Index: lib/DebugInfo/CodeView/SymbolDumper.cpp
===================================================================
--- lib/DebugInfo/CodeView/SymbolDumper.cpp
+++ lib/DebugInfo/CodeView/SymbolDumper.cpp
@@ -317,7 +317,8 @@
 
 Error CVSymbolDumperImpl::visitKnownRecord(
     CVSymbol &CVR, DefRangeRegisterRelSym &DefRangeRegisterRel) {
-  W.printNumber("BaseRegister", DefRangeRegisterRel.Hdr.Register);
+  W.printEnum("BaseRegister", uint16_t(DefRangeRegisterRel.Hdr.Register),
+              getRegisterNames());
   W.printBoolean("HasSpilledUDTMember",
                  DefRangeRegisterRel.hasSpilledUDTMember());
   W.printNumber("OffsetInParent", DefRangeRegisterRel.offsetInParent());
@@ -330,7 +331,8 @@
 
 Error CVSymbolDumperImpl::visitKnownRecord(
     CVSymbol &CVR, DefRangeRegisterSym &DefRangeRegister) {
-  W.printNumber("Register", DefRangeRegister.Hdr.Register);
+  W.printEnum("Register", uint16_t(DefRangeRegister.Hdr.Register),
+              getRegisterNames());
   W.printNumber("MayHaveNoName", DefRangeRegister.Hdr.MayHaveNoName);
   printLocalVariableAddrRange(DefRangeRegister.Range,
                               DefRangeRegister.getRelocationOffset());
@@ -340,7 +342,8 @@
 
 Error CVSymbolDumperImpl::visitKnownRecord(
     CVSymbol &CVR, DefRangeSubfieldRegisterSym &DefRangeSubfieldRegister) {
-  W.printNumber("Register", DefRangeSubfieldRegister.Hdr.Register);
+  W.printEnum("Register", uint16_t(DefRangeSubfieldRegister.Hdr.Register),
+              getRegisterNames());
   W.printNumber("MayHaveNoName", DefRangeSubfieldRegister.Hdr.MayHaveNoName);
   W.printNumber("OffsetInParent", DefRangeSubfieldRegister.Hdr.OffsetInParent);
   printLocalVariableAddrRange(DefRangeSubfieldRegister.Range,
@@ -393,7 +396,7 @@
                                      FrameCookie.getRelocationOffset(),
                                      FrameCookie.CodeOffset, &LinkageName);
   }
-  W.printHex("Register", FrameCookie.Register);
+  W.printEnum("Register", uint16_t(FrameCookie.Register), getRegisterNames());
   W.printEnum("CookieKind", uint16_t(FrameCookie.CookieKind),
               getFrameCookieKindNames());
   W.printHex("Flags", FrameCookie.Flags);
Index: test/DebugInfo/COFF/fp-stack.ll
===================================================================
--- test/DebugInfo/COFF/fp-stack.ll
+++ test/DebugInfo/COFF/fp-stack.ll
@@ -12,7 +12,7 @@
 
 ; ASM:         .cv_def_range    Lfunc_begin0 Lfunc_end0, "A\021\200\000\000\000"
 ; OBJ:    DefRangeRegisterSym {
-; OBJ:      Register: 128
+; OBJ:      Register: 0x80
 ; OBJ:      MayHaveNoName: 0
 ; OBJ:      LocalVariableAddrRange {
 ; OBJ:        OffsetStart: .text+0x0
Index: test/DebugInfo/COFF/local-variable-gap.ll
===================================================================
--- test/DebugInfo/COFF/local-variable-gap.ll
+++ test/DebugInfo/COFF/local-variable-gap.ll
@@ -73,7 +73,7 @@
 ; OBJ-NOT:     LocalSym {
