//===-- GCNSubtarget.cpp - GCN Subtarget Information ----------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
/// \file
/// Implements the GCN specific subclass of TargetSubtarget.
//
//===----------------------------------------------------------------------===//

#include "GCNSubtarget.h"
#include "AMDGPUCallLowering.h"
#include "AMDGPUInstructionSelector.h"
#include "AMDGPULegalizerInfo.h"
#include "AMDGPURegisterBankInfo.h"
#include "AMDGPUSelectionDAGInfo.h"
#include "AMDGPUTargetMachine.h"
#include "SIMachineFunctionInfo.h"
#include "Utils/AMDGPUBaseInfo.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/CodeGen/GlobalISel/InlineAsmLowering.h"
#include "llvm/CodeGen/MachineScheduler.h"
#include "llvm/CodeGen/TargetFrameLowering.h"
#include "llvm/IR/DiagnosticInfo.h"
#include "llvm/IR/MDBuilder.h"
#include "llvm/TargetParser/AMDGPUTargetParser.h"
#include <algorithm>

using namespace llvm;

#define DEBUG_TYPE "gcn-subtarget"

#define GET_SUBTARGETINFO_TARGET_DESC
#define GET_SUBTARGETINFO_CTOR
#define AMDGPUSubtarget GCNSubtarget
#include "AMDGPUGenSubtargetInfo.inc"
#undef AMDGPUSubtarget

static cl::opt<bool> EnableVGPRIndexMode(
    "amdgpu-vgpr-index-mode",
    cl::desc("Use GPR indexing mode instead of movrel for vector indexing"),
    cl::init(false));

static cl::opt<bool> UseAA("amdgpu-use-aa-in-codegen",
                           cl::desc("Enable the use of AA during codegen."),
                           cl::init(true));

static cl::opt<unsigned>
    NSAThreshold("amdgpu-nsa-threshold",
                 cl::desc("Number of addresses from which to enable MIMG NSA."),
                 cl::init(2), cl::Hidden);

GCNSubtarget::~GCNSubtarget() = default;

static AMDGPUSubtarget::Generation computeDefaultGeneration(const Triple &TT) {
  // Legacy triples without a subarch default to the first target that supports
  // flat addressing for HSA, otherwise the first amdgcn target.
  if (TT.getSubArch() == Triple::NoSubArch)
    return TT.getOS() == Triple::AMDHSA ? AMDGPUSubtarget::SEA_ISLANDS
                                        : AMDGPUSubtarget::SOUTHERN_ISLANDS;

  switch (AMDGPU::getMajorSubArch(TT.getSubArch())) {
  case Triple::AMDGPUSubArch6:
    return AMDGPUSubtarget::SOUTHERN_ISLANDS;
  case Triple::AMDGPUSubArch7:
    return AMDGPUSubtarget::SEA_ISLANDS;
  case Triple::AMDGPUSubArch8:
  case Triple::AMDGPUSubArch810:
    return AMDGPUSubtarget::VOLCANIC_ISLANDS;
  case Triple::AMDGPUSubArch9:
  case Triple::AMDGPUSubArch908:
  case Triple::AMDGPUSubArch90A:
  case Triple::AMDGPUSubArch9_4:
    return AMDGPUSubtarget::GFX9;
  case Triple::AMDGPUSubArch10_1:
  case Triple::AMDGPUSubArch10_3:
    return AMDGPUSubtarget::GFX10;
  case Triple::AMDGPUSubArch11:
  case Triple::AMDGPUSubArch11_7:
    return AMDGPUSubtarget::GFX11;
  case Triple::AMDGPUSubArch12:
  case Triple::AMDGPUSubArch12_5:
    return AMDGPUSubtarget::GFX12;
  case Triple::AMDGPUSubArch13:
    return AMDGPUSubtarget::GFX13;
  default:
    reportFatalUsageError("invalid subarch for amdgpu");
  }
}

GCNSubtarget &GCNSubtarget::initializeSubtargetDependencies(const Triple &TT,
                                                            StringRef GPU,
                                                            StringRef FS) {
  // Determine default and user-specified characteristics
  //
  // We want to be able to turn these off, but making this a subtarget feature
  // for SI has the unhelpful behavior that it unsets everything else if you
  // disable it.
  //
  // Similarly we want enable-prt-strict-null to be on by default and not to
  // unset everything else if it is disabled

  SmallString<256> FullFS("+load-store-opt,+enable-ds128,");

  // Turn on features that HSA ABI requires. Also turn on FlatForGlobal by
  // default
  if (isAmdHsaOS())
    FullFS += "+flat-for-global,+unaligned-access-mode,+trap-handler,";

  FullFS += "+enable-prt-strict-null,"; // This is overridden by a disable in FS

  // Disable mutually exclusive bits.
  if (FS.contains_insensitive("+wavefrontsize")) {
    if (!FS.contains_insensitive("wavefrontsize16"))
      FullFS += "-wavefrontsize16,";
    if (!FS.contains_insensitive("wavefrontsize32"))
      FullFS += "-wavefrontsize32,";
    if (!FS.contains_insensitive("wavefrontsize64"))
      FullFS += "-wavefrontsize64,";
  }

  FullFS += FS;

  ParseSubtargetFeatures(GPU, /*TuneCPU*/ GPU, FullFS);

  // Implement the "generic" processors, which acts as the default when no
  // generation features are enabled (e.g for -mcpu=''). HSA OS defaults to
  // the first amdgcn target that supports flat addressing. Other OSes defaults
  // to the first amdgcn target.
  if (Gen == AMDGPUSubtarget::INVALID) {
    Gen = computeDefaultGeneration(TT);
    // Assume wave64 for the unknown target, if not explicitly set.
    if (getWavefrontSizeLog2() == 0)
      WavefrontSizeLog2 = 6;
  } else if (!hasFeature(AMDGPU::FeatureWavefrontSize32) &&
             !hasFeature(AMDGPU::FeatureWavefrontSize64)) {
    // If there is no default wave size it must be a generation before gfx10,
    // these have FeatureWavefrontSize64 in their definition already. For gfx10+
    // set wave32 as a default.
    ToggleFeature(AMDGPU::FeatureWavefrontSize32);
    WavefrontSizeLog2 = getGeneration() >= AMDGPUSubtarget::GFX10 ? 5 : 6;
  }

