Target/AMDGPU/AMDGPUInstructionSelector.cpp

//===- AMDGPUInstructionSelector.cpp ----------------------------*- C++ -*-==//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
/// \file
/// This file implements the targeting of the InstructionSelector class for
/// AMDGPU.
/// \todo This should be generated by TableGen.
//===----------------------------------------------------------------------===//

#include "AMDGPUInstructionSelector.h"
#include "AMDGPUInstrInfo.h"
#include "AMDGPURegisterBankInfo.h"
#include "AMDGPURegisterInfo.h"
#include "AMDGPUSubtarget.h"
#include "AMDGPUTargetMachine.h"
#include "SIMachineFunctionInfo.h"
#include "MCTargetDesc/AMDGPUMCTargetDesc.h"
#include "llvm/CodeGen/GlobalISel/InstructionSelector.h"
#include "llvm/CodeGen/GlobalISel/InstructionSelectorImpl.h"
#include "llvm/CodeGen/GlobalISel/Utils.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/IR/Type.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"

#define DEBUG_TYPE "amdgpu-isel"

using namespace llvm;

#define GET_GLOBALISEL_IMPL
#define AMDGPUSubtarget GCNSubtarget
#include "AMDGPUGenGlobalISel.inc"
#undef GET_GLOBALISEL_IMPL
#undef AMDGPUSubtarget

AMDGPUInstructionSelector::AMDGPUInstructionSelector(
    const GCNSubtarget &STI, const AMDGPURegisterBankInfo &RBI,
    const AMDGPUTargetMachine &TM)
    : InstructionSelector(), TII(*STI.getInstrInfo()),
      TRI(*STI.getRegisterInfo()), RBI(RBI), TM(TM),
      STI(STI),
      EnableLateStructurizeCFG(AMDGPUTargetMachine::EnableLateStructurizeCFG),
#define GET_GLOBALISEL_PREDICATES_INIT
#include "AMDGPUGenGlobalISel.inc"
#undef GET_GLOBALISEL_PREDICATES_INIT
#define GET_GLOBALISEL_TEMPORARIES_INIT
#include "AMDGPUGenGlobalISel.inc"
#undef GET_GLOBALISEL_TEMPORARIES_INIT
{
}

const char *AMDGPUInstructionSelector::getName() { return DEBUG_TYPE; }

static bool isSCC(unsigned Reg, const MachineRegisterInfo &MRI) {
  if (Reg == AMDGPU::SCC)
    return true;

  if (TargetRegisterInfo::isPhysicalRegister(Reg))
    return false;

  auto &RegClassOrBank = MRI.getRegClassOrRegBank(Reg);
  const TargetRegisterClass *RC =
      RegClassOrBank.dyn_cast<const TargetRegisterClass*>();
  if (RC)
    return RC->getID() == AMDGPU::SReg_32_XM0RegClassID &&
           MRI.getType(Reg).getSizeInBits() == 1;

  const RegisterBank *RB = RegClassOrBank.get<const RegisterBank *>();
  return RB->getID() == AMDGPU::SCCRegBankID;
}

bool AMDGPUInstructionSelector::selectCOPY(MachineInstr &I) const {
  MachineBasicBlock *BB = I.getParent();
  MachineFunction *MF = BB->getParent();
  MachineRegisterInfo &MRI = MF->getRegInfo();
  I.setDesc(TII.get(TargetOpcode::COPY));

  // Special case for COPY from the scc register bank.  The scc register bank
  // is modeled using 32-bit sgprs.
  const MachineOperand &Src = I.getOperand(1);
  unsigned SrcReg = Src.getReg();
  if (!TargetRegisterInfo::isPhysicalRegister(SrcReg) && isSCC(SrcReg, MRI)) {
    unsigned DstReg = TRI.getRegSizeInBits(I.getOperand(0).getReg(), MRI);
    unsigned DstSize = TRI.getRegSizeInBits(DstReg, MRI);

    // We have a copy from a 32-bit to 64-bit register.  This happens
    // when we are selecting scc->vcc copies.
    if (DstSize == 64) {
      const DebugLoc &DL = I.getDebugLoc();
      BuildMI(*BB, &I, DL, TII.get(AMDGPU::V_CMP_NE_U32_e64), I.getOperand(0).getReg())
        .addImm(0)
        .addReg(SrcReg);
      if (!MRI.getRegClassOrNull(SrcReg))
        MRI.setRegClass(SrcReg, TRI.getConstrainedRegClassForOperand(Src, MRI));
      I.eraseFromParent();
      return true;
    }
  }

  for (const MachineOperand &MO : I.operands()) {
    if (TargetRegisterInfo::isPhysicalRegister(MO.getReg()))
      continue;

    const TargetRegisterClass *RC =
            TRI.getConstrainedRegClassForOperand(MO, MRI);
    if (!RC)
      continue;
    RBI.constrainGenericRegister(MO.getReg(), *RC, MRI);
  }
  return true;
}

MachineOperand
AMDGPUInstructionSelector::getSubOperand64(MachineOperand &MO,
                                           unsigned SubIdx) const {

  MachineInstr *MI = MO.getParent();
  MachineBasicBlock *BB = MO.getParent()->getParent();
  MachineFunction *MF = BB->getParent();
  MachineRegisterInfo &MRI = MF->getRegInfo();
  unsigned DstReg = MRI.createVirtualRegister(&AMDGPU::SGPR_32RegClass);

  if (MO.isReg()) {
    unsigned ComposedSubIdx = TRI.composeSubRegIndices(MO.getSubReg(), SubIdx);
    unsigned Reg = MO.getReg();
    BuildMI(*BB, MI, MI->getDebugLoc(), TII.get(AMDGPU::COPY), DstReg)
            .addReg(Reg, 0, ComposedSubIdx);

    return MachineOperand::CreateReg(DstReg, MO.isDef(), MO.isImplicit(),
                                     MO.isKill(), MO.isDead(), MO.isUndef(),
                                     MO.isEarlyClobber(), 0, MO.isDebug(),
                                     MO.isInternalRead());
  }

  assert(MO.isImm());

