Index: docs/LangRef.rst
===================================================================
--- docs/LangRef.rst
+++ docs/LangRef.rst
@@ -4666,6 +4666,10 @@
   here, respectively) of the variable fragment from the working expression. Note
   that contrary to DW_OP_bit_piece, the offset is describing the location
   within the described source variable.
+- ``DW_OP_LLVM_convert, 16, DW_ATE_signed`` specifies a bit size and encoding
+  (``16`` and ``DW_ATE_signed`` here, respectively) to which the top of the
+  expression stack is to be converted. Maps into a ``DW_OP_convert`` operation
+  that references a base type constructed from the supplied values.
 - ``DW_OP_swap`` swaps top two stack entries.
 - ``DW_OP_xderef`` provides extended dereference mechanism. The entry at the top
   of the stack is treated as an address. The second stack entry is treated as an
Index: include/llvm/BinaryFormat/Dwarf.h
===================================================================
--- include/llvm/BinaryFormat/Dwarf.h
+++ include/llvm/BinaryFormat/Dwarf.h
@@ -129,7 +129,8 @@
 #include "llvm/BinaryFormat/Dwarf.def"
   DW_OP_lo_user = 0xe0,
   DW_OP_hi_user = 0xff,
-  DW_OP_LLVM_fragment = 0x1000 ///< Only used in LLVM metadata.
+  DW_OP_LLVM_fragment = 0x1000, ///< Only used in LLVM metadata.
+  DW_OP_LLVM_convert  = 0x1001  ///< Only used in LLVM metadata.
 };
 
 enum TypeKind : uint8_t {
Index: include/llvm/CodeGen/AsmPrinter.h
===================================================================
--- include/llvm/CodeGen/AsmPrinter.h
+++ include/llvm/CodeGen/AsmPrinter.h
@@ -510,7 +510,7 @@
   void EmitSLEB128(int64_t Value, const char *Desc = nullptr) const;
 
   /// Emit the specified unsigned leb128 value.
-  void EmitULEB128(uint64_t Value, const char *Desc = nullptr) const;
+  void EmitULEB128(uint64_t Value, const char *Desc = nullptr, unsigned PadTo = 0) const;
 
   /// Emit a .byte 42 directive that corresponds to an encoding.  If verbose
   /// assembly output is enabled, we output comments describing the encoding.
Index: include/llvm/CodeGen/DIE.h
===================================================================
--- include/llvm/CodeGen/DIE.h
+++ include/llvm/CodeGen/DIE.h
@@ -38,6 +38,7 @@
 class AsmPrinter;
 class DIE;
 class DIEUnit;
+class DwarfCompileUnit;
 class MCExpr;
 class MCSection;
 class MCSymbol;
@@ -229,6 +230,23 @@
   void print(raw_ostream &O) const;
 };
 
+//===--------------------------------------------------------------------===//
+/// A BaseTypeRef DIE.
+class DIEBaseTypeRef {
+  const DwarfCompileUnit *CU;
+  const uint64_t Index;
+  static constexpr unsigned ULEB128PadSize = 4;
+
+public:
+  explicit DIEBaseTypeRef(const DwarfCompileUnit *TheCU, uint64_t Idx)
+    : CU(TheCU), Index(Idx) {}
+
+  void EmitValue(const AsmPrinter *AP, dwarf::Form Form) const;
+  unsigned SizeOf(const AsmPrinter *AP, dwarf::Form Form) const;
+
+  void print(raw_ostream &O) const;
+};
+
 //===--------------------------------------------------------------------===//
 /// A simple label difference DIE.
 ///
@@ -349,7 +367,7 @@
   /// should be stored by reference instead of by value.
   using ValTy = AlignedCharArrayUnion<DIEInteger, DIEString, DIEExpr, DIELabel,
                                       DIEDelta *, DIEEntry, DIEBlock *,
-                                      DIELoc *, DIELocList>;
+                                      DIELoc *, DIELocList, DIEBaseTypeRef *>;
 
   static_assert(sizeof(ValTy) <= sizeof(uint64_t) ||
                     sizeof(ValTy) <= sizeof(void *),
@@ -501,6 +519,18 @@
     }
     Last = &N;
   }
+
+  void push_front(Node &N) {
+    assert(N.Next.getPointer() == &N && "Expected unlinked node");
+    assert(N.Next.getInt() == true && "Expected unlinked node");
+
+    if (Last) {
+      N.Next.setPointerAndInt(Last->Next.getPointer(), false);
+      Last->Next.setPointerAndInt(&N, true);
+    } else {
+      Last = &N;
+    }
+  }
 };
 
 template <class T> class IntrusiveBackList : IntrusiveBackListBase {
@@ -508,8 +538,15 @@
   using IntrusiveBackListBase::empty;
 
   void push_back(T &N) { IntrusiveBackListBase::push_back(N); }
+  void push_front(T &N) { IntrusiveBackListBase::push_front(N); }
   T &back() { return *static_cast<T *>(Last); }
   const T &back() const { return *static_cast<T *>(Last); }
+  T &front() {
+    return *static_cast<T *>(Last ? Last->Next.getPointer() : nullptr);
+  }
+  const T &front() const {
+    return *static_cast<T *>(Last ? Last->Next.getPointer() : nullptr);
+  }
 
   class const_iterator;
   class iterator
@@ -772,6 +809,13 @@
     return Children.back();
   }
 
+  DIE &addChildFront(DIE *Child) {
+    assert(!Child->getParent() && "Child should be orphaned");
+    Child->Owner = this;
+    Children.push_front(*Child);
+    return Children.front();
+  }
+
   /// Find a value in the DIE with the attribute given.
   ///
   /// Returns a default-constructed DIEValue (where \a DIEValue::getType()
Index: include/llvm/CodeGen/DIEValue.def
===================================================================
--- include/llvm/CodeGen/DIEValue.def
+++ include/llvm/CodeGen/DIEValue.def
@@ -34,6 +34,7 @@
 HANDLE_DIEVALUE_SMALL(String)
 HANDLE_DIEVALUE_SMALL(Expr)
 HANDLE_DIEVALUE_SMALL(Label)
+HANDLE_DIEVALUE_SMALL(BaseTypeRef)
 HANDLE_DIEVALUE_LARGE(Delta)
 HANDLE_DIEVALUE_SMALL(Entry)
 HANDLE_DIEVALUE_LARGE(Block)
Index: include/llvm/MC/MCStreamer.h
===================================================================
--- include/llvm/MC/MCStreamer.h
+++ include/llvm/MC/MCStreamer.h
@@ -634,7 +634,7 @@
 
   /// Special case of EmitULEB128Value that avoids the client having to
   /// pass in a MCExpr for constant integers.
-  void EmitULEB128IntValue(uint64_t Value);
+  void EmitULEB128IntValue(uint64_t Value, unsigned PadTo = 0);
 
   /// Special case of EmitSLEB128Value that avoids the client having to
   /// pass in a MCExpr for constant integers.
Index: lib/AsmParser/LLParser.cpp
===================================================================
--- lib/AsmParser/LLParser.cpp
+++ lib/AsmParser/LLParser.cpp
@@ -4835,6 +4835,15 @@
         return TokError(Twine("invalid DWARF op '") + Lex.getStrVal() + "'");
       }
 
+      if (Lex.getKind() == lltok::DwarfAttEncoding) {
+        if (unsigned Op = dwarf::getAttributeEncoding(Lex.getStrVal())) {
+          Lex.Lex();
+          Elements.push_back(Op);
+          continue;
+        }
+        return TokError(Twine("invalid DWARF attribute encoding '") + Lex.getStrVal() + "'");
+      }
+
       if (Lex.getKind() != lltok::APSInt || Lex.getAPSIntVal().isSigned())
         return TokError("expected unsigned integer");
 
Index: lib/BinaryFormat/Dwarf.cpp
===================================================================
--- lib/BinaryFormat/Dwarf.cpp
+++ lib/BinaryFormat/Dwarf.cpp
@@ -143,6 +143,8 @@
   case DW_OP_##NAME:                                                           \
     return "DW_OP_" #NAME;
 #include "llvm/BinaryFormat/Dwarf.def"
+  case DW_OP_LLVM_convert:
+    return "DW_OP_LLVM_convert";
   case DW_OP_LLVM_fragment:
     return "DW_OP_LLVM_fragment";
   }
@@ -153,6 +155,7 @@
 #define HANDLE_DW_OP(ID, NAME, VERSION, VENDOR)                                \
   .Case("DW_OP_" #NAME, DW_OP_##NAME)
 #include "llvm/BinaryFormat/Dwarf.def"
+      .Case("DW_OP_LLVM_convert", DW_OP_LLVM_convert)
       .Case("DW_OP_LLVM_fragment", DW_OP_LLVM_fragment)
       .Default(0);
 }
Index: lib/CodeGen/AsmPrinter/AsmPrinterDwarf.cpp
===================================================================
--- lib/CodeGen/AsmPrinter/AsmPrinterDwarf.cpp
+++ lib/CodeGen/AsmPrinter/AsmPrinterDwarf.cpp
@@ -42,11 +42,11 @@
   OutStreamer->EmitSLEB128IntValue(Value);
 }
 