 ; OBJ:         DefRangeRegisterSym {
 ; OBJ-NEXT:      Kind:
-; OBJ-NEXT:      Register: 23
+; OBJ-NEXT:      Register: ESI (0x17)
 ; OBJ-NEXT:      MayHaveNoName: 0
 ; OBJ-NEXT:      LocalVariableAddrRange {
 ; OBJ-NEXT:        OffsetStart: .text+0x{{.*}}
Index: test/DebugInfo/COFF/local-variables.ll
===================================================================
--- test/DebugInfo/COFF/local-variables.ll
+++ test/DebugInfo/COFF/local-variables.ll
@@ -111,7 +111,7 @@
 ; OBJ:      VarName: param
 ; OBJ:    }
 ; OBJ:    DefRangeRegisterRelSym {
-; OBJ:      BaseRegister: 335
+; OBJ:      BaseRegister: RSP (0x14F)
 ; OBJ:      HasSpilledUDTMember: No
 ; OBJ:      OffsetInParent: 0
 ; OBJ:      BasePointerOffset: 52
@@ -128,7 +128,7 @@
 ; OBJ:      VarName: a
 ; OBJ:    }
 ; OBJ:    DefRangeRegisterRelSym {
-; OBJ:      BaseRegister: 335
+; OBJ:      BaseRegister: RSP (0x14F)
 ; OBJ:      HasSpilledUDTMember: No
 ; OBJ:      OffsetInParent: 0
 ; OBJ:      BasePointerOffset: 40
@@ -145,7 +145,7 @@
 ; OBJ:      VarName: b
 ; OBJ:    }
 ; OBJ:    DefRangeRegisterRelSym {
-; OBJ:      BaseRegister: 335
+; OBJ:      BaseRegister: RSP (0x14F)
 ; OBJ:      HasSpilledUDTMember: No
 ; OBJ:      OffsetInParent: 0
 ; OBJ:      BasePointerOffset: 36
@@ -173,7 +173,7 @@
 ; OBJ:      VarName: v
 ; OBJ:    }
 ; OBJ:    DefRangeRegisterRelSym {
-; OBJ:      BaseRegister: 335
+; OBJ:      BaseRegister: RSP (0x14F)
 ; OBJ:      HasSpilledUDTMember: No
 ; OBJ:      OffsetInParent: 0
 ; OBJ:      BasePointerOffset: 44
@@ -203,7 +203,7 @@
 ; OBJ:      VarName: v
 ; OBJ:    }
 ; OBJ:    DefRangeRegisterRelSym {
-; OBJ:      BaseRegister: 335
+; OBJ:      BaseRegister: RSP (0x14F)
 ; OBJ:      HasSpilledUDTMember: No
 ; OBJ:      OffsetInParent: 0
 ; OBJ:      BasePointerOffset: 48
Index: test/DebugInfo/COFF/pieces.ll
===================================================================
--- test/DebugInfo/COFF/pieces.ll
+++ test/DebugInfo/COFF/pieces.ll
@@ -113,14 +113,14 @@
 ; OBJ:         VarName: o
 ; OBJ:       }
 ; OBJ:       DefRangeSubfieldRegisterSym {
-; OBJ:         Register: 24
+; OBJ:         Register: EDI (0x18)
 ; OBJ:         MayHaveNoName: 0
 ; OBJ:         OffsetInParent: 0
 ; OBJ:         LocalVariableAddrRange {
 ; OBJ:         }
 ; OBJ:       }
 ; OBJ:       DefRangeSubfieldRegisterSym {
-; OBJ:         Register: 23
+; OBJ:         Register: ESI (0x17)
 ; OBJ:         MayHaveNoName: 0
 ; OBJ:         OffsetInParent: 4
 ; OBJ:         LocalVariableAddrRange {
@@ -143,7 +143,7 @@
 ; OBJ:         VarName: o
 ; OBJ:       }
 ; OBJ:       DefRangeSubfieldRegisterSym {
-; OBJ:         Register: 18
+; OBJ:         Register: ECX (0x12)
 ; OBJ:         MayHaveNoName: 0
 ; OBJ:         OffsetInParent: 4
 ; OBJ:         LocalVariableAddrRange {
@@ -166,7 +166,7 @@
 ; OBJ:         VarName: o
 ; OBJ:       }
 ; OBJ:       DefRangeSubfieldRegisterSym {
