diff --git a/include/llvm/CodeGen/MachineRegisterInfo.h b/include/llvm/CodeGen/MachineRegisterInfo.h
index 3272fbd78ff..5a82caa9acd 100644
--- a/include/llvm/CodeGen/MachineRegisterInfo.h
+++ b/include/llvm/CodeGen/MachineRegisterInfo.h
@@ -336,7 +336,7 @@ public:
   bool isPhysRegOrOverlapUsed(unsigned Reg) const {
     if (UsedPhysRegMask.test(Reg))
       return true;
-    for (const uint16_t *AI = TRI->getOverlaps(Reg); *AI; ++AI)
+    for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI)
       if (UsedPhysRegs.test(*AI))
         return true;
     return false;
diff --git a/include/llvm/MC/MCRegisterInfo.h b/include/llvm/MC/MCRegisterInfo.h
index a2ec7bc9c4f..956f5e6aa95 100644
--- a/include/llvm/MC/MCRegisterInfo.h
+++ b/include/llvm/MC/MCRegisterInfo.h
@@ -361,12 +361,7 @@ public:
   /// getMatchingSuperReg - Return a super-register of the specified register
   /// Reg so its sub-register of index SubIdx is Reg.
   unsigned getMatchingSuperReg(unsigned Reg, unsigned SubIdx,
-                               const MCRegisterClass *RC) const {
-    for (const uint16_t *SRs = getSuperRegisters(Reg); unsigned SR = *SRs;++SRs)
-      if (Reg == getSubReg(SR, SubIdx) && RC->contains(SR))
-        return SR;
-    return 0;
-  }
+                               const MCRegisterClass *RC) const;
 
   /// getSubRegIndex - For a given register pair, return the sub-register index
   /// if the second register is a sub-register of the first. Return zero
@@ -494,6 +489,15 @@ public:
   {}
 };
 
+inline
+unsigned MCRegisterInfo::getMatchingSuperReg(unsigned Reg, unsigned SubIdx,
+                                             const MCRegisterClass *RC) const {
+    for (MCSuperRegIterator Supers(Reg, this); Supers.isValid(); ++Supers)
+      if (Reg == getSubReg(*Supers, SubIdx) && RC->contains(*Supers))
+        return *Supers;
+    return 0;
+}
+
 //===----------------------------------------------------------------------===//
 //                               Register Units
 //===----------------------------------------------------------------------===//
diff --git a/lib/CodeGen/AggressiveAntiDepBreaker.cpp b/lib/CodeGen/AggressiveAntiDepBreaker.cpp
index 6348fdd71fd..766336ac8a0 100644
--- a/lib/CodeGen/AggressiveAntiDepBreaker.cpp
+++ b/lib/CodeGen/AggressiveAntiDepBreaker.cpp
@@ -157,8 +157,8 @@ void AggressiveAntiDepBreaker::StartBlock(MachineBasicBlock *BB) {
     // In a return block, examine the function live-out regs.
     for (MachineRegisterInfo::liveout_iterator I = MRI.liveout_begin(),
          E = MRI.liveout_end(); I != E; ++I) {
-      for (const uint16_t *Alias = TRI->getOverlaps(*I);
-           unsigned Reg = *Alias; ++Alias) {
+      for (MCRegAliasIterator AI(*I, TRI, true); AI.isValid(); ++AI) {
+        unsigned Reg = *AI;
         State->UnionGroups(Reg, 0);
         KillIndices[Reg] = BB->size();
         DefIndices[Reg] = ~0u;
@@ -173,8 +173,8 @@ void AggressiveAntiDepBreaker::StartBlock(MachineBasicBlock *BB) {
          SE = BB->succ_end(); SI != SE; ++SI)
     for (MachineBasicBlock::livein_iterator I = (*SI)->livein_begin(),
            E = (*SI)->livein_end(); I != E; ++I) {
-      for (const uint16_t *Alias = TRI->getOverlaps(*I);
-           unsigned Reg = *Alias; ++Alias) {
+      for (MCRegAliasIterator AI(*I, TRI, true); AI.isValid(); ++AI) {
+        unsigned Reg = *AI;
         State->UnionGroups(Reg, 0);
         KillIndices[Reg] = BB->size();
         DefIndices[Reg] = ~0u;
@@ -189,8 +189,8 @@ void AggressiveAntiDepBreaker::StartBlock(MachineBasicBlock *BB) {
   for (const uint16_t *I = TRI->getCalleeSavedRegs(&MF); *I; ++I) {
     unsigned Reg = *I;
     if (!IsReturnBlock && !Pristine.test(Reg)) continue;
-    for (const uint16_t *Alias = TRI->getOverlaps(Reg);
-         unsigned AliasReg = *Alias; ++Alias) {
+    for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI) {
+      unsigned AliasReg = *AI;
       State->UnionGroups(AliasReg, 0);
       KillIndices[AliasReg] = BB->size();
       DefIndices[AliasReg] = ~0u;
@@ -265,10 +265,8 @@ void AggressiveAntiDepBreaker::GetPassthruRegs(MachineInstr *MI,
         IsImplicitDefUse(MI, MO)) {
       const unsigned Reg = MO.getReg();
       PassthruRegs.insert(Reg);
-      for (const uint16_t *Subreg = TRI->getSubRegisters(Reg);
-           *Subreg; ++Subreg) {
-        PassthruRegs.insert(*Subreg);
-      }
+      for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs)
+        PassthruRegs.insert(*SubRegs);
     }
   }
 }
@@ -333,9 +331,8 @@ void AggressiveAntiDepBreaker::HandleLastUse(unsigned Reg, unsigned KillIdx,
     DEBUG(dbgs() << "->g" << State->GetGroup(Reg) << tag);
   }
   // Repeat for subregisters.
-  for (const uint16_t *Subreg = TRI->getSubRegisters(Reg);
-       *Subreg; ++Subreg) {
-    unsigned SubregReg = *Subreg;
+  for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs) {
+    unsigned SubregReg = *SubRegs;
     if (!State->IsLive(SubregReg)) {
       KillIndices[SubregReg] = KillIdx;
       DefIndices[SubregReg] = ~0u;
@@ -392,8 +389,8 @@ void AggressiveAntiDepBreaker::PrescanInstruction(MachineInstr *MI,
 
     // Any aliased that are live at this point are completely or
     // partially defined here, so group those aliases with Reg.
-    for (const uint16_t *Alias = TRI->getAliasSet(Reg); *Alias; ++Alias) {
-      unsigned AliasReg = *Alias;
+    for (MCRegAliasIterator AI(Reg, TRI, false); AI.isValid(); ++AI) {
+      unsigned AliasReg = *AI;
       if (State->IsLive(AliasReg)) {
         State->UnionGroups(Reg, AliasReg);
         DEBUG(dbgs() << "->g" << State->GetGroup(Reg) << "(via " <<
@@ -423,9 +420,8 @@ void AggressiveAntiDepBreaker::PrescanInstruction(MachineInstr *MI,
       continue;
 
     // Update def for Reg and aliases.
-    for (const uint16_t *Alias = TRI->getOverlaps(Reg);
-         unsigned AliasReg = *Alias; ++Alias)
-      DefIndices[AliasReg] = Count;
+    for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI)
+      DefIndices[*AI] = Count;
   }
 }
 
@@ -678,9 +674,8 @@ bool AggressiveAntiDepBreaker::FindSuitableFreeRegisters(
         goto next_super_reg;
       } else {
         bool found = false;
-        for (const uint16_t *Alias = TRI->getAliasSet(NewReg);
-             *Alias; ++Alias) {
-          unsigned AliasReg = *Alias;
+        for (MCRegAliasIterator AI(NewReg, TRI, false); AI.isValid(); ++AI) {
+          unsigned AliasReg = *AI;
           if (State->IsLive(AliasReg) ||
               (KillIndices[Reg] > DefIndices[AliasReg])) {
             DEBUG(dbgs() << "(alias " << TRI->getName(AliasReg) << " live)");
diff --git a/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index ae498dd27d3..eeacc43c097 100644
--- a/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -796,8 +796,8 @@ void AsmPrinter::EmitDwarfRegOp(const MachineLocation &MLoc) const {
   const TargetRegisterInfo *TRI = TM.getRegisterInfo();
   int Reg = TRI->getDwarfRegNum(MLoc.getReg(), false);
 
