ARM64Instruction.cpp

/*******************************************************************************
 * Copyright (c) 2018, 2020 IBM Corp. and others
 *
 * This program and the accompanying materials are made available under
 * the terms of the Eclipse Public License 2.0 which accompanies this
 * distribution and is available at http://eclipse.org/legal/epl-2.0
 * or the Apache License, Version 2.0 which accompanies this distribution
 * and is available at https://www.apache.org/licenses/LICENSE-2.0.
 *
 * This Source Code may also be made available under the following Secondary
 * Licenses when the conditions for such availability set forth in the
 * Eclipse Public License, v. 2.0 are satisfied: GNU General Public License,
 * version 2 with the GNU Classpath Exception [1] and GNU General Public
 * License, version 2 with the OpenJDK Assembly Exception [2].
 *
 * [1] https://www.gnu.org/software/classpath/license.html
 * [2] http://openjdk.java.net/legal/assembly-exception.html
 *
 * SPDX-License-Identifier: EPL-2.0 OR Apache-2.0 OR GPL-2.0 WITH Classpath-exception-2.0 OR LicenseRef-GPL-2.0 WITH Assembly-exception
 *******************************************************************************/

#include "codegen/ARM64Instruction.hpp"
#include "codegen/ARM64OutOfLineCodeSection.hpp"
#include "codegen/CodeGenerator.hpp"
#include "codegen/RegisterDependency.hpp"

void TR::ARM64LabelInstruction::assignRegistersForOutOfLineCodeSection(TR_RegisterKinds kindToBeAssigned)
   {
   TR::Compilation *comp = cg()->comp();

   bool isLabel = getOpCodeValue() == TR::InstOpCode::label;
   bool isBranch = (getOpCodeValue() == TR::InstOpCode::b) || (getKind() == IsConditionalBranch) || (getKind() == IsCompareBranch);

   cg()->freeUnlatchedRegisters();
   // this is the return label from OOL
   if (isLabel && getLabelSymbol()->isEndOfColdInstructionStream())
      {
      TR::Machine *machine = cg()->machine();
      if (comp->getOption(TR_TraceRA))
         traceMsg (comp,"\nOOL: taking register state snap shot\n");
      cg()->setIsOutOfLineHotPath(true);
      machine->takeRegisterStateSnapShot();
      }
   if (isBranch && getLabelSymbol()->isStartOfColdInstructionStream())
      {
      // Switch to the outlined instruction stream and assign registers.
      //
      TR_ARM64OutOfLineCodeSection *oi = cg()->findARM64OutOfLineCodeSectionFromLabel(getLabelSymbol());
      TR_ASSERT(oi, "Could not find ARM64OutOfLineCodeSection stream from label.  instr=%p, label=%p\n", this, getLabelSymbol());
      if (!oi->hasBeenRegisterAssigned())
         oi->assignRegisters(kindToBeAssigned);
      }
   if (isBranch && getLabelSymbol()->isEndOfColdInstructionStream())
      {
      // This if statement prevents RA to restore register snapshot on regular branches to the
      // OOL section merging point. Register snapshot is a snapshot of register states taken at
      // OOL merge label. Using this snapshot RA can enforce the similarity of register states
      // at the end of main-stream code and OOL path.
      // Generally the safer option is to not reuse OOL merge label for any other purpose. This
      // can be done by creating an extra label right after merge point label.
      if (cg()->getIsInOOLSection())
         {
         // Branches from inside an OOL section to the merge-points are not allowed. Branches
         // in the OOL section can jump to the end of section and then only one branch (the
         // last instruction of an OOL section) jumps to the merge-point. In other words, OOL
         // section must contain exactly one exit point.
         TR_ASSERT(cg()->getAppendInstruction() == this, "OOL section must have only one branch to the merge point\n");
         // Start RA for OOL cold path, restore register state from snap shot
         TR::Machine *machine = cg()->machine();
         if (comp->getOption(TR_TraceRA))
            traceMsg (comp, "\nOOL: Restoring Register state from snap shot\n");
         cg()->setIsOutOfLineHotPath(false);
         machine->restoreRegisterStateFromSnapShot();
         }
      // Reusing the OOL Section merge label for other branches might be unsafe.
      else if(comp->getOption(TR_TraceRA))
         traceMsg (comp, "\nOOL: Reusing the OOL Section merge label for other branches might be unsafe.\n");
      }
   }

