</span><span class="cx"> 
</span><span class="cx">             let nodeIndex = nodeOrdinal * this._nodeFieldCount;
</span><span class="lines">@@ -775,18 +787,13 @@
</span><span class="cx">                 if (fromNodeIsInternal)
</span><span class="cx">                     continue;
</span><span class="cx"> 
</span><del>-                let edgeIndex = this._incomingEdges[incomingEdgeIndex];
-                currentPath.push({edge: edgeIndex});
-                visitNode.call(this, fromNodeOrdinal);
-                currentPath.pop();
</del><ins>+                let newPath = currentPath.slice();
+                newPath.push({edge: this._incomingEdges[incomingEdgeIndex]});
+                pathsBeingProcessed.push({currentPath: newPath, nodeOrdinal: fromNodeOrdinal});
</ins><span class="cx">             }
</span><del>-
-            currentPath.pop();
</del><span class="cx">         }
</span><span class="cx"> 
</span><del>-        visitNode.call(this, targetNodeOrdinal);
-
-        return paths;
</del><ins>+        return gcRootPaths;
</ins><span class="cx">     }
</span><span class="cx"> };
</span><span class="cx"> 
</span></span></pre>
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