Index: include/llvm/Transforms/Utils/Cloning.h
===================================================================
--- include/llvm/Transforms/Utils/Cloning.h
+++ include/llvm/Transforms/Utils/Cloning.h
@@ -144,7 +144,8 @@
                        const char *NameSuffix = "",
                        ClonedCodeInfo *CodeInfo = nullptr,
                        ValueMapTypeRemapper *TypeMapper = nullptr,
-                       ValueMaterializer *Materializer = nullptr);
+                       ValueMaterializer *Materializer = nullptr,
+                       bool ExtractingFunctions = false);
 
 void CloneAndPruneIntoFromInst(Function *NewFunc, const Function *OldFunc,
                                const Instruction *StartingInst,
Index: lib/Transforms/IPO/MergeSimilarFunctions.cpp
===================================================================
--- lib/Transforms/IPO/MergeSimilarFunctions.cpp
+++ lib/Transforms/IPO/MergeSimilarFunctions.cpp
@@ -1847,7 +1847,8 @@
   (*DestI).setName("__merge_arg");
 
   SmallVector<ReturnInst*, 8> Returns;
-  CloneFunctionInto(NewF, F1, VMap, false, Returns);
+  CloneFunctionInto(NewF, F1, VMap, false, Returns, "", nullptr, nullptr,
+                    nullptr, true);
   // Set linkage to set visibility to default.
   NewF->setLinkage(GlobalValue::InternalLinkage);
 
Index: lib/Transforms/Utils/CloneFunction.cpp
===================================================================
--- lib/Transforms/Utils/CloneFunction.cpp
+++ lib/Transforms/Utils/CloneFunction.cpp
@@ -97,7 +97,8 @@
                              SmallVectorImpl<ReturnInst*> &Returns,
                              const char *NameSuffix, ClonedCodeInfo *CodeInfo,
                              ValueMapTypeRemapper *TypeMapper,
-                             ValueMaterializer *Materializer) {
+                             ValueMaterializer *Materializer,
+                             bool ExtractingFunction) {
   assert(NameSuffix && "NameSuffix cannot be null!");
 
 #ifndef NDEBUG
@@ -133,7 +134,7 @@
       AttributeList::get(NewFunc->getContext(), OldAttrs.getFnAttributes(),
                          OldAttrs.getRetAttributes(), NewArgAttrs));
 
