lib/Target/MSP430/MSP430RegisterInfo.cpp - platform/external/llvm - Gitiles

 //===- MSP430RegisterInfo.cpp - MSP430 Register Information ---------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file contains the MSP430 implementation of the TargetRegisterInfo class.
 //
 //===----------------------------------------------------------------------===//

 #define DEBUG_TYPE "msp430-reg-info"

 #include "MSP430.h"
 #include "MSP430MachineFunctionInfo.h"
 #include "MSP430RegisterInfo.h"
 #include "MSP430TargetMachine.h"
 #include "llvm/CodeGen/MachineFrameInfo.h"
 #include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/CodeGen/MachineInstrBuilder.h"
 #include "llvm/Target/TargetMachine.h"
 #include "llvm/Target/TargetOptions.h"
 #include "llvm/ADT/BitVector.h"
 #include "llvm/Support/ErrorHandling.h"

 using namespace llvm;

 // FIXME: Provide proper call frame setup / destroy opcodes.
 MSP430RegisterInfo::MSP430RegisterInfo(MSP430TargetMachine &tm,
                                        const TargetInstrInfo &tii)
   : MSP430GenRegisterInfo(MSP430::ADJCALLSTACKDOWN, MSP430::ADJCALLSTACKUP),
     TM(tm), TII(tii) {
   StackAlign = TM.getFrameInfo()->getStackAlignment();
 }

 const unsigned*
 MSP430RegisterInfo::getCalleeSavedRegs(const MachineFunction *MF) const {
   static const unsigned CalleeSavedRegs[] = {
     MSP430::FPW, MSP430::R5W, MSP430::R6W, MSP430::R7W,
     MSP430::R8W, MSP430::R9W, MSP430::R10W, MSP430::R11W,
     0
   };

   return CalleeSavedRegs;
 }

 const TargetRegisterClass* const*
 MSP430RegisterInfo::getCalleeSavedRegClasses(const MachineFunction *MF) const {
   static const TargetRegisterClass * const CalleeSavedRegClasses[] = {
     &MSP430::GR16RegClass, &MSP430::GR16RegClass,
     &MSP430::GR16RegClass, &MSP430::GR16RegClass,
     &MSP430::GR16RegClass, &MSP430::GR16RegClass,
     &MSP430::GR16RegClass, &MSP430::GR16RegClass,
     0
   };

   return CalleeSavedRegClasses;
 }

 BitVector
 MSP430RegisterInfo::getReservedRegs(const MachineFunction &MF) const {
   BitVector Reserved(getNumRegs());

   // Mark 4 special registers as reserved.
   Reserved.set(MSP430::PCW);
   Reserved.set(MSP430::SPW);
   Reserved.set(MSP430::SRW);
   Reserved.set(MSP430::CGW);

   // Mark frame pointer as reserved if needed.
   if (hasFP(MF))
     Reserved.set(MSP430::FPW);

   return Reserved;
 }

 const TargetRegisterClass* MSP430RegisterInfo::getPointerRegClass() const {
   return &MSP430::GR16RegClass;
 }


 bool MSP430RegisterInfo::hasFP(const MachineFunction &MF) const {
   return NoFramePointerElim || MF.getFrameInfo()->hasVarSizedObjects();
 }

 bool MSP430RegisterInfo::hasReservedCallFrame(MachineFunction &MF) const {
   return !MF.getFrameInfo()->hasVarSizedObjects();
 }

 void MSP430RegisterInfo::
 eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
                               MachineBasicBlock::iterator I) const {
   if (!hasReservedCallFrame(MF)) {
     // If the stack pointer can be changed after prologue, turn the
     // adjcallstackup instruction into a 'sub SPW, <amt>' and the
     // adjcallstackdown instruction into 'add SPW, <amt>'
     // TODO: consider using push / pop instead of sub + store / add
     MachineInstr *Old = I;
     uint64_t Amount = Old->getOperand(0).getImm();
     if (Amount != 0) {
       // We need to keep the stack aligned properly.  To do this, we round the
       // amount of space needed for the outgoing arguments up to the next
       // alignment boundary.
       Amount = (Amount+StackAlign-1)/StackAlign*StackAlign;

