SIFrameLowering.cpp

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//===----------------------- SIFrameLowering.cpp --------------------------===//
//
// 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
//
//==-----------------------------------------------------------------------===//
 
#include "SIFrameLowering.h"
#include "AMDGPU.h"
#include "AMDGPULaneMaskUtils.h"
#include "GCNSubtarget.h"
#include "MCTargetDesc/AMDGPUMCTargetDesc.h"
#include "SIMachineFunctionInfo.h"
#include "SISpillUtils.h"
#include "llvm/BinaryFormat/Dwarf.h"
#include "llvm/CodeGen/LiveRegUnits.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/RegisterScavenging.h"
#include "llvm/Support/LEB128.h"
#include "llvm/Target/TargetMachine.h"
 
using namespace llvm;
 
#define DEBUG_TYPE "frame-info"
 
static cl::opt<bool> EnableSpillVGPRToAGPR(
  "amdgpu-spill-vgpr-to-agpr",
  cl::desc("Enable spilling VGPRs to AGPRs"),
  cl::ReallyHidden,
  cl::init(true));
 
static constexpr unsigned SGPRBitSize = 32;
static constexpr unsigned SGPRByteSize = SGPRBitSize / 8;
static constexpr unsigned VGPRLaneBitSize = 32;
 
// Find a register matching \p RC from \p LiveUnits which is unused and
// available throughout the function. On failure, returns AMDGPU::NoRegister.
// TODO: Rewrite the loop here to iterate over MCRegUnits instead of
// MCRegisters. This should reduce the number of iterations and avoid redundant
// checking.
static MCRegister findUnusedRegister(MachineRegisterInfo &MRI,
                                     const LiveRegUnits &LiveUnits,
                                     const TargetRegisterClass &RC) {
  for (MCRegister Reg : RC) {
    if (!MRI.isPhysRegUsed(Reg) && LiveUnits.available(Reg) &&
        !MRI.isReserved(Reg))
      return Reg;
  }
  return MCRegister();
}
 
static void encodeDwarfRegisterLocation(int DwarfReg, raw_ostream &OS) {
  assert(DwarfReg >= 0);
  if (DwarfReg < 32) {
    OS << uint8_t(dwarf::DW_OP_reg0 + DwarfReg);
  } else {
    OS << uint8_t(dwarf::DW_OP_regx);
    encodeULEB128(DwarfReg, OS);
  }
}
 
static MCCFIInstruction
createScaledCFAInPrivateWave(const GCNSubtarget &ST,
                             MCRegister DwarfStackPtrReg) {
  assert(ST.enableFlatScratch());
 
  // When flat scratch is enabled, the stack pointer is an address in the
  // private_lane DWARF address space (i.e. swizzled), but in order to
  // accurately and efficiently describe things like masked spills of vector
  // registers we want to define the CFA to be an address in the private_wave
  // DWARF address space (i.e. unswizzled). To achieve this we scale the stack
  // pointer by the wavefront size, implemented as (SP << wave_size_log2).
  const unsigned WavefrontSizeLog2 = ST.getWavefrontSizeLog2();
  assert(WavefrontSizeLog2 < 32);
 
  SmallString<20> Block;
  raw_svector_ostream OSBlock(Block);
  encodeDwarfRegisterLocation(DwarfStackPtrReg, OSBlock);
  OSBlock << uint8_t(dwarf::DW_OP_deref_size) << uint8_t(SGPRByteSize)
          << uint8_t(dwarf::DW_OP_lit0 + WavefrontSizeLog2)
          << uint8_t(dwarf::DW_OP_shl)
          << uint8_t(dwarf::DW_OP_lit0 +
                     dwarf::DW_ASPACE_LLVM_AMDGPU_private_wave)
          << uint8_t(dwarf::DW_OP_LLVM_user)
          << uint8_t(dwarf::DW_OP_LLVM_form_aspace_address);
 
  SmallString<20> CFIInst;
  raw_svector_ostream OSCFIInst(CFIInst);
  OSCFIInst << uint8_t(dwarf::DW_CFA_def_cfa_expression);
  encodeULEB128(Block.size(), OSCFIInst);
  OSCFIInst << Block;
 
  return MCCFIInstruction::createEscape(nullptr, OSCFIInst.str());
}
 
void SIFrameLowering::emitDefCFA(MachineBasicBlock &MBB,
                                 MachineBasicBlock::iterator MBBI,
                                 DebugLoc const &DL, MCRegister StackPtrReg,
                                 bool AspaceAlreadyDefined,
                                 MachineInstr::MIFlag Flags) const {
  MachineFunction &MF = *MBB.getParent();
  const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
  const SIRegisterInfo *TRI = ST.getRegisterInfo();
 
  MCRegister DwarfStackPtrReg = TRI->getDwarfRegNum(StackPtrReg, false);
  MCCFIInstruction CFIInst =
      ST.enableFlatScratch()
          ? createScaledCFAInPrivateWave(ST, DwarfStackPtrReg)
          : (AspaceAlreadyDefined
                 ? MCCFIInstruction::createLLVMDefAspaceCfa(
                       nullptr, DwarfStackPtrReg, 0,
                       dwarf::DW_ASPACE_LLVM_AMDGPU_private_wave, SMLoc())
                 : MCCFIInstruction::createDefCfaRegister(nullptr,
                                                          DwarfStackPtrReg));
  buildCFI(MBB, MBBI, DL, CFIInst, Flags);
}
 
// Find a scratch register that we can use in the prologue. We avoid using
// callee-save registers since they may appear to be free when this is called
// from canUseAsPrologue (during shrink wrapping), but then no longer be free
// when this is called from emitPrologue.
static MCRegister findScratchNonCalleeSaveRegister(
    MachineRegisterInfo &MRI, LiveRegUnits &LiveUnits,
    const TargetRegisterClass &RC, bool Unused = false) {
  // Mark callee saved registers as used so we will not choose them.
  const MCPhysReg *CSRegs = MRI.getCalleeSavedRegs();
  for (unsigned i = 0; CSRegs[i]; ++i)
    LiveUnits.addReg(CSRegs[i]);
 
  // We are looking for a register that can be used throughout the entire
  // function, so any use is unacceptable.
  if (Unused)
    return findUnusedRegister(MRI, LiveUnits, RC);
 
  for (MCRegister Reg : RC) {
    if (LiveUnits.available(Reg) && !MRI.isReserved(Reg))
      return Reg;
  }
 
  return MCRegister();
}
 
/// Query target location for spilling SGPRs
/// \p IncludeScratchCopy : Also look for free scratch SGPRs
static void getVGPRSpillLaneOrTempRegister(
    MachineFunction &MF, LiveRegUnits &LiveUnits, Register SGPR,
    const TargetRegisterClass &RC = AMDGPU::SReg_32_XM0_XEXECRegClass,
    bool IncludeScratchCopy = true) {
  SIMachineFunctionInfo *MFI = MF.getInfo<SIMachineFunctionInfo>();
  MachineFrameInfo &FrameInfo = MF.getFrameInfo();
 
  const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
  const SIRegisterInfo *TRI = ST.getRegisterInfo();
  unsigned Size = TRI->getSpillSize(RC);
  Align Alignment = TRI->getSpillAlign(RC);
 
  // We need to save and restore the given SGPR.
 
  Register ScratchSGPR;
  // 1: Try to save the given register into an unused scratch SGPR. The
  // LiveUnits should have all the callee saved registers marked as used. For
  // certain cases we skip copy to scratch SGPR.
  if (IncludeScratchCopy)
    ScratchSGPR = findUnusedRegister(MF.getRegInfo(), LiveUnits, RC);
 
  if (!ScratchSGPR) {
    int FI = FrameInfo.CreateStackObject(Size, Alignment, true, nullptr,
                                         TargetStackID::SGPRSpill);
 
    if (TRI->spillSGPRToVGPR() &&
        MFI->allocateSGPRSpillToVGPRLane(MF, FI, /*SpillToPhysVGPRLane=*/true,
                                         /*IsPrologEpilog=*/true)) {
      // 2: There's no free lane to spill, and no free register to save the
      // SGPR, so we're forced to take another VGPR to use for the spill.
      MFI->addToPrologEpilogSGPRSpills(
          SGPR, PrologEpilogSGPRSaveRestoreInfo(
                    SGPRSaveKind::SPILL_TO_VGPR_LANE, FI));
 
      LLVM_DEBUG(auto Spill = MFI->getSGPRSpillToPhysicalVGPRLanes(FI).front();
                 dbgs() << printReg(SGPR, TRI) << " requires fallback spill to "
                        << printReg(Spill.VGPR, TRI) << ':' << Spill.Lane
                        << '\n';);
    } else {
      // Remove dead <FI> index
      MF.getFrameInfo().RemoveStackObject(FI);
      // 3: If all else fails, spill the register to memory.
      FI = FrameInfo.CreateSpillStackObject(Size, Alignment);
      MFI->addToPrologEpilogSGPRSpills(
          SGPR,
          PrologEpilogSGPRSaveRestoreInfo(SGPRSaveKind::SPILL_TO_MEM, FI));
      LLVM_DEBUG(dbgs() << "Reserved FI " << FI << " for spilling "
                        << printReg(SGPR, TRI) << '\n');
    }
  } else {
    MFI->addToPrologEpilogSGPRSpills(
        SGPR, PrologEpilogSGPRSaveRestoreInfo(
                  SGPRSaveKind::COPY_TO_SCRATCH_SGPR, ScratchSGPR));
    LiveUnits.addReg(ScratchSGPR);
    LLVM_DEBUG(dbgs() << "Saving " << printReg(SGPR, TRI) << " with copy to "
                      << printReg(ScratchSGPR, TRI) << '\n');
  }
}
 
// We need to specially emit stack operations here because a different frame
// register is used than in the rest of the function, as getFrameRegister would
// use.
static void buildPrologSpill(const GCNSubtarget &ST, const SIRegisterInfo &TRI,
                             const SIMachineFunctionInfo &FuncInfo,
                             LiveRegUnits &LiveUnits, MachineFunction &MF,
                             MachineBasicBlock &MBB,
                             MachineBasicBlock::iterator I, const DebugLoc &DL,
                             Register SpillReg, int FI, Register FrameReg,
                             int64_t DwordOff = 0) {
  unsigned Opc = ST.hasFlatScratchEnabled() ? AMDGPU::SCRATCH_STORE_DWORD_SADDR
                                            : AMDGPU::BUFFER_STORE_DWORD_OFFSET;
 
  MachineFrameInfo &FrameInfo = MF.getFrameInfo();
  MachinePointerInfo PtrInfo = MachinePointerInfo::getFixedStack(MF, FI);
  MachineMemOperand *MMO = MF.getMachineMemOperand(
      PtrInfo, MachineMemOperand::MOStore, FrameInfo.getObjectSize(FI),
      FrameInfo.getObjectAlign(FI));
  LiveUnits.addReg(SpillReg);
  bool IsKill = !MBB.isLiveIn(SpillReg);
  TRI.buildSpillLoadStore(MBB, I, DL, Opc, FI, SpillReg, IsKill, FrameReg,
                          DwordOff, MMO, nullptr, &LiveUnits);
  if (IsKill)
    LiveUnits.removeReg(SpillReg);
}
 
static void buildEpilogRestore(const GCNSubtarget &ST,
                               const SIRegisterInfo &TRI,
                               const SIMachineFunctionInfo &FuncInfo,
                               LiveRegUnits &LiveUnits, MachineFunction &MF,
                               MachineBasicBlock &MBB,
                               MachineBasicBlock::iterator I,
                               const DebugLoc &DL, Register SpillReg, int FI,
                               Register FrameReg, int64_t DwordOff = 0) {
  unsigned Opc = ST.hasFlatScratchEnabled() ? AMDGPU::SCRATCH_LOAD_DWORD_SADDR
                                            : AMDGPU::BUFFER_LOAD_DWORD_OFFSET;
 
  MachineFrameInfo &FrameInfo = MF.getFrameInfo();
  MachinePointerInfo PtrInfo = MachinePointerInfo::getFixedStack(MF, FI);
  MachineMemOperand *MMO = MF.getMachineMemOperand(
      PtrInfo, MachineMemOperand::MOLoad, FrameInfo.getObjectSize(FI),
      FrameInfo.getObjectAlign(FI));
  TRI.buildSpillLoadStore(MBB, I, DL, Opc, FI, SpillReg, false, FrameReg,
                          DwordOff, MMO, nullptr, &LiveUnits);
}
 
static void buildGitPtr(MachineBasicBlock &MBB, MachineBasicBlock::iterator I,
                        const DebugLoc &DL, const SIInstrInfo *TII,
                        Register TargetReg) {
  MachineFunction *MF = MBB.getParent();
  const SIMachineFunctionInfo *MFI = MF->getInfo<SIMachineFunctionInfo>();
  const SIRegisterInfo *TRI = &TII->getRegisterInfo();
  const MCInstrDesc &SMovB32 = TII->get(AMDGPU::S_MOV_B32);
  Register TargetLo = TRI->getSubReg(TargetReg, AMDGPU::sub0);
  Register TargetHi = TRI->getSubReg(TargetReg, AMDGPU::sub1);
 
  if (MFI->getGITPtrHigh() != 0xffffffff) {
    BuildMI(MBB, I, DL, SMovB32, TargetHi)
        .addImm(MFI->getGITPtrHigh())
        .addReg(TargetReg, RegState::ImplicitDefine);
  } else {
    const MCInstrDesc &GetPC64 = TII->get(AMDGPU::S_GETPC_B64_pseudo);
    BuildMI(MBB, I, DL, GetPC64, TargetReg);
  }
  Register GitPtrLo = MFI->getGITPtrLoReg(*MF);
  MF->getRegInfo().addLiveIn(GitPtrLo);
  MBB.addLiveIn(GitPtrLo);
  BuildMI(MBB, I, DL, SMovB32, TargetLo)
    .addReg(GitPtrLo);
}
 
static void initLiveUnits(LiveRegUnits &LiveUnits, const SIRegisterInfo &TRI,
                          const SIMachineFunctionInfo *FuncInfo,
                          MachineFunction &MF, MachineBasicBlock &MBB,
                          MachineBasicBlock::iterator MBBI, bool IsProlog) {
  if (LiveUnits.empty()) {
    LiveUnits.init(TRI);
    if (IsProlog) {
      LiveUnits.addLiveIns(MBB);
    } else {
      // In epilog.
      LiveUnits.addLiveOuts(MBB);
      LiveUnits.stepBackward(*MBBI);
    }
  }
}
 
namespace llvm {
 
// SpillBuilder to save/restore special SGPR spills like the one needed for FP,
// BP, etc. These spills are delayed until the current function's frame is
// finalized. For a given register, the builder uses the
// PrologEpilogSGPRSaveRestoreInfo to decide the spill method.
class PrologEpilogSGPRSpillBuilder {
  MachineBasicBlock::iterator MI;
  MachineBasicBlock &MBB;
  MachineFunction &MF;
  const GCNSubtarget &ST;
  MachineFrameInfo &MFI;
  SIMachineFunctionInfo *FuncInfo;
  const SIInstrInfo *TII;
  const SIRegisterInfo &TRI;
  const MCRegisterInfo *MCRI;
  const SIFrameLowering *TFI;
  Register SuperReg;
  const PrologEpilogSGPRSaveRestoreInfo SI;
  LiveRegUnits &LiveUnits;
  const DebugLoc &DL;
  Register FrameReg;
  ArrayRef<int16_t> SplitParts;
  unsigned NumSubRegs;
  unsigned EltSize = 4;
  bool IsFramePtrPrologSpill;
  bool NeedsFrameMoves;
 
  static bool isExec(Register Reg) {
    return Reg == AMDGPU::EXEC_LO || Reg == AMDGPU::EXEC;
  }
 
  /// If this builder requires SuperReg-based CFI, which is emitted after all
  /// SubRegs are actually spilled, return the Register which should be used
  /// as input to getDwarfRegNum. Otherwise, CFI should be generated per-SubReg.
  ///
  /// Note: Most spills handled by this builder generate CFI after each
  /// SubReg spill, as each SubReg maps directly to a CFI register via
  /// getDwarfRegNum(SubReg, false). All other cases currently currently
  /// correspond to the SuperReg directly.
  MCRegister getCFISuperReg() const {
    if (IsFramePtrPrologSpill)
      return FuncInfo->getFrameOffsetReg();
    // FIXME: CFI for EXEC needs a fix by accurately computing the spill
    // offset for both the low and high components.
    if (isExec(SuperReg))
      return AMDGPU::EXEC;
    return {};
  }
 
  void saveToMemory(const int FI) const {
    MachineRegisterInfo &MRI = MF.getRegInfo();
    const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
    assert(!MFI.isDeadObjectIndex(FI));
 
    initLiveUnits(LiveUnits, TRI, FuncInfo, MF, MBB, MI, /*IsProlog*/ true);
 