-  bool MustCloneSP =
+  bool MustCloneSP = !ExtractingFunction &&
       OldFunc->getParent() && OldFunc->getParent() == NewFunc->getParent();
   DISubprogram *SP = OldFunc->getSubprogram();
   if (SP) {
Index: test/Transforms/MergeSimilarFunc/merge-debug-info-2.ll
===================================================================
--- /dev/null
+++ test/Transforms/MergeSimilarFunc/merge-debug-info-2.ll
@@ -0,0 +1,133 @@
+; RUN: opt -S -mergesimilarfunc < %s | FileCheck %s
+; This used to fail with assertion in CloneFunction
+; REQUIRES: asserts
+; CHECK-LABEL: @foo__merged(
+
+target datalayout = "e-m:o-i64:64-i128:128-n32:64-S128"
+target triple = "arm64-apple-ios8.0.0"
+
+%struct.wibble = type { %struct.wibble.0*, %struct.wibble* }
+%struct.wibble.0 = type { i64*, i8*, i64*, i64*, %struct.eggs*, %struct.wibble* }
+%struct.eggs = type { %struct.wombat*, %struct.eggs* }
+%struct.wombat = type { i8*, %struct.blam*, %struct.blam* }
+%struct.blam = type { i8*, %struct.blam* }
+%struct.snork = type { %struct.bar*, %struct.snork* }
+%struct.bar = type { i64*, i8* }
+
+; Function Attrs: argmemonly nounwind
+declare void @llvm.lifetime.start.p0i8(i64, i8* nocapture) #0
+
+; Function Attrs: minsize nounwind optsize ssp uwtable
+define hidden void @foo(%struct.wibble* %arg) #1 align 2 !dbg !4 {
+bb:
+  %tmp = alloca %struct.wibble*, align 8
+  %tmp1 = alloca %struct.wibble*, align 8
+  store %struct.wibble* %arg, %struct.wibble** %tmp, align 8
+  %tmp2 = load %struct.wibble*, %struct.wibble** %tmp, align 8, !dbg !12
+  %tmp3 = icmp ne %struct.wibble* %tmp2, null, !dbg !13
+  br i1 %tmp3, label %bb4, label %bb13, !dbg !14
+
+bb4:                                              ; preds = %bb
+  %tmp5 = bitcast %struct.wibble** %tmp1 to i8*, !dbg !15
+  call void @llvm.lifetime.start.p0i8(i64 8, i8* %tmp5) #2, !dbg !15
+  %tmp6 = load %struct.wibble*, %struct.wibble** %tmp, align 8, !dbg !16
+  store %struct.wibble* %tmp6, %struct.wibble** %tmp1, align 8, !dbg !17
+  %tmp7 = load %struct.wibble*, %struct.wibble** %tmp, align 8, !dbg !18
+  %tmp8 = getelementptr inbounds %struct.wibble, %struct.wibble* %tmp7, i32 0, i32 1, !dbg !19
+  %tmp9 = load %struct.wibble*, %struct.wibble** %tmp8, align 8, !dbg !19
+  store %struct.wibble* %tmp9, %struct.wibble** %tmp, align 8, !dbg !22
+  call void @foo.1() #3, !dbg !26
+  unreachable
+
+bb13:                                             ; preds = %bb
+  ret void, !dbg !27
+}
+
+; Function Attrs: minsize nounwind optsize ssp uwtable
+declare hidden void @foo.1() #1 align 2
+
+; Function Attrs: minsize nounwind optsize ssp uwtable
+define void @quux() unnamed_addr #1 align 2 !dbg !28 {
+bb:
+  ret void
+}
+
+; Function Attrs: minsize nounwind optsize ssp uwtable
+define hidden void @baz(%struct.snork* %arg) #1 align 2 !dbg !30 {
+bb:
+  %tmp = alloca %struct.snork*, align 8
+  %tmp1 = alloca %struct.snork*, align 8
+  store %struct.snork* %arg, %struct.snork** %tmp, align 8
+  %tmp2 = load %struct.snork*, %struct.snork** %tmp, align 8, !dbg !31
+  %tmp3 = icmp ne %struct.snork* %tmp2, null, !dbg !32
+  br i1 %tmp3, label %bb4, label %bb13, !dbg !33
+
+bb4:                                              ; preds = %bb
+  %tmp5 = bitcast %struct.snork** %tmp1 to i8*, !dbg !34
+  call void @llvm.lifetime.start.p0i8(i64 8, i8* %tmp5) #2, !dbg !34
+  %tmp6 = load %struct.snork*, %struct.snork** %tmp, align 8, !dbg !35
+  store %struct.snork* %tmp6, %struct.snork** %tmp1, align 8, !dbg !36
+  %tmp7 = load %struct.snork*, %struct.snork** %tmp, align 8, !dbg !37
+  %tmp8 = getelementptr inbounds %struct.snork, %struct.snork* %tmp7, i32 0, i32 1, !dbg !38
+  %tmp9 = load %struct.snork*, %struct.snork** %tmp8, align 8, !dbg !38
+  store %struct.snork* %tmp9, %struct.snork** %tmp, align 8, !dbg !39
+  call void @blam() #3, !dbg !42
+  unreachable
+
+bb13:                                             ; preds = %bb
+  ret void, !dbg !43
+}
+
+; Function Attrs: minsize nounwind optsize ssp uwtable
+declare hidden void @blam() #1 align 2
+
+attributes #0 = { argmemonly nounwind }
+attributes #1 = { minsize nounwind optsize ssp uwtable }
+attributes #2 = { nounwind }
+attributes #3 = { minsize optsize }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!2, !3}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "(based on LLVM 5.0.0)", isOptimized: true, runtimeVersion: 0, emissionKind: LineTablesOnly)
+!1 = !DIFile(filename: "foo.cpp", directory: "/")
+!2 = !{i32 2, !"Debug Info Version", i32 3}
+!3 = !{i32 7, !"PIC Level", i32 2}
+!4 = distinct !DISubprogram(name: "delete", scope: !5, file: !5, line: 31, type: !6, isLocal: false, isDefinition: true, scopeLine: 32, flags: DIFlagPrototyped, isOptimized: true, unit: !0)
+!5 = !DIFile(filename: "foo.h", directory: "/")
+!6 = !DISubroutineType(types: !7)
+!7 = !{}
+!9 = !{!"any pointer", !10, i64 0}
+!10 = !{!"omnipotent char", !11, i64 0}
+!11 = !{!"Simple C++ TBAA"}
+!12 = !DILocation(line: 33, column: 11, scope: !4)
+!13 = !DILocation(line: 33, column: 16, scope: !4)
+!14 = !DILocation(line: 33, column: 5, scope: !4)
+!15 = !DILocation(line: 34, column: 7, scope: !4)
+!16 = !DILocation(line: 34, column: 25, scope: !4)
+!17 = !DILocation(line: 34, column: 18, scope: !4)
+!18 = !DILocation(line: 35, column: 14, scope: !4)
+!19 = !DILocation(line: 35, column: 20, scope: !4)
+!21 = !{!"_ZTSN", !9, i64 0, !9, i64 8}
+!22 = !DILocation(line: 35, column: 12, scope: !4)
+!23 = !DILocation(line: 37, column: 25, scope: !4)
+!24 = !DILocation(line: 37, column: 31, scope: !4)
+!25 = !{!21, !9, i64 0}
+!26 = !DILocation(line: 37, column: 7, scope: !4)
+!27 = !DILocation(line: 41, column: 3, scope: !4)
+!28 = distinct !DISubprogram(name: "~destruct", scope: !29, file: !29, line: 31, type: !6, isLocal: false, isDefinition: true, scopeLine: 32, flags: DIFlagPrototyped, isOptimized: true, unit: !0)
+!29 = !DIFile(filename: "bar.h", directory: "/")
+!30 = distinct !DISubprogram(name: "delete", scope: !5, file: !5, line: 31, type: !6, isLocal: false, isDefinition: true, scopeLine: 32, flags: DIFlagPrototyped, isOptimized: true, unit: !0)
+!31 = !DILocation(line: 33, column: 11, scope: !30)
+!32 = !DILocation(line: 33, column: 16, scope: !30)
+!33 = !DILocation(line: 33, column: 5, scope: !30)
+!34 = !DILocation(line: 34, column: 7, scope: !30)
+!35 = !DILocation(line: 34, column: 25, scope: !30)
+!36 = !DILocation(line: 34, column: 18, scope: !30)
+!37 = !DILocation(line: 35, column: 14, scope: !30)
+!38 = !DILocation(line: 35, column: 20, scope: !30)
+!39 = !DILocation(line: 35, column: 12, scope: !30)
+!40 = !DILocation(line: 37, column: 25, scope: !30)
+!41 = !DILocation(line: 37, column: 31, scope: !30)
+!42 = !DILocation(line: 37, column: 7, scope: !30)
+!43 = !DILocation(line: 41, column: 3, scope: !30)