-void AsmPrinter::EmitULEB128(uint64_t Value, const char *Desc) const {
+void AsmPrinter::EmitULEB128(uint64_t Value, const char *Desc, unsigned PadTo) const {
   if (isVerbose() && Desc)
     OutStreamer->AddComment(Desc);
 
-  OutStreamer->EmitULEB128IntValue(Value);
+  OutStreamer->EmitULEB128IntValue(Value, PadTo);
 }
 
 /// Emit something like ".uleb128 Hi-Lo".
Index: lib/CodeGen/AsmPrinter/ByteStreamer.h
===================================================================
--- lib/CodeGen/AsmPrinter/ByteStreamer.h
+++ lib/CodeGen/AsmPrinter/ByteStreamer.h
@@ -31,7 +31,7 @@
   // For now we're just handling the calls we need for dwarf emission/hashing.
   virtual void EmitInt8(uint8_t Byte, const Twine &Comment = "") = 0;
   virtual void EmitSLEB128(uint64_t DWord, const Twine &Comment = "") = 0;
-  virtual void EmitULEB128(uint64_t DWord, const Twine &Comment = "") = 0;
+  virtual void EmitULEB128(uint64_t DWord, const Twine &Comment = "", unsigned PadTo = 0) = 0;
 };
 
 class APByteStreamer final : public ByteStreamer {
@@ -48,7 +48,7 @@
     AP.OutStreamer->AddComment(Comment);
     AP.EmitSLEB128(DWord);
   }
-  void EmitULEB128(uint64_t DWord, const Twine &Comment) override {
+  void EmitULEB128(uint64_t DWord, const Twine &Comment, unsigned PadTo) override {
     AP.OutStreamer->AddComment(Comment);
     AP.EmitULEB128(DWord);
   }
@@ -65,7 +65,7 @@
   void EmitSLEB128(uint64_t DWord, const Twine &Comment) override {
     Hash.addSLEB128(DWord);
   }
-  void EmitULEB128(uint64_t DWord, const Twine &Comment) override {
+  void EmitULEB128(uint64_t DWord, const Twine &Comment, unsigned PadTo) override {
     Hash.addULEB128(DWord);
   }
 };
@@ -102,9 +102,9 @@
 
     }
   }
-  void EmitULEB128(uint64_t DWord, const Twine &Comment) override {
+  void EmitULEB128(uint64_t DWord, const Twine &Comment, unsigned PadTo) override {
     raw_svector_ostream OSE(Buffer);
-    unsigned Length = encodeULEB128(DWord, OSE);
+    unsigned Length = encodeULEB128(DWord, OSE, PadTo);
     if (GenerateComments) {
       Comments.push_back(Comment.str());
       // Add some empty comments to keep the Buffer and Comments vectors aligned
Index: lib/CodeGen/AsmPrinter/DIE.cpp
===================================================================
--- lib/CodeGen/AsmPrinter/DIE.cpp
+++ lib/CodeGen/AsmPrinter/DIE.cpp
@@ -505,6 +505,27 @@
 LLVM_DUMP_METHOD
 void DIELabel::print(raw_ostream &O) const { O << "Lbl: " << Label->getName(); }
 
+//===----------------------------------------------------------------------===//
+// DIEBaseTypeRef Implementation
+//===----------------------------------------------------------------------===//
+
+/// EmitValue - Emit base type reference.
+///
+void DIEBaseTypeRef::EmitValue(const AsmPrinter *AP, dwarf::Form Form) const {
+  uint64_t Offset = CU->ExprRefedBaseTypes[Index].Die->getOffset();
+  assert(Offset < (1ULL << (ULEB128PadSize * 7)) && "Offset wont fit");
+  AP->EmitULEB128(Offset, nullptr, ULEB128PadSize);
+}
+
+/// SizeOf - Determine size of the base type reference in bytes.
+///
+unsigned DIEBaseTypeRef::SizeOf(const AsmPrinter *AP, dwarf::Form Form) const {
+  return ULEB128PadSize;
+}
+
+LLVM_DUMP_METHOD
+void DIEBaseTypeRef::print(raw_ostream &O) const { O << "BaseTypeRef: " << Index; }
+
 //===----------------------------------------------------------------------===//
 // DIEDelta Implementation
 //===----------------------------------------------------------------------===//
Index: lib/CodeGen/AsmPrinter/DIEHash.cpp
===================================================================
--- lib/CodeGen/AsmPrinter/DIEHash.cpp
+++ lib/CodeGen/AsmPrinter/DIEHash.cpp
@@ -225,7 +225,7 @@
   DwarfDebug &DD = *AP->getDwarfDebug();
   const DebugLocStream &Locs = DD.getDebugLocs();
   for (const auto &Entry : Locs.getEntries(Locs.getList(LocList.getValue())))
-    DD.emitDebugLocEntry(Streamer, Entry);
+    DD.emitDebugLocEntry(Streamer, Entry, nullptr);
 }
 
 // Hash an individual attribute \param Attr based on the type of attribute and
@@ -309,6 +309,7 @@
     // FIXME: It's uncertain whether or not we should handle this at the moment.
   case DIEValue::isExpr:
   case DIEValue::isLabel:
+  case DIEValue::isBaseTypeRef:
   case DIEValue::isDelta:
     llvm_unreachable("Add support for additional value types.");
   }
Index: lib/CodeGen/AsmPrinter/DebugLocEntry.h
===================================================================
--- lib/CodeGen/AsmPrinter/DebugLocEntry.h
+++ lib/CodeGen/AsmPrinter/DebugLocEntry.h
@@ -148,8 +148,10 @@
   }
 
   /// Lower this entry into a DWARF expression.
-  void finalize(const AsmPrinter &AP, DebugLocStream::ListBuilder &List,
-                const DIBasicType *BT);
+  void finalize(const AsmPrinter &AP,
+                DebugLocStream::ListBuilder &List,
+                const DIBasicType *BT,
+                DwarfCompileUnit &TheCU);
 };
 
 /// Compare two Values for equality.
Index: lib/CodeGen/AsmPrinter/DwarfCompileUnit.h
===================================================================
--- lib/CodeGen/AsmPrinter/DwarfCompileUnit.h
+++ lib/CodeGen/AsmPrinter/DwarfCompileUnit.h
@@ -124,6 +124,16 @@
     const DIExpression *Expr;
   };
 
+  struct BaseTypeRef {
+    BaseTypeRef(unsigned BitSize, dwarf::TypeKind Encoding) :
+      BitSize(BitSize), Encoding(Encoding) {}
+    unsigned BitSize;
+    dwarf::TypeKind Encoding;
+    DIE *Die = nullptr;
+  };
+
+  std::vector<BaseTypeRef> ExprRefedBaseTypes;
+
   /// Get or create global variable DIE.
   DIE *
   getOrCreateGlobalVariableDIE(const DIGlobalVariable *GV,
@@ -199,6 +209,8 @@
                               SmallVectorImpl<DIE *> &Children,
                               bool *HasNonScopeChildren = nullptr);
 
+  void createBaseTypeDIEs();
+
   /// Construct a DIE for this subprogram scope.
   DIE &constructSubprogramScopeDIE(const DISubprogram *Sub,
                                    LexicalScope *Scope);
@@ -313,6 +325,8 @@
   void setDWOId(uint64_t DwoId) { DWOId = DwoId; }
 
   bool hasDwarfPubSections() const;
+
+  void addBaseTypeRef(DIEValueList &Die, int64_t Idx);
 };
 
 } // end namespace llvm
Index: lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
===================================================================
--- lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
+++ lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
@@ -17,6 +17,7 @@
 #include "DwarfUnit.h"
 #include "llvm/ADT/None.h"
 #include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/BinaryFormat/Dwarf.h"
@@ -1185,3 +1186,24 @@
                                          : dwarf::DW_AT_GNU_addr_base,
                   Label, TLOF.getDwarfAddrSection()->getBeginSymbol());
 }
+
+void DwarfCompileUnit::addBaseTypeRef(DIEValueList &Die, int64_t Idx) {
+  Die.addValue(DIEValueAllocator, (dwarf::Attribute)0, dwarf::DW_FORM_udata,
+               DIEBaseTypeRef(this, Idx));
+}
+
+void DwarfCompileUnit::createBaseTypeDIEs() {
+  // Insert the base type DIEs directly after the CU. Maintain order by
+  // iterating backwards and inserting to the front of CU child list.
+  for (auto &Btr : reverse(ExprRefedBaseTypes)) {
+    DIE &Die = getUnitDie().addChildFront(
+      DIE::get(DIEValueAllocator, dwarf::DW_TAG_base_type));
+    Twine T(dwarf::AttributeEncodingString(Btr.Encoding) + "_" + Twine(Btr.BitSize));
+    SmallString<32> Str;
+    addString(Die, dwarf::DW_AT_name, T.toStringRef(Str));
+    addUInt(Die, dwarf::DW_AT_encoding, dwarf::DW_FORM_data1, Btr.Encoding);
+    addUInt(Die, dwarf::DW_AT_byte_size, None, Btr.BitSize / 8);
+
+    Btr.Die = &Die;
+  }
+}
Index: lib/CodeGen/AsmPrinter/DwarfDebug.h
===================================================================
--- lib/CodeGen/AsmPrinter/DwarfDebug.h
+++ lib/CodeGen/AsmPrinter/DwarfDebug.h
@@ -682,10 +682,12 @@
   /// Emit an entry for the debug loc section. This can be used to
   /// handle an entry that's going to be emitted into the debug loc section.
   void emitDebugLocEntry(ByteStreamer &Streamer,
-                         const DebugLocStream::Entry &Entry);
+                         const DebugLocStream::Entry &Entry,
+                         const DwarfCompileUnit *CU);
 