-  for (const uint16_t *SR = TRI->getSuperRegisters(MLoc.getReg());
-       *SR && Reg < 0; ++SR) {
+  for (MCSuperRegIterator SR(MLoc.getReg(), TRI); SR.isValid() && Reg < 0;
+       ++SR) {
     Reg = TRI->getDwarfRegNum(*SR, false);
     // FIXME: Get the bit range this register uses of the superregister
     // so that we can produce a DW_OP_bit_piece
diff --git a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index fe49730bccd..f24067d6b8c 100644
--- a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -1309,8 +1309,9 @@ void DwarfDebug::beginFunction(const MachineFunction *MF) {
                MOE = MI->operands_end(); MOI != MOE; ++MOI) {
           if (!MOI->isReg() || !MOI->isDef() || !MOI->getReg())
             continue;
-          for (const uint16_t *AI = TRI->getOverlaps(MOI->getReg());
-               unsigned Reg = *AI; ++AI) {
+          for (MCRegAliasIterator AI(MOI->getReg(), TRI, true);
+               AI.isValid(); ++AI) {
+            unsigned Reg = *AI;
             const MDNode *Var = LiveUserVar[Reg];
             if (!Var)
               continue;
diff --git a/lib/CodeGen/BranchFolding.cpp b/lib/CodeGen/BranchFolding.cpp
index 971552144f7..edfebe1b6c7 100644
--- a/lib/CodeGen/BranchFolding.cpp
+++ b/lib/CodeGen/BranchFolding.cpp
@@ -137,9 +137,8 @@ bool BranchFolder::OptimizeImpDefsBlock(MachineBasicBlock *MBB) {
       break;
     unsigned Reg = I->getOperand(0).getReg();
     ImpDefRegs.insert(Reg);
-    for (const uint16_t *SubRegs = TRI->getSubRegisters(Reg);
-         unsigned SubReg = *SubRegs; ++SubRegs)
-      ImpDefRegs.insert(SubReg);
+    for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs)
+      ImpDefRegs.insert(*SubRegs);
     ++I;
   }
   if (ImpDefRegs.empty())
@@ -1557,8 +1556,8 @@ MachineBasicBlock::iterator findHoistingInsertPosAndDeps(MachineBasicBlock *MBB,
     } else {
       if (Uses.count(Reg)) {
         Uses.erase(Reg);
-        for (const uint16_t *SR = TRI->getSubRegisters(Reg); *SR; ++SR)
-          Uses.erase(*SR); // Use getSubRegisters to be conservative
+        for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs)
+          Uses.erase(*SubRegs); // Use sub-registers to be conservative
       }
       for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI)
         Defs.insert(*AI);
@@ -1688,8 +1687,8 @@ bool BranchFolder::HoistCommonCodeInSuccs(MachineBasicBlock *MBB) {
       unsigned Reg = MO.getReg();
       if (!Reg || !LocalDefsSet.count(Reg))
         continue;
-      for (const uint16_t *OR = TRI->getOverlaps(Reg); *OR; ++OR)
-        LocalDefsSet.erase(*OR);
+      for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI)
+        LocalDefsSet.erase(*AI);
     }
 
     // Track local defs so we can update liveins.
@@ -1701,8 +1700,8 @@ bool BranchFolder::HoistCommonCodeInSuccs(MachineBasicBlock *MBB) {
       if (!Reg)
         continue;
       LocalDefs.push_back(Reg);
-      for (const uint16_t *OR = TRI->getOverlaps(Reg); *OR; ++OR)
-        LocalDefsSet.insert(*OR);
+      for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI)
+        LocalDefsSet.insert(*AI);
     }
 
     HasDups = true;
diff --git a/lib/CodeGen/CallingConvLower.cpp b/lib/CodeGen/CallingConvLower.cpp
index 2b7dfdbe41a..b2c976b2a5e 100644
--- a/lib/CodeGen/CallingConvLower.cpp
+++ b/lib/CodeGen/CallingConvLower.cpp
@@ -58,9 +58,8 @@ void CCState::HandleByVal(unsigned ValNo, MVT ValVT,
 
 /// MarkAllocated - Mark a register and all of its aliases as allocated.
 void CCState::MarkAllocated(unsigned Reg) {
-  for (const uint16_t *Alias = TRI.getOverlaps(Reg);
-       unsigned Reg = *Alias; ++Alias)
-    UsedRegs[Reg/32] |= 1 << (Reg&31);
+  for (MCRegAliasIterator AI(Reg, &TRI, true); AI.isValid(); ++AI)
+    UsedRegs[*AI/32] |= 1 << (*AI&31);
 }
 
 /// AnalyzeFormalArguments - Analyze an array of argument values,
diff --git a/lib/CodeGen/CriticalAntiDepBreaker.cpp b/lib/CodeGen/CriticalAntiDepBreaker.cpp
index 0cb6480da07..9cec59030a0 100644
--- a/lib/CodeGen/CriticalAntiDepBreaker.cpp
+++ b/lib/CodeGen/CriticalAntiDepBreaker.cpp
@@ -200,11 +200,11 @@ void CriticalAntiDepBreaker::PrescanInstruction(MachineInstr *MI) {
       Classes[Reg] = reinterpret_cast<TargetRegisterClass *>(-1);
 
     // Now check for aliases.
-    for (const uint16_t *Alias = TRI->getAliasSet(Reg); *Alias; ++Alias) {
+    for (MCRegAliasIterator AI(Reg, TRI, false); AI.isValid(); ++AI) {
       // If an alias of the reg is used during the live range, give up.
       // Note that this allows us to skip checking if AntiDepReg
       // overlaps with any of the aliases, among other things.
-      unsigned AliasReg = *Alias;
+      unsigned AliasReg = *AI;
       if (Classes[AliasReg]) {
         Classes[AliasReg] = reinterpret_cast<TargetRegisterClass *>(-1);
         Classes[Reg] = reinterpret_cast<TargetRegisterClass *>(-1);
@@ -218,9 +218,8 @@ void CriticalAntiDepBreaker::PrescanInstruction(MachineInstr *MI) {
     if (MO.isUse() && Special) {
       if (!KeepRegs.test(Reg)) {
         KeepRegs.set(Reg);
-        for (const uint16_t *Subreg = TRI->getSubRegisters(Reg);
-             *Subreg; ++Subreg)
-          KeepRegs.set(*Subreg);
+        for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs)
+          KeepRegs.set(*SubRegs);
       }
     }
   }
@@ -264,9 +263,8 @@ void CriticalAntiDepBreaker::ScanInstruction(MachineInstr *MI,
       Classes[Reg] = 0;
       RegRefs.erase(Reg);
       // Repeat, for all subregs.
-      for (const uint16_t *Subreg = TRI->getSubRegisters(Reg);
-           *Subreg; ++Subreg) {
-        unsigned SubregReg = *Subreg;
+      for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs) {
+        unsigned SubregReg = *SubRegs;
         DefIndices[SubregReg] = Count;
         KillIndices[SubregReg] = ~0u;
         KeepRegs.reset(SubregReg);
@@ -274,11 +272,8 @@ void CriticalAntiDepBreaker::ScanInstruction(MachineInstr *MI,
         RegRefs.erase(SubregReg);
       }
       // Conservatively mark super-registers as unusable.
-      for (const uint16_t *Super = TRI->getSuperRegisters(Reg);
-           *Super; ++Super) {
-        unsigned SuperReg = *Super;
-        Classes[SuperReg] = reinterpret_cast<TargetRegisterClass *>(-1);
-      }
+      for (MCSuperRegIterator SR(Reg, TRI); SR.isValid(); ++SR)
+        Classes[*SR] = reinterpret_cast<TargetRegisterClass *>(-1);
     }
   }
   for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
@@ -310,8 +305,8 @@ void CriticalAntiDepBreaker::ScanInstruction(MachineInstr *MI,
                "Kill and Def maps aren't consistent for Reg!");
     }
     // Repeat, for all aliases.
-    for (const uint16_t *Alias = TRI->getAliasSet(Reg); *Alias; ++Alias) {
-      unsigned AliasReg = *Alias;
+    for (MCRegAliasIterator AI(Reg, TRI, false); AI.isValid(); ++AI) {
+      unsigned AliasReg = *AI;
       if (KillIndices[AliasReg] == ~0u) {
         KillIndices[AliasReg] = Count;
         DefIndices[AliasReg] = ~0u;
diff --git a/lib/CodeGen/DeadMachineInstructionElim.cpp b/lib/CodeGen/DeadMachineInstructionElim.cpp
index 69bd1c24ebc..b4394e8d56e 100644
--- a/lib/CodeGen/DeadMachineInstructionElim.cpp
+++ b/lib/CodeGen/DeadMachineInstructionElim.cpp
@@ -171,9 +171,8 @@ bool DeadMachineInstructionElim::runOnMachineFunction(MachineFunction &MF) {
             // Check the subreg set, not the alias set, because a def
             // of a super-register may still be partially live after
             // this def.
-            for (const uint16_t *SubRegs = TRI->getSubRegisters(Reg);
-                 *SubRegs; ++SubRegs)
-              LivePhysRegs.reset(*SubRegs);
+            for (MCSubRegIterator SR(Reg, TRI); SR.isValid(); ++SR)
+              LivePhysRegs.reset(*SR);
           }
         } else if (MO.isRegMask()) {
           // Register mask of preserved registers. All clobbers are dead.
diff --git a/lib/CodeGen/ExecutionDepsFix.cpp b/lib/CodeGen/ExecutionDepsFix.cpp
index a48c5400abc..9237f7efc29 100644
--- a/lib/CodeGen/ExecutionDepsFix.cpp
+++ b/lib/CodeGen/ExecutionDepsFix.cpp
@@ -666,7 +666,8 @@ bool ExeDepsFix::runOnMachineFunction(MachineFunction &mf) {
     // or -1.
     AliasMap.resize(TRI->getNumRegs(), -1);
     for (unsigned i = 0, e = RC->getNumRegs(); i != e; ++i)
-      for (const uint16_t *AI = TRI->getOverlaps(RC->getRegister(i)); *AI; ++AI)
+      for (MCRegAliasIterator AI(RC->getRegister(i), TRI, true);
+           AI.isValid(); ++AI)
         AliasMap[*AI] = i;
   }
 