  // We don't support FP64 for EG/NI atm.
  assert(!hasFP64() || (getGeneration() >= AMDGPUSubtarget::SOUTHERN_ISLANDS));

  // Targets must either support 64-bit offsets for MUBUF instructions, and/or
  // support flat operations, otherwise they cannot access a 64-bit global
  // address space
  assert(hasAddr64() || hasFlat());
  // Unless +-flat-for-global is specified, turn on FlatForGlobal for targets
  // that do not support ADDR64 variants of MUBUF instructions. Such targets
  // cannot use a 64 bit offset with a MUBUF instruction to access the global
  // address space
  if (!hasAddr64() && !FS.contains("flat-for-global") && !UseFlatForGlobal) {
    ToggleFeature(AMDGPU::FeatureUseFlatForGlobal);
    UseFlatForGlobal = true;
  }
  // Unless +-flat-for-global is specified, use MUBUF instructions for global
  // address space access if flat operations are not available.
  if (!hasFlat() && !FS.contains("flat-for-global") && UseFlatForGlobal) {
    ToggleFeature(AMDGPU::FeatureUseFlatForGlobal);
    UseFlatForGlobal = false;
  }

  // Set defaults if needed.
  if (MaxPrivateElementSize == 0)
    MaxPrivateElementSize = 4;

  if (LDSBankCount == 0)
    LDSBankCount = 32;

  if (AddressableLocalMemorySize == 0)
    AddressableLocalMemorySize = 32768;

  if (FlatOffsetBitWidth == 0)
    FlatOffsetBitWidth = 13;

  LocalMemorySize = AMDGPU::IsaInfo::getLocalMemorySize(*this);
  // LDS Allocation Granularity calculated in bytes from dwords
  LDSAllocationGranularity =
      AMDGPU::getLdsDwGranularity(*this) * sizeof(uint32_t);

  HasFminFmaxLegacy = getGeneration() < AMDGPUSubtarget::VOLCANIC_ISLANDS;
  HasSMulHi = getGeneration() >= AMDGPUSubtarget::GFX9;

  // InstCacheLineSize is set from TableGen subtarget features
  // (FeatureInstCacheLineSize64 / FeatureInstCacheLineSize128).
  // Fall back to 64 if no feature was specified (e.g. generic targets).
  if (InstCacheLineSize == 0)
    InstCacheLineSize = 64;

  assert(llvm::isPowerOf2_32(InstCacheLineSize) &&
         "InstCacheLineSize must be a power of 2");

  return *this;
}

void GCNSubtarget::checkSubtargetFeatures(const Function &F) const {
  LLVMContext &Ctx = F.getContext();
  if (hasFeature(AMDGPU::FeatureWavefrontSize32) &&
      hasFeature(AMDGPU::FeatureWavefrontSize64)) {
    Ctx.diagnose(DiagnosticInfoUnsupported(
        F, "must specify exactly one of wavefrontsize32 and wavefrontsize64"));
  }
}

// TODO: Validate subarch for subtarget

GCNSubtarget::GCNSubtarget(const Triple &TT, StringRef GPU, StringRef FS,
                           const GCNTargetMachine &TM, bool BufferOOBRelaxed,
                           bool TBufferOOBRelaxed,
                           AMDGPU::TargetIDSetting XnackSetting,
                           AMDGPU::TargetIDSetting SramEccSetting)
    : // clang-format off
    AMDGPUGenSubtargetInfo(TT, GPU, /*TuneCPU*/ GPU, FS),
    AMDGPUSubtarget(TT),
    TargetID(AMDGPU::createAMDGPUTargetID(*this, "")),
    InstrItins(getInstrItineraryForCPU(GPU)),
    BufferOOBRelaxed(BufferOOBRelaxed),
    TBufferOOBRelaxed(TBufferOOBRelaxed),
    InstrInfo(initializeSubtargetDependencies(TT, GPU, FS)),
    TLInfo(TM, *this),
    // Frame index expansion sometimes assumes the low bit of SP is 0
    FrameLowering(TargetFrameLowering::StackGrowsUp, getStackAlignment(), 0,
                  /*TransAl=*/Align(4)) {

  // clang-format on

  // Apply the module flag's xnack setting if the target supports on/off modes.
  // Targets without on/off mode support have xnack always on and ignore module
  // flags.
  if (hasXNACKOnOffModes())
    TargetID.setXnackSetting(XnackSetting);

  // Apply the module flag's sramecc setting if the target supports it.
  if (supportsSRAMECC())
    TargetID.setSramEccSetting(SramEccSetting);

  LLVM_DEBUG(dbgs() << "xnack setting for subtarget: "
                    << TargetID.getXnackSetting() << '\n');
  LLVM_DEBUG(dbgs() << "sramecc setting for subtarget: "
                    << TargetID.getSramEccSetting() << '\n');

  MaxWavesPerEU = AMDGPU::IsaInfo::getMaxWavesPerEU(*this);
  EUsPerCU = AMDGPU::IsaInfo::getEUsPerCU(*this);

  TSInfo = std::make_unique<AMDGPUSelectionDAGInfo>();