       MachineInstr *New = 0;
       if (Old->getOpcode() == getCallFrameSetupOpcode()) {
         New = BuildMI(MF, Old->getDebugLoc(),
                       TII.get(MSP430::SUB16ri), MSP430::SPW)
           .addReg(MSP430::SPW).addImm(Amount);
       } else {
         assert(Old->getOpcode() == getCallFrameDestroyOpcode());
         // factor out the amount the callee already popped.
         uint64_t CalleeAmt = Old->getOperand(1).getImm();
         Amount -= CalleeAmt;
         if (Amount)
           New = BuildMI(MF, Old->getDebugLoc(),
                         TII.get(MSP430::ADD16ri), MSP430::SPW)
             .addReg(MSP430::SPW).addImm(Amount);
       }

       if (New) {
         // The SRW implicit def is dead.
         New->getOperand(3).setIsDead();

         // Replace the pseudo instruction with a new instruction...
         MBB.insert(I, New);
       }
     }
   } else if (I->getOpcode() == getCallFrameDestroyOpcode()) {
     // If we are performing frame pointer elimination and if the callee pops
     // something off the stack pointer, add it back.
     if (uint64_t CalleeAmt = I->getOperand(1).getImm()) {
       MachineInstr *Old = I;
       MachineInstr *New =
         BuildMI(MF, Old->getDebugLoc(), TII.get(MSP430::SUB16ri),
                 MSP430::SPW).addReg(MSP430::SPW).addImm(CalleeAmt);
       // The SRW implicit def is dead.
       New->getOperand(3).setIsDead();

       MBB.insert(I, New);
     }
   }

   MBB.erase(I);
 }

 void
 MSP430RegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator II,
                                         int SPAdj, RegScavenger *RS) const {
   assert(SPAdj == 0 && "Unexpected");

   unsigned i = 0;
   MachineInstr &MI = *II;
   MachineBasicBlock &MBB = *MI.getParent();
   MachineFunction &MF = *MBB.getParent();
   DebugLoc dl = MI.getDebugLoc();
   while (!MI.getOperand(i).isFI()) {
     ++i;
     assert(i < MI.getNumOperands() && "Instr doesn't have FrameIndex operand!");
   }

   int FrameIndex = MI.getOperand(i).getIndex();

   unsigned BasePtr = (hasFP(MF) ? MSP430::FPW : MSP430::SPW);
   int Offset = MF.getFrameInfo()->getObjectOffset(FrameIndex);

   // Skip the saved PC
   Offset += 2;

   if (!hasFP(MF))
     Offset += MF.getFrameInfo()->getStackSize();
   else
     Offset += 2; // Skip the saved FPW

   // Fold imm into offset
   Offset += MI.getOperand(i+1).getImm();

   if (MI.getOpcode() == MSP430::ADD16ri) {
     // This is actually "load effective address" of the stack slot
     // instruction. We have only two-address instructions, thus we need to
     // expand it into mov + add

     MI.setDesc(TII.get(MSP430::MOV16rr));
     MI.getOperand(i).ChangeToRegister(BasePtr, false);

     if (Offset == 0)
       return;

     // We need to materialize the offset via add instruction.
     unsigned DstReg = MI.getOperand(0).getReg();
     if (Offset < 0)
       BuildMI(MBB, next(II), dl, TII.get(MSP430::SUB16ri), DstReg)
         .addReg(DstReg).addImm(-Offset);
     else
       BuildMI(MBB, next(II), dl, TII.get(MSP430::ADD16ri), DstReg)
         .addReg(DstReg).addImm(Offset);

     return;
   }

   MI.getOperand(i).ChangeToRegister(BasePtr, false);
   MI.getOperand(i+1).ChangeToImmediate(Offset);
 }

 void
 MSP430RegisterInfo::processFunctionBeforeFrameFinalized(MachineFunction &MF)
                                                                          const {
   // Create a frame entry for the FPW register that must be saved.
   if (hasFP(MF)) {
     int FrameIdx = MF.getFrameInfo()->CreateFixedObject(2, -4);
     assert(FrameIdx == MF.getFrameInfo()->getObjectIndexBegin() &&
            "Slot for FPW register must be last in order to be found!");
     FrameIdx = 0;
   }
 }