  APInt Imm(64, MO.getImm());

  switch (SubIdx) {
  default:
    llvm_unreachable("do not know to split immediate with this sub index.");
  case AMDGPU::sub0:
    return MachineOperand::CreateImm(Imm.getLoBits(32).getSExtValue());
  case AMDGPU::sub1:
    return MachineOperand::CreateImm(Imm.getHiBits(32).getSExtValue());
  }
}

static int64_t getConstant(const MachineInstr *MI) {
  return MI->getOperand(1).getCImm()->getSExtValue();
}

bool AMDGPUInstructionSelector::selectG_ADD(MachineInstr &I) const {
  MachineBasicBlock *BB = I.getParent();
  MachineFunction *MF = BB->getParent();
  MachineRegisterInfo &MRI = MF->getRegInfo();
  unsigned Size = RBI.getSizeInBits(I.getOperand(0).getReg(), MRI, TRI);
  unsigned DstLo = MRI.createVirtualRegister(&AMDGPU::SReg_32RegClass);
  unsigned DstHi = MRI.createVirtualRegister(&AMDGPU::SReg_32RegClass);

  if (Size != 64)
    return false;

  DebugLoc DL = I.getDebugLoc();

  MachineOperand Lo1(getSubOperand64(I.getOperand(1), AMDGPU::sub0));
  MachineOperand Lo2(getSubOperand64(I.getOperand(2), AMDGPU::sub0));

  BuildMI(*BB, &I, DL, TII.get(AMDGPU::S_ADD_U32), DstLo)
          .add(Lo1)
          .add(Lo2);

  MachineOperand Hi1(getSubOperand64(I.getOperand(1), AMDGPU::sub1));
  MachineOperand Hi2(getSubOperand64(I.getOperand(2), AMDGPU::sub1));

  BuildMI(*BB, &I, DL, TII.get(AMDGPU::S_ADDC_U32), DstHi)
          .add(Hi1)
          .add(Hi2);

  BuildMI(*BB, &I, DL, TII.get(AMDGPU::REG_SEQUENCE), I.getOperand(0).getReg())
          .addReg(DstLo)
          .addImm(AMDGPU::sub0)
          .addReg(DstHi)
          .addImm(AMDGPU::sub1);

  for (MachineOperand &MO : I.explicit_operands()) {
    if (!MO.isReg() || TargetRegisterInfo::isPhysicalRegister(MO.getReg()))
      continue;
    RBI.constrainGenericRegister(MO.getReg(), AMDGPU::SReg_64RegClass, MRI);
  }

  I.eraseFromParent();
  return true;
}

bool AMDGPUInstructionSelector::selectG_EXTRACT(MachineInstr &I) const {
  MachineBasicBlock *BB = I.getParent();
  MachineFunction *MF = BB->getParent();
  MachineRegisterInfo &MRI = MF->getRegInfo();
  assert(I.getOperand(2).getImm() % 32 == 0);
  unsigned SubReg = TRI.getSubRegFromChannel(I.getOperand(2).getImm() / 32);
  const DebugLoc &DL = I.getDebugLoc();
  MachineInstr *Copy = BuildMI(*BB, &I, DL, TII.get(TargetOpcode::COPY),
                               I.getOperand(0).getReg())
                               .addReg(I.getOperand(1).getReg(), 0, SubReg);

  for (const MachineOperand &MO : Copy->operands()) {
    const TargetRegisterClass *RC =
            TRI.getConstrainedRegClassForOperand(MO, MRI);
    if (!RC)
      continue;
    RBI.constrainGenericRegister(MO.getReg(), *RC, MRI);
  }
  I.eraseFromParent();
  return true;
}

bool AMDGPUInstructionSelector::selectG_GEP(MachineInstr &I) const {
  return selectG_ADD(I);
}

bool AMDGPUInstructionSelector::selectG_IMPLICIT_DEF(MachineInstr &I) const {
  MachineBasicBlock *BB = I.getParent();
  MachineFunction *MF = BB->getParent();
  MachineRegisterInfo &MRI = MF->getRegInfo();
  const MachineOperand &MO = I.getOperand(0);

  // FIXME: Interface for getConstrainedRegClassForOperand needs work. The
  // regbank check here is to know why getConstrainedRegClassForOperand failed.
  const TargetRegisterClass *RC = TRI.getConstrainedRegClassForOperand(MO, MRI);
  if ((!RC && !MRI.getRegBankOrNull(MO.getReg())) ||
      (RC && RBI.constrainGenericRegister(MO.getReg(), *RC, MRI))) {
    I.setDesc(TII.get(TargetOpcode::IMPLICIT_DEF));
    return true;
  }

  return false;
}

bool AMDGPUInstructionSelector::selectG_INSERT(MachineInstr &I) const {
  MachineBasicBlock *BB = I.getParent();
  MachineFunction *MF = BB->getParent();
  MachineRegisterInfo &MRI = MF->getRegInfo();
  unsigned SubReg = TRI.getSubRegFromChannel(I.getOperand(3).getImm() / 32);
  DebugLoc DL = I.getDebugLoc();
  MachineInstr *Ins = BuildMI(*BB, &I, DL, TII.get(TargetOpcode::INSERT_SUBREG))
                               .addDef(I.getOperand(0).getReg())
                               .addReg(I.getOperand(1).getReg())
                               .addReg(I.getOperand(2).getReg())
                               .addImm(SubReg);

  for (const MachineOperand &MO : Ins->operands()) {
    if (!MO.isReg())
      continue;
    if (TargetRegisterInfo::isPhysicalRegister(MO.getReg()))
      continue;

    const TargetRegisterClass *RC =
            TRI.getConstrainedRegClassForOperand(MO, MRI);
    if (!RC)
      continue;
    RBI.constrainGenericRegister(MO.getReg(), *RC, MRI);
  }
  I.eraseFromParent();
  return true;
}

bool AMDGPUInstructionSelector::selectG_INTRINSIC(MachineInstr &I,
                                          CodeGenCoverage &CoverageInfo) const {
  unsigned IntrinsicID =  I.getOperand(I.getNumExplicitDefs()).getIntrinsicID();
  switch (IntrinsicID) {
  default:
    break;
  case Intrinsic::maxnum:
  case Intrinsic::minnum:
  case Intrinsic::amdgcn_cvt_pkrtz:
    return selectImpl(I, CoverageInfo);

  case Intrinsic::amdgcn_kernarg_segment_ptr: {
    MachineFunction *MF = I.getParent()->getParent();
    MachineRegisterInfo &MRI = MF->getRegInfo();
    const SIMachineFunctionInfo *MFI = MF->getInfo<SIMachineFunctionInfo>();
    const ArgDescriptor *InputPtrReg;
    const TargetRegisterClass *RC;
    const DebugLoc &DL = I.getDebugLoc();

    std::tie(InputPtrReg, RC)
      = MFI->getPreloadedValue(AMDGPUFunctionArgInfo::KERNARG_SEGMENT_PTR);
    if (!InputPtrReg)
      report_fatal_error("missing kernarg segment ptr");