void TR::ARM64LabelInstruction::assignRegisters(TR_RegisterKinds kindToBeAssigned)
   {
   TR::RegisterDependencyConditions *cond = OMR::ARM64::Instruction::getDependencyConditions();

   if (cond)
      {
      cond->assignPostConditionRegisters(self(), kindToBeAssigned, self()->cg());
      cond->assignPreConditionRegisters(self()->getPrev(), kindToBeAssigned, self()->cg());
      }

   assignRegistersForOutOfLineCodeSection(kindToBeAssigned);
   }

// TR::ARM64AdminInstruction member functions

void TR::ARM64AdminInstruction::assignRegisters(TR_RegisterKinds kindToBeAssigned)
   {
   if (getOpCodeValue() != TR::InstOpCode::assocreg)
      {
      OMR::ARM64::Instruction::assignRegisters(kindToBeAssigned);
      }
   else if (self()->cg()->enableRegisterAssociations())
      {
      TR::Machine *machine = self()->cg()->machine();

      int32_t first = TR::RealRegister::FirstGPR;
      int32_t last  = TR::RealRegister::LastAssignableFPR;
      // Step 1 : First traverse the existing associations and remove them so that they don't interfere with the new ones
      for (int32_t i = first; i <= last; ++i)
         {
         TR::Register *virtReg = machine->getVirtualAssociatedWithReal(static_cast<TR::RealRegister::RegNum>(i));
         if (virtReg)
            {
            virtReg->setAssociation(TR::RealRegister::NoReg);
            }
         }

      // Step 2 : loop through and set up the new associations (both on the machine and by associating the virtual
      // registers with their real dependencies)
      auto depCond = self()->getDependencyConditions();
      auto depGroup = depCond->getPostConditions();
      auto numPostCond = depCond->getNumPostConditions();
      for (int32_t j = 0; j < numPostCond; ++j)
         {
         auto registerDependency = depGroup->getRegisterDependency(j);
         TR::RealRegister::RegNum regNum = registerDependency->getRealRegister();
         TR::Register *virtReg = registerDependency->getRegister();

         machine->setVirtualAssociatedWithReal(regNum, virtReg);
         }

      // Set up virtual to real associations and set register weights
      machine->setRegisterWeightsFromAssociations();
      }
   }

// TR::ARM64Trg1Instruction:: member functions

bool TR::ARM64Trg1Instruction::refsRegister(TR::Register *reg)
   {
   return (reg == getTargetRegister());
   }

bool TR::ARM64Trg1Instruction::usesRegister(TR::Register *reg)
   {
   return false;
   }

bool TR::ARM64Trg1Instruction::defsRegister(TR::Register *reg)
   {
   return (reg == getTargetRegister());
   }

bool TR::ARM64Trg1Instruction::defsRealRegister(TR::Register *reg)
   {
   return (reg == getTargetRegister()->getAssignedRegister());
   }

void TR::ARM64Trg1Instruction::assignRegisters(TR_RegisterKinds kindToBeAssigned)
   {
   if (getDependencyConditions())
      getDependencyConditions()->assignPostConditionRegisters(this, kindToBeAssigned, cg());

   TR::Machine *machine = cg()->machine();
   TR::Register *targetVirtual = getTargetRegister();
   setTargetRegister(machine->assignOneRegister(this, targetVirtual));

   if (getDependencyConditions())
      getDependencyConditions()->assignPreConditionRegisters(this->getPrev(), kindToBeAssigned, cg());
   }

// TR::ARM64Trg1Src1Instruction:: member functions

bool TR::ARM64Trg1Src1Instruction::refsRegister(TR::Register *reg)
   {
   return (reg == getTargetRegister() ||
           reg == getSource1Register() );
   }

bool TR::ARM64Trg1Src1Instruction::usesRegister(TR::Register *reg)
   {
   return (reg == getSource1Register());
   }

bool TR::ARM64Trg1Src1Instruction::defsRegister(TR::Register *reg)
   {
   return (reg == getTargetRegister());
   }

bool TR::ARM64Trg1Src1Instruction::defsRealRegister(TR::Register *reg)
   {
   return (reg == getTargetRegister()->getAssignedRegister());
   }

void TR::ARM64Trg1Src1Instruction::assignRegisters(TR_RegisterKinds kindToBeAssigned)
   {
   TR::Machine *machine = cg()->machine();
   TR::Register *target1Virtual = getTargetRegister();
   TR::Register *source1Virtual = getSource1Register();

   if (getDependencyConditions())
      getDependencyConditions()->assignPostConditionRegisters(this, kindToBeAssigned, cg());

   target1Virtual->block();
   TR::RealRegister *assignedSource1Register = machine->assignOneRegister(this, source1Virtual);
   target1Virtual->unblock();

   source1Virtual->block();
   TR::RealRegister *assignedTarget1Register = machine->assignOneRegister(this, target1Virtual);
   source1Virtual->unblock();

   if (getDependencyConditions())
      getDependencyConditions()->assignPreConditionRegisters(this->getPrev(), kindToBeAssigned, cg());

   setTargetRegister(assignedTarget1Register);
   setSource1Register(assignedSource1Register);
   }

