diff --git a/llvm/include/llvm/CodeGen/MachineInstr.h b/llvm/include/llvm/CodeGen/MachineInstr.h
--- a/llvm/include/llvm/CodeGen/MachineInstr.h
+++ b/llvm/include/llvm/CodeGen/MachineInstr.h
@@ -29,6 +29,7 @@
 #include "llvm/MC/MCInstrDesc.h"
 #include "llvm/MC/MCSymbol.h"
 #include "llvm/Support/ArrayRecycler.h"
+#include "llvm/Support/MathExtras.h"
 #include "llvm/Support/TrailingObjects.h"
 #include <algorithm>
 #include <cassert>
@@ -121,22 +122,27 @@
 
   // Operands are allocated by an ArrayRecycler.
   MachineOperand *Operands = nullptr;   // Pointer to the first operand.
-  uint32_t Flags = 0;                   // Various bits of additional
-                                        // information about machine
-                                        // instruction.
-  uint16_t NumOperands = 0;             // Number of operands on instruction.
-  uint8_t AsmPrinterFlags = 0;          // Various bits of information used by
-                                        // the AsmPrinter to emit helpful
-                                        // comments.  This is *not* semantic
-                                        // information.  Do not use this for
-                                        // anything other than to convey comment
-                                        // information to AsmPrinter.
-
-  // OperandCapacity has uint8_t size, so it should be next to AsmPrinterFlags
+
+#define LLVM_MI_NUMOPERANDS_BITS 24
+#define LLVM_MI_FLAGS_BITS 24
+#define LLVM_MI_ASMPRINTERFLAGS_BITS 8
+
+  /// Number of operands on instruction.
+  uint32_t NumOperands : LLVM_MI_NUMOPERANDS_BITS;
+
+  // OperandCapacity has uint8_t size, so it should be next to NumOperands
   // to properly pack.
   using OperandCapacity = ArrayRecycler<MachineOperand>::Capacity;
   OperandCapacity CapOperands;          // Capacity of the Operands array.
 
+  /// Various bits of additional information about the machine instruction.
+  uint32_t Flags : LLVM_MI_FLAGS_BITS;
+
+  /// Various bits of information used by the AsmPrinter to emit helpful
+  /// comments.  This is *not* semantic information.  Do not use this for
+  /// anything other than to convey comment information to AsmPrinter.
+  uint8_t AsmPrinterFlags : LLVM_MI_ASMPRINTERFLAGS_BITS;
+
   /// Internal implementation detail class that provides out-of-line storage for
   /// extra info used by the machine instruction when this info cannot be stored
   /// in-line within the instruction itself.
@@ -342,16 +348,22 @@
 
   /// Return whether an AsmPrinter flag is set.
   bool getAsmPrinterFlag(CommentFlag Flag) const {
+    assert(isUInt<LLVM_MI_ASMPRINTERFLAGS_BITS>(unsigned(Flag)) &&
+           "Flag is out of range for the AsmPrinterFlags field");
     return AsmPrinterFlags & Flag;
   }
 
   /// Set a flag for the AsmPrinter.
   void setAsmPrinterFlag(uint8_t Flag) {
+    assert(isUInt<LLVM_MI_ASMPRINTERFLAGS_BITS>(unsigned(Flag)) &&
+           "Flag is out of range for the AsmPrinterFlags field");
     AsmPrinterFlags |= Flag;
   }
 
   /// Clear specific AsmPrinter flags.
   void clearAsmPrinterFlag(CommentFlag Flag) {
+    assert(isUInt<LLVM_MI_ASMPRINTERFLAGS_BITS>(unsigned(Flag)) &&
+           "Flag is out of range for the AsmPrinterFlags field");
     AsmPrinterFlags &= ~Flag;
   }
 
@@ -362,15 +374,21 @@
 
   /// Return whether an MI flag is set.
   bool getFlag(MIFlag Flag) const {
+    assert(isUInt<LLVM_MI_FLAGS_BITS>(unsigned(Flag)) &&
+           "Flag is out of range for the Flags field");
     return Flags & Flag;
   }
 
   /// Set a MI flag.
   void setFlag(MIFlag Flag) {
+    assert(isUInt<LLVM_MI_FLAGS_BITS>(unsigned(Flag)) &&
+           "Flag is out of range for the Flags field");
     Flags |= (uint32_t)Flag;
   }
 
   void setFlags(unsigned flags) {
+    assert(isUInt<LLVM_MI_FLAGS_BITS>(flags) &&
+           "flags to be set are out of range for the Flags field");
     // Filter out the automatically maintained flags.
     unsigned Mask = BundledPred | BundledSucc;
     Flags = (Flags & Mask) | (flags & ~Mask);
@@ -378,6 +396,8 @@
 
   /// clearFlag - Clear a MI flag.
   void clearFlag(MIFlag Flag) {
+    assert(isUInt<LLVM_MI_FLAGS_BITS>(unsigned(Flag)) &&
+           "Flag to clear is out of range for the Flags field");
     Flags &= ~((uint32_t)Flag);
   }
 
diff --git a/llvm/lib/CodeGen/MachineInstr.cpp b/llvm/lib/CodeGen/MachineInstr.cpp
--- a/llvm/lib/CodeGen/MachineInstr.cpp
+++ b/llvm/lib/CodeGen/MachineInstr.cpp
@@ -96,7 +96,8 @@
 /// the MCInstrDesc.
 MachineInstr::MachineInstr(MachineFunction &MF, const MCInstrDesc &TID,
                            DebugLoc DL, bool NoImp)
-    : MCID(&TID), DbgLoc(std::move(DL)), DebugInstrNum(0) {
+    : MCID(&TID), NumOperands(0), Flags(0), AsmPrinterFlags(0),
+      DbgLoc(std::move(DL)), DebugInstrNum(0) {
   assert(DbgLoc.hasTrivialDestructor() && "Expected trivial destructor");
 
   // Reserve space for the expected number of operands.
@@ -114,8 +115,8 @@
 /// Does not copy the number from debug instruction numbering, to preserve
 /// uniqueness.
 MachineInstr::MachineInstr(MachineFunction &MF, const MachineInstr &MI)
-    : MCID(&MI.getDesc()), Info(MI.Info), DbgLoc(MI.getDebugLoc()),
-      DebugInstrNum(0) {
+    : MCID(&MI.getDesc()), NumOperands(0), Flags(0), AsmPrinterFlags(0),
+      Info(MI.Info), DbgLoc(MI.getDebugLoc()), DebugInstrNum(0) {
   assert(DbgLoc.hasTrivialDestructor() && "Expected trivial destructor");
 
   CapOperands = OperandCapacity::get(MI.getNumOperands());
@@ -192,7 +193,8 @@
 /// an explicit operand it is added at the end of the explicit operand list
 /// (before the first implicit operand).
 void MachineInstr::addOperand(MachineFunction &MF, const MachineOperand &Op) {
-  assert(NumOperands < USHRT_MAX && "Cannot add more operands.");
+  assert(isUInt<LLVM_MI_NUMOPERANDS_BITS>(NumOperands + 1) &&
+         "Cannot add more operands.");
   assert(MCID && "Cannot add operands before providing an instr descriptor");
 
   // Check if we're adding one of our existing operands.