SPIRVUtils.cpp

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//===--- SPIRVUtils.cpp ---- SPIR-V Utility Functions -----------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file contains miscellaneous utility functions.
//
//===----------------------------------------------------------------------===//
 
#include "SPIRVUtils.h"
#include "MCTargetDesc/SPIRVBaseInfo.h"
#include "SPIRV.h"
#include "SPIRVBuiltins.h"
#include "SPIRVGlobalRegistry.h"
#include "SPIRVInstrInfo.h"
#include "SPIRVSubtarget.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/CodeGen/GlobalISel/GenericMachineInstrs.h"
#include "llvm/CodeGen/GlobalISel/MachineIRBuilder.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/Demangle/Demangle.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/IntrinsicsSPIRV.h"
#include "llvm/Support/MathExtras.h"
#include <cstring>
#include <queue>
#include <vector>
 
namespace llvm {
namespace SPIRV {
// This code restores function args/retvalue types for composite cases
// because the final types should still be aggregate whereas they're i32
// during the translation to cope with aggregate flattening etc.
// TODO: should these just return nullptr when there's no metadata?
static FunctionType *extractFunctionTypeFromMetadata(NamedMDNode *NMD,
                                                     FunctionType *FTy,
                                                     StringRef Name) {
  if (!NMD)
    return FTy;
 
  auto It = find_if(NMD->operands(), [Name](MDNode *N) {
    if (auto *MDS = dyn_cast_or_null<MDString>(N->getOperand(0)))
      return MDS->getString() == Name;
    return false;
  });
 
  if (It == NMD->op_end())
    return FTy;
 
  Type *RetTy = FTy->getReturnType();
  SmallVector<Type *, 4> PTys(FTy->params());
 
  for (unsigned I = 1; I != (*It)->getNumOperands(); ++I) {
    MDNode *MD = dyn_cast<MDNode>((*It)->getOperand(I));
    assert(MD && "MDNode operand is expected");
 
    if (auto *Const = getMDOperandAsConstInt(MD, 0)) {
      auto *CMeta = dyn_cast<ConstantAsMetadata>(MD->getOperand(1));
      assert(CMeta && "ConstantAsMetadata operand is expected");
      int64_t Idx = Const->getSExtValue();
      // Currently -1 indicates return value, greater values mean
      // argument numbers.
      if (Idx == -1) {
        RetTy = CMeta->getType();
        continue;
      }
      if (Idx >= 0 && static_cast<uint64_t>(Idx) < PTys.size()) {
        PTys[Idx] = CMeta->getType();
        continue;
      }
      report_fatal_error("invalid argument index in function type metadata");
    }
  }
 
  return FunctionType::get(RetTy, PTys, FTy->isVarArg());
}
 
static StringRef extractAsmConstraintsFromMetadata(NamedMDNode *NMD,
                                                   StringRef Constraints,
                                                   StringRef Name) {
  // TODO: unify the extractors.
  if (!NMD)
    return Constraints;
 
  auto It = find_if(NMD->operands(), [Name](MDNode *N) {
    if (auto *MDS = dyn_cast_or_null<MDString>(N->getOperand(0)))
      return MDS->getString() == Name;
    return false;
  });
 
  if (It == NMD->op_end())
    return Constraints;
 
  // By convention, the constraints string is stored in the final MD operand.
  MDNode *MD = dyn_cast<MDNode>((*It)->getOperand((*It)->getNumOperands() - 1));
  assert(MD && "MDNode operand is expected");
 
  if (auto *MDS = dyn_cast<MDString>(MD->getOperand(0)))
    Constraints = MDS->getString();
 
  return Constraints;
}
 
FunctionType *getOriginalFunctionType(const Function &F) {
  return extractFunctionTypeFromMetadata(
      F.getParent()->getNamedMetadata("spv.cloned_funcs"), F.getFunctionType(),
      F.getName());
}
 
// Keyed via instruction metadata, not a name.
static std::optional<StringRef> getMutatedCallsiteKey(const CallBase &CB) {
  if (MDNode *MD = CB.getMetadata("spv.mutated_callsite"))
    if (MD->getNumOperands() > 0)
      if (auto *MDS = dyn_cast<MDString>(MD->getOperand(0)))
        return MDS->getString();
  return std::nullopt;
}
 
FunctionType *getOriginalFunctionType(const CallBase &CB) {
  std::optional<StringRef> Key = getMutatedCallsiteKey(CB);
  if (!Key)
    return CB.getFunctionType();
  return extractFunctionTypeFromMetadata(
      CB.getModule()->getNamedMetadata("spv.mutated_callsites"),
      CB.getFunctionType(), *Key);
}
 
StringRef getOriginalAsmConstraints(const CallBase &CB) {
  StringRef Constraints =
      cast<InlineAsm>(CB.getCalledOperand())->getConstraintString();
  std::optional<StringRef> Key = getMutatedCallsiteKey(CB);
  if (!Key)
    return Constraints;
  return extractAsmConstraintsFromMetadata(
      CB.getModule()->getNamedMetadata("spv.mutated_callsites"), Constraints,
      *Key);
}
} // Namespace SPIRV
 