// TR::ARM64Trg1Src2Instruction:: member functions

bool TR::ARM64Trg1Src2Instruction::refsRegister(TR::Register *reg)
   {
   return (reg == getTargetRegister() ||
           reg == getSource1Register() ||
           reg == getSource2Register());
   }

bool TR::ARM64Trg1Src2Instruction::usesRegister(TR::Register *reg)
   {
   return (reg == getSource1Register() || reg == getSource2Register());
   }

bool TR::ARM64Trg1Src2Instruction::defsRegister(TR::Register *reg)
   {
   return (reg == getTargetRegister());
   }

bool TR::ARM64Trg1Src2Instruction::defsRealRegister(TR::Register *reg)
   {
   return (reg == getTargetRegister()->getAssignedRegister());
   }

void TR::ARM64Trg1Src2Instruction::assignRegisters(TR_RegisterKinds kindToBeAssigned)
   {
   TR::Machine *machine = cg()->machine();
   TR::Register *target1Virtual = getTargetRegister();
   TR::Register *source1Virtual = getSource1Register();
   TR::Register *source2Virtual = getSource2Register();

   if (getDependencyConditions())
      getDependencyConditions()->assignPostConditionRegisters(this, kindToBeAssigned, cg());

   source1Virtual->block();
   target1Virtual->block();
   TR::RealRegister *assignedSource2Register = machine->assignOneRegister(this, source2Virtual);
   target1Virtual->unblock();
   source1Virtual->unblock();

   source2Virtual->block();
   target1Virtual->block();
   TR::RealRegister *assignedSource1Register = machine->assignOneRegister(this, source1Virtual);
   target1Virtual->unblock();
   source2Virtual->unblock();

   source2Virtual->block();
   source1Virtual->block();
   TR::RealRegister *assignedTarget1Register = machine->assignOneRegister(this, target1Virtual);
   source1Virtual->unblock();
   source2Virtual->unblock();

   if (getDependencyConditions())
      getDependencyConditions()->assignPreConditionRegisters(this->getPrev(), kindToBeAssigned, cg());

   setTargetRegister(assignedTarget1Register);
   setSource1Register(assignedSource1Register);
   setSource2Register(assignedSource2Register);
   }

// TR::ARM64Trg1Src3Instruction:: member functions

bool TR::ARM64Trg1Src3Instruction::refsRegister(TR::Register *reg)
   {
   return (reg == getTargetRegister() ||
           reg == getSource1Register() ||
           reg == getSource2Register() ||
           reg == getSource3Register());
   }

bool TR::ARM64Trg1Src3Instruction::usesRegister(TR::Register *reg)
   {
   return (reg == getSource1Register() || reg == getSource2Register() || reg == getSource3Register());
   }

bool TR::ARM64Trg1Src3Instruction::defsRegister(TR::Register *reg)
   {
   return (reg == getTargetRegister());
   }

bool TR::ARM64Trg1Src3Instruction::defsRealRegister(TR::Register *reg)
   {
   return (reg == getTargetRegister()->getAssignedRegister());
   }

void TR::ARM64Trg1Src3Instruction::assignRegisters(TR_RegisterKinds kindToBeAssigned)
   {
   TR::Machine *machine = cg()->machine();
   TR::Register *target1Virtual = getTargetRegister();
   TR::Register *source1Virtual = getSource1Register();
   TR::Register *source2Virtual = getSource2Register();
   TR::Register *source3Virtual = getSource3Register();

   if (getDependencyConditions())
      getDependencyConditions()->assignPostConditionRegisters(this, kindToBeAssigned, cg());

   source2Virtual->block();
   source1Virtual->block();
   target1Virtual->block();
   TR::RealRegister *assignedSource3Register = machine->assignOneRegister(this, source3Virtual);
   target1Virtual->unblock();
   source1Virtual->unblock();
   source2Virtual->unblock();