  CallLoweringInfo = std::make_unique<AMDGPUCallLowering>(*getTargetLowering());
  InlineAsmLoweringInfo =
      std::make_unique<InlineAsmLowering>(getTargetLowering());
  Legalizer = std::make_unique<AMDGPULegalizerInfo>(*this, TM);
  RegBankInfo = std::make_unique<AMDGPURegisterBankInfo>(*this);
  InstSelector =
      std::make_unique<AMDGPUInstructionSelector>(*this, *RegBankInfo);
}

const SelectionDAGTargetInfo *GCNSubtarget::getSelectionDAGInfo() const {
  return TSInfo.get();
}

unsigned GCNSubtarget::getConstantBusLimit(unsigned Opcode) const {
  if (getGeneration() < GFX10)
    return 1;

  switch (Opcode) {
  case AMDGPU::V_LSHLREV_B64_e64:
  case AMDGPU::V_LSHLREV_B64_gfx10:
  case AMDGPU::V_LSHLREV_B64_e64_gfx11:
  case AMDGPU::V_LSHLREV_B64_e32_gfx12:
  case AMDGPU::V_LSHLREV_B64_e64_gfx12:
  case AMDGPU::V_LSHL_B64_e64:
  case AMDGPU::V_LSHRREV_B64_e64:
  case AMDGPU::V_LSHRREV_B64_gfx10:
  case AMDGPU::V_LSHRREV_B64_e64_gfx11:
  case AMDGPU::V_LSHRREV_B64_e64_gfx12:
  case AMDGPU::V_LSHR_B64_e64:
  case AMDGPU::V_ASHRREV_I64_e64:
  case AMDGPU::V_ASHRREV_I64_gfx10:
  case AMDGPU::V_ASHRREV_I64_e64_gfx11:
  case AMDGPU::V_ASHRREV_I64_e64_gfx12:
  case AMDGPU::V_ASHR_I64_e64:
    return 1;
  }

  return 2;
}

/// This list was mostly derived from experimentation.
bool GCNSubtarget::zeroesHigh16BitsOfDest(unsigned Opcode) const {
  switch (Opcode) {
  case AMDGPU::V_CVT_F16_F32_e32:
  case AMDGPU::V_CVT_F16_F32_e64:
  case AMDGPU::V_CVT_F16_U16_e32:
  case AMDGPU::V_CVT_F16_U16_e64:
  case AMDGPU::V_CVT_F16_I16_e32:
  case AMDGPU::V_CVT_F16_I16_e64:
  case AMDGPU::V_RCP_F16_e64:
  case AMDGPU::V_RCP_F16_e32:
  case AMDGPU::V_RSQ_F16_e64:
  case AMDGPU::V_RSQ_F16_e32:
  case AMDGPU::V_SQRT_F16_e64:
  case AMDGPU::V_SQRT_F16_e32:
  case AMDGPU::V_LOG_F16_e64:
  case AMDGPU::V_LOG_F16_e32:
  case AMDGPU::V_EXP_F16_e64:
  case AMDGPU::V_EXP_F16_e32:
  case AMDGPU::V_SIN_F16_e64:
  case AMDGPU::V_SIN_F16_e32:
  case AMDGPU::V_COS_F16_e64:
  case AMDGPU::V_COS_F16_e32:
  case AMDGPU::V_FLOOR_F16_e64:
  case AMDGPU::V_FLOOR_F16_e32:
  case AMDGPU::V_CEIL_F16_e64:
  case AMDGPU::V_CEIL_F16_e32:
  case AMDGPU::V_TRUNC_F16_e64:
  case AMDGPU::V_TRUNC_F16_e32:
  case AMDGPU::V_RNDNE_F16_e64:
  case AMDGPU::V_RNDNE_F16_e32:
  case AMDGPU::V_FRACT_F16_e64:
  case AMDGPU::V_FRACT_F16_e32:
  case AMDGPU::V_FREXP_MANT_F16_e64:
  case AMDGPU::V_FREXP_MANT_F16_e32:
  case AMDGPU::V_FREXP_EXP_I16_F16_e64:
  case AMDGPU::V_FREXP_EXP_I16_F16_e32:
  case AMDGPU::V_LDEXP_F16_e64:
  case AMDGPU::V_LDEXP_F16_e32:
  case AMDGPU::V_LSHLREV_B16_e64:
  case AMDGPU::V_LSHLREV_B16_e32:
  case AMDGPU::V_LSHRREV_B16_e64:
  case AMDGPU::V_LSHRREV_B16_e32:
  case AMDGPU::V_ASHRREV_I16_e64:
  case AMDGPU::V_ASHRREV_I16_e32:
  case AMDGPU::V_ADD_U16_e64:
  case AMDGPU::V_ADD_U16_e32:
  case AMDGPU::V_SUB_U16_e64:
  case AMDGPU::V_SUB_U16_e32:
  case AMDGPU::V_SUBREV_U16_e64:
  case AMDGPU::V_SUBREV_U16_e32:
  case AMDGPU::V_MUL_LO_U16_e64:
  case AMDGPU::V_MUL_LO_U16_e32:
  case AMDGPU::V_ADD_F16_e64:
  case AMDGPU::V_ADD_F16_e32:
  case AMDGPU::V_SUB_F16_e64:
  case AMDGPU::V_SUB_F16_e32:
  case AMDGPU::V_SUBREV_F16_e64:
  case AMDGPU::V_SUBREV_F16_e32:
  case AMDGPU::V_MUL_F16_e64:
  case AMDGPU::V_MUL_F16_e32:
  case AMDGPU::V_MAX_F16_e64:
  case AMDGPU::V_MAX_F16_e32:
  case AMDGPU::V_MIN_F16_e64:
  case AMDGPU::V_MIN_F16_e32:
  case AMDGPU::V_MAX_U16_e64:
  case AMDGPU::V_MAX_U16_e32:
  case AMDGPU::V_MIN_U16_e64:
  case AMDGPU::V_MIN_U16_e32:
  case AMDGPU::V_MAX_I16_e64:
  case AMDGPU::V_MAX_I16_e32:
  case AMDGPU::V_MIN_I16_e64:
  case AMDGPU::V_MIN_I16_e32:
  case AMDGPU::V_MAD_F16_e64:
  case AMDGPU::V_MAD_U16_e64:
  case AMDGPU::V_MAD_I16_e64:
  case AMDGPU::V_FMA_F16_e64:
  case AMDGPU::V_DIV_FIXUP_F16_e64:
    // On gfx10, all 16-bit instructions preserve the high bits.
    return getGeneration() <= AMDGPUSubtarget::GFX9;
  case AMDGPU::V_MADAK_F16:
  case AMDGPU::V_MADMK_F16:
  case AMDGPU::V_MAC_F16_e64:
  case AMDGPU::V_MAC_F16_e32:
  case AMDGPU::V_FMAMK_F16:
  case AMDGPU::V_FMAAK_F16:
  case AMDGPU::V_FMAC_F16_e64:
  case AMDGPU::V_FMAC_F16_e32:
    // In gfx9, the preferred handling of the unused high 16-bits changed. Most
    // instructions maintain the legacy behavior of 0ing. Some instructions
    // changed to preserving the high bits.
    return getGeneration() == AMDGPUSubtarget::VOLCANIC_ISLANDS;
  case AMDGPU::V_MAD_MIXLO_F16:
  case AMDGPU::V_MAD_MIXHI_F16:
  default:
    return false;
  }
}