-; OBJ:         Register: 18
+; OBJ:         Register: ECX (0x12)
 ; OBJ:         MayHaveNoName: 0
 ; OBJ:         OffsetInParent: 0
 ; OBJ:         LocalVariableAddrRange {
@@ -193,7 +193,7 @@
 ; OBJ:         VarName: o
 ; OBJ:       }
 ; OBJ:       DefRangeRegisterRelSym {
-; OBJ:         BaseRegister: 330
+; OBJ:         BaseRegister: RCX (0x14A)
 ; OBJ:         HasSpilledUDTMember: No
 ; OBJ:         OffsetInParent: 0
 ; OBJ:         BasePointerOffset: 0
@@ -204,7 +204,7 @@
 ; OBJ:         VarName: p
 ; OBJ:       }
 ; OBJ:       DefRangeSubfieldRegisterSym {
-; OBJ:         Register: 17
+; OBJ:         Register: EAX (0x11)
 ; OBJ:         MayHaveNoName: 0
 ; OBJ:         OffsetInParent: 4
 ; OBJ:         LocalVariableAddrRange {
@@ -228,7 +228,7 @@
 ; OBJ:         VarName: o
 ; OBJ:       }
 ; OBJ:       DefRangeRegisterRelSym {
-; OBJ:         BaseRegister: 335
+; OBJ:         BaseRegister: RSP (0x14F)
 ; OBJ:         HasSpilledUDTMember: Yes
 ; OBJ:         OffsetInParent: 4
 ; OBJ:         BasePointerOffset: 36
Index: test/DebugInfo/COFF/register-variables.ll
===================================================================
--- test/DebugInfo/COFF/register-variables.ll
+++ test/DebugInfo/COFF/register-variables.ll
@@ -92,7 +92,7 @@
 ; OBJ:     VarName: p
 ; OBJ:   }
 ; OBJ:   DefRangeRegisterSym {
-; OBJ:     Register: 18
+; OBJ:     Register: ECX (0x12)
 ; OBJ:     LocalVariableAddrRange {
 ; OBJ:       OffsetStart: .text+0x0
 ; OBJ:       ISectStart: 0x0
@@ -100,7 +100,7 @@
 ; OBJ:     }
 ; OBJ:   }
 ; OBJ:   DefRangeRegisterSym {
-; OBJ:     Register: 23
+; OBJ:     Register: ESI (0x17)
 ; OBJ:     LocalVariableAddrRange {
 ; OBJ:       OffsetStart: .text+0x7
 ; OBJ:       ISectStart: 0x0
@@ -114,7 +114,7 @@
 ; OBJ:     VarName: a
 ; OBJ:   }
 ; OBJ:   DefRangeRegisterSym {
-; OBJ:     Register: 17
+; OBJ:     Register: EAX (0x11)
 ; OBJ:     LocalVariableAddrRange {
 ; OBJ:       OffsetStart: .text+0xC
 ; OBJ:       ISectStart: 0x0
@@ -128,7 +128,7 @@
 ; OBJ:     VarName: c
 ; OBJ:   }
 ; OBJ:   DefRangeRegisterSym {
-; OBJ:     Register: 17
+; OBJ:     Register: EAX (0x11)
 ; OBJ:     LocalVariableAddrRange {
 ; OBJ:       OffsetStart: .text+0xC
 ; OBJ:       ISectStart: 0x0
@@ -142,7 +142,7 @@
 ; OBJ:     VarName: b
 ; OBJ:   }
 ; OBJ:   DefRangeRegisterSym {
-; OBJ:     Register: 17
+; OBJ:     Register: EAX (0x11)
 ; OBJ:     MayHaveNoName: 0
 ; OBJ:       OffsetStart: .text+0x13
 ; OBJ:       ISectStart: 0x0
@@ -162,7 +162,7 @@
 ; OBJ:     VarName: a
 ; OBJ:   }
 ; OBJ:   DefRangeRegisterSym {
-; OBJ:     Register: 17
+; OBJ:     Register: EAX (0x11)
 ; OBJ:     LocalVariableAddrRange {
 ; OBJ:       OffsetStart: .text+0xC
 ; OBJ:       ISectStart: 0x0
@@ -176,7 +176,7 @@
 ; OBJ:     VarName: b
 ; OBJ:   }
 ; OBJ:   DefRangeRegisterSym {
-; OBJ:     Register: 17
+; OBJ:     Register: EAX (0x11)
 ; OBJ:     LocalVariableAddrRange {