   source3Virtual->block();
   source1Virtual->block();
   target1Virtual->block();
   TR::RealRegister *assignedSource2Register = machine->assignOneRegister(this, source2Virtual);
   target1Virtual->unblock();
   source1Virtual->unblock();
   source3Virtual->unblock();

   source3Virtual->block();
   source2Virtual->block();
   target1Virtual->block();
   TR::RealRegister *assignedSource1Register = machine->assignOneRegister(this, source1Virtual);
   target1Virtual->unblock();
   source2Virtual->unblock();
   source3Virtual->unblock();

   source3Virtual->block();
   source2Virtual->block();
   source1Virtual->block();
   TR::RealRegister *assignedTarget1Register = machine->assignOneRegister(this, target1Virtual);
   source1Virtual->unblock();
   source2Virtual->unblock();
   source3Virtual->unblock();

   if (getDependencyConditions())
      getDependencyConditions()->assignPreConditionRegisters(this->getPrev(), kindToBeAssigned, cg());

   setTargetRegister(assignedTarget1Register);
   setSource1Register(assignedSource1Register);
   setSource2Register(assignedSource2Register);
   setSource3Register(assignedSource3Register);
   }

// TR::ARM64MemSrc1Instruction:: member functions

bool TR::ARM64MemSrc1Instruction::refsRegister(TR::Register *reg)
   {
   return (getMemoryReference()->refsRegister(reg) || reg == getSource1Register());
   }

bool TR::ARM64MemSrc1Instruction::usesRegister(TR::Register *reg)
   {
   return (getMemoryReference()->refsRegister(reg) || reg == getSource1Register());
   }

bool TR::ARM64MemSrc1Instruction::defsRegister(TR::Register *reg)
   {
   return false;
   }

bool TR::ARM64MemSrc1Instruction::defsRealRegister(TR::Register *reg)
   {
   return false;
   }

void TR::ARM64MemSrc1Instruction::assignRegisters(TR_RegisterKinds kindToBeAssigned)
   {
   TR::Machine *machine = cg()->machine();
   TR::MemoryReference *mref = getMemoryReference();
   TR::Register *sourceVirtual = getSource1Register();

   if (getDependencyConditions())
      getDependencyConditions()->assignPostConditionRegisters(this, kindToBeAssigned, cg());

   mref->blockRegisters();
   setSource1Register(machine->assignOneRegister(this, sourceVirtual));
   mref->unblockRegisters();

   sourceVirtual->block();
   mref->assignRegisters(this, cg());
   sourceVirtual->unblock();

   if (getDependencyConditions())
      getDependencyConditions()->assignPreConditionRegisters(this->getPrev(), kindToBeAssigned, cg());
   }

// TR::ARM64MemSrc2Instruction:: member functions

bool TR::ARM64MemSrc2Instruction::refsRegister(TR::Register *reg)
   {
   return (reg == getSource2Register()) || TR::ARM64MemSrc1Instruction::refsRegister(reg);
   }

bool TR::ARM64MemSrc2Instruction::usesRegister(TR::Register *reg)
   {
   return (reg == getSource2Register()) || TR::ARM64MemSrc1Instruction::usesRegister(reg);
   }

bool TR::ARM64MemSrc2Instruction::defsRegister(TR::Register *reg)
   {
   return false;
   }

bool TR::ARM64MemSrc2Instruction::defsRealRegister(TR::Register *reg)
   {
   return false;
   }

void TR::ARM64MemSrc2Instruction::assignRegisters(TR_RegisterKinds kindToBeAssigned)
   {
   TR::Machine *machine = cg()->machine();
   TR::MemoryReference *mref = getMemoryReference();
   TR::Register *source1Virtual = getSource1Register();
   TR::Register *source2Virtual = getSource2Register();

   if (getDependencyConditions())
      getDependencyConditions()->assignPostConditionRegisters(this, kindToBeAssigned, cg());

   mref->blockRegisters();
   source2Virtual->block();
   setSource1Register(machine->assignOneRegister(this, source1Virtual));
   source2Virtual->unblock();
   mref->unblockRegisters();

   mref->blockRegisters();
   source1Virtual->block();
   setSource2Register(machine->assignOneRegister(this, source2Virtual));
   source1Virtual->unblock();
   mref->unblockRegisters();

   source1Virtual->block();
   source2Virtual->block();
   mref->assignRegisters(this, cg());
   source2Virtual->unblock();
   source1Virtual->unblock();

   if (getDependencyConditions())
      getDependencyConditions()->assignPreConditionRegisters(this->getPrev(), kindToBeAssigned, cg());
   }