   /// Emit the location for a debug loc entry, including the size header.
-  void emitDebugLocEntryLocation(const DebugLocStream::Entry &Entry);
+  void emitDebugLocEntryLocation(const DebugLocStream::Entry &Entry,
+                                 const DwarfCompileUnit *CU);
 
   /// Find the MDNode for the given reference.
   template <typename T> T *resolve(TypedDINodeRef<T> Ref) const {
Index: lib/CodeGen/AsmPrinter/DwarfDebug.cpp
===================================================================
--- lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -161,6 +161,7 @@
 static const char *const DWARFGroupDescription = "DWARF Emission";
 static const char *const DbgTimerName = "writer";
 static const char *const DbgTimerDescription = "DWARF Debug Writer";
+static constexpr unsigned ULEB128PadSize = 4;
 
 void DebugLocDwarfExpression::emitOp(uint8_t Op, const char *Comment) {
   BS.EmitInt8(
@@ -176,6 +177,11 @@
   BS.EmitULEB128(Value, Twine(Value));
 }
 
+void DebugLocDwarfExpression::emitBaseTypeRef(uint64_t Idx) {
+  assert(Idx < (1ULL << (ULEB128PadSize * 7)) && "Idx wont fit");
+  BS.EmitULEB128(Idx, Twine(Idx), ULEB128PadSize);
+}
+
 bool DebugLocDwarfExpression::isFrameRegister(const TargetRegisterInfo &TRI,
                                               unsigned MachineReg) {
   // This information is not available while emitting .debug_loc entries.
@@ -940,6 +946,11 @@
   assert(CurFn == nullptr);
   assert(CurMI == nullptr);
 
+  for (const auto &P : CUMap) {
+    auto &CU = *P.second;
+    CU.createBaseTypeDIEs();
+  }
+
   // If we aren't actually generating debug info (check beginModule -
   // conditionalized on !DisableDebugInfoPrinting and the presence of the
   // llvm.dbg.cu metadata node)
@@ -1369,7 +1380,7 @@
 
     // Finalize the entry by lowering it into a DWARF bytestream.
     for (auto &Entry : Entries)
-      Entry.finalize(*Asm, List, BT);
+      Entry.finalize(*Asm, List, BT, TheCU);
   }
 
   // For each InlinedEntity collected from DBG_LABEL instructions, convert to
@@ -1911,13 +1922,108 @@
                      StringOffsetsSection, /* UseRelativeOffsets = */ true);
 }
 
-void DwarfDebug::emitDebugLocEntry(ByteStreamer &Streamer,
-                                   const DebugLocStream::Entry &Entry) {
+void DwarfDebug::emitDebugLocEntry(ByteStreamer &Streamer, const
+                                   DebugLocStream::Entry &Entry,
+                                   const DwarfCompileUnit *CU) {
   auto &&Comments = DebugLocs.getComments(Entry);
   auto Comment = Comments.begin();
   auto End = Comments.end();
-  for (uint8_t Byte : DebugLocs.getBytes(Entry))
-    Streamer.EmitInt8(Byte, Comment != End ? *(Comment++) : "");
+
+  enum {Idle, SkipLEB128, BaseTypeFromULEB128} State = Idle;
+  uint64_t ULEB128Value;
+  uint64_t ULEB128Shift;
+  unsigned NumSkipLEB128s;
+  for (uint8_t Byte : DebugLocs.getBytes(Entry)) {
+    bool EmitByte = true;
+    // XXX: This is admittedly pretty stupid but sadly appears to be the
+    // easiest way to pass custom values as the expressions are inserted into a
+    // byte stream rather early (see DwarfExpression::addExpression).
+    switch (State) {
+    case Idle:
+      switch (Byte) {
+      default:
+        if (dwarf::DW_OP_breg0 <= Byte && Byte <= dwarf::DW_OP_breg0 + 31) {
+          NumSkipLEB128s = 1;
+          State = SkipLEB128;
+        } else if ((dwarf::DW_OP_lit0 <= Byte && Byte <= dwarf::DW_OP_lit0 + 31) ||
+                   (dwarf::DW_OP_reg0 <= Byte && Byte <= dwarf::DW_OP_reg0 + 31)) {
+          // Do nothing.
+        } else {
+          llvm_unreachable("unhandled opcode found in expression");
+        }
+        break;
+        // Ops with 0 arguments.
+      case dwarf::DW_OP_and:
+      case dwarf::DW_OP_deref:
+      case dwarf::DW_OP_div:
+      case dwarf::DW_OP_dup:
+      case dwarf::DW_OP_minus:
+      case dwarf::DW_OP_mod:
+      case dwarf::DW_OP_mul:
+      case dwarf::DW_OP_not:
+      case dwarf::DW_OP_or:
+      case dwarf::DW_OP_plus:
+      case dwarf::DW_OP_shl:
+      case dwarf::DW_OP_shr:
+      case dwarf::DW_OP_shra:
+      case dwarf::DW_OP_stack_value:
+      case dwarf::DW_OP_swap:
+      case dwarf::DW_OP_xderef:
+      case dwarf::DW_OP_xor:
+        // Do nothing.
+        break;
+        // Ops with 2 [SU]LEB128 arguments.
+      case dwarf::DW_OP_bit_piece:
+      case dwarf::DW_OP_bregx:
+        NumSkipLEB128s = 2;
+        State = SkipLEB128;
+        break;
+        // Ops with 1 [SU]LEB128 arguments.
+      case dwarf::DW_OP_consts:
+      case dwarf::DW_OP_constu:
+      case dwarf::DW_OP_fbreg:
+      case dwarf::DW_OP_piece:
+      case dwarf::DW_OP_plus_uconst:
+      case dwarf::DW_OP_regx:
+        NumSkipLEB128s = 1;
+        State = SkipLEB128;
+        break;
+      case dwarf::DW_OP_convert:
+        ULEB128Value = 0;
+        ULEB128Shift = 0;
+        State = BaseTypeFromULEB128;
+        break;
+      }
+      break;
+
+    case SkipLEB128:
+      if (!(Byte & 0x80) && --NumSkipLEB128s == 0)
+        State = Idle;
+      break;
+    case BaseTypeFromULEB128:
+      EmitByte = false;
+      ULEB128Value |= (Byte & 0x7f) << ULEB128Shift;
+      if (Byte & 0x80)
+        ULEB128Shift += 7;
+      else {
+        if (CU) {
+          uint64_t Offset = CU->ExprRefedBaseTypes[ULEB128Value].Die->getOffset();
+          assert(Offset < (1ULL << (ULEB128PadSize * 7)) && "Offset wont fit");
+          Asm->EmitULEB128(Offset, nullptr, ULEB128PadSize);
+        } else {
+          // Emit a reference to the 'generic type'.
+          Asm->EmitULEB128(0);
+        }
+        State = Idle;
+      }
+      if (Comment != End)
+        Comment++;
+      break;
+    }
+
+    if (EmitByte)
+      Streamer.EmitInt8(Byte, Comment != End ? *(Comment++) : "");
+  }
 }
 
 static void emitDebugLocValue(const AsmPrinter &AP, const DIBasicType *BT,
@@ -1951,11 +2057,12 @@
 
 void DebugLocEntry::finalize(const AsmPrinter &AP,
                              DebugLocStream::ListBuilder &List,
-                             const DIBasicType *BT) {
+                             const DIBasicType *BT,
+                             DwarfCompileUnit &TheCU) {
   assert(Begin != End && "unexpected location list entry with empty range");
   DebugLocStream::EntryBuilder Entry(List, Begin, End);
   BufferByteStreamer Streamer = Entry.getStreamer();
-  DebugLocDwarfExpression DwarfExpr(AP.getDwarfVersion(), Streamer);
+  DebugLocDwarfExpression DwarfExpr(AP.getDwarfVersion(), Streamer, TheCU);
   const DebugLocEntry::Value &Value = Values[0];
   if (Value.isFragment()) {
     // Emit all fragments that belong to the same variable and range.
@@ -1975,7 +2082,8 @@
   DwarfExpr.finalize();
 }
 