    MCPhysReg TmpVGPR = findScratchNonCalleeSaveRegister(
        MRI, LiveUnits, AMDGPU::VGPR_32RegClass);
    if (!TmpVGPR)
      report_fatal_error("failed to find free scratch register");
 
    auto BuildCFI = [&](Register Reg) {
      TFI->buildCFI(MBB, MI, DL,
                    MCCFIInstruction::createOffset(
                        nullptr, MCRI->getDwarfRegNum(Reg, false),
                        MFI.getObjectOffset(FI) * ST.getWavefrontSize()));
    };
    MCRegister CFISuperReg = getCFISuperReg();
    for (unsigned I = 0, DwordOff = 0; I < NumSubRegs; ++I) {
      Register SubReg = NumSubRegs == 1
                            ? SuperReg
                            : Register(TRI.getSubReg(SuperReg, SplitParts[I]));
      BuildMI(MBB, MI, DL, TII->get(AMDGPU::V_MOV_B32_e32), TmpVGPR)
          .addReg(SubReg);
 
      buildPrologSpill(ST, TRI, *FuncInfo, LiveUnits, MF, MBB, MI, DL, TmpVGPR,
                       FI, FrameReg, DwordOff);
      if (NeedsFrameMoves && !CFISuperReg)
        BuildCFI(SubReg);
      DwordOff += 4;
    }
    if (NeedsFrameMoves && CFISuperReg)
      BuildCFI(CFISuperReg);
  }
 
  void saveToVGPRLane(const int FI) const {
    assert(!MFI.isDeadObjectIndex(FI));
 
    assert(MFI.getStackID(FI) == TargetStackID::SGPRSpill);
    ArrayRef<SIRegisterInfo::SpilledReg> Spill =
        FuncInfo->getSGPRSpillToPhysicalVGPRLanes(FI);
    assert(Spill.size() == NumSubRegs);
 
    MCRegister CFISuperReg = getCFISuperReg();
    for (unsigned I = 0; I < NumSubRegs; ++I) {
      Register SubReg = NumSubRegs == 1
                            ? SuperReg
                            : Register(TRI.getSubReg(SuperReg, SplitParts[I]));
      BuildMI(MBB, MI, DL, TII->get(AMDGPU::SI_SPILL_S32_TO_VGPR),
              Spill[I].VGPR)
          .addReg(SubReg)
          .addImm(Spill[I].Lane)
          .addReg(Spill[I].VGPR, RegState::Undef);
      if (NeedsFrameMoves && !CFISuperReg)
        TFI->buildCFIForSGPRToVGPRSpill(MBB, MI, DL, SubReg, Spill[I].VGPR,
                                        Spill[I].Lane);
    }
    if (NeedsFrameMoves && CFISuperReg)
      TFI->buildCFIForSGPRToVGPRSpill(MBB, MI, DL, CFISuperReg, Spill);
  }
 
  void copyToScratchSGPR(Register DstReg) const {
    BuildMI(MBB, MI, DL, TII->get(AMDGPU::COPY), DstReg)
        .addReg(SuperReg)
        .setMIFlag(MachineInstr::FrameSetup);
    if (NeedsFrameMoves) {
      const TargetRegisterClass *RC = TRI.getPhysRegBaseClass(DstReg);
      ArrayRef<int16_t> DstSplitParts = TRI.getRegSplitParts(RC, EltSize);
      assert(NumSubRegs == (DstSplitParts.empty() ? 1 : DstSplitParts.size()));
      MCRegister CFISuperReg = getCFISuperReg();
      if (NumSubRegs == 1) {
        TFI->buildCFI(
            MBB, MI, DL,
            MCCFIInstruction::createRegister(
                nullptr,
                MCRI->getDwarfRegNum(
                    CFISuperReg ? CFISuperReg : SuperReg.asMCReg(), false),
                MCRI->getDwarfRegNum(DstReg, false)));
      } else if (isExec(CFISuperReg)) {
        assert(NumSubRegs == 2 && "EXEC larger than 64-bit");
        TFI->buildCFIForRegToSGPRPairSpill(MBB, MI, DL, CFISuperReg, DstReg);
      } else {
        for (unsigned I = 0; I < NumSubRegs; ++I) {
          MCRegister SrcSubReg = TRI.getSubReg(SuperReg, SplitParts[I]);
          MCRegister DstSubReg = TRI.getSubReg(DstReg, DstSplitParts[I]);
          TFI->buildCFI(MBB, MI, DL,
                        MCCFIInstruction::createRegister(
                            nullptr, MCRI->getDwarfRegNum(SrcSubReg, false),
                            MCRI->getDwarfRegNum(DstSubReg, false)));
        }
      }
    }
  }
 
  void restoreFromMemory(const int FI) {
    MachineRegisterInfo &MRI = MF.getRegInfo();
    const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
 
    initLiveUnits(LiveUnits, TRI, FuncInfo, MF, MBB, MI, /*IsProlog*/ false);
    MCPhysReg TmpVGPR = findScratchNonCalleeSaveRegister(
        MRI, LiveUnits, AMDGPU::VGPR_32RegClass);
    if (!TmpVGPR)
      report_fatal_error("failed to find free scratch register");
 
    for (unsigned I = 0, DwordOff = 0; I < NumSubRegs; ++I) {
      MCRegister SubReg = NumSubRegs == 1
                              ? SuperReg.asMCReg()
                              : TRI.getSubReg(SuperReg, SplitParts[I]);
 
      buildEpilogRestore(ST, TRI, *FuncInfo, LiveUnits, MF, MBB, MI, DL,
                         TmpVGPR, FI, FrameReg, DwordOff);
      assert(SubReg.isPhysical());
 
      BuildMI(MBB, MI, DL, TII->get(AMDGPU::V_READFIRSTLANE_B32), SubReg)
          .addReg(TmpVGPR, RegState::Kill);
      DwordOff += 4;
    }
  }
 
  void restoreFromVGPRLane(const int FI) {
    assert(MFI.getStackID(FI) == TargetStackID::SGPRSpill);
    ArrayRef<SIRegisterInfo::SpilledReg> Spill =
        FuncInfo->getSGPRSpillToPhysicalVGPRLanes(FI);
    assert(Spill.size() == NumSubRegs);
 
    for (unsigned I = 0; I < NumSubRegs; ++I) {
      MCRegister SubReg = NumSubRegs == 1
                              ? SuperReg.asMCReg()
                              : TRI.getSubReg(SuperReg, SplitParts[I]);
      BuildMI(MBB, MI, DL, TII->get(AMDGPU::SI_RESTORE_S32_FROM_VGPR), SubReg)
          .addReg(Spill[I].VGPR)
          .addImm(Spill[I].Lane);
    }
  }
 
  void copyFromScratchSGPR(Register SrcReg) const {
    BuildMI(MBB, MI, DL, TII->get(AMDGPU::COPY), SuperReg)
        .addReg(SrcReg)
        .setMIFlag(MachineInstr::FrameDestroy);
  }
 
public:
  PrologEpilogSGPRSpillBuilder(Register Reg,
                               const PrologEpilogSGPRSaveRestoreInfo SI,
                               MachineBasicBlock &MBB,
                               MachineBasicBlock::iterator MI,
                               const DebugLoc &DL, const SIInstrInfo *TII,
                               const SIRegisterInfo &TRI,
                               LiveRegUnits &LiveUnits, Register FrameReg,
                               bool IsFramePtrPrologSpill = false)
      : MI(MI), MBB(MBB), MF(*MBB.getParent()),
        ST(MF.getSubtarget<GCNSubtarget>()), MFI(MF.getFrameInfo()),
        FuncInfo(MF.getInfo<SIMachineFunctionInfo>()), TII(TII), TRI(TRI),
        MCRI(MF.getContext().getRegisterInfo()), TFI(ST.getFrameLowering()),
        SuperReg(Reg), SI(SI), LiveUnits(LiveUnits), DL(DL), FrameReg(FrameReg),
        IsFramePtrPrologSpill(IsFramePtrPrologSpill),
        NeedsFrameMoves(MF.needsFrameMoves()) {
    const TargetRegisterClass *RC = TRI.getPhysRegBaseClass(SuperReg);
    SplitParts = TRI.getRegSplitParts(RC, EltSize);
    NumSubRegs = SplitParts.empty() ? 1 : SplitParts.size();
 
    assert(SuperReg != AMDGPU::M0 && "m0 should never spill");
  }
 
  void save() {
    switch (SI.getKind()) {
    case SGPRSaveKind::SPILL_TO_MEM:
      return saveToMemory(SI.getIndex());
    case SGPRSaveKind::SPILL_TO_VGPR_LANE:
      return saveToVGPRLane(SI.getIndex());
    case SGPRSaveKind::COPY_TO_SCRATCH_SGPR:
      return copyToScratchSGPR(SI.getReg());
    }
  }
 
  void restore() {
    switch (SI.getKind()) {
    case SGPRSaveKind::SPILL_TO_MEM:
      return restoreFromMemory(SI.getIndex());
    case SGPRSaveKind::SPILL_TO_VGPR_LANE:
      return restoreFromVGPRLane(SI.getIndex());
    case SGPRSaveKind::COPY_TO_SCRATCH_SGPR:
      return copyFromScratchSGPR(SI.getReg());
    }
  }
};
 
} // namespace llvm
 
// Emit flat scratch setup code, assuming `MFI->hasFlatScratchInit()`
void SIFrameLowering::emitEntryFunctionFlatScratchInit(
    MachineFunction &MF, MachineBasicBlock &MBB, MachineBasicBlock::iterator I,
    const DebugLoc &DL, Register ScratchWaveOffsetReg) const {
  const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
  const SIInstrInfo *TII = ST.getInstrInfo();
  const SIRegisterInfo *TRI = &TII->getRegisterInfo();
  const SIMachineFunctionInfo *MFI = MF.getInfo<SIMachineFunctionInfo>();
 
  // We don't need this if we only have spills since there is no user facing
  // scratch.
 
  // TODO: If we know we don't have flat instructions earlier, we can omit
  // this from the input registers.
  //
  // TODO: We only need to know if we access scratch space through a flat
  // pointer. Because we only detect if flat instructions are used at all,
  // this will be used more often than necessary on VI.
 
  Register FlatScrInitLo;
  Register FlatScrInitHi;
 
  if (ST.isAmdPalOS()) {
    // Extract the scratch offset from the descriptor in the GIT
    LiveRegUnits LiveUnits;
    LiveUnits.init(*TRI);
    LiveUnits.addLiveIns(MBB);
 
    // Find unused reg to load flat scratch init into
    MachineRegisterInfo &MRI = MF.getRegInfo();
    Register FlatScrInit = AMDGPU::NoRegister;
    ArrayRef<MCPhysReg> AllSGPR64s = TRI->getAllSGPR64(MF);
    unsigned NumPreloaded = (MFI->getNumPreloadedSGPRs() + 1) / 2;
    AllSGPR64s = AllSGPR64s.slice(
        std::min(static_cast<unsigned>(AllSGPR64s.size()), NumPreloaded));
    Register GITPtrLoReg = MFI->getGITPtrLoReg(MF);
    for (MCPhysReg Reg : AllSGPR64s) {
      if (LiveUnits.available(Reg) && !MRI.isReserved(Reg) &&
          MRI.isAllocatable(Reg) && !TRI->isSubRegisterEq(Reg, GITPtrLoReg)) {
        FlatScrInit = Reg;
        break;
      }
    }
    assert(FlatScrInit && "Failed to find free register for scratch init");
 
    FlatScrInitLo = TRI->getSubReg(FlatScrInit, AMDGPU::sub0);
    FlatScrInitHi = TRI->getSubReg(FlatScrInit, AMDGPU::sub1);
 
    buildGitPtr(MBB, I, DL, TII, FlatScrInit);
 
    // We now have the GIT ptr - now get the scratch descriptor from the entry
    // at offset 0 (or offset 16 for a compute shader).
    MachinePointerInfo PtrInfo(AMDGPUAS::CONSTANT_ADDRESS);
    const MCInstrDesc &LoadDwordX2 = TII->get(AMDGPU::S_LOAD_DWORDX2_IMM);
    auto *MMO = MF.getMachineMemOperand(
        PtrInfo,
        MachineMemOperand::MOLoad | MachineMemOperand::MOInvariant |
            MachineMemOperand::MODereferenceable,
        8, Align(4));
    unsigned Offset =
        MF.getFunction().getCallingConv() == CallingConv::AMDGPU_CS ? 16 : 0;
    const GCNSubtarget &Subtarget = MF.getSubtarget<GCNSubtarget>();
    unsigned EncodedOffset = AMDGPU::convertSMRDOffsetUnits(Subtarget, Offset);
    BuildMI(MBB, I, DL, LoadDwordX2, FlatScrInit)
        .addReg(FlatScrInit)
        .addImm(EncodedOffset) // offset
        .addImm(0)             // cpol
        .addMemOperand(MMO);
 
    // Mask the offset in [47:0] of the descriptor
    const MCInstrDesc &SAndB32 = TII->get(AMDGPU::S_AND_B32);
    auto And = BuildMI(MBB, I, DL, SAndB32, FlatScrInitHi)
        .addReg(FlatScrInitHi)
        .addImm(0xffff);
    And->getOperand(3).setIsDead(); // Mark SCC as dead.
  } else {
    Register FlatScratchInitReg =
        MFI->getPreloadedReg(AMDGPUFunctionArgInfo::FLAT_SCRATCH_INIT);
    assert(FlatScratchInitReg);
 
    MachineRegisterInfo &MRI = MF.getRegInfo();
    MRI.addLiveIn(FlatScratchInitReg);
    MBB.addLiveIn(FlatScratchInitReg);
 
    FlatScrInitLo = TRI->getSubReg(FlatScratchInitReg, AMDGPU::sub0);
    FlatScrInitHi = TRI->getSubReg(FlatScratchInitReg, AMDGPU::sub1);
  }
 
  // Do a 64-bit pointer add.
  if (ST.flatScratchIsPointer()) {
    if (ST.getGeneration() >= AMDGPUSubtarget::GFX10) {
      BuildMI(MBB, I, DL, TII->get(AMDGPU::S_ADD_U32), FlatScrInitLo)
        .addReg(FlatScrInitLo)
        .addReg(ScratchWaveOffsetReg);
      auto Addc = BuildMI(MBB, I, DL, TII->get(AMDGPU::S_ADDC_U32),
                          FlatScrInitHi)
        .addReg(FlatScrInitHi)
        .addImm(0);
      Addc->getOperand(3).setIsDead(); // Mark SCC as dead.
 
      using namespace AMDGPU::Hwreg;
      BuildMI(MBB, I, DL, TII->get(AMDGPU::S_SETREG_B32))
          .addReg(FlatScrInitLo)
          .addImm(int16_t(HwregEncoding::encode(ID_FLAT_SCR_LO, 0, 32)));
      BuildMI(MBB, I, DL, TII->get(AMDGPU::S_SETREG_B32))
          .addReg(FlatScrInitHi)
          .addImm(int16_t(HwregEncoding::encode(ID_FLAT_SCR_HI, 0, 32)));
      return;
    }
 
    // For GFX9.
    BuildMI(MBB, I, DL, TII->get(AMDGPU::S_ADD_U32), AMDGPU::FLAT_SCR_LO)
      .addReg(FlatScrInitLo)
      .addReg(ScratchWaveOffsetReg);
    auto Addc = BuildMI(MBB, I, DL, TII->get(AMDGPU::S_ADDC_U32),
                        AMDGPU::FLAT_SCR_HI)
      .addReg(FlatScrInitHi)
      .addImm(0);
    Addc->getOperand(3).setIsDead(); // Mark SCC as dead.
 
    return;
  }
 
  assert(ST.getGeneration() < AMDGPUSubtarget::GFX9);
 
  // Copy the size in bytes.
  BuildMI(MBB, I, DL, TII->get(AMDGPU::COPY), AMDGPU::FLAT_SCR_LO)
    .addReg(FlatScrInitHi, RegState::Kill);
 
  // Add wave offset in bytes to private base offset.
  // See comment in AMDKernelCodeT.h for enable_sgpr_flat_scratch_init.
  BuildMI(MBB, I, DL, TII->get(AMDGPU::S_ADD_I32), FlatScrInitLo)
      .addReg(FlatScrInitLo)
      .addReg(ScratchWaveOffsetReg);
 
  // Convert offset to 256-byte units.
  auto LShr = BuildMI(MBB, I, DL, TII->get(AMDGPU::S_LSHR_B32),
                      AMDGPU::FLAT_SCR_HI)
    .addReg(FlatScrInitLo, RegState::Kill)
    .addImm(8);
  LShr->getOperand(3).setIsDead(); // Mark SCC as dead.
}
 
// Note SGPRSpill stack IDs should only be used for SGPR spilling to VGPRs, not
// memory. They should have been removed by now.
static bool allStackObjectsAreDead(const MachineFrameInfo &MFI) {
  for (int I = MFI.getObjectIndexBegin(), E = MFI.getObjectIndexEnd();
       I != E; ++I) {
    if (!MFI.isDeadObjectIndex(I))
      return false;
  }
 
  return true;
}
 
// Shift down registers reserved for the scratch RSRC.
Register SIFrameLowering::getEntryFunctionReservedScratchRsrcReg(
    MachineFunction &MF) const {
 
  const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
  const SIInstrInfo *TII = ST.getInstrInfo();
  const SIRegisterInfo *TRI = &TII->getRegisterInfo();
  MachineRegisterInfo &MRI = MF.getRegInfo();
  SIMachineFunctionInfo *MFI = MF.getInfo<SIMachineFunctionInfo>();
 
  assert(MFI->isEntryFunction());
 
  Register ScratchRsrcReg = MFI->getScratchRSrcReg();
 
  if (!ScratchRsrcReg || (!MRI.isPhysRegUsed(ScratchRsrcReg) &&
                          allStackObjectsAreDead(MF.getFrameInfo())))
    return Register();
 
  if (ST.hasSGPRInitBug() ||
      ScratchRsrcReg != TRI->reservedPrivateSegmentBufferReg(MF))
    return ScratchRsrcReg;
 
  // We reserved the last registers for this. Shift it down to the end of those
  // which were actually used.
  //
  // FIXME: It might be safer to use a pseudoregister before replacement.
 
