lib/Target/ARM/ARMISelDAGToDAG.cpp - fp2-dev/platform/external/llvm - Gitiles

 //===-- ARMISelDAGToDAG.cpp - A dag to dag inst selector for ARM ----------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file was developed by Chris Lattner and is distributed under
 // the University of Illinois Open Source License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file defines an instruction selector for the ARM target.
 //
 //===----------------------------------------------------------------------===//

 #include "ARM.h"
 #include "ARMTargetMachine.h"
 #include "llvm/CallingConv.h"
 #include "llvm/DerivedTypes.h"
 #include "llvm/Function.h"
 #include "llvm/Intrinsics.h"
 #include "llvm/CodeGen/MachineFrameInfo.h"
 #include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/CodeGen/MachineInstrBuilder.h"
 #include "llvm/CodeGen/SelectionDAG.h"
 #include "llvm/CodeGen/SelectionDAGISel.h"
 #include "llvm/CodeGen/SSARegMap.h"
 #include "llvm/Target/TargetLowering.h"
 #include "llvm/Support/Debug.h"
 #include <iostream>
 #include <queue>
 #include <set>
 using namespace llvm;

 namespace {
   class ARMTargetLowering : public TargetLowering {
   public:
     ARMTargetLowering(TargetMachine &TM);
     virtual SDOperand LowerOperation(SDOperand Op, SelectionDAG &DAG);
     virtual const char *getTargetNodeName(unsigned Opcode) const;
   };

 }

 ARMTargetLowering::ARMTargetLowering(TargetMachine &TM)
   : TargetLowering(TM) {
   setOperationAction(ISD::RET,           MVT::Other, Custom);
   setOperationAction(ISD::GlobalAddress, MVT::i32,   Custom);
   setOperationAction(ISD::ConstantPool,  MVT::i32,   Custom);

   setSchedulingPreference(SchedulingForRegPressure);
 }

 namespace llvm {
   namespace ARMISD {
     enum NodeType {
       // Start the numbering where the builting ops and target ops leave off.
       FIRST_NUMBER = ISD::BUILTIN_OP_END+ARM::INSTRUCTION_LIST_END,
       /// CALL - A direct function call.
       CALL,

       /// Return with a flag operand.
       RET_FLAG
     };
   }
 }

 const char *ARMTargetLowering::getTargetNodeName(unsigned Opcode) const {
   switch (Opcode) {
   default: return 0;
   case ARMISD::CALL:          return "ARMISD::CALL";
   case ARMISD::RET_FLAG:      return "ARMISD::RET_FLAG";
   }
 }

 // This transforms a ISD::CALL node into a
 // callseq_star <- ARMISD:CALL <- callseq_end
 // chain
 static SDOperand LowerCALL(SDOperand Op, SelectionDAG &DAG) {
   SDOperand Chain    = Op.getOperand(0);
   unsigned CallConv  = cast<ConstantSDNode>(Op.getOperand(1))->getValue();
   assert(CallConv == CallingConv::C && "unknown calling convention");
   bool isVarArg      = cast<ConstantSDNode>(Op.getOperand(2))->getValue() != 0;
   bool isTailCall    = cast<ConstantSDNode>(Op.getOperand(3))->getValue() != 0;
   assert(isTailCall == false && "tail call not supported");
   SDOperand Callee   = Op.getOperand(4);
   unsigned NumOps    = (Op.getNumOperands() - 5) / 2;

   // Count how many bytes are to be pushed on the stack.
   unsigned NumBytes = 0;

   // Add up all the space actually used.
   for (unsigned i = 4; i < NumOps; ++i)
     NumBytes += MVT::getSizeInBits(Op.getOperand(5+2*i).getValueType())/8;

   // Adjust the stack pointer for the new arguments...
   // These operations are automatically eliminated by the prolog/epilog pass
   Chain = DAG.getCALLSEQ_START(Chain,
                                DAG.getConstant(NumBytes, MVT::i32));

