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.
//
//===----------------------------------------------------------------------===//
//
// This file implements the TargetInstrInfo class.
//
//===----------------------------------------------------------------------===//

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

namespace llvm {
  // External object describing the machine instructions Initialized only when
  // the TargetMachine class is created and reset when that class is destroyed.
  //
  // FIXME: UGLY SPARCV9 HACK!
  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
}

// FIXME: SPARCV9 SPECIFIC!
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;
}

// commuteInstruction - The default implementation of this method just exchanges
// operand 1 and 2.
MachineInstr *TargetInstrInfo::commuteInstruction(MachineInstr *MI) const {
  assert(MI->getOperand(1).isRegister() && MI->getOperand(2).isRegister() &&
         "This only knows how to commute register operands so far");
  unsigned Reg1 = MI->getOperand(1).getReg();
  unsigned Reg2 = MI->getOperand(1).getReg();
  MI->SetMachineOperandReg(2, Reg1);
  MI->SetMachineOperandReg(1, Reg2);
  return MI;
}