  // FIXME: We should be able to eliminate unused input registers. We only
  // cannot do this for the resources required for scratch access. For now we
  // skip over user SGPRs and may leave unused holes.
 
  unsigned NumPreloaded = (MFI->getNumPreloadedSGPRs() + 3) / 4;
  ArrayRef<MCPhysReg> AllSGPR128s = TRI->getAllSGPR128(MF);
  AllSGPR128s = AllSGPR128s.slice(std::min(static_cast<unsigned>(AllSGPR128s.size()), NumPreloaded));
 
  // Skip the last N reserved elements because they should have already been
  // reserved for VCC etc.
  Register GITPtrLoReg = MFI->getGITPtrLoReg(MF);
  for (MCPhysReg Reg : AllSGPR128s) {
    // Pick the first unallocated one. Make sure we don't clobber the other
    // reserved input we needed. Also for PAL, make sure we don't clobber
    // the GIT pointer passed in SGPR0 or SGPR8.
    if (!MRI.isPhysRegUsed(Reg) && MRI.isAllocatable(Reg) &&
        (!GITPtrLoReg || !TRI->isSubRegisterEq(Reg, GITPtrLoReg))) {
      MRI.replaceRegWith(ScratchRsrcReg, Reg);
      MFI->setScratchRSrcReg(Reg);
      MRI.reserveReg(Reg, TRI);
      return Reg;
    }
  }
 
  return ScratchRsrcReg;
}
 
static unsigned getScratchScaleFactor(const GCNSubtarget &ST) {
  return ST.hasFlatScratchEnabled() ? 1 : ST.getWavefrontSize();
}
 
void SIFrameLowering::emitEntryFunctionPrologue(MachineFunction &MF,
                                                MachineBasicBlock &MBB) const {
  assert(&MF.front() == &MBB && "Shrink-wrapping not yet supported");
 
  // FIXME: If we only have SGPR spills, we won't actually be using scratch
  // memory since these spill to VGPRs. We should be cleaning up these unused
  // SGPR spill frame indices somewhere.
 
  // FIXME: We still have implicit uses on SGPR spill instructions in case they
  // need to spill to vector memory. It's likely that will not happen, but at
  // this point it appears we need the setup. This part of the prolog should be
  // emitted after frame indices are eliminated.
 
  // FIXME: Remove all of the isPhysRegUsed checks
 
  SIMachineFunctionInfo *MFI = MF.getInfo<SIMachineFunctionInfo>();
  const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
  const SIInstrInfo *TII = ST.getInstrInfo();
  const SIRegisterInfo *TRI = &TII->getRegisterInfo();
  MachineRegisterInfo &MRI = MF.getRegInfo();
  const Function &F = MF.getFunction();
  MachineFrameInfo &FrameInfo = MF.getFrameInfo();
 
  assert(MFI->isEntryFunction());
 
  // Debug location must be unknown since the first debug location is used to
  // determine the end of the prologue.
  DebugLoc DL;
  MachineBasicBlock::iterator I = MBB.begin();
 
  if (MF.needsFrameMoves()) {
    // On entry the SP/FP are not set up, so we need to define the CFA in terms
    // of a literal location expression.
    static const char CFAEncodedInstUserOpsArr[] = {
        dwarf::DW_CFA_def_cfa_expression,
        4, // length
        static_cast<char>(dwarf::DW_OP_lit0),
        static_cast<char>(dwarf::DW_OP_lit0 +
                          dwarf::DW_ASPACE_LLVM_AMDGPU_private_wave),
        static_cast<char>(dwarf::DW_OP_LLVM_user),
        static_cast<char>(dwarf::DW_OP_LLVM_form_aspace_address)};
    static StringRef CFAEncodedInstUserOps =
        StringRef(CFAEncodedInstUserOpsArr, sizeof(CFAEncodedInstUserOpsArr));
    buildCFI(MBB, I, DL,
             MCCFIInstruction::createEscape(nullptr, CFAEncodedInstUserOps,
                                            SMLoc(),
                                            "CFA is 0 in private_wave aspace"));
    // Unwinding halts when the return address (PC) is undefined.
    buildCFI(MBB, I, DL,
             MCCFIInstruction::createUndefined(
                 nullptr, TRI->getDwarfRegNum(AMDGPU::PC_REG, false)));
  }
 
  Register PreloadedScratchWaveOffsetReg = MFI->getPreloadedReg(
      AMDGPUFunctionArgInfo::PRIVATE_SEGMENT_WAVE_BYTE_OFFSET);
 
  // We need to do the replacement of the private segment buffer register even
  // if there are no stack objects. There could be stores to undef or a
  // constant without an associated object.
  //
  // This will return `Register()` in cases where there are no actual
  // uses of the SRSRC.
  Register ScratchRsrcReg;
  if (!ST.hasFlatScratchEnabled())
    ScratchRsrcReg = getEntryFunctionReservedScratchRsrcReg(MF);
 
  // Make the selected register live throughout the function.
  if (ScratchRsrcReg) {
    for (MachineBasicBlock &OtherBB : MF) {
      if (&OtherBB != &MBB) {
        OtherBB.addLiveIn(ScratchRsrcReg);
      }
    }
  }
 
  // Now that we have fixed the reserved SRSRC we need to locate the
  // (potentially) preloaded SRSRC.
  Register PreloadedScratchRsrcReg;
  if (ST.isAmdHsaOrMesa(F)) {
    PreloadedScratchRsrcReg =
        MFI->getPreloadedReg(AMDGPUFunctionArgInfo::PRIVATE_SEGMENT_BUFFER);
    if (ScratchRsrcReg && PreloadedScratchRsrcReg) {
      // We added live-ins during argument lowering, but since they were not
      // used they were deleted. We're adding the uses now, so add them back.
      MRI.addLiveIn(PreloadedScratchRsrcReg);
      MBB.addLiveIn(PreloadedScratchRsrcReg);
    }
  }
 
  // We found the SRSRC first because it needs four registers and has an
  // alignment requirement. If the SRSRC that we found is clobbering with
  // the scratch wave offset, which may be in a fixed SGPR or a free SGPR
  // chosen by SITargetLowering::allocateSystemSGPRs, COPY the scratch
  // wave offset to a free SGPR.
  Register ScratchWaveOffsetReg;
  if (PreloadedScratchWaveOffsetReg &&
      TRI->isSubRegisterEq(ScratchRsrcReg, PreloadedScratchWaveOffsetReg)) {
    ArrayRef<MCPhysReg> AllSGPRs = TRI->getAllSGPR32(MF);
    unsigned NumPreloaded = MFI->getNumPreloadedSGPRs();
    AllSGPRs = AllSGPRs.slice(
        std::min(static_cast<unsigned>(AllSGPRs.size()), NumPreloaded));
    Register GITPtrLoReg = MFI->getGITPtrLoReg(MF);
    for (MCPhysReg Reg : AllSGPRs) {
      if (!MRI.isPhysRegUsed(Reg) && MRI.isAllocatable(Reg) &&
          !TRI->isSubRegisterEq(ScratchRsrcReg, Reg) && GITPtrLoReg != Reg) {
        ScratchWaveOffsetReg = Reg;
        BuildMI(MBB, I, DL, TII->get(AMDGPU::COPY), ScratchWaveOffsetReg)
            .addReg(PreloadedScratchWaveOffsetReg, RegState::Kill);
        break;
      }
    }
 
    // FIXME: We can spill incoming arguments and restore at the end of the
    // prolog.
    if (!ScratchWaveOffsetReg)
      report_fatal_error(
          "could not find temporary scratch offset register in prolog");
  } else {
    ScratchWaveOffsetReg = PreloadedScratchWaveOffsetReg;
  }
  assert(ScratchWaveOffsetReg || !PreloadedScratchWaveOffsetReg);
 
  unsigned Offset = FrameInfo.getStackSize() * getScratchScaleFactor(ST);
  if (!mayReserveScratchForCWSR(MF)) {
    if (hasFP(MF)) {
      Register FPReg = MFI->getFrameOffsetReg();
      assert(FPReg != AMDGPU::FP_REG);
      BuildMI(MBB, I, DL, TII->get(AMDGPU::S_MOV_B32), FPReg).addImm(0);
    }
 
    if (requiresStackPointerReference(MF)) {
      Register SPReg = MFI->getStackPtrOffsetReg();
      assert(SPReg != AMDGPU::SP_REG);
      BuildMI(MBB, I, DL, TII->get(AMDGPU::S_MOV_B32), SPReg).addImm(Offset);
    }
  } else {
    // We need to check if we're on a compute queue - if we are, then the CWSR
    // trap handler may need to store some VGPRs on the stack. The first VGPR
    // block is saved separately, so we only need to allocate space for any
    // additional VGPR blocks used. For now, we will make sure there's enough
    // room for the theoretical maximum number of VGPRs that can be allocated.
    // FIXME: Figure out if the shader uses fewer VGPRs in practice.
    assert(hasFP(MF));
    Register FPReg = MFI->getFrameOffsetReg();
    assert(FPReg != AMDGPU::FP_REG);
    unsigned VGPRSize = llvm::alignTo(
        (ST.getAddressableNumVGPRs(MFI->getDynamicVGPRBlockSize()) -
         AMDGPU::IsaInfo::getVGPRAllocGranule(ST,
                                              MFI->getDynamicVGPRBlockSize())) *
            4,
        FrameInfo.getMaxAlign());
    MFI->setScratchReservedForDynamicVGPRs(VGPRSize);
 
    BuildMI(MBB, I, DL, TII->get(AMDGPU::GET_STACK_BASE), FPReg);
    if (requiresStackPointerReference(MF)) {
      Register SPReg = MFI->getStackPtrOffsetReg();
      assert(SPReg != AMDGPU::SP_REG);
 
      // If at least one of the constants can be inlined, then we can use
      // s_cselect. Otherwise, use a mov and cmovk.
      if (AMDGPU::isInlinableLiteral32(Offset, ST.hasInv2PiInlineImm()) ||
          AMDGPU::isInlinableLiteral32(Offset + VGPRSize,
                                       ST.hasInv2PiInlineImm())) {
        BuildMI(MBB, I, DL, TII->get(AMDGPU::S_CSELECT_B32), SPReg)
            .addImm(Offset + VGPRSize)
            .addImm(Offset);
      } else {
        BuildMI(MBB, I, DL, TII->get(AMDGPU::S_MOV_B32), SPReg).addImm(Offset);
        BuildMI(MBB, I, DL, TII->get(AMDGPU::S_CMOVK_I32), SPReg)
            .addImm(Offset + VGPRSize);
      }
    }
  }
 
  bool NeedsFlatScratchInit =
      MFI->getUserSGPRInfo().hasFlatScratchInit() &&
      (MRI.isPhysRegUsed(AMDGPU::FLAT_SCR) || FrameInfo.hasCalls() ||
       (!allStackObjectsAreDead(FrameInfo) && ST.hasFlatScratchEnabled()));
 
  if ((NeedsFlatScratchInit || ScratchRsrcReg) &&
      PreloadedScratchWaveOffsetReg && !ST.hasArchitectedFlatScratch()) {
    MRI.addLiveIn(PreloadedScratchWaveOffsetReg);
    MBB.addLiveIn(PreloadedScratchWaveOffsetReg);
  }
 
  if (NeedsFlatScratchInit) {
    emitEntryFunctionFlatScratchInit(MF, MBB, I, DL, ScratchWaveOffsetReg);
  }
 
  if (ScratchRsrcReg) {
    emitEntryFunctionScratchRsrcRegSetup(MF, MBB, I, DL,
                                         PreloadedScratchRsrcReg,
                                         ScratchRsrcReg, ScratchWaveOffsetReg);
  }
 
  if (ST.hasWaitXcnt()) {
    // Set REPLAY_MODE (bit 25) in MODE register to enable multi-group XNACK
    // replay. This aligns hardware behavior with the compiler's s_wait_xcnt
    // insertion logic, which assumes multi-group mode by default.
    unsigned RegEncoding =
        AMDGPU::Hwreg::HwregEncoding::encode(AMDGPU::Hwreg::ID_MODE, 25, 1);
    BuildMI(MBB, I, DL, TII->get(AMDGPU::S_SETREG_IMM32_B32))
        .addImm(1)
        .addImm(RegEncoding);
  }
}
 
// Emit scratch RSRC setup code, assuming `ScratchRsrcReg != AMDGPU::NoReg`
void SIFrameLowering::emitEntryFunctionScratchRsrcRegSetup(
    MachineFunction &MF, MachineBasicBlock &MBB, MachineBasicBlock::iterator I,
    const DebugLoc &DL, Register PreloadedScratchRsrcReg,
    Register ScratchRsrcReg, Register ScratchWaveOffsetReg) const {
 
  const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
  const SIInstrInfo *TII = ST.getInstrInfo();
  const SIRegisterInfo *TRI = &TII->getRegisterInfo();
  const SIMachineFunctionInfo *MFI = MF.getInfo<SIMachineFunctionInfo>();
  const Function &Fn = MF.getFunction();
 
  if (ST.isAmdPalOS()) {
    // The pointer to the GIT is formed from the offset passed in and either
    // the amdgpu-git-ptr-high function attribute or the top part of the PC
    Register Rsrc01 = TRI->getSubReg(ScratchRsrcReg, AMDGPU::sub0_sub1);
    Register Rsrc03 = TRI->getSubReg(ScratchRsrcReg, AMDGPU::sub3);
 
    buildGitPtr(MBB, I, DL, TII, Rsrc01);
 