   SDOperand StackPtr = DAG.getRegister(ARM::R13, MVT::i32);

   static const unsigned int num_regs = 4;
   static const unsigned regs[num_regs] = {
     ARM::R0, ARM::R1, ARM::R2, ARM::R3
   };

   std::vector<std::pair<unsigned, SDOperand> > RegsToPass;
   std::vector<SDOperand> MemOpChains;

   for (unsigned i = 0; i != NumOps; ++i) {
     SDOperand Arg = Op.getOperand(5+2*i);
     assert(Arg.getValueType() == MVT::i32);
     if (i < num_regs)
       RegsToPass.push_back(std::make_pair(regs[i], Arg));
     else {
       unsigned ArgOffset = (i - num_regs) * 4;
       SDOperand PtrOff = DAG.getConstant(ArgOffset, StackPtr.getValueType());
       PtrOff = DAG.getNode(ISD::ADD, MVT::i32, StackPtr, PtrOff);
       MemOpChains.push_back(DAG.getNode(ISD::STORE, MVT::Other, Chain,
                                           Arg, PtrOff, DAG.getSrcValue(NULL)));
     }
   }
   if (!MemOpChains.empty())
     Chain = DAG.getNode(ISD::TokenFactor, MVT::Other,
                         &MemOpChains[0], MemOpChains.size());

   // Build a sequence of copy-to-reg nodes chained together with token chain
   // and flag operands which copy the outgoing args into the appropriate regs.
   SDOperand InFlag;
   for (unsigned i = 0, e = RegsToPass.size(); i != e; ++i) {
     Chain = DAG.getCopyToReg(Chain, RegsToPass[i].first, RegsToPass[i].second,
                              InFlag);
     InFlag = Chain.getValue(1);
   }

   std::vector<MVT::ValueType> NodeTys;
   NodeTys.push_back(MVT::Other);   // Returns a chain
   NodeTys.push_back(MVT::Flag);    // Returns a flag for retval copy to use.

   // If the callee is a GlobalAddress/ExternalSymbol node (quite common, every
   // direct call is) turn it into a TargetGlobalAddress/TargetExternalSymbol
   // node so that legalize doesn't hack it.
   if (GlobalAddressSDNode *G = dyn_cast<GlobalAddressSDNode>(Callee))
     Callee = DAG.getTargetGlobalAddress(G->getGlobal(), Callee.getValueType());

   // If this is a direct call, pass the chain and the callee.
   assert (Callee.Val);
   std::vector<SDOperand> Ops;
   Ops.push_back(Chain);
   Ops.push_back(Callee);

   // Add argument registers to the end of the list so that they are known live
   // into the call.
   for (unsigned i = 0, e = RegsToPass.size(); i != e; ++i)
     Ops.push_back(DAG.getRegister(RegsToPass[i].first,
                                   RegsToPass[i].second.getValueType()));

   unsigned CallOpc = ARMISD::CALL;
   if (InFlag.Val)
     Ops.push_back(InFlag);
   Chain = DAG.getNode(CallOpc, NodeTys, &Ops[0], Ops.size());
   InFlag = Chain.getValue(1);

   std::vector<SDOperand> ResultVals;
   NodeTys.clear();

   // If the call has results, copy the values out of the ret val registers.
   switch (Op.Val->getValueType(0)) {
   default: assert(0 && "Unexpected ret value!");
   case MVT::Other:
     break;
   case MVT::i32:
     Chain = DAG.getCopyFromReg(Chain, ARM::R0, MVT::i32, InFlag).getValue(1);
     ResultVals.push_back(Chain.getValue(0));
     NodeTys.push_back(MVT::i32);
   }

   Chain = DAG.getNode(ISD::CALLSEQ_END, MVT::Other, Chain,
                       DAG.getConstant(NumBytes, MVT::i32));
   NodeTys.push_back(MVT::Other);

   if (ResultVals.empty())
     return Chain;