// The following functions are used to add these string literals as a series of
// 32-bit integer operands with the correct format, and unpack them if necessary
// when making string comparisons in compiler passes.
// SPIR-V requires null-terminated UTF-8 strings padded to 32-bit alignment.
static uint32_t convertCharsToWord(StringRef Str, unsigned i) {
  uint32_t Word = 0u; // Padding/null bytes are zero-initialized.
  unsigned Count = std::min(static_cast<size_t>(4), Str.size() - i);
  std::memcpy(&Word, Str.data() + i, Count);
  return Word;
}
 
// Get length including padding and null terminator.
static size_t getPaddedLen(StringRef Str) { return alignTo(Str.size() + 1, 4); }
 
void addStringImm(StringRef Str, MCInst &Inst) {
  const size_t PaddedLen = getPaddedLen(Str);
  for (unsigned i = 0; i < PaddedLen; i += 4) {
    // Add an operand for the 32-bits of chars or padding.
    Inst.addOperand(MCOperand::createImm(convertCharsToWord(Str, i)));
  }
}
 
void addStringImm(StringRef Str, MachineInstrBuilder &MIB) {
  const size_t PaddedLen = getPaddedLen(Str);
  for (unsigned i = 0; i < PaddedLen; i += 4) {
    // Add an operand for the 32-bits of chars or padding.
    MIB.addImm(convertCharsToWord(Str, i));
  }
}
 
std::string getStringImm(const MachineInstr &MI, unsigned StartIndex) {
  return getSPIRVStringOperand(MI, StartIndex);
}
 
std::string getStringValueFromReg(Register Reg, MachineRegisterInfo &MRI) {
  MachineInstr *Def = getVRegDef(MRI, Reg);
  assert(Def && Def->getOpcode() == TargetOpcode::G_GLOBAL_VALUE &&
         "Expected G_GLOBAL_VALUE");
  const GlobalValue *GV = Def->getOperand(1).getGlobal();
  Value *V = GV->getOperand(0);
  const ConstantDataArray *CDA = cast<ConstantDataArray>(V);
  return CDA->getAsCString().str();
}
 
void addNumImm(const APInt &Imm, MachineInstrBuilder &MIB) {
  const auto Bitwidth = Imm.getBitWidth();
  if (Bitwidth == 1)
    return; // Already handled
  else if (Bitwidth <= 32) {
    MIB.addImm(Imm.getZExtValue());
    // Asm Printer needs this info to print floating-type correctly
    if (Bitwidth == 16)
      MIB.getInstr()->setAsmPrinterFlag(SPIRV::ASM_PRINTER_WIDTH16);
    return;
  } else if (Bitwidth <= 64) {
    uint64_t FullImm = Imm.getZExtValue();
    MIB.addImm(Lo_32(FullImm)).addImm(Hi_32(FullImm));
    // Asm Printer needs this info to print 64-bit operands correctly
    MIB.getInstr()->setAsmPrinterFlag(SPIRV::ASM_PRINTER_WIDTH64);
    return;
  } else {
    // Emit ceil(Bitwidth / 32) words to conform SPIR-V spec.
    unsigned NumWords = divideCeil(Bitwidth, 32);
    for (unsigned I = 0; I < NumWords; ++I) {
      unsigned LimbIdx = I / 2;
      unsigned LimbShift = (I % 2) * 32;
      uint32_t Word = (Imm.getRawData()[LimbIdx] >> LimbShift) & 0xffffffff;
      MIB.addImm(Word);
    }
    return;
  }
}
 
void buildOpName(Register Target, StringRef Name,
                 MachineIRBuilder &MIRBuilder) {
  if (!Name.empty()) {
    auto MIB = MIRBuilder.buildInstr(SPIRV::OpName).addUse(Target);
    addStringImm(Name, MIB);
  }
}
 
void buildOpName(Register Target, StringRef Name, MachineInstr &I,
                 const SPIRVInstrInfo &TII) {
  if (!Name.empty()) {
    auto MIB =
        BuildMI(*I.getParent(), I, I.getDebugLoc(), TII.get(SPIRV::OpName))
            .addUse(Target);
    addStringImm(Name, MIB);
  }
}
 
static void finishBuildOpDecorate(MachineInstrBuilder &MIB,
                                  ArrayRef<uint32_t> DecArgs,
                                  StringRef StrImm) {
  if (!StrImm.empty())
    addStringImm(StrImm, MIB);
  for (const auto &DecArg : DecArgs)
    MIB.addImm(DecArg);
}
 
void buildOpDecorate(Register Reg, MachineIRBuilder &MIRBuilder,
                     SPIRV::Decoration::Decoration Dec,
                     ArrayRef<uint32_t> DecArgs, StringRef StrImm) {
  auto MIB = MIRBuilder.buildInstr(SPIRV::OpDecorate)
                 .addUse(Reg)
                 .addImm(static_cast<uint32_t>(Dec));
  finishBuildOpDecorate(MIB, DecArgs, StrImm);
}
 
