diff --git a/include/llvm/CodeGen/LiveVariables.h b/include/llvm/CodeGen/LiveVariables.h
index da267c5ddd4..5b42a713189 100644
--- a/include/llvm/CodeGen/LiveVariables.h
+++ b/include/llvm/CodeGen/LiveVariables.h
@@ -31,12 +31,12 @@
 
 #include "llvm/CodeGen/MachineFunctionPass.h"
 #include "llvm/ADT/BitVector.h"
+#include "llvm/ADT/SmallVector.h"
 #include <map>
 
 namespace llvm {
 
 class MRegisterInfo;
-class BitVector;
 
 class LiveVariables : public MachineFunctionPass {
 public:
@@ -127,28 +127,24 @@ private:   // Intermediate data structures
   // PhysRegInfo - Keep track of which instruction was the last def/use of a
   // physical register. This is a purely local property, because all physical
   // register references as presumed dead across basic blocks.
-  std::vector<MachineInstr*> PhysRegInfo;
+  MachineInstr **PhysRegInfo;
 
   // PhysRegUsed - Keep track whether the physical register has been used after
   // its last definition. This is local property.
-  BitVector                  PhysRegUsed;
+  bool          *PhysRegUsed;
+
+  // PhysRegPartUse - Keep track of which instruction was the last partial use
+  // of a physical register (e.g. on X86 a def of EAX followed by a use of AX).
+  // This is a purely local property.
+  MachineInstr **PhysRegPartUse;
 
   // PhysRegPartDef - Keep track of a list of instructions which "partially"
   // defined the physical register (e.g. on X86 AX partially defines EAX).
   // These are turned into use/mod/write if there is a use of the register
   // later in the same block. This is local property.
-  std::vector<std::vector<MachineInstr*> > PhysRegPartDef;
-
-  // PhysRegPartUse - Keep track of which instruction was the last partial use
-  // of a physical register (e.g. on X86 a def of EAX followed by a use of AX).
-  // This is a purely local property.
-  std::vector<MachineInstr*> PhysRegPartUse;
-
-  typedef std::map<const MachineBasicBlock*,
-                   std::vector<unsigned> > PHIVarInfoMap;
-
-  PHIVarInfoMap PHIVarInfo;
+  SmallVector<MachineInstr*, 4> *PhysRegPartDef;
 
+  SmallVector<unsigned, 4> *PHIVarInfo;
 
   /// addRegisterKilled - We have determined MI kills a register. Look for the
   /// operand that uses it and mark it as IsKill.
diff --git a/lib/CodeGen/LiveVariables.cpp b/lib/CodeGen/LiveVariables.cpp
index 310b53a757e..19ea588cd03 100644
--- a/lib/CodeGen/LiveVariables.cpp
+++ b/lib/CodeGen/LiveVariables.cpp
@@ -321,10 +321,15 @@ bool LiveVariables::runOnMachineFunction(MachineFunction &mf) {
 
   ReservedRegisters = RegInfo->getReservedRegs(mf);
 
-  PhysRegInfo.resize(RegInfo->getNumRegs(), (MachineInstr*)NULL);
-  PhysRegUsed.resize(RegInfo->getNumRegs());
-  PhysRegPartDef.resize(RegInfo->getNumRegs());
-  PhysRegPartUse.resize(RegInfo->getNumRegs(), (MachineInstr*)NULL);
+  unsigned NumRegs = RegInfo->getNumRegs();
+  PhysRegInfo = new MachineInstr*[NumRegs];
+  PhysRegUsed = new bool[NumRegs];
+  PhysRegPartUse = new MachineInstr*[NumRegs];
+  PhysRegPartDef = new SmallVector<MachineInstr*,4>[NumRegs];
+  PHIVarInfo = new SmallVector<unsigned, 4>[MF->getNumBlockIDs()];
+  std::fill(PhysRegInfo, PhysRegInfo + NumRegs, (MachineInstr*)0);
+  std::fill(PhysRegUsed, PhysRegUsed + NumRegs, false);
+  std::fill(PhysRegPartUse, PhysRegPartUse + NumRegs, (MachineInstr*)0);
 
   /// Get some space for a respectable number of registers...
   VirtRegInfo.resize(64);
@@ -399,10 +404,10 @@ bool LiveVariables::runOnMachineFunction(MachineFunction &mf) {
     // bottom of this basic block.  We check all of our successor blocks to see
     // if they have PHI nodes, and if so, we simulate an assignment at the end
     // of the current block.
-    if (!PHIVarInfo[MBB].empty()) {
-      std::vector<unsigned>& VarInfoVec = PHIVarInfo[MBB];
+    if (!PHIVarInfo[MBB->getNumber()].empty()) {
+      SmallVector<unsigned, 4>& VarInfoVec = PHIVarInfo[MBB->getNumber()];
 
-      for (std::vector<unsigned>::iterator I = VarInfoVec.begin(),
+      for (SmallVector<unsigned, 4>::iterator I = VarInfoVec.begin(),
              E = VarInfoVec.end(); I != E; ++I) {
         VarInfo& VRInfo = getVarInfo(*I);
         assert(VRInfo.DefInst && "Register use before def (or no def)!");
@@ -428,15 +433,16 @@ bool LiveVariables::runOnMachineFunction(MachineFunction &mf) {
 
     // Loop over PhysRegInfo, killing any registers that are available at the
     // end of the basic block.  This also resets the PhysRegInfo map.
-    for (unsigned i = 0, e = RegInfo->getNumRegs(); i != e; ++i)
+    for (unsigned i = 0; i != NumRegs; ++i)
       if (PhysRegInfo[i])
         HandlePhysRegDef(i, 0);
 
     // Clear some states between BB's. These are purely local information.
-    for (unsigned i = 0, e = RegInfo->getNumRegs(); i != e; ++i) {
+    for (unsigned i = 0; i != NumRegs; ++i) {
       PhysRegPartDef[i].clear();
-      PhysRegPartUse[i] = NULL;
+      //PhysRegPartUse[i] = NULL;
     }
+    std::fill(PhysRegPartUse, PhysRegPartUse + NumRegs, (MachineInstr*)0);
   }
 
   // Convert and transfer the dead / killed information we have gathered into
@@ -460,7 +466,12 @@ bool LiveVariables::runOnMachineFunction(MachineFunction &mf) {
     assert(Visited.count(&*i) != 0 && "unreachable basic block found");
 #endif
 
-  PHIVarInfo.clear();
+  delete[] PhysRegInfo;
+  delete[] PhysRegUsed;
+  delete[] PhysRegPartUse;
+  delete[] PhysRegPartDef;
+  delete[] PHIVarInfo;
+
   return false;
 }
 
@@ -543,6 +554,6 @@ void LiveVariables::analyzePHINodes(const MachineFunction& Fn) {
     for (MachineBasicBlock::const_iterator BBI = I->begin(), BBE = I->end();
          BBI != BBE && BBI->getOpcode() == TargetInstrInfo::PHI; ++BBI)
       for (unsigned i = 1, e = BBI->getNumOperands(); i != e; i += 2)
-        PHIVarInfo[BBI->getOperand(i + 1).getMachineBasicBlock()].
+        PHIVarInfo[BBI->getOperand(i + 1).getMachineBasicBlock()->getNumber()].
           push_back(BBI->getOperand(i).getReg());
 }