Index: mlir/include/mlir/IR/Region.h
===================================================================
--- mlir/include/mlir/IR/Region.h
+++ mlir/include/mlir/IR/Region.h
@@ -235,6 +235,7 @@
   /// Takes body of another region (that region will have no body after this
   /// operation completes).  The current body of this region is cleared.
   void takeBody(Region &other) {
+    dropAllReferences();
     blocks.clear();
     blocks.splice(blocks.end(), other.getBlocks());
   }
Index: mlir/test/IR/test-take-body.mlir
===================================================================
--- /dev/null
+++ mlir/test/IR/test-take-body.mlir
@@ -0,0 +1,23 @@
+// RUN: mlir-opt -allow-unregistered-dialect %s --test-take-body -split-input-file
+
+func @foo() {
+  %0 = "test.foo"() : () -> i32
+  cf.br ^header
+	
+^header:
+  cf.br ^body
+
+^body:
+  "test.use"(%0) : (i32) -> ()
+  cf.br ^header
+}
+
+func private @bar() {
+  return
+}
+
+// CHECK-LABEL: func @foo
+// CHECK-NEXT: return
+
+// CHECK-LABEL: func private @bar()
+// CHECK-NOT: {
Index: mlir/test/lib/IR/CMakeLists.txt
===================================================================
--- mlir/test/lib/IR/CMakeLists.txt
+++ mlir/test/lib/IR/CMakeLists.txt
@@ -15,6 +15,7 @@
   TestSideEffects.cpp
   TestSlicing.cpp
   TestSymbolUses.cpp
+  TestTakeBody.cpp
   TestTypes.cpp
   TestVisitors.cpp
   TestVisitorsGeneric.cpp
Index: mlir/test/lib/IR/TestTakeBody.cpp
===================================================================
--- /dev/null
+++ mlir/test/lib/IR/TestTakeBody.cpp
@@ -0,0 +1,43 @@
+//===- TestTakeBody.cpp - Pass to test Region's takeBody ------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "TestDialect.h"
+#include "mlir/IR/BuiltinOps.h"
+#include "mlir/Pass/Pass.h"
+
+using namespace mlir;
+
+namespace {
+/// This is a test pass that tests Region's takeBody method by making the first
+/// function take the body of the second.
+struct TakeBodyPass
+    : public PassWrapper<TakeBodyPass, OperationPass<ModuleOp>> {
+  MLIR_DEFINE_EXPLICIT_INTERNAL_INLINE_TYPE_ID(TakeBodyPass)
+
+  StringRef getArgument() const final { return "test-take-body"; }
+  StringRef getDescription() const final { return "Test Region's takeBody"; }
+
+  void runOnOperation() override {
+    auto module = getOperation();
+
+    SmallVector<FuncOp> functions = llvm::to_vector(module.getOps<FuncOp>());
+    if (functions.size() != 2) {
+      module.emitError("Expected only two functions in test");
+      signalPassFailure();
+      return;
+    }
+
+    functions[0].getBody().takeBody(functions[1].getBody());
+  }
+};
+
+} // namespace
+
+namespace mlir {
+void registerTakeBodyTestPasses() { PassRegistration<TakeBodyPass>(); }
+} // namespace mlir
Index: mlir/tools/mlir-opt/mlir-opt.cpp
===================================================================
--- mlir/tools/mlir-opt/mlir-opt.cpp
+++ mlir/tools/mlir-opt/mlir-opt.cpp
@@ -37,6 +37,7 @@
 void registerSideEffectTestPasses();
 void registerSliceAnalysisTestPass();
 void registerSymbolTestPasses();
+void registerTakeBodyTestPasses();
 void registerTestAffineDataCopyPass();
 void registerTestAffineLoopUnswitchingPass();
 void registerTestAllReduceLoweringPass();
@@ -128,6 +129,7 @@
   registerSideEffectTestPasses();
   registerSliceAnalysisTestPass();
   registerSymbolTestPasses();
+  registerTakeBodyTestPasses();
   registerTestAffineDataCopyPass();
   registerTestAffineLoopUnswitchingPass();
   registerTestAllReduceLoweringPass();