diff --git a/llvm/include/llvm/MC/MCAsmMacro.h b/llvm/include/llvm/MC/MCAsmMacro.h
--- a/llvm/include/llvm/MC/MCAsmMacro.h
+++ b/llvm/include/llvm/MC/MCAsmMacro.h
@@ -63,7 +63,7 @@
   };
 
 private:
-  TokenKind Kind;
+  TokenKind Kind = TokenKind::Eof;
 
   /// A reference to the entire token contents; this is always a pointer into
   /// a memory buffer owned by the source manager.
diff --git a/llvm/include/llvm/MC/MCDwarf.h b/llvm/include/llvm/MC/MCDwarf.h
--- a/llvm/include/llvm/MC/MCDwarf.h
+++ b/llvm/include/llvm/MC/MCDwarf.h
@@ -506,7 +506,7 @@
     int Offset;
     unsigned Register2;
   };
-  unsigned AddressSpace;
+  unsigned AddressSpace = ~0u;
   std::vector<char> Values;
   std::string Comment;
 
diff --git a/llvm/include/llvm/MC/MCMachObjectWriter.h b/llvm/include/llvm/MC/MCMachObjectWriter.h
--- a/llvm/include/llvm/MC/MCMachObjectWriter.h
+++ b/llvm/include/llvm/MC/MCMachObjectWriter.h
@@ -32,7 +32,7 @@
 protected:
   uint32_t CPUSubtype;
 public:
-  unsigned LocalDifference_RIT;
+  unsigned LocalDifference_RIT = 0;
 
 protected:
   MCMachObjectTargetWriter(bool Is64Bit_, uint32_t CPUType_,
diff --git a/llvm/include/llvm/MC/MCObjectStreamer.h b/llvm/include/llvm/MC/MCObjectStreamer.h
--- a/llvm/include/llvm/MC/MCObjectStreamer.h
+++ b/llvm/include/llvm/MC/MCObjectStreamer.h
@@ -46,7 +46,7 @@
   bool EmitDebugFrame;
   SmallVector<MCSymbol *, 2> PendingLabels;
   SmallSetVector<MCSection *, 4> PendingLabelSections;
-  unsigned CurSubsectionIdx;
+  unsigned CurSubsectionIdx = 0;
   struct PendingMCFixup {
     const MCSymbol *Sym;
     MCFixup Fixup;
diff --git a/llvm/include/llvm/MC/MCParser/MCAsmLexer.h b/llvm/include/llvm/MC/MCParser/MCAsmLexer.h
--- a/llvm/include/llvm/MC/MCParser/MCAsmLexer.h
+++ b/llvm/include/llvm/MC/MCParser/MCAsmLexer.h
@@ -45,7 +45,7 @@
 protected: // Can only create subclasses.
   const char *TokStart = nullptr;
   bool SkipSpace = true;
-  bool AllowAtInIdentifier;
+  bool AllowAtInIdentifier = false;
   bool AllowHashInIdentifier = false;
   bool IsAtStartOfStatement = true;
   bool LexMasmHexFloats = false;
diff --git a/llvm/include/llvm/MC/MCParser/MCParsedAsmOperand.h b/llvm/include/llvm/MC/MCParser/MCParsedAsmOperand.h
--- a/llvm/include/llvm/MC/MCParser/MCParsedAsmOperand.h
+++ b/llvm/include/llvm/MC/MCParser/MCParsedAsmOperand.h
@@ -24,7 +24,7 @@
 class MCParsedAsmOperand {
   /// MCOperandNum - The corresponding MCInst operand number.  Only valid when
   /// parsing MS-style inline assembly.
-  unsigned MCOperandNum;
+  unsigned MCOperandNum = ~0u;
 
   /// Constraint - The constraint on this operand.  Only valid when parsing
   /// MS-style inline assembly.
diff --git a/llvm/include/llvm/MC/MCRegisterInfo.h b/llvm/include/llvm/MC/MCRegisterInfo.h
--- a/llvm/include/llvm/MC/MCRegisterInfo.h
+++ b/llvm/include/llvm/MC/MCRegisterInfo.h
@@ -243,7 +243,7 @@
                                     std::forward_iterator_tag, MCPhysReg> {
     MCRegisterInfo::DiffListIterator Iter;
     /// Current value as MCPhysReg, so we can return a reference to it.
-    MCPhysReg Val;
+    MCPhysReg Val = 0;
 
   protected:
     mc_difflist_iterator(MCRegisterInfo::DiffListIterator Iter) : Iter(Iter) {}
diff --git a/llvm/include/llvm/MC/MCSection.h b/llvm/include/llvm/MC/MCSection.h
--- a/llvm/include/llvm/MC/MCSection.h
+++ b/llvm/include/llvm/MC/MCSection.h
@@ -74,7 +74,7 @@
   /// The section index in the assemblers section list.
   unsigned Ordinal = 0;
   /// The index of this section in the layout order.
-  unsigned LayoutOrder;
+  unsigned LayoutOrder = 0;
 
   /// Keeping track of bundle-locked state.
   BundleLockStateType BundleLockState = NotBundleLocked;
diff --git a/llvm/lib/MC/ELFObjectWriter.cpp b/llvm/lib/MC/ELFObjectWriter.cpp
--- a/llvm/lib/MC/ELFObjectWriter.cpp
+++ b/llvm/lib/MC/ELFObjectWriter.cpp
@@ -128,11 +128,11 @@
   /// @}
 
   // This holds the symbol table index of the last local symbol.
-  unsigned LastLocalSymbolIndex;
+  unsigned LastLocalSymbolIndex = ~0u;
   // This holds the .strtab section index.
-  unsigned StringTableIndex;
+  unsigned StringTableIndex = ~0u;
   // This holds the .symtab section index.
-  unsigned SymbolTableIndex;
+  unsigned SymbolTableIndex = ~0u;
 
   // Sections in the order they are to be output in the section table.
   std::vector<const MCSectionELF *> SectionTable;
diff --git a/llvm/lib/MC/WinCOFFObjectWriter.cpp b/llvm/lib/MC/WinCOFFObjectWriter.cpp
--- a/llvm/lib/MC/WinCOFFObjectWriter.cpp
+++ b/llvm/lib/MC/WinCOFFObjectWriter.cpp
@@ -79,7 +79,7 @@
   using AuxiliarySymbols = SmallVector<AuxSymbol, 1>;
 
   name Name;
-  int Index;
+  int Index = 0;
   AuxiliarySymbols Aux;
   COFFSymbol *Other = nullptr;
   COFFSection *Section = nullptr;
@@ -115,7 +115,7 @@
   COFF::section Header = {};
 
   std::string Name;
-  int Number;
+  int Number = 0;
   MCSectionCOFF const *MCSection = nullptr;
   COFFSymbol *Symbol = nullptr;
   relocations Relocations;
diff --git a/llvm/lib/MC/XCOFFObjectWriter.cpp b/llvm/lib/MC/XCOFFObjectWriter.cpp
--- a/llvm/lib/MC/XCOFFObjectWriter.cpp
+++ b/llvm/lib/MC/XCOFFObjectWriter.cpp
@@ -206,7 +206,7 @@
 
 struct ExceptionTableEntry {
   const MCSymbol *Trap;
-  uint64_t TrapAddress;
+  uint64_t TrapAddress = ~0ul;
   unsigned Lang;
   unsigned Reason;