    // We now have the GIT ptr - now get the scratch descriptor from the entry
    // at offset 0 (or offset 16 for a compute shader).
    MachinePointerInfo PtrInfo(AMDGPUAS::CONSTANT_ADDRESS);
    const MCInstrDesc &LoadDwordX4 = TII->get(AMDGPU::S_LOAD_DWORDX4_IMM);
    auto *MMO = MF.getMachineMemOperand(
        PtrInfo,
        MachineMemOperand::MOLoad | MachineMemOperand::MOInvariant |
            MachineMemOperand::MODereferenceable,
        16, Align(4));
    unsigned Offset = Fn.getCallingConv() == CallingConv::AMDGPU_CS ? 16 : 0;
    const GCNSubtarget &Subtarget = MF.getSubtarget<GCNSubtarget>();
    unsigned EncodedOffset = AMDGPU::convertSMRDOffsetUnits(Subtarget, Offset);
    BuildMI(MBB, I, DL, LoadDwordX4, ScratchRsrcReg)
      .addReg(Rsrc01)
      .addImm(EncodedOffset) // offset
      .addImm(0) // cpol
      .addReg(ScratchRsrcReg, RegState::ImplicitDefine)
      .addMemOperand(MMO);
 
    // The driver will always set the SRD for wave 64 (bits 118:117 of
    // descriptor / bits 22:21 of third sub-reg will be 0b11)
    // If the shader is actually wave32 we have to modify the const_index_stride
    // field of the descriptor 3rd sub-reg (bits 22:21) to 0b10 (stride=32). The
    // reason the driver does this is that there can be cases where it presents
    // 2 shaders with different wave size (e.g. VsFs).
    // TODO: convert to using SCRATCH instructions or multiple SRD buffers
    if (ST.isWave32()) {
      const MCInstrDesc &SBitsetB32 = TII->get(AMDGPU::S_BITSET0_B32);
      BuildMI(MBB, I, DL, SBitsetB32, Rsrc03)
          .addImm(21)
          .addReg(Rsrc03);
    }
  } else if (ST.isMesaGfxShader(Fn) || !PreloadedScratchRsrcReg) {
    assert(!ST.isAmdHsaOrMesa(Fn));
    const MCInstrDesc &SMovB32 = TII->get(AMDGPU::S_MOV_B32);
 
    Register Rsrc2 = TRI->getSubReg(ScratchRsrcReg, AMDGPU::sub2);
    Register Rsrc3 = TRI->getSubReg(ScratchRsrcReg, AMDGPU::sub3);
 
    // Use relocations to get the pointer, and setup the other bits manually.
    uint64_t Rsrc23 = TII->getScratchRsrcWords23();
 
    if (MFI->getUserSGPRInfo().hasImplicitBufferPtr()) {
      Register Rsrc01 = TRI->getSubReg(ScratchRsrcReg, AMDGPU::sub0_sub1);
 
      if (AMDGPU::isCompute(MF.getFunction().getCallingConv())) {
        const MCInstrDesc &Mov64 = TII->get(AMDGPU::S_MOV_B64);
 
        BuildMI(MBB, I, DL, Mov64, Rsrc01)
          .addReg(MFI->getImplicitBufferPtrUserSGPR())
          .addReg(ScratchRsrcReg, RegState::ImplicitDefine);
      } else {
        const MCInstrDesc &LoadDwordX2 = TII->get(AMDGPU::S_LOAD_DWORDX2_IMM);
 
        MachinePointerInfo PtrInfo(AMDGPUAS::CONSTANT_ADDRESS);
        auto *MMO = MF.getMachineMemOperand(
            PtrInfo,
            MachineMemOperand::MOLoad | MachineMemOperand::MOInvariant |
                MachineMemOperand::MODereferenceable,
            8, Align(4));
        BuildMI(MBB, I, DL, LoadDwordX2, Rsrc01)
          .addReg(MFI->getImplicitBufferPtrUserSGPR())
          .addImm(0) // offset
          .addImm(0) // cpol
          .addMemOperand(MMO)
          .addReg(ScratchRsrcReg, RegState::ImplicitDefine);
 
        MF.getRegInfo().addLiveIn(MFI->getImplicitBufferPtrUserSGPR());
        MBB.addLiveIn(MFI->getImplicitBufferPtrUserSGPR());
      }
    } else {
      Register Rsrc0 = TRI->getSubReg(ScratchRsrcReg, AMDGPU::sub0);
      Register Rsrc1 = TRI->getSubReg(ScratchRsrcReg, AMDGPU::sub1);
 
      BuildMI(MBB, I, DL, SMovB32, Rsrc0)
        .addExternalSymbol("SCRATCH_RSRC_DWORD0")
        .addReg(ScratchRsrcReg, RegState::ImplicitDefine);
 
      BuildMI(MBB, I, DL, SMovB32, Rsrc1)
        .addExternalSymbol("SCRATCH_RSRC_DWORD1")
        .addReg(ScratchRsrcReg, RegState::ImplicitDefine);
    }
 
    BuildMI(MBB, I, DL, SMovB32, Rsrc2)
        .addImm(Lo_32(Rsrc23))
        .addReg(ScratchRsrcReg, RegState::ImplicitDefine);
 
    BuildMI(MBB, I, DL, SMovB32, Rsrc3)
        .addImm(Hi_32(Rsrc23))
        .addReg(ScratchRsrcReg, RegState::ImplicitDefine);
  } else if (ST.isAmdHsaOrMesa(Fn)) {
    assert(PreloadedScratchRsrcReg);
 
    if (ScratchRsrcReg != PreloadedScratchRsrcReg) {
      BuildMI(MBB, I, DL, TII->get(AMDGPU::COPY), ScratchRsrcReg)
          .addReg(PreloadedScratchRsrcReg, RegState::Kill);
    }
  }
 
  // Add the scratch wave offset into the scratch RSRC.
  //
  // We only want to update the first 48 bits, which is the base address
  // pointer, without touching the adjacent 16 bits of flags. We know this add
  // cannot carry-out from bit 47, otherwise the scratch allocation would be
  // impossible to fit in the 48-bit global address space.
  //
  // TODO: Evaluate if it is better to just construct an SRD using the flat
  // scratch init and some constants rather than update the one we are passed.
  Register ScratchRsrcSub0 = TRI->getSubReg(ScratchRsrcReg, AMDGPU::sub0);
  Register ScratchRsrcSub1 = TRI->getSubReg(ScratchRsrcReg, AMDGPU::sub1);
 
  // We cannot Kill ScratchWaveOffsetReg here because we allow it to be used in
  // the kernel body via inreg arguments.
  BuildMI(MBB, I, DL, TII->get(AMDGPU::S_ADD_U32), ScratchRsrcSub0)
      .addReg(ScratchRsrcSub0)
      .addReg(ScratchWaveOffsetReg)
      .addReg(ScratchRsrcReg, RegState::ImplicitDefine);
  auto Addc = BuildMI(MBB, I, DL, TII->get(AMDGPU::S_ADDC_U32), ScratchRsrcSub1)
      .addReg(ScratchRsrcSub1)
      .addImm(0)
      .addReg(ScratchRsrcReg, RegState::ImplicitDefine);
  Addc->getOperand(3).setIsDead(); // Mark SCC as dead.
}
 
bool SIFrameLowering::isSupportedStackID(TargetStackID::Value ID) const {
  switch (ID) {
  case TargetStackID::Default:
  case TargetStackID::NoAlloc:
  case TargetStackID::SGPRSpill:
    return true;
  case TargetStackID::ScalableVector:
  case TargetStackID::ScalablePredicateVector:
  case TargetStackID::WasmLocal:
    return false;
  }
  llvm_unreachable("Invalid TargetStackID::Value");
}
 
void SIFrameLowering::emitPrologueEntryCFI(MachineBasicBlock &MBB,
                                           MachineBasicBlock::iterator MBBI,
                                           const DebugLoc &DL) const {
  const MachineFunction &MF = *MBB.getParent();
  const MachineRegisterInfo &MRI = MF.getRegInfo();
  const MCRegisterInfo *MCRI = MF.getContext().getRegisterInfo();
  const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
  const SIRegisterInfo &TRI = ST.getInstrInfo()->getRegisterInfo();
  MCRegister StackPtrReg =
      MF.getInfo<SIMachineFunctionInfo>()->getStackPtrOffsetReg();
 
  emitDefCFA(MBB, MBBI, DL, StackPtrReg, /*AspaceAlreadyDefined=*/true,
             MachineInstr::FrameSetup);
 
  buildCFIForRegToSGPRPairSpill(MBB, MBBI, DL, AMDGPU::PC_REG,
                                TRI.getReturnAddressReg(MF));
 
  BitVector IsCalleeSaved(TRI.getNumRegs());
  const MCPhysReg *CSRegs = MRI.getCalleeSavedRegs();
  for (unsigned I = 0; CSRegs[I]; ++I) {
    IsCalleeSaved.set(CSRegs[I]);
  }
  auto ProcessReg = [&](MCPhysReg Reg) {
    // VCC is not preserved across calls.
    if (Reg == AMDGPU::VCC || Reg == AMDGPU::VCC_LO || Reg == AMDGPU::VCC_HI)
      return;
    if (IsCalleeSaved.test(Reg) || !MRI.isPhysRegModified(Reg))
      return;
    MCRegister DwarfReg = MCRI->getDwarfRegNum(Reg, false);
    buildCFI(MBB, MBBI, DL,
             MCCFIInstruction::createUndefined(nullptr, DwarfReg));
  };
 
  // Emit CFI rules for caller saved Arch VGPRs which are clobbered
  unsigned NumArchVGPRs = ST.has1024AddressableVGPRs() ? 1024 : 256;
  for_each(AMDGPU::VGPR_32RegClass.getRegisters().take_front(NumArchVGPRs),
           ProcessReg);
 
  // Emit CFI rules for caller saved Accum VGPRs which are clobbered
  if (ST.hasMAIInsts()) {
    for_each(AMDGPU::AGPR_32RegClass.getRegisters(), ProcessReg);
  }
 
  // Emit CFI rules for caller saved SGPRs which are clobbered
  for_each(AMDGPU::SGPR_32RegClass.getRegisters(), ProcessReg);
}
 
// Activate only the inactive lanes when \p EnableInactiveLanes is true.
// Otherwise, activate all lanes. It returns the saved exec.
static Register buildScratchExecCopy(LiveRegUnits &LiveUnits,
                                     MachineFunction &MF,
                                     MachineBasicBlock &MBB,
                                     MachineBasicBlock::iterator MBBI,
                                     const DebugLoc &DL, bool IsProlog,
                                     bool EnableInactiveLanes) {
  Register ScratchExecCopy;
  MachineRegisterInfo &MRI = MF.getRegInfo();
  const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
  const SIInstrInfo *TII = ST.getInstrInfo();
  const SIRegisterInfo &TRI = TII->getRegisterInfo();
  SIMachineFunctionInfo *FuncInfo = MF.getInfo<SIMachineFunctionInfo>();
 
  initLiveUnits(LiveUnits, TRI, FuncInfo, MF, MBB, MBBI, IsProlog);
 
  if (FuncInfo->isWholeWaveFunction()) {
    // Whole wave functions already have a copy of the original EXEC mask that
    // we can use.
    assert(IsProlog && "Epilog should look at return, not setup");
    ScratchExecCopy =
        TII->getWholeWaveFunctionSetup(MF)->getOperand(0).getReg();
    assert(ScratchExecCopy && "Couldn't find copy of EXEC");
  } else {
    ScratchExecCopy = findScratchNonCalleeSaveRegister(
        MRI, LiveUnits, *TRI.getWaveMaskRegClass());
  }
 
  if (!ScratchExecCopy)
    report_fatal_error("failed to find free scratch register");
 
  LiveUnits.addReg(ScratchExecCopy);
 
  const unsigned SaveExecOpc =
      ST.isWave32() ? (EnableInactiveLanes ? AMDGPU::S_XOR_SAVEEXEC_B32
                                           : AMDGPU::S_OR_SAVEEXEC_B32)
                    : (EnableInactiveLanes ? AMDGPU::S_XOR_SAVEEXEC_B64
                                           : AMDGPU::S_OR_SAVEEXEC_B64);
  auto SaveExec =
      BuildMI(MBB, MBBI, DL, TII->get(SaveExecOpc), ScratchExecCopy).addImm(-1);
  SaveExec->getOperand(3).setIsDead(); // Mark SCC as dead.
 
  return ScratchExecCopy;
}
 
void SIFrameLowering::emitCSRSpillStores(
    MachineFunction &MF, MachineBasicBlock &MBB,
    MachineBasicBlock::iterator MBBI, const DebugLoc &DL,
    LiveRegUnits &LiveUnits, Register FrameReg, Register FramePtrRegScratchCopy,
    const bool NeedsFrameMoves) const {
  SIMachineFunctionInfo *FuncInfo = MF.getInfo<SIMachineFunctionInfo>();
  MachineFrameInfo &MFI = MF.getFrameInfo();
  const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
  const SIInstrInfo *TII = ST.getInstrInfo();
  const SIRegisterInfo &TRI = TII->getRegisterInfo();
  const MCRegisterInfo *MCRI = MF.getContext().getRegisterInfo();
  MachineRegisterInfo &MRI = MF.getRegInfo();
  const AMDGPU::LaneMaskConstants &LMC = AMDGPU::LaneMaskConstants::get(ST);
 
  // Spill Whole-Wave Mode VGPRs. Save only the inactive lanes of the scratch
  // registers. However, save all lanes of callee-saved VGPRs. Due to this, we
  // might end up flipping the EXEC bits twice.
  Register ScratchExecCopy;
  SmallVector<std::pair<Register, int>, 2> WWMCalleeSavedRegs, WWMScratchRegs;
  FuncInfo->splitWWMSpillRegisters(MF, WWMCalleeSavedRegs, WWMScratchRegs);
  if (!WWMScratchRegs.empty())
    ScratchExecCopy =
        buildScratchExecCopy(LiveUnits, MF, MBB, MBBI, DL,
                             /*IsProlog*/ true, /*EnableInactiveLanes*/ true);
 
  auto StoreWWMRegisters =
      [&](SmallVectorImpl<std::pair<Register, int>> &WWMRegs) {
        for (const auto &Reg : WWMRegs) {
          Register VGPR = Reg.first;
          int FI = Reg.second;
          buildPrologSpill(ST, TRI, *FuncInfo, LiveUnits, MF, MBB, MBBI, DL,
                           VGPR, FI, FrameReg);
          if (NeedsFrameMoves) {
            // We spill the entire VGPR, so we can get away with just cfi_offset
            buildCFI(MBB, MBBI, DL,
                     MCCFIInstruction::createOffset(
                         nullptr, MCRI->getDwarfRegNum(VGPR, false),
                         MFI.getObjectOffset(FI) * ST.getWavefrontSize()));
          }
        }
      };
 
  for (const Register Reg : make_first_range(WWMScratchRegs)) {
    if (!MRI.isReserved(Reg)) {
      MRI.addLiveIn(Reg);
      MBB.addLiveIn(Reg);
    }
  }
  StoreWWMRegisters(WWMScratchRegs);
 
  auto EnableAllLanes = [&]() {
    BuildMI(MBB, MBBI, DL, TII->get(LMC.MovOpc), LMC.ExecReg).addImm(-1);
  };
 
  if (!WWMCalleeSavedRegs.empty()) {
    if (ScratchExecCopy) {
      EnableAllLanes();
    } else {
      ScratchExecCopy = buildScratchExecCopy(LiveUnits, MF, MBB, MBBI, DL,
                                             /*IsProlog*/ true,
                                             /*EnableInactiveLanes*/ false);
    }
  }
 
  StoreWWMRegisters(WWMCalleeSavedRegs);
  if (FuncInfo->isWholeWaveFunction()) {
    // If we have already saved some WWM CSR registers, then the EXEC is already
    // -1 and we don't need to do anything else. Otherwise, save the original
    // EXEC into the setup register and set EXEC to -1 here.
    if (!ScratchExecCopy)
      buildScratchExecCopy(LiveUnits, MF, MBB, MBBI, DL, /*IsProlog*/ true,
                           /*EnableInactiveLanes*/ false);
    else if (WWMCalleeSavedRegs.empty())
      EnableAllLanes();
  } else if (ScratchExecCopy) {
    // FIXME: Split block and make terminator.
    BuildMI(MBB, MBBI, DL, TII->get(LMC.MovOpc), LMC.ExecReg)
        .addReg(ScratchExecCopy, RegState::Kill);
    LiveUnits.addReg(ScratchExecCopy);
  }
 