-void DwarfDebug::emitDebugLocEntryLocation(const DebugLocStream::Entry &Entry) {
+void DwarfDebug::emitDebugLocEntryLocation(const DebugLocStream::Entry &Entry,
+                                           const DwarfCompileUnit *CU) {
   // Emit the size.
   Asm->OutStreamer->AddComment("Loc expr size");
   if (getDwarfVersion() >= 5)
@@ -1984,7 +2092,7 @@
     Asm->emitInt16(DebugLocs.getBytes(Entry).size());
   // Emit the entry.
   APByteStreamer Streamer(*Asm);
-  emitDebugLocEntry(Streamer, Entry);
+  emitDebugLocEntry(Streamer, Entry, CU);
 }
 
 // Emit the common part of the DWARF 5 range/locations list tables header.
@@ -2084,7 +2192,7 @@
           Asm->EmitLabelDifference(Entry.EndSym, Base, Size);
         }
 
-        emitDebugLocEntryLocation(Entry);
+        emitDebugLocEntryLocation(Entry, CU);
         continue;
       }
 
@@ -2105,7 +2213,7 @@
         Asm->OutStreamer->EmitSymbolValue(Entry.EndSym, Size);
       }
 
-      emitDebugLocEntryLocation(Entry);
+      emitDebugLocEntryLocation(Entry, CU);
     }
 
     if (IsLocLists) {
@@ -2141,7 +2249,7 @@
       Asm->EmitULEB128(idx);
       Asm->EmitLabelDifference(Entry.EndSym, Entry.BeginSym, 4);
 
-      emitDebugLocEntryLocation(Entry);
+      emitDebugLocEntryLocation(Entry, List.CU);
     }
     Asm->emitInt8(dwarf::DW_LLE_end_of_list);
   }
Index: lib/CodeGen/AsmPrinter/DwarfExpression.h
===================================================================
--- lib/CodeGen/AsmPrinter/DwarfExpression.h
+++ lib/CodeGen/AsmPrinter/DwarfExpression.h
@@ -27,7 +27,7 @@
 class AsmPrinter;
 class APInt;
 class ByteStreamer;
-class DwarfUnit;
+class DwarfCompileUnit;
 class DIELoc;
 class TargetRegisterInfo;
 
@@ -104,6 +104,8 @@
     const char *Comment;
   };
 
+  DwarfCompileUnit &CU;
+
   /// The register location, if any.
   SmallVector<Register, 2> DwarfRegs;
 
@@ -137,6 +139,8 @@
   /// Emit a raw unsigned value.
   virtual void emitUnsigned(uint64_t Value) = 0;
 
+  virtual void emitBaseTypeRef(uint64_t Idx) = 0;
+
   /// Emit a normalized unsigned constant.
   void emitConstu(uint64_t Value);
 
@@ -199,7 +203,8 @@
   ~DwarfExpression() = default;
 
 public:
-  DwarfExpression(unsigned DwarfVersion) : DwarfVersion(DwarfVersion) {}
+  DwarfExpression(unsigned DwarfVersion, DwarfCompileUnit &CU)
+    : CU(CU), DwarfVersion(DwarfVersion) {}
 
   /// This needs to be called last to commit any pending changes.
   void finalize();
@@ -247,6 +252,9 @@
   /// If applicable, emit an empty DW_OP_piece / DW_OP_bit_piece to advance to
   /// the fragment described by \c Expr.
   void addFragmentOffset(const DIExpression *Expr);
+
+  void emitLegacySExt(unsigned FromBits);
+  void emitLegacyZExt(unsigned FromBits);
 };
 
 /// DwarfExpression implementation for .debug_loc entries.
@@ -256,27 +264,28 @@
   void emitOp(uint8_t Op, const char *Comment = nullptr) override;
   void emitSigned(int64_t Value) override;
   void emitUnsigned(uint64_t Value) override;
+  void emitBaseTypeRef(uint64_t Idx) override;
   bool isFrameRegister(const TargetRegisterInfo &TRI,
                        unsigned MachineReg) override;
 
 public:
-  DebugLocDwarfExpression(unsigned DwarfVersion, ByteStreamer &BS)
-      : DwarfExpression(DwarfVersion), BS(BS) {}
+  DebugLocDwarfExpression(unsigned DwarfVersion, ByteStreamer &BS, DwarfCompileUnit &CU)
+      : DwarfExpression(DwarfVersion, CU), BS(BS) {}
 };
 
 /// DwarfExpression implementation for singular DW_AT_location.
 class DIEDwarfExpression final : public DwarfExpression {
 const AsmPrinter &AP;
-  DwarfUnit &DU;
   DIELoc &DIE;
 
   void emitOp(uint8_t Op, const char *Comment = nullptr) override;
   void emitSigned(int64_t Value) override;
   void emitUnsigned(uint64_t Value) override;
+  void emitBaseTypeRef(uint64_t Idx) override;
   bool isFrameRegister(const TargetRegisterInfo &TRI,
                        unsigned MachineReg) override;
 public:
-  DIEDwarfExpression(const AsmPrinter &AP, DwarfUnit &DU, DIELoc &DIE);
+  DIEDwarfExpression(const AsmPrinter &AP, DwarfCompileUnit &CU, DIELoc &DIE);
 
   DIELoc *finalize() {
     DwarfExpression::finalize();
Index: lib/CodeGen/AsmPrinter/DwarfExpression.cpp
===================================================================
--- lib/CodeGen/AsmPrinter/DwarfExpression.cpp
+++ lib/CodeGen/AsmPrinter/DwarfExpression.cpp
@@ -11,6 +11,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "DwarfExpression.h"
+#include "DwarfCompileUnit.h"
 #include "llvm/ADT/APInt.h"
 #include "llvm/ADT/SmallBitVector.h"
 #include "llvm/BinaryFormat/Dwarf.h"
@@ -23,6 +24,11 @@
 
 using namespace llvm;
 
+static cl::opt<bool> GenerateTypedDwarfExpr(
+  "generate-typed-dwarf5-expr", cl::Hidden,
+  cl::desc("Generate typed DWARF5 expressions regardless of DWARF version targeted."),
+  cl::init(false));
+
 void DwarfExpression::emitConstu(uint64_t Value) {
   if (Value < 32)
     emitOp(dwarf::DW_OP_lit0 + Value);
@@ -318,6 +324,8 @@
   if (SubRegisterSizeInBits && N && (N->getOp() != dwarf::DW_OP_LLVM_fragment))
     maskSubRegister();
 
+  Optional<DIExpression::ExprOperand> PrevConvertOp = None;
+
   while (ExprCursor) {
     auto Op = ExprCursor.take();
     switch (Op->getOp()) {
@@ -384,6 +392,37 @@
       assert(LocationKind != Register);
       emitConstu(Op->getArg(0));
       break;
+    case dwarf::DW_OP_LLVM_convert: {
+      unsigned BitSize = Op->getArg(0);
+      dwarf::TypeKind Encoding = static_cast<dwarf::TypeKind>(Op->getArg(1));
+      if (DwarfVersion >= 5 || GenerateTypedDwarfExpr) {
+        emitOp(dwarf::DW_OP_convert);
+        // XXX: Simply emit the index into the raw byte stream as ULEB128,
+        // DwarfDebug::emitDebugLocEntry has been fitted with means to extract it
+        // later.
+        unsigned I = 0, E = CU.ExprRefedBaseTypes.size();
+        for (; I != E; ++I)
+          if (CU.ExprRefedBaseTypes[I].BitSize == BitSize &&
+              CU.ExprRefedBaseTypes[I].Encoding == Encoding)
+            break;
+
+        if (I == E)
+          CU.ExprRefedBaseTypes.emplace_back(BitSize, Encoding);
+
+        emitBaseTypeRef(I);
+      } else {
+        if (PrevConvertOp && PrevConvertOp->getArg(0) < BitSize) {
+          if (Encoding == dwarf::DW_ATE_signed)
+            emitLegacySExt(PrevConvertOp->getArg(0));
+          else if (Encoding == dwarf::DW_ATE_unsigned)
+            emitLegacyZExt(PrevConvertOp->getArg(0));
+          PrevConvertOp = None;
+        } else {
+          PrevConvertOp = Op;
+        }
+      }
+      break;
+    }
     case dwarf::DW_OP_stack_value:
       LocationKind = Implicit;
       break;
@@ -436,3 +475,25 @@
     addOpPiece(FragmentOffset - OffsetInBits);
   OffsetInBits = FragmentOffset;
 }
+
+void DwarfExpression::emitLegacySExt(unsigned FromBits) {
+  // (((X >> (FromBits - 1)) * (~0)) << FromBits) | X
+  emitOp(dwarf::DW_OP_dup);
+  emitOp(dwarf::DW_OP_constu);
+  emitUnsigned(FromBits - 1);
+  emitOp(dwarf::DW_OP_shr);
+  emitOp(dwarf::DW_OP_lit0);
+  emitOp(dwarf::DW_OP_not);
+  emitOp(dwarf::DW_OP_mul);
+  emitOp(dwarf::DW_OP_constu);
+  emitUnsigned(FromBits);
+  emitOp(dwarf::DW_OP_shl);
+  emitOp(dwarf::DW_OP_or);
+}
+
+void DwarfExpression::emitLegacyZExt(unsigned FromBits) {
+  // (X & (1 << FromBits - 1))
+  emitOp(dwarf::DW_OP_constu);
+  emitUnsigned((1ULL << FromBits) - 1);
+  emitOp(dwarf::DW_OP_and);
+}
Index: lib/CodeGen/AsmPrinter/DwarfFile.h
===================================================================
--- lib/CodeGen/AsmPrinter/DwarfFile.h
+++ lib/CodeGen/AsmPrinter/DwarfFile.h
@@ -147,7 +147,7 @@
   void emitUnits(bool UseOffsets);
 
