diff --git a/lib/CodeGen/AggressiveAntiDepBreaker.cpp b/lib/CodeGen/AggressiveAntiDepBreaker.cpp
index 8482774..62e40e9 100644
--- a/lib/CodeGen/AggressiveAntiDepBreaker.cpp
+++ b/lib/CodeGen/AggressiveAntiDepBreaker.cpp
@@ -41,11 +41,11 @@
 
 AggressiveAntiDepState::AggressiveAntiDepState(const unsigned TargetRegs,
                                                MachineBasicBlock *BB) :
-  NumTargetRegs(TargetRegs), GroupNodes(TargetRegs, 0) {
-  GroupNodeIndices.reserve(TargetRegs);
-  KillIndices.reserve(TargetRegs);
-  DefIndices.reserve(TargetRegs);
-
+  NumTargetRegs(TargetRegs), GroupNodes(TargetRegs, 0),
+  GroupNodeIndices(TargetRegs, 0),
+  KillIndices(TargetRegs, 0),
+  DefIndices(TargetRegs, 0)
+{
   const unsigned BBSize = BB->size();
   for (unsigned i = 0; i < NumTargetRegs; ++i) {
     // Initialize all registers to be in their own group. Initially we
diff --git a/lib/CodeGen/CriticalAntiDepBreaker.cpp b/lib/CodeGen/CriticalAntiDepBreaker.cpp
index e3746a9..cb15166 100644
--- a/lib/CodeGen/CriticalAntiDepBreaker.cpp
+++ b/lib/CodeGen/CriticalAntiDepBreaker.cpp
@@ -32,21 +32,23 @@
   MRI(MF.getRegInfo()),
   TII(MF.getTarget().getInstrInfo()),
   TRI(MF.getTarget().getRegisterInfo()),
-  AllocatableSet(TRI->getAllocatableSet(MF))
-{
-}
+  AllocatableSet(TRI->getAllocatableSet(MF)),
+  Classes(TRI->getNumRegs(), static_cast<const TargetRegisterClass *>(0)),
+  KillIndices(TRI->getNumRegs(), 0),
+  DefIndices(TRI->getNumRegs(), 0) {}
 
 CriticalAntiDepBreaker::~CriticalAntiDepBreaker() {
 }
 
 void CriticalAntiDepBreaker::StartBlock(MachineBasicBlock *BB) {
-  // Clear out the register class data.
-  std::fill(Classes, array_endof(Classes),
-            static_cast<const TargetRegisterClass *>(0));
+  Classes.clear();
 
-  // Initialize the indices to indicate that no registers are live.
   const unsigned BBSize = BB->size();
-  for (unsigned i = 0; i < TRI->getNumRegs(); ++i) {
+  for (unsigned i = 0, e = TRI->getNumRegs(); i != e; ++i) {
+    // Clear out the register class data.
+    Classes[i] = static_cast<const TargetRegisterClass *>(0);
+
+    // Initialize the indices to indicate that no registers are live.
     KillIndices[i] = ~0u;
     DefIndices[i] = BBSize;
   }
@@ -65,6 +67,7 @@
       Classes[Reg] = reinterpret_cast<TargetRegisterClass *>(-1);
       KillIndices[Reg] = BB->size();
       DefIndices[Reg] = ~0u;
+
       // Repeat, for all aliases.
       for (const unsigned *Alias = TRI->getAliasSet(Reg); *Alias; ++Alias) {
         unsigned AliasReg = *Alias;
@@ -86,6 +89,7 @@
       Classes[Reg] = reinterpret_cast<TargetRegisterClass *>(-1);
       KillIndices[Reg] = BB->size();
       DefIndices[Reg] = ~0u;
+
       // Repeat, for all aliases.
       for (const unsigned *Alias = TRI->getAliasSet(Reg); *Alias; ++Alias) {
         unsigned AliasReg = *Alias;
@@ -106,6 +110,7 @@
     Classes[Reg] = reinterpret_cast<TargetRegisterClass *>(-1);
     KillIndices[Reg] = BB->size();
     DefIndices[Reg] = ~0u;
+
     // Repeat, for all aliases.
     for (const unsigned *Alias = TRI->getAliasSet(Reg); *Alias; ++Alias) {
       unsigned AliasReg = *Alias;
@@ -134,8 +139,10 @@
   for (unsigned Reg = 0; Reg != TRI->getNumRegs(); ++Reg)
     if (DefIndices[Reg] < InsertPosIndex && DefIndices[Reg] >= Count) {
       assert(KillIndices[Reg] == ~0u && "Clobbered register is live!");
+
       // Mark this register to be non-renamable.
       Classes[Reg] = reinterpret_cast<TargetRegisterClass *>(-1);
+
       // Move the def index to the end of the previous region, to reflect
       // that the def could theoretically have been scheduled at the end.
       DefIndices[Reg] = InsertPosIndex;
@@ -433,7 +440,7 @@
   // fix that remaining critical edge too. This is a little more involved,
   // because unlike the most recent register, less recent registers should
   // still be considered, though only if no other registers are available.
-  unsigned LastNewReg[TargetRegisterInfo::FirstVirtualRegister] = {};
+  std::vector<unsigned> LastNewReg(TRI->getNumRegs(), 0);
 
   // Attempt to break anti-dependence edges on the critical path. Walk the
   // instructions from the bottom up, tracking information about liveness
diff --git a/lib/CodeGen/CriticalAntiDepBreaker.h b/lib/CodeGen/CriticalAntiDepBreaker.h
index 5406300..0ed7c35 100644
--- a/lib/CodeGen/CriticalAntiDepBreaker.h
+++ b/lib/CodeGen/CriticalAntiDepBreaker.h
@@ -46,19 +46,18 @@
     /// corresponding value is null. If the register is live but used in
     /// multiple register classes, the corresponding value is -1 casted to a
     /// pointer.
-    const TargetRegisterClass *
-      Classes[TargetRegisterInfo::FirstVirtualRegister];
+    std::vector<const TargetRegisterClass*> Classes;
 
     /// RegRegs - Map registers to all their references within a live range.
     std::multimap<unsigned, MachineOperand *> RegRefs;
 
     /// KillIndices - The index of the most recent kill (proceding bottom-up),
     /// or ~0u if the register is not live.
-    unsigned KillIndices[TargetRegisterInfo::FirstVirtualRegister];
+    std::vector<unsigned> KillIndices;
 
     /// DefIndices - The index of the most recent complete def (proceding bottom
     /// up), or ~0u if the register is live.
-    unsigned DefIndices[TargetRegisterInfo::FirstVirtualRegister];
+    std::vector<unsigned> DefIndices;
 
     /// KeepRegs - A set of registers which are live and cannot be changed to
     /// break anti-dependencies.