diff --git a/llvm/include/llvm/IR/Function.h b/llvm/include/llvm/IR/Function.h
--- a/llvm/include/llvm/IR/Function.h
+++ b/llvm/include/llvm/IR/Function.h
@@ -116,6 +116,8 @@
 
   void clearArguments();
 
+  void deleteBodyImpl();
+
   /// Function ctor - If the (optional) Module argument is specified, the
   /// function is automatically inserted into the end of the function list for
   /// the module.
@@ -667,7 +669,7 @@
   /// the linkage to external.
   ///
   void deleteBody() {
-    dropAllReferences();
+    deleteBodyImpl();
     setLinkage(ExternalLinkage);
   }
 
diff --git a/llvm/lib/IR/Function.cpp b/llvm/lib/IR/Function.cpp
--- a/llvm/lib/IR/Function.cpp
+++ b/llvm/lib/IR/Function.cpp
@@ -548,6 +548,32 @@
   clearMetadata();
 }
 
+// This function do almost all the same things as Function::dropAllReferences(),
+// except setting Op<0..3> with PointerNull.
+void Function::deleteBodyImpl() {
+  setIsMaterializable(false);
+
+  for (BasicBlock &BB : *this)
+    BB.dropAllReferences();
+
+  // Delete all basic blocks. They are now unused, except possibly by
+  // blockaddresses, but BasicBlock's destructor takes care of those.
+  while (!BasicBlocks.empty())
+    BasicBlocks.begin()->eraseFromParent();
+
+  // The code needs to match Function::allocHungoffUselist().
+  if (getNumOperands()) {
+    auto *CPN = ConstantPointerNull::get(PointerType::get(getContext(), 0));
+    Op<0>().set(CPN);
+    Op<1>().set(CPN);
+    Op<2>().set(CPN);
+    setValueSubclassData(getSubclassDataFromValue() & ~0xe);
+  }
+
+  // Metadata is stored in a side-table.
+  clearMetadata();
+}
+
 void Function::addAttributeAtIndex(unsigned i, Attribute Attr) {
   AttributeSets = AttributeSets.addAttributeAtIndex(getContext(), i, Attr);
 }