   ResultVals.push_back(Chain);
   SDOperand Res = DAG.getNode(ISD::MERGE_VALUES, NodeTys, &ResultVals[0],
                               ResultVals.size());
   return Res.getValue(Op.ResNo);
 }

 static SDOperand LowerRET(SDOperand Op, SelectionDAG &DAG) {
   SDOperand Copy;
   SDOperand Chain = Op.getOperand(0);
   switch(Op.getNumOperands()) {
   default:
     assert(0 && "Do not know how to return this many arguments!");
     abort();
   case 1: {
     SDOperand LR = DAG.getRegister(ARM::R14, MVT::i32);
     return DAG.getNode(ARMISD::RET_FLAG, MVT::Other, Chain);
   }
   case 3:
     Copy = DAG.getCopyToReg(Chain, ARM::R0, Op.getOperand(1), SDOperand());
     if (DAG.getMachineFunction().liveout_empty())
       DAG.getMachineFunction().addLiveOut(ARM::R0);
     break;
   }

   //We must use RET_FLAG instead of BRIND because BRIND doesn't have a flag
   return DAG.getNode(ARMISD::RET_FLAG, MVT::Other, Copy, Copy.getValue(1));
 }

 static SDOperand LowerFORMAL_ARGUMENT(SDOperand Op, SelectionDAG &DAG,
 				      unsigned ArgNo) {
   MachineFunction &MF = DAG.getMachineFunction();
   MVT::ValueType ObjectVT = Op.getValue(ArgNo).getValueType();
   assert (ObjectVT == MVT::i32);
   SDOperand Root = Op.getOperand(0);
   SSARegMap *RegMap = MF.getSSARegMap();

   unsigned num_regs = 4;
   static const unsigned REGS[] = {
     ARM::R0, ARM::R1, ARM::R2, ARM::R3
   };

   if(ArgNo < num_regs) {
     unsigned VReg = RegMap->createVirtualRegister(&ARM::IntRegsRegClass);
     MF.addLiveIn(REGS[ArgNo], VReg);
     return DAG.getCopyFromReg(Root, VReg, MVT::i32);
   } else {
     // If the argument is actually used, emit a load from the right stack
       // slot.
     if (!Op.Val->hasNUsesOfValue(0, ArgNo)) {
       unsigned ArgOffset = (ArgNo - num_regs) * 4;

       MachineFrameInfo *MFI = MF.getFrameInfo();
       unsigned ObjSize = MVT::getSizeInBits(ObjectVT)/8;
       int FI = MFI->CreateFixedObject(ObjSize, ArgOffset);
       SDOperand FIN = DAG.getFrameIndex(FI, MVT::i32);
       return DAG.getLoad(ObjectVT, Root, FIN,
 			 DAG.getSrcValue(NULL));
     } else {
       // Don't emit a dead load.
       return DAG.getNode(ISD::UNDEF, ObjectVT);
     }
   }
 }

 static SDOperand LowerConstantPool(SDOperand Op, SelectionDAG &DAG) {
   MVT::ValueType PtrVT = Op.getValueType();
   ConstantPoolSDNode *CP = cast<ConstantPoolSDNode>(Op);
   Constant *C = CP->get();
   SDOperand CPI = DAG.getTargetConstantPool(C, PtrVT, CP->getAlignment());

   return CPI;
 }

 static SDOperand LowerGlobalAddress(SDOperand Op,
 				    SelectionDAG &DAG) {
   GlobalValue  *GV = cast<GlobalAddressSDNode>(Op)->getGlobal();
   int alignment = 2;
   SDOperand CPAddr = DAG.getConstantPool(GV, MVT::i32, alignment);
   return DAG.getLoad(MVT::i32, DAG.getEntryNode(), CPAddr,
 		     DAG.getSrcValue(NULL));
 }

 static SDOperand LowerFORMAL_ARGUMENTS(SDOperand Op, SelectionDAG &DAG) {
   std::vector<SDOperand> ArgValues;
   SDOperand Root = Op.getOperand(0);

   for (unsigned ArgNo = 0, e = Op.Val->getNumValues()-1; ArgNo != e; ++ArgNo) {
     SDOperand ArgVal = LowerFORMAL_ARGUMENT(Op, DAG, ArgNo);

     ArgValues.push_back(ArgVal);
   }

   bool isVarArg = cast<ConstantSDNode>(Op.getOperand(2))->getValue() != 0;
   assert(!isVarArg);

   ArgValues.push_back(Root);

   // Return the new list of results.
   std::vector<MVT::ValueType> RetVT(Op.Val->value_begin(),
                                     Op.Val->value_end());
   return DAG.getNode(ISD::MERGE_VALUES, RetVT, &ArgValues[0], ArgValues.size());
 }