    BuildMI(*I.getParent(), &I, DL, TII.get(AMDGPU::COPY))
      .add(I.getOperand(0))
      .addReg(MRI.getLiveInVirtReg(InputPtrReg->getRegister()));
    I.eraseFromParent();
    return true;
  }
  }
  return false;
}

static unsigned getV_CMPOpcode(CmpInst::Predicate P, unsigned Size) {
  assert(Size == 32 || Size == 64);
  switch (P) {
  default:
    llvm_unreachable("Unknown condition code!");
  case CmpInst::ICMP_NE:
    return Size == 32 ? AMDGPU::V_CMP_NE_U32_e64 : AMDGPU::V_CMP_NE_U64_e64;
  case CmpInst::ICMP_EQ:
    return Size == 32 ? AMDGPU::V_CMP_EQ_U32_e64 : AMDGPU::V_CMP_EQ_U64_e64;
  case CmpInst::ICMP_SGT:
    return Size == 32 ? AMDGPU::V_CMP_GT_I32_e64 : AMDGPU::V_CMP_GT_I64_e64;
  case CmpInst::ICMP_SGE:
    return Size == 32 ? AMDGPU::V_CMP_GE_I32_e64 : AMDGPU::V_CMP_GE_I64_e64;
  case CmpInst::ICMP_SLT:
    return Size == 32 ? AMDGPU::V_CMP_LT_I32_e64 : AMDGPU::V_CMP_LT_I64_e64;
  case CmpInst::ICMP_SLE:
    return Size == 32 ? AMDGPU::V_CMP_LE_I32_e64 : AMDGPU::V_CMP_LE_I64_e64;
  case CmpInst::ICMP_UGT:
    return Size == 32 ? AMDGPU::V_CMP_GT_U32_e64 : AMDGPU::V_CMP_GT_U64_e64;
  case CmpInst::ICMP_UGE:
    return Size == 32 ? AMDGPU::V_CMP_GE_U32_e64 : AMDGPU::V_CMP_GE_U64_e64;
  case CmpInst::ICMP_ULT:
    return Size == 32 ? AMDGPU::V_CMP_LT_U32_e64 : AMDGPU::V_CMP_LT_U64_e64;
  case CmpInst::ICMP_ULE:
    return Size == 32 ? AMDGPU::V_CMP_LE_U32_e64 : AMDGPU::V_CMP_LE_U64_e64;
  }
}

static unsigned getS_CMPOpcode(CmpInst::Predicate P, unsigned Size) {
  // FIXME: VI supports 64-bit comparse.
  assert(Size == 32);
  switch (P) {
  default:
    llvm_unreachable("Unknown condition code!");
  case CmpInst::ICMP_NE:
    return AMDGPU::S_CMP_LG_U32;
  case CmpInst::ICMP_EQ:
    return AMDGPU::S_CMP_EQ_U32;
  case CmpInst::ICMP_SGT:
    return AMDGPU::S_CMP_GT_I32;
  case CmpInst::ICMP_SGE:
    return AMDGPU::S_CMP_GE_I32;
  case CmpInst::ICMP_SLT:
    return AMDGPU::S_CMP_LT_I32;
  case CmpInst::ICMP_SLE:
    return AMDGPU::S_CMP_LE_I32;
  case CmpInst::ICMP_UGT:
    return AMDGPU::S_CMP_GT_U32;
  case CmpInst::ICMP_UGE:
    return AMDGPU::S_CMP_GE_U32;
  case CmpInst::ICMP_ULT:
    return AMDGPU::S_CMP_LT_U32;
  case CmpInst::ICMP_ULE:
    return AMDGPU::S_CMP_LE_U32;
  }
}

bool AMDGPUInstructionSelector::selectG_ICMP(MachineInstr &I) const {
  MachineBasicBlock *BB = I.getParent();
  MachineFunction *MF = BB->getParent();
  MachineRegisterInfo &MRI = MF->getRegInfo();
  DebugLoc DL = I.getDebugLoc();

  unsigned SrcReg = I.getOperand(2).getReg();
  unsigned Size = RBI.getSizeInBits(SrcReg, MRI, TRI);
  // FIXME: VI supports 64-bit compares.
  assert(Size == 32);

  unsigned CCReg = I.getOperand(0).getReg();
  if (isSCC(CCReg, MRI)) {
    unsigned Opcode = getS_CMPOpcode((CmpInst::Predicate)I.getOperand(1).getPredicate(), Size);
    MachineInstr *ICmp = BuildMI(*BB, &I, DL, TII.get(Opcode))
            .add(I.getOperand(2))
            .add(I.getOperand(3));
    BuildMI(*BB, &I, DL, TII.get(AMDGPU::COPY), CCReg)
      .addReg(AMDGPU::SCC);
    bool Ret =
        constrainSelectedInstRegOperands(*ICmp, TII, TRI, RBI) &&
        RBI.constrainGenericRegister(CCReg, AMDGPU::SReg_32RegClass, MRI);
    I.eraseFromParent();
    return Ret;
  }

  assert(Size == 32 || Size == 64);
  unsigned Opcode = getV_CMPOpcode((CmpInst::Predicate)I.getOperand(1).getPredicate(), Size);
  MachineInstr *ICmp = BuildMI(*BB, &I, DL, TII.get(Opcode),
            I.getOperand(0).getReg())
            .add(I.getOperand(2))
            .add(I.getOperand(3));
  RBI.constrainGenericRegister(ICmp->getOperand(0).getReg(),
                               AMDGPU::SReg_64RegClass, MRI);
  bool Ret = constrainSelectedInstRegOperands(*ICmp, TII, TRI, RBI);
  I.eraseFromParent();
  return Ret;
}