// TR::ARM64Trg1MemInstruction:: member functions

bool TR::ARM64Trg1MemInstruction::refsRegister(TR::Register *reg)
   {
   return (reg == getTargetRegister() || getMemoryReference()->refsRegister(reg));
   }

bool TR::ARM64Trg1MemInstruction::usesRegister(TR::Register *reg)
   {
   return getMemoryReference()->refsRegister(reg);
   }

bool TR::ARM64Trg1MemInstruction::defsRegister(TR::Register *reg)
   {
   return (reg == getTargetRegister());
   }

bool TR::ARM64Trg1MemInstruction::defsRealRegister(TR::Register *reg)
   {
   return (reg == getTargetRegister()->getAssignedRegister());
   }

void TR::ARM64Trg1MemInstruction::assignRegisters(TR_RegisterKinds kindToBeAssigned)
   {
   TR::Machine *machine = cg()->machine();
   TR::MemoryReference *mref = getMemoryReference();
   TR::Register *targetVirtual = getTargetRegister();

   if (getDependencyConditions())
      getDependencyConditions()->assignPostConditionRegisters(this, kindToBeAssigned, cg());

   mref->blockRegisters();
   setTargetRegister(machine->assignOneRegister(this, targetVirtual));
   mref->unblockRegisters();

   targetVirtual->block();
   mref->assignRegisters(this, cg());
   targetVirtual->unblock();

   if (getDependencyConditions())
      getDependencyConditions()->assignPreConditionRegisters(this->getPrev(), kindToBeAssigned, cg());
   }

// TR::ARM64Trg1MemSrc1Instruction:: member functions

bool TR::ARM64Trg1MemSrc1Instruction::refsRegister(TR::Register *reg)
   {
   return (reg == getTargetRegister() || getMemoryReference()->refsRegister(reg) || reg == getSource1Register());
   }

bool TR::ARM64Trg1MemSrc1Instruction::usesRegister(TR::Register *reg)
   {
   return (getMemoryReference()->refsRegister(reg) || reg == getSource1Register());
   }

bool TR::ARM64Trg1MemSrc1Instruction::defsRegister(TR::Register *reg)
   {
   return (reg == getTargetRegister());
   }

bool TR::ARM64Trg1MemSrc1Instruction::defsRealRegister(TR::Register *reg)
   {
   return (reg == getTargetRegister()->getAssignedRegister());
   }

void TR::ARM64Trg1MemSrc1Instruction::assignRegisters(TR_RegisterKinds kindToBeAssigned)
   {
   TR::Machine *machine = cg()->machine();
   TR::MemoryReference *mref = getMemoryReference();
   TR::Register *sourceVirtual = getSource1Register();
   TR::Register *targetVirtual = getTargetRegister();

   if (getDependencyConditions())
      getDependencyConditions()->assignPostConditionRegisters(this, kindToBeAssigned, cg());

   mref->blockRegisters();
   sourceVirtual->block();
   setTargetRegister(machine->assignOneRegister(this, targetVirtual));
   sourceVirtual->unblock();
   mref->unblockRegisters();

   mref->blockRegisters();
   targetVirtual->block();
   setSource1Register(machine->assignOneRegister(this, sourceVirtual));
   targetVirtual->unblock();
   mref->unblockRegisters();

   sourceVirtual->block();
   targetVirtual->block();
   mref->assignRegisters(this, cg());
   targetVirtual->unblock();
   sourceVirtual->unblock();

   if (getDependencyConditions())
      getDependencyConditions()->assignPreConditionRegisters(this->getPrev(), kindToBeAssigned, cg());
   }

// TR::ARM64Src1Instruction:: member functions

bool TR::ARM64Src1Instruction::refsRegister(TR::Register *reg)
   {
   return (reg == getSource1Register());
   }

bool TR::ARM64Src1Instruction::usesRegister(TR::Register *reg)
   {
   return (reg == getSource1Register());
   }

bool TR::ARM64Src1Instruction::defsRegister(TR::Register *reg)
   {
   return false;
   }

bool TR::ARM64Src1Instruction::defsRealRegister(TR::Register *reg)
   {
   return false;
   }

void TR::ARM64Src1Instruction::assignRegisters(TR_RegisterKinds kindToBeAssigned)
   {
   TR::Machine *machine = cg()->machine();
   TR::Register *source1Virtual = getSource1Register();

   if (getDependencyConditions())
      getDependencyConditions()->assignPostConditionRegisters(this, kindToBeAssigned, cg());