void buildOpDecorate(Register Reg, MachineInstr &I, const SPIRVInstrInfo &TII,
                     SPIRV::Decoration::Decoration Dec,
                     ArrayRef<uint32_t> DecArgs, StringRef StrImm) {
  MachineBasicBlock &MBB = *I.getParent();
  auto MIB = BuildMI(MBB, I, I.getDebugLoc(), TII.get(SPIRV::OpDecorate))
                 .addUse(Reg)
                 .addImm(static_cast<uint32_t>(Dec));
  finishBuildOpDecorate(MIB, DecArgs, StrImm);
}
 
void buildOpMemberDecorate(Register Reg, MachineIRBuilder &MIRBuilder,
                           SPIRV::Decoration::Decoration Dec, uint32_t Member,
                           ArrayRef<uint32_t> DecArgs, StringRef StrImm) {
  auto MIB = MIRBuilder.buildInstr(SPIRV::OpMemberDecorate)
                 .addUse(Reg)
                 .addImm(Member)
                 .addImm(static_cast<uint32_t>(Dec));
  finishBuildOpDecorate(MIB, DecArgs, StrImm);
}
 
void buildOpSpirvDecorations(Register Reg, MachineIRBuilder &MIRBuilder,
                             const MDNode *GVarMD, const SPIRVSubtarget &ST) {
  for (unsigned I = 0, E = GVarMD->getNumOperands(); I != E; ++I) {
    auto *OpMD = dyn_cast<MDNode>(GVarMD->getOperand(I));
    if (!OpMD)
      report_fatal_error("Invalid decoration");
    if (OpMD->getNumOperands() == 0)
      report_fatal_error("Expect operand(s) of the decoration");
    ConstantInt *DecorationId =
        mdconst::dyn_extract<ConstantInt>(OpMD->getOperand(0));
    if (!DecorationId)
      report_fatal_error("Expect SPIR-V <Decoration> operand to be the first "
                         "element of the decoration");
 
    // The goal of `spirv.Decorations` metadata is to provide a way to
    // represent SPIR-V entities that do not map to LLVM in an obvious way.
    // FP flags do have obvious matches between LLVM IR and SPIR-V.
    // Additionally, we have no guarantee at this point that the flags passed
    // through the decoration are not violated already in the optimizer passes.
    // Therefore, we simply ignore FP flags, including NoContraction, and
    // FPFastMathMode.
    if (DecorationId->getZExtValue() ==
            static_cast<uint32_t>(SPIRV::Decoration::NoContraction) ||
        DecorationId->getZExtValue() ==
            static_cast<uint32_t>(SPIRV::Decoration::FPFastMathMode)) {
      continue; // Ignored.
    }
    auto MIB = MIRBuilder.buildInstr(SPIRV::OpDecorate)
                   .addUse(Reg)
                   .addImm(static_cast<uint32_t>(DecorationId->getZExtValue()));
    for (unsigned OpI = 1, OpE = OpMD->getNumOperands(); OpI != OpE; ++OpI) {
      if (ConstantInt *OpV =
              mdconst::dyn_extract<ConstantInt>(OpMD->getOperand(OpI)))
        MIB.addImm(static_cast<uint32_t>(OpV->getZExtValue()));
      else if (MDString *OpV = dyn_cast<MDString>(OpMD->getOperand(OpI)))
        addStringImm(OpV->getString(), MIB);
      else
        report_fatal_error("Unexpected operand of the decoration");
    }
  }
}
 
MachineBasicBlock::iterator getOpVariableMBBIt(MachineFunction &MF) {
  MachineBasicBlock &MBB = MF.front();
  // Find the position to insert the OpVariable instruction.
  // We will insert it after the last OpFunctionParameter, if any, or
  // after OpFunction otherwise.
  auto IsPreamble = [](const MachineInstr &MI) {
    switch (MI.getOpcode()) {
    case SPIRV::OpFunction:
    case SPIRV::OpFunctionParameter:
    case SPIRV::OpLabel:
    case SPIRV::ASSIGN_TYPE:
      return true;
    default:
      return false;
    }
  };
  MachineBasicBlock::iterator VarPos = MBB.SkipPHIsAndLabels(MBB.begin());
  while (VarPos != MBB.end() && VarPos->getOpcode() != SPIRV::OpFunction)
    ++VarPos;
  // Advance past the preamble.
  while (VarPos != MBB.end() && IsPreamble(*VarPos))
    ++VarPos;
  return VarPos;
}
 
MachineBasicBlock::iterator getInsertPtValidEnd(MachineBasicBlock *MBB) {
  MachineBasicBlock::iterator I = MBB->end();
  if (I == MBB->begin())
    return I;
  --I;
  while (I->isTerminator() || I->isDebugValue()) {
    if (I == MBB->begin())
      break;
    --I;
  }
  return I;
}
 