static MachineInstr *
buildEXP(const TargetInstrInfo &TII, MachineInstr *Insert, unsigned Tgt,
         unsigned Reg0, unsigned Reg1, unsigned Reg2, unsigned Reg3,
         unsigned VM, bool Compr, unsigned Enabled, bool Done) {
  const DebugLoc &DL = Insert->getDebugLoc();
  MachineBasicBlock &BB = *Insert->getParent();
  unsigned Opcode = Done ? AMDGPU::EXP_DONE : AMDGPU::EXP;
  return BuildMI(BB, Insert, DL, TII.get(Opcode))
          .addImm(Tgt)
          .addReg(Reg0)
          .addReg(Reg1)
          .addReg(Reg2)
          .addReg(Reg3)
          .addImm(VM)
          .addImm(Compr)
          .addImm(Enabled);
}

bool AMDGPUInstructionSelector::selectG_INTRINSIC_W_SIDE_EFFECTS(
                                                 MachineInstr &I,
						 CodeGenCoverage &CoverageInfo) const {
  MachineBasicBlock *BB = I.getParent();
  MachineFunction *MF = BB->getParent();
  MachineRegisterInfo &MRI = MF->getRegInfo();

  unsigned IntrinsicID = I.getOperand(0).getIntrinsicID();
  switch (IntrinsicID) {
  case Intrinsic::amdgcn_exp: {
    int64_t Tgt = getConstant(MRI.getVRegDef(I.getOperand(1).getReg()));
    int64_t Enabled = getConstant(MRI.getVRegDef(I.getOperand(2).getReg()));
    int64_t Done = getConstant(MRI.getVRegDef(I.getOperand(7).getReg()));
    int64_t VM = getConstant(MRI.getVRegDef(I.getOperand(8).getReg()));

    MachineInstr *Exp = buildEXP(TII, &I, Tgt, I.getOperand(3).getReg(),
                                 I.getOperand(4).getReg(),
                                 I.getOperand(5).getReg(),
                                 I.getOperand(6).getReg(),
                                 VM, false, Enabled, Done);

    I.eraseFromParent();
    return constrainSelectedInstRegOperands(*Exp, TII, TRI, RBI);
  }
  case Intrinsic::amdgcn_exp_compr: {
    const DebugLoc &DL = I.getDebugLoc();
    int64_t Tgt = getConstant(MRI.getVRegDef(I.getOperand(1).getReg()));
    int64_t Enabled = getConstant(MRI.getVRegDef(I.getOperand(2).getReg()));
    unsigned Reg0 = I.getOperand(3).getReg();
    unsigned Reg1 = I.getOperand(4).getReg();
    unsigned Undef = MRI.createVirtualRegister(&AMDGPU::VGPR_32RegClass);
    int64_t Done = getConstant(MRI.getVRegDef(I.getOperand(5).getReg()));
    int64_t VM = getConstant(MRI.getVRegDef(I.getOperand(6).getReg()));

    BuildMI(*BB, &I, DL, TII.get(AMDGPU::IMPLICIT_DEF), Undef);
    MachineInstr *Exp = buildEXP(TII, &I, Tgt, Reg0, Reg1, Undef, Undef, VM,
                                 true,  Enabled, Done);

    I.eraseFromParent();
    return constrainSelectedInstRegOperands(*Exp, TII, TRI, RBI);
  }
  }
  return false;
}

bool AMDGPUInstructionSelector::selectG_SELECT(MachineInstr &I) const {
  MachineBasicBlock *BB = I.getParent();
  MachineFunction *MF = BB->getParent();
  MachineRegisterInfo &MRI = MF->getRegInfo();
  const DebugLoc &DL = I.getDebugLoc();

  unsigned DstReg = I.getOperand(0).getReg();
  unsigned Size = RBI.getSizeInBits(DstReg, MRI, TRI);
  assert(Size == 32 || Size == 64);
  const MachineOperand &CCOp = I.getOperand(1);
  unsigned CCReg = CCOp.getReg();
  if (isSCC(CCReg, MRI)) {
    unsigned SelectOpcode = Size == 32 ? AMDGPU::S_CSELECT_B32 :
                                         AMDGPU::S_CSELECT_B64;
    MachineInstr *CopySCC = BuildMI(*BB, &I, DL, TII.get(AMDGPU::COPY), AMDGPU::SCC)
            .addReg(CCReg);

    // The generic constrainSelectedInstRegOperands doesn't work for the scc register
    // bank, because it does not cover the register class that we used to represent
    // for it.  So we need to manually set the register class here.
    if (!MRI.getRegClassOrNull(CCReg))
        MRI.setRegClass(CCReg, TRI.getConstrainedRegClassForOperand(CCOp, MRI));
    MachineInstr *Select = BuildMI(*BB, &I, DL, TII.get(SelectOpcode), DstReg)
            .add(I.getOperand(2))
            .add(I.getOperand(3));

    bool Ret = constrainSelectedInstRegOperands(*Select, TII, TRI, RBI) |
               constrainSelectedInstRegOperands(*CopySCC, TII, TRI, RBI);
    I.eraseFromParent();
    return Ret;
  }

  assert(Size == 32);
  // FIXME: Support 64-bit select
  MachineInstr *Select =
      BuildMI(*BB, &I, DL, TII.get(AMDGPU::V_CNDMASK_B32_e64), DstReg)
              .addImm(0)
              .add(I.getOperand(3))
              .addImm(0)
              .add(I.getOperand(2))
              .add(I.getOperand(1));

  bool Ret = constrainSelectedInstRegOperands(*Select, TII, TRI, RBI);
  I.eraseFromParent();
  return Ret;
}

bool AMDGPUInstructionSelector::selectG_STORE(MachineInstr &I) const {
  MachineBasicBlock *BB = I.getParent();
  MachineFunction *MF = BB->getParent();
  MachineRegisterInfo &MRI = MF->getRegInfo();
  DebugLoc DL = I.getDebugLoc();
  unsigned StoreSize = RBI.getSizeInBits(I.getOperand(0).getReg(), MRI, TRI);
  unsigned Opcode;