   /// Emit the given unit to its section.
-  void emitUnit(DwarfUnit *U, bool UseOffsets);
+  void emitUnit(DwarfUnit *TheU, bool UseOffsets);
 
   /// Emit a set of abbreviations to the specific section.
   void emitAbbrevs(MCSection *);
Index: lib/CodeGen/AsmPrinter/DwarfUnit.cpp
===================================================================
--- lib/CodeGen/AsmPrinter/DwarfUnit.cpp
+++ lib/CodeGen/AsmPrinter/DwarfUnit.cpp
@@ -46,21 +46,26 @@
 
 #define DEBUG_TYPE "dwarfdebug"
 
-DIEDwarfExpression::DIEDwarfExpression(const AsmPrinter &AP, DwarfUnit &DU,
+DIEDwarfExpression::DIEDwarfExpression(const AsmPrinter &AP,
+                                       DwarfCompileUnit &CU,
                                        DIELoc &DIE)
-    : DwarfExpression(AP.getDwarfVersion()), AP(AP), DU(DU),
+    : DwarfExpression(AP.getDwarfVersion(), CU), AP(AP),
       DIE(DIE) {}
 
 void DIEDwarfExpression::emitOp(uint8_t Op, const char* Comment) {
-  DU.addUInt(DIE, dwarf::DW_FORM_data1, Op);
+  CU.addUInt(DIE, dwarf::DW_FORM_data1, Op);
 }
 
 void DIEDwarfExpression::emitSigned(int64_t Value) {
-  DU.addSInt(DIE, dwarf::DW_FORM_sdata, Value);
+  CU.addSInt(DIE, dwarf::DW_FORM_sdata, Value);
 }
 
 void DIEDwarfExpression::emitUnsigned(uint64_t Value) {
-  DU.addUInt(DIE, dwarf::DW_FORM_udata, Value);
+  CU.addUInt(DIE, dwarf::DW_FORM_udata, Value);
+}
+
+void DIEDwarfExpression::emitBaseTypeRef(uint64_t Idx) {
+  CU.addBaseTypeRef(DIE, Idx);
 }
 
 bool DIEDwarfExpression::isFrameRegister(const TargetRegisterInfo &TRI,
Index: lib/DebugInfo/DWARF/DWARFExpression.cpp
===================================================================
--- lib/DebugInfo/DWARF/DWARFExpression.cpp
+++ lib/DebugInfo/DWARF/DWARFExpression.cpp
@@ -96,6 +96,7 @@
   Descriptions[DW_OP_addrx] = Desc(Op::Dwarf4, Op::SizeLEB);
   Descriptions[DW_OP_GNU_addr_index] = Desc(Op::Dwarf4, Op::SizeLEB);
   Descriptions[DW_OP_GNU_const_index] = Desc(Op::Dwarf4, Op::SizeLEB);
+  Descriptions[DW_OP_convert] = Desc(Op::Dwarf4, Op::SizeLEB);
   return Descriptions;
 }
 
Index: lib/IR/AsmWriter.cpp
===================================================================
--- lib/IR/AsmWriter.cpp
+++ lib/IR/AsmWriter.cpp
@@ -2123,8 +2123,13 @@
       assert(!OpStr.empty() && "Expected valid opcode");
 
       Out << FS << OpStr;
-      for (unsigned A = 0, AE = I->getNumArgs(); A != AE; ++A)
-        Out << FS << I->getArg(A);
+      if (I->getOp() == dwarf::DW_OP_LLVM_convert) {
+        Out << FS << I->getArg(0);
+        Out << FS << dwarf::AttributeEncodingString(I->getArg(1));
+      } else {
+        for (unsigned A = 0, AE = I->getNumArgs(); A != AE; ++A)
+          Out << FS << I->getArg(A);
+      }
     }
   } else {
     for (const auto &I : N->getElements())
Index: lib/IR/DebugInfoMetadata.cpp
===================================================================
--- lib/IR/DebugInfoMetadata.cpp
+++ lib/IR/DebugInfoMetadata.cpp
@@ -813,6 +813,7 @@
 
 unsigned DIExpression::ExprOperand::getSize() const {
   switch (getOp()) {
+  case dwarf::DW_OP_LLVM_convert:
   case dwarf::DW_OP_LLVM_fragment:
     return 3;
   case dwarf::DW_OP_constu:
@@ -857,6 +858,7 @@
         return false;
       break;
     }
+    case dwarf::DW_OP_LLVM_convert:
     case dwarf::DW_OP_constu:
     case dwarf::DW_OP_plus_uconst:
     case dwarf::DW_OP_plus:
Index: lib/MC/MCStreamer.cpp
===================================================================
--- lib/MC/MCStreamer.cpp
+++ lib/MC/MCStreamer.cpp
@@ -135,10 +135,10 @@
 
 /// EmitULEB128IntValue - Special case of EmitULEB128Value that avoids the
 /// client having to pass in a MCExpr for constant integers.
-void MCStreamer::EmitULEB128IntValue(uint64_t Value) {
+void MCStreamer::EmitULEB128IntValue(uint64_t Value, unsigned PadTo) {
   SmallString<128> Tmp;
   raw_svector_ostream OSE(Tmp);
-  encodeULEB128(Value, OSE);
+  encodeULEB128(Value, OSE, PadTo);
   EmitBytes(OSE.str());
 }
 
Index: lib/Transforms/Utils/Local.cpp
===================================================================
--- lib/Transforms/Utils/Local.cpp
+++ lib/Transforms/Utils/Local.cpp
@@ -1860,21 +1860,10 @@
         return None;
 
       bool Signed = *Signedness == DIBasicType::Signedness::Signed;
-
-      if (!Signed) {
-        // In the unsigned case, assume that a debugger will initialize the
-        // high bits to 0 and do a no-op conversion.
-        return Identity(DII);
-      } else {
-        // In the signed case, the high bits are given by sign extension, i.e:
-        //   (To >> (ToBits - 1)) * ((2 ^ FromBits) - 1)
-        // Calculate the high bits and OR them together with the low bits.
-        SmallVector<uint64_t, 8> Ops({dwarf::DW_OP_dup, dwarf::DW_OP_constu,
-                                      (ToBits - 1), dwarf::DW_OP_shr,
-                                      dwarf::DW_OP_lit0, dwarf::DW_OP_not,
-                                      dwarf::DW_OP_mul, dwarf::DW_OP_or});
-        return DIExpression::appendToStack(DII.getExpression(), Ops);
-      }
+      dwarf::TypeKind TK = Signed ? dwarf::DW_ATE_signed : dwarf::DW_ATE_unsigned;
+      SmallVector<uint64_t, 8> Ops({dwarf::DW_OP_LLVM_convert, ToBits, TK,
+                                   dwarf::DW_OP_LLVM_convert, FromBits, TK});
+      return DIExpression::appendToStack(DII.getExpression(), Ops);
     };
     return rewriteDebugUsers(From, To, DomPoint, DT, SignOrZeroExt);
   }
Index: test/Assembler/diexpression.ll
===================================================================
--- test/Assembler/diexpression.ll
+++ test/Assembler/diexpression.ll
@@ -8,9 +8,10 @@
 ; CHECK-SAME: !DIExpression(DW_OP_LLVM_fragment, 3, 7),
 ; CHECK-SAME: !DIExpression(DW_OP_deref, DW_OP_plus_uconst, 3, DW_OP_LLVM_fragment, 3, 7),
 ; CHECK-SAME: !DIExpression(DW_OP_constu, 2, DW_OP_swap, DW_OP_xderef),
-; CHECK-SAME: !DIExpression(DW_OP_plus_uconst, 3)}
+; CHECK-SAME: !DIExpression(DW_OP_plus_uconst, 3)
+; CHECK-SAME: !DIExpression(DW_OP_LLVM_convert, 16, DW_ATE_unsigned, DW_OP_LLVM_convert, 32, DW_ATE_signed)}
 
-!named = !{!0, !1, !2, !3, !4, !5, !6}
+!named = !{!0, !1, !2, !3, !4, !5, !6, !7}
 