diff --git a/lib/CodeGen/IfConversion.cpp b/lib/CodeGen/IfConversion.cpp
index 00ea3c599f6..5bfd5499b43 100644
--- a/lib/CodeGen/IfConversion.cpp
+++ b/lib/CodeGen/IfConversion.cpp
@@ -962,9 +962,8 @@ static void InitPredRedefs(MachineBasicBlock *BB, SmallSet<unsigned,4> &Redefs,
          E = BB->livein_end(); I != E; ++I) {
     unsigned Reg = *I;
     Redefs.insert(Reg);
-    for (const uint16_t *Subreg = TRI->getSubRegisters(Reg);
-         *Subreg; ++Subreg)
-      Redefs.insert(*Subreg);
+    for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs)
+      Redefs.insert(*SubRegs);
   }
 }
 
@@ -983,8 +982,8 @@ static void UpdatePredRedefs(MachineInstr *MI, SmallSet<unsigned,4> &Redefs,
       Defs.push_back(Reg);
     else if (MO.isKill()) {
       Redefs.erase(Reg);
-      for (const uint16_t *SR = TRI->getSubRegisters(Reg); *SR; ++SR)
-        Redefs.erase(*SR);
+      for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs)
+        Redefs.erase(*SubRegs);
     }
   }
   for (unsigned i = 0, e = Defs.size(); i != e; ++i) {
@@ -997,8 +996,8 @@ static void UpdatePredRedefs(MachineInstr *MI, SmallSet<unsigned,4> &Redefs,
                                               false/*IsDead*/,true/*IsUndef*/));
     } else {
       Redefs.insert(Reg);
-      for (const uint16_t *SR = TRI->getSubRegisters(Reg); *SR; ++SR)
-        Redefs.insert(*SR);
+      for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs)
+        Redefs.insert(*SubRegs);
     }
   }
 }
@@ -1336,8 +1335,8 @@ bool IfConverter::IfConvertDiamond(BBInfo &BBI, IfcvtKind Kind,
           // These are defined before ctrl flow reach the 'false' instructions.
           // They cannot be modified by the 'true' instructions.
           ExtUses.insert(Reg);
-          for (const uint16_t *SR = TRI->getSubRegisters(Reg); *SR; ++SR)
-            ExtUses.insert(*SR);
+          for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs)
+            ExtUses.insert(*SubRegs);
         }
       }
 
@@ -1345,8 +1344,8 @@ bool IfConverter::IfConvertDiamond(BBInfo &BBI, IfcvtKind Kind,
         unsigned Reg = Defs[i];
         if (!ExtUses.count(Reg)) {
           RedefsByFalse.insert(Reg);
-          for (const uint16_t *SR = TRI->getSubRegisters(Reg); *SR; ++SR)
-            RedefsByFalse.insert(*SR);
+          for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs)
+            RedefsByFalse.insert(*SubRegs);
         }
       }
     }
diff --git a/lib/CodeGen/InterferenceCache.cpp b/lib/CodeGen/InterferenceCache.cpp
index 8368b58880a..9b6d496b060 100644
--- a/lib/CodeGen/InterferenceCache.cpp
+++ b/lib/CodeGen/InterferenceCache.cpp
@@ -80,8 +80,8 @@ void InterferenceCache::Entry::reset(unsigned physReg,
   PhysReg = physReg;
   Blocks.resize(MF->getNumBlockIDs());
   Aliases.clear();
-  for (const uint16_t *AS = TRI->getOverlaps(PhysReg); *AS; ++AS) {
-    LiveIntervalUnion *LIU = LIUArray + *AS;
+  for (MCRegAliasIterator AI(PhysReg, TRI, true); AI.isValid(); ++AI) {
+    LiveIntervalUnion *LIU = LIUArray + *AI;
     Aliases.push_back(std::make_pair(LIU, LIU->getTag()));
   }
 
@@ -96,8 +96,8 @@ void InterferenceCache::Entry::reset(unsigned physReg,
 bool InterferenceCache::Entry::valid(LiveIntervalUnion *LIUArray,
                                      const TargetRegisterInfo *TRI) {
   unsigned i = 0, e = Aliases.size();
-  for (const uint16_t *AS = TRI->getOverlaps(PhysReg); *AS; ++AS, ++i) {
-    LiveIntervalUnion *LIU = LIUArray + *AS;
+  for (MCRegAliasIterator AI(PhysReg, TRI, true); AI.isValid(); ++AI, ++i) {
+    LiveIntervalUnion *LIU = LIUArray + *AI;
     if (i == e ||  Aliases[i].first != LIU)
       return false;
     if (LIU->changedSince(Aliases[i].second))
diff --git a/lib/CodeGen/LiveVariables.cpp b/lib/CodeGen/LiveVariables.cpp
index 5a0d97d132d..acf986ca610 100644
--- a/lib/CodeGen/LiveVariables.cpp
+++ b/lib/CodeGen/LiveVariables.cpp
@@ -192,8 +192,8 @@ MachineInstr *LiveVariables::FindLastPartialDef(unsigned Reg,
   unsigned LastDefReg = 0;
   unsigned LastDefDist = 0;
   MachineInstr *LastDef = NULL;
-  for (const uint16_t *SubRegs = TRI->getSubRegisters(Reg);
-       unsigned SubReg = *SubRegs; ++SubRegs) {
+  for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs) {
+    unsigned SubReg = *SubRegs;
     MachineInstr *Def = PhysRegDef[SubReg];
     if (!Def)
       continue;
@@ -216,9 +216,8 @@ MachineInstr *LiveVariables::FindLastPartialDef(unsigned Reg,
     unsigned DefReg = MO.getReg();
     if (TRI->isSubRegister(Reg, DefReg)) {
       PartDefRegs.insert(DefReg);
-      for (const uint16_t *SubRegs = TRI->getSubRegisters(DefReg);
-           unsigned SubReg = *SubRegs; ++SubRegs)
-        PartDefRegs.insert(SubReg);
+      for (MCSubRegIterator SubRegs(DefReg, TRI); SubRegs.isValid(); ++SubRegs)
+        PartDefRegs.insert(*SubRegs);
     }
   }
   return LastDef;
@@ -247,8 +246,8 @@ void LiveVariables::HandlePhysRegUse(unsigned Reg, MachineInstr *MI) {
                                                            true/*IsImp*/));
       PhysRegDef[Reg] = LastPartialDef;
       SmallSet<unsigned, 8> Processed;
-      for (const uint16_t *SubRegs = TRI->getSubRegisters(Reg);
-           unsigned SubReg = *SubRegs; ++SubRegs) {
+      for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs) {
+        unsigned SubReg = *SubRegs;
         if (Processed.count(SubReg))
           continue;
         if (PartDefRegs.count(SubReg))
@@ -259,7 +258,7 @@ void LiveVariables::HandlePhysRegUse(unsigned Reg, MachineInstr *MI) {
                                                              false/*IsDef*/,
                                                              true/*IsImp*/));
         PhysRegDef[SubReg] = LastPartialDef;
-        for (const uint16_t *SS = TRI->getSubRegisters(SubReg); *SS; ++SS)
+        for (MCSubRegIterator SS(SubReg, TRI); SS.isValid(); ++SS)
           Processed.insert(*SS);
       }
     }
@@ -271,9 +270,8 @@ void LiveVariables::HandlePhysRegUse(unsigned Reg, MachineInstr *MI) {
 
