diff --git a/llvm/include/llvm/ADT/IntervalMap.h b/llvm/include/llvm/ADT/IntervalMap.h
--- a/llvm/include/llvm/ADT/IntervalMap.h
+++ b/llvm/include/llvm/ADT/IntervalMap.h
@@ -1042,6 +1042,16 @@
     new(&rootLeaf()) RootLeaf();
   }
 
+  IntervalMap(const IntervalMap &Other)
+      : height(Other.height), rootSize(Other.rootSize),
+        allocator(Other.allocator) {
+    if (Other.branched()) {
+      new (&rootBranchData()) RootBranchData(Other.rootBranchData());
+    } else {
+      new (&rootLeaf()) RootLeaf(Other.rootLeaf());
+    }
+  }
+
   ~IntervalMap() {
     clear();
     rootLeaf().~RootLeaf();