SPIRV::StorageClass::StorageClass
addressSpaceToStorageClass(unsigned AddrSpace, const SPIRVSubtarget &STI) {
  switch (AddrSpace) {
  case 0:
    return SPIRV::StorageClass::Function;
  case 1:
    return SPIRV::StorageClass::CrossWorkgroup;
  case 2:
    return SPIRV::StorageClass::UniformConstant;
  case 3:
    return SPIRV::StorageClass::Workgroup;
  case 4:
    return SPIRV::StorageClass::Generic;
  case 5:
    return STI.canUseExtension(SPIRV::Extension::SPV_INTEL_usm_storage_classes)
               ? SPIRV::StorageClass::DeviceOnlyINTEL
               : SPIRV::StorageClass::CrossWorkgroup;
  case 6:
    return STI.canUseExtension(SPIRV::Extension::SPV_INTEL_usm_storage_classes)
               ? SPIRV::StorageClass::HostOnlyINTEL
               : SPIRV::StorageClass::CrossWorkgroup;
  case 7:
    return SPIRV::StorageClass::Input;
  case 8:
    return SPIRV::StorageClass::Output;
  case 9:
    return SPIRV::StorageClass::CodeSectionINTEL;
  case 10:
    return SPIRV::StorageClass::Private;
  case 11:
    return SPIRV::StorageClass::StorageBuffer;
  case 12:
    return SPIRV::StorageClass::Uniform;
  case 13:
    return SPIRV::StorageClass::PushConstant;
  default:
    report_fatal_error("Unknown address space");
  }
}
 
SPIRV::MemorySemantics::MemorySemantics
getMemSemanticsForStorageClass(SPIRV::StorageClass::StorageClass SC) {
  switch (SC) {
  case SPIRV::StorageClass::StorageBuffer:
  case SPIRV::StorageClass::Uniform:
    return SPIRV::MemorySemantics::UniformMemory;
  case SPIRV::StorageClass::Workgroup:
    return SPIRV::MemorySemantics::WorkgroupMemory;
  case SPIRV::StorageClass::CrossWorkgroup:
    return SPIRV::MemorySemantics::CrossWorkgroupMemory;
  case SPIRV::StorageClass::AtomicCounter:
    return SPIRV::MemorySemantics::AtomicCounterMemory;
  case SPIRV::StorageClass::Image:
    return SPIRV::MemorySemantics::ImageMemory;
  default:
    return SPIRV::MemorySemantics::None;
  }
}
 
SPIRV::MemorySemantics::MemorySemantics getMemSemantics(AtomicOrdering Ord) {
  switch (Ord) {
  case AtomicOrdering::Acquire:
    return SPIRV::MemorySemantics::Acquire;
  case AtomicOrdering::Release:
    return SPIRV::MemorySemantics::Release;
  case AtomicOrdering::AcquireRelease:
    return SPIRV::MemorySemantics::AcquireRelease;
  case AtomicOrdering::SequentiallyConsistent:
    return SPIRV::MemorySemantics::SequentiallyConsistent;
  case AtomicOrdering::Unordered:
  case AtomicOrdering::Monotonic:
  case AtomicOrdering::NotAtomic:
    return SPIRV::MemorySemantics::None;
  }
  llvm_unreachable(nullptr);
}
 
SPIRV::Scope::Scope getMemScope(LLVMContext &Ctx, SyncScope::ID Id) {
  // Named by
  // https://registry.khronos.org/SPIR-V/specs/unified1/SPIRV.html#_scope_id.
  // We don't need aliases for Invocation and CrossDevice, as we already have
  // them covered by "singlethread" and "" strings respectively (see
  // implementation of LLVMContext::LLVMContext()).
  static const llvm::SyncScope::ID SubGroup =
      Ctx.getOrInsertSyncScopeID("subgroup");
  static const llvm::SyncScope::ID WorkGroup =
      Ctx.getOrInsertSyncScopeID("workgroup");
  static const llvm::SyncScope::ID Device =
      Ctx.getOrInsertSyncScopeID("device");
 
  if (Id == llvm::SyncScope::SingleThread)
    return SPIRV::Scope::Invocation;
  else if (Id == llvm::SyncScope::System)
    return SPIRV::Scope::CrossDevice;
  else if (Id == SubGroup)
    return SPIRV::Scope::Subgroup;
  else if (Id == WorkGroup)
    return SPIRV::Scope::Workgroup;
  else if (Id == Device)
    return SPIRV::Scope::Device;
  return SPIRV::Scope::CrossDevice;
}
 