  Register FramePtrReg = FuncInfo->getFrameOffsetReg();
 
  for (const auto &Spill : FuncInfo->getPrologEpilogSGPRSpills()) {
    // Special handle FP spill:
    // Skip if FP is saved to a scratch SGPR, the save has already been emitted.
    // Otherwise, FP has been moved to a temporary register and spill it
    // instead.
    bool IsFramePtrPrologSpill = Spill.first == FramePtrReg;
    Register Reg = IsFramePtrPrologSpill ? FramePtrRegScratchCopy : Spill.first;
    if (!Reg)
      continue;
 
    PrologEpilogSGPRSpillBuilder SB(Reg, Spill.second, MBB, MBBI, DL, TII, TRI,
                                    LiveUnits, FrameReg, IsFramePtrPrologSpill);
    SB.save();
  }
 
  // If a copy to scratch SGPR has been chosen for any of the SGPR spills, make
  // such scratch registers live throughout the function.
  SmallVector<Register, 1> ScratchSGPRs;
  FuncInfo->getAllScratchSGPRCopyDstRegs(ScratchSGPRs);
  if (!ScratchSGPRs.empty()) {
    for (MachineBasicBlock &MBB : MF) {
      for (MCPhysReg Reg : ScratchSGPRs)
        MBB.addLiveIn(Reg);
 
      MBB.sortUniqueLiveIns();
    }
    if (!LiveUnits.empty()) {
      for (MCPhysReg Reg : ScratchSGPRs)
        LiveUnits.addReg(Reg);
    }
  }
 
  // Remove the spill entry created for EXEC. It is needed only for CFISaves in
  // the prologue.
  if (TRI.isCFISavedRegsSpillEnabled())
    FuncInfo->removePrologEpilogSGPRSpillEntry(TRI.getExec());
}
 
void SIFrameLowering::emitCSRSpillRestores(
    MachineFunction &MF, MachineBasicBlock &MBB,
    MachineBasicBlock::iterator MBBI, const DebugLoc &DL,
    LiveRegUnits &LiveUnits, Register FrameReg,
    Register FramePtrRegScratchCopy) const {
  const SIMachineFunctionInfo *FuncInfo = MF.getInfo<SIMachineFunctionInfo>();
  const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
  const SIInstrInfo *TII = ST.getInstrInfo();
  const SIRegisterInfo &TRI = TII->getRegisterInfo();
  const AMDGPU::LaneMaskConstants &LMC = AMDGPU::LaneMaskConstants::get(ST);
  Register FramePtrReg = FuncInfo->getFrameOffsetReg();
 
  for (const auto &Spill : FuncInfo->getPrologEpilogSGPRSpills()) {
    // Special handle FP restore:
    // Skip if FP needs to be restored from the scratch SGPR. Otherwise, restore
    // the FP value to a temporary register. The frame pointer should be
    // overwritten only at the end when all other spills are restored from
    // current frame.
    Register Reg =
        Spill.first == FramePtrReg ? FramePtrRegScratchCopy : Spill.first;
    if (!Reg)
      continue;
 
    PrologEpilogSGPRSpillBuilder SB(Reg, Spill.second, MBB, MBBI, DL, TII, TRI,
                                    LiveUnits, FrameReg);
    SB.restore();
  }
 
  // Restore Whole-Wave Mode VGPRs. Restore only the inactive lanes of the
  // scratch registers. However, restore all lanes of callee-saved VGPRs. Due to
  // this, we might end up flipping the EXEC bits twice.
  Register ScratchExecCopy;
  SmallVector<std::pair<Register, int>, 2> WWMCalleeSavedRegs, WWMScratchRegs;
  FuncInfo->splitWWMSpillRegisters(MF, WWMCalleeSavedRegs, WWMScratchRegs);
  auto RestoreWWMRegisters =
      [&](SmallVectorImpl<std::pair<Register, int>> &WWMRegs) {
        for (const auto &Reg : WWMRegs) {
          Register VGPR = Reg.first;
          int FI = Reg.second;
          buildEpilogRestore(ST, TRI, *FuncInfo, LiveUnits, MF, MBB, MBBI, DL,
                             VGPR, FI, FrameReg);
        }
      };
 
  if (FuncInfo->isWholeWaveFunction()) {
    // For whole wave functions, the EXEC is already -1 at this point.
    // Therefore, we can restore the CSR WWM registers right away.
    RestoreWWMRegisters(WWMCalleeSavedRegs);
 
    // The original EXEC is the first operand of the return instruction.
    MachineInstr &Return = MBB.instr_back();
    unsigned Opcode = Return.getOpcode();
    switch (Opcode) {
    case AMDGPU::SI_WHOLE_WAVE_FUNC_RETURN:
      Opcode = AMDGPU::SI_RETURN;
      break;
    case AMDGPU::SI_TCRETURN_GFX_WholeWave:
      Opcode = AMDGPU::SI_TCRETURN_GFX;
      break;
    default:
      llvm_unreachable("Unexpected return inst");
    }
    Register OrigExec = Return.getOperand(0).getReg();
 
    if (!WWMScratchRegs.empty()) {
      BuildMI(MBB, MBBI, DL, TII->get(LMC.XorOpc), LMC.ExecReg)
          .addReg(OrigExec)
          .addImm(-1);
      RestoreWWMRegisters(WWMScratchRegs);
    }
 
    // Restore original EXEC.
    BuildMI(MBB, MBBI, DL, TII->get(LMC.MovOpc), LMC.ExecReg).addReg(OrigExec);
 
    // Drop the first operand and update the opcode.
    Return.removeOperand(0);
    Return.setDesc(TII->get(Opcode));
 
    return;
  }
 
  if (!WWMScratchRegs.empty()) {
    ScratchExecCopy =
        buildScratchExecCopy(LiveUnits, MF, MBB, MBBI, DL,
                             /*IsProlog=*/false, /*EnableInactiveLanes=*/true);
  }
  RestoreWWMRegisters(WWMScratchRegs);
  if (!WWMCalleeSavedRegs.empty()) {
    if (ScratchExecCopy) {
      BuildMI(MBB, MBBI, DL, TII->get(LMC.MovOpc), LMC.ExecReg).addImm(-1);
    } else {
      ScratchExecCopy = buildScratchExecCopy(LiveUnits, MF, MBB, MBBI, DL,
                                             /*IsProlog*/ false,
                                             /*EnableInactiveLanes*/ false);
    }
  }
 
  RestoreWWMRegisters(WWMCalleeSavedRegs);
  if (ScratchExecCopy) {
    // FIXME: Split block and make terminator.
    BuildMI(MBB, MBBI, DL, TII->get(LMC.MovOpc), LMC.ExecReg)
        .addReg(ScratchExecCopy, RegState::Kill);
  }
}
 
void SIFrameLowering::emitPrologue(MachineFunction &MF,
                                   MachineBasicBlock &MBB) const {
  SIMachineFunctionInfo *FuncInfo = MF.getInfo<SIMachineFunctionInfo>();
  if (FuncInfo->isEntryFunction()) {
    emitEntryFunctionPrologue(MF, MBB);
    return;
  }
 
  MachineFrameInfo &MFI = MF.getFrameInfo();
  const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
  const SIInstrInfo *TII = ST.getInstrInfo();
  const SIRegisterInfo &TRI = TII->getRegisterInfo();
  MachineRegisterInfo &MRI = MF.getRegInfo();
 
  Register StackPtrReg = FuncInfo->getStackPtrOffsetReg();
  Register FramePtrReg = FuncInfo->getFrameOffsetReg();
  Register BasePtrReg =
      TRI.hasBasePointer(MF) ? TRI.getBaseRegister() : Register();
  LiveRegUnits LiveUnits;
 
  MachineBasicBlock::iterator MBBI = MBB.begin();
  // DebugLoc must be unknown since the first instruction with DebugLoc is used
  // to determine the end of the prologue.
  DebugLoc DL;
 
  bool HasFP = false;
  bool HasBP = false;
  uint32_t NumBytes = MFI.getStackSize();
  uint32_t RoundedSize = NumBytes;
 
  // Functions that never return don't need to save and restore the FP or BP.
  const Function &F = MF.getFunction();
  bool SavesStackRegs =
      !F.hasFnAttribute(Attribute::NoReturn) && !FuncInfo->isChainFunction();
 
  const bool NeedsFrameMoves = MF.needsFrameMoves();
 
  if (NeedsFrameMoves)
    emitPrologueEntryCFI(MBB, MBBI, DL);
 
  if (TRI.hasStackRealignment(MF))
    HasFP = true;
 
  Register FramePtrRegScratchCopy;
  if (!HasFP && !hasFP(MF)) {
    // Emit the CSR spill stores with SP base register.
    emitCSRSpillStores(MF, MBB, MBBI, DL, LiveUnits, StackPtrReg,
                       FramePtrRegScratchCopy, NeedsFrameMoves);
  } else if (SavesStackRegs) {
    // CSR spill stores will use FP as base register.
    Register SGPRForFPSaveRestoreCopy =
        FuncInfo->getScratchSGPRCopyDstReg(FramePtrReg);
 
    initLiveUnits(LiveUnits, TRI, FuncInfo, MF, MBB, MBBI, /*IsProlog*/ true);
    if (SGPRForFPSaveRestoreCopy) {
      // Copy FP to the scratch register now and emit the CFI entry. It avoids
      // the extra FP copy needed in the other two cases when FP is spilled to
      // memory or to a VGPR lane.
      PrologEpilogSGPRSpillBuilder SB(
          FramePtrReg,
          FuncInfo->getPrologEpilogSGPRSaveRestoreInfo(FramePtrReg), MBB, MBBI,
          DL, TII, TRI, LiveUnits, FramePtrReg,
          /*IsFramePtrPrologSpill*/ true);
      SB.save();
      LiveUnits.addReg(SGPRForFPSaveRestoreCopy);
    } else {
      // Copy FP into a new scratch register so that its previous value can be
      // spilled after setting up the new frame.
      FramePtrRegScratchCopy = findScratchNonCalleeSaveRegister(
          MRI, LiveUnits, AMDGPU::SReg_32_XM0_XEXECRegClass);
      if (!FramePtrRegScratchCopy)
        report_fatal_error("failed to find free scratch register");
 
      LiveUnits.addReg(FramePtrRegScratchCopy);
      BuildMI(MBB, MBBI, DL, TII->get(AMDGPU::COPY), FramePtrRegScratchCopy)
          .addReg(FramePtrReg);
    }
  }
 
  if (HasFP) {
    const unsigned Alignment = MFI.getMaxAlign().value();
 
    RoundedSize += Alignment;
    if (LiveUnits.empty()) {
      LiveUnits.init(TRI);
      LiveUnits.addLiveIns(MBB);
    }
 
    // s_add_i32 s33, s32, NumBytes
    // s_and_b32 s33, s33, 0b111...0000
    BuildMI(MBB, MBBI, DL, TII->get(AMDGPU::S_ADD_I32), FramePtrReg)
        .addReg(StackPtrReg)
        .addImm((Alignment - 1) * getScratchScaleFactor(ST))
        .setMIFlag(MachineInstr::FrameSetup);
    auto And = BuildMI(MBB, MBBI, DL, TII->get(AMDGPU::S_AND_B32), FramePtrReg)
        .addReg(FramePtrReg, RegState::Kill)
        .addImm(-Alignment * getScratchScaleFactor(ST))
        .setMIFlag(MachineInstr::FrameSetup);
    And->getOperand(3).setIsDead(); // Mark SCC as dead.
    FuncInfo->setIsStackRealigned(true);
  } else if ((HasFP = hasFP(MF))) {
    BuildMI(MBB, MBBI, DL, TII->get(AMDGPU::COPY), FramePtrReg)
        .addReg(StackPtrReg)
        .setMIFlag(MachineInstr::FrameSetup);
  }
 
  // If FP is used, emit the CSR spills with FP base register.
  if (HasFP) {
    emitCSRSpillStores(MF, MBB, MBBI, DL, LiveUnits, FramePtrReg,
                       FramePtrRegScratchCopy, NeedsFrameMoves);
    if (FramePtrRegScratchCopy)
      LiveUnits.removeReg(FramePtrRegScratchCopy);
  }
 
  // If we need a base pointer, set it up here. It's whatever the value of
  // the stack pointer is at this point. Any variable size objects will be
  // allocated after this, so we can still use the base pointer to reference
  // the incoming arguments.
  if ((HasBP = TRI.hasBasePointer(MF))) {
    BuildMI(MBB, MBBI, DL, TII->get(AMDGPU::COPY), BasePtrReg)
        .addReg(StackPtrReg)
        .setMIFlag(MachineInstr::FrameSetup);
  }
 
  if (HasFP) {
    if (NeedsFrameMoves)
      emitDefCFA(MBB, MBBI, DL, FramePtrReg, /*AspaceAlreadyDefined=*/false,
                 MachineInstr::FrameSetup);
  }
 
  if (HasFP && RoundedSize != 0) {
    auto Add = BuildMI(MBB, MBBI, DL, TII->get(AMDGPU::S_ADD_I32), StackPtrReg)
        .addReg(StackPtrReg)
        .addImm(RoundedSize * getScratchScaleFactor(ST))
        .setMIFlag(MachineInstr::FrameSetup);
    Add->getOperand(3).setIsDead(); // Mark SCC as dead.
  }
 
  bool FPSaved = FuncInfo->hasPrologEpilogSGPRSpillEntry(FramePtrReg);
  (void)FPSaved;
  assert((!HasFP || FPSaved || !SavesStackRegs) &&
         "Needed to save FP but didn't save it anywhere");
 
  // If we allow spilling to AGPRs we may have saved FP but then spill
  // everything into AGPRs instead of the stack.
  assert((HasFP || !FPSaved || !SavesStackRegs || EnableSpillVGPRToAGPR) &&
         "Saved FP but didn't need it");
 
  bool BPSaved = FuncInfo->hasPrologEpilogSGPRSpillEntry(BasePtrReg);
  (void)BPSaved;
  assert((!HasBP || BPSaved || !SavesStackRegs) &&
         "Needed to save BP but didn't save it anywhere");
 
  assert((HasBP || !BPSaved) && "Saved BP but didn't need it");
 
  if (FuncInfo->isWholeWaveFunction()) {
    // SI_WHOLE_WAVE_FUNC_SETUP has outlived its purpose.
    TII->getWholeWaveFunctionSetup(MF)->eraseFromParent();
  }
}
 
void SIFrameLowering::emitEpilogue(MachineFunction &MF,
                                   MachineBasicBlock &MBB) const {
  const SIMachineFunctionInfo *FuncInfo = MF.getInfo<SIMachineFunctionInfo>();
  if (FuncInfo->isEntryFunction())
    return;
 
  const MachineFrameInfo &MFI = MF.getFrameInfo();
  if (FuncInfo->isChainFunction() && !MFI.hasTailCall())
    return;
 
  const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
  const SIInstrInfo *TII = ST.getInstrInfo();
  const SIRegisterInfo &TRI = TII->getRegisterInfo();
  MachineRegisterInfo &MRI = MF.getRegInfo();
  LiveRegUnits LiveUnits;
  // Get the insert location for the epilogue. If there were no terminators in
  // the block, get the last instruction.
  MachineBasicBlock::iterator MBBI = MBB.end();
  DebugLoc DL;
  if (!MBB.empty()) {
    MBBI = MBB.getLastNonDebugInstr();
    if (MBBI != MBB.end())
      DL = MBBI->getDebugLoc();
 
    MBBI = MBB.getFirstTerminator();
  }
 
  uint32_t NumBytes = MFI.getStackSize();
  uint32_t RoundedSize = FuncInfo->isStackRealigned()
                             ? NumBytes + MFI.getMaxAlign().value()
                             : NumBytes;
  const Register StackPtrReg = FuncInfo->getStackPtrOffsetReg();
  Register FramePtrReg = FuncInfo->getFrameOffsetReg();
  bool FPSaved = FuncInfo->hasPrologEpilogSGPRSpillEntry(FramePtrReg);
 
  if (RoundedSize != 0) {
    if (TRI.hasBasePointer(MF)) {
      BuildMI(MBB, MBBI, DL, TII->get(AMDGPU::COPY), StackPtrReg)
          .addReg(TRI.getBaseRegister())
          .setMIFlag(MachineInstr::FrameDestroy);
    } else if (hasFP(MF)) {
      BuildMI(MBB, MBBI, DL, TII->get(AMDGPU::COPY), StackPtrReg)
          .addReg(FramePtrReg)
          .setMIFlag(MachineInstr::FrameDestroy);
    }
  }
 
