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
@@ -39,6 +39,7 @@
   const uint16_t RegsSize;
   const uint16_t RegSetSize;
   const uint16_t ID;
+  const uint16_t PhysRegSize;
   const int8_t CopyCost;
   const bool Allocatable;
 
@@ -78,6 +79,11 @@
     return contains(Reg1) && contains(Reg2);
   }
 
+  /// Return the size of the physical register in bytes.
+  unsigned getPhysRegSize() const { return PhysRegSize; }
+  /// Temporary function to allow out-of-tree targets to switch.
+  unsigned getSize() const { return getPhysRegSize(); }
+
   /// getCopyCost - Return the cost of copying a value between two registers in
   /// this class. A negative number means the register class is very expensive
   /// to copy e.g. status flag register classes.
diff --git a/llvm/lib/CodeGen/TargetInstrInfo.cpp b/llvm/lib/CodeGen/TargetInstrInfo.cpp
--- a/llvm/lib/CodeGen/TargetInstrInfo.cpp
+++ b/llvm/lib/CodeGen/TargetInstrInfo.cpp
@@ -397,7 +397,8 @@
     return true;
   }
   unsigned BitSize = TRI->getSubRegIdxSize(SubIdx);
-  // Convert bit size to byte size.
+  // Convert bit size to byte size to be consistent with
+  // MCRegisterClass::getSize().
   if (BitSize % 8)
     return false;
 
diff --git a/llvm/utils/TableGen/RegisterInfoEmitter.cpp b/llvm/utils/TableGen/RegisterInfoEmitter.cpp
--- a/llvm/utils/TableGen/RegisterInfoEmitter.cpp
+++ b/llvm/utils/TableGen/RegisterInfoEmitter.cpp
@@ -1084,10 +1084,14 @@
 
   for (const auto &RC : RegisterClasses) {
     assert(isInt<8>(RC.CopyCost) && "Copy cost too large.");
+    uint32_t RegSize = 0;
+    if (RC.RSI.isSimple())
+      RegSize = RC.RSI.getSimple().RegSize;
     OS << "  { " << RC.getName() << ", " << RC.getName() << "Bits, "
        << RegClassStrings.get(RC.getName()) << ", "
        << RC.getOrder().size() << ", sizeof(" << RC.getName() << "Bits), "
        << RC.getQualifiedName() + "RegClassID" << ", "
+       << RegSize/8 << ", "
        << RC.CopyCost << ", "
        << ( RC.Allocatable ? "true" : "false" ) << " },\n";
   }