MachineInstr *getDefInstrMaybeConstant(Register &ConstReg,
                                       const MachineRegisterInfo *MRI) {
  MachineInstr *MI = MRI->getVRegDef(ConstReg);
  MachineInstr *ConstInstr =
      MI->getOpcode() == SPIRV::G_TRUNC || MI->getOpcode() == SPIRV::G_ZEXT
          ? MRI->getVRegDef(MI->getOperand(1).getReg())
          : MI;
  if (auto *GI = dyn_cast<GIntrinsic>(ConstInstr)) {
    if (GI->is(Intrinsic::spv_track_constant)) {
      ConstReg = ConstInstr->getOperand(2).getReg();
      return MRI->getVRegDef(ConstReg);
    }
  } else if (ConstInstr->getOpcode() == SPIRV::ASSIGN_TYPE) {
    ConstReg = ConstInstr->getOperand(1).getReg();
    return MRI->getVRegDef(ConstReg);
  } else if (ConstInstr->getOpcode() == TargetOpcode::G_CONSTANT ||
             ConstInstr->getOpcode() == TargetOpcode::G_FCONSTANT) {
    ConstReg = ConstInstr->getOperand(0).getReg();
    return ConstInstr;
  }
  return MRI->getVRegDef(ConstReg);
}
 
uint64_t getIConstVal(Register ConstReg, const MachineRegisterInfo *MRI) {
  const MachineInstr *MI = getDefInstrMaybeConstant(ConstReg, MRI);
  assert(MI && MI->getOpcode() == TargetOpcode::G_CONSTANT);
  return MI->getOperand(1).getCImm()->getValue().getZExtValue();
}
 
int64_t getIConstValSext(Register ConstReg, const MachineRegisterInfo *MRI) {
  const MachineInstr *MI = getDefInstrMaybeConstant(ConstReg, MRI);
  assert(MI && MI->getOpcode() == TargetOpcode::G_CONSTANT);
  return MI->getOperand(1).getCImm()->getSExtValue();
}
 
bool isSpvIntrinsic(const MachineInstr &MI, Intrinsic::ID IntrinsicID) {
  if (const auto *GI = dyn_cast<GIntrinsic>(&MI))
    return GI->is(IntrinsicID);
  return false;
}
 
Type *getMDOperandAsType(const MDNode *N, unsigned I) {
  Type *ElementTy = cast<ValueAsMetadata>(N->getOperand(I))->getType();
  return toTypedPointer(ElementTy);
}
 
ConstantInt *getMDOperandAsConstInt(const MDNode *N, unsigned I) {
  if (N->getNumOperands() <= I)
    return nullptr;
  if (auto *CMeta = dyn_cast<ConstantAsMetadata>(N->getOperand(I)))
    return dyn_cast<ConstantInt>(CMeta->getValue());
  return nullptr;
}
 
static bool isEnqueueKernelBI(StringRef MangledName) {
  return MangledName == "__enqueue_kernel_basic" ||
         MangledName == "__enqueue_kernel_basic_events" ||
         MangledName == "__enqueue_kernel_varargs" ||
         MangledName == "__enqueue_kernel_events_varargs";
}
 
static bool isKernelQueryBI(StringRef MangledName) {
  return MangledName == "__get_kernel_work_group_size_impl" ||
         MangledName == "__get_kernel_sub_group_count_for_ndrange_impl" ||
         MangledName == "__get_kernel_max_sub_group_size_for_ndrange_impl" ||
         MangledName == "__get_kernel_preferred_work_group_size_multiple_impl";
}
 
static bool isNonMangledOCLBuiltin(StringRef Name) {
  if (!Name.starts_with("__"))
    return false;
 
  return isEnqueueKernelBI(Name) || isKernelQueryBI(Name) ||
         SPIRV::isPipeOrAddressSpaceCastBuiltin(Name) ||
         Name == "__translate_sampler_initializer";
}
 
std::string getOclOrSpirvBuiltinDemangledName(StringRef Name) {
  bool IsNonMangledOCL = isNonMangledOCLBuiltin(Name);
  bool IsNonMangledSPIRV = Name.starts_with("__spirv_");
  bool IsNonMangledHLSL = Name.starts_with("__hlsl_");
  bool IsMangled = Name.starts_with("_Z");
 
  // Otherwise use simple demangling to return the function name.
  if (IsNonMangledOCL || IsNonMangledSPIRV || IsNonMangledHLSL || !IsMangled)
    return Name.str();
 
  // Try to use the itanium demangler.
  if (char *DemangledName = itaniumDemangle(Name.data())) {
    std::string Result = DemangledName;
    free(DemangledName);
    return Result;
  }
 
  // Autocheck C++, maybe need to do explicit check of the source language.
  // OpenCL C++ built-ins are declared in cl namespace.
  // TODO: consider using 'St' abbriviation for cl namespace mangling.
  // Similar to ::std:: in C++.
  size_t Start, Len = 0;
  size_t DemangledNameLenStart = 2;
  if (Name.starts_with("_ZN")) {
    // Skip CV and ref qualifiers.
    size_t NameSpaceStart = Name.find_first_not_of("rVKRO", 3);
    // All built-ins are in the ::cl:: namespace.
    if (Name.substr(NameSpaceStart, 11) != "2cl7__spirv")
      return std::string();
    DemangledNameLenStart = NameSpaceStart + 11;
  }
  Start = Name.find_first_not_of("0123456789", DemangledNameLenStart);
  bool Error = Name.substr(DemangledNameLenStart, Start - DemangledNameLenStart)
                   .getAsInteger(10, Len);
  if (Error)
    return std::string();
  return Name.substr(Start, Len).str();
}
 
bool hasBuiltinTypePrefix(StringRef Name) {
  if (Name.starts_with("opencl.") || Name.starts_with("ocl_") ||
      Name.starts_with("spirv."))
    return true;
  return false;
}
 
bool isSpecialOpaqueType(const Type *Ty) {
  if (const TargetExtType *ExtTy = dyn_cast<TargetExtType>(Ty))
    return isTypedPointerWrapper(ExtTy)
               ? false
               : hasBuiltinTypePrefix(ExtTy->getName());
 
  return false;
}
 
bool isEntryPoint(const Function &F) {
  // OpenCL handling: any function with the SPIR_KERNEL
  // calling convention will be a potential entry point.
  if (F.getCallingConv() == CallingConv::SPIR_KERNEL)
    return true;
 