 ; OBJ:       OffsetStart: .text+0x13
 ; OBJ:       ISectStart: 0x0
Index: test/DebugInfo/COFF/types-array.ll
===================================================================
--- test/DebugInfo/COFF/types-array.ll
+++ test/DebugInfo/COFF/types-array.ll
@@ -68,7 +68,7 @@
 ; CHECK:       VarName: a
 ; CHECK:     }
 ; CHECK:     DefRangeRegisterRelSym {
-; CHECK:       BaseRegister: 22
+; CHECK:       BaseRegister: EBP (0x16)
 ; CHECK:       HasSpilledUDTMember: No
 ; CHECK:       OffsetInParent: 0
 ; CHECK:       BasePointerOffset: -20
Index: test/DebugInfo/X86/dbg-declare-inalloca.ll
===================================================================
--- test/DebugInfo/X86/dbg-declare-inalloca.ll
+++ test/DebugInfo/X86/dbg-declare-inalloca.ll
@@ -67,7 +67,7 @@
 ; OBJ:   VarName: a
 ; OBJ: }
 ; OBJ: DefRangeRegisterRelSym {
-; OBJ:   BaseRegister: 21
+; OBJ:   BaseRegister: ESP (0x15)
 ; OBJ:   BasePointerOffset: 12
 ; OBJ: }
 ; OBJ: LocalSym {
@@ -78,7 +78,7 @@
 ; OBJ:   VarName: b
 ; OBJ: }
 ; OBJ: DefRangeRegisterRelSym {
-; OBJ:   BaseRegister: 21
+; OBJ:   BaseRegister: ESP (0x15)
 ; OBJ:   BasePointerOffset: 16
 ; OBJ: }
 ; FIXME: Retain unused.
@@ -90,7 +90,7 @@
 ; OBJ:   VarName: c
 ; OBJ: }
 ; OBJ: DefRangeRegisterRelSym {
-; OBJ:   BaseRegister: 21
+; OBJ:   BaseRegister: ESP (0x15)
 ; OBJ:   BasePointerOffset: 24
 ; OBJ: }
 ; OBJ-LABEL: ProcEnd {
Index: test/MC/COFF/cv-def-range-gap.s
===================================================================
--- test/MC/COFF/cv-def-range-gap.s
+++ test/MC/COFF/cv-def-range-gap.s
@@ -9,7 +9,7 @@
 # CHECK-NOT:     LocalSym {
 # CHECK:         DefRangeRegisterSym {
 # CHECK-NEXT:      Kind: S_DEFRANGE_REGISTER (0x1141)
-# CHECK-NEXT:      Register: 23
+# CHECK-NEXT:      Register: ESI (0x17)
 # CHECK-NEXT:      MayHaveNoName: 0
 # CHECK-NEXT:      LocalVariableAddrRange {
 # CHECK-NEXT:        OffsetStart: .text+0x5
@@ -23,7 +23,7 @@
 # CHECK-NEXT:    }
 # CHECK-NEXT:    DefRangeRegisterSym {
 # CHECK-NEXT:      Kind: S_DEFRANGE_REGISTER (0x1141)
-# CHECK-NEXT:      Register: 23
+# CHECK-NEXT:      Register: ESI (0x17)
 # CHECK-NEXT:      MayHaveNoName: 0
 # CHECK-NEXT:      LocalVariableAddrRange {
 # CHECK-NEXT:        OffsetStart: .text+0x10015
@@ -33,7 +33,7 @@
 # CHECK-NEXT:    }
 # CHECK-NEXT:    DefRangeRegisterSym {
 # CHECK-NEXT:      Kind: S_DEFRANGE_REGISTER (0x1141)
-# CHECK-NEXT:      Register: 23
+# CHECK-NEXT:      Register: ESI (0x17)
 # CHECK-NEXT:      MayHaveNoName: 0
 # CHECK-NEXT:      LocalVariableAddrRange {
 # CHECK-NEXT:        OffsetStart: .text+0x2001B
@@ -43,7 +43,7 @@
 # CHECK-NEXT:    }
 # CHECK-NEXT:    DefRangeRegisterSym {
 # CHECK-NEXT:      Kind: S_DEFRANGE_REGISTER (0x1141)
-# CHECK-NEXT:      Register: 23
+# CHECK-NEXT:      Register: ESI (0x17)
 # CHECK-NEXT:      MayHaveNoName: 0
 # CHECK-NEXT:      LocalVariableAddrRange {
 # CHECK-NEXT:        OffsetStart: .text+0x2001C