 SDOperand ARMTargetLowering::LowerOperation(SDOperand Op, SelectionDAG &DAG) {
   switch (Op.getOpcode()) {
   default:
     assert(0 && "Should not custom lower this!");
     abort();
   case ISD::ConstantPool:
     return LowerConstantPool(Op, DAG);
   case ISD::GlobalAddress:
     return LowerGlobalAddress(Op, DAG);
   case ISD::FORMAL_ARGUMENTS:
     return LowerFORMAL_ARGUMENTS(Op, DAG);
   case ISD::CALL:
     return LowerCALL(Op, DAG);
   case ISD::RET:
     return LowerRET(Op, DAG);
   }
 }

 //===----------------------------------------------------------------------===//
 // Instruction Selector Implementation
 //===----------------------------------------------------------------------===//

 //===--------------------------------------------------------------------===//
 /// ARMDAGToDAGISel - ARM specific code to select ARM machine
 /// instructions for SelectionDAG operations.
 ///
 namespace {
 class ARMDAGToDAGISel : public SelectionDAGISel {
   ARMTargetLowering Lowering;

 public:
   ARMDAGToDAGISel(TargetMachine &TM)
     : SelectionDAGISel(Lowering), Lowering(TM) {
   }

   SDNode *Select(SDOperand &Result, SDOperand Op);
   virtual void InstructionSelectBasicBlock(SelectionDAG &DAG);
   bool SelectAddrRegImm(SDOperand N, SDOperand &Offset, SDOperand &Base);

   // Include the pieces autogenerated from the target description.
 #include "ARMGenDAGISel.inc"
 };

 void ARMDAGToDAGISel::InstructionSelectBasicBlock(SelectionDAG &DAG) {
   DEBUG(BB->dump());

   DAG.setRoot(SelectRoot(DAG.getRoot()));
   DAG.RemoveDeadNodes();

   ScheduleAndEmitDAG(DAG);
 }

 static bool isInt12Immediate(SDNode *N, short &Imm) {
   if (N->getOpcode() != ISD::Constant)
     return false;

   int32_t t = cast<ConstantSDNode>(N)->getValue();
   int max = 2<<12 - 1;
   int min = -max;
   if (t > min && t < max) {
     Imm = t;
     return true;
   }
   else
     return false;
 }

 static bool isInt12Immediate(SDOperand Op, short &Imm) {
   return isInt12Immediate(Op.Val, Imm);
 }

 //register plus/minus 12 bit offset
 bool ARMDAGToDAGISel::SelectAddrRegImm(SDOperand N, SDOperand &Offset,
 				    SDOperand &Base) {
   if (N.getOpcode() == ISD::ADD) {
     short imm = 0;
     if (isInt12Immediate(N.getOperand(1), imm)) {
       Offset = CurDAG->getTargetConstant(imm, MVT::i32);
       if (FrameIndexSDNode *FI = dyn_cast<FrameIndexSDNode>(N.getOperand(0))) {
 	Base = CurDAG->getTargetFrameIndex(FI->getIndex(), N.getValueType());
       } else {
 	Base = N.getOperand(0);
       }
       return true; // [r+i]
     }
   }

   Offset = CurDAG->getTargetConstant(0, MVT::i32);
   if (FrameIndexSDNode *FI = dyn_cast<FrameIndexSDNode>(N)) {
     Base = CurDAG->getTargetFrameIndex(FI->getIndex(), N.getValueType());
   }
   else
     Base = N;
   return true;      //any address fits in a register
 }

 SDNode *ARMDAGToDAGISel::Select(SDOperand &Result, SDOperand Op) {
   SDNode *N = Op.Val;

   switch (N->getOpcode()) {
   default:
     return SelectCode(Result, Op);
     break;
   }
   return NULL;
 }

