Index: llvm/trunk/include/llvm/BinaryFormat/Dwarf.h
===================================================================
--- llvm/trunk/include/llvm/BinaryFormat/Dwarf.h
+++ llvm/trunk/include/llvm/BinaryFormat/Dwarf.h
@@ -46,6 +46,11 @@
   DW_VIRTUALITY_invalid = ~0U, // Virtuality for invalid results.
   DW_MACINFO_invalid = ~0U,    // Macinfo type for invalid results.
 
+  // Special values for an initial length field.
+  DW_LENGTH_lo_reserved = 0xfffffff0, // Lower bound of the reserved range.
+  DW_LENGTH_DWARF64 = 0xffffffff,     // Indicator of 64-bit DWARF format.
+  DW_LENGTH_hi_reserved = 0xffffffff, // Upper bound of the reserved range.
+
   // Other constants.
   DWARF_VERSION = 4,       // Default dwarf version we output.
   DW_PUBTYPES_VERSION = 2, // Section version number for .debug_pubtypes.
Index: llvm/trunk/lib/DebugInfo/DWARF/DWARFDebugAddr.cpp
===================================================================
--- llvm/trunk/lib/DebugInfo/DWARF/DWARFDebugAddr.cpp
+++ llvm/trunk/lib/DebugInfo/DWARF/DWARFDebugAddr.cpp
@@ -44,7 +44,7 @@
   Format = dwarf::DwarfFormat::DWARF32;
   if (UnitVersion >= 5) {
     HeaderData.Length = Data.getU32(OffsetPtr);
-    if (HeaderData.Length == 0xffffffffu) {
+    if (HeaderData.Length == dwarf::DW_LENGTH_DWARF64) {
       invalidateLength();
       return createStringError(errc::not_supported,
           "DWARF64 is not supported in .debug_addr at offset 0x%" PRIx32,
Index: llvm/trunk/lib/DebugInfo/DWARF/DWARFDebugFrame.cpp
===================================================================
--- llvm/trunk/lib/DebugInfo/DWARF/DWARFDebugFrame.cpp
+++ llvm/trunk/lib/DebugInfo/DWARF/DWARFDebugFrame.cpp
@@ -364,7 +364,7 @@
     uint64_t Length = Data.getRelocatedValue(4, &Offset);
     uint64_t Id;
 
-    if (Length == UINT32_MAX) {
+    if (Length == dwarf::DW_LENGTH_DWARF64) {
       // DWARF-64 is distinguished by the first 32 bits of the initial length
       // field being 0xffffffff. Then, the next 64 bits are the actual entry
       // length.
Index: llvm/trunk/lib/DebugInfo/DWARF/DWARFDebugLine.cpp
===================================================================
--- llvm/trunk/lib/DebugInfo/DWARF/DWARFDebugLine.cpp
+++ llvm/trunk/lib/DebugInfo/DWARF/DWARFDebugLine.cpp
@@ -332,10 +332,10 @@
 
   clear();
   TotalLength = DebugLineData.getRelocatedValue(4, OffsetPtr);
-  if (TotalLength == UINT32_MAX) {
+  if (TotalLength == dwarf::DW_LENGTH_DWARF64) {
     FormParams.Format = dwarf::DWARF64;
     TotalLength = DebugLineData.getU64(OffsetPtr);
-  } else if (TotalLength >= 0xfffffff0) {
+  } else if (TotalLength >= dwarf::DW_LENGTH_lo_reserved) {
     return createStringError(errc::invalid_argument,
         "parsing line table prologue at offset 0x%8.8" PRIx64
         " unsupported reserved unit length found of value 0x%8.8" PRIx64,
@@ -1126,7 +1126,8 @@
 }
 
 bool DWARFDebugLine::Prologue::totalLengthIsValid() const {
-  return TotalLength == 0xffffffff || TotalLength < 0xfffffff0;
+  return TotalLength == dwarf::DW_LENGTH_DWARF64 ||
+         TotalLength < dwarf::DW_LENGTH_lo_reserved;
 }
 