 void MSP430RegisterInfo::emitPrologue(MachineFunction &MF) const {
   MachineBasicBlock &MBB = MF.front();   // Prolog goes in entry BB
   MachineFrameInfo *MFI = MF.getFrameInfo();
   MSP430MachineFunctionInfo *MSP430FI = MF.getInfo<MSP430MachineFunctionInfo>();
   MachineBasicBlock::iterator MBBI = MBB.begin();
   DebugLoc DL = (MBBI != MBB.end() ? MBBI->getDebugLoc() :
                  DebugLoc::getUnknownLoc());

   // Get the number of bytes to allocate from the FrameInfo.
   uint64_t StackSize = MFI->getStackSize();

   uint64_t NumBytes = 0;
   if (hasFP(MF)) {
     // Calculate required stack adjustment
     uint64_t FrameSize = StackSize - 2;
     NumBytes = FrameSize - MSP430FI->getCalleeSavedFrameSize();

     // Get the offset of the stack slot for the EBP register... which is
     // guaranteed to be the last slot by processFunctionBeforeFrameFinalized.
     // Update the frame offset adjustment.
     MFI->setOffsetAdjustment(-NumBytes);

     // Save FPW into the appropriate stack slot...
     BuildMI(MBB, MBBI, DL, TII.get(MSP430::PUSH16r))
       .addReg(MSP430::FPW, RegState::Kill);

     // Update FPW with the new base value...
     BuildMI(MBB, MBBI, DL, TII.get(MSP430::MOV16rr), MSP430::FPW)
       .addReg(MSP430::SPW);

     // Mark the FramePtr as live-in in every block except the entry.
     for (MachineFunction::iterator I = next(MF.begin()), E = MF.end();
          I != E; ++I)
       I->addLiveIn(MSP430::FPW);

   } else
     NumBytes = StackSize - MSP430FI->getCalleeSavedFrameSize();

   // Skip the callee-saved push instructions.
   while (MBBI != MBB.end() && (MBBI->getOpcode() == MSP430::PUSH16r))
     ++MBBI;

   if (MBBI != MBB.end())
     DL = MBBI->getDebugLoc();

   if (NumBytes) { // adjust stack pointer: SPW -= numbytes
     // If there is an SUB16ri of SPW immediately before this instruction, merge
     // the two.
     //NumBytes -= mergeSPUpdates(MBB, MBBI, true);
     // If there is an ADD16ri or SUB16ri of SPW immediately after this
     // instruction, merge the two instructions.
     // mergeSPUpdatesDown(MBB, MBBI, &NumBytes);

     if (NumBytes) {
       MachineInstr *MI =
         BuildMI(MBB, MBBI, DL, TII.get(MSP430::SUB16ri), MSP430::SPW)
         .addReg(MSP430::SPW).addImm(NumBytes);
       // The SRW implicit def is dead.
       MI->getOperand(3).setIsDead();
     }
   }
 }

 void MSP430RegisterInfo::emitEpilogue(MachineFunction &MF,
                                       MachineBasicBlock &MBB) const {
   const MachineFrameInfo *MFI = MF.getFrameInfo();
   MSP430MachineFunctionInfo *MSP430FI = MF.getInfo<MSP430MachineFunctionInfo>();
   MachineBasicBlock::iterator MBBI = prior(MBB.end());
   unsigned RetOpcode = MBBI->getOpcode();
   DebugLoc DL = MBBI->getDebugLoc();

   switch (RetOpcode) {
   case MSP430::RET: break;  // These are ok
   default:
     llvm_unreachable("Can only insert epilog into returning blocks");
   }

   // Get the number of bytes to allocate from the FrameInfo
   uint64_t StackSize = MFI->getStackSize();
   unsigned CSSize = MSP430FI->getCalleeSavedFrameSize();
   uint64_t NumBytes = 0;

   if (hasFP(MF)) {
     // Calculate required stack adjustment
     uint64_t FrameSize = StackSize - 2;
     NumBytes = FrameSize - CSSize;