  // HLSL handling: special attribute are emitted from the
  // front-end.
  if (F.getFnAttribute("hlsl.shader").isValid())
    return true;
 
  return false;
}
 
Type *parseBasicTypeName(StringRef &TypeName, LLVMContext &Ctx) {
  TypeName.consume_front("atomic_");
  if (TypeName.consume_front("void"))
    return Type::getVoidTy(Ctx);
  else if (TypeName.consume_front("bool") || TypeName.consume_front("_Bool"))
    return Type::getIntNTy(Ctx, 1);
  else if (TypeName.consume_front("char") ||
           TypeName.consume_front("signed char") ||
           TypeName.consume_front("unsigned char") ||
           TypeName.consume_front("uchar"))
    return Type::getInt8Ty(Ctx);
  else if (TypeName.consume_front("short") ||
           TypeName.consume_front("signed short") ||
           TypeName.consume_front("unsigned short") ||
           TypeName.consume_front("ushort"))
    return Type::getInt16Ty(Ctx);
  else if (TypeName.consume_front("int") ||
           TypeName.consume_front("signed int") ||
           TypeName.consume_front("unsigned int") ||
           TypeName.consume_front("uint"))
    return Type::getInt32Ty(Ctx);
  else if (TypeName.consume_front("long") ||
           TypeName.consume_front("signed long") ||
           TypeName.consume_front("unsigned long") ||
           TypeName.consume_front("ulong"))
    return Type::getInt64Ty(Ctx);
  else if (TypeName.consume_front("half") ||
           TypeName.consume_front("_Float16") ||
           TypeName.consume_front("__fp16"))
    return Type::getHalfTy(Ctx);
  else if (TypeName.consume_front("float"))
    return Type::getFloatTy(Ctx);
  else if (TypeName.consume_front("double"))
    return Type::getDoubleTy(Ctx);
 
  // Unable to recognize SPIRV type name
  return nullptr;
}
 
SmallPtrSet<BasicBlock *, 0>
PartialOrderingVisitor::getReachableFrom(BasicBlock *Start) {
  std::queue<BasicBlock *> ToVisit;
  ToVisit.push(Start);
 
  SmallPtrSet<BasicBlock *, 0> Output;
  while (ToVisit.size() != 0) {
    BasicBlock *BB = ToVisit.front();
    ToVisit.pop();
 
    if (Output.count(BB) != 0)
      continue;
    Output.insert(BB);
 
    for (BasicBlock *Successor : successors(BB)) {
      if (DT.dominates(Successor, BB))
        continue;
      ToVisit.push(Successor);
    }
  }
 
  return Output;
}
 
bool PartialOrderingVisitor::CanBeVisited(BasicBlock *BB) const {
  for (BasicBlock *P : predecessors(BB)) {
    // Ignore back-edges.
    if (DT.dominates(BB, P))
      continue;
 
    // One of the predecessor hasn't been visited. Not ready yet.
    if (BlockToOrder.count(P) == 0)
      return false;
 
    // If the block is a loop exit, the loop must be finished before
    // we can continue.
    Loop *L = LI.getLoopFor(P);
    if (L == nullptr || L->contains(BB))
      continue;
 
    // SPIR-V requires a single back-edge. And the backend first
    // step transforms loops into the simplified format. If we have
    // more than 1 back-edge, something is wrong.
    assert(L->getNumBackEdges() <= 1);
 
    // If the loop has no latch, loop's rank won't matter, so we can
    // proceed.
    BasicBlock *Latch = L->getLoopLatch();
    assert(Latch);
    if (Latch == nullptr)
      continue;
 
    // The latch is not ready yet, let's wait.
    if (BlockToOrder.count(Latch) == 0)
      return false;
  }
 
  return true;
}
 
size_t PartialOrderingVisitor::GetNodeRank(BasicBlock *BB) const {
  auto It = BlockToOrder.find(BB);
  if (It != BlockToOrder.end())
    return It->second.Rank;
 
  size_t result = 0;
  for (BasicBlock *P : predecessors(BB)) {
    // Ignore back-edges.
    if (DT.dominates(BB, P))
      continue;
 
    auto Iterator = BlockToOrder.end();
    Loop *L = LI.getLoopFor(P);
    BasicBlock *Latch = L ? L->getLoopLatch() : nullptr;
 
