Machine-independent code generation routines used in instruction

selection.  These used to live in several different places before.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@719 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 714 insertions, 0 deletions

diff --git a/lib/CodeGen/InstrSelection/InstrSelectionSupport.cpp b/lib/CodeGen/InstrSelection/InstrSelectionSupport.cpp
new file mode 100644
index 0000000..685463c
--- /dev/null
+++ b/lib/CodeGen/InstrSelection/InstrSelectionSupport.cpp
@@ -0,0 +1,357 @@
+// $Id$ -*-c++-*-
+//***************************************************************************
+// File:
+//	InstrSelectionSupport.h
+// 
+// Purpose:
+//	Target-independent instruction selection code.
+//      See SparcInstrSelection.cpp for usage.
+//      
+// History:
+//	10/10/01	 -  Vikram Adve  -  Created
+//**************************************************************************/
+
+#include "llvm/CodeGen/InstrSelectionSupport.h"
+#include "llvm/CodeGen/InstrSelection.h"
+#include "llvm/CodeGen/MachineInstr.h"
+#include "llvm/Target/TargetMachine.h"
+#include "llvm/Target/MachineRegInfo.h"
+#include "llvm/ConstPoolVals.h"
+#include "llvm/Instruction.h"
+#include "llvm/Type.h"
+#include "llvm/iMemory.h"
+
+
+//*************************** Local Functions ******************************/
+
+inline int64_t
+GetSignedIntConstantValue(Value* val, bool& isValidConstant)
+{
+  int64_t intValue = 0;
+  isValidConstant = false;
+  
+  if (val->getValueType() == Value::ConstantVal)
+    {
+      switch(val->getType()->getPrimitiveID())
+	{
+	case Type::BoolTyID:
+	  intValue = ((ConstPoolBool*) val)->getValue()? 1 : 0;
+	  isValidConstant = true;
+	  break;
+	case Type::SByteTyID:
+	case Type::ShortTyID:
+	case Type::IntTyID:
+	case Type::LongTyID:
+	  intValue = ((ConstPoolSInt*) val)->getValue();
+	  isValidConstant = true;
+	  break;
+	default:
+	  break;
+	}
+    }
+  
+  return intValue;
+}
+
+inline uint64_t
+GetUnsignedIntConstantValue(Value* val, bool& isValidConstant)
+{
+  uint64_t intValue = 0;
+  isValidConstant = false;
+  
+  if (val->getValueType() == Value::ConstantVal)
+    {
+      switch(val->getType()->getPrimitiveID())
+	{
+	case Type::BoolTyID:
+	  intValue = ((ConstPoolBool*) val)->getValue()? 1 : 0;
+	  isValidConstant = true;
+	  break;
+	case Type::UByteTyID:
+	case Type::UShortTyID:
+	case Type::UIntTyID:
+	case Type::ULongTyID:
+	  intValue = ((ConstPoolUInt*) val)->getValue();
+	  isValidConstant = true;
+	  break;
+	default:
+	  break;
+	}
+    }
+  
+  return intValue;
+}
+
+
+inline int64_t
+GetConstantValueAsSignedInt(Value* val, bool& isValidConstant)
+{
+  int64_t intValue = 0;
+  
+  if (val->getType()->isSigned())
+    {
+      intValue = GetSignedIntConstantValue(val, isValidConstant);
+    }
+  else				// non-numeric types will fall here
+    {
+      uint64_t uintValue = GetUnsignedIntConstantValue(val, isValidConstant);
+      if (isValidConstant && uintValue < INT64_MAX)	// safe to use signed
+	intValue = (int64_t) uintValue;
+      else 
+	isValidConstant = false;
+    }
+  
+  return intValue;
+}
+
+
+//---------------------------------------------------------------------------
+// Function: FoldGetElemChain
+// 
+// Purpose:
+//   Fold a chain of GetElementPtr instructions into an equivalent
+//   (Pointer, IndexVector) pair.  Returns the pointer Value, and
+//   stores the resulting IndexVector in argument chainIdxVec.