   TR::RealRegister *assignedSource1Register = machine->assignOneRegister(this, source1Virtual);

   if (getDependencyConditions())
      getDependencyConditions()->assignPreConditionRegisters(this->getPrev(), kindToBeAssigned, cg());

   setSource1Register(assignedSource1Register);
   }

// TR::ARM64Src2Instruction:: member functions

bool TR::ARM64Src2Instruction::refsRegister(TR::Register *reg)
   {
   return (reg == getSource1Register() || reg == getSource2Register());
   }

bool TR::ARM64Src2Instruction::usesRegister(TR::Register *reg)
   {
   return (reg == getSource1Register() || reg == getSource2Register());
   }

bool TR::ARM64Src2Instruction::defsRegister(TR::Register *reg)
   {
   return false;
   }

bool TR::ARM64Src2Instruction::defsRealRegister(TR::Register *reg)
   {
   return false;
   }

void TR::ARM64Src2Instruction::assignRegisters(TR_RegisterKinds kindToBeAssigned)
   {
   TR::Machine *machine = cg()->machine();
   TR::Register *source1Virtual = getSource1Register();
   TR::Register *source2Virtual = getSource2Register();

   if (getDependencyConditions())
      getDependencyConditions()->assignPostConditionRegisters(this, kindToBeAssigned, cg());

   source1Virtual->block();
   TR::RealRegister *assignedSource2Register = machine->assignOneRegister(this, source2Virtual);
   source1Virtual->unblock();

   source2Virtual->block();
   TR::RealRegister *assignedSource1Register = machine->assignOneRegister(this, source1Virtual);
   source2Virtual->unblock();

   if (getDependencyConditions())
      getDependencyConditions()->assignPreConditionRegisters(this->getPrev(), kindToBeAssigned, cg());

   setSource1Register(assignedSource1Register);
   setSource2Register(assignedSource2Register);
   }

// TR::ARM64CompareBranchInstruction:: member functions

bool TR::ARM64CompareBranchInstruction::refsRegister(TR::Register *reg)
   {
   return (reg == getSource1Register());
   }

bool TR::ARM64CompareBranchInstruction::usesRegister(TR::Register *reg)
   {
   return (reg == getSource1Register());
   }

bool TR::ARM64CompareBranchInstruction::defsRegister(TR::Register *reg)
   {
   return false;
   }

bool TR::ARM64CompareBranchInstruction::defsRealRegister(TR::Register *reg)
   {
   return false;
   }

void TR::ARM64CompareBranchInstruction::assignRegisters(TR_RegisterKinds kindToBeAssigned)
   {
   TR::Machine *machine = cg()->machine();
   TR::Register *source1Virtual = getSource1Register();

   if (getDependencyConditions())
      getDependencyConditions()->assignPostConditionRegisters(this, kindToBeAssigned, cg());

   TR::RealRegister *assignedSource1Register = machine->assignOneRegister(this, source1Virtual);

   if (getDependencyConditions())
      getDependencyConditions()->assignPreConditionRegisters(this->getPrev(), kindToBeAssigned, cg());

   setSource1Register(assignedSource1Register);

   assignRegistersForOutOfLineCodeSection(kindToBeAssigned);
   }

// TR::ARM64RegBranchInstruction:: member functions

bool TR::ARM64RegBranchInstruction::refsRegister(TR::Register *reg)
   {
   return (reg == getTargetRegister());
   }

bool TR::ARM64RegBranchInstruction::usesRegister(TR::Register *reg)
   {
   return (reg == getTargetRegister());
   }

bool TR::ARM64RegBranchInstruction::defsRegister(TR::Register *reg)
   {
   return false;
   }

bool TR::ARM64RegBranchInstruction::defsRealRegister(TR::Register *reg)
   {
   return false;
   }

void TR::ARM64RegBranchInstruction::assignRegisters(TR_RegisterKinds kindToBeAssigned)
   {
   TR::Machine *machine = cg()->machine();
   TR::Register *targetVirtual = getTargetRegister();

   if (getDependencyConditions())
      getDependencyConditions()->assignPostConditionRegisters(this, kindToBeAssigned, cg());

   TR::RealRegister *assignedTargetRegister = machine->assignOneRegister(this, targetVirtual);

   if (getDependencyConditions())
      getDependencyConditions()->assignPreConditionRegisters(this->getPrev(), kindToBeAssigned, cg());

   setTargetRegister(assignedTargetRegister);
   }