lib/Target/TargetInstrInfo.cpp

//===-- TargetInstrInfo.cpp - Target Instruction Information --------------===//
// 
//                     The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
// 
//===----------------------------------------------------------------------===//
//
//
//===----------------------------------------------------------------------===//

#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/Constant.h"
#include "llvm/DerivedTypes.h"

namespace llvm {

// External object describing the machine instructions
// Initialized only when the TargetMachine class is created
// and reset when that class is destroyed.
// 
const TargetInstrDescriptor* TargetInstrDescriptors = 0;

TargetInstrInfo::TargetInstrInfo(const TargetInstrDescriptor* Desc,
				 unsigned numOpcodes)
  : desc(Desc), NumOpcodes(numOpcodes) {
  // FIXME: TargetInstrDescriptors should not be global
  assert(TargetInstrDescriptors == NULL && desc != NULL
         && "TargetMachine data structure corrupt; maybe you tried to create another TargetMachine? (only one may exist in a program)");
  TargetInstrDescriptors = desc;	// initialize global variable
}

TargetInstrInfo::~TargetInstrInfo() {
  TargetInstrDescriptors = NULL;	// reset global variable
}

bool TargetInstrInfo::constantFitsInImmedField(MachineOpCode opCode,
					       int64_t intValue) const {
  // First, check if opCode has an immed field.
  bool isSignExtended;
  uint64_t maxImmedValue = maxImmedConstant(opCode, isSignExtended);
  if (maxImmedValue != 0)
    {
      // NEED TO HANDLE UNSIGNED VALUES SINCE THEY MAY BECOME MUCH
      // SMALLER AFTER CASTING TO SIGN-EXTENDED int, short, or char.
      // See CreateUIntSetInstruction in SparcInstrInfo.cpp.
      
      // Now check if the constant fits
      if (intValue <= (int64_t) maxImmedValue &&
	  intValue >= -((int64_t) maxImmedValue+1))
	return true;
    }
  
  return false;
}

} // End llvm namespace