 DWARFDebugLine::LineTable DWARFDebugLine::SectionParser::parseNext(
Index: llvm/trunk/lib/DebugInfo/DWARF/DWARFListTable.cpp
===================================================================
--- llvm/trunk/lib/DebugInfo/DWARF/DWARFListTable.cpp
+++ llvm/trunk/lib/DebugInfo/DWARF/DWARFListTable.cpp
@@ -26,7 +26,7 @@
                        SectionName.data(), *OffsetPtr);
   // TODO: Add support for DWARF64.
   HeaderData.Length = Data.getRelocatedValue(4, OffsetPtr);
-  if (HeaderData.Length == 0xffffffffu)
+  if (HeaderData.Length == dwarf::DW_LENGTH_DWARF64)
     return createStringError(errc::not_supported,
                        "DWARF64 is not supported in %s at offset 0x%" PRIx32,
                        SectionName.data(), HeaderOffset);
Index: llvm/trunk/lib/DebugInfo/DWARF/DWARFUnit.cpp
===================================================================
--- llvm/trunk/lib/DebugInfo/DWARF/DWARFUnit.cpp
+++ llvm/trunk/lib/DebugInfo/DWARF/DWARFUnit.cpp
@@ -244,7 +244,7 @@
   Length = debug_info.getRelocatedValue(4, offset_ptr);
   FormParams.Format = DWARF32;
   unsigned SizeOfLength = 4;
-  if (Length == 0xffffffff) {
+  if (Length == dwarf::DW_LENGTH_DWARF64) {
     Length = debug_info.getU64(offset_ptr);
     FormParams.Format = DWARF64;
     SizeOfLength = 8;
@@ -784,7 +784,7 @@
   if (!DA.isValidOffsetForDataOfSize(Offset, 16))
     return createStringError(errc::invalid_argument, "section offset exceeds section size");
 
-  if (DA.getU32(&Offset) != 0xffffffff)
+  if (DA.getU32(&Offset) != dwarf::DW_LENGTH_DWARF64)
     return createStringError(errc::invalid_argument, "32 bit contribution referenced from a 64 bit unit");
 
   uint64_t Size = DA.getU64(&Offset);
@@ -803,7 +803,7 @@
     return createStringError(errc::invalid_argument, "section offset exceeds section size");
 
   uint32_t ContributionSize = DA.getU32(&Offset);
-  if (ContributionSize >= 0xfffffff0)
+  if (ContributionSize >= dwarf::DW_LENGTH_lo_reserved)
     return createStringError(errc::invalid_argument, "invalid length");
 
   uint8_t Version = DA.getU16(&Offset);
Index: llvm/trunk/lib/DebugInfo/DWARF/DWARFVerifier.cpp
===================================================================
--- llvm/trunk/lib/DebugInfo/DWARF/DWARFVerifier.cpp
+++ llvm/trunk/lib/DebugInfo/DWARF/DWARFVerifier.cpp
@@ -113,7 +113,7 @@
 
   uint32_t OffsetStart = *Offset;
   Length = DebugInfoData.getU32(Offset);
-  if (Length == UINT32_MAX) {
+  if (Length == dwarf::DW_LENGTH_DWARF64) {
     Length = DebugInfoData.getU64(Offset);
     isUnitDWARF64 = true;
   }
Index: llvm/trunk/unittests/DebugInfo/DWARF/DwarfGenerator.cpp
===================================================================
--- llvm/trunk/unittests/DebugInfo/DWARF/DwarfGenerator.cpp
+++ llvm/trunk/unittests/DebugInfo/DWARF/DwarfGenerator.cpp
@@ -262,7 +262,7 @@
   MCSymbol *UnitStart = Asm.createTempSymbol("line_unit_start");
   MCSymbol *UnitEnd = Asm.createTempSymbol("line_unit_end");
   if (Format == DwarfFormat::DWARF64) {
-    Asm.emitInt32(0xffffffff);
+    Asm.emitInt32(dwarf::DW_LENGTH_DWARF64);
     Asm.EmitLabelDifference(UnitEnd, UnitStart, 8);
   } else {
     Asm.EmitLabelDifference(UnitEnd, UnitStart, 4);
@@ -288,7 +288,7 @@
 
 void dwarfgen::LineTable::writePrologue(AsmPrinter &Asm) const {
   if (Format == DwarfFormat::DWARF64) {
-    Asm.emitInt32(0xffffffff);
+    Asm.emitInt32(dwarf::DW_LENGTH_DWARF64);
     Asm.emitInt64(Prologue->TotalLength);
   } else {
     Asm.emitInt32(Prologue->TotalLength);