     // pop FPW.
     BuildMI(MBB, MBBI, DL, TII.get(MSP430::POP16r), MSP430::FPW);
   } else
     NumBytes = StackSize - CSSize;

   // Skip the callee-saved pop instructions.
   MachineBasicBlock::iterator LastCSPop = MBBI;
   while (MBBI != MBB.begin()) {
     MachineBasicBlock::iterator PI = prior(MBBI);
     unsigned Opc = PI->getOpcode();
     if (Opc != MSP430::POP16r && !PI->getDesc().isTerminator())
       break;
     --MBBI;
   }

   DL = MBBI->getDebugLoc();

   // If there is an ADD16ri or SUB16ri of SPW immediately before this
   // instruction, merge the two instructions.
   //if (NumBytes || MFI->hasVarSizedObjects())
   //  mergeSPUpdatesUp(MBB, MBBI, StackPtr, &NumBytes);

   if (MFI->hasVarSizedObjects()) {
     llvm_unreachable("Not implemented yet!");
   } else {
     // adjust stack pointer back: SPW += numbytes
     if (NumBytes) {
       MachineInstr *MI =
         BuildMI(MBB, MBBI, DL, TII.get(MSP430::ADD16ri), MSP430::SPW)
         .addReg(MSP430::SPW).addImm(NumBytes);
       // The SRW implicit def is dead.
       MI->getOperand(3).setIsDead();
     }
   }
 }

 unsigned MSP430RegisterInfo::getRARegister() const {
   return MSP430::PCW;
 }

 unsigned MSP430RegisterInfo::getFrameRegister(MachineFunction &MF) const {
   return hasFP(MF) ? MSP430::FPW : MSP430::SPW;
 }

 int MSP430RegisterInfo::getDwarfRegNum(unsigned RegNum, bool isEH) const {
   llvm_unreachable("Not implemented yet!");
   return 0;
 }

 #include "MSP430GenRegisterInfo.inc"
	//===- MSP430RegisterInfo.cpp - MSP430 Register Information ---------------===//
	//
	// The LLVM Compiler Infrastructure
	//
	// This file is distributed under the University of Illinois Open Source
	// License. See LICENSE.TXT for details.
	//
	//===----------------------------------------------------------------------===//
	//
	// This file contains the MSP430 implementation of the TargetRegisterInfo class.
	//
	//===----------------------------------------------------------------------===//

	#define DEBUG_TYPE "msp430-reg-info"

	#include "MSP430.h"
	#include "MSP430MachineFunctionInfo.h"
	#include "MSP430RegisterInfo.h"
	#include "MSP430TargetMachine.h"
	#include "llvm/CodeGen/MachineFrameInfo.h"
	#include "llvm/CodeGen/MachineFunction.h"
	#include "llvm/CodeGen/MachineInstrBuilder.h"
	#include "llvm/Target/TargetMachine.h"
	#include "llvm/Target/TargetOptions.h"
	#include "llvm/ADT/BitVector.h"
	#include "llvm/Support/ErrorHandling.h"

	using namespace llvm;

	// FIXME: Provide proper call frame setup / destroy opcodes.
	MSP430RegisterInfo::MSP430RegisterInfo(MSP430TargetMachine &tm,
	const TargetInstrInfo &tii)
	: MSP430GenRegisterInfo(MSP430::ADJCALLSTACKDOWN, MSP430::ADJCALLSTACKUP),
	TM(tm), TII(tii) {
	StackAlign = TM.getFrameInfo()->getStackAlignment();
	}

	const unsigned*
	MSP430RegisterInfo::getCalleeSavedRegs(const MachineFunction *MF) const {
	static const unsigned CalleeSavedRegs[] = {
	MSP430::FPW, MSP430::R5W, MSP430::R6W, MSP430::R7W,
	MSP430::R8W, MSP430::R9W, MSP430::R10W, MSP430::R11W,
	0
	};

	return CalleeSavedRegs;
	}

	const TargetRegisterClass* const*
	MSP430RegisterInfo::getCalleeSavedRegClasses(const MachineFunction *MF) const {
	static const TargetRegisterClass * const CalleeSavedRegClasses[] = {
	&MSP430::GR16RegClass, &MSP430::GR16RegClass,
	&MSP430::GR16RegClass, &MSP430::GR16RegClass,
	&MSP430::GR16RegClass, &MSP430::GR16RegClass,
	&MSP430::GR16RegClass, &MSP430::GR16RegClass,
	0
	};

	return CalleeSavedRegClasses;
	}

	BitVector
	MSP430RegisterInfo::getReservedRegs(const MachineFunction &MF) const {
	BitVector Reserved(getNumRegs());