  // FIXME: Select store instruction based on address space
  switch (StoreSize) {
  default:
    return false;
  case 32:
    Opcode = AMDGPU::FLAT_STORE_DWORD;
    break;
  case 64:
    Opcode = AMDGPU::FLAT_STORE_DWORDX2;
    break;
  case 96:
    Opcode = AMDGPU::FLAT_STORE_DWORDX3;
    break;
  case 128:
    Opcode = AMDGPU::FLAT_STORE_DWORDX4;
    break;
  }

  MachineInstr *Flat = BuildMI(*BB, &I, DL, TII.get(Opcode))
          .add(I.getOperand(1))
          .add(I.getOperand(0))
          .addImm(0)  // offset
          .addImm(0)  // glc
          .addImm(0)  // slc
          .addImm(0); // dlc


  // Now that we selected an opcode, we need to constrain the register
  // operands to use appropriate classes.
  bool Ret = constrainSelectedInstRegOperands(*Flat, TII, TRI, RBI);

  I.eraseFromParent();
  return Ret;
}

static int sizeToSubRegIndex(unsigned Size) {
  switch (Size) {
  case 32:
    return AMDGPU::sub0;
  case 64:
    return AMDGPU::sub0_sub1;
  case 96:
    return AMDGPU::sub0_sub1_sub2;
  case 128:
    return AMDGPU::sub0_sub1_sub2_sub3;
  case 256:
    return AMDGPU::sub0_sub1_sub2_sub3_sub4_sub5_sub6_sub7;
  default:
    if (Size < 32)
      return AMDGPU::sub0;
    if (Size > 256)
      return -1;
    return sizeToSubRegIndex(PowerOf2Ceil(Size));
  }
}

bool AMDGPUInstructionSelector::selectG_TRUNC(MachineInstr &I) const {
  MachineBasicBlock *BB = I.getParent();
  MachineFunction *MF = BB->getParent();
  MachineRegisterInfo &MRI = MF->getRegInfo();

  unsigned DstReg = I.getOperand(0).getReg();
  unsigned SrcReg = I.getOperand(1).getReg();
  const LLT DstTy = MRI.getType(DstReg);
  const LLT SrcTy = MRI.getType(SrcReg);
  if (!DstTy.isScalar())
    return false;

  const RegisterBank *DstRB = RBI.getRegBank(DstReg, MRI, TRI);
  const RegisterBank *SrcRB = RBI.getRegBank(SrcReg, MRI, TRI);
  if (SrcRB != DstRB)
    return false;

  unsigned DstSize = DstTy.getSizeInBits();
  unsigned SrcSize = SrcTy.getSizeInBits();

  const TargetRegisterClass *SrcRC
    = TRI.getRegClassForSizeOnBank(SrcSize, *SrcRB, MRI);
  const TargetRegisterClass *DstRC
    = TRI.getRegClassForSizeOnBank(DstSize, *DstRB, MRI);

  if (SrcSize > 32) {
    int SubRegIdx = sizeToSubRegIndex(DstSize);
    if (SubRegIdx == -1)
      return false;

    // Deal with weird cases where the class only partially supports the subreg
    // index.
    SrcRC = TRI.getSubClassWithSubReg(SrcRC, SubRegIdx);
    if (!SrcRC)
      return false;

    I.getOperand(1).setSubReg(SubRegIdx);
  }

  if (!RBI.constrainGenericRegister(SrcReg, *SrcRC, MRI) ||
      !RBI.constrainGenericRegister(DstReg, *DstRC, MRI)) {
    LLVM_DEBUG(dbgs() << "Failed to constrain G_TRUNC\n");
    return false;
  }

  I.setDesc(TII.get(TargetOpcode::COPY));
  return true;
}

bool AMDGPUInstructionSelector::selectG_SZA_EXT(MachineInstr &I) const {
  bool Signed = I.getOpcode() == AMDGPU::G_SEXT;
  const DebugLoc &DL = I.getDebugLoc();
  MachineBasicBlock &MBB = *I.getParent();
  MachineFunction &MF = *MBB.getParent();
  MachineRegisterInfo &MRI = MF.getRegInfo();
  const unsigned DstReg = I.getOperand(0).getReg();
  const unsigned SrcReg = I.getOperand(1).getReg();

  const LLT DstTy = MRI.getType(DstReg);
  const LLT SrcTy = MRI.getType(SrcReg);
  const LLT S1 = LLT::scalar(1);
  const unsigned SrcSize = SrcTy.getSizeInBits();
  const unsigned DstSize = DstTy.getSizeInBits();
  if (!DstTy.isScalar())
    return false;

  const RegisterBank *SrcBank = RBI.getRegBank(SrcReg, MRI, TRI);

  if (SrcBank->getID() == AMDGPU::SCCRegBankID) {
    if (SrcTy != S1 || DstSize > 64) // Invalid
      return false;

    unsigned Opcode =
        DstSize > 32 ? AMDGPU::S_CSELECT_B64 : AMDGPU::S_CSELECT_B32;
    const TargetRegisterClass *DstRC =
        DstSize > 32 ? &AMDGPU::SReg_64RegClass : &AMDGPU::SReg_32RegClass;

    // FIXME: Create an extra copy to avoid incorrectly constraining the result
    // of the scc producer.
    unsigned TmpReg = MRI.createVirtualRegister(&AMDGPU::SReg_32RegClass);
    BuildMI(MBB, I, DL, TII.get(AMDGPU::COPY), TmpReg)
      .addReg(SrcReg);
    BuildMI(MBB, I, DL, TII.get(AMDGPU::COPY), AMDGPU::SCC)
      .addReg(TmpReg);

    // The instruction operands are backwards from what you would expect.
    BuildMI(MBB, I, DL, TII.get(Opcode), DstReg)
      .addImm(0)
      .addImm(Signed ? -1 : 1);
    return RBI.constrainGenericRegister(DstReg, *DstRC, MRI);
  }

  if (SrcBank->getID() == AMDGPU::VCCRegBankID && DstSize <= 32) {
    if (SrcTy != S1) // Invalid
      return false;