  Register FramePtrRegScratchCopy;
  Register SGPRForFPSaveRestoreCopy =
      FuncInfo->getScratchSGPRCopyDstReg(FramePtrReg);
  if (FPSaved) {
    // CSR spill restores should use FP as base register. If
    // SGPRForFPSaveRestoreCopy is not true, restore the previous value of FP
    // into a new scratch register and copy to FP later when other registers are
    // restored from the current stack frame.
    initLiveUnits(LiveUnits, TRI, FuncInfo, MF, MBB, MBBI, /*IsProlog*/ false);
    if (SGPRForFPSaveRestoreCopy) {
      LiveUnits.addReg(SGPRForFPSaveRestoreCopy);
    } else {
      FramePtrRegScratchCopy = findScratchNonCalleeSaveRegister(
          MRI, LiveUnits, AMDGPU::SReg_32_XM0_XEXECRegClass);
      if (!FramePtrRegScratchCopy)
        report_fatal_error("failed to find free scratch register");
 
      LiveUnits.addReg(FramePtrRegScratchCopy);
    }
 
    emitCSRSpillRestores(MF, MBB, MBBI, DL, LiveUnits, FramePtrReg,
                         FramePtrRegScratchCopy);
  }
 
  if (hasFP(MF) && MF.needsFrameMoves()) {
    emitDefCFA(MBB, MBBI, DL, StackPtrReg, /*AspaceAlreadyDefined=*/false,
               MachineInstr::FrameDestroy);
  }
 
  if (FPSaved) {
    // Insert the copy to restore FP.
    Register SrcReg = SGPRForFPSaveRestoreCopy ? SGPRForFPSaveRestoreCopy
                                               : FramePtrRegScratchCopy;
    MachineInstrBuilder MIB =
        BuildMI(MBB, MBBI, DL, TII->get(AMDGPU::COPY), FramePtrReg)
            .addReg(SrcReg);
    if (SGPRForFPSaveRestoreCopy)
      MIB.setMIFlag(MachineInstr::FrameDestroy);
  } else {
    // Insert the CSR spill restores with SP as the base register.
    emitCSRSpillRestores(MF, MBB, MBBI, DL, LiveUnits, StackPtrReg,
                         FramePtrRegScratchCopy);
  }
}
 
#ifndef NDEBUG
static bool allSGPRSpillsAreDead(const MachineFunction &MF) {
  const MachineFrameInfo &MFI = MF.getFrameInfo();
  const SIMachineFunctionInfo *FuncInfo = MF.getInfo<SIMachineFunctionInfo>();
  for (int I = MFI.getObjectIndexBegin(), E = MFI.getObjectIndexEnd();
       I != E; ++I) {
    if (!MFI.isDeadObjectIndex(I) &&
        MFI.getStackID(I) == TargetStackID::SGPRSpill &&
        !FuncInfo->checkIndexInPrologEpilogSGPRSpills(I)) {
      return false;
    }
  }
 
  return true;
}
#endif
 
StackOffset SIFrameLowering::getFrameIndexReference(const MachineFunction &MF,
                                                    int FI,
                                                    Register &FrameReg) const {
  const SIRegisterInfo *RI = MF.getSubtarget<GCNSubtarget>().getRegisterInfo();
 
  FrameReg = RI->getFrameRegister(MF);
  return StackOffset::getFixed(MF.getFrameInfo().getObjectOffset(FI));
}
 
void SIFrameLowering::processFunctionBeforeFrameFinalized(
  MachineFunction &MF,
  RegScavenger *RS) const {
  MachineFrameInfo &MFI = MF.getFrameInfo();
 
  const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
  const SIInstrInfo *TII = ST.getInstrInfo();
  const SIRegisterInfo *TRI = ST.getRegisterInfo();
  MachineRegisterInfo &MRI = MF.getRegInfo();
  SIMachineFunctionInfo *FuncInfo = MF.getInfo<SIMachineFunctionInfo>();
 
  const bool SpillVGPRToAGPR = ST.hasMAIInsts() && FuncInfo->hasSpilledVGPRs()
                               && EnableSpillVGPRToAGPR;
 
  if (SpillVGPRToAGPR) {
    // To track the spill frame indices handled in this pass.
    BitVector SpillFIs(MFI.getObjectIndexEnd(), false);
    BitVector NonVGPRSpillFIs(MFI.getObjectIndexEnd(), false);
 
    bool SeenDbgInstr = false;
 
    for (MachineBasicBlock &MBB : MF) {
      for (MachineInstr &MI : llvm::make_early_inc_range(MBB)) {
        int FrameIndex;
        if (MI.isDebugInstr())
          SeenDbgInstr = true;
 
        if (TII->isVGPRSpill(MI)) {
          // Try to eliminate stack used by VGPR spills before frame
          // finalization.
          unsigned FIOp = AMDGPU::getNamedOperandIdx(MI.getOpcode(),
                                                     AMDGPU::OpName::vaddr);
          int FI = MI.getOperand(FIOp).getIndex();
          Register VReg =
            TII->getNamedOperand(MI, AMDGPU::OpName::vdata)->getReg();
          if (FuncInfo->allocateVGPRSpillToAGPR(MF, FI,
                                                TRI->isAGPR(MRI, VReg))) {
            assert(RS != nullptr);
            RS->enterBasicBlockEnd(MBB);
            RS->backward(std::next(MI.getIterator()));
            TRI->eliminateFrameIndex(MI, 0, FIOp, RS);
            SpillFIs.set(FI);
            continue;
          }
        } else if (TII->isStoreToStackSlot(MI, FrameIndex) ||
                   TII->isLoadFromStackSlot(MI, FrameIndex))
          if (!MFI.isFixedObjectIndex(FrameIndex))
            NonVGPRSpillFIs.set(FrameIndex);
      }
    }
 
    // Stack slot coloring may assign different objects to the same stack slot.
    // If not, then the VGPR to AGPR spill slot is dead.
    for (unsigned FI : SpillFIs.set_bits())
      if (!NonVGPRSpillFIs.test(FI))
        FuncInfo->setVGPRToAGPRSpillDead(FI);
 
    for (MachineBasicBlock &MBB : MF) {
      for (MCPhysReg Reg : FuncInfo->getVGPRSpillAGPRs())
        MBB.addLiveIn(Reg);
 
      for (MCPhysReg Reg : FuncInfo->getAGPRSpillVGPRs())
        MBB.addLiveIn(Reg);
 
      MBB.sortUniqueLiveIns();
 
      if (!SpillFIs.empty() && SeenDbgInstr)
        clearDebugInfoForSpillFIs(MFI, MBB, SpillFIs);
    }
  }
 
  // At this point we've already allocated all spilled SGPRs to VGPRs if we
  // can. Any remaining SGPR spills will go to memory, so move them back to the
  // default stack.
  bool HaveSGPRToVMemSpill =
      FuncInfo->removeDeadFrameIndices(MFI, /*ResetSGPRSpillStackIDs*/ true);
  assert(allSGPRSpillsAreDead(MF) &&
         "SGPR spill should have been removed in SILowerSGPRSpills");
 
  // FIXME: The other checks should be redundant with allStackObjectsAreDead,
  // but currently hasNonSpillStackObjects is set only from source
  // allocas. Stack temps produced from legalization are not counted currently.
  if (!allStackObjectsAreDead(MFI)) {
    assert(RS && "RegScavenger required if spilling");
 
    // Add an emergency spill slot
    RS->addScavengingFrameIndex(FuncInfo->getScavengeFI(MFI, *TRI));
 
    // If we are spilling SGPRs to memory with a large frame, we may need a
    // second VGPR emergency frame index.
    if (HaveSGPRToVMemSpill &&
        allocateScavengingFrameIndexesNearIncomingSP(MF)) {
      RS->addScavengingFrameIndex(MFI.CreateSpillStackObject(4, Align(4)));
    }
  }
}
 
void SIFrameLowering::processFunctionBeforeFrameIndicesReplaced(
    MachineFunction &MF, RegScavenger *RS) const {
  const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
  const SIRegisterInfo *TRI = ST.getRegisterInfo();
  MachineRegisterInfo &MRI = MF.getRegInfo();
  SIMachineFunctionInfo *FuncInfo = MF.getInfo<SIMachineFunctionInfo>();
 
  if (ST.hasMAIInsts() && !ST.hasGFX90AInsts()) {
    // On gfx908, we had initially reserved highest available VGPR for AGPR
    // copy. Now since we are done with RA, check if there exist an unused VGPR
    // which is lower than the eariler reserved VGPR before RA. If one exist,
    // use it for AGPR copy instead of one reserved before RA.
    Register VGPRForAGPRCopy = FuncInfo->getVGPRForAGPRCopy();
    Register UnusedLowVGPR =
        TRI->findUnusedRegister(MRI, &AMDGPU::VGPR_32RegClass, MF);
    if (UnusedLowVGPR && (TRI->getHWRegIndex(UnusedLowVGPR) <
                          TRI->getHWRegIndex(VGPRForAGPRCopy))) {
      // Reserve this newly identified VGPR (for AGPR copy)
      // reserved registers should already be frozen at this point
      // so we can avoid calling MRI.freezeReservedRegs and just use
      // MRI.reserveReg
      FuncInfo->setVGPRForAGPRCopy(UnusedLowVGPR);
      MRI.reserveReg(UnusedLowVGPR, TRI);
    }
  }
  // We initally reserved the highest available SGPR pair for long branches
  // now, after RA, we shift down to a lower unused one if one exists
  Register LongBranchReservedReg = FuncInfo->getLongBranchReservedReg();
  Register UnusedLowSGPR =
      TRI->findUnusedRegister(MRI, &AMDGPU::SGPR_64RegClass, MF);
  // If LongBranchReservedReg is null then we didn't find a long branch
  // and never reserved a register to begin with so there is nothing to
  // shift down. Then if UnusedLowSGPR is null, there isn't available lower
  // register to use so just keep the original one we set.
  if (LongBranchReservedReg && UnusedLowSGPR) {
    FuncInfo->setLongBranchReservedReg(UnusedLowSGPR);
    MRI.reserveReg(UnusedLowSGPR, TRI);
  }
}
 
// The special SGPR spills like the one needed for FP, BP or any reserved
// registers delayed until frame lowering.
void SIFrameLowering::determinePrologEpilogSGPRSaves(
    MachineFunction &MF, BitVector &SavedVGPRs,
    bool NeedExecCopyReservedReg) const {
  MachineFrameInfo &FrameInfo = MF.getFrameInfo();
  MachineRegisterInfo &MRI = MF.getRegInfo();
  SIMachineFunctionInfo *MFI = MF.getInfo<SIMachineFunctionInfo>();
  const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
  const SIRegisterInfo *TRI = ST.getRegisterInfo();
  LiveRegUnits LiveUnits;
  LiveUnits.init(*TRI);
  // Initially mark callee saved registers as used so we will not choose them
  // while looking for scratch SGPRs.
  const MCPhysReg *CSRegs = MF.getRegInfo().getCalleeSavedRegs();
  for (unsigned I = 0; CSRegs[I]; ++I)
    LiveUnits.addReg(CSRegs[I]);
 
  const TargetRegisterClass &RC = *TRI->getWaveMaskRegClass();
 
  Register ReservedRegForExecCopy = MFI->getSGPRForEXECCopy();
  if (NeedExecCopyReservedReg ||
      (ReservedRegForExecCopy &&
       MRI.isPhysRegUsed(ReservedRegForExecCopy, /*SkipRegMaskTest=*/true))) {
    MRI.reserveReg(ReservedRegForExecCopy, TRI);
    Register UnusedScratchReg = findUnusedRegister(MRI, LiveUnits, RC);
    if (UnusedScratchReg) {
      // If found any unused scratch SGPR, reserve the register itself for Exec
      // copy and there is no need for any spills in that case.
      MFI->setSGPRForEXECCopy(UnusedScratchReg);
      MRI.replaceRegWith(ReservedRegForExecCopy, UnusedScratchReg);
      LiveUnits.addReg(UnusedScratchReg);
    } else {
      // Needs spill.
      assert(!MFI->hasPrologEpilogSGPRSpillEntry(ReservedRegForExecCopy) &&
             "Re-reserving spill slot for EXEC copy register");
      getVGPRSpillLaneOrTempRegister(MF, LiveUnits, ReservedRegForExecCopy, RC,
                                     /*IncludeScratchCopy=*/false);
    }
  } else if (ReservedRegForExecCopy) {
    // Reset it at this point. There are no whole-wave copies and spills
    // encountered.
    MFI->setSGPRForEXECCopy(AMDGPU::NoRegister);
  }
 
  if (TRI->isCFISavedRegsSpillEnabled()) {
    Register Exec = TRI->getExec();
    assert(!MFI->hasPrologEpilogSGPRSpillEntry(Exec) &&
           "Re-reserving spill slot for EXEC");
    getVGPRSpillLaneOrTempRegister(MF, LiveUnits, Exec, RC);
  }
 
  // Functions that don't return to the caller don't need to preserve
  // the FP and BP.
  const Function &F = MF.getFunction();
  if (F.hasFnAttribute(Attribute::NoReturn) ||
      AMDGPU::isChainCC(F.getCallingConv()))
    return;
 
  // hasFP only knows about stack objects that already exist. We're now
  // determining the stack slots that will be created, so we have to predict
  // them. Stack objects force FP usage with calls.
  //
  // Note a new VGPR CSR may be introduced if one is used for the spill, but we
  // don't want to report it here.
  //
  // FIXME: Is this really hasReservedCallFrame?
  const bool WillHaveFP =
      FrameInfo.hasCalls() &&
      (SavedVGPRs.any() || !allStackObjectsAreDead(FrameInfo));
 
  if (WillHaveFP || hasFP(MF)) {
    Register FramePtrReg = MFI->getFrameOffsetReg();
    assert(!MFI->hasPrologEpilogSGPRSpillEntry(FramePtrReg) &&
           "Re-reserving spill slot for FP");
    getVGPRSpillLaneOrTempRegister(MF, LiveUnits, FramePtrReg);
  }
 
  if (TRI->hasBasePointer(MF)) {
    Register BasePtrReg = TRI->getBaseRegister();
    assert(!MFI->hasPrologEpilogSGPRSpillEntry(BasePtrReg) &&
           "Re-reserving spill slot for BP");
    getVGPRSpillLaneOrTempRegister(MF, LiveUnits, BasePtrReg);
  }
}
 
// Only report VGPRs to generic code.
void SIFrameLowering::determineCalleeSaves(MachineFunction &MF,
                                           BitVector &SavedVGPRs,
                                           RegScavenger *RS) const {
  SIMachineFunctionInfo *MFI = MF.getInfo<SIMachineFunctionInfo>();
 
  // If this is a function with the amdgpu_cs_chain[_preserve] calling
  // convention and it doesn't contain any calls to llvm.amdgcn.cs.chain, then
  // we don't need to save and restore anything.
  if (MFI->isChainFunction() && !MF.getFrameInfo().hasTailCall())
    return;
 
  TargetFrameLowering::determineCalleeSaves(MF, SavedVGPRs, RS);
 
  const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
  const SIRegisterInfo *TRI = ST.getRegisterInfo();
  const SIInstrInfo *TII = ST.getInstrInfo();
  bool NeedExecCopyReservedReg = false;
 
  MachineInstr *ReturnMI = nullptr;
  for (MachineBasicBlock &MBB : MF) {
    for (MachineInstr &MI : MBB) {
      // TODO: Walking through all MBBs here would be a bad heuristic. Better
      // handle them elsewhere.
      if (TII->isWWMRegSpillOpcode(MI.getOpcode()))
        NeedExecCopyReservedReg = true;
      else if (MI.getOpcode() == AMDGPU::SI_RETURN ||
               MI.getOpcode() == AMDGPU::SI_RETURN_TO_EPILOG ||
               MI.getOpcode() == AMDGPU::SI_WHOLE_WAVE_FUNC_RETURN ||
               (MFI->isChainFunction() &&
                TII->isChainCallOpcode(MI.getOpcode()))) {
        // We expect all return to be the same size.
        assert(!ReturnMI ||
               (count_if(MI.operands(), [](auto Op) { return Op.isReg(); }) ==
                count_if(ReturnMI->operands(), [](auto Op) { return Op.isReg(); })));
        ReturnMI = &MI;
      }
    }
  }
 