 }  // end anonymous namespace

 /// createARMISelDag - This pass converts a legalized DAG into a
 /// ARM-specific DAG, ready for instruction scheduling.
 ///
 FunctionPass *llvm::createARMISelDag(TargetMachine &TM) {
   return new ARMDAGToDAGISel(TM);
 }
	//===-- ARMISelDAGToDAG.cpp - A dag to dag inst selector for ARM ----------===//
	//
	// The LLVM Compiler Infrastructure
	//
	// This file was developed by Chris Lattner and is distributed under
	// the University of Illinois Open Source License. See LICENSE.TXT for details.
	//
	//===----------------------------------------------------------------------===//
	//
	// This file defines an instruction selector for the ARM target.
	//
	//===----------------------------------------------------------------------===//

	#include "ARM.h"
	#include "ARMTargetMachine.h"
	#include "llvm/CallingConv.h"
	#include "llvm/DerivedTypes.h"
	#include "llvm/Function.h"
	#include "llvm/Intrinsics.h"
	#include "llvm/CodeGen/MachineFrameInfo.h"
	#include "llvm/CodeGen/MachineFunction.h"
	#include "llvm/CodeGen/MachineInstrBuilder.h"
	#include "llvm/CodeGen/SelectionDAG.h"
	#include "llvm/CodeGen/SelectionDAGISel.h"
	#include "llvm/CodeGen/SSARegMap.h"
	#include "llvm/Target/TargetLowering.h"
	#include "llvm/Support/Debug.h"
	#include <iostream>
	#include <queue>
	#include <set>
	using namespace llvm;

	namespace {
	class ARMTargetLowering : public TargetLowering {
	public:
	ARMTargetLowering(TargetMachine &TM);
	virtual SDOperand LowerOperation(SDOperand Op, SelectionDAG &DAG);
	virtual const char *getTargetNodeName(unsigned Opcode) const;
	};

	}

	ARMTargetLowering::ARMTargetLowering(TargetMachine &TM)
	: TargetLowering(TM) {
	setOperationAction(ISD::RET, MVT::Other, Custom);
	setOperationAction(ISD::GlobalAddress, MVT::i32, Custom);
	setOperationAction(ISD::ConstantPool, MVT::i32, Custom);

	setSchedulingPreference(SchedulingForRegPressure);
	}

	namespace llvm {
	namespace ARMISD {
	enum NodeType {
	// Start the numbering where the builting ops and target ops leave off.
	FIRST_NUMBER = ISD::BUILTIN_OP_END+ARM::INSTRUCTION_LIST_END,
	/// CALL - A direct function call.
	CALL,

	/// Return with a flag operand.
	RET_FLAG
	};
	}
	}

	const char *ARMTargetLowering::getTargetNodeName(unsigned Opcode) const {
	switch (Opcode) {
	default: return 0;
	case ARMISD::CALL: return "ARMISD::CALL";
	case ARMISD::RET_FLAG: return "ARMISD::RET_FLAG";
	}
	}

	// This transforms a ISD::CALL node into a
	// callseq_star <- ARMISD:CALL <- callseq_end
	// chain
	static SDOperand LowerCALL(SDOperand Op, SelectionDAG &DAG) {
	SDOperand Chain = Op.getOperand(0);
	unsigned CallConv = cast<ConstantSDNode>(Op.getOperand(1))->getValue();
	assert(CallConv == CallingConv::C && "unknown calling convention");
	bool isVarArg = cast<ConstantSDNode>(Op.getOperand(2))->getValue() != 0;
	bool isTailCall = cast<ConstantSDNode>(Op.getOperand(3))->getValue() != 0;
	assert(isTailCall == false && "tail call not supported");
	SDOperand Callee = Op.getOperand(4);
	unsigned NumOps = (Op.getNumOperands() - 5) / 2;

	// Count how many bytes are to be pushed on the stack.
	unsigned NumBytes = 0;

	// Add up all the space actually used.
	for (unsigned i = 4; i < NumOps; ++i)
	NumBytes += MVT::getSizeInBits(Op.getOperand(5+2*i).getValueType())/8;

	// Adjust the stack pointer for the new arguments...
	// These operations are automatically eliminated by the prolog/epilog pass
	Chain = DAG.getCALLSEQ_START(Chain,
	DAG.getConstant(NumBytes, MVT::i32));