    // If the predecessor is either outside a loop, or part of
    // the same loop, simply take its rank + 1.
    if (L == nullptr || L->contains(BB) || Latch == nullptr) {
      Iterator = BlockToOrder.find(P);
    } else {
      // Otherwise, take the loop's rank (highest rank in the loop) as base.
      // Since loops have a single latch, highest rank is easy to find.
      // If the loop has no latch, then it doesn't matter.
      Iterator = BlockToOrder.find(Latch);
    }
 
    assert(Iterator != BlockToOrder.end());
    result = std::max(result, Iterator->second.Rank + 1);
  }
 
  return result;
}
 
size_t PartialOrderingVisitor::visit(BasicBlock *BB, size_t Unused) {
  ToVisit.push(BB);
  Queued.insert(BB);
 
  size_t QueueIndex = 0;
  while (ToVisit.size() != 0) {
    BasicBlock *BB = ToVisit.front();
    ToVisit.pop();
 
    if (!CanBeVisited(BB)) {
      ToVisit.push(BB);
      if (QueueIndex >= ToVisit.size())
        llvm::report_fatal_error(
            "No valid candidate in the queue. Is the graph reducible?");
      QueueIndex++;
      continue;
    }
 
    QueueIndex = 0;
    size_t Rank = GetNodeRank(BB);
    OrderInfo Info = {Rank, BlockToOrder.size()};
    BlockToOrder.try_emplace(BB, Info);
 
    for (BasicBlock *S : successors(BB)) {
      if (Queued.count(S) != 0)
        continue;
      ToVisit.push(S);
      Queued.insert(S);
    }
  }
 
  return 0;
}
 
PartialOrderingVisitor::PartialOrderingVisitor(Function &F) {
  DT.recalculate(F);
  LI = LoopInfo(DT);
 
  visit(&*F.begin(), 0);
 
  Order.reserve(F.size());
  for (auto &[BB, Info] : BlockToOrder)
    Order.emplace_back(BB);
 
  llvm::sort(Order, [&](const auto &LHS, const auto &RHS) {
    return compare(LHS, RHS);
  });
}
 
bool PartialOrderingVisitor::compare(const BasicBlock *LHS,
                                     const BasicBlock *RHS) const {
  const OrderInfo &InfoLHS = BlockToOrder.at(const_cast<BasicBlock *>(LHS));
  const OrderInfo &InfoRHS = BlockToOrder.at(const_cast<BasicBlock *>(RHS));
  if (InfoLHS.Rank != InfoRHS.Rank)
    return InfoLHS.Rank < InfoRHS.Rank;
  return InfoLHS.TraversalIndex < InfoRHS.TraversalIndex;
}
 
void PartialOrderingVisitor::partialOrderVisit(
    BasicBlock &Start, std::function<bool(BasicBlock *)> Op) {
  SmallPtrSet<BasicBlock *, 0> Reachable = getReachableFrom(&Start);
  assert(BlockToOrder.count(&Start) != 0);
 
  // Skipping blocks with a rank inferior to |Start|'s rank.
  auto It = Order.begin();
  while (It != Order.end() && *It != &Start)
    ++It;
 
  // This is unexpected. Worst case |Start| is the last block,
  // so It should point to the last block, not past-end.
  assert(It != Order.end());
 
  // By default, there is no rank limit. Setting it to the maximum value.
  std::optional<size_t> EndRank = std::nullopt;
  for (; It != Order.end(); ++It) {
    if (EndRank.has_value() && BlockToOrder[*It].Rank > *EndRank)
      break;
 
    if (Reachable.count(*It) == 0) {
      continue;
    }
 
    if (!Op(*It)) {
      EndRank = BlockToOrder[*It].Rank;
    }
  }
}
 
bool sortBlocks(Function &F) {
  if (F.size() == 0)
    return false;
 
  bool Modified = false;
  std::vector<BasicBlock *> Order;
  Order.reserve(F.size());
 
  ReversePostOrderTraversal<Function *> RPOT(&F);
  llvm::append_range(Order, RPOT);
 
  assert(&*F.begin() == Order[0]);
  BasicBlock *LastBlock = &*F.begin();
  for (BasicBlock *BB : Order) {
    if (BB != LastBlock && &*LastBlock->getNextNode() != BB) {
      Modified = true;
      BB->moveAfter(LastBlock);
    }
    LastBlock = BB;
  }
 
  return Modified;
}
 
AllocaInst *createVariable(Function &F, Type *Type) {
  const DataLayout &DL = F.getDataLayout();
  return new AllocaInst(Type, DL.getAllocaAddrSpace(), nullptr, "reg",
                        F.begin()->getFirstInsertionPt());
}
 
Value *
createExitVariable(BasicBlock *BB,
                   const DenseMap<BasicBlock *, ConstantInt *> &TargetToValue) {
  auto *T = BB->getTerminator();
  if (isa<ReturnInst>(T))
    return nullptr;
  if (auto *BI = dyn_cast<UncondBrInst>(T))
    return TargetToValue.lookup(BI->getSuccessor());
 
