Index: lib/IR/AsmWriter.cpp
===================================================================
--- lib/IR/AsmWriter.cpp
+++ lib/IR/AsmWriter.cpp
@@ -3148,7 +3148,7 @@
   if (MDs.empty())
     return;
 
-  if (MDNames.empty())
+  if (TheModule && MDNames.empty())
     TheModule->getMDKindNames(MDNames);
 
   for (const auto &I : MDs) {
Index: unittests/IR/AsmWriterTest.cpp
===================================================================
--- /dev/null
+++ unittests/IR/AsmWriterTest.cpp
@@ -0,0 +1,58 @@
+//===- llvm/unittest/IR/AsmWriter.cpp - AsmWriter tests -------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/MDBuilder.h"
+#include "llvm/IR/Module.h"
+#include "gtest/gtest.h"
+
+using namespace llvm;
+
+namespace {
+
+TEST(AsmWriterTest, DebugPrintDetachedInstruction) {
+  LLVMContext Ctx;
+  Module Mod("MyModule", Ctx);
+
+  // Create a tiny function with a couple of instructions.
+  FunctionType *FTy = FunctionType::get(Type::getVoidTy(Ctx),
+                                           /*isVarArg=*/false);
+  Function *F = Function::Create(FTy, Function::ExternalLinkage, "", &Mod);
+  BasicBlock *BB = BasicBlock::Create(Ctx, "", F);
+
+  // Final instruction has branch weight meta-data so as to trigger
+  // the bug in question.
+  IRBuilder<> IBuilder(BB);
+  BasicBlock *TBB = BasicBlock::Create(Ctx, "", F);
+  BasicBlock *FBB = BasicBlock::Create(Ctx, "", F);
+  MDBuilder MDB(Ctx);
+  MDNode *Weights = MDB.createBranchWeights(42, 13);
+  Value *VT = IBuilder.getTrue();
+  AllocaInst *Alloca1 = IBuilder.CreateAlloca(IBuilder.getInt32Ty());
+  BranchInst *BI = IBuilder.CreateCondBr(VT, TBB, FBB, Weights);
+
+  // PR24852: Insure that an instruction can be printed even when it
+  // has no parent.
+  { std::string S;
+    raw_string_ostream OS(S);
+    BI->print(OS); // with parent
+    EXPECT_EQ(OS.str(), "  br i1 true, label %2, label %3, !prof !0");
+  }
+  BI->removeFromParent();
+  { std::string S;
+    raw_string_ostream OS(S);
+    BI->print(OS); // without parent
+    std::size_t r = OS.str().find("br i1 true, label %2, label %3, !<unknown");
+    EXPECT_TRUE(r != std::string::npos);
+  }
+  BI->insertAfter(Alloca1); // reparent so that it will be cleaned up
+}
+
+}
Index: unittests/IR/CMakeLists.txt
===================================================================
--- unittests/IR/CMakeLists.txt
+++ unittests/IR/CMakeLists.txt
@@ -6,6 +6,7 @@
   )
 
 set(IRSources
+  AsmWriterTest.cpp
   AttributesTest.cpp
   ConstantRangeTest.cpp
   ConstantsTest.cpp