2 files changed, 50 insertions, 20 deletions

diff --git a/include/llvm/CodeGen/RegisterScavenging.h b/include/llvm/CodeGen/RegisterScavenging.h
index 33d00a7443..65fdaea104 100644
--- a/include/llvm/CodeGen/RegisterScavenging.h
+++ b/include/llvm/CodeGen/RegisterScavenging.h
@@ -27,16 +27,34 @@ class TargetRegisterClass;
 class RegScavenger {
   MachineBasicBlock *MBB;
   MachineBasicBlock::iterator MBBI;
-  bool MBBIInited;
   unsigned NumPhysRegs;
 
+  /// Initialized - All states are initialized and ready to go!
+  bool Initialized;
+
   /// RegStates - The current state of all the physical registers immediately
   /// before MBBI. One bit per physical register. If bit is set that means it's
   /// available, unset means the register is currently being used.
   BitVector RegStates;
 
 public:
-  RegScavenger(MachineBasicBlock *mbb);
+  RegScavenger()
+    : MBB(NULL), Initialized(false) {};
+
+  RegScavenger(MachineBasicBlock *mbb)
+    : MBB(mbb), Initialized(false) {};
+
+  /// Init - Initialize the states.
+  ///
+  void init();
+
+  /// Reset - Discard previous states and re-initialize the states given for
+  /// the specific basic block.
+  void reset(MachineBasicBlock *mbb) {
+    MBB = mbb;
+    clear();
+    init();
+  }
 
   /// forward / backward - Move the internal MBB iterator and update register
   /// states.
@@ -45,8 +63,12 @@ public:
 
   /// forward / backward - Move the internal MBB iterator and update register
   /// states until it has reached but not processed the specific iterator.
-  void forward(MachineBasicBlock::iterator I);
-  void backward(MachineBasicBlock::iterator I);
+  void forward(MachineBasicBlock::iterator I) {
+    while (MBBI != I) forward();
+  }
+  void backward(MachineBasicBlock::iterator I) {
+    while (MBBI != I) backward();
+  }
 
   /// isReserved - Returns true if a register is reserved. It is never "unused".
   bool isReserved(unsigned Reg) const { return ReservedRegs[Reg]; }
@@ -69,10 +91,16 @@ public:
                          bool ExCalleeSaved = false) const;
 
 private:
+  /// clear - Clear states.
+  ///
+  void clear();
+
   /// CalleeSavedrRegs - A bitvector of callee saved registers for the target.
+  ///
   BitVector CalleeSavedRegs;
 
   /// ReservedRegs - A bitvector of reserved registers.
+  ///
   BitVector ReservedRegs;
 };
  
diff --git a/lib/CodeGen/RegisterScavenging.cpp b/lib/CodeGen/RegisterScavenging.cpp
index 3ee0f97f77..0f980a7123 100644
--- a/lib/CodeGen/RegisterScavenging.cpp
+++ b/lib/CodeGen/RegisterScavenging.cpp
@@ -25,12 +25,12 @@
 #include "llvm/ADT/STLExtras.h"
 using namespace llvm;
 
-RegScavenger::RegScavenger(MachineBasicBlock *mbb)
-  : MBB(mbb), MBBIInited(false) {
+void RegScavenger::init() {
   const MachineFunction &MF = *MBB->getParent();
   const TargetMachine &TM = MF.getTarget();
   const MRegisterInfo *RegInfo = TM.getRegisterInfo();
 
+  MBBI = MBB->begin();
   NumPhysRegs = RegInfo->getNumRegs();
   RegStates.resize(NumPhysRegs, true);
 
@@ -50,15 +50,16 @@ RegScavenger::RegScavenger(MachineBasicBlock *mbb)
     for (MachineBasicBlock::const_livein_iterator I = MBB->livein_begin(),
            E = MBB->livein_end(); I != E; ++I)
       setUsed(*I);
+
+  Initialized = true;
 }
 
 void RegScavenger::forward() {
   assert(MBBI != MBB->end() && "Already at the end of the basic block!");
   // Move ptr forward.
-  if (!MBBIInited) {
-    MBBI = MBB->begin();
-    MBBIInited = true;
-  } else
+  if (!Initialized)
+    init();
+  else
     MBBI = next(MBBI);
 
   MachineInstr *MI = MBBI;
@@ -133,16 +134,6 @@ void RegScavenger::backward() {
   setUsed(ChangedRegs);
 }
 
-void RegScavenger::forward(MachineBasicBlock::iterator I) {
-  while (MBBI != I)
-    forward();
-}
-
-void RegScavenger::backward(MachineBasicBlock::iterator I) {
-  while (MBBI != I)
-    backward();
-}
-
 /// CreateRegClassMask - Set the bits that represent the registers in the
 /// TargetRegisterClass.
 static void CreateRegClassMask(const TargetRegisterClass *RC, BitVector &Mask) {
@@ -167,3 +158,14 @@ unsigned RegScavenger::FindUnusedReg(const TargetRegisterClass *RegClass,
   int Reg = RegStatesCopy.find_first();
   return (Reg == -1) ? 0 : Reg;
 }
+
+void RegScavenger::clear() {
+  if (MBB) {
+    MBBI = MBB->end();
+    MBB = NULL;
+  }
+
+  NumPhysRegs = 0;
+  Initialized = false;
+  RegStates.clear();
+}