Index: llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
===================================================================
--- llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -2850,23 +2850,23 @@
 
     // Emit size of content not including length itself.
     unsigned ContentSize =
-        sizeof(int16_t) + // DWARF ARange version number
-        sizeof(int32_t) + // Offset of CU in the .debug_info section
-        sizeof(int8_t) +  // Pointer Size (in bytes)
-        sizeof(int8_t);   // Segment Size (in bytes)
+        sizeof(int16_t) +               // DWARF ARange version number
+        Asm->getDwarfOffsetByteSize() + // Offset of CU in the .debug_info
+                                        // section
+        sizeof(int8_t) +                // Pointer Size (in bytes)
+        sizeof(int8_t);                 // Segment Size (in bytes)
 
     unsigned TupleSize = PtrSize * 2;
 
     // 7.20 in the Dwarf specs requires the table to be aligned to a tuple.
-    unsigned Padding =
-        offsetToAlignment(sizeof(int32_t) + ContentSize, Align(TupleSize));
+    unsigned Padding = offsetToAlignment(
+        Asm->getUnitLengthFieldByteSize() + ContentSize, Align(TupleSize));
 
     ContentSize += Padding;
     ContentSize += (List.size() + 1) * TupleSize;
 
     // For each compile unit, write the list of spans it covers.
-    Asm->OutStreamer->AddComment("Length of ARange Set");
-    Asm->emitInt32(ContentSize);
+    Asm->emitDwarfUnitLength(ContentSize, "Length of ARange Set");
     Asm->OutStreamer->AddComment("DWARF Arange version number");
     Asm->emitInt16(dwarf::DW_ARANGES_VERSION);
     Asm->OutStreamer->AddComment("Offset Into Debug Info Section");
Index: llvm/test/DebugInfo/X86/debug-aranges-dwarf64.ll
===================================================================
--- /dev/null
+++ llvm/test/DebugInfo/X86/debug-aranges-dwarf64.ll
@@ -0,0 +1,28 @@
+; This checks that .debug_aranges can be generated in the DWARF64 format.
+
+; RUN: llc -mtriple=x86_64 -dwarf64 -generate-arange-section -filetype=obj %s -o %t
+; RUN: llvm-dwarfdump -debug-aranges %t | FileCheck %s
+
+; CHECK:      .debug_aranges contents:
+; CHECK-NEXT: Address Range Header:
+; CHECK-SAME:   length = 0x0000000000000034,
+; CHECK-SAME:   format = DWARF64,
+; CHECK-SAME:   version = 0x0002,
+; CHECK-SAME:   cu_offset = 0x0000000000000000,
+; CHECK-SAME:   addr_size = 0x08,
+; CHECK-SAME:   seg_size = 0x00
+; CHECK-NEXT: [0x0000000000000000,  0x0000000000000004)
+
+@foo = common dso_local global i32 0, align 4, !dbg !5
+
+!llvm.dbg.cu = !{!2}
+!llvm.module.flags = !{!0}
+
+!0 = !{i32 2, !"Debug Info Version", i32 3}
+!1 = !DIFile(filename: "foo.c", directory: "/tmp")
+!2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "Manual", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !3, globals: !4, splitDebugInlining: false, nameTableKind: None)
+!3 = !{}
+!4 = !{!5}
+!5 = !DIGlobalVariableExpression(var: !6, expr: !DIExpression())
+!6 = distinct !DIGlobalVariable(name: "foo", scope: !2, file: !1, line: 1, type: !7, isLocal: false, isDefinition: true)
+!7 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)