	SDOperand StackPtr = DAG.getRegister(ARM::R13, MVT::i32);

	static const unsigned int num_regs = 4;
	static const unsigned regs[num_regs] = {
	ARM::R0, ARM::R1, ARM::R2, ARM::R3
	};

	std::vector<std::pair<unsigned, SDOperand> > RegsToPass;
	std::vector<SDOperand> MemOpChains;

	for (unsigned i = 0; i != NumOps; ++i) {
	SDOperand Arg = Op.getOperand(5+2*i);
	assert(Arg.getValueType() == MVT::i32);
	if (i < num_regs)
	RegsToPass.push_back(std::make_pair(regs[i], Arg));
	else {
	unsigned ArgOffset = (i - num_regs) * 4;
	SDOperand PtrOff = DAG.getConstant(ArgOffset, StackPtr.getValueType());
	PtrOff = DAG.getNode(ISD::ADD, MVT::i32, StackPtr, PtrOff);
	MemOpChains.push_back(DAG.getNode(ISD::STORE, MVT::Other, Chain,
	Arg, PtrOff, DAG.getSrcValue(NULL)));
	}
	}
	if (!MemOpChains.empty())
	Chain = DAG.getNode(ISD::TokenFactor, MVT::Other,
	&MemOpChains[0], MemOpChains.size());

	// Build a sequence of copy-to-reg nodes chained together with token chain
	// and flag operands which copy the outgoing args into the appropriate regs.
	SDOperand InFlag;
	for (unsigned i = 0, e = RegsToPass.size(); i != e; ++i) {
	Chain = DAG.getCopyToReg(Chain, RegsToPass[i].first, RegsToPass[i].second,
	InFlag);
	InFlag = Chain.getValue(1);
	}

	std::vector<MVT::ValueType> NodeTys;
	NodeTys.push_back(MVT::Other); // Returns a chain
	NodeTys.push_back(MVT::Flag); // Returns a flag for retval copy to use.

	// If the callee is a GlobalAddress/ExternalSymbol node (quite common, every
	// direct call is) turn it into a TargetGlobalAddress/TargetExternalSymbol
	// node so that legalize doesn't hack it.
	if (GlobalAddressSDNode *G = dyn_cast<GlobalAddressSDNode>(Callee))
	Callee = DAG.getTargetGlobalAddress(G->getGlobal(), Callee.getValueType());

	// If this is a direct call, pass the chain and the callee.
	assert (Callee.Val);
	std::vector<SDOperand> Ops;
	Ops.push_back(Chain);
	Ops.push_back(Callee);

	// Add argument registers to the end of the list so that they are known live
	// into the call.
	for (unsigned i = 0, e = RegsToPass.size(); i != e; ++i)
	Ops.push_back(DAG.getRegister(RegsToPass[i].first,
	RegsToPass[i].second.getValueType()));

	unsigned CallOpc = ARMISD::CALL;
	if (InFlag.Val)
	Ops.push_back(InFlag);
	Chain = DAG.getNode(CallOpc, NodeTys, &Ops[0], Ops.size());
	InFlag = Chain.getValue(1);

	std::vector<SDOperand> ResultVals;
	NodeTys.clear();

	// If the call has results, copy the values out of the ret val registers.
	switch (Op.Val->getValueType(0)) {
	default: assert(0 && "Unexpected ret value!");
	case MVT::Other:
	break;
	case MVT::i32:
	Chain = DAG.getCopyFromReg(Chain, ARM::R0, MVT::i32, InFlag).getValue(1);
	ResultVals.push_back(Chain.getValue(0));
	NodeTys.push_back(MVT::i32);
	}

	Chain = DAG.getNode(ISD::CALLSEQ_END, MVT::Other, Chain,
	DAG.getConstant(NumBytes, MVT::i32));
	NodeTys.push_back(MVT::Other);

	if (ResultVals.empty())
	return Chain;