void GCNSubtarget::overrideSchedPolicy(MachineSchedPolicy &Policy,
                                       const SchedRegion &Region) const {
  // Track register pressure so the scheduler can try to decrease
  // pressure once register usage is above the threshold defined by
  // SIRegisterInfo::getRegPressureSetLimit()
  Policy.ShouldTrackPressure = true;

  const Function &F = Region.RegionBegin->getMF()->getFunction();
  if (AMDGPU::getSchedStrategy(F) == "coexec") {
    Policy.OnlyTopDown = true;
    Policy.OnlyBottomUp = false;
    return;
  }

  // Enabling both top down and bottom up scheduling seems to give us less
  // register spills than just using one of these approaches on its own.
  Policy.OnlyTopDown = false;
  Policy.OnlyBottomUp = false;

  // Enabling ShouldTrackLaneMasks crashes the SI Machine Scheduler.
  if (!enableSIScheduler())
    Policy.ShouldTrackLaneMasks = true;
}

void GCNSubtarget::overridePostRASchedPolicy(MachineSchedPolicy &Policy,
                                             const SchedRegion &Region) const {
  const Function &F = Region.RegionBegin->getMF()->getFunction();
  Attribute PostRADirectionAttr = F.getFnAttribute("amdgpu-post-ra-direction");
  if (!PostRADirectionAttr.isValid())
    return;

  StringRef PostRADirectionStr = PostRADirectionAttr.getValueAsString();
  if (PostRADirectionStr == "topdown") {
    Policy.OnlyTopDown = true;
    Policy.OnlyBottomUp = false;
  } else if (PostRADirectionStr == "bottomup") {
    Policy.OnlyTopDown = false;
    Policy.OnlyBottomUp = true;
  } else if (PostRADirectionStr == "bidirectional") {
    Policy.OnlyTopDown = false;
    Policy.OnlyBottomUp = false;
  } else {
    DiagnosticInfoOptimizationFailure Diag(
        F, F.getSubprogram(), "invalid value for postRA direction attribute");
    F.getContext().diagnose(Diag);
  }

  LLVM_DEBUG({
    const char *DirStr = "default";
    if (Policy.OnlyTopDown && !Policy.OnlyBottomUp)
      DirStr = "topdown";
    else if (!Policy.OnlyTopDown && Policy.OnlyBottomUp)
      DirStr = "bottomup";
    else if (!Policy.OnlyTopDown && !Policy.OnlyBottomUp)
      DirStr = "bidirectional";

    dbgs() << "Post-MI-sched direction (" << F.getName() << "): " << DirStr
           << '\n';
  });
}

void GCNSubtarget::mirFileLoaded(MachineFunction &MF) const {
  if (isWave32()) {
    // Fix implicit $vcc operands after MIParser has verified that they match
    // the instruction definitions.
    for (auto &MBB : MF) {
      for (auto &MI : MBB)
        InstrInfo.fixImplicitOperands(MI);
    }
  }
}

bool GCNSubtarget::hasMadF16() const {
  return InstrInfo.pseudoToMCOpcode(AMDGPU::V_MAD_F16_e64) != -1;
}

bool GCNSubtarget::useVGPRIndexMode() const {
  return hasVGPRIndexMode() && (!hasMovrel() || EnableVGPRIndexMode);
}

bool GCNSubtarget::useAA() const { return UseAA; }

unsigned GCNSubtarget::getOccupancyWithNumSGPRs(unsigned SGPRs) const {
  return AMDGPU::IsaInfo::getOccupancyWithNumSGPRs(*this, SGPRs);
}

unsigned
GCNSubtarget::getOccupancyWithNumVGPRs(unsigned NumVGPRs,
                                       unsigned DynamicVGPRBlockSize) const {
  return AMDGPU::IsaInfo::getNumWavesPerEUWithNumVGPRs(*this, NumVGPRs,
                                                       DynamicVGPRBlockSize);
}

unsigned
GCNSubtarget::getBaseReservedNumSGPRs(const bool HasFlatScratch) const {
  if (getGeneration() >= AMDGPUSubtarget::GFX10)
    return 2; // VCC. FLAT_SCRATCH and XNACK are no longer in SGPRs.