 !0 = !DIExpression()
 !1 = !DIExpression(DW_OP_deref)
@@ -19,3 +20,4 @@
 !4 = !DIExpression(DW_OP_deref, DW_OP_plus_uconst, 3, DW_OP_LLVM_fragment, 3, 7)
 !5 = !DIExpression(DW_OP_constu, 2, DW_OP_swap, DW_OP_xderef)
 !6 = !DIExpression(DW_OP_plus_uconst, 3)
+!7 = !DIExpression(DW_OP_LLVM_convert, 16, DW_ATE_unsigned, DW_OP_LLVM_convert, 32, DW_ATE_signed)
Index: test/DebugInfo/Generic/convert-debugloc.ll
===================================================================
--- /dev/null
+++ test/DebugInfo/Generic/convert-debugloc.ll
@@ -0,0 +1,167 @@
+; RUN: llc -filetype=obj -O0 < %s | llvm-dwarfdump - | FileCheck %s --check-prefix=DW5-CHECK
+; RUN: llc -dwarf-version=4 -filetype=obj -O0 < %s | llvm-dwarfdump - | FileCheck %s --check-prefix=DW4-CHECK
+
+; DW5-CHECK: .debug_info contents:
+; DW5-CHECK-NEXT: 0x00000000: Compile Unit: length = 0x0000005c version = 0x0005 unit_type = DW_UT_compile abbr_offset = 0x0000 addr_size = 0x08 (next unit at 0x00000060)
+; DW5-CHECK-EMPTY:
+; DW5-CHECK-NEXT: 0x0000000c: DW_TAG_compile_unit
+; DW5-CHECK-NEXT:               DW_AT_producer	("clang version 9.0.0 (trunk 353791) (llvm/trunk 353801)")
+; DW5-CHECK-NEXT:               DW_AT_language	(DW_LANG_C99)
+; DW5-CHECK-NEXT:               DW_AT_name	("dbg.c")
+; DW5-CHECK-NEXT:               DW_AT_str_offsets_base	(0x00000008)
+; DW5-CHECK-NEXT:               DW_AT_stmt_list	(0x00000000)
+; DW5-CHECK-NEXT:               DW_AT_comp_dir	("/tmp")
+; DW5-CHECK-NEXT:               DW_AT_addr_base	(0x00000008)
+; DW5-CHECK-NEXT:               DW_AT_low_pc	(0x0000000000000000)
+; DW5-CHECK-NEXT:               DW_AT_high_pc	(0x000000000000000c)
+; DW5-CHECK-NEXT:               DW_AT_loclists_base	(0x0000000c)
+; DW5-CHECK-EMPTY:
+; DW5-CHECK-NEXT: 0x00000027:   DW_TAG_base_type
+; DW5-CHECK-NEXT:                 DW_AT_name	("DW_ATE_signed_8")
+; DW5-CHECK-NEXT:                 DW_AT_encoding	(DW_ATE_signed)
+; DW5-CHECK-NEXT:                 DW_AT_byte_size	(0x01)
+; DW5-CHECK-EMPTY:
+; DW5-CHECK-NEXT: 0x0000002b:   DW_TAG_base_type
+; DW5-CHECK-NEXT:                 DW_AT_name	("DW_ATE_signed_32")
+; DW5-CHECK-NEXT:                 DW_AT_encoding	(DW_ATE_signed)
+; DW5-CHECK-NEXT:                 DW_AT_byte_size	(0x04)
+; DW5-CHECK-EMPTY:
+; DW5-CHECK-NEXT: 0x0000002f:   DW_TAG_subprogram
+; DW5-CHECK-NEXT:                 DW_AT_low_pc	(0x0000000000000000)
+; DW5-CHECK-NEXT:                 DW_AT_high_pc	(0x000000000000000c)
+; DW5-CHECK-NEXT:                 DW_AT_frame_base	(DW_OP_reg6 RBP)
+; DW5-CHECK-NEXT:                 DW_AT_name	("foo")
+; DW5-CHECK-NEXT:                 DW_AT_decl_file	("/tmp/dbg.c")
+; DW5-CHECK-NEXT:                 DW_AT_decl_line	(1)
+; DW5-CHECK-NEXT:                 DW_AT_prototyped	(true)
+; DW5-CHECK-NEXT:                 DW_AT_type	(0x00000057 "signed char")
+; DW5-CHECK-NEXT:                 DW_AT_external	(true)
+; DW5-CHECK-EMPTY:
+; DW5-CHECK-NEXT: 0x0000003e:     DW_TAG_formal_parameter
+; DW5-CHECK-NEXT:                   DW_AT_location	(0x0000000c
+; DW5-CHECK-NEXT:                      [0x0000000000000007, 0x000000000000000a): DW_OP_reg0 RAX)
+; DW5-CHECK-NEXT:                   DW_AT_name	("x")
+; DW5-CHECK-NEXT:                   DW_AT_decl_file	("/tmp/dbg.c")
+; DW5-CHECK-NEXT:                   DW_AT_decl_line	(1)
+; DW5-CHECK-NEXT:                   DW_AT_type	(0x00000057 "signed char")
+; DW5-CHECK-EMPTY:
+; DW5-CHECK-NEXT: 0x0000004a:     DW_TAG_variable
+; DW5-CHECK-NEXT:                   DW_AT_location	(0x00000012
+; DW5-CHECK-NEXT:                      [0x0000000000000007, 0x000000000000000a): DW_OP_breg0 RAX+0, DW_OP_constu 0xff, DW_OP_and, DW_OP_convert 0x27, DW_OP_convert 0x2b, DW_OP_stack_value)
+; DW5-CHECK-NEXT:                   DW_AT_name	("y")
+; DW5-CHECK-NEXT:                   DW_AT_decl_file	("/tmp/dbg.c")
+; DW5-CHECK-NEXT:                   DW_AT_decl_line	(3)
+; DW5-CHECK-NEXT:                   DW_AT_type	(0x0000005b "int")
+; DW5-CHECK-EMPTY:
+; DW5-CHECK-NEXT: 0x00000056:     NULL
+; DW5-CHECK-EMPTY:
+; DW5-CHECK-NEXT: 0x00000057:   DW_TAG_base_type
+; DW5-CHECK-NEXT:                 DW_AT_name	("signed char")
+; DW5-CHECK-NEXT:                 DW_AT_encoding	(DW_ATE_signed_char)
+; DW5-CHECK-NEXT:                 DW_AT_byte_size	(0x01)
+; DW5-CHECK-EMPTY:
+; DW5-CHECK-NEXT: 0x0000005b:   DW_TAG_base_type
+; DW5-CHECK-NEXT:                 DW_AT_name	("int")
+; DW5-CHECK-NEXT:                 DW_AT_encoding	(DW_ATE_signed)
+; DW5-CHECK-NEXT:                 DW_AT_byte_size	(0x04)
+; DW5-CHECK-EMPTY:
+; DW5-CHECK-NEXT: 0x0000005f:   NULL
+
+
+; DW4-CHECK: .debug_info contents:
+; DW4-CHECK-NEXT: 0x00000000: Compile Unit: length = 0x0000006d version = 0x0004 abbr_offset = 0x0000 addr_size = 0x08 (next unit at 0x00000071)
+; DW4-CHECK-EMPTY:
+; DW4-CHECK-NEXT: 0x0000000b: DW_TAG_compile_unit
+; DW4-CHECK-NEXT:               DW_AT_producer	("clang version 9.0.0 (trunk 353791) (llvm/trunk 353801)")
+; DW4-CHECK-NEXT:               DW_AT_language	(DW_LANG_C99)
+; DW4-CHECK-NEXT:               DW_AT_name	("dbg.c")
+; DW4-CHECK-NEXT:               DW_AT_stmt_list	(0x00000000)
+; DW4-CHECK-NEXT:               DW_AT_comp_dir	("/tmp")
+; DW4-CHECK-NEXT:               DW_AT_low_pc	(0x0000000000000000)
+; DW4-CHECK-NEXT:               DW_AT_high_pc	(0x000000000000000c)
+; DW4-CHECK-EMPTY:
+; DW4-CHECK-NEXT: 0x0000002a:   DW_TAG_subprogram
+; DW4-CHECK-NEXT:                 DW_AT_low_pc	(0x0000000000000000)
+; DW4-CHECK-NEXT:                 DW_AT_high_pc	(0x000000000000000c)
+; DW4-CHECK-NEXT:                 DW_AT_frame_base	(DW_OP_reg6 RBP)
+; DW4-CHECK-NEXT:                 DW_AT_name	("foo")
+; DW4-CHECK-NEXT:                 DW_AT_decl_file	("/tmp/dbg.c")
+; DW4-CHECK-NEXT:                 DW_AT_decl_line	(1)
+; DW4-CHECK-NEXT:                 DW_AT_prototyped	(true)
+; DW4-CHECK-NEXT:                 DW_AT_type	(0x00000062 "signed char")
+; DW4-CHECK-NEXT:                 DW_AT_external	(true)
+; DW4-CHECK-EMPTY:
+; DW4-CHECK-NEXT: 0x00000043:     DW_TAG_formal_parameter
+; DW4-CHECK-NEXT:                   DW_AT_location	(0x00000000
+; DW4-CHECK-NEXT:                      [0x0000000000000007,  0x000000000000000a): DW_OP_reg0 RAX)
+; DW4-CHECK-NEXT:                   DW_AT_name	("x")
+; DW4-CHECK-NEXT:                   DW_AT_decl_file	("/tmp/dbg.c")
+; DW4-CHECK-NEXT:                   DW_AT_decl_line	(1)
+; DW4-CHECK-NEXT:                   DW_AT_type	(0x00000062 "signed char")
+; DW4-CHECK-EMPTY:
+; DW4-CHECK-NEXT: 0x00000052:     DW_TAG_variable
+; DW4-CHECK-NEXT:                   DW_AT_location	(0x00000023
+; DW4-CHECK-NEXT:                      [0x0000000000000007,  0x000000000000000a): DW_OP_breg0 RAX+0, DW_OP_constu 0xff, DW_OP_and, DW_OP_dup, DW_OP_constu 0x7, DW_OP_shr, DW_OP_lit0, DW_OP_not, DW_OP_mul, DW_OP_constu 0x8, DW_OP_shl, DW_OP_or, DW_OP_stack_value)
+; DW4-CHECK-NEXT:                   DW_AT_name	("y")
+; DW4-CHECK-NEXT:                   DW_AT_decl_file	("/tmp/dbg.c")
+; DW4-CHECK-NEXT:                   DW_AT_decl_line	(3)
+; DW4-CHECK-NEXT:                   DW_AT_type	(0x00000069 "int")
+; DW4-CHECK-EMPTY:
+; DW4-CHECK-NEXT: 0x00000061:     NULL
+; DW4-CHECK-EMPTY:
+; DW4-CHECK-NEXT: 0x00000062:   DW_TAG_base_type
+; DW4-CHECK-NEXT:                 DW_AT_name	("signed char")
+; DW4-CHECK-NEXT:                 DW_AT_encoding	(DW_ATE_signed_char)
+; DW4-CHECK-NEXT:                 DW_AT_byte_size	(0x01)
+; DW4-CHECK-EMPTY:
+; DW4-CHECK-NEXT: 0x00000069:   DW_TAG_base_type
+; DW4-CHECK-NEXT:                 DW_AT_name	("int")
+; DW4-CHECK-NEXT:                 DW_AT_encoding	(DW_ATE_signed)
+; DW4-CHECK-NEXT:                 DW_AT_byte_size	(0x04)
+; DW4-CHECK-EMPTY:
+; DW4-CHECK-NEXT: 0x00000070:   NULL
+
+
+; ModuleID = 'dbg.ll'
+source_filename = "dbg.c"
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+; Function Attrs: noinline nounwind uwtable
