diff --git a/llvm/include/llvm/MC/MCDwarf.h b/llvm/include/llvm/MC/MCDwarf.h
index 5052c6756c32bd..18056c5fdf816a 100644
--- a/llvm/include/llvm/MC/MCDwarf.h
+++ b/llvm/include/llvm/MC/MCDwarf.h
@@ -483,7 +483,7 @@ class MCGenDwarfLabelEntry {
 
 class MCCFIInstruction {
 public:
-  enum OpType : uint8_t {
+  enum OpType {
     OpSameValue,
     OpRememberState,
     OpRestoreState,
@@ -504,44 +504,35 @@ class MCCFIInstruction {
   };
 
 private:
+  OpType Operation;
   MCSymbol *Label;
+  unsigned Register;
   union {
-    struct {
-      unsigned Register;
-      int Offset;
-    } RI;
-    struct {
-      unsigned Register;
-      int Offset;
-      unsigned AddressSpace;
-    } RIA;
-    struct {
-      unsigned Register;
-      unsigned Register2;
-    } RR;
-  } U;
-  OpType Operation;
+    int Offset;
+    unsigned Register2;
+  };
+  unsigned AddressSpace = ~0u;
   SMLoc Loc;
   std::vector<char> Values;
   std::string Comment;
 
   MCCFIInstruction(OpType Op, MCSymbol *L, unsigned R, int O, SMLoc Loc,
                    StringRef V = "", StringRef Comment = "")
-      : Label(L), Operation(Op), Loc(Loc), Values(V.begin(), V.end()),
-        Comment(Comment) {
+      : Operation(Op), Label(L), Register(R), Offset(O), Loc(Loc),
+        Values(V.begin(), V.end()), Comment(Comment) {
     assert(Op != OpRegister && Op != OpLLVMDefAspaceCfa);
-    U.RI = {R, O};
   }
+
   MCCFIInstruction(OpType Op, MCSymbol *L, unsigned R1, unsigned R2, SMLoc Loc)
-      : Label(L), Operation(Op), Loc(Loc) {
+      : Operation(Op), Label(L), Register(R1), Register2(R2), Loc(Loc) {
     assert(Op == OpRegister);
-    U.RR = {R1, R2};
   }
+
   MCCFIInstruction(OpType Op, MCSymbol *L, unsigned R, int O, unsigned AS,
                    SMLoc Loc)
-      : Label(L), Operation(Op), Loc(Loc) {
+      : Operation(Op), Label(L), Register(R), Offset(O), AddressSpace(AS),
+        Loc(Loc) {
     assert(Op == OpLLVMDefAspaceCfa);
-    U.RIA = {R, O, AS};
   }
 
 public:
@@ -668,34 +659,30 @@ class MCCFIInstruction {
   MCSymbol *getLabel() const { return Label; }
 
   unsigned getRegister() const {
-    if (Operation == OpRegister)
-      return U.RR.Register;
-    if (Operation == OpLLVMDefAspaceCfa)
-      return U.RIA.Register;
     assert(Operation == OpDefCfa || Operation == OpOffset ||
            Operation == OpRestore || Operation == OpUndefined ||
            Operation == OpSameValue || Operation == OpDefCfaRegister ||
-           Operation == OpRelOffset);
-    return U.RI.Register;
+           Operation == OpRelOffset || Operation == OpRegister ||
+           Operation == OpLLVMDefAspaceCfa);
+    return Register;
   }
 
   unsigned getRegister2() const {
     assert(Operation == OpRegister);
-    return U.RR.Register2;
+    return Register2;
   }
 
   unsigned getAddressSpace() const {
     assert(Operation == OpLLVMDefAspaceCfa);
-    return U.RIA.AddressSpace;
+    return AddressSpace;
   }
 
   int getOffset() const {
-    if (Operation == OpLLVMDefAspaceCfa)
-      return U.RIA.Offset;
     assert(Operation == OpDefCfa || Operation == OpOffset ||
            Operation == OpRelOffset || Operation == OpDefCfaOffset ||
-           Operation == OpAdjustCfaOffset || Operation == OpGnuArgsSize);
-    return U.RI.Offset;
+           Operation == OpAdjustCfaOffset || Operation == OpGnuArgsSize ||
+           Operation == OpLLVMDefAspaceCfa);
+    return Offset;
   }
 
   StringRef getValues() const {