  if (HasFlatScratch || HasArchitectedFlatScratch) {
    if (getGeneration() >= AMDGPUSubtarget::VOLCANIC_ISLANDS)
      return 6; // FLAT_SCRATCH, XNACK, VCC (in that order).
    if (getGeneration() == AMDGPUSubtarget::SEA_ISLANDS)
      return 4; // FLAT_SCRATCH, VCC (in that order).
  }

  if (isXNACKEnabled())
    return 4; // XNACK, VCC (in that order).
  return 2;   // VCC.
}

unsigned GCNSubtarget::getReservedNumSGPRs(const MachineFunction &MF) const {
  const SIMachineFunctionInfo &MFI = *MF.getInfo<SIMachineFunctionInfo>();
  return getBaseReservedNumSGPRs(MFI.getUserSGPRInfo().hasFlatScratchInit());
}

unsigned GCNSubtarget::getReservedNumSGPRs(const Function &F) const {
  // In principle we do not need to reserve SGPR pair used for flat_scratch if
  // we know flat instructions do not access the stack anywhere in the
  // program. For now assume it's needed if we have flat instructions.
  const bool KernelUsesFlatScratch = hasFlatAddressSpace();
  return getBaseReservedNumSGPRs(KernelUsesFlatScratch);
}

std::pair<unsigned, unsigned>
GCNSubtarget::computeOccupancy(const Function &F, unsigned LDSSize,
                               unsigned NumSGPRs, unsigned NumVGPRs) const {
  unsigned DynamicVGPRBlockSize = AMDGPU::getDynamicVGPRBlockSize(F);
  // Temporarily check both the attribute and the subtarget feature until the
  // latter is removed.
  if (DynamicVGPRBlockSize == 0 && isDynamicVGPREnabled())
    DynamicVGPRBlockSize = getDynamicVGPRBlockSize();

  auto [MinOcc, MaxOcc] = getOccupancyWithWorkGroupSizes(LDSSize, F);
  unsigned SGPROcc = getOccupancyWithNumSGPRs(NumSGPRs);
  unsigned VGPROcc = getOccupancyWithNumVGPRs(NumVGPRs, DynamicVGPRBlockSize);

  // Maximum occupancy may be further limited by high SGPR/VGPR usage.
  MaxOcc = std::min({MaxOcc, SGPROcc, VGPROcc});
  return {std::min(MinOcc, MaxOcc), MaxOcc};
}

unsigned GCNSubtarget::getBaseMaxNumSGPRs(
    const Function &F, std::pair<unsigned, unsigned> WavesPerEU,
    unsigned PreloadedSGPRs, unsigned ReservedNumSGPRs) const {
  // Compute maximum number of SGPRs function can use using default/requested
  // minimum number of waves per execution unit.
  unsigned MaxNumSGPRs = getMaxNumSGPRs(WavesPerEU.first, false);
  unsigned MaxAddressableNumSGPRs = getMaxNumSGPRs(WavesPerEU.first, true);

  // Check if maximum number of SGPRs was explicitly requested using
  // "amdgpu-num-sgpr" attribute.
  unsigned Requested =
      F.getFnAttributeAsParsedInteger("amdgpu-num-sgpr", MaxNumSGPRs);

  if (Requested != MaxNumSGPRs) {
    // Make sure requested value does not violate subtarget's specifications.
    if (Requested && (Requested <= ReservedNumSGPRs))
      Requested = 0;

    // If more SGPRs are required to support the input user/system SGPRs,
    // increase to accommodate them.
    //
    // FIXME: This really ends up using the requested number of SGPRs + number
    // of reserved special registers in total. Theoretically you could re-use
    // the last input registers for these special registers, but this would
    // require a lot of complexity to deal with the weird aliasing.
    unsigned InputNumSGPRs = PreloadedSGPRs;
    if (Requested && Requested < InputNumSGPRs)
      Requested = InputNumSGPRs;

    // Make sure requested value is compatible with values implied by
    // default/requested minimum/maximum number of waves per execution unit.
    if (Requested && Requested > getMaxNumSGPRs(WavesPerEU.first, false))
      Requested = 0;
    if (WavesPerEU.second && Requested &&
        Requested < getMinNumSGPRs(WavesPerEU.second))
      Requested = 0;

    if (Requested)
      MaxNumSGPRs = Requested;
  }

  if (hasSGPRInitBug())
    MaxNumSGPRs = AMDGPU::IsaInfo::FIXED_NUM_SGPRS_FOR_INIT_BUG;

  return std::min(MaxNumSGPRs - ReservedNumSGPRs, MaxAddressableNumSGPRs);
}

unsigned GCNSubtarget::getMaxNumSGPRs(const MachineFunction &MF) const {
  const Function &F = MF.getFunction();
  const SIMachineFunctionInfo &MFI = *MF.getInfo<SIMachineFunctionInfo>();
  return getBaseMaxNumSGPRs(F, MFI.getWavesPerEU(), MFI.getNumPreloadedSGPRs(),
                            getReservedNumSGPRs(MF));
}

unsigned GCNSubtarget::getMaxNumPreloadedSGPRs() const {
  using USI = GCNUserSGPRUsageInfo;
  // Max number of user SGPRs
  const unsigned MaxUserSGPRs =
      USI::getNumUserSGPRForField(USI::PrivateSegmentBufferID) +
      USI::getNumUserSGPRForField(USI::DispatchPtrID) +
      USI::getNumUserSGPRForField(USI::QueuePtrID) +
      USI::getNumUserSGPRForField(USI::KernargSegmentPtrID) +
      USI::getNumUserSGPRForField(USI::DispatchIdID) +
      USI::getNumUserSGPRForField(USI::FlatScratchInitID) +
      USI::getNumUserSGPRForField(USI::ImplicitBufferPtrID);

  // Max number of system SGPRs
  const unsigned MaxSystemSGPRs = 1 + // WorkGroupIDX
                                  1 + // WorkGroupIDY
                                  1 + // WorkGroupIDZ
                                  1 + // WorkGroupInfo
                                  1;  // private segment wave byte offset

  // Max number of synthetic SGPRs
  const unsigned SyntheticSGPRs = 1; // LDSKernelId

  return MaxUserSGPRs + MaxSystemSGPRs + SyntheticSGPRs;
}

unsigned GCNSubtarget::getMaxNumSGPRs(const Function &F) const {
  return getBaseMaxNumSGPRs(F, getWavesPerEU(F), getMaxNumPreloadedSGPRs(),
                            getReservedNumSGPRs(F));
}

unsigned GCNSubtarget::getBaseMaxNumVGPRs(
    const Function &F, std::pair<unsigned, unsigned> NumVGPRBounds) const {
  const auto [Min, Max] = NumVGPRBounds;

