diff --git a/llvm/lib/Target/AMDGPU/SIRegisterInfo.cpp b/llvm/lib/Target/AMDGPU/SIRegisterInfo.cpp
--- a/llvm/lib/Target/AMDGPU/SIRegisterInfo.cpp
+++ b/llvm/lib/Target/AMDGPU/SIRegisterInfo.cpp
@@ -61,7 +61,8 @@
          "getNumCoveredRegs() will not work with generated subreg masks!");
 
   RegPressureIgnoredUnits.resize(getNumRegUnits());
-  RegPressureIgnoredUnits.set(*MCRegUnitIterator(AMDGPU::M0, this));
+  RegPressureIgnoredUnits.set(
+      *MCRegUnitIterator(MCRegister::from(AMDGPU::M0), this));
   for (auto Reg : AMDGPU::VGPR_HI16RegClass)
     RegPressureIgnoredUnits.set(*MCRegUnitIterator(Reg, this));
 
@@ -2091,7 +2092,8 @@
     DefIdx = V->def;
   } else {
     // Find last def.
-    for (MCRegUnitIterator Units(Reg, this); Units.isValid(); ++Units) {
+    for (MCRegUnitIterator Units(Reg.asMCReg(), this); Units.isValid();
+         ++Units) {
       LiveRange &LR = LIS->getRegUnit(*Units);
       if (VNInfo *V = LR.getVNInfoAt(UseIdx)) {
         if (!DefIdx.isValid() ||
diff --git a/llvm/lib/Target/AMDGPU/SIWholeQuadMode.cpp b/llvm/lib/Target/AMDGPU/SIWholeQuadMode.cpp
--- a/llvm/lib/Target/AMDGPU/SIWholeQuadMode.cpp
+++ b/llvm/lib/Target/AMDGPU/SIWholeQuadMode.cpp
@@ -353,7 +353,8 @@
       if (Reg == AMDGPU::EXEC || Reg == AMDGPU::EXEC_LO)
         continue;
 
-      for (MCRegUnitIterator RegUnit(Reg, TRI); RegUnit.isValid(); ++RegUnit) {
+      for (MCRegUnitIterator RegUnit(Reg.asMCReg(), TRI); RegUnit.isValid();
+           ++RegUnit) {
         LiveRange &LR = LIS->getRegUnit(*RegUnit);
         const VNInfo *Value = LR.Query(LIS->getInstructionIndex(MI)).valueIn();
         if (!Value)
@@ -630,7 +631,8 @@
   if (!SaveSCC)
     return PreferLast ? Last : First;
 
-  LiveRange &LR = LIS->getRegUnit(*MCRegUnitIterator(AMDGPU::SCC, TRI));
+  LiveRange &LR =
+      LIS->getRegUnit(*MCRegUnitIterator(MCRegister::from(AMDGPU::SCC), TRI));
   auto MBBE = MBB.end();
   SlotIndex FirstIdx = First != MBBE ? LIS->getInstructionIndex(*First)
                                      : LIS->getMBBEndIdx(&MBB);
@@ -1060,7 +1062,7 @@
   // Physical registers like SCC aren't tracked by default anyway, so just
   // removing the ranges we computed is the simplest option for maintaining
   // the analysis results.
-  LIS->removeRegUnit(*MCRegUnitIterator(AMDGPU::SCC, TRI));
+  LIS->removeRegUnit(*MCRegUnitIterator(MCRegister::from(AMDGPU::SCC), TRI));
 
   return true;
 }
diff --git a/llvm/lib/Target/PowerPC/PPCVSXFMAMutate.cpp b/llvm/lib/Target/PowerPC/PPCVSXFMAMutate.cpp
--- a/llvm/lib/Target/PowerPC/PPCVSXFMAMutate.cpp
+++ b/llvm/lib/Target/PowerPC/PPCVSXFMAMutate.cpp
@@ -315,9 +315,9 @@
         // Extend the live interval of the addend source (it might end at the
         // copy to be removed, or somewhere in between there and here). This
         // is necessary only if it is a physical register.
-        if (!Register::isVirtualRegister(AddendSrcReg))
-          for (MCRegUnitIterator Units(AddendSrcReg, TRI); Units.isValid();
-               ++Units) {
+        if (!AddendSrcReg.isVirtual())
+          for (MCRegUnitIterator Units(AddendSrcReg.asMCReg(), TRI);
+               Units.isValid(); ++Units) {
             unsigned Unit = *Units;
 
             LiveRange &AddendSrcRange = LIS->getRegUnit(Unit);
diff --git a/llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp b/llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp
--- a/llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp
+++ b/llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp
@@ -999,7 +999,7 @@
   unsigned Opcode = MI.getOpcode();
 
   // Check CC liveness if new instruction introduces a dead def of CC.
-  MCRegUnitIterator CCUnit(SystemZ::CC, TRI);
+  MCRegUnitIterator CCUnit(MCRegister::from(SystemZ::CC), TRI);
   SlotIndex MISlot = SlotIndex();
   LiveRange *CCLiveRange = nullptr;
   bool CCLiveAtMI = true;