	ResultVals.push_back(Chain);
	SDOperand Res = DAG.getNode(ISD::MERGE_VALUES, NodeTys, &ResultVals[0],
	ResultVals.size());
	return Res.getValue(Op.ResNo);
	}

	static SDOperand LowerRET(SDOperand Op, SelectionDAG &DAG) {
	SDOperand Copy;
	SDOperand Chain = Op.getOperand(0);
	switch(Op.getNumOperands()) {
	default:
	assert(0 && "Do not know how to return this many arguments!");
	abort();
	case 1: {
	SDOperand LR = DAG.getRegister(ARM::R14, MVT::i32);
	return DAG.getNode(ARMISD::RET_FLAG, MVT::Other, Chain);
	}
	case 3:
	Copy = DAG.getCopyToReg(Chain, ARM::R0, Op.getOperand(1), SDOperand());
	if (DAG.getMachineFunction().liveout_empty())
	DAG.getMachineFunction().addLiveOut(ARM::R0);
	break;
	}

	//We must use RET_FLAG instead of BRIND because BRIND doesn't have a flag
	return DAG.getNode(ARMISD::RET_FLAG, MVT::Other, Copy, Copy.getValue(1));
	}

	static SDOperand LowerFORMAL_ARGUMENT(SDOperand Op, SelectionDAG &DAG,
	unsigned ArgNo) {
	MachineFunction &MF = DAG.getMachineFunction();
	MVT::ValueType ObjectVT = Op.getValue(ArgNo).getValueType();
	assert (ObjectVT == MVT::i32);
	SDOperand Root = Op.getOperand(0);
	SSARegMap *RegMap = MF.getSSARegMap();

	unsigned num_regs = 4;
	static const unsigned REGS[] = {
	ARM::R0, ARM::R1, ARM::R2, ARM::R3
	};

	if(ArgNo < num_regs) {
	unsigned VReg = RegMap->createVirtualRegister(&ARM::IntRegsRegClass);
	MF.addLiveIn(REGS[ArgNo], VReg);
	return DAG.getCopyFromReg(Root, VReg, MVT::i32);
	} else {
	// If the argument is actually used, emit a load from the right stack
	// slot.
	if (!Op.Val->hasNUsesOfValue(0, ArgNo)) {
	unsigned ArgOffset = (ArgNo - num_regs) * 4;

	MachineFrameInfo *MFI = MF.getFrameInfo();
	unsigned ObjSize = MVT::getSizeInBits(ObjectVT)/8;
	int FI = MFI->CreateFixedObject(ObjSize, ArgOffset);
	SDOperand FIN = DAG.getFrameIndex(FI, MVT::i32);
	return DAG.getLoad(ObjectVT, Root, FIN,
	DAG.getSrcValue(NULL));
	} else {
	// Don't emit a dead load.
	return DAG.getNode(ISD::UNDEF, ObjectVT);
	}
	}
	}

	static SDOperand LowerConstantPool(SDOperand Op, SelectionDAG &DAG) {
	MVT::ValueType PtrVT = Op.getValueType();
	ConstantPoolSDNode *CP = cast<ConstantPoolSDNode>(Op);
	Constant *C = CP->get();
	SDOperand CPI = DAG.getTargetConstantPool(C, PtrVT, CP->getAlignment());

	return CPI;
	}

	static SDOperand LowerGlobalAddress(SDOperand Op,
	SelectionDAG &DAG) {
	GlobalValue *GV = cast<GlobalAddressSDNode>(Op)->getGlobal();
	int alignment = 2;
	SDOperand CPAddr = DAG.getConstantPool(GV, MVT::i32, alignment);
	return DAG.getLoad(MVT::i32, DAG.getEntryNode(), CPAddr,
	DAG.getSrcValue(NULL));
	}

	static SDOperand LowerFORMAL_ARGUMENTS(SDOperand Op, SelectionDAG &DAG) {
	std::vector<SDOperand> ArgValues;
	SDOperand Root = Op.getOperand(0);

	for (unsigned ArgNo = 0, e = Op.Val->getNumValues()-1; ArgNo != e; ++ArgNo) {
	SDOperand ArgVal = LowerFORMAL_ARGUMENT(Op, DAG, ArgNo);

	ArgValues.push_back(ArgVal);
	}

	bool isVarArg = cast<ConstantSDNode>(Op.getOperand(2))->getValue() != 0;
	assert(!isVarArg);

	ArgValues.push_back(Root);

	// Return the new list of results.
	std::vector<MVT::ValueType> RetVT(Op.Val->value_begin(),
	Op.Val->value_end());
	return DAG.getNode(ISD::MERGE_VALUES, RetVT, &ArgValues[0], ArgValues.size());
	}