  SmallVector<Register> SortedWWMVGPRs;
  for (Register Reg : MFI->getWWMReservedRegs()) {
    // The shift-back is needed only for the VGPRs used for SGPR spills and they
    // are of 32-bit size. SIPreAllocateWWMRegs pass can add tuples into WWM
    // reserved registers.
    const TargetRegisterClass *RC = TRI->getPhysRegBaseClass(Reg);
    if (TRI->getRegSizeInBits(*RC) != 32)
      continue;
    SortedWWMVGPRs.push_back(Reg);
  }
 
  sort(SortedWWMVGPRs, std::greater<Register>());
  MFI->shiftWwmVGPRsToLowestRange(MF, SortedWWMVGPRs, SavedVGPRs);
 
  if (MFI->isEntryFunction())
    return;
 
  if (MFI->isWholeWaveFunction()) {
    // In practice, all the VGPRs are WWM registers, and we will need to save at
    // least their inactive lanes. Add them to WWMReservedRegs.
    assert(!NeedExecCopyReservedReg &&
           "Whole wave functions can use the reg mapped for their i1 argument");
 
    unsigned NumArchVGPRs = ST.getAddressableNumArchVGPRs();
    for (MCRegister Reg :
         AMDGPU::VGPR_32RegClass.getRegisters().take_front(NumArchVGPRs))
      if (MF.getRegInfo().isPhysRegModified(Reg)) {
        MFI->reserveWWMRegister(Reg);
        MF.begin()->addLiveIn(Reg);
      }
    MF.begin()->sortUniqueLiveIns();
  }
 
  // Remove any VGPRs used in the return value because these do not need to be saved.
  // This prevents CSR restore from clobbering return VGPRs.
  if (ReturnMI) {
    for (auto &Op : ReturnMI->operands()) {
      if (Op.isReg())
        SavedVGPRs.reset(Op.getReg());
    }
  }
 
  // Create the stack objects for WWM registers now.
  for (Register Reg : MFI->getWWMReservedRegs()) {
    const TargetRegisterClass *RC = TRI->getPhysRegBaseClass(Reg);
    MFI->allocateWWMSpill(MF, Reg, TRI->getSpillSize(*RC),
                          TRI->getSpillAlign(*RC));
  }
 
  // Ignore the SGPRs the default implementation found.
  SavedVGPRs.clearBitsNotInMask(TRI->getAllVectorRegMask());
 
  // Do not save AGPRs prior to GFX90A because there was no easy way to do so.
  // In gfx908 there was do AGPR loads and stores and thus spilling also
  // require a temporary VGPR.
  if (!ST.hasGFX90AInsts())
    SavedVGPRs.clearBitsInMask(TRI->getAllAGPRRegMask());
 
  determinePrologEpilogSGPRSaves(MF, SavedVGPRs, NeedExecCopyReservedReg);
 
  // The Whole-Wave VGPRs need to be specially inserted in the prolog, so don't
  // allow the default insertion to handle them.
  for (auto &Reg : MFI->getWWMSpills())
    SavedVGPRs.reset(Reg.first);
}
 
void SIFrameLowering::determineCalleeSavesSGPR(MachineFunction &MF,
                                               BitVector &SavedRegs,
                                               RegScavenger *RS) const {
  TargetFrameLowering::determineCalleeSaves(MF, SavedRegs, RS);
  const SIMachineFunctionInfo *MFI = MF.getInfo<SIMachineFunctionInfo>();
  if (MFI->isEntryFunction())
    return;
 
  const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
  const SIRegisterInfo *TRI = ST.getRegisterInfo();
 
  // The SP is specifically managed and we don't want extra spills of it.
  SavedRegs.reset(MFI->getStackPtrOffsetReg());
 
  const BitVector AllSavedRegs = SavedRegs;
  SavedRegs.clearBitsInMask(TRI->getAllVectorRegMask());
 
  // We have to anticipate introducing CSR VGPR spills or spill of caller
  // save VGPR reserved for SGPR spills as we now always create stack entry
  // for it, if we don't have any stack objects already, since we require a FP
  // if there is a call and stack. We will allocate a VGPR for SGPR spills if
  // there are any SGPR spills. Whether they are CSR spills or otherwise.
  MachineFrameInfo &FrameInfo = MF.getFrameInfo();
  const bool WillHaveFP =
      FrameInfo.hasCalls() && (AllSavedRegs.any() || MFI->hasSpilledSGPRs());
 
  // FP will be specially managed like SP.
  if (WillHaveFP || hasFP(MF))
    SavedRegs.reset(MFI->getFrameOffsetReg());
 
  // Return address use with return instruction is hidden through the SI_RETURN
  // pseudo. Given that and since the IPRA computes actual register usage and
  // does not use CSR list, the clobbering of return address by function calls
  // (D117243) or otherwise (D120922) is ignored/not seen by the IPRA's register
  // usage collection. This will ensure save/restore of return address happens
  // in those scenarios.
  const MachineRegisterInfo &MRI = MF.getRegInfo();
  Register RetAddrReg = TRI->getReturnAddressReg(MF);
  if (!MFI->isEntryFunction() &&
      (FrameInfo.hasCalls() || MRI.isPhysRegModified(RetAddrReg))) {
    SavedRegs.set(TRI->getSubReg(RetAddrReg, AMDGPU::sub0));
    SavedRegs.set(TRI->getSubReg(RetAddrReg, AMDGPU::sub1));
  }
}
 
static void assignSlotsUsingVGPRBlocks(MachineFunction &MF,
                                       const GCNSubtarget &ST,
                                       std::vector<CalleeSavedInfo> &CSI) {
  SIMachineFunctionInfo *FuncInfo = MF.getInfo<SIMachineFunctionInfo>();
  MachineFrameInfo &MFI = MF.getFrameInfo();
  const SIRegisterInfo *TRI = ST.getRegisterInfo();
 
  assert(
      llvm::is_sorted(CSI,
                      [](const CalleeSavedInfo &A, const CalleeSavedInfo &B) {
                        return A.getReg() < B.getReg();
                      }) &&
      "Callee saved registers not sorted");
 
  auto CanUseBlockOps = [&](const CalleeSavedInfo &CSI) {
    return !CSI.isSpilledToReg() &&
           TRI->getPhysRegBaseClass(CSI.getReg()) == &AMDGPU::VGPR_32RegClass &&
           !FuncInfo->isWWMReservedRegister(CSI.getReg());
  };
 
  auto CSEnd = CSI.end();
  for (auto CSIt = CSI.begin(); CSIt != CSEnd; ++CSIt) {
    Register Reg = CSIt->getReg();
    if (!CanUseBlockOps(*CSIt))
      continue;
 
    // Find all the regs that will fit in a 32-bit mask starting at the current
    // reg and build said mask. It should have 1 for every register that's
    // included, with the current register as the least significant bit.
    uint32_t Mask = 1;
    CSEnd = std::remove_if(
        CSIt + 1, CSEnd, [&](const CalleeSavedInfo &CSI) -> bool {
          if (CanUseBlockOps(CSI) && CSI.getReg() < Reg + 32) {
            Mask |= 1 << (CSI.getReg() - Reg);
            return true;
          } else {
            return false;
          }
        });
 
    const TargetRegisterClass *BlockRegClass = TRI->getRegClassForBlockOp(MF);
    Register RegBlock =
        TRI->getMatchingSuperReg(Reg, AMDGPU::sub0, BlockRegClass);
    if (!RegBlock) {
      // We couldn't find a super register for the block. This can happen if
      // the register we started with is too high (e.g. v232 if the maximum is
      // v255). We therefore try to get the last register block and figure out
      // the mask from there.
      Register LastBlockStart =
          AMDGPU::VGPR0 + alignDown(Reg - AMDGPU::VGPR0, 32);
      RegBlock =
          TRI->getMatchingSuperReg(LastBlockStart, AMDGPU::sub0, BlockRegClass);
      assert(RegBlock && TRI->isSubRegister(RegBlock, Reg) &&
             "Couldn't find super register");
      int RegDelta = Reg - LastBlockStart;
      assert(RegDelta > 0 && llvm::countl_zero(Mask) >= RegDelta &&
             "Bad shift amount");
      Mask <<= RegDelta;
    }
 
    FuncInfo->setMaskForVGPRBlockOps(RegBlock, Mask);
 
    // The stack objects can be a bit smaller than the register block if we know
    // some of the high bits of Mask are 0. This may happen often with calling
    // conventions where the caller and callee-saved VGPRs are interleaved at
    // a small boundary (e.g. 8 or 16).
    int UnusedBits = llvm::countl_zero(Mask);
    unsigned BlockSize = TRI->getSpillSize(*BlockRegClass) - UnusedBits * 4;
    int FrameIdx =
        MFI.CreateStackObject(BlockSize, TRI->getSpillAlign(*BlockRegClass),
                              /*isSpillSlot=*/true);
    MFI.setIsCalleeSavedObjectIndex(FrameIdx, true);
 
    CSIt->setFrameIdx(FrameIdx);
    CSIt->setReg(RegBlock);
  }
  CSI.erase(CSEnd, CSI.end());
}
 
bool SIFrameLowering::assignCalleeSavedSpillSlots(
    MachineFunction &MF, const TargetRegisterInfo *TRI,
    std::vector<CalleeSavedInfo> &CSI) const {
  if (CSI.empty())
    return true; // Early exit if no callee saved registers are modified!
 
  const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
  bool UseVGPRBlocks = ST.useVGPRBlockOpsForCSR();
 
  if (UseVGPRBlocks)
    assignSlotsUsingVGPRBlocks(MF, ST, CSI);
 
  return assignCalleeSavedSpillSlotsImpl(MF, TRI, CSI) || UseVGPRBlocks;
}
 
bool SIFrameLowering::assignCalleeSavedSpillSlotsImpl(
    MachineFunction &MF, const TargetRegisterInfo *TRI,
    std::vector<CalleeSavedInfo> &CSI) const {
  if (CSI.empty())
    return true; // Early exit if no callee saved registers are modified!
 
  const SIMachineFunctionInfo *FuncInfo = MF.getInfo<SIMachineFunctionInfo>();
  const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
  const SIRegisterInfo *RI = ST.getRegisterInfo();
  Register FramePtrReg = FuncInfo->getFrameOffsetReg();
  Register BasePtrReg = RI->getBaseRegister();
  Register SGPRForFPSaveRestoreCopy =
      FuncInfo->getScratchSGPRCopyDstReg(FramePtrReg);
  Register SGPRForBPSaveRestoreCopy =
      FuncInfo->getScratchSGPRCopyDstReg(BasePtrReg);
  if (!SGPRForFPSaveRestoreCopy && !SGPRForBPSaveRestoreCopy)
    return false;
 
  unsigned NumModifiedRegs = 0;
 
  if (SGPRForFPSaveRestoreCopy)
    NumModifiedRegs++;
  if (SGPRForBPSaveRestoreCopy)
    NumModifiedRegs++;
 
  for (auto &CS : CSI) {
    if (CS.getReg() == FramePtrReg.asMCReg() && SGPRForFPSaveRestoreCopy) {
      CS.setDstReg(SGPRForFPSaveRestoreCopy);
      if (--NumModifiedRegs)
        break;
    } else if (CS.getReg() == BasePtrReg.asMCReg() &&
               SGPRForBPSaveRestoreCopy) {
      CS.setDstReg(SGPRForBPSaveRestoreCopy);
      if (--NumModifiedRegs)
        break;
    }
  }
 
  return false;
}
 
bool SIFrameLowering::allocateScavengingFrameIndexesNearIncomingSP(
  const MachineFunction &MF) const {
 
  const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
  const MachineFrameInfo &MFI = MF.getFrameInfo();
  const SIInstrInfo *TII = ST.getInstrInfo();
  uint64_t EstStackSize = MFI.estimateStackSize(MF);
  uint64_t MaxOffset = EstStackSize - 1;
 
  // We need the emergency stack slots to be allocated in range of the
  // MUBUF/flat scratch immediate offset from the base register, so assign these
  // first at the incoming SP position.
  //
  // TODO: We could try sorting the objects to find a hole in the first bytes
  // rather than allocating as close to possible. This could save a lot of space
  // on frames with alignment requirements.
  if (ST.hasFlatScratchEnabled()) {
    if (TII->isLegalFLATOffset(MaxOffset, AMDGPUAS::PRIVATE_ADDRESS,
                               AMDGPU::FlatAddrSpace::FlatScratch))
      return false;
  } else {
    if (TII->isLegalMUBUFImmOffset(MaxOffset))
      return false;
  }
 
  return true;
}
 
/// Return the set of all root registers of regunits live-in to @p MBB.
///
/// Intended to avoid using the expensive @c MCRegAliasIterator when deciding
/// if a register to be spilled is already live-in (see @c isAnyRootLiveIn).
static SparseBitVector<> buildLiveInRoots(const MachineBasicBlock &MBB,
                                          const SIRegisterInfo &TRI) {
  SparseBitVector<> LiveInRoots;
  for (const auto &LI : MBB.liveins()) {
    for (MCRegUnitMaskIterator MI(LI.PhysReg, &TRI); MI.isValid(); ++MI) {
      auto [Unit, UnitLaneMask] = *MI;
      if ((LI.LaneMask & UnitLaneMask).none())
        continue;
      for (MCRegUnitRootIterator RI(Unit, &TRI); RI.isValid(); ++RI)
        LiveInRoots.set(*RI);
    }
  }
  return LiveInRoots;
}
 
/// Returns true iff any root of @p Reg is in @p LiveInRoots
/// (see @c buildLiveInRoots).
static bool isAnyRootLiveIn(const SparseBitVector<> &LiveInRoots,
                            const SIRegisterInfo &TRI, MCRegister Reg) {
  for (MCRegUnitIterator UI(Reg, &TRI); UI.isValid(); ++UI) {
    for (MCRegUnitRootIterator RI(*UI, &TRI); RI.isValid(); ++RI) {
      if (LiveInRoots.test(*RI))
        return true;
    }
  }
  return false;
}
 
void SIFrameLowering::spillCalleeSavedRegisterWithoutBlockOps(
    MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
    const CalleeSavedInfo &CS, const SIInstrInfo *TII,
    const SIRegisterInfo &TRI,
    const std::optional<SparseBitVector<>> &LiveInRoots) const {
  MCRegister Reg = CS.getReg();
 
  // We assume a sortUniqueLiveIns later
  MBB.addLiveIn(Reg);
 
  if (CS.isSpilledToReg()) {
    BuildMI(MBB, MI, DebugLoc(), TII->get(TargetOpcode::COPY), CS.getDstReg())
        .addReg(Reg, getKillRegState(true));
  } else {
    const TargetRegisterClass *RC = TRI.getMinimalPhysRegClass(Reg);
    bool IsKill = true;
    // If this value was already livein, we probably have a direct use of
    // the incoming register value, so don't kill at the spill point. This
    // happens since we pass some special inputs (workgroup IDs) in the
    // callee saved range.
    if (LiveInRoots)
      IsKill = !isAnyRootLiveIn(*LiveInRoots, TRI, Reg);
    TII->storeRegToStackSlotCFI(MBB, MI, Reg, IsKill, CS.getFrameIdx(), RC);
  }
}
 
bool SIFrameLowering::spillCalleeSavedRegisters(
    MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
    ArrayRef<CalleeSavedInfo> CSI, const TargetRegisterInfo *OrigTRI) const {
  auto &TRI = *static_cast<const SIRegisterInfo *>(OrigTRI);
  MachineFunction *MF = MBB.getParent();
  const GCNSubtarget &ST = MF->getSubtarget<GCNSubtarget>();
  const SIInstrInfo *TII = ST.getInstrInfo();
 
  std::optional<SparseBitVector<>> LiveInRoots;
  if (MBB.getParent()->getRegInfo().tracksLiveness())
    LiveInRoots = buildLiveInRoots(MBB, TRI);
 
  if (!ST.useVGPRBlockOpsForCSR()) {
    for (const CalleeSavedInfo &CS : CSI)
      spillCalleeSavedRegisterWithoutBlockOps(MBB, MI, CS, TII, TRI,
                                              LiveInRoots);
    if (LiveInRoots)
      MBB.sortUniqueLiveIns();
    return true;
  }
 