  // Check if maximum number of VGPRs was explicitly requested using
  // "amdgpu-num-vgpr" attribute.

  unsigned Requested = F.getFnAttributeAsParsedInteger("amdgpu-num-vgpr", Max);
  if (Requested != Max && hasGFX90AInsts())
    Requested *= 2;

  // Make sure requested value is inside the range of possible VGPR usage.
  return std::clamp(Requested, Min, Max);
}

unsigned GCNSubtarget::getMaxNumVGPRs(const Function &F) const {
  // Temporarily check both the attribute and the subtarget feature, until the
  // latter is removed.
  unsigned DynamicVGPRBlockSize = AMDGPU::getDynamicVGPRBlockSize(F);
  if (DynamicVGPRBlockSize == 0 && isDynamicVGPREnabled())
    DynamicVGPRBlockSize = getDynamicVGPRBlockSize();

  std::pair<unsigned, unsigned> Waves = getWavesPerEU(F);
  return getBaseMaxNumVGPRs(
      F, {getMinNumVGPRs(Waves.second, DynamicVGPRBlockSize),
          getMaxNumVGPRs(Waves.first, DynamicVGPRBlockSize)});
}

unsigned GCNSubtarget::getMaxNumVGPRs(const MachineFunction &MF) const {
  return getMaxNumVGPRs(MF.getFunction());
}

std::pair<unsigned, unsigned>
GCNSubtarget::getMaxNumVectorRegs(const Function &F) const {
  const unsigned MaxVectorRegs = getMaxNumVGPRs(F);

  unsigned MaxNumVGPRs = MaxVectorRegs;
  unsigned MaxNumAGPRs = 0;
  unsigned NumArchVGPRs = getAddressableNumArchVGPRs();

  // On GFX90A, the number of VGPRs and AGPRs need not be equal. Theoretically,
  // a wave may have up to 512 total vector registers combining together both
  // VGPRs and AGPRs. Hence, in an entry function without calls and without
  // AGPRs used within it, it is possible to use the whole vector register
  // budget for VGPRs.
  //
  // TODO: it shall be possible to estimate maximum AGPR/VGPR pressure and split
  //       register file accordingly.
  if (hasGFX90AInsts()) {
    unsigned MinNumAGPRs = 0;
    const unsigned TotalNumAGPRs = AMDGPU::AGPR_32RegClass.getNumRegs();

    const std::pair<unsigned, unsigned> DefaultNumAGPR = {~0u, ~0u};

    // TODO: The lower bound should probably force the number of required
    // registers up, overriding amdgpu-waves-per-eu.
    std::tie(MinNumAGPRs, MaxNumAGPRs) =
        AMDGPU::getIntegerPairAttribute(F, "amdgpu-agpr-alloc", DefaultNumAGPR,
                                        /*OnlyFirstRequired=*/true);

    if (MinNumAGPRs == DefaultNumAGPR.first) {
      // Default to splitting half the registers if AGPRs are required.
      MinNumAGPRs = MaxNumAGPRs = MaxVectorRegs / 2;
    } else {
      // Align to accum_offset's allocation granularity.
      MinNumAGPRs = alignTo(MinNumAGPRs, 4);

      MinNumAGPRs = std::min(MinNumAGPRs, TotalNumAGPRs);
    }

    // Clamp values to be inbounds of our limits, and ensure min <= max.

    MaxNumAGPRs = std::min(std::max(MinNumAGPRs, MaxNumAGPRs), MaxVectorRegs);
    MinNumAGPRs = std::min({MinNumAGPRs, TotalNumAGPRs, MaxNumAGPRs});

    MaxNumVGPRs = std::min(MaxVectorRegs - MinNumAGPRs, NumArchVGPRs);
    MaxNumAGPRs = std::min(MaxVectorRegs - MaxNumVGPRs, MaxNumAGPRs);

    assert(MaxNumVGPRs + MaxNumAGPRs <= MaxVectorRegs &&
           MaxNumAGPRs <= TotalNumAGPRs && MaxNumVGPRs <= NumArchVGPRs &&
           "invalid register counts");
  } else if (hasMAIInsts()) {
    // On gfx908 the number of AGPRs always equals the number of VGPRs.
    MaxNumAGPRs = MaxNumVGPRs = MaxVectorRegs;
  }

  return std::pair(MaxNumVGPRs, MaxNumAGPRs);
}

// Check to which source operand UseOpIdx points to and return a pointer to the
// operand of the corresponding source modifier.
// Return nullptr if UseOpIdx either doesn't point to src0/1/2 or if there is no
// operand for the corresponding source modifier.
static const MachineOperand *
getVOP3PSourceModifierFromOpIdx(const MachineInstr &UseI, int UseOpIdx,
                                const SIInstrInfo &InstrInfo) {
  AMDGPU::OpName UseName =
      AMDGPU::getOperandIdxName(UseI.getOpcode(), UseOpIdx);
  switch (UseName) {
  case AMDGPU::OpName::src0:
    return InstrInfo.getNamedOperand(UseI, AMDGPU::OpName::src0_modifiers);
  case AMDGPU::OpName::src1:
    return InstrInfo.getNamedOperand(UseI, AMDGPU::OpName::src1_modifiers);
  case AMDGPU::OpName::src2:
    return InstrInfo.getNamedOperand(UseI, AMDGPU::OpName::src2_modifiers);
  default:
    return nullptr;
  }
}