	// Mark 4 special registers as reserved.
	Reserved.set(MSP430::PCW);
	Reserved.set(MSP430::SPW);
	Reserved.set(MSP430::SRW);
	Reserved.set(MSP430::CGW);

	// Mark frame pointer as reserved if needed.
	if (hasFP(MF))
	Reserved.set(MSP430::FPW);

	return Reserved;
	}

	const TargetRegisterClass* MSP430RegisterInfo::getPointerRegClass() const {
	return &MSP430::GR16RegClass;
	}


	bool MSP430RegisterInfo::hasFP(const MachineFunction &MF) const {
	return NoFramePointerElim \|\| MF.getFrameInfo()->hasVarSizedObjects();
	}

	bool MSP430RegisterInfo::hasReservedCallFrame(MachineFunction &MF) const {
	return !MF.getFrameInfo()->hasVarSizedObjects();
	}

	void MSP430RegisterInfo::
	eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
	MachineBasicBlock::iterator I) const {
	if (!hasReservedCallFrame(MF)) {
	// If the stack pointer can be changed after prologue, turn the
	// adjcallstackup instruction into a 'sub SPW, <amt>' and the
	// adjcallstackdown instruction into 'add SPW, <amt>'
	// TODO: consider using push / pop instead of sub + store / add
	MachineInstr *Old = I;
	uint64_t Amount = Old->getOperand(0).getImm();
	if (Amount != 0) {
	// We need to keep the stack aligned properly. To do this, we round the
	// amount of space needed for the outgoing arguments up to the next
	// alignment boundary.
	Amount = (Amount+StackAlign-1)/StackAlign*StackAlign;

	MachineInstr *New = 0;
	if (Old->getOpcode() == getCallFrameSetupOpcode()) {
	New = BuildMI(MF, Old->getDebugLoc(),
	TII.get(MSP430::SUB16ri), MSP430::SPW)
	.addReg(MSP430::SPW).addImm(Amount);
	} else {
	assert(Old->getOpcode() == getCallFrameDestroyOpcode());
	// factor out the amount the callee already popped.
	uint64_t CalleeAmt = Old->getOperand(1).getImm();
	Amount -= CalleeAmt;
	if (Amount)
	New = BuildMI(MF, Old->getDebugLoc(),
	TII.get(MSP430::ADD16ri), MSP430::SPW)
	.addReg(MSP430::SPW).addImm(Amount);
	}

	if (New) {
	// The SRW implicit def is dead.
	New->getOperand(3).setIsDead();

	// Replace the pseudo instruction with a new instruction...
	MBB.insert(I, New);
	}
	}
	} else if (I->getOpcode() == getCallFrameDestroyOpcode()) {
	// If we are performing frame pointer elimination and if the callee pops
	// something off the stack pointer, add it back.
	if (uint64_t CalleeAmt = I->getOperand(1).getImm()) {
	MachineInstr *Old = I;
	MachineInstr *New =
	BuildMI(MF, Old->getDebugLoc(), TII.get(MSP430::SUB16ri),
	MSP430::SPW).addReg(MSP430::SPW).addImm(CalleeAmt);
	// The SRW implicit def is dead.
	New->getOperand(3).setIsDead();