+//---------------------------------------------------------------------------
+
+Value*
+FoldGetElemChain(const InstructionNode* getElemInstrNode,
+		 vector<ConstPoolVal*>& chainIdxVec)
+{
+  MemAccessInst* getElemInst = (MemAccessInst*)
+    getElemInstrNode->getInstruction();
+  
+  // Initialize return values from the incoming instruction
+  Value* ptrVal = getElemInst->getPtrOperand();
+  chainIdxVec = getElemInst->getIndexVec(); // copies index vector values
+  
+  // Now chase the chain of getElementInstr instructions, if any
+  InstrTreeNode* ptrChild = getElemInstrNode->leftChild();
+  while (ptrChild->getOpLabel() == Instruction::GetElementPtr ||
+	 ptrChild->getOpLabel() == GetElemPtrIdx)
+    {
+      // Child is a GetElemPtr instruction
+      getElemInst = (MemAccessInst*)
+	((InstructionNode*) ptrChild)->getInstruction();
+      const vector<ConstPoolVal*>& idxVec = getElemInst->getIndexVec();
+      
+      // Get the pointer value out of ptrChild and *prepend* its index vector
+      ptrVal = getElemInst->getPtrOperand();
+      chainIdxVec.insert(chainIdxVec.begin(), idxVec.begin(), idxVec.end());
+      
+      ptrChild = ptrChild->leftChild();
+    }
+  
+  return ptrVal;
+}
+
+
+//------------------------------------------------------------------------ 
+// Function Set2OperandsFromInstr
+// Function Set3OperandsFromInstr
+// 
+// For the common case of 2- and 3-operand arithmetic/logical instructions,
+// set the m/c instr. operands directly from the VM instruction's operands.
+// Check whether the first or second operand is 0 and can use a dedicated "0"
+// register.
+// Check whether the second operand should use an immediate field or register.
+// (First and third operands are never immediates for such instructions.)
+// 
+// Arguments:
+// canDiscardResult: Specifies that the result operand can be discarded
+//		     by using the dedicated "0"
+// 
+// op1position, op2position and resultPosition: Specify in which position
+//		     in the machine instruction the 3 operands (arg1, arg2
+//		     and result) should go.
+// 
+// RETURN VALUE: unsigned int flags, where
+//	flags & 0x01	=> operand 1 is constant and needs a register
+//	flags & 0x02	=> operand 2 is constant and needs a register
+//------------------------------------------------------------------------ 
+
+void
+Set2OperandsFromInstr(MachineInstr* minstr,
+		      InstructionNode* vmInstrNode,
+		      const TargetMachine& target,
+		      bool canDiscardResult,
+		      int op1Position,
+		      int resultPosition)
+{
+  Set3OperandsFromInstr(minstr, vmInstrNode, target,
+			canDiscardResult, op1Position,
+			/*op2Position*/ -1, resultPosition);
+}
+
+#undef REVERT_TO_EXPLICIT_CONSTANT_CHECKS
+#ifdef REVERT_TO_EXPLICIT_CONSTANT_CHECKS
+unsigned
+Set3OperandsFromInstrJUNK(MachineInstr* minstr,
+			  InstructionNode* vmInstrNode,
+			  const TargetMachine& target,
+			  bool canDiscardResult,
+			  int op1Position,
+			  int op2Position,
+			  int resultPosition)
+{
+  assert(op1Position >= 0);
+  assert(resultPosition >= 0);
+  
+  unsigned returnFlags = 0x0;
+  
+  // Check if operand 1 is 0.  If so, try to use a hardwired 0 register.
+  Value* op1Value = vmInstrNode->leftChild()->getValue();
+  bool isValidConstant;
+  int64_t intValue = GetConstantValueAsSignedInt(op1Value, isValidConstant);
+  if (isValidConstant && intValue == 0 && target.zeroRegNum >= 0)
+    minstr->SetMachineOperand(op1Position, /*regNum*/ target.zeroRegNum);
+  else
+    {
+      if (isa<ConstPoolVal>(op1Value))
+	{
+	  // value is constant and must be loaded from constant pool
+	  returnFlags = returnFlags | (1 << op1Position);
+	}
+      minstr->SetMachineOperand(op1Position, MachineOperand::MO_VirtualRegister,
+				op1Value);
+    }
+  
+  // Check if operand 2 (if any) fits in the immed. field of the instruction,
+  // or if it is 0 and can use a dedicated machine register
+  if (op2Position >= 0)
+    {
+      Value* op2Value = vmInstrNode->rightChild()->getValue();
+      int64_t immedValue;
+      unsigned int machineRegNum;
+      
+      MachineOperand::MachineOperandType
+	op2type = ChooseRegOrImmed(op2Value, minstr->getOpCode(), target,
+				   /*canUseImmed*/ true,
+				   machineRegNum, immedValue);
+      
+      if (op2type == MachineOperand::MO_MachineRegister)