    MachineInstr *ExtI =
      BuildMI(MBB, I, DL, TII.get(AMDGPU::V_CNDMASK_B32_e64), DstReg)
      .addImm(0)               // src0_modifiers
      .addImm(0)               // src0
      .addImm(0)               // src1_modifiers
      .addImm(Signed ? -1 : 1) // src1
      .addUse(SrcReg);
    return constrainSelectedInstRegOperands(*ExtI, TII, TRI, RBI);
  }

  if (I.getOpcode() == AMDGPU::G_ANYEXT)
    return selectCOPY(I);

  if (SrcBank->getID() == AMDGPU::VGPRRegBankID && DstSize <= 32) {
    // 64-bit should have been split up in RegBankSelect
    //
    // TODO: USE V_AND_B32 when the constant mask is an inline immediate for
    // unsigned for smaller code size.
    const unsigned BFE = Signed ? AMDGPU::V_BFE_I32 : AMDGPU::V_BFE_U32;
    MachineInstr *ExtI =
      BuildMI(MBB, I, DL, TII.get(BFE), DstReg)
      .addReg(SrcReg)
      .addImm(0) // Offset
      .addImm(SrcSize); // Width
    return constrainSelectedInstRegOperands(*ExtI, TII, TRI, RBI);
  }

  if (SrcBank->getID() == AMDGPU::SGPRRegBankID && DstSize <= 64) {
    if (!RBI.constrainGenericRegister(SrcReg, AMDGPU::SReg_32RegClass, MRI))
      return false;

    if (Signed && DstSize == 32 && (SrcSize == 8 || SrcSize == 16)) {
      const unsigned SextOpc = SrcSize == 8 ?
        AMDGPU::S_SEXT_I32_I8 : AMDGPU::S_SEXT_I32_I16;
      BuildMI(MBB, I, DL, TII.get(SextOpc), DstReg)
        .addReg(SrcReg);
      return RBI.constrainGenericRegister(DstReg, AMDGPU::SReg_32RegClass, MRI);
    }

    const unsigned BFE64 = Signed ? AMDGPU::S_BFE_I64 : AMDGPU::S_BFE_U64;
    const unsigned BFE32 = Signed ? AMDGPU::S_BFE_I32 : AMDGPU::S_BFE_U32;

    // Scalar BFE is encoded as S1[5:0] = offset, S1[22:16]= width.
    if (DstSize > 32 && SrcSize <= 32) {
      // We need a 64-bit register source, but the high bits don't matter.
      unsigned ExtReg
        = MRI.createVirtualRegister(&AMDGPU::SReg_64RegClass);
      unsigned UndefReg
        = MRI.createVirtualRegister(&AMDGPU::SReg_32RegClass);
      BuildMI(MBB, I, DL, TII.get(AMDGPU::IMPLICIT_DEF), UndefReg);
      BuildMI(MBB, I, DL, TII.get(AMDGPU::REG_SEQUENCE), ExtReg)
        .addReg(SrcReg)
        .addImm(AMDGPU::sub0)
        .addReg(UndefReg)
        .addImm(AMDGPU::sub1);

      BuildMI(MBB, I, DL, TII.get(BFE64), DstReg)
        .addReg(ExtReg)
        .addImm(SrcSize << 16);

      return RBI.constrainGenericRegister(DstReg, AMDGPU::SReg_64RegClass, MRI);
    }

    BuildMI(MBB, I, DL, TII.get(BFE32), DstReg)
      .addReg(SrcReg)
      .addImm(SrcSize << 16);
    return RBI.constrainGenericRegister(DstReg, AMDGPU::SReg_32RegClass, MRI);
  }

  return false;
}

bool AMDGPUInstructionSelector::selectG_CONSTANT(MachineInstr &I) const {
  MachineBasicBlock *BB = I.getParent();
  MachineFunction *MF = BB->getParent();
  MachineRegisterInfo &MRI = MF->getRegInfo();
  MachineOperand &ImmOp = I.getOperand(1);

  // The AMDGPU backend only supports Imm operands and not CImm or FPImm.
  if (ImmOp.isFPImm()) {
    const APInt &Imm = ImmOp.getFPImm()->getValueAPF().bitcastToAPInt();
    ImmOp.ChangeToImmediate(Imm.getZExtValue());
  } else if (ImmOp.isCImm()) {
    ImmOp.ChangeToImmediate(ImmOp.getCImm()->getZExtValue());
  }

  unsigned DstReg = I.getOperand(0).getReg();
  unsigned Size;
  bool IsSgpr;
  const RegisterBank *RB = MRI.getRegBankOrNull(I.getOperand(0).getReg());
  if (RB) {
    IsSgpr = RB->getID() == AMDGPU::SGPRRegBankID;
    Size = MRI.getType(DstReg).getSizeInBits();
  } else {
    const TargetRegisterClass *RC = TRI.getRegClassForReg(MRI, DstReg);
    IsSgpr = TRI.isSGPRClass(RC);
    Size = TRI.getRegSizeInBits(*RC);
  }

  if (Size != 32 && Size != 64)
    return false;

  unsigned Opcode = IsSgpr ? AMDGPU::S_MOV_B32 : AMDGPU::V_MOV_B32_e32;
  if (Size == 32) {
    I.setDesc(TII.get(Opcode));
    I.addImplicitDefUseOperands(*MF);
    return constrainSelectedInstRegOperands(I, TII, TRI, RBI);
  }

  DebugLoc DL = I.getDebugLoc();
  const TargetRegisterClass *RC = IsSgpr ? &AMDGPU::SReg_32_XM0RegClass :
                                           &AMDGPU::VGPR_32RegClass;
  unsigned LoReg = MRI.createVirtualRegister(RC);
  unsigned HiReg = MRI.createVirtualRegister(RC);
  const APInt &Imm = APInt(Size, I.getOperand(1).getImm());

  BuildMI(*BB, &I, DL, TII.get(Opcode), LoReg)
          .addImm(Imm.trunc(32).getZExtValue());

  BuildMI(*BB, &I, DL, TII.get(Opcode), HiReg)
          .addImm(Imm.ashr(32).getZExtValue());

  const MachineInstr *RS =
      BuildMI(*BB, &I, DL, TII.get(AMDGPU::REG_SEQUENCE), DstReg)
              .addReg(LoReg)
              .addImm(AMDGPU::sub0)
              .addReg(HiReg)
              .addImm(AMDGPU::sub1);