	MBB.insert(I, New);
	}
	}

	MBB.erase(I);
	}

	void
	MSP430RegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator II,
	int SPAdj, RegScavenger *RS) const {
	assert(SPAdj == 0 && "Unexpected");

	unsigned i = 0;
	MachineInstr &MI = *II;
	MachineBasicBlock &MBB = *MI.getParent();
	MachineFunction &MF = *MBB.getParent();
	DebugLoc dl = MI.getDebugLoc();
	while (!MI.getOperand(i).isFI()) {
	++i;
	assert(i < MI.getNumOperands() && "Instr doesn't have FrameIndex operand!");
	}

	int FrameIndex = MI.getOperand(i).getIndex();

	unsigned BasePtr = (hasFP(MF) ? MSP430::FPW : MSP430::SPW);
	int Offset = MF.getFrameInfo()->getObjectOffset(FrameIndex);

	// Skip the saved PC
	Offset += 2;

	if (!hasFP(MF))
	Offset += MF.getFrameInfo()->getStackSize();
	else
	Offset += 2; // Skip the saved FPW

	// Fold imm into offset
	Offset += MI.getOperand(i+1).getImm();

	if (MI.getOpcode() == MSP430::ADD16ri) {
	// This is actually "load effective address" of the stack slot
	// instruction. We have only two-address instructions, thus we need to
	// expand it into mov + add

	MI.setDesc(TII.get(MSP430::MOV16rr));
	MI.getOperand(i).ChangeToRegister(BasePtr, false);

	if (Offset == 0)
	return;

	// We need to materialize the offset via add instruction.
	unsigned DstReg = MI.getOperand(0).getReg();
	if (Offset < 0)
	BuildMI(MBB, next(II), dl, TII.get(MSP430::SUB16ri), DstReg)
	.addReg(DstReg).addImm(-Offset);
	else
	BuildMI(MBB, next(II), dl, TII.get(MSP430::ADD16ri), DstReg)
	.addReg(DstReg).addImm(Offset);

	return;
	}

	MI.getOperand(i).ChangeToRegister(BasePtr, false);
	MI.getOperand(i+1).ChangeToImmediate(Offset);
	}

	void
	MSP430RegisterInfo::processFunctionBeforeFrameFinalized(MachineFunction &MF)
	const {
	// Create a frame entry for the FPW register that must be saved.
	if (hasFP(MF)) {
	int FrameIdx = MF.getFrameInfo()->CreateFixedObject(2, -4);
	assert(FrameIdx == MF.getFrameInfo()->getObjectIndexBegin() &&
	"Slot for FPW register must be last in order to be found!");
	FrameIdx = 0;
	}
	}


	void MSP430RegisterInfo::emitPrologue(MachineFunction &MF) const {
	MachineBasicBlock &MBB = MF.front(); // Prolog goes in entry BB
	MachineFrameInfo *MFI = MF.getFrameInfo();
	MSP430MachineFunctionInfo *MSP430FI = MF.getInfo<MSP430MachineFunctionInfo>();
	MachineBasicBlock::iterator MBBI = MBB.begin();
	DebugLoc DL = (MBBI != MBB.end() ? MBBI->getDebugLoc() :
	DebugLoc::getUnknownLoc());

	// Get the number of bytes to allocate from the FrameInfo.
	uint64_t StackSize = MFI->getStackSize();

	uint64_t NumBytes = 0;
	if (hasFP(MF)) {
	// Calculate required stack adjustment
	uint64_t FrameSize = StackSize - 2;
	NumBytes = FrameSize - MSP430FI->getCalleeSavedFrameSize();

	// Get the offset of the stack slot for the EBP register... which is
	// guaranteed to be the last slot by processFunctionBeforeFrameFinalized.
	// Update the frame offset adjustment.
	MFI->setOffsetAdjustment(-NumBytes);

	// Save FPW into the appropriate stack slot...
	BuildMI(MBB, MBBI, DL, TII.get(MSP430::PUSH16r))
	.addReg(MSP430::FPW, RegState::Kill);

	// Update FPW with the new base value...
	BuildMI(MBB, MBBI, DL, TII.get(MSP430::MOV16rr), MSP430::FPW)
	.addReg(MSP430::SPW);

	// Mark the FramePtr as live-in in every block except the entry.
	for (MachineFunction::iterator I = next(MF.begin()), E = MF.end();
	I != E; ++I)
	I->addLiveIn(MSP430::FPW);