   // Remember this use.
   PhysRegUse[Reg]  = MI;
-  for (const uint16_t *SubRegs = TRI->getSubRegisters(Reg);
-       unsigned SubReg = *SubRegs; ++SubRegs)
-    PhysRegUse[SubReg] =  MI;
+  for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs)
+    PhysRegUse[*SubRegs] =  MI;
 }
 
 /// FindLastRefOrPartRef - Return the last reference or partial reference of
@@ -287,8 +285,8 @@ MachineInstr *LiveVariables::FindLastRefOrPartRef(unsigned Reg) {
   MachineInstr *LastRefOrPartRef = LastUse ? LastUse : LastDef;
   unsigned LastRefOrPartRefDist = DistanceMap[LastRefOrPartRef];
   unsigned LastPartDefDist = 0;
-  for (const uint16_t *SubRegs = TRI->getSubRegisters(Reg);
-       unsigned SubReg = *SubRegs; ++SubRegs) {
+  for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs) {
+    unsigned SubReg = *SubRegs;
     MachineInstr *Def = PhysRegDef[SubReg];
     if (Def && Def != LastDef) {
       // There was a def of this sub-register in between. This is a partial
@@ -336,8 +334,8 @@ bool LiveVariables::HandlePhysRegKill(unsigned Reg, MachineInstr *MI) {
   MachineInstr *LastPartDef = 0;
   unsigned LastPartDefDist = 0;
   SmallSet<unsigned, 8> PartUses;
-  for (const uint16_t *SubRegs = TRI->getSubRegisters(Reg);
-       unsigned SubReg = *SubRegs; ++SubRegs) {
+  for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs) {
+    unsigned SubReg = *SubRegs;
     MachineInstr *Def = PhysRegDef[SubReg];
     if (Def && Def != LastDef) {
       // There was a def of this sub-register in between. This is a partial
@@ -351,7 +349,7 @@ bool LiveVariables::HandlePhysRegKill(unsigned Reg, MachineInstr *MI) {
     }
     if (MachineInstr *Use = PhysRegUse[SubReg]) {
       PartUses.insert(SubReg);
-      for (const uint16_t *SS = TRI->getSubRegisters(SubReg); *SS; ++SS)
+      for (MCSubRegIterator SS(SubReg, TRI); SS.isValid(); ++SS)
         PartUses.insert(*SS);
       unsigned Dist = DistanceMap[Use];
       if (Dist > LastRefOrPartRefDist) {
@@ -367,8 +365,8 @@ bool LiveVariables::HandlePhysRegKill(unsigned Reg, MachineInstr *MI) {
     // EAX<dead>  = op  AL<imp-def>
     // That is, EAX def is dead but AL def extends pass it.
     PhysRegDef[Reg]->addRegisterDead(Reg, TRI, true);
-    for (const uint16_t *SubRegs = TRI->getSubRegisters(Reg);
-         unsigned SubReg = *SubRegs; ++SubRegs) {
+    for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs) {
+      unsigned SubReg = *SubRegs;
       if (!PartUses.count(SubReg))
         continue;
       bool NeedDef = true;
@@ -388,11 +386,10 @@ bool LiveVariables::HandlePhysRegKill(unsigned Reg, MachineInstr *MI) {
       else {
         LastRefOrPartRef->addRegisterKilled(SubReg, TRI, true);
         PhysRegUse[SubReg] = LastRefOrPartRef;
-        for (const uint16_t *SSRegs = TRI->getSubRegisters(SubReg);
-             unsigned SSReg = *SSRegs; ++SSRegs)
-          PhysRegUse[SSReg] = LastRefOrPartRef;
+        for (MCSubRegIterator SS(SubReg, TRI); SS.isValid(); ++SS)
+          PhysRegUse[*SS] = LastRefOrPartRef;
       }
-      for (const uint16_t *SS = TRI->getSubRegisters(SubReg); *SS; ++SS)
+      for (MCSubRegIterator SS(SubReg, TRI); SS.isValid(); ++SS)
         PartUses.erase(*SS);
     }
   } else if (LastRefOrPartRef == PhysRegDef[Reg] && LastRefOrPartRef != MI) {
@@ -434,7 +431,7 @@ void LiveVariables::HandleRegMask(const MachineOperand &MO) {
     // Kill the largest clobbered super-register.
     // This avoids needless implicit operands.
     unsigned Super = Reg;
-    for (const uint16_t *SR = TRI->getSuperRegisters(Reg); *SR; ++SR)
+    for (MCSuperRegIterator SR(Reg, TRI); SR.isValid(); ++SR)
       if ((PhysRegDef[*SR] || PhysRegUse[*SR]) && MO.clobbersPhysReg(*SR))
         Super = *SR;
     HandlePhysRegKill(Super, 0);
@@ -447,11 +444,11 @@ void LiveVariables::HandlePhysRegDef(unsigned Reg, MachineInstr *MI,
   SmallSet<unsigned, 32> Live;
   if (PhysRegDef[Reg] || PhysRegUse[Reg]) {
     Live.insert(Reg);
-    for (const uint16_t *SS = TRI->getSubRegisters(Reg); *SS; ++SS)
-      Live.insert(*SS);
+    for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs)
+      Live.insert(*SubRegs);
   } else {
-    for (const uint16_t *SubRegs = TRI->getSubRegisters(Reg);
-         unsigned SubReg = *SubRegs; ++SubRegs) {
+    for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs) {
+      unsigned SubReg = *SubRegs;
       // If a register isn't itself defined, but all parts that make up of it
       // are defined, then consider it also defined.
       // e.g.
@@ -462,7 +459,7 @@ void LiveVariables::HandlePhysRegDef(unsigned Reg, MachineInstr *MI,
         continue;
       if (PhysRegDef[SubReg] || PhysRegUse[SubReg]) {
         Live.insert(SubReg);
-        for (const uint16_t *SS = TRI->getSubRegisters(SubReg); *SS; ++SS)
+        for (MCSubRegIterator SS(SubReg, TRI); SS.isValid(); ++SS)
           Live.insert(*SS);
       }
     }
@@ -472,8 +469,8 @@ void LiveVariables::HandlePhysRegDef(unsigned Reg, MachineInstr *MI,
   // is referenced.
   HandlePhysRegKill(Reg, MI);
   // Only some of the sub-registers are used.
-  for (const uint16_t *SubRegs = TRI->getSubRegisters(Reg);
-       unsigned SubReg = *SubRegs; ++SubRegs) {
+  for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs) {
+    unsigned SubReg = *SubRegs;
     if (!Live.count(SubReg))
       // Skip if this sub-register isn't defined.
       continue;
@@ -491,8 +488,8 @@ void LiveVariables::UpdatePhysRegDefs(MachineInstr *MI,
     Defs.pop_back();
     PhysRegDef[Reg]  = MI;
     PhysRegUse[Reg]  = NULL;
-    for (const uint16_t *SubRegs = TRI->getSubRegisters(Reg);
-         unsigned SubReg = *SubRegs; ++SubRegs) {
+    for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs) {
+      unsigned SubReg = *SubRegs;
       PhysRegDef[SubReg]  = MI;
       PhysRegUse[SubReg]  = NULL;
     }
diff --git a/lib/CodeGen/MachineCopyPropagation.cpp b/lib/CodeGen/MachineCopyPropagation.cpp
index db98cb9eeb0..bac3aa2c155 100644
--- a/lib/CodeGen/MachineCopyPropagation.cpp
+++ b/lib/CodeGen/MachineCopyPropagation.cpp
@@ -71,7 +71,7 @@ MachineCopyPropagation::SourceNoLongerAvailable(unsigned Reg,
         unsigned MappedDef = *I;
         // Source of copy is no longer available for propagation.
         if (AvailCopyMap.erase(MappedDef)) {
-          for (const uint16_t *SR = TRI->getSubRegisters(MappedDef); *SR; ++SR)
+          for (MCSubRegIterator SR(MappedDef, TRI); SR.isValid(); ++SR)
             AvailCopyMap.erase(*SR);
         }
       }
@@ -196,13 +196,13 @@ bool MachineCopyPropagation::CopyPropagateBlock(MachineBasicBlock &MBB) {
 
