[llvm] [SandboxVec][Scheduler][NFC] ReadyListContainer::contains() is now constant time (PR #215418)

[via llvm-commits]

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@@ -69,40 +71,51 @@ class ReadyListContainer {
     assert(!contains(N) && "Node already exists in ready list!");
 #endif
     List.push(N);
+    Set.insert(N);
+    assert(List.size() == Set.size() && "List and Set out-of-sync!");
   }
   DGNode *pop() {
     auto *Back = List.top();
     List.pop();
+    Set.erase(Back);
+    assert(List.size() == Set.size() && "List and Set out-of-sync!");
     return Back;
   }
-  bool empty() const { return List.empty(); }
-  void clear() { List = {}; }
+  bool empty() const {
+    assert(List.empty() == Set.empty() && "List and Set out-of-sync!");
+    return List.empty();
+  }
+  void clear() {
+    List.clear();
+    Set.clear();
+  }
   bool contains(DGNode *N) const {
-    // TODO: We should update the data structure to make this O(1).
-    auto ListCopy = List;
-    while (!ListCopy.empty()) {
-      DGNode *Top = ListCopy.top();
-      if (Top == N)
-        return true;
-      ListCopy.pop();
-    }
-    return false;
+#ifndef NDEBUG
+    // TODO: We should eventually remove this check.
+    auto ListContains = [this](DGNode *N) {
+      auto ListCopy = List;
+      while (!ListCopy.empty()) {
+        DGNode *Top = ListCopy.top();
+        if (Top == N)
+          return true;
+        ListCopy.pop();
+      }
+      return false;
+    };
+    assert(ListContains(N) == Set.contains(N) && "List and Set out-of-sync!");
+#endif
+    return Set.contains(N);
   }
-  /// \Removes \p N if found in the ready list.
+  /// \Removes \p N if found in the ready list. Note: this is linear time!
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vporpo wrote:

The linear time component is the removal from the PriorityQueue with erase_one() (line 116).

https://github.com/llvm/llvm-project/pull/215418