+	minstr->SetMachineOperand(op2Position, machineRegNum);
+      else if (op2type == MachineOperand::MO_VirtualRegister)
+	{
+	  if (isa<ConstPoolVal>(op2Value))
+	    {
+	      // value is constant and must be loaded from constant pool
+	      returnFlags = returnFlags | (1 << op2Position);
+	    }
+	  minstr->SetMachineOperand(op2Position, op2type, op2Value);
+	}
+      else
+	{
+	  assert(op2type != MO_CCRegister);
+	  minstr->SetMachineOperand(op2Position, op2type, immedValue);
+	}
+    }
+  
+  // If operand 3 (result) can be discarded, use a dead register if one exists
+  if (canDiscardResult && target.zeroRegNum >= 0)
+    minstr->SetMachineOperand(resultPosition, target.zeroRegNum);
+  else
+    minstr->SetMachineOperand(resultPosition,
+                  MachineOperand::MO_VirtualRegister, vmInstrNode->getValue());
+  
+  return returnFlags;
+}
+#endif
+
+
+void
+Set3OperandsFromInstr(MachineInstr* minstr,
+		      InstructionNode* vmInstrNode,
+		      const TargetMachine& target,
+		      bool canDiscardResult,
+		      int op1Position,
+		      int op2Position,
+		      int resultPosition)
+{
+  assert(op1Position >= 0);
+  assert(resultPosition >= 0);
+  
+  // operand 1
+  minstr->SetMachineOperand(op1Position, MachineOperand::MO_VirtualRegister,
+			    vmInstrNode->leftChild()->getValue());   
+  
+  // operand 2 (if any)
+  if (op2Position >= 0)
+    minstr->SetMachineOperand(op2Position, MachineOperand::MO_VirtualRegister,
+			      vmInstrNode->rightChild()->getValue());   
+  
+  // result operand: if it can be discarded, use a dead register if one exists
+  if (canDiscardResult && target.getRegInfo().getZeroRegNum() >= 0)
+    minstr->SetMachineOperand(resultPosition,
+			      target.getRegInfo().getZeroRegNum());
+  else
+    minstr->SetMachineOperand(resultPosition,
+			      MachineOperand::MO_VirtualRegister, vmInstrNode->getValue());
+}
+
+
+MachineOperand::MachineOperandType
+ChooseRegOrImmed(Value* val,
+		 MachineOpCode opCode,
+		 const TargetMachine& target,
+		 bool canUseImmed,
+		 unsigned int& getMachineRegNum,
+		 int64_t& getImmedValue)
+{
+  MachineOperand::MachineOperandType opType =
+    MachineOperand::MO_VirtualRegister;
+  getMachineRegNum = 0;
+  getImmedValue = 0;
+  
+  // Check for the common case first: argument is not constant
+  // 
+  ConstPoolVal *CPV = dyn_cast<ConstPoolVal>(val);
+  if (!CPV) return opType;
+
+  if (CPV->getType() == Type::BoolTy)
+    {
+      ConstPoolBool *CPB = (ConstPoolBool*)CPV;
+      if (!CPB->getValue() && target.getRegInfo().getZeroRegNum() >= 0)
+	{
+	  getMachineRegNum = target.getRegInfo().getZeroRegNum();
+	  return MachineOperand::MO_MachineRegister;
+	}
+
+      getImmedValue = 1;
+      return MachineOperand::MO_SignExtendedImmed;
+    }
+  
+  if (!CPV->getType()->isIntegral()) return opType;
+
+  // Now get the constant value and check if it fits in the IMMED field.
+  // Take advantage of the fact that the max unsigned value will rarely
+  // fit into any IMMED field and ignore that case (i.e., cast smaller
+  // unsigned constants to signed).
+  // 
+  int64_t intValue;
+  if (CPV->getType()->isSigned())
+    {
+      intValue = ((ConstPoolSInt*)CPV)->getValue();
+    }
+  else
+    {
+      uint64_t V = ((ConstPoolUInt*)CPV)->getValue();
+      if (V >= INT64_MAX) return opType;
+      intValue = (int64_t)V;
+    }
+
+  if (intValue == 0 && target.getRegInfo().getZeroRegNum() >= 0)
+    {
+      opType = MachineOperand::MO_MachineRegister;
+      getMachineRegNum = target.getRegInfo().getZeroRegNum();
+    }
+  else if (canUseImmed &&
+	   target.getInstrInfo().constantFitsInImmedField(opCode, intValue))
+    {
+      opType = MachineOperand::MO_SignExtendedImmed;
+      getImmedValue = intValue;
+    }
+  
+  return opType;
+}
+
diff --git a/lib/Target/SparcV9/InstrSelection/InstrSelectionSupport.cpp b/lib/Target/SparcV9/InstrSelection/InstrSelectionSupport.cpp
new file mode 100644
index 0000000..685463c
--- /dev/null
+++ b/lib/Target/SparcV9/InstrSelection/InstrSelectionSupport.cpp
@@ -0,0 +1,357 @@
+// $Id$ -*-c++-*-
+//***************************************************************************
+// File:
+//	InstrSelectionSupport.h
+// 
+// Purpose:
+//	Target-independent instruction selection code.
