Add an emplace(...) method to llvm::Optional<T>.

[oota-llvm.git] / include / llvm / ADT / MapVector.h

diff --git a/include/llvm/ADT/MapVector.h b/include/llvm/ADT/MapVector.h
index 2eae22c56659bb40d4b295c4d911997486560d65..4e1fc1527270f27e06a7094602a887bbc4041d7b 100644 (file)
--- a/include/llvm/ADT/MapVector.h
+++ b/include/llvm/ADT/MapVector.h
@@ -125,15 +125,57 @@ public:
   }
 
   /// \brief Remove the element given by Iterator.
+  ///
   /// Returns an iterator to the element following the one which was removed,
   /// which may be end().
+  ///
+  /// \note This is a deceivingly expensive operation (linear time).  It's
+  /// usually better to use \a remove_if() if possible.
   typename VectorType::iterator erase(typename VectorType::iterator Iterator) {
-    typename MapType::iterator MapIterator = Map.find(Iterator->first);
-    Map.erase(MapIterator);
-    return Vector.erase(Iterator);
+    Map.erase(Iterator->first);
+    auto Next = Vector.erase(Iterator);
+    if (Next == Vector.end())
+      return Next;
+
+    // Update indices in the map.
+    size_t Index = Next - Vector.begin();
+    for (auto &I : Map) {
+      assert(I.second != Index && "Index was already erased!");
+      if (I.second > Index)
+        --I.second;
+    }
+    return Next;
   }
+
+  /// \brief Remove the elements that match the predicate.
+  ///
+  /// Erase all elements that match \c Pred in a single pass.  Takes linear
+  /// time.
+  template <class Predicate> void remove_if(Predicate Pred);
 };
 
+template <typename KeyT, typename ValueT, typename MapType, typename VectorType>
+template <class Function>
+void MapVector<KeyT, ValueT, MapType, VectorType>::remove_if(Function Pred) {
+  auto O = Vector.begin();
+  for (auto I = O, E = Vector.end(); I != E; ++I) {
+    if (Pred(*I)) {
+      // Erase from the map.
+      Map.erase(I->first);
+      continue;
+    }
+
+    if (I != O) {
+      // Move the value and update the index in the map.
+      *O = std::move(*I);
+      Map[O->first] = O - Vector.begin();
+    }
+    ++O;
+  }
+  // Erase trailing entries in the vector.
+  Vector.erase(O, Vector.end());
 }
 
+} // end namespace llvm
+
 #endif