// Get the subreg idx of the subreg that is used by the given instruction
// operand, considering the given op_sel modifier.
// Return 0 if the whole register is used or as a conservative fallback.
static unsigned getEffectiveSubRegIdx(const SIRegisterInfo &TRI,
                                      const SIInstrInfo &InstrInfo,
                                      const MachineInstr &I,
                                      const MachineOperand &Op) {
  if (!InstrInfo.isVOP3P(I) || InstrInfo.isWMMA(I) || InstrInfo.isSWMMAC(I))
    return AMDGPU::NoSubRegister;

  const MachineOperand *OpMod =
      getVOP3PSourceModifierFromOpIdx(I, Op.getOperandNo(), InstrInfo);
  if (!OpMod)
    return AMDGPU::NoSubRegister;

  // Note: the FMA_MIX* and MAD_MIX* instructions have different semantics for
  // the op_sel and op_sel_hi source modifiers:
  // - op_sel: selects low/high operand bits as input to the operation;
  //           has only meaning for 16-bit source operands
  // - op_sel_hi: specifies the size of the source operands (16 or 32 bits);
  //              a value of 0 indicates 32 bit, 1 indicates 16 bit
  // For the other VOP3P instructions, the semantics are:
  // - op_sel: selects low/high operand bits as input to the operation which
  //           results in the lower-half of the destination
  // - op_sel_hi: selects the low/high operand bits as input to the operation
  //              which results in the higher-half of the destination
  int64_t OpSel = OpMod->getImm() & SISrcMods::OP_SEL_0;
  int64_t OpSelHi = OpMod->getImm() & SISrcMods::OP_SEL_1;

  // Check if all parts of the register are being used (= op_sel and op_sel_hi
  // differ for VOP3P or op_sel_hi=0 for VOP3PMix). In that case we can return
  // early.
  if ((!InstrInfo.isVOP3PMix(I) && (!OpSel || !OpSelHi) &&
       (OpSel || OpSelHi)) ||
      (InstrInfo.isVOP3PMix(I) && !OpSelHi))
    return AMDGPU::NoSubRegister;

  const MachineRegisterInfo &MRI = I.getParent()->getParent()->getRegInfo();
  const TargetRegisterClass *RC = TRI.getRegClassForOperandReg(MRI, Op);

  if (unsigned SubRegIdx = OpSel ? AMDGPU::sub1 : AMDGPU::sub0;
      TRI.getSubClassWithSubReg(RC, SubRegIdx) == RC)
    return SubRegIdx;
  if (unsigned SubRegIdx = OpSel ? AMDGPU::hi16 : AMDGPU::lo16;
      TRI.getSubClassWithSubReg(RC, SubRegIdx) == RC)
    return SubRegIdx;

  return AMDGPU::NoSubRegister;
}

Register GCNSubtarget::getRealSchedDependency(const MachineInstr &DefI,
                                              int DefOpIdx,
                                              const MachineInstr &UseI,
                                              int UseOpIdx) const {
  const SIRegisterInfo *TRI = getRegisterInfo();
  const MachineOperand &DefOp = DefI.getOperand(DefOpIdx);
  const MachineOperand &UseOp = UseI.getOperand(UseOpIdx);
  Register DefReg = DefOp.getReg();
  Register UseReg = UseOp.getReg();

  // If the registers aren't restricted to a sub-register, there is no point in
  // further analysis. This check makes only sense for virtual registers because
  // physical registers may form a tuple and thus be part of a superregister
  // although they are not a subregister themselves (vgpr0 is a "subreg" of
  // vgpr0_vgpr1 without being a subreg in itself).
  unsigned DefSubRegIdx = DefOp.getSubReg();
  if (DefReg.isVirtual() && DefSubRegIdx == AMDGPU::NoSubRegister)
    return DefReg;
  unsigned UseSubRegIdx = getEffectiveSubRegIdx(*TRI, InstrInfo, UseI, UseOp);
  if (UseReg.isVirtual() && UseSubRegIdx == AMDGPU::NoSubRegister)
    return DefReg;

  if (!TRI->checkSubRegInterference(DefReg, DefSubRegIdx, UseReg, UseSubRegIdx))
    return Register(); // No real dependency

  // UseReg might be smaller or larger than DefReg, depending on the subreg and
  // on whether DefReg is a subreg, too. -> Find the smaller one.  This does not
  // apply to virtual registers because we cannot construct a subreg for them.
  if (DefReg.isVirtual())
    return DefReg;
  MCRegister DefMCReg =
      DefSubRegIdx ? TRI->getSubReg(DefReg, DefSubRegIdx) : DefReg.asMCReg();
  MCRegister UseMCReg =
      UseSubRegIdx ? TRI->getSubReg(UseReg, UseSubRegIdx) : UseReg.asMCReg();
  return TRI->isSubRegisterEq(DefMCReg, UseMCReg) ? UseMCReg : DefMCReg;
}

void GCNSubtarget::adjustSchedDependency(
    SUnit *Def, int DefOpIdx, SUnit *Use, int UseOpIdx, SDep &Dep,
    const TargetSchedModel *SchedModel) const {
  if (Dep.getKind() != SDep::Kind::Data || !Dep.getReg() || !Def->isInstr() ||
      !Use->isInstr())
    return;

  MachineInstr *DefI = Def->getInstr();
  MachineInstr *UseI = Use->getInstr();

  // Check for false latency on $tensorcnt / $asynccnt dependencies
  if (Dep.getReg() == AMDGPU::TENSORcnt || Dep.getReg() == AMDGPU::ASYNCcnt) {
    unsigned UseOp = UseI->getOpcode();
    // Do not adjust latency for load->s_wait
    bool IsBarrierCase =
        InstrInfo.isLDSDMA(*DefI) &&
        (UseOp == AMDGPU::S_WAIT_TENSORCNT || UseOp == AMDGPU::S_WAIT_ASYNCCNT);
    if (!IsBarrierCase) {
      Dep.setLatency(1);
      return;
    }
  }

  if (Register Reg = getRealSchedDependency(*DefI, DefOpIdx, *UseI, UseOpIdx)) {
    Dep.setReg(Reg);
  } else {
    Dep = SDep(Def, SDep::Artificial);
    return; // This is not a data dependency anymore.
  }