       // Remember Def is defined by the copy.
       // ... Make sure to clear the def maps of aliases first.
-      for (const uint16_t *AS = TRI->getAliasSet(Def); *AS; ++AS) {
-        CopyMap.erase(*AS);
-        AvailCopyMap.erase(*AS);
+      for (MCRegAliasIterator AI(Def, TRI, false); AI.isValid(); ++AI) {
+        CopyMap.erase(*AI);
+        AvailCopyMap.erase(*AI);
       }
       CopyMap[Def] = MI;
       AvailCopyMap[Def] = MI;
-      for (const uint16_t *SR = TRI->getSubRegisters(Def); *SR; ++SR) {
+      for (MCSubRegIterator SR(Def, TRI); SR.isValid(); ++SR) {
         CopyMap[*SR] = MI;
         AvailCopyMap[*SR] = MI;
       }
diff --git a/lib/CodeGen/MachineInstr.cpp b/lib/CodeGen/MachineInstr.cpp
index 59b0e654a7b..2dfb299843c 100644
--- a/lib/CodeGen/MachineInstr.cpp
+++ b/lib/CodeGen/MachineInstr.cpp
@@ -1538,12 +1538,14 @@ void MachineInstr::print(raw_ostream &OS, const TargetMachine *TM) const {
         const MachineRegisterInfo &MRI = MF->getRegInfo();
         if (MRI.use_empty(Reg) && !MRI.isLiveOut(Reg)) {
           bool HasAliasLive = false;
-          for (const uint16_t *Alias = TM->getRegisterInfo()->getAliasSet(Reg);
-               unsigned AliasReg = *Alias; ++Alias)
+          for (MCRegAliasIterator AI(Reg, TM->getRegisterInfo(), true);
+               AI.isValid(); ++AI) {
+            unsigned AliasReg = *AI;
             if (!MRI.use_empty(AliasReg) || MRI.isLiveOut(AliasReg)) {
               HasAliasLive = true;
               break;
             }
+          }
           if (!HasAliasLive) {
             OmittedAnyCallClobbers = true;
             continue;
@@ -1675,7 +1677,8 @@ bool MachineInstr::addRegisterKilled(unsigned IncomingReg,
                                      const TargetRegisterInfo *RegInfo,
                                      bool AddIfNotFound) {
   bool isPhysReg = TargetRegisterInfo::isPhysicalRegister(IncomingReg);
-  bool hasAliases = isPhysReg && RegInfo->getAliasSet(IncomingReg);
+  bool hasAliases = isPhysReg &&
+    MCRegAliasIterator(IncomingReg, RegInfo, false).isValid();
   bool Found = false;
   SmallVector<unsigned,4> DeadOps;
   for (unsigned i = 0, e = getNumOperands(); i != e; ++i) {
@@ -1747,7 +1750,8 @@ bool MachineInstr::addRegisterDead(unsigned IncomingReg,
                                    const TargetRegisterInfo *RegInfo,
                                    bool AddIfNotFound) {
   bool isPhysReg = TargetRegisterInfo::isPhysicalRegister(IncomingReg);
-  bool hasAliases = isPhysReg && RegInfo->getAliasSet(IncomingReg);
+  bool hasAliases = isPhysReg &&
+    MCRegAliasIterator(IncomingReg, RegInfo, false).isValid();
   bool Found = false;
   SmallVector<unsigned,4> DeadOps;
   for (unsigned i = 0, e = getNumOperands(); i != e; ++i) {
diff --git a/lib/CodeGen/MachineInstrBundle.cpp b/lib/CodeGen/MachineInstrBundle.cpp
index 73489a7160b..b7de7bfb492 100644
--- a/lib/CodeGen/MachineInstrBundle.cpp
+++ b/lib/CodeGen/MachineInstrBundle.cpp
@@ -169,8 +169,8 @@ void llvm::finalizeBundle(MachineBasicBlock &MBB,
       }
 
       if (!MO.isDead()) {
-        for (const uint16_t *SubRegs = TRI->getSubRegisters(Reg);
-             unsigned SubReg = *SubRegs; ++SubRegs) {
+        for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs) {
+          unsigned SubReg = *SubRegs;
           if (LocalDefSet.insert(SubReg))
             LocalDefs.push_back(SubReg);
         }
diff --git a/lib/CodeGen/MachineLICM.cpp b/lib/CodeGen/MachineLICM.cpp
index 4cf37a3088c..efec481dab8 100644
--- a/lib/CodeGen/MachineLICM.cpp
+++ b/lib/CodeGen/MachineLICM.cpp
@@ -445,8 +445,8 @@ void MachineLICM::ProcessMI(MachineInstr *MI,
     }
 
     if (MO.isImplicit()) {
-      for (const uint16_t *AS = TRI->getOverlaps(Reg); *AS; ++AS)
-        PhysRegClobbers.set(*AS);
+      for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI)
+        PhysRegClobbers.set(*AI);
       if (!MO.isDead())
         // Non-dead implicit def? This cannot be hoisted.
         RuledOut = true;
@@ -465,7 +465,7 @@ void MachineLICM::ProcessMI(MachineInstr *MI,
     // If we have already seen another instruction that defines the same
     // register, then this is not safe.  Two defs is indicated by setting a
     // PhysRegClobbers bit.
-    for (const uint16_t *AS = TRI->getOverlaps(Reg); *AS; ++AS) {
+    for (MCRegAliasIterator AS(Reg, TRI, true); AS.isValid(); ++AS) {
       if (PhysRegDefs.test(*AS))
         PhysRegClobbers.set(*AS);
       if (PhysRegClobbers.test(*AS))
@@ -517,8 +517,8 @@ void MachineLICM::HoistRegionPostRA() {
     for (MachineBasicBlock::livein_iterator I = BB->livein_begin(),
            E = BB->livein_end(); I != E; ++I) {
       unsigned Reg = *I;
-      for (const uint16_t *AS = TRI->getOverlaps(Reg); *AS; ++AS)
-        PhysRegDefs.set(*AS);
+      for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI)
+        PhysRegDefs.set(*AI);
     }
 
     SpeculationState = SpeculateUnknown;
@@ -540,8 +540,8 @@ void MachineLICM::HoistRegionPostRA() {
       unsigned Reg = MO.getReg();
       if (!Reg)
         continue;
-      for (const uint16_t *AS = TRI->getOverlaps(Reg); *AS; ++AS)
-        TermRegs.set(*AS);
+      for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI)
+        TermRegs.set(*AI);
     }
   }
 
diff --git a/lib/CodeGen/MachineRegisterInfo.cpp b/lib/CodeGen/MachineRegisterInfo.cpp
index 7ea151713a6..9c0d749a266 100644
--- a/lib/CodeGen/MachineRegisterInfo.cpp
+++ b/lib/CodeGen/MachineRegisterInfo.cpp
@@ -268,15 +268,15 @@ bool MachineRegisterInfo::isConstantPhysReg(unsigned PhysReg,
   assert(TargetRegisterInfo::isPhysicalRegister(PhysReg));
 
   // Check if any overlapping register is modified.
-  for (const uint16_t *R = TRI->getOverlaps(PhysReg); *R; ++R)
-    if (!def_empty(*R))
+  for (MCRegAliasIterator AI(PhysReg, TRI, true); AI.isValid(); ++AI)
+    if (!def_empty(*AI))
       return false;
 
   // Check if any overlapping register is allocatable so it may be used later.
   if (AllocatableRegs.empty())
     AllocatableRegs = TRI->getAllocatableSet(MF);
-  for (const uint16_t *R = TRI->getOverlaps(PhysReg); *R; ++R)
-    if (AllocatableRegs.test(*R))
+  for (MCRegAliasIterator AI(PhysReg, TRI, true); AI.isValid(); ++AI)
+    if (AllocatableRegs.test(*AI))
       return false;
   return true;
 }
diff --git a/lib/CodeGen/MachineVerifier.cpp b/lib/CodeGen/MachineVerifier.cpp
index 20dbe11bf9e..37d56f9d5dc 100644
--- a/lib/CodeGen/MachineVerifier.cpp
+++ b/lib/CodeGen/MachineVerifier.cpp
@@ -89,8 +89,8 @@ namespace {
     void addRegWithSubRegs(RegVector &RV, unsigned Reg) {
       RV.push_back(Reg);
       if (TargetRegisterInfo::isPhysicalRegister(Reg))
-        for (const uint16_t *R = TRI->getSubRegisters(Reg); *R; R++)
-          RV.push_back(*R);
+        for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs)
+          RV.push_back(*SubRegs);
     }
 
     struct BBInfo {
@@ -384,10 +384,10 @@ void MachineVerifier::visitMachineFunctionBefore() {
   // A sub-register of a reserved register is also reserved
   for (int Reg = regsReserved.find_first(); Reg>=0;
        Reg = regsReserved.find_next(Reg)) {
-    for (const uint16_t *Sub = TRI->getSubRegisters(Reg); *Sub; ++Sub) {
+    for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs) {
       // FIXME: This should probably be:
-      // assert(regsReserved.test(*Sub) && "Non-reserved sub-register");
-      regsReserved.set(*Sub);
+      // assert(regsReserved.test(*SubRegs) && "Non-reserved sub-register");
+      regsReserved.set(*SubRegs);
     }
   }
 
