diff --git a/llvm/lib/DebugInfo/CodeView/Formatters.cpp b/llvm/lib/DebugInfo/CodeView/Formatters.cpp
--- a/llvm/lib/DebugInfo/CodeView/Formatters.cpp
+++ b/llvm/lib/DebugInfo/CodeView/Formatters.cpp
@@ -25,11 +25,13 @@
 
 void GuidAdapter::format(raw_ostream &Stream, StringRef Style) {
   static const char *Lookup = "0123456789ABCDEF";
+  static const uint8_t Order[16] = {3, 2, 1,  0,  5,  4,  7,  6,
+                                    8, 9, 10, 11, 12, 13, 14, 15};
 
   assert(Item.size() == 16 && "Expected 16-byte GUID");
   Stream << "{";
   for (int i = 0; i < 16;) {
-    uint8_t Byte = Item[i];
+    uint8_t Byte = Item[Order[i]];
     uint8_t HighNibble = (Byte >> 4) & 0xF;
     uint8_t LowNibble = Byte & 0xF;
     Stream << Lookup[HighNibble] << Lookup[LowNibble];
diff --git a/llvm/lib/ObjectYAML/CodeViewYAMLTypes.cpp b/llvm/lib/ObjectYAML/CodeViewYAMLTypes.cpp
--- a/llvm/lib/ObjectYAML/CodeViewYAMLTypes.cpp
+++ b/llvm/lib/ObjectYAML/CodeViewYAMLTypes.cpp
@@ -146,6 +146,8 @@
 }
 
 StringRef ScalarTraits<GUID>::input(StringRef Scalar, void *Ctx, GUID &S) {
+  static const uint8_t Order[16] = {3, 2, 1,  0,  5,  4,  7,  6,
+                                    8, 9, 10, 11, 12, 13, 14, 15};
   if (Scalar.size() != 38)
     return "GUID strings are 38 characters long";
   if (Scalar[0] != '{' || Scalar[37] != '}')
@@ -154,7 +156,7 @@
       Scalar[24] != '-')
     return "GUID sections are not properly delineated with dashes";
 
-  uint8_t *OutBuffer = S.Guid;
+  uint8_t I = 0;
   for (auto Iter = Scalar.begin(); Iter != Scalar.end();) {
     if (*Iter == '-' || *Iter == '{' || *Iter == '}') {
       ++Iter;
@@ -162,7 +164,7 @@
     }
     uint8_t Value = (llvm::hexDigitValue(*Iter++) << 4);
     Value |= llvm::hexDigitValue(*Iter++);
-    *OutBuffer++ = Value;
+    S.Guid[Order[I++]] = Value;
   }
 
   return "";
diff --git a/llvm/test/DebugInfo/PDB/DIA/pdbdump-flags.test b/llvm/test/DebugInfo/PDB/DIA/pdbdump-flags.test
--- a/llvm/test/DebugInfo/PDB/DIA/pdbdump-flags.test
+++ b/llvm/test/DebugInfo/PDB/DIA/pdbdump-flags.test
@@ -5,7 +5,7 @@
 
 ; Check that neither symbols nor compilands are dumped when neither argument specified.
 ; NO_ARGS: empty.pdb
-; NO_ARGS: Guid: {0B355641-86A0-A249-896F-9988FAE52FF0}
+; NO_ARGS: Guid: {4156350B-A086-49A2-896F-9988FAE52FF0}
 ; NO_ARGS: Attributes: HasPrivateSymbols
 ; NO_ARGS-NOT: ---TYPES---
 ; NO_ARGS-NOT: ---COMPILANDS---
@@ -14,7 +14,7 @@
 
 ; Check that only types are dumped when only -types is specified.
 ; TYPES: empty.pdb
-; TYPES: Guid: {0B355641-86A0-A249-896F-9988FAE52FF0}
+; TYPES: Guid: {4156350B-A086-49A2-896F-9988FAE52FF0}
 ; TYPES: Attributes: HasPrivateSymbols
 ; TYPES: ---TYPES---
 ; TYPES-NOT: ---COMPILANDS---
@@ -23,7 +23,7 @@
 