  if (DefI->isBundle()) {
    const SIRegisterInfo *TRI = getRegisterInfo();
    auto Reg = Dep.getReg();
    MachineBasicBlock::const_instr_iterator I(DefI->getIterator());
    MachineBasicBlock::const_instr_iterator E(DefI->getParent()->instr_end());
    unsigned Lat = 0;
    for (++I; I != E && I->isBundledWithPred(); ++I) {
      if (I->isMetaInstruction())
        continue;
      if (I->modifiesRegister(Reg, TRI))
        Lat = InstrInfo.getInstrLatency(getInstrItineraryData(), *I);
      else if (Lat)
        --Lat;
    }
    Dep.setLatency(Lat);
  } else if (UseI->isBundle()) {
    const SIRegisterInfo *TRI = getRegisterInfo();
    auto Reg = Dep.getReg();
    MachineBasicBlock::const_instr_iterator I(UseI->getIterator());
    MachineBasicBlock::const_instr_iterator E(UseI->getParent()->instr_end());
    unsigned Lat = InstrInfo.getInstrLatency(getInstrItineraryData(), *DefI);
    for (++I; I != E && I->isBundledWithPred() && Lat; ++I) {
      if (I->isMetaInstruction())
        continue;
      if (I->readsRegister(Reg, TRI))
        break;
      --Lat;
    }
    Dep.setLatency(Lat);
  } else if (Dep.getLatency() == 0 && Dep.getReg() == AMDGPU::VCC_LO) {
    // Work around the fact that SIInstrInfo::fixImplicitOperands modifies
    // implicit operands which come from the MCInstrDesc, which can fool
    // ScheduleDAGInstrs::addPhysRegDataDeps into treating them as implicit
    // pseudo operands.
    Dep.setLatency(InstrInfo.getSchedModel().computeOperandLatency(
        DefI, DefOpIdx, UseI, UseOpIdx));
  }
}

unsigned GCNSubtarget::getNSAThreshold(const MachineFunction &MF) const {
  if (getGeneration() >= AMDGPUSubtarget::GFX12)
    return 0; // Not MIMG encoding.

  if (NSAThreshold.getNumOccurrences() > 0)
    return std::max(NSAThreshold.getValue(), 2u);

  int Value = MF.getFunction().getFnAttributeAsParsedInteger(
      "amdgpu-nsa-threshold", -1);
  if (Value > 0)
    return std::max(Value, 2);

  return NSAThreshold;
}

GCNUserSGPRUsageInfo::GCNUserSGPRUsageInfo(const Function &F,
                                           const GCNSubtarget &ST)
    : ST(ST) {
  const CallingConv::ID CC = F.getCallingConv();
  const bool IsKernel =
      CC == CallingConv::AMDGPU_KERNEL || CC == CallingConv::SPIR_KERNEL;

  if (IsKernel && (!F.arg_empty() || ST.getImplicitArgNumBytes(F) != 0))
    KernargSegmentPtr = true;

  bool IsAmdHsaOrMesa = ST.isAmdHsaOrMesa(F);
  if (IsAmdHsaOrMesa && !ST.hasFlatScratchEnabled())
    PrivateSegmentBuffer = true;
  else if (ST.isMesaGfxShader(F))
    ImplicitBufferPtr = true;

  if (!AMDGPU::isGraphics(CC)) {
    if (!F.hasFnAttribute("amdgpu-no-dispatch-ptr"))
      DispatchPtr = true;

    // FIXME: Can this always be disabled with < COv5?
    if (!F.hasFnAttribute("amdgpu-no-queue-ptr"))
      QueuePtr = true;

    if (!F.hasFnAttribute("amdgpu-no-dispatch-id"))
      DispatchID = true;
  }

  if (ST.hasFlatAddressSpace() && AMDGPU::isEntryFunctionCC(CC) &&
      (IsAmdHsaOrMesa || ST.hasFlatScratchEnabled()) &&
      // FlatScratchInit cannot be true for graphics CC if
      // hasFlatScratchEnabled() is false.
      (ST.hasFlatScratchEnabled() ||
       (!AMDGPU::isGraphics(CC) &&
        !F.hasFnAttribute("amdgpu-no-flat-scratch-init"))) &&
      !ST.hasArchitectedFlatScratch()) {
    FlatScratchInit = true;
  }

  if (hasImplicitBufferPtr())
    NumUsedUserSGPRs += getNumUserSGPRForField(ImplicitBufferPtrID);

  if (hasPrivateSegmentBuffer())
    NumUsedUserSGPRs += getNumUserSGPRForField(PrivateSegmentBufferID);

  if (hasDispatchPtr())
    NumUsedUserSGPRs += getNumUserSGPRForField(DispatchPtrID);

  if (hasQueuePtr())
    NumUsedUserSGPRs += getNumUserSGPRForField(QueuePtrID);

  if (hasKernargSegmentPtr())
    NumUsedUserSGPRs += getNumUserSGPRForField(KernargSegmentPtrID);

  if (hasDispatchID())
    NumUsedUserSGPRs += getNumUserSGPRForField(DispatchIdID);

  if (hasFlatScratchInit())
    NumUsedUserSGPRs += getNumUserSGPRForField(FlatScratchInitID);

  if (hasPrivateSegmentSize())
    NumUsedUserSGPRs += getNumUserSGPRForField(PrivateSegmentSizeID);
}

void GCNUserSGPRUsageInfo::allocKernargPreloadSGPRs(unsigned NumSGPRs) {
  assert(NumKernargPreloadSGPRs + NumSGPRs <= AMDGPU::getMaxNumUserSGPRs(ST));
  NumKernargPreloadSGPRs += NumSGPRs;
  NumUsedUserSGPRs += NumSGPRs;
}

unsigned GCNUserSGPRUsageInfo::getNumFreeUserSGPRs() {
  return AMDGPU::getMaxNumUserSGPRs(ST) - NumUsedUserSGPRs;
}