@@ -554,8 +554,8 @@ MachineVerifier::visitMachineBasicBlockBefore(const MachineBasicBlock *MBB) {
       continue;
     }
     regsLive.insert(*I);
-    for (const uint16_t *R = TRI->getSubRegisters(*I); *R; R++)
-      regsLive.insert(*R);
+    for (MCSubRegIterator SubRegs(*I, TRI); SubRegs.isValid(); ++SubRegs)
+      regsLive.insert(*SubRegs);
   }
   regsLiveInButUnused = regsLive;
 
@@ -564,8 +564,8 @@ MachineVerifier::visitMachineBasicBlockBefore(const MachineBasicBlock *MBB) {
   BitVector PR = MFI->getPristineRegs(MBB);
   for (int I = PR.find_first(); I>0; I = PR.find_next(I)) {
     regsLive.insert(I);
-    for (const uint16_t *R = TRI->getSubRegisters(I); *R; R++)
-      regsLive.insert(*R);
+    for (MCSubRegIterator SubRegs(I, TRI); SubRegs.isValid(); ++SubRegs)
+      regsLive.insert(*SubRegs);
   }
 
   regsKilled.clear();
diff --git a/lib/CodeGen/PostRASchedulerList.cpp b/lib/CodeGen/PostRASchedulerList.cpp
index 13feaec7d8d..cedb41273cd 100644
--- a/lib/CodeGen/PostRASchedulerList.cpp
+++ b/lib/CodeGen/PostRASchedulerList.cpp
@@ -427,9 +427,8 @@ void SchedulePostRATDList::StartBlockForKills(MachineBasicBlock *BB) {
       unsigned Reg = *I;
       LiveRegs.set(Reg);
       // Repeat, for all subregs.
-      for (const uint16_t *Subreg = TRI->getSubRegisters(Reg);
-           *Subreg; ++Subreg)
-        LiveRegs.set(*Subreg);
+      for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs)
+        LiveRegs.set(*SubRegs);
     }
   }
   else {
@@ -441,9 +440,8 @@ void SchedulePostRATDList::StartBlockForKills(MachineBasicBlock *BB) {
         unsigned Reg = *I;
         LiveRegs.set(Reg);
         // Repeat, for all subregs.
-        for (const uint16_t *Subreg = TRI->getSubRegisters(Reg);
-             *Subreg; ++Subreg)
-          LiveRegs.set(*Subreg);
+        for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs)
+          LiveRegs.set(*SubRegs);
       }
     }
   }
@@ -468,10 +466,9 @@ bool SchedulePostRATDList::ToggleKillFlag(MachineInstr *MI,
   MO.setIsKill(false);
   bool AllDead = true;
   const unsigned SuperReg = MO.getReg();
-  for (const uint16_t *Subreg = TRI->getSubRegisters(SuperReg);
-       *Subreg; ++Subreg) {
-    if (LiveRegs.test(*Subreg)) {
-      MI->addOperand(MachineOperand::CreateReg(*Subreg,
+  for (MCSubRegIterator SubRegs(SuperReg, TRI); SubRegs.isValid(); ++SubRegs) {
+    if (LiveRegs.test(*SubRegs)) {
+      MI->addOperand(MachineOperand::CreateReg(*SubRegs,
                                                true  /*IsDef*/,
                                                true  /*IsImp*/,
                                                false /*IsKill*/,
@@ -521,9 +518,8 @@ void SchedulePostRATDList::FixupKills(MachineBasicBlock *MBB) {
       LiveRegs.reset(Reg);
 
       // Repeat for all subregs.
-      for (const uint16_t *Subreg = TRI->getSubRegisters(Reg);
-           *Subreg; ++Subreg)
-        LiveRegs.reset(*Subreg);
+      for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs)
+        LiveRegs.reset(*SubRegs);
     }
 
     // Examine all used registers and set/clear kill flag. When a
@@ -540,9 +536,8 @@ void SchedulePostRATDList::FixupKills(MachineBasicBlock *MBB) {
       if (!killedRegs.test(Reg)) {
         kill = true;
         // A register is not killed if any subregs are live...
-        for (const uint16_t *Subreg = TRI->getSubRegisters(Reg);
-             *Subreg; ++Subreg) {
-          if (LiveRegs.test(*Subreg)) {
+        for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs) {
+          if (LiveRegs.test(*SubRegs)) {
             kill = false;
             break;
           }
@@ -574,9 +569,8 @@ void SchedulePostRATDList::FixupKills(MachineBasicBlock *MBB) {
 
       LiveRegs.set(Reg);
 
-      for (const uint16_t *Subreg = TRI->getSubRegisters(Reg);
-           *Subreg; ++Subreg)
-        LiveRegs.set(*Subreg);
+      for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs)
+        LiveRegs.set(*SubRegs);
     }
   }
 }
diff --git a/lib/CodeGen/ProcessImplicitDefs.cpp b/lib/CodeGen/ProcessImplicitDefs.cpp
index 1ad3479afb4..7735fa2bb12 100644
--- a/lib/CodeGen/ProcessImplicitDefs.cpp
+++ b/lib/CodeGen/ProcessImplicitDefs.cpp
@@ -113,8 +113,8 @@ bool ProcessImplicitDefs::runOnMachineFunction(MachineFunction &fn) {
         unsigned Reg = MI->getOperand(0).getReg();
         ImpDefRegs.insert(Reg);
         if (TargetRegisterInfo::isPhysicalRegister(Reg)) {
-          for (const uint16_t *SS = TRI->getSubRegisters(Reg); *SS; ++SS)
-            ImpDefRegs.insert(*SS);
+          for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs)
+            ImpDefRegs.insert(*SubRegs);
         }
         continue;
       }
diff --git a/lib/CodeGen/RegAllocBase.cpp b/lib/CodeGen/RegAllocBase.cpp
index b8d1d185e9f..a0ef9af411a 100644
--- a/lib/CodeGen/RegAllocBase.cpp
+++ b/lib/CodeGen/RegAllocBase.cpp
@@ -239,9 +239,9 @@ void RegAllocBase::allocatePhysRegs() {
 // physical register. Return the interfering register.
 unsigned RegAllocBase::checkPhysRegInterference(LiveInterval &VirtReg,
                                                 unsigned PhysReg) {
-  for (const uint16_t *AliasI = TRI->getOverlaps(PhysReg); *AliasI; ++AliasI)
-    if (query(VirtReg, *AliasI).checkInterference())
-      return *AliasI;
+  for (MCRegAliasIterator AI(PhysReg, TRI, true); AI.isValid(); ++AI)
+    if (query(VirtReg, *AI).checkInterference())
+      return *AI;
   return 0;
 }
 
diff --git a/lib/CodeGen/RegAllocBasic.cpp b/lib/CodeGen/RegAllocBasic.cpp
index 6b01ccb3094..83dbbf2c1db 100644
--- a/lib/CodeGen/RegAllocBasic.cpp
+++ b/lib/CodeGen/RegAllocBasic.cpp
@@ -204,8 +204,8 @@ bool RABasic::spillInterferences(LiveInterval &VirtReg, unsigned PhysReg,
   // either the union or live intervals.
   unsigned NumInterferences = 0;
   // Collect interferences assigned to any alias of the physical register.
-  for (const uint16_t *asI = TRI->getOverlaps(PhysReg); *asI; ++asI) {
-    LiveIntervalUnion::Query &QAlias = query(VirtReg, *asI);
+  for (MCRegAliasIterator AI(PhysReg, TRI, true); AI.isValid(); ++AI) {
+    LiveIntervalUnion::Query &QAlias = query(VirtReg, *AI);
     NumInterferences += QAlias.collectInterferingVRegs();
     if (QAlias.seenUnspillableVReg()) {
       return false;
@@ -216,8 +216,8 @@ bool RABasic::spillInterferences(LiveInterval &VirtReg, unsigned PhysReg,
   assert(NumInterferences > 0 && "expect interference");
 
   // Spill each interfering vreg allocated to PhysReg or an alias.
-  for (const uint16_t *AliasI = TRI->getOverlaps(PhysReg); *AliasI; ++AliasI)
-    spillReg(VirtReg, *AliasI, SplitVRegs);
+  for (MCRegAliasIterator AI(PhysReg, TRI, true); AI.isValid(); ++AI)
+    spillReg(VirtReg, *AI, SplitVRegs);
   return true;
 }
 
diff --git a/lib/CodeGen/RegAllocFast.cpp b/lib/CodeGen/RegAllocFast.cpp
index 8a22e632734..2cb16e00c83 100644
--- a/lib/CodeGen/RegAllocFast.cpp
+++ b/lib/CodeGen/RegAllocFast.cpp
@@ -354,8 +354,8 @@ void RAFast::usePhysReg(MachineOperand &MO) {
   }
 