 ; Check that only compilands are dumped when only -compilands is specified.
 ; COMPILANDS: empty.pdb
-; COMPILANDS: Guid: {0B355641-86A0-A249-896F-9988FAE52FF0}
+; COMPILANDS: Guid: {4156350B-A086-49A2-896F-9988FAE52FF0}
 ; COMPILANDS: Attributes: HasPrivateSymbols
 ; COMPILANDS: ---COMPILANDS---
 ; COMPILANDS-NOT: ---TYPES---
@@ -32,7 +32,7 @@
 
 ; Check that types and compilands are dumped when both arguments are specified.
 ; MULTIPLE: empty.pdb
-; MULTIPLE: Guid: {0B355641-86A0-A249-896F-9988FAE52FF0}
+; MULTIPLE: Guid: {4156350B-A086-49A2-896F-9988FAE52FF0}
 ; MULTIPLE: Attributes: HasPrivateSymbols
 ; MULTIPLE: ---COMPILANDS---
 ; MULTIPLE: ---TYPES---
diff --git a/llvm/test/DebugInfo/PDB/Native/pdb-native-summary.test b/llvm/test/DebugInfo/PDB/Native/pdb-native-summary.test
--- a/llvm/test/DebugInfo/PDB/Native/pdb-native-summary.test
+++ b/llvm/test/DebugInfo/PDB/Native/pdb-native-summary.test
@@ -6,6 +6,6 @@
 ; `-native` option produces identical output.
 