+//      See SparcInstrSelection.cpp for usage.
+//      
+// History:
+//	10/10/01	 -  Vikram Adve  -  Created
+//**************************************************************************/
+
+#include "llvm/CodeGen/InstrSelectionSupport.h"
+#include "llvm/CodeGen/InstrSelection.h"
+#include "llvm/CodeGen/MachineInstr.h"
+#include "llvm/Target/TargetMachine.h"
+#include "llvm/Target/MachineRegInfo.h"
+#include "llvm/ConstPoolVals.h"
+#include "llvm/Instruction.h"
+#include "llvm/Type.h"
+#include "llvm/iMemory.h"
+
+
+//*************************** Local Functions ******************************/
+
+inline int64_t
+GetSignedIntConstantValue(Value* val, bool& isValidConstant)
+{
+  int64_t intValue = 0;
+  isValidConstant = false;
+  
+  if (val->getValueType() == Value::ConstantVal)
+    {
+      switch(val->getType()->getPrimitiveID())
+	{
+	case Type::BoolTyID:
+	  intValue = ((ConstPoolBool*) val)->getValue()? 1 : 0;
+	  isValidConstant = true;
+	  break;
+	case Type::SByteTyID:
+	case Type::ShortTyID:
+	case Type::IntTyID:
+	case Type::LongTyID:
+	  intValue = ((ConstPoolSInt*) val)->getValue();
+	  isValidConstant = true;
+	  break;
+	default:
+	  break;
+	}
+    }
+  
+  return intValue;
+}
+
+inline uint64_t
+GetUnsignedIntConstantValue(Value* val, bool& isValidConstant)
+{
+  uint64_t intValue = 0;
+  isValidConstant = false;
+  
+  if (val->getValueType() == Value::ConstantVal)
+    {
+      switch(val->getType()->getPrimitiveID())
+	{
+	case Type::BoolTyID:
+	  intValue = ((ConstPoolBool*) val)->getValue()? 1 : 0;
+	  isValidConstant = true;
+	  break;
+	case Type::UByteTyID:
+	case Type::UShortTyID:
+	case Type::UIntTyID:
+	case Type::ULongTyID:
+	  intValue = ((ConstPoolUInt*) val)->getValue();
+	  isValidConstant = true;
+	  break;
+	default:
+	  break;
+	}
+    }
+  
+  return intValue;
+}
+
+
+inline int64_t
+GetConstantValueAsSignedInt(Value* val, bool& isValidConstant)
+{
+  int64_t intValue = 0;
+  
+  if (val->getType()->isSigned())
+    {
+      intValue = GetSignedIntConstantValue(val, isValidConstant);
+    }
+  else				// non-numeric types will fall here
+    {
+      uint64_t uintValue = GetUnsignedIntConstantValue(val, isValidConstant);
+      if (isValidConstant && uintValue < INT64_MAX)	// safe to use signed
+	intValue = (int64_t) uintValue;
+      else 
+	isValidConstant = false;
+    }
+  
+  return intValue;
+}
+
+
+//---------------------------------------------------------------------------
+// Function: FoldGetElemChain
+// 
+// Purpose:
+//   Fold a chain of GetElementPtr instructions into an equivalent
+//   (Pointer, IndexVector) pair.  Returns the pointer Value, and
+//   stores the resulting IndexVector in argument chainIdxVec.