   // Maybe a superregister is reserved?
-  for (const uint16_t *AS = TRI->getAliasSet(PhysReg);
-       unsigned Alias = *AS; ++AS) {
+  for (MCRegAliasIterator AI(PhysReg, TRI, false); AI.isValid(); ++AI) {
+    unsigned Alias = *AI;
     switch (PhysRegState[Alias]) {
     case regDisabled:
       break;
@@ -408,8 +408,8 @@ void RAFast::definePhysReg(MachineInstr *MI, unsigned PhysReg,
 
   // This is a disabled register, disable all aliases.
   PhysRegState[PhysReg] = NewState;
-  for (const uint16_t *AS = TRI->getAliasSet(PhysReg);
-       unsigned Alias = *AS; ++AS) {
+  for (MCRegAliasIterator AI(PhysReg, TRI, false); AI.isValid(); ++AI) {
+    unsigned Alias = *AI;
     switch (unsigned VirtReg = PhysRegState[Alias]) {
     case regDisabled:
       break;
@@ -456,8 +456,8 @@ unsigned RAFast::calcSpillCost(unsigned PhysReg) const {
   // This is a disabled register, add up cost of aliases.
   DEBUG(dbgs() << PrintReg(PhysReg, TRI) << " is disabled.\n");
   unsigned Cost = 0;
-  for (const uint16_t *AS = TRI->getAliasSet(PhysReg);
-       unsigned Alias = *AS; ++AS) {
+  for (MCRegAliasIterator AI(PhysReg, TRI, false); AI.isValid(); ++AI) {
+    unsigned Alias = *AI;
     if (UsedInInstr.test(Alias))
       return spillImpossible;
     switch (unsigned VirtReg = PhysRegState[Alias]) {
diff --git a/lib/CodeGen/RegAllocGreedy.cpp b/lib/CodeGen/RegAllocGreedy.cpp
index 426e0383786..bb00603f4d0 100644
--- a/lib/CodeGen/RegAllocGreedy.cpp
+++ b/lib/CodeGen/RegAllocGreedy.cpp
@@ -541,8 +541,8 @@ bool RAGreedy::canEvictInterference(LiveInterval &VirtReg, unsigned PhysReg,
     Cascade = NextCascade;
 
   EvictionCost Cost;
-  for (const uint16_t *AliasI = TRI->getOverlaps(PhysReg); *AliasI; ++AliasI) {
-    LiveIntervalUnion::Query &Q = query(VirtReg, *AliasI);
+  for (MCRegAliasIterator AI(PhysReg, TRI, true); AI.isValid(); ++AI) {
+    LiveIntervalUnion::Query &Q = query(VirtReg, *AI);
     // If there is 10 or more interferences, chances are one is heavier.
     if (Q.collectInterferingVRegs(10) >= 10)
       return false;
@@ -605,8 +605,8 @@ void RAGreedy::evictInterference(LiveInterval &VirtReg, unsigned PhysReg,
 
   DEBUG(dbgs() << "evicting " << PrintReg(PhysReg, TRI)
                << " interference: Cascade " << Cascade << '\n');
-  for (const uint16_t *AliasI = TRI->getOverlaps(PhysReg); *AliasI; ++AliasI) {
-    LiveIntervalUnion::Query &Q = query(VirtReg, *AliasI);
+  for (MCRegAliasIterator AI(PhysReg, TRI, true); AI.isValid(); ++AI) {
+    LiveIntervalUnion::Query &Q = query(VirtReg, *AI);
     assert(Q.seenAllInterferences() && "Didn't check all interfererences.");
     for (unsigned i = 0, e = Q.interferingVRegs().size(); i != e; ++i) {
       LiveInterval *Intf = Q.interferingVRegs()[i];
@@ -1358,7 +1358,7 @@ void RAGreedy::calcGapWeights(unsigned PhysReg,
   GapWeight.assign(NumGaps, 0.0f);
 
   // Add interference from each overlapping register.
-  for (const uint16_t *AI = TRI->getOverlaps(PhysReg); *AI; ++AI) {
+  for (MCRegAliasIterator AI(PhysReg, TRI, true); AI.isValid(); ++AI) {
     if (!query(const_cast<LiveInterval&>(SA->getParent()), *AI)
            .checkInterference())
       continue;
diff --git a/lib/CodeGen/RegAllocPBQP.cpp b/lib/CodeGen/RegAllocPBQP.cpp
index cfdfa59d6d4..4084ebb27a3 100644
--- a/lib/CodeGen/RegAllocPBQP.cpp
+++ b/lib/CodeGen/RegAllocPBQP.cpp
@@ -291,15 +291,11 @@ std::auto_ptr<PBQPRAProblem> PBQPBuilder::build(MachineFunction *mf,
       }
 
       // Also remove any aliases.
-      const uint16_t *aliasItr = tri->getAliasSet(preg);
-      if (aliasItr != 0) {
-        for (; *aliasItr != 0; ++aliasItr) {
-          VRAllowed::iterator eraseItr =
-            std::find(vrAllowed.begin(), vrAllowed.end(), *aliasItr);
-
-          if (eraseItr != vrAllowed.end()) {
-            vrAllowed.erase(eraseItr);
-          }
+      for (MCRegAliasIterator AI(preg, tri, false); AI.isValid(); ++AI) {
+        VRAllowed::iterator eraseItr =
+          std::find(vrAllowed.begin(), vrAllowed.end(), *AI);
+        if (eraseItr != vrAllowed.end()) {
+          vrAllowed.erase(eraseItr);
         }
       }
     }
diff --git a/lib/CodeGen/RegisterClassInfo.cpp b/lib/CodeGen/RegisterClassInfo.cpp
index 17165fa7266..d5b7f309db8 100644
--- a/lib/CodeGen/RegisterClassInfo.cpp
+++ b/lib/CodeGen/RegisterClassInfo.cpp
@@ -50,9 +50,8 @@ void RegisterClassInfo::runOnMachineFunction(const MachineFunction &mf) {
     CSRNum.clear();
     CSRNum.resize(TRI->getNumRegs(), 0);
     for (unsigned N = 0; unsigned Reg = CSR[N]; ++N)
-      for (const uint16_t *AS = TRI->getOverlaps(Reg);
-           unsigned Alias = *AS; ++AS)
-        CSRNum[Alias] = N + 1; // 0 means no CSR, 1 means CalleeSaved[0], ...
+      for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI)
+        CSRNum[*AI] = N + 1; // 0 means no CSR, 1 means CalleeSaved[0], ...
     Update = true;
   }
   CalleeSaved = CSR;
diff --git a/lib/CodeGen/RegisterCoalescer.cpp b/lib/CodeGen/RegisterCoalescer.cpp
index 2a535322198..0e154288ef0 100644
--- a/lib/CodeGen/RegisterCoalescer.cpp
+++ b/lib/CodeGen/RegisterCoalescer.cpp
@@ -470,7 +470,7 @@ bool RegisterCoalescer::adjustCopiesBackFrom(const CoalescerPair &CP,
   // If the IntB live range is assigned to a physical register, and if that
   // physreg has sub-registers, update their live intervals as well.
   if (TargetRegisterInfo::isPhysicalRegister(IntB.reg)) {
-    for (const uint16_t *SR = TRI->getSubRegisters(IntB.reg); *SR; ++SR) {
+    for (MCSubRegIterator SR(IntB.reg, TRI); SR.isValid(); ++SR) {
       if (!LIS->hasInterval(*SR))
         continue;
       LiveInterval &SRLI = LIS->getInterval(*SR);
@@ -1112,7 +1112,7 @@ bool RegisterCoalescer::joinReservedPhysReg(CoalescerPair &CP) {
 
   // Deny any overlapping intervals.  This depends on all the reserved
   // register live ranges to look like dead defs.
-  for (const uint16_t *AS = TRI->getOverlaps(CP.getDstReg()); *AS; ++AS) {
+  for (MCRegAliasIterator AS(CP.getDstReg(), TRI, true); AS.isValid(); ++AS) {
     if (!LIS->hasInterval(*AS)) {
       // Make sure at least DstReg itself exists before attempting a join.
       if (*AS == CP.getDstReg())
diff --git a/lib/CodeGen/RegisterPressure.cpp b/lib/CodeGen/RegisterPressure.cpp
index b1c1c513daa..ea2bb6b2664 100644
--- a/lib/CodeGen/RegisterPressure.cpp
+++ b/lib/CodeGen/RegisterPressure.cpp
@@ -271,10 +271,9 @@ void RegPressureTracker::closeRegion() {
 static bool hasRegAlias(unsigned Reg, SparseSet<unsigned> &Regs,
                         const TargetRegisterInfo *TRI) {
   assert(!TargetRegisterInfo::isVirtualRegister(Reg) && "only for physregs");
-  for (const uint16_t *Alias = TRI->getOverlaps(Reg); *Alias; ++Alias) {
-    if (Regs.count(*Alias))
+  for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI)
+    if (Regs.count(*AI))
       return true;
-  }
   return false;
 }
 