 ; EMPTY:  Size: 102400 bytes
-; EMPTY:  Guid: {0B355641-86A0-A249-896F-9988FAE52FF0}
+; EMPTY:  Guid: {4156350B-A086-49A2-896F-9988FAE52FF0}
 ; EMPTY:  Age: 1
 ; EMPTY:  Attributes: HasPrivateSymbols
diff --git a/llvm/test/DebugInfo/PDB/pdbdump-headers.test b/llvm/test/DebugInfo/PDB/pdbdump-headers.test
--- a/llvm/test/DebugInfo/PDB/pdbdump-headers.test
+++ b/llvm/test/DebugInfo/PDB/pdbdump-headers.test
@@ -12,7 +12,7 @@
 ALL-NEXT:   Number of streams: 17
 ALL-NEXT:   Signature: 1424295906
 ALL-NEXT:   Age: 1
-ALL-NEXT:   GUID: {0B355641-86A0-A249-896F-9988FAE52FF0}
+ALL-NEXT:   GUID: {4156350B-A086-49A2-896F-9988FAE52FF0}
 ALL-NEXT:   Features: 0x1
 ALL-NEXT:   Has Debug Info: true
 ALL-NEXT:   Has Types: true
@@ -601,7 +601,7 @@
 BIG-NEXT:   Number of streams: 64
 BIG-NEXT:   Signature: 1461714535
 BIG-NEXT:   Age: 1
-BIG-NEXT:   GUID: {880ECC89-DF81-0B4F-839C-58CBD052E937}
+BIG-NEXT:   GUID: {89CC0E88-81DF-4F0B-839C-58CBD052E937}
 BIG-NEXT:   Features: 0x1
 BIG-NEXT:   Has Debug Info: true
 BIG-NEXT:   Has Types: true
diff --git a/llvm/test/DebugInfo/PDB/pdbdump-readwrite.test b/llvm/test/DebugInfo/PDB/pdbdump-readwrite.test
--- a/llvm/test/DebugInfo/PDB/pdbdump-readwrite.test
+++ b/llvm/test/DebugInfo/PDB/pdbdump-readwrite.test
@@ -14,7 +14,7 @@
 CHECK-NEXT:  Number of streams:
 CHECK-NEXT:  Signature: 1424295906
 CHECK-NEXT:  Age: 1
-CHECK-NEXT:  GUID: {0B355641-86A0-A249-896F-9988FAE52FF0}
+CHECK-NEXT:  GUID: {4156350B-A086-49A2-896F-9988FAE52FF0}
 CHECK-NEXT:  Features: 0x1
 CHECK-NEXT:  Has Debug Info: true
 CHECK-NEXT:  Has Types: true
diff --git a/llvm/test/DebugInfo/PDB/pdbdump-yaml.test b/llvm/test/DebugInfo/PDB/pdbdump-yaml.test
--- a/llvm/test/DebugInfo/PDB/pdbdump-yaml.test
+++ b/llvm/test/DebugInfo/PDB/pdbdump-yaml.test
@@ -42,7 +42,7 @@
 ; YAML-NEXT:   - '$T0 $ebp = $eip $T0 4 + ^ = $ebp $T0 ^ = $esp $T0 8 + = '
 ; YAML-NEXT: PdbStream:
 ; YAML-NEXT:   Age:             1
-; YAML-NEXT:   Guid:            '{0B355641-86A0-A249-896F-9988FAE52FF0}'
+; YAML-NEXT:   Guid:            '{4156350B-A086-49A2-896F-9988FAE52FF0}'
 ; YAML-NEXT:   Signature:       1424295906
 ; YAML-NEXT:   Features:        [ VC110 ]
 ; YAML-NEXT:   Version:         VC70
diff --git a/llvm/test/ObjectYAML/CodeView/sections.yaml b/llvm/test/ObjectYAML/CodeView/sections.yaml
--- a/llvm/test/ObjectYAML/CodeView/sections.yaml
+++ b/llvm/test/ObjectYAML/CodeView/sections.yaml
@@ -13,7 +13,7 @@
     Types:
       - Kind:            LF_TYPESERVER2
         TypeServer2:
-          Guid:            '{01DF191B-22BF-6B42-96CE-5258B8329FE5}'
+          Guid:            '{1B19DF01-BF22-426B-96CE-5258B8329FE5}'
           Age:             24
           Name:            'C:\src\llvm-project\build\vc140.pdb'
   - Name:            '.debug$H'
@@ -66,7 +66,7 @@
 # CHECK:     Types:
 # CHECK:       - Kind:            LF_TYPESERVER2
 # CHECK:         TypeServer2:
-# CHECK:           Guid:            '{01DF191B-22BF-6B42-96CE-5258B8329FE5}'
+# CHECK:           Guid:            '{1B19DF01-BF22-426B-96CE-5258B8329FE5}'
 # CHECK:           Age:             24
 # CHECK:           Name:            'C:\src\llvm-project\build\vc140.pdb'
 # CHECK:   - Name:            '.debug$H'
diff --git a/llvm/test/tools/llvm-pdbutil/explain-pdb-stream.test b/llvm/test/tools/llvm-pdbutil/explain-pdb-stream.test
--- a/llvm/test/tools/llvm-pdbutil/explain-pdb-stream.test
+++ b/llvm/test/tools/llvm-pdbutil/explain-pdb-stream.test
@@ -39,7 +39,7 @@
 CHECK-NEXT:   Within the PDB stream:
 CHECK-NEXT:     address is at offset 12/28 of the PDB Stream Header.
 CHECK-NEXT:     which contains the guid of the PDB.
-CHECK-NEXT:     The current value is {826BE46E-02ED-7043-9C27-20CCC07E92A7}.
+CHECK-NEXT:     The current value is {6EE46B82-ED02-4370-9C27-20CCC07E92A7}.
 
 CHECK:      Block:Offset = 11:001C.
 CHECK-NEXT: Address is in block 17 (allocated).
diff --git a/llvm/test/tools/llvm-pdbutil/stripped.test b/llvm/test/tools/llvm-pdbutil/stripped.test
--- a/llvm/test/tools/llvm-pdbutil/stripped.test
+++ b/llvm/test/tools/llvm-pdbutil/stripped.test
@@ -8,7 +8,7 @@
 ; CHECK-NEXT:  Number of streams: 12
 ; CHECK-NEXT:  Signature: 1541179274
 ; CHECK-NEXT:  Age: 2
-; CHECK-NEXT:  GUID: {FF4F9B62-D99A-4647-97A7-22C702B1E053}
+; CHECK-NEXT:  GUID: {629B4FFF-9AD9-4746-97A7-22C702B1E053}
 ; CHECK-NEXT:  Features: 0x1
 ; CHECK-NEXT:  Has Debug Info: true
 ; CHECK-NEXT:  Has Types: true