  // We can't call constrainSelectedInstRegOperands here, because it doesn't
  // work for target independent opcodes
  I.eraseFromParent();
  const TargetRegisterClass *DstRC =
      TRI.getConstrainedRegClassForOperand(RS->getOperand(0), MRI);
  if (!DstRC)
    return true;
  return RBI.constrainGenericRegister(DstReg, *DstRC, MRI);
}

static bool isConstant(const MachineInstr &MI) {
  return MI.getOpcode() == TargetOpcode::G_CONSTANT;
}

void AMDGPUInstructionSelector::getAddrModeInfo(const MachineInstr &Load,
    const MachineRegisterInfo &MRI, SmallVectorImpl<GEPInfo> &AddrInfo) const {

  const MachineInstr *PtrMI = MRI.getUniqueVRegDef(Load.getOperand(1).getReg());

  assert(PtrMI);

  if (PtrMI->getOpcode() != TargetOpcode::G_GEP)
    return;

  GEPInfo GEPInfo(*PtrMI);

  for (unsigned i = 1, e = 3; i < e; ++i) {
    const MachineOperand &GEPOp = PtrMI->getOperand(i);
    const MachineInstr *OpDef = MRI.getUniqueVRegDef(GEPOp.getReg());
    assert(OpDef);
    if (isConstant(*OpDef)) {
      // FIXME: Is it possible to have multiple Imm parts?  Maybe if we
      // are lacking other optimizations.
      assert(GEPInfo.Imm == 0);
      GEPInfo.Imm = OpDef->getOperand(1).getCImm()->getSExtValue();
      continue;
    }
    const RegisterBank *OpBank = RBI.getRegBank(GEPOp.getReg(), MRI, TRI);
    if (OpBank->getID() == AMDGPU::SGPRRegBankID)
      GEPInfo.SgprParts.push_back(GEPOp.getReg());
    else
      GEPInfo.VgprParts.push_back(GEPOp.getReg());
  }

  AddrInfo.push_back(GEPInfo);
  getAddrModeInfo(*PtrMI, MRI, AddrInfo);
}

bool AMDGPUInstructionSelector::isInstrUniform(const MachineInstr &MI) const {
  if (!MI.hasOneMemOperand())
    return false;

  const MachineMemOperand *MMO = *MI.memoperands_begin();
  const Value *Ptr = MMO->getValue();

  // UndefValue means this is a load of a kernel input.  These are uniform.
  // Sometimes LDS instructions have constant pointers.
  // If Ptr is null, then that means this mem operand contains a
  // PseudoSourceValue like GOT.
  if (!Ptr || isa<UndefValue>(Ptr) || isa<Argument>(Ptr) ||
      isa<Constant>(Ptr) || isa<GlobalValue>(Ptr))
    return true;

  if (MMO->getAddrSpace() == AMDGPUAS::CONSTANT_ADDRESS_32BIT)
    return true;

  const Instruction *I = dyn_cast<Instruction>(Ptr);
  return I && I->getMetadata("amdgpu.uniform");
}

bool AMDGPUInstructionSelector::hasVgprParts(ArrayRef<GEPInfo> AddrInfo) const {
  for (const GEPInfo &GEPInfo : AddrInfo) {
    if (!GEPInfo.VgprParts.empty())
      return true;
  }
  return false;
}

bool AMDGPUInstructionSelector::selectG_LOAD(MachineInstr &I) const {
  MachineBasicBlock *BB = I.getParent();
  MachineFunction *MF = BB->getParent();
  MachineRegisterInfo &MRI = MF->getRegInfo();
  DebugLoc DL = I.getDebugLoc();
  unsigned DstReg = I.getOperand(0).getReg();
  unsigned PtrReg = I.getOperand(1).getReg();
  unsigned LoadSize = RBI.getSizeInBits(DstReg, MRI, TRI);
  unsigned Opcode;

  SmallVector<GEPInfo, 4> AddrInfo;

  getAddrModeInfo(I, MRI, AddrInfo);

  switch (LoadSize) {
  default:
    llvm_unreachable("Load size not supported\n");
  case 32:
    Opcode = AMDGPU::FLAT_LOAD_DWORD;
    break;
  case 64:
    Opcode = AMDGPU::FLAT_LOAD_DWORDX2;
    break;
  }

  MachineInstr *Flat = BuildMI(*BB, &I, DL, TII.get(Opcode))
                               .add(I.getOperand(0))
                               .addReg(PtrReg)
                               .addImm(0)  // offset
                               .addImm(0)  // glc
                               .addImm(0)  // slc
                               .addImm(0); // dlc

  bool Ret = constrainSelectedInstRegOperands(*Flat, TII, TRI, RBI);
  I.eraseFromParent();
  return Ret;
}

bool AMDGPUInstructionSelector::select(MachineInstr &I,
                                       CodeGenCoverage &CoverageInfo) const {

  if (!isPreISelGenericOpcode(I.getOpcode())) {
    if (I.isCopy())
      return selectCOPY(I);
    return true;
  }

  switch (I.getOpcode()) {
  default:
    return selectImpl(I, CoverageInfo);
  case TargetOpcode::G_ADD:
    return selectG_ADD(I);
  case TargetOpcode::G_INTTOPTR:
  case TargetOpcode::G_BITCAST:
    return selectCOPY(I);
  case TargetOpcode::G_CONSTANT:
  case TargetOpcode::G_FCONSTANT:
    return selectG_CONSTANT(I);
  case TargetOpcode::G_EXTRACT:
    return selectG_EXTRACT(I);
  case TargetOpcode::G_GEP:
    return selectG_GEP(I);
  case TargetOpcode::G_IMPLICIT_DEF:
    return selectG_IMPLICIT_DEF(I);
  case TargetOpcode::G_INSERT:
    return selectG_INSERT(I);
  case TargetOpcode::G_INTRINSIC:
    return selectG_INTRINSIC(I, CoverageInfo);
  case TargetOpcode::G_INTRINSIC_W_SIDE_EFFECTS:
    return selectG_INTRINSIC_W_SIDE_EFFECTS(I, CoverageInfo);
  case TargetOpcode::G_ICMP:
    return selectG_ICMP(I);
  case TargetOpcode::G_LOAD:
    if (selectImpl(I, CoverageInfo))
      return true;
    return selectG_LOAD(I);
  case TargetOpcode::G_SELECT:
    return selectG_SELECT(I);
  case TargetOpcode::G_STORE:
    return selectG_STORE(I);
  case TargetOpcode::G_TRUNC:
    return selectG_TRUNC(I);
  case TargetOpcode::G_SEXT:
  case TargetOpcode::G_ZEXT:
  case TargetOpcode::G_ANYEXT:
    if (selectG_SZA_EXT(I)) {
      I.eraseFromParent();
      return true;
    }

    return false;
  }
  return false;
}

InstructionSelector::ComplexRendererFns
AMDGPUInstructionSelector::selectVCSRC(MachineOperand &Root) const {
  return {{
      [=](MachineInstrBuilder &MIB) { MIB.add(Root); }
  }};