+//---------------------------------------------------------------------------
+
+Value*
+FoldGetElemChain(const InstructionNode* getElemInstrNode,
+		 vector<ConstPoolVal*>& chainIdxVec)
+{
+  MemAccessInst* getElemInst = (MemAccessInst*)
+    getElemInstrNode->getInstruction();
+  
+  // Initialize return values from the incoming instruction
+  Value* ptrVal = getElemInst->getPtrOperand();
+  chainIdxVec = getElemInst->getIndexVec(); // copies index vector values
+  
+  // Now chase the chain of getElementInstr instructions, if any
+  InstrTreeNode* ptrChild = getElemInstrNode->leftChild();
+  while (ptrChild->getOpLabel() == Instruction::GetElementPtr ||
+	 ptrChild->getOpLabel() == GetElemPtrIdx)
+    {
+      // Child is a GetElemPtr instruction
+      getElemInst = (MemAccessInst*)
+	((InstructionNode*) ptrChild)->getInstruction();
+      const vector<ConstPoolVal*>& idxVec = getElemInst->getIndexVec();
+      
+      // Get the pointer value out of ptrChild and *prepend* its index vector
+      ptrVal = getElemInst->getPtrOperand();
+      chainIdxVec.insert(chainIdxVec.begin(), idxVec.begin(), idxVec.end());
+      
+      ptrChild = ptrChild->leftChild();
+    }
+  
+  return ptrVal;
+}
+
+
+//------------------------------------------------------------------------ 
+// Function Set2OperandsFromInstr
+// Function Set3OperandsFromInstr
+// 
+// For the common case of 2- and 3-operand arithmetic/logical instructions,
+// set the m/c instr. operands directly from the VM instruction's operands.
+// Check whether the first or second operand is 0 and can use a dedicated "0"
+// register.
+// Check whether the second operand should use an immediate field or register.
+// (First and third operands are never immediates for such instructions.)
+// 
+// Arguments:
+// canDiscardResult: Specifies that the result operand can be discarded
+//		     by using the dedicated "0"
+// 
+// op1position, op2position and resultPosition: Specify in which position
+//		     in the machine instruction the 3 operands (arg1, arg2
+//		     and result) should go.
+// 
+// RETURN VALUE: unsigned int flags, where
+//	flags & 0x01	=> operand 1 is constant and needs a register
+//	flags & 0x02	=> operand 2 is constant and needs a register
+//------------------------------------------------------------------------ 
+
+void
+Set2OperandsFromInstr(MachineInstr* minstr,
+		      InstructionNode* vmInstrNode,
+		      const TargetMachine& target,
+		      bool canDiscardResult,
+		      int op1Position,
+		      int resultPosition)
+{
+  Set3OperandsFromInstr(minstr, vmInstrNode, target,
+			canDiscardResult, op1Position,
+			/*op2Position*/ -1, resultPosition);
+}
+
+#undef REVERT_TO_EXPLICIT_CONSTANT_CHECKS
+#ifdef REVERT_TO_EXPLICIT_CONSTANT_CHECKS
+unsigned
+Set3OperandsFromInstrJUNK(MachineInstr* minstr,
+			  InstructionNode* vmInstrNode,
+			  const TargetMachine& target,
+			  bool canDiscardResult,
+			  int op1Position,
+			  int op2Position,
+			  int resultPosition)
+{
+  assert(op1Position >= 0);
+  assert(resultPosition >= 0);
+  
+  unsigned returnFlags = 0x0;
+  
+  // Check if operand 1 is 0.  If so, try to use a hardwired 0 register.
+  Value* op1Value = vmInstrNode->leftChild()->getValue();
+  bool isValidConstant;
+  int64_t intValue = GetConstantValueAsSignedInt(op1Value, isValidConstant);
+  if (isValidConstant && intValue == 0 && target.zeroRegNum >= 0)
+    minstr->SetMachineOperand(op1Position, /*regNum*/ target.zeroRegNum);
+  else
+    {
+      if (isa<ConstPoolVal>(op1Value))
+	{
+	  // value is constant and must be loaded from constant pool
+	  returnFlags = returnFlags | (1 << op1Position);
+	}
+      minstr->SetMachineOperand(op1Position, MachineOperand::MO_VirtualRegister,
+				op1Value);
+    }
+  
+  // Check if operand 2 (if any) fits in the immed. field of the instruction,
+  // or if it is 0 and can use a dedicated machine register
+  if (op2Position >= 0)
+    {
+      Value* op2Value = vmInstrNode->rightChild()->getValue();
+      int64_t immedValue;
+      unsigned int machineRegNum;