  MachineFrameInfo &FrameInfo = MF->getFrameInfo();
  SIMachineFunctionInfo *FuncInfo = MF->getInfo<SIMachineFunctionInfo>();
 
  const TargetRegisterClass *BlockRegClass = TRI.getRegClassForBlockOp(*MF);
  for (const CalleeSavedInfo &CS : CSI) {
    Register Reg = CS.getReg();
    if (!BlockRegClass->contains(Reg) ||
        !FuncInfo->hasMaskForVGPRBlockOps(Reg)) {
      spillCalleeSavedRegisterWithoutBlockOps(MBB, MI, CS, TII, TRI,
                                              LiveInRoots);
      continue;
    }
 
    // Build a scratch block store.
    uint32_t Mask = FuncInfo->getMaskForVGPRBlockOps(Reg);
    int FrameIndex = CS.getFrameIdx();
    MachinePointerInfo PtrInfo =
        MachinePointerInfo::getFixedStack(*MF, FrameIndex);
    MachineMemOperand *MMO =
        MF->getMachineMemOperand(PtrInfo, MachineMemOperand::MOStore,
                                 FrameInfo.getObjectSize(FrameIndex),
                                 FrameInfo.getObjectAlign(FrameIndex));
 
    BuildMI(MBB, MI, MI->getDebugLoc(),
            TII->get(AMDGPU::SI_BLOCK_SPILL_V1024_CFI_SAVE))
        .addReg(Reg, getKillRegState(false))
        .addFrameIndex(FrameIndex)
        .addReg(FuncInfo->getStackPtrOffsetReg())
        .addImm(0)
        .addImm(Mask)
        .addMemOperand(MMO);
 
    FuncInfo->setHasSpilledVGPRs();
 
    // Add the register to the liveins. This is necessary because if any of the
    // VGPRs in the register block is reserved (e.g. if it's a WWM register),
    // then the whole block will be marked as reserved and `updateLiveness` will
    // skip it.
    if (LiveInRoots)
      MBB.addLiveIn(Reg);
  }
  if (LiveInRoots)
    MBB.sortUniqueLiveIns();
 
  return true;
}
 
bool SIFrameLowering::restoreCalleeSavedRegisters(
    MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
    MutableArrayRef<CalleeSavedInfo> CSI,
    const TargetRegisterInfo *OrigTRI) const {
  auto &TRI = *static_cast<const SIRegisterInfo *>(OrigTRI);
  MachineFunction *MF = MBB.getParent();
  const GCNSubtarget &ST = MF->getSubtarget<GCNSubtarget>();
  if (!ST.useVGPRBlockOpsForCSR())
    return false;
 
  SIMachineFunctionInfo *FuncInfo = MF->getInfo<SIMachineFunctionInfo>();
  MachineFrameInfo &MFI = MF->getFrameInfo();
  const SIInstrInfo *TII = ST.getInstrInfo();
  const TargetRegisterClass *BlockRegClass = TRI.getRegClassForBlockOp(*MF);
  for (const CalleeSavedInfo &CS : reverse(CSI)) {
    Register Reg = CS.getReg();
    if (!BlockRegClass->contains(Reg) ||
        !FuncInfo->hasMaskForVGPRBlockOps(Reg)) {
      restoreCalleeSavedRegister(MBB, MI, CS, TII, &TRI);
      continue;
    }
 
    // Build a scratch block load.
    uint32_t Mask = FuncInfo->getMaskForVGPRBlockOps(Reg);
    int FrameIndex = CS.getFrameIdx();
    MachinePointerInfo PtrInfo =
        MachinePointerInfo::getFixedStack(*MF, FrameIndex);
    MachineMemOperand *MMO = MF->getMachineMemOperand(
        PtrInfo, MachineMemOperand::MOLoad, MFI.getObjectSize(FrameIndex),
        MFI.getObjectAlign(FrameIndex));
 
    auto MIB = BuildMI(MBB, MI, MI->getDebugLoc(),
                       TII->get(AMDGPU::SI_BLOCK_SPILL_V1024_RESTORE), Reg)
                   .addFrameIndex(FrameIndex)
                   .addReg(FuncInfo->getStackPtrOffsetReg())
                   .addImm(0)
                   .addImm(Mask)
                   .addMemOperand(MMO);
    TRI.addImplicitUsesForBlockCSRLoad(MIB, Reg);
 
    // Add the register to the liveins. This is necessary because if any of the
    // VGPRs in the register block is reserved (e.g. if it's a WWM register),
    // then the whole block will be marked as reserved and `updateLiveness` will
    // skip it.
    MBB.addLiveIn(Reg);
  }
 
  MBB.sortUniqueLiveIns();
  return true;
}
 
MachineBasicBlock::iterator SIFrameLowering::eliminateCallFramePseudoInstr(
  MachineFunction &MF,
  MachineBasicBlock &MBB,
  MachineBasicBlock::iterator I) const {
  int64_t Amount = I->getOperand(0).getImm();
  if (Amount == 0)
    return MBB.erase(I);
 
  const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
  const SIInstrInfo *TII = ST.getInstrInfo();
  const DebugLoc &DL = I->getDebugLoc();
  unsigned Opc = I->getOpcode();
  bool IsDestroy = Opc == TII->getCallFrameDestroyOpcode();
  uint64_t CalleePopAmount = IsDestroy ? I->getOperand(1).getImm() : 0;
 
  if (!hasReservedCallFrame(MF)) {
    Amount = alignTo(Amount, getStackAlign());
    assert(isUInt<32>(Amount) && "exceeded stack address space size");
    const SIMachineFunctionInfo *MFI = MF.getInfo<SIMachineFunctionInfo>();
    Register SPReg = MFI->getStackPtrOffsetReg();
 
    Amount *= getScratchScaleFactor(ST);
    if (IsDestroy)
      Amount = -Amount;
    auto Add = BuildMI(MBB, I, DL, TII->get(AMDGPU::S_ADD_I32), SPReg)
        .addReg(SPReg)
        .addImm(Amount);
    Add->getOperand(3).setIsDead(); // Mark SCC as dead.
  } else if (CalleePopAmount != 0) {
    llvm_unreachable("is this used?");
  }
 
  return MBB.erase(I);
}
 
/// Returns true if the frame will require a reference to the stack pointer.
///
/// This is the set of conditions common to setting up the stack pointer in a
/// kernel, and for using a frame pointer in a callable function.
///
/// FIXME: Should also check hasOpaqueSPAdjustment and if any inline asm
/// references SP.
static bool frameTriviallyRequiresSP(const MachineFrameInfo &MFI) {
  return MFI.hasVarSizedObjects() || MFI.hasStackMap() || MFI.hasPatchPoint();
}
 
// The FP for kernels is always known 0, so we never really need to setup an
// explicit register for it. However, DisableFramePointerElim will force us to
// use a register for it.
bool SIFrameLowering::hasFPImpl(const MachineFunction &MF) const {
  const MachineFrameInfo &MFI = MF.getFrameInfo();
 
  // For entry functions we can use an immediate offset in most cases,
  // so the presence of calls doesn't imply we need a distinct frame pointer.
  if (MFI.hasCalls() &&
      !MF.getInfo<SIMachineFunctionInfo>()->isEntryFunction()) {
    // All offsets are unsigned, so need to be addressed in the same direction
    // as stack growth.
 
    // FIXME: This function is pretty broken, since it can be called before the
    // frame layout is determined or CSR spills are inserted.
    return MFI.getStackSize() != 0;
  }
 
  return frameTriviallyRequiresSP(MFI) || MFI.isFrameAddressTaken() ||
         MF.getSubtarget<GCNSubtarget>().getRegisterInfo()->hasStackRealignment(
             MF) ||
         mayReserveScratchForCWSR(MF) ||
         MF.getTarget().Options.DisableFramePointerElim(MF);
}
 
bool SIFrameLowering::mayReserveScratchForCWSR(
    const MachineFunction &MF) const {
  return MF.getInfo<SIMachineFunctionInfo>()->isDynamicVGPREnabled() &&
         AMDGPU::isEntryFunctionCC(MF.getFunction().getCallingConv()) &&
         AMDGPU::isCompute(MF.getFunction().getCallingConv());
}
 
// This is essentially a reduced version of hasFP for entry functions. Since the
// stack pointer is known 0 on entry to kernels, we never really need an FP
// register. We may need to initialize the stack pointer depending on the frame
// properties, which logically overlaps many of the cases where an ordinary
// function would require an FP.
bool SIFrameLowering::requiresStackPointerReference(
    const MachineFunction &MF) const {
  // Callable functions always require a stack pointer reference.
  assert(MF.getInfo<SIMachineFunctionInfo>()->isEntryFunction() &&
         "only expected to call this for entry points functions");
 
  const MachineFrameInfo &MFI = MF.getFrameInfo();
 
  // Entry points ordinarily don't need to initialize SP. We have to set it up
  // for callees if there are any. Also note tail calls are only possible via
  // the `llvm.amdgcn.cs.chain` intrinsic.
  if (MFI.hasCalls() || MFI.hasTailCall())
    return true;
 
  // We still need to initialize the SP if we're doing anything weird that
  // references the SP, like variable sized stack objects.
  return frameTriviallyRequiresSP(MFI);
}
 
MachineInstr *SIFrameLowering::buildCFI(MachineBasicBlock &MBB,
                                        MachineBasicBlock::iterator MBBI,
                                        const DebugLoc &DL,
                                        const MCCFIInstruction &CFIInst,
                                        MachineInstr::MIFlag Flag) const {
  MachineFunction &MF = *MBB.getParent();
  const SIInstrInfo *TII = MF.getSubtarget<GCNSubtarget>().getInstrInfo();
  return BuildMI(MBB, MBBI, DL, TII->get(TargetOpcode::CFI_INSTRUCTION))
      .addCFIIndex(MF.addFrameInst(CFIInst))
      .setMIFlag(Flag);
}
 
MachineInstr *SIFrameLowering::buildCFIForVRegToVRegSpill(
    MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI,
    const DebugLoc &DL, const MCRegister Reg, const MCRegister RegCopy) const {
  MachineFunction &MF = *MBB.getParent();
  const MCRegisterInfo &MCRI = *MF.getContext().getRegisterInfo();
  const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
 
  MCRegister MaskReg = MCRI.getDwarfRegNum(
      ST.isWave32() ? AMDGPU::EXEC_LO : AMDGPU::EXEC, false);
  auto CFIInst = MCCFIInstruction::createLLVMVectorRegisterMask(
      nullptr, MCRI.getDwarfRegNum(Reg, false),
      MCRI.getDwarfRegNum(RegCopy, false), VGPRLaneBitSize, MaskReg,
      ST.getWavefrontSize());
  return buildCFI(MBB, MBBI, DL, std::move(CFIInst));
}
 
MachineInstr *SIFrameLowering::buildCFIForSGPRToVGPRSpill(
    MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI,
    const DebugLoc &DL, const MCRegister SGPR, const MCRegister VGPR,
    const int Lane) const {
  const MachineFunction &MF = *MBB.getParent();
  const MCRegisterInfo &MCRI = *MF.getContext().getRegisterInfo();
 
  int DwarfSGPR = MCRI.getDwarfRegNum(SGPR, false);
  int DwarfVGPR = MCRI.getDwarfRegNum(VGPR, false);
  assert(DwarfSGPR != -1 && DwarfVGPR != -1);
  assert(Lane != -1 && "Expected a lane to be present");
 
  // Build a CFI instruction that represents a SGPR spilled to a single lane of
  // a VGPR.
  MCCFIInstruction::VectorRegisterWithLane VR{unsigned(DwarfVGPR),
                                              unsigned(Lane), VGPRLaneBitSize};
  auto CFIInst =
      MCCFIInstruction::createLLVMVectorRegisters(nullptr, DwarfSGPR, {VR});
  return buildCFI(MBB, MBBI, DL, std::move(CFIInst));
}
 
MachineInstr *SIFrameLowering::buildCFIForSGPRToVGPRSpill(
    MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI,
    const DebugLoc &DL, MCRegister SGPR,
    ArrayRef<SIRegisterInfo::SpilledReg> VGPRSpills) const {
  if (VGPRSpills.size() == 1u)
    return buildCFIForSGPRToVGPRSpill(MBB, MBBI, DL, SGPR, VGPRSpills[0].VGPR,
                                      VGPRSpills[0].Lane);
  const MachineFunction &MF = *MBB.getParent();
  const MCRegisterInfo &MCRI = *MF.getContext().getRegisterInfo();
 
  int DwarfSGPR = MCRI.getDwarfRegNum(SGPR, false);
  assert(DwarfSGPR != -1);
 
  // Build a CFI instruction that represents a SGPR spilled to multiple lanes of
  // multiple VGPRs.
 
  SmallVector<MCCFIInstruction::VectorRegisterWithLane> VGPRs;
  for (SIRegisterInfo::SpilledReg Spill : VGPRSpills) {
    int DwarfVGPR = MCRI.getDwarfRegNum(Spill.VGPR, false);
    assert(DwarfVGPR != -1);
    assert(Spill.hasLane() && "Expected a lane to be present");
    VGPRs.push_back(
        {unsigned(DwarfVGPR), unsigned(Spill.Lane), VGPRLaneBitSize});
  }
 
  auto CFIInst = MCCFIInstruction::createLLVMVectorRegisters(nullptr, DwarfSGPR,
                                                             std::move(VGPRs));
  return buildCFI(MBB, MBBI, DL, std::move(CFIInst));
}
 
MachineInstr *SIFrameLowering::buildCFIForSGPRToVMEMSpill(
    MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI,
    const DebugLoc &DL, MCRegister SGPR, int64_t Offset) const {
  MachineFunction &MF = *MBB.getParent();
  const MCRegisterInfo &MCRI = *MF.getContext().getRegisterInfo();
  return buildCFI(MBB, MBBI, DL,
                  llvm::MCCFIInstruction::createOffset(
                      nullptr, MCRI.getDwarfRegNum(SGPR, false), Offset));
}
 
MachineInstr *SIFrameLowering::buildCFIForVGPRToVMEMSpill(
    MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI,
    const DebugLoc &DL, MCRegister VGPR, int64_t Offset) const {
  const MachineFunction &MF = *MBB.getParent();
  const MCRegisterInfo &MCRI = *MF.getContext().getRegisterInfo();
  const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
 
  int DwarfVGPR = MCRI.getDwarfRegNum(VGPR, false);
  assert(DwarfVGPR != -1);
 
  MCRegister MaskReg = MCRI.getDwarfRegNum(
      ST.isWave32() ? AMDGPU::EXEC_LO : AMDGPU::EXEC, false);
  auto CFIInst = MCCFIInstruction::createLLVMVectorOffset(
      nullptr, DwarfVGPR, VGPRLaneBitSize, MaskReg, ST.getWavefrontSize(),
      Offset);
  return buildCFI(MBB, MBBI, DL, std::move(CFIInst));
}
 
MachineInstr *SIFrameLowering::buildCFIForRegToSGPRPairSpill(
    MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI,
    const DebugLoc &DL, const MCRegister Reg, const MCRegister SGPRPair) const {
  const MachineFunction &MF = *MBB.getParent();
  const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
  const SIRegisterInfo &TRI = *ST.getRegisterInfo();
 
  MCRegister SGPR0 = TRI.getSubReg(SGPRPair, AMDGPU::sub0);
  MCRegister SGPR1 = TRI.getSubReg(SGPRPair, AMDGPU::sub1);
 
  int DwarfReg = TRI.getDwarfRegNum(Reg, false);
  int DwarfSGPR0 = TRI.getDwarfRegNum(SGPR0, false);
  int DwarfSGPR1 = TRI.getDwarfRegNum(SGPR1, false);
  assert(DwarfReg != -1 && DwarfSGPR0 != -1 && DwarfSGPR1 != -1);
 
  auto CFIInst = MCCFIInstruction::createLLVMRegisterPair(
      nullptr, DwarfReg, DwarfSGPR0, SGPRBitSize, DwarfSGPR1, SGPRBitSize);
  return buildCFI(MBB, MBBI, DL, std::move(CFIInst));
}
 
MachineInstr *SIFrameLowering::buildCFIForSameValue(
    MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI,
    const DebugLoc &DL, MCRegister Reg) const {
  const MachineFunction &MF = *MBB.getParent();
  const MCRegisterInfo &MCRI = *MF.getContext().getRegisterInfo();
  int DwarfReg = MCRI.getDwarfRegNum(Reg, /*isEH=*/false);
  auto CFIInst = MCCFIInstruction::createSameValue(nullptr, DwarfReg);
  return buildCFI(MBB, MBBI, DL, std::move(CFIInst));
}