diff --git a/include/llvm/CodeGen/MachineBasicBlock.h b/include/llvm/CodeGen/MachineBasicBlock.h
index 1fd36ed55a7..142f8d8fa6f 100644
--- a/include/llvm/CodeGen/MachineBasicBlock.h
+++ b/include/llvm/CodeGen/MachineBasicBlock.h
@@ -63,11 +63,18 @@ public:
   Instructions Insts;
   MachineBasicBlock *Prev, *Next;
   const BasicBlock *BB;
-  std::vector<MachineBasicBlock *> Predecessors;
-  std::vector<MachineBasicBlock *> Successors;
   int Number;
   MachineFunction *Parent;
 
+  /// Predecessors/Successors - Keep track of the predecessor / successor
+  /// basicblocks.
+  std::vector<MachineBasicBlock *> Predecessors;
+  std::vector<MachineBasicBlock *> Successors;
+
+  /// LiveIns - Keep track of the physical registers that are livein of
+  /// the basicblock.
+  std::vector<unsigned> LiveIns;
+
 public:
   MachineBasicBlock(const BasicBlock *bb = 0) : Prev(0), Next(0), BB(bb),
                                                 Number(-1), Parent(0) {
@@ -125,6 +132,19 @@ public:
   unsigned             succ_size()  const { return Successors.size();    }
   bool                 succ_empty() const { return Successors.empty();   }
 
+  // LiveIn management methods.
+
+  /// addLiveIn - Add the specified register as a live in.  Note that it
+  /// is an error to add the same register to the same set more than once.
+  void addLiveIn(unsigned Reg)  { LiveIns.push_back(Reg); }
+
+  // Iteration support for live in sets.  These sets are kept in sorted
+  // order by their register number.
+  typedef std::vector<unsigned>::const_iterator livein_iterator;
+  livein_iterator livein_begin() const { return LiveIns.begin(); }
+  livein_iterator livein_end()   const { return LiveIns.end(); }
+  bool            livein_empty() const { return LiveIns.empty(); }
+
   // Code Layout methods.
   
   /// moveBefore/moveAfter - move 'this' block before or after the specified
diff --git a/lib/CodeGen/MachineBasicBlock.cpp b/lib/CodeGen/MachineBasicBlock.cpp
index a626f4fdd15..d67159d61e7 100644
--- a/lib/CodeGen/MachineBasicBlock.cpp
+++ b/lib/CodeGen/MachineBasicBlock.cpp
@@ -15,6 +15,7 @@
 #include "llvm/BasicBlock.h"
 #include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/CodeGen/MachineInstr.h"
+#include "llvm/Target/MRegisterInfo.h"
 #include "llvm/Target/TargetData.h"
 #include "llvm/Target/TargetInstrInfo.h"
 #include "llvm/Target/TargetMachine.h"
@@ -89,8 +90,20 @@ void MachineBasicBlock::dump() const {
   print(*cerr.stream());
 }
 
+static inline void OutputReg(std::ostream &os, unsigned RegNo,
+                             const MRegisterInfo *MRI = 0) {
+  if (!RegNo || MRegisterInfo::isPhysicalRegister(RegNo)) {
+    if (MRI)
+      os << " %" << MRI->get(RegNo).Name;
+    else
+      os << " %mreg(" << RegNo << ")";
+  } else
+    os << " %reg" << RegNo;
+}
+
 void MachineBasicBlock::print(std::ostream &OS) const {
-  if(!getParent()) {
+  const MachineFunction *MF = getParent();
+  if(!MF) {
     OS << "Can't print out MachineBasicBlock because parent MachineFunction"
        << " is null\n";
     return;
@@ -101,6 +114,14 @@ void MachineBasicBlock::print(std::ostream &OS) const {
   if (LBB) OS << LBB->getName();
   OS << " (" << (const void*)this
      << ", LLVM BB @" << (const void*) LBB << ", ID#" << getNumber()<< "):\n";
+
+  const MRegisterInfo *MRI = MF->getTarget().getRegisterInfo();  
+  if (livein_begin() != livein_end()) {
+    OS << "Live Ins:";
+    for (livein_iterator I = livein_begin(), E = livein_end(); I != E; ++I)
+      OutputReg(OS, *I, MRI);
+    OS << "\n";
+  }
   // Print the preds of this block according to the CFG.
   if (!pred_empty()) {
     OS << "    Predecessors according to CFG:";