+define dso_local signext i8 @foo(i8 signext %x) #0 !dbg !7 {
+entry:
+  call void @llvm.dbg.value(metadata i8 %x, metadata !11, metadata !DIExpression()), !dbg !12
+  call void @llvm.dbg.value(metadata i8 %x, metadata !13, metadata !DIExpression(DW_OP_LLVM_convert, 8, DW_ATE_signed, DW_OP_LLVM_convert, 32, DW_ATE_signed, DW_OP_stack_value)), !dbg !15
+  ret i8 %x, !dbg !16
+}
+
+; Function Attrs: nounwind readnone speculatable
+declare void @llvm.dbg.declare(metadata, metadata, metadata) #1
+
+; Function Attrs: nounwind readnone speculatable
+declare void @llvm.dbg.value(metadata, metadata, metadata) #1
+
+attributes #0 = { noinline nounwind uwtable "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "min-legal-vector-width"="0" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #1 = { nounwind readnone speculatable }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4, !5}
+!llvm.ident = !{!6}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 9.0.0 (trunk 353791) (llvm/trunk 353801)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, nameTableKind: None)
+!1 = !DIFile(filename: "dbg.c", directory: "/tmp", checksumkind: CSK_MD5, checksum: "2a034da6937f5b9cf6dd2d89127f57fd")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 5}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{i32 1, !"wchar_size", i32 4}
+!6 = !{!"clang version 9.0.0 (trunk 353791) (llvm/trunk 353801)"}
+!7 = distinct !DISubprogram(name: "foo", scope: !1, file: !1, line: 1, type: !8, scopeLine: 2, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !2)
+!8 = !DISubroutineType(types: !9)
+!9 = !{!10, !10}
+!10 = !DIBasicType(name: "signed char", size: 8, encoding: DW_ATE_signed_char)
+!11 = !DILocalVariable(name: "x", arg: 1, scope: !7, file: !1, line: 1, type: !10)
+!12 = !DILocation(line: 1, column: 29, scope: !7)
+!13 = !DILocalVariable(name: "y", scope: !7, file: !1, line: 3, type: !14)
+!14 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!15 = !DILocation(line: 3, column: 14, scope: !7)
+!16 = !DILocation(line: 4, column: 3, scope: !7)
Index: test/DebugInfo/Generic/convert-inlined.ll
===================================================================
--- /dev/null
+++ test/DebugInfo/Generic/convert-inlined.ll
@@ -0,0 +1,87 @@
+; RUN: llc -filetype=obj -O0 < %s | llvm-dwarfdump - | FileCheck %s --check-prefix=DW5-CHECK
+; RUN: llc -dwarf-version=4 -filetype=obj -O0 < %s | llvm-dwarfdump - | FileCheck %s --check-prefix=DW4-CHECK
+
+; DW5-CHECK: .debug_info contents:
+; DW5-CHECK-NEXT: 0x00000000: Compile Unit: length = 0x0000003e version = 0x0005 unit_type = DW_UT_compile abbr_offset = 0x0000 addr_size = 0x08 (next unit at 0x00000042)
+; DW5-CHECK-EMPTY:
+; DW5-CHECK-NEXT: 0x0000000c: DW_TAG_compile_unit
+; DW5-CHECK-NEXT:               DW_AT_producer	("clang version 9.0.0 (trunk 353791) (llvm/trunk 353801)")
+; DW5-CHECK-NEXT:               DW_AT_language	(DW_LANG_C99)
+; DW5-CHECK-NEXT:               DW_AT_name	("dbg.c")
+; DW5-CHECK-NEXT:               DW_AT_str_offsets_base	(0x00000008)
+; DW5-CHECK-NEXT:               DW_AT_stmt_list	(0x00000000)
+; DW5-CHECK-NEXT:               DW_AT_comp_dir	("/tmp")
+; DW5-CHECK-NEXT:               DW_AT_addr_base	(0x00000008)
+; DW5-CHECK-EMPTY:
+; DW5-CHECK-NEXT: 0x0000001e:   DW_TAG_base_type
+; DW5-CHECK-NEXT:                 DW_AT_name	("DW_ATE_signed_8")
+; DW5-CHECK-NEXT:                 DW_AT_encoding	(DW_ATE_signed)
+; DW5-CHECK-NEXT:                 DW_AT_byte_size	(0x01)
+; DW5-CHECK-EMPTY:
+; DW5-CHECK-NEXT: 0x00000022:   DW_TAG_base_type
+; DW5-CHECK-NEXT:                 DW_AT_name	("DW_ATE_signed_32")
+; DW5-CHECK-NEXT:                 DW_AT_encoding	(DW_ATE_signed)
+; DW5-CHECK-NEXT:                 DW_AT_byte_size	(0x04)
+; DW5-CHECK-EMPTY:
+; DW5-CHECK-NEXT: 0x00000026:   DW_TAG_variable
+; DW5-CHECK-NEXT:                 DW_AT_name	("global")
+; DW5-CHECK-NEXT:                 DW_AT_type	(0x0000003d "int")
+; DW5-CHECK-NEXT:                 DW_AT_external	(true)
+; DW5-CHECK-NEXT:                 DW_AT_decl_file	("/tmp/dbg.c")
+; DW5-CHECK-NEXT:                 DW_AT_decl_line	(1)
+; DW5-CHECK-NEXT:                 DW_AT_location	(DW_OP_addrx 0x0, DW_OP_deref, DW_OP_convert 0x1e, DW_OP_convert 0x22, DW_OP_stack_value)
+; DW5-CHECK-EMPTY:
+; DW5-CHECK-NEXT: 0x0000003d:   DW_TAG_base_type
+; DW5-CHECK-NEXT:                 DW_AT_name	("int")
+; DW5-CHECK-NEXT:                 DW_AT_encoding	(DW_ATE_signed)
+; DW5-CHECK-NEXT:                 DW_AT_byte_size	(0x04)
+; DW5-CHECK-EMPTY:
+; DW5-CHECK-NEXT: 0x00000041:   NULL
+
+
+; DW4-CHECK: .debug_info contents:
+; DW4-CHECK-NEXT: 0x00000000: Compile Unit: length = 0x00000044 version = 0x0004 abbr_offset = 0x0000 addr_size = 0x08 (next unit at 0x00000048)
+; DW4-CHECK-EMPTY:
+; DW4-CHECK-NEXT: 0x0000000b: DW_TAG_compile_unit
+; DW4-CHECK-NEXT:               DW_AT_producer	("clang version 9.0.0 (trunk 353791) (llvm/trunk 353801)")
+; DW4-CHECK-NEXT:               DW_AT_language	(DW_LANG_C99)
+; DW4-CHECK-NEXT:               DW_AT_name	("dbg.c")
+; DW4-CHECK-NEXT:               DW_AT_stmt_list	(0x00000000)
+; DW4-CHECK-NEXT:               DW_AT_comp_dir	("/tmp")
+; DW4-CHECK-EMPTY:
+; DW4-CHECK-NEXT: 0x0000001e:   DW_TAG_variable
+; DW4-CHECK-NEXT:                 DW_AT_name	("global")
+; DW4-CHECK-NEXT:                 DW_AT_type	(0x00000040 "int")
+; DW4-CHECK-NEXT:                 DW_AT_external	(true)
+; DW4-CHECK-NEXT:                 DW_AT_decl_file	("/tmp/dbg.c")
+; DW4-CHECK-NEXT:                 DW_AT_decl_line	(1)
+; DW4-CHECK-NEXT:                 DW_AT_location	(DW_OP_addr 0x0, DW_OP_deref, DW_OP_dup, DW_OP_constu 0x7, DW_OP_shr, DW_OP_lit0, DW_OP_not, DW_OP_mul, DW_OP_constu 0x8, DW_OP_shl, DW_OP_or, DW_OP_stack_value)
+; DW4-CHECK-EMPTY:
+; DW4-CHECK-NEXT: 0x00000040:   DW_TAG_base_type
+; DW4-CHECK-NEXT:                 DW_AT_name	("int")
+; DW4-CHECK-NEXT:                 DW_AT_encoding	(DW_ATE_signed)
+; DW4-CHECK-NEXT:                 DW_AT_byte_size	(0x04)
+; DW4-CHECK-EMPTY:
+; DW4-CHECK-NEXT: 0x00000047:   NULL
+
+source_filename = "dbg.c"
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+@global = dso_local global i32 255, align 4, !dbg !0
+
+!llvm.dbg.cu = !{!2}
+!llvm.module.flags = !{!7, !8, !9}
+!llvm.ident = !{!10}
+
+!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression(DW_OP_deref, DW_OP_LLVM_convert, 8, DW_ATE_signed, DW_OP_LLVM_convert, 32, DW_ATE_signed, DW_OP_stack_value))
+!1 = distinct !DIGlobalVariable(name: "global", scope: !2, file: !3, line: 1, type: !6, isLocal: false, isDefinition: true)
+!2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, producer: "clang version 9.0.0 (trunk 353791) (llvm/trunk 353801)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5, nameTableKind: None)
+!3 = !DIFile(filename: "dbg.c", directory: "/tmp", checksumkind: CSK_MD5, checksum: "7c731722dd7304ccb8e366ae80269b82")
+!4 = !{}
+!5 = !{!0}
+!6 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!7 = !{i32 2, !"Dwarf Version", i32 5}
+!8 = !{i32 2, !"Debug Info Version", i32 3}
+!9 = !{i32 1, !"wchar_size", i32 4}
+!10 = !{!"clang version 9.0.0 (trunk 353791) (llvm/trunk 353801)"}
Index: test/Transforms/InstCombine/cast-set-preserve-signed-dbg-val.ll
===================================================================
--- test/Transforms/InstCombine/cast-set-preserve-signed-dbg-val.ll
+++ test/Transforms/InstCombine/cast-set-preserve-signed-dbg-val.ll
@@ -14,7 +14,7 @@
   ;
   ; The high 16 bits of the original 'and' require sign-extending the new 16-bit and:
   ; CHECK-NEXT: call void @llvm.dbg.value(metadata i16 [[and]], metadata [[C:![0-9]+]],
-  ; CHECK-SAME:    metadata !DIExpression(DW_OP_dup, DW_OP_constu, 15, DW_OP_shr, DW_OP_lit0, DW_OP_not, DW_OP_mul, DW_OP_or, DW_OP_stack_value)
+  ; CHECK-SAME:    metadata !DIExpression(DW_OP_LLVM_convert, 16, DW_ATE_signed, DW_OP_LLVM_convert, 32, DW_ATE_signed, DW_OP_stack_value)
 