	} else
	NumBytes = StackSize - MSP430FI->getCalleeSavedFrameSize();

	// Skip the callee-saved push instructions.
	while (MBBI != MBB.end() && (MBBI->getOpcode() == MSP430::PUSH16r))
	++MBBI;

	if (MBBI != MBB.end())
	DL = MBBI->getDebugLoc();

	if (NumBytes) { // adjust stack pointer: SPW -= numbytes
	// If there is an SUB16ri of SPW immediately before this instruction, merge
	// the two.
	//NumBytes -= mergeSPUpdates(MBB, MBBI, true);
	// If there is an ADD16ri or SUB16ri of SPW immediately after this
	// instruction, merge the two instructions.
	// mergeSPUpdatesDown(MBB, MBBI, &NumBytes);

	if (NumBytes) {
	MachineInstr *MI =
	BuildMI(MBB, MBBI, DL, TII.get(MSP430::SUB16ri), MSP430::SPW)
	.addReg(MSP430::SPW).addImm(NumBytes);
	// The SRW implicit def is dead.
	MI->getOperand(3).setIsDead();
	}
	}
	}

	void MSP430RegisterInfo::emitEpilogue(MachineFunction &MF,
	MachineBasicBlock &MBB) const {
	const MachineFrameInfo *MFI = MF.getFrameInfo();
	MSP430MachineFunctionInfo *MSP430FI = MF.getInfo<MSP430MachineFunctionInfo>();
	MachineBasicBlock::iterator MBBI = prior(MBB.end());
	unsigned RetOpcode = MBBI->getOpcode();
	DebugLoc DL = MBBI->getDebugLoc();

	switch (RetOpcode) {
	case MSP430::RET: break; // These are ok
	default:
	llvm_unreachable("Can only insert epilog into returning blocks");
	}

	// Get the number of bytes to allocate from the FrameInfo
	uint64_t StackSize = MFI->getStackSize();
	unsigned CSSize = MSP430FI->getCalleeSavedFrameSize();
	uint64_t NumBytes = 0;

	if (hasFP(MF)) {
	// Calculate required stack adjustment
	uint64_t FrameSize = StackSize - 2;
	NumBytes = FrameSize - CSSize;

	// pop FPW.
	BuildMI(MBB, MBBI, DL, TII.get(MSP430::POP16r), MSP430::FPW);
	} else
	NumBytes = StackSize - CSSize;

	// Skip the callee-saved pop instructions.
	MachineBasicBlock::iterator LastCSPop = MBBI;
	while (MBBI != MBB.begin()) {
	MachineBasicBlock::iterator PI = prior(MBBI);
	unsigned Opc = PI->getOpcode();
	if (Opc != MSP430::POP16r && !PI->getDesc().isTerminator())
	break;
	--MBBI;
	}

	DL = MBBI->getDebugLoc();

	// If there is an ADD16ri or SUB16ri of SPW immediately before this
	// instruction, merge the two instructions.
	//if (NumBytes \|\| MFI->hasVarSizedObjects())
	// mergeSPUpdatesUp(MBB, MBBI, StackPtr, &NumBytes);

	if (MFI->hasVarSizedObjects()) {
	llvm_unreachable("Not implemented yet!");
	} else {
	// adjust stack pointer back: SPW += numbytes
	if (NumBytes) {
	MachineInstr *MI =
	BuildMI(MBB, MBBI, DL, TII.get(MSP430::ADD16ri), MSP430::SPW)
	.addReg(MSP430::SPW).addImm(NumBytes);
	// The SRW implicit def is dead.
	MI->getOperand(3).setIsDead();
	}
	}
	}

	unsigned MSP430RegisterInfo::getRARegister() const {
	return MSP430::PCW;
	}

	unsigned MSP430RegisterInfo::getFrameRegister(MachineFunction &MF) const {
	return hasFP(MF) ? MSP430::FPW : MSP430::SPW;
	}

	int MSP430RegisterInfo::getDwarfRegNum(unsigned RegNum, bool isEH) const {
	llvm_unreachable("Not implemented yet!");
	return 0;
	}

	#include "MSP430GenRegisterInfo.inc"