  IRBuilder<> Builder(BB);
  Builder.SetInsertPoint(T);
 
  if (auto *BI = dyn_cast<CondBrInst>(T)) {
    Value *LHS = TargetToValue.lookup(BI->getSuccessor(0));
    Value *RHS = TargetToValue.lookup(BI->getSuccessor(1));
 
    if (LHS == nullptr || RHS == nullptr)
      return LHS == nullptr ? RHS : LHS;
    return Builder.CreateSelect(BI->getCondition(), LHS, RHS);
  }
 
  // TODO: add support for switch cases.
  llvm_unreachable("Unhandled terminator type.");
}
 
MachineInstr *getVRegDef(MachineRegisterInfo &MRI, Register Reg) {
  MachineInstr *MaybeDef = MRI.getVRegDef(Reg);
  if (MaybeDef && MaybeDef->getOpcode() == SPIRV::ASSIGN_TYPE)
    MaybeDef = MRI.getVRegDef(MaybeDef->getOperand(1).getReg());
  return MaybeDef;
}
 
static bool getVacantFunctionName(Module &M, std::string &Name) {
  // It's a bit of paranoia, but still we don't want to have even a chance that
  // the loop will work for too long.
  constexpr unsigned MaxIters = 1024;
  for (unsigned I = 0; I < MaxIters; ++I) {
    std::string OrdName = Name + Twine(I).str();
    if (!M.getFunction(OrdName)) {
      Name = std::move(OrdName);
      return true;
    }
  }
  return false;
}
 
// Assign SPIR-V type to the register. If the register has no valid assigned
// class, set register LLT type and class according to the SPIR-V type.
void setRegClassType(Register Reg, SPIRVTypeInst SpvType,
                     SPIRVGlobalRegistry *GR, MachineRegisterInfo *MRI,
                     const MachineFunction &MF, bool Force) {
  GR->assignSPIRVTypeToVReg(SpvType, Reg, MF);
  if (!MRI->getRegClassOrNull(Reg) || Force) {
    MRI->setRegClass(Reg, GR->getRegClass(SpvType));
    LLT RegType = GR->getRegType(SpvType);
    if (Force || !MRI->getType(Reg).isValid())
      MRI->setType(Reg, RegType);
  }
}
 
// Create a SPIR-V type, assign SPIR-V type to the register. If the register has
// no valid assigned class, set register LLT type and class according to the
// SPIR-V type.
void setRegClassType(Register Reg, const Type *Ty, SPIRVGlobalRegistry *GR,
                     MachineIRBuilder &MIRBuilder,
                     SPIRV::AccessQualifier::AccessQualifier AccessQual,
                     bool EmitIR, bool Force) {
  setRegClassType(Reg,
                  GR->getOrCreateSPIRVType(Ty, MIRBuilder, AccessQual, EmitIR),
                  GR, MIRBuilder.getMRI(), MIRBuilder.getMF(), Force);
}
 
// Create a virtual register and assign SPIR-V type to the register. Set
// register LLT type and class according to the SPIR-V type.
Register createVirtualRegister(SPIRVTypeInst SpvType, SPIRVGlobalRegistry *GR,
                               MachineRegisterInfo *MRI,
                               const MachineFunction &MF) {
  Register Reg = MRI->createVirtualRegister(GR->getRegClass(SpvType));
  MRI->setType(Reg, GR->getRegType(SpvType));
  GR->assignSPIRVTypeToVReg(SpvType, Reg, MF);
  return Reg;
}
 
// Create a virtual register and assign SPIR-V type to the register. Set
// register LLT type and class according to the SPIR-V type.
Register createVirtualRegister(SPIRVTypeInst SpvType, SPIRVGlobalRegistry *GR,
                               MachineIRBuilder &MIRBuilder) {
  return createVirtualRegister(SpvType, GR, MIRBuilder.getMRI(),
                               MIRBuilder.getMF());
}
 
// Create a SPIR-V type, virtual register and assign SPIR-V type to the
// register. Set register LLT type and class according to the SPIR-V type.
Register createVirtualRegister(
    const Type *Ty, SPIRVGlobalRegistry *GR, MachineIRBuilder &MIRBuilder,
    SPIRV::AccessQualifier::AccessQualifier AccessQual, bool EmitIR) {
  return createVirtualRegister(
      GR->getOrCreateSPIRVType(Ty, MIRBuilder, AccessQual, EmitIR), GR,
      MIRBuilder);
}
 
CallInst *buildIntrWithMD(Intrinsic::ID IntrID, ArrayRef<Type *> Types,
                          Value *Arg, Value *Arg2, ArrayRef<Constant *> Imms,
                          IRBuilder<> &B) {
  SmallVector<Value *, 4> Args;
  Args.push_back(Arg2);
  Args.push_back(buildMD(Arg));
  llvm::append_range(Args, Imms);
  return B.CreateIntrinsicWithoutFolding(IntrID, {Types}, Args);
}
 
// Return true if there is an opaque pointer type nested in the argument.
bool isNestedPointer(const Type *Ty) {
  if (Ty->isPtrOrPtrVectorTy())
    return true;
  if (const FunctionType *