}

///
/// This will select either an SGPR or VGPR operand and will save us from
/// having to write an extra tablegen pattern.
InstructionSelector::ComplexRendererFns
AMDGPUInstructionSelector::selectVSRC0(MachineOperand &Root) const {
  return {{
      [=](MachineInstrBuilder &MIB) { MIB.add(Root); }
  }};
}

InstructionSelector::ComplexRendererFns
AMDGPUInstructionSelector::selectVOP3Mods0(MachineOperand &Root) const {
  return {{
      [=](MachineInstrBuilder &MIB) { MIB.add(Root); },
      [=](MachineInstrBuilder &MIB) { MIB.addImm(0); }, // src0_mods
      [=](MachineInstrBuilder &MIB) { MIB.addImm(0); }, // clamp
      [=](MachineInstrBuilder &MIB) { MIB.addImm(0); }  // omod
  }};
}
InstructionSelector::ComplexRendererFns
AMDGPUInstructionSelector::selectVOP3OMods(MachineOperand &Root) const {
  return {{
      [=](MachineInstrBuilder &MIB) { MIB.add(Root); },
      [=](MachineInstrBuilder &MIB) { MIB.addImm(0); }, // clamp
      [=](MachineInstrBuilder &MIB) { MIB.addImm(0); }  // omod
  }};
}

InstructionSelector::ComplexRendererFns
AMDGPUInstructionSelector::selectVOP3Mods(MachineOperand &Root) const {
  return {{
      [=](MachineInstrBuilder &MIB) { MIB.add(Root); },
      [=](MachineInstrBuilder &MIB) { MIB.addImm(0); }  // src_mods
  }};
}

InstructionSelector::ComplexRendererFns
AMDGPUInstructionSelector::selectSmrdImm(MachineOperand &Root) const {
  MachineRegisterInfo &MRI =
      Root.getParent()->getParent()->getParent()->getRegInfo();

  SmallVector<GEPInfo, 4> AddrInfo;
  getAddrModeInfo(*Root.getParent(), MRI, AddrInfo);

  if (AddrInfo.empty() || AddrInfo[0].SgprParts.size() != 1)
    return None;

  const GEPInfo &GEPInfo = AddrInfo[0];

  if (!AMDGPU::isLegalSMRDImmOffset(STI, GEPInfo.Imm))
    return None;

  unsigned PtrReg = GEPInfo.SgprParts[0];
  int64_t EncodedImm = AMDGPU::getSMRDEncodedOffset(STI, GEPInfo.Imm);
  return {{
    [=](MachineInstrBuilder &MIB) { MIB.addReg(PtrReg); },
    [=](MachineInstrBuilder &MIB) { MIB.addImm(EncodedImm); }
  }};
}

InstructionSelector::ComplexRendererFns
AMDGPUInstructionSelector::selectSmrdImm32(MachineOperand &Root) const {
  MachineRegisterInfo &MRI =
      Root.getParent()->getParent()->getParent()->getRegInfo();

  SmallVector<GEPInfo, 4> AddrInfo;
  getAddrModeInfo(*Root.getParent(), MRI, AddrInfo);

  if (AddrInfo.empty() || AddrInfo[0].SgprParts.size() != 1)
    return None;

  const GEPInfo &GEPInfo = AddrInfo[0];
  unsigned PtrReg = GEPInfo.SgprParts[0];
  int64_t EncodedImm = AMDGPU::getSMRDEncodedOffset(STI, GEPInfo.Imm);
  if (!isUInt<32>(EncodedImm))
    return None;

  return {{
    [=](MachineInstrBuilder &MIB) { MIB.addReg(PtrReg); },
    [=](MachineInstrBuilder &MIB) { MIB.addImm(EncodedImm); }
  }};
}

InstructionSelector::ComplexRendererFns
AMDGPUInstructionSelector::selectSmrdSgpr(MachineOperand &Root) const {
  MachineInstr *MI = Root.getParent();
  MachineBasicBlock *MBB = MI->getParent();
  MachineRegisterInfo &MRI = MBB->getParent()->getRegInfo();

  SmallVector<GEPInfo, 4> AddrInfo;
  getAddrModeInfo(*MI, MRI, AddrInfo);

  // FIXME: We should shrink the GEP if the offset is known to be <= 32-bits,
  // then we can select all ptr + 32-bit offsets not just immediate offsets.
  if (AddrInfo.empty() || AddrInfo[0].SgprParts.size() != 1)
    return None;

  const GEPInfo &GEPInfo = AddrInfo[0];
  if (!GEPInfo.Imm || !isUInt<32>(GEPInfo.Imm))
    return None;

  // If we make it this far we have a load with an 32-bit immediate offset.
  // It is OK to select this using a sgpr offset, because we have already
  // failed trying to select this load into one of the _IMM variants since
  // the _IMM Patterns are considered before the _SGPR patterns.
  unsigned PtrReg = GEPInfo.SgprParts[0];
  unsigned OffsetReg = MRI.createVirtualRegister(&AMDGPU::SReg_32_XM0RegClass);
  BuildMI(*MBB, MI, MI->getDebugLoc(), TII.get(AMDGPU::S_MOV_B32), OffsetReg)
          .addImm(GEPInfo.Imm);
  return {{
    [=](MachineInstrBuilder &MIB) { MIB.addReg(PtrReg); },
    [=](MachineInstrBuilder &MIB) { MIB.addReg(OffsetReg); }
  }};
}