Index: llvm/include/llvm/CodeGen/MachineInstr.h
===================================================================
--- llvm/include/llvm/CodeGen/MachineInstr.h
+++ llvm/include/llvm/CodeGen/MachineInstr.h
@@ -120,7 +120,7 @@
 
   // Operands are allocated by an ArrayRecycler.
   MachineOperand *Operands = nullptr;   // Pointer to the first operand.
-  unsigned NumOperands = 0;             // Number of operands on instruction.
+  uint16_t NumOperands = 0;             // Number of operands on instruction.
 
   uint16_t Flags = 0;                   // Various bits of additional
                                         // information about machine
@@ -516,7 +516,7 @@
   unsigned getOpcode() const { return MCID->Opcode; }
 
   /// Retuns the total number of operands.
-  unsigned getNumOperands() const { return NumOperands; }
+  uint16_t getNumOperands() const { return NumOperands; }
 
   /// Returns the total number of operands which are debug locations.
   unsigned getNumDebugOperands() const {
@@ -604,7 +604,7 @@
   }
 
   /// Returns the implicit operands number.
-  unsigned getNumImplicitOperands() const {
+  uint16_t getNumImplicitOperands() const {
     return getNumOperands() - getNumExplicitOperands();
   }
 
@@ -623,7 +623,7 @@
   }
 
   /// Returns the number of non-implicit operands.
-  unsigned getNumExplicitOperands() const;
+  unsigned short getNumExplicitOperands() const;
 
   /// Returns the number of non-implicit definitions.
   unsigned getNumExplicitDefs() const;
Index: llvm/lib/CodeGen/MachineFunction.cpp
===================================================================
--- llvm/lib/CodeGen/MachineFunction.cpp
+++ llvm/lib/CodeGen/MachineFunction.cpp
@@ -945,7 +945,7 @@
   // While this has no functional effect, it risks confusing someone reading
   // MIR output.
   // Examine all the operands, or the first N specified by the caller.
-  MaxOperand = std::min(MaxOperand, Old.getNumOperands());
+  MaxOperand = std::min(MaxOperand, static_cast<unsigned>(Old.getNumOperands()));
   for (unsigned int I = 0; I < MaxOperand; ++I) {
     const auto &OldMO = Old.getOperand(I);
     auto &NewMO = New.getOperand(I);
Index: llvm/lib/CodeGen/MachineInstr.cpp
===================================================================
--- llvm/lib/CodeGen/MachineInstr.cpp
+++ llvm/lib/CodeGen/MachineInstr.cpp
@@ -57,6 +57,7 @@
 #include <cassert>
 #include <cstdint>
 #include <cstring>
+#include <limits>
 #include <utility>
 
 using namespace llvm;
@@ -192,6 +193,7 @@
 /// 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 < std::numeric_limits<uint16_t>::max() && "Cannot add more operands.");
   assert(MCID && "Cannot add operands before providing an instr descriptor");
 
   // Check if we're adding one of our existing operands.
@@ -738,12 +740,12 @@
   return isCandidateForCallSiteEntry();
 }
 
-unsigned MachineInstr::getNumExplicitOperands() const {
-  unsigned NumOperands = MCID->getNumOperands();
+uint16_t MachineInstr::getNumExplicitOperands() const {
+  uint16_t NumOperands = MCID->getNumOperands();
   if (!MCID->isVariadic())
     return NumOperands;
 
-  for (unsigned I = NumOperands, E = getNumOperands(); I != E; ++I) {
+  for (uint16_t I = NumOperands, E = getNumOperands(); I != E; ++I) {
     const MachineOperand &MO = getOperand(I);
     // The operands must always be in the following order:
     // - explicit reg defs,