	SDOperand ARMTargetLowering::LowerOperation(SDOperand Op, SelectionDAG &DAG) {
	switch (Op.getOpcode()) {
	default:
	assert(0 && "Should not custom lower this!");
	abort();
	case ISD::ConstantPool:
	return LowerConstantPool(Op, DAG);
	case ISD::GlobalAddress:
	return LowerGlobalAddress(Op, DAG);
	case ISD::FORMAL_ARGUMENTS:
	return LowerFORMAL_ARGUMENTS(Op, DAG);
	case ISD::CALL:
	return LowerCALL(Op, DAG);
	case ISD::RET:
	return LowerRET(Op, DAG);
	}
	}

	//===----------------------------------------------------------------------===//
	// Instruction Selector Implementation
	//===----------------------------------------------------------------------===//

	//===--------------------------------------------------------------------===//
	/// ARMDAGToDAGISel - ARM specific code to select ARM machine
	/// instructions for SelectionDAG operations.
	///
	namespace {
	class ARMDAGToDAGISel : public SelectionDAGISel {
	ARMTargetLowering Lowering;

	public:
	ARMDAGToDAGISel(TargetMachine &TM)
	: SelectionDAGISel(Lowering), Lowering(TM) {
	}

	SDNode *Select(SDOperand &Result, SDOperand Op);
	virtual void InstructionSelectBasicBlock(SelectionDAG &DAG);
	bool SelectAddrRegImm(SDOperand N, SDOperand &Offset, SDOperand &Base);

	// Include the pieces autogenerated from the target description.
	#include "ARMGenDAGISel.inc"
	};

	void ARMDAGToDAGISel::InstructionSelectBasicBlock(SelectionDAG &DAG) {
	DEBUG(BB->dump());

	DAG.setRoot(SelectRoot(DAG.getRoot()));
	DAG.RemoveDeadNodes();

	ScheduleAndEmitDAG(DAG);
	}

	static bool isInt12Immediate(SDNode *N, short &Imm) {
	if (N->getOpcode() != ISD::Constant)
	return false;

	int32_t t = cast<ConstantSDNode>(N)->getValue();
	int max = 2<<12 - 1;
	int min = -max;
	if (t > min && t < max) {
	Imm = t;
	return true;
	}
	else
	return false;
	}

	static bool isInt12Immediate(SDOperand Op, short &Imm) {
	return isInt12Immediate(Op.Val, Imm);
	}

	//register plus/minus 12 bit offset
	bool ARMDAGToDAGISel::SelectAddrRegImm(SDOperand N, SDOperand &Offset,
	SDOperand &Base) {
	if (N.getOpcode() == ISD::ADD) {
	short imm = 0;
	if (isInt12Immediate(N.getOperand(1), imm)) {
	Offset = CurDAG->getTargetConstant(imm, MVT::i32);
	if (FrameIndexSDNode *FI = dyn_cast<FrameIndexSDNode>(N.getOperand(0))) {
	Base = CurDAG->getTargetFrameIndex(FI->getIndex(), N.getValueType());
	} else {
	Base = N.getOperand(0);
	}
	return true; // [r+i]
	}
	}

	Offset = CurDAG->getTargetConstant(0, MVT::i32);
	if (FrameIndexSDNode *FI = dyn_cast<FrameIndexSDNode>(N)) {
	Base = CurDAG->getTargetFrameIndex(FI->getIndex(), N.getValueType());
	}
	else
	Base = N;
	return true; //any address fits in a register
	}

	SDNode *ARMDAGToDAGISel::Select(SDOperand &Result, SDOperand Op) {
	SDNode *N = Op.Val;

	switch (N->getOpcode()) {
	default:
	return SelectCode(Result, Op);
	break;
	}
	return NULL;
	}

	} // end anonymous namespace

	/// createARMISelDag - This pass converts a legalized DAG into a
	/// ARM-specific DAG, ready for instruction scheduling.
	///
	FunctionPass *llvm::createARMISelDag(TargetMachine &TM) {
	return new ARMDAGToDAGISel(TM);
	}