+      
+      MachineOperand::MachineOperandType
+	op2type = ChooseRegOrImmed(op2Value, minstr->getOpCode(), target,
+				   /*canUseImmed*/ true,
+				   machineRegNum, immedValue);
+      
+      if (op2type == MachineOperand::MO_MachineRegister)
+	minstr->SetMachineOperand(op2Position, machineRegNum);
+      else if (op2type == MachineOperand::MO_VirtualRegister)
+	{
+	  if (isa<ConstPoolVal>(op2Value))
+	    {
+	      // value is constant and must be loaded from constant pool
+	      returnFlags = returnFlags | (1 << op2Position);
+	    }
+	  minstr->SetMachineOperand(op2Position, op2type, op2Value);
+	}
+      else
+	{
+	  assert(op2type != MO_CCRegister);
+	  minstr->SetMachineOperand(op2Position, op2type, immedValue);
+	}
+    }
+  
+  // If operand 3 (result) can be discarded, use a dead register if one exists
+  if (canDiscardResult && target.zeroRegNum >= 0)
+    minstr->SetMachineOperand(resultPosition, target.zeroRegNum);
+  else
+    minstr->SetMachineOperand(resultPosition,
+                  MachineOperand::MO_VirtualRegister, vmInstrNode->getValue());
+  
+  return returnFlags;
+}
+#endif
+
+
+void
+Set3OperandsFromInstr(MachineInstr* minstr,
+		      InstructionNode* vmInstrNode,
+		      const TargetMachine& target,
+		      bool canDiscardResult,
+		      int op1Position,
+		      int op2Position,
+		      int resultPosition)
+{
+  assert(op1Position >= 0);
+  assert(resultPosition >= 0);
+  
+  // operand 1
+  minstr->SetMachineOperand(op1Position, MachineOperand::MO_VirtualRegister,
+			    vmInstrNode->leftChild()->getValue());   
+  
+  // operand 2 (if any)
+  if (op2Position >= 0)
+    minstr->SetMachineOperand(op2Position, MachineOperand::MO_VirtualRegister,
+			      vmInstrNode->rightChild()->getValue());   
+  
+  // result operand: if it can be discarded, use a dead register if one exists
+  if (canDiscardResult && target.getRegInfo().getZeroRegNum() >= 0)
+    minstr->SetMachineOperand(resultPosition,
+			      target.getRegInfo().getZeroRegNum());
+  else
+    minstr->SetMachineOperand(resultPosition,
+			      MachineOperand::MO_VirtualRegister, vmInstrNode->getValue());
+}
+
+
+MachineOperand::MachineOperandType
+ChooseRegOrImmed(Value* val,
+		 MachineOpCode opCode,
+		 const TargetMachine& target,
+		 bool canUseImmed,
+		 unsigned int& getMachineRegNum,
+		 int64_t& getImmedValue)
+{
+  MachineOperand::MachineOperandType opType =
+    MachineOperand::MO_VirtualRegister;
+  getMachineRegNum = 0;
+  getImmedValue = 0;
+  
+  // Check for the common case first: argument is not constant
+  // 
+  ConstPoolVal *CPV = dyn_cast<ConstPoolVal>(val);
+  if (!CPV) return opType;
+
+  if (CPV->getType() == Type::BoolTy)
+    {
+      ConstPoolBool *CPB = (ConstPoolBool*)CPV;
+      if (!CPB->getValue() && target.getRegInfo().getZeroRegNum() >= 0)
+	{
+	  getMachineRegNum = target.getRegInfo().getZeroRegNum();
+	  return MachineOperand::MO_MachineRegister;
+	}
+
+      getImmedValue = 1;
+      return MachineOperand::MO_SignExtendedImmed;
+    }
+  
+  if (!CPV->getType()->isIntegral()) return opType;
+
+  // Now get the constant value and check if it fits in the IMMED field.
+  // Take advantage of the fact that the max unsigned value will rarely
+  // fit into any IMMED field and ignore that case (i.e., cast smaller
+  // unsigned constants to signed).
+  // 
+  int64_t intValue;
+  if (CPV->getType()->isSigned())
+    {
+      intValue = ((ConstPoolSInt*)CPV)->getValue();
+    }
+  else
+    {
+      uint64_t V = ((ConstPoolUInt*)CPV)->getValue();
+      if (V >= INT64_MAX) return opType;
+      intValue = (int64_t)V;
+    }
+
+  if (intValue == 0 && target.getRegInfo().getZeroRegNum() >= 0)
+    {
+      opType = MachineOperand::MO_MachineRegister;
+      getMachineRegNum = target.getRegInfo().getZeroRegNum();
+    }
+  else if (canUseImmed &&
+	   target.getInstrInfo().constantFitsInImmedField(opCode, intValue))
+    {
+      opType = MachineOperand::MO_SignExtendedImmed;
+      getImmedValue = intValue;
+    }
+  
+  return opType;
+}
+