   %D = trunc i32 %C to i16, !dbg !42
   call void @llvm.dbg.value(metadata i16 %D, metadata !38, metadata !DIExpression()), !dbg !42
Index: unittests/Transforms/Utils/LocalTest.cpp
===================================================================
--- unittests/Transforms/Utils/LocalTest.cpp
+++ unittests/Transforms/Utils/LocalTest.cpp
@@ -788,31 +788,35 @@
   };
 
   // Case 1: The original expr is empty, so no deref is needed.
-  EXPECT_TRUE(hasADbgVal({DW_OP_dup, DW_OP_constu, 31, DW_OP_shr, DW_OP_lit0,
-                          DW_OP_not, DW_OP_mul, DW_OP_or, DW_OP_stack_value}));
+  EXPECT_TRUE(hasADbgVal({DW_OP_LLVM_convert, 32, DW_ATE_signed,
+                         DW_OP_LLVM_convert, 64, DW_ATE_signed,
+                         DW_OP_stack_value}));
 
   // Case 2: Perform an address calculation with the original expr, deref it,
   // then sign-extend the result.
-  EXPECT_TRUE(hasADbgVal({DW_OP_lit0, DW_OP_mul, DW_OP_deref, DW_OP_dup,
-                          DW_OP_constu, 31, DW_OP_shr, DW_OP_lit0, DW_OP_not,
-                          DW_OP_mul, DW_OP_or, DW_OP_stack_value}));
+  EXPECT_TRUE(hasADbgVal({DW_OP_lit0, DW_OP_mul, DW_OP_deref,
+                         DW_OP_LLVM_convert, 32, DW_ATE_signed,
+                         DW_OP_LLVM_convert, 64, DW_ATE_signed,
+                         DW_OP_stack_value}));
 
   // Case 3: Insert the sign-extension logic before the DW_OP_stack_value.
-  EXPECT_TRUE(hasADbgVal({DW_OP_lit0, DW_OP_mul, DW_OP_dup, DW_OP_constu, 31,
-                          DW_OP_shr, DW_OP_lit0, DW_OP_not, DW_OP_mul, DW_OP_or,
-                          DW_OP_stack_value}));
+  EXPECT_TRUE(hasADbgVal({DW_OP_lit0, DW_OP_mul, DW_OP_LLVM_convert, 32,
+                         DW_ATE_signed, DW_OP_LLVM_convert, 64, DW_ATE_signed,
+                         DW_OP_stack_value}));
 
   // Cases 4-6: Just like cases 1-3, but preserve the fragment at the end.
-  EXPECT_TRUE(hasADbgVal({DW_OP_dup, DW_OP_constu, 31, DW_OP_shr, DW_OP_lit0,
-                          DW_OP_not, DW_OP_mul, DW_OP_or, DW_OP_stack_value,
-                          DW_OP_LLVM_fragment, 0, 8}));
-  EXPECT_TRUE(
-      hasADbgVal({DW_OP_lit0, DW_OP_mul, DW_OP_deref, DW_OP_dup, DW_OP_constu,
-                  31, DW_OP_shr, DW_OP_lit0, DW_OP_not, DW_OP_mul, DW_OP_or,
-                  DW_OP_stack_value, DW_OP_LLVM_fragment, 0, 8}));
-  EXPECT_TRUE(hasADbgVal({DW_OP_lit0, DW_OP_mul, DW_OP_dup, DW_OP_constu, 31,
-                          DW_OP_shr, DW_OP_lit0, DW_OP_not, DW_OP_mul, DW_OP_or,
-                          DW_OP_stack_value, DW_OP_LLVM_fragment, 0, 8}));
+  EXPECT_TRUE(hasADbgVal({DW_OP_LLVM_convert, 32, DW_ATE_signed,
+                         DW_OP_LLVM_convert, 64, DW_ATE_signed,
+                         DW_OP_stack_value, DW_OP_LLVM_fragment, 0, 8}));
+
+  EXPECT_TRUE(hasADbgVal({DW_OP_lit0, DW_OP_mul, DW_OP_deref,
+                         DW_OP_LLVM_convert, 32, DW_ATE_signed,
+                         DW_OP_LLVM_convert, 64, DW_ATE_signed,
+                         DW_OP_stack_value, DW_OP_LLVM_fragment, 0, 8}));
+
+  EXPECT_TRUE(hasADbgVal({DW_OP_lit0, DW_OP_mul, DW_OP_LLVM_convert, 32,
+                         DW_ATE_signed, DW_OP_LLVM_convert, 64, DW_ATE_signed,
+                         DW_OP_stack_value, DW_OP_LLVM_fragment, 0, 8}));
 
   verifyModule(*M, &errs(), &BrokenDebugInfo);
   ASSERT_FALSE(BrokenDebugInfo);