@@ -283,9 +282,9 @@ static bool hasRegAlias(unsigned Reg, SparseSet<unsigned> &Regs,
 static SmallVectorImpl<unsigned>::iterator
 findRegAlias(unsigned Reg, SmallVectorImpl<unsigned> &Regs,
              const TargetRegisterInfo *TRI) {
-  for (const uint16_t *Alias = TRI->getOverlaps(Reg); *Alias; ++Alias) {
+  for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI) {
     SmallVectorImpl<unsigned>::iterator I =
-      std::find(Regs.begin(), Regs.end(), *Alias);
+      std::find(Regs.begin(), Regs.end(), *AI);
     if (I != Regs.end())
       return I;
   }
diff --git a/lib/CodeGen/RegisterScavenging.cpp b/lib/CodeGen/RegisterScavenging.cpp
index c965d8715b0..d673794e1b9 100644
--- a/lib/CodeGen/RegisterScavenging.cpp
+++ b/lib/CodeGen/RegisterScavenging.cpp
@@ -37,9 +37,8 @@ using namespace llvm;
 void RegScavenger::setUsed(unsigned Reg) {
   RegsAvailable.reset(Reg);
 
-  for (const uint16_t *SubRegs = TRI->getSubRegisters(Reg);
-       unsigned SubReg = *SubRegs; ++SubRegs)
-    RegsAvailable.reset(SubReg);
+  for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs)
+    RegsAvailable.reset(*SubRegs);
 }
 
 bool RegScavenger::isAliasUsed(unsigned Reg) const {
@@ -112,8 +111,8 @@ void RegScavenger::enterBasicBlock(MachineBasicBlock *mbb) {
 
 void RegScavenger::addRegWithSubRegs(BitVector &BV, unsigned Reg) {
   BV.set(Reg);
-  for (const uint16_t *R = TRI->getSubRegisters(Reg); *R; R++)
-    BV.set(*R);
+  for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs)
+    BV.set(*SubRegs);
 }
 
 void RegScavenger::forward() {
@@ -193,9 +192,8 @@ void RegScavenger::forward() {
         // Ideally we would like a way to model this, but leaving the
         // insert_subreg around causes both correctness and performance issues.
         bool SubUsed = false;
-        for (const uint16_t *SubRegs = TRI->getSubRegisters(Reg);
-             unsigned SubReg = *SubRegs; ++SubRegs)
-          if (isUsed(SubReg)) {
+        for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs)
+          if (isUsed(*SubRegs)) {
             SubUsed = true;
             break;
           }
diff --git a/lib/CodeGen/ScheduleDAGInstrs.cpp b/lib/CodeGen/ScheduleDAGInstrs.cpp
index 54f3dd3fcc5..773a29d0c23 100644
--- a/lib/CodeGen/ScheduleDAGInstrs.cpp
+++ b/lib/CodeGen/ScheduleDAGInstrs.cpp
@@ -241,7 +241,8 @@ void ScheduleDAGInstrs::addPhysRegDataDeps(SUnit *SU,
   unsigned SpecialAddressLatency = ST.getSpecialAddressLatency();
   unsigned DataLatency = SU->Latency;
 
-  for (const uint16_t *Alias = TRI->getOverlaps(MO.getReg()); *Alias; ++Alias) {
+  for (MCRegAliasIterator Alias(MO.getReg(), TRI, true);
+       Alias.isValid(); ++Alias) {
     if (!Uses.contains(*Alias))
       continue;
     std::vector<SUnit*> &UseList = Uses[*Alias];
@@ -294,7 +295,8 @@ void ScheduleDAGInstrs::addPhysRegDeps(SUnit *SU, unsigned OperIdx) {
   // TODO: Using a latency of 1 here for output dependencies assumes
   //       there's no cost for reusing registers.
   SDep::Kind Kind = MO.isUse() ? SDep::Anti : SDep::Output;
-  for (const uint16_t *Alias = TRI->getOverlaps(MO.getReg()); *Alias; ++Alias) {
+  for (MCRegAliasIterator Alias(MO.getReg(), TRI, true);
+       Alias.isValid(); ++Alias) {
     if (!Defs.contains(*Alias))
       continue;
     std::vector<SUnit *> &DefList = Defs[*Alias];
diff --git a/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp b/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp
index 0c92878b311..e90373c0318 100644
--- a/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp
+++ b/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp
@@ -1182,7 +1182,7 @@ static void CheckForLiveRegDef(SUnit *SU, unsigned Reg,
                                SmallSet<unsigned, 4> &RegAdded,
                                SmallVector<unsigned, 4> &LRegs,
                                const TargetRegisterInfo *TRI) {
-  for (const uint16_t *AliasI = TRI->getOverlaps(Reg); *AliasI; ++AliasI) {
+  for (MCRegAliasIterator AliasI(Reg, TRI, true); AliasI.isValid(); ++AliasI) {
 
     // Check if Ref is live.
     if (!LiveRegDefs[*AliasI]) continue;
diff --git a/lib/Target/ARM/Thumb2ITBlockPass.cpp b/lib/Target/ARM/Thumb2ITBlockPass.cpp
index ecb4c2f0e5d..3fce12136cd 100644
--- a/lib/Target/ARM/Thumb2ITBlockPass.cpp
+++ b/lib/Target/ARM/Thumb2ITBlockPass.cpp
@@ -76,16 +76,14 @@ static void TrackDefUses(MachineInstr *MI,
   for (unsigned i = 0, e = LocalUses.size(); i != e; ++i) {
     unsigned Reg = LocalUses[i];
     Uses.insert(Reg);
-    for (const uint16_t *Subreg = TRI->getSubRegisters(Reg);
-         *Subreg; ++Subreg)
+    for (MCSubRegIterator Subreg(Reg, TRI); Subreg.isValid(); ++Subreg)
       Uses.insert(*Subreg);
   }
 
   for (unsigned i = 0, e = LocalDefs.size(); i != e; ++i) {
     unsigned Reg = LocalDefs[i];
     Defs.insert(Reg);
-    for (const uint16_t *Subreg = TRI->getSubRegisters(Reg);
-         *Subreg; ++Subreg)
+    for (MCSubRegIterator Subreg(Reg, TRI); Subreg.isValid(); ++Subreg)
       Defs.insert(*Subreg);
     if (Reg == ARM::CPSR)
       continue;
diff --git a/lib/Target/X86/X86FrameLowering.cpp b/lib/Target/X86/X86FrameLowering.cpp
index 3cf834780e0..c2b1cf7be2f 100644
--- a/lib/Target/X86/X86FrameLowering.cpp
+++ b/lib/Target/X86/X86FrameLowering.cpp
@@ -125,8 +125,8 @@ static unsigned findDeadCallerSavedReg(MachineBasicBlock &MBB,
       unsigned Reg = MO.getReg();
       if (!Reg)
         continue;
-      for (const uint16_t *AsI = TRI.getOverlaps(Reg); *AsI; ++AsI)
-        Uses.insert(*AsI);
+      for (MCRegAliasIterator AI(Reg, &TRI, true); AI.isValid(); ++AI)
+        Uses.insert(*AI);
     }
 
     const uint16_t *CS = Is64Bit ? CallerSavedRegs64Bit : CallerSavedRegs32Bit;
diff --git a/lib/Target/X86/X86RegisterInfo.cpp b/lib/Target/X86/X86RegisterInfo.cpp
index c514d97bae7..b22a086b243 100644
--- a/lib/Target/X86/X86RegisterInfo.cpp
+++ b/lib/Target/X86/X86RegisterInfo.cpp
@@ -323,14 +323,13 @@ BitVector X86RegisterInfo::getReservedRegs(const MachineFunction &MF) const {
         X86::R8,  X86::R9,  X86::R10, X86::R11,
         X86::R12, X86::R13, X86::R14, X86::R15
       };
-      for (const uint16_t *AI = getOverlaps(GPR64[n]); unsigned Reg = *AI; ++AI)
-        Reserved.set(Reg);
+      for (MCRegAliasIterator AI(GPR64[n], this, true); AI.isValid(); ++AI)
+        Reserved.set(*AI);
 
       // XMM8, XMM9, ...
       assert(X86::XMM15 == X86::XMM8+7);
-      for (const uint16_t *AI = getOverlaps(X86::XMM8 + n); unsigned Reg = *AI;
-           ++AI)
-        Reserved.set(Reg);
+      for (MCRegAliasIterator AI(X86::XMM8 + n, this, true); AI.isValid(); ++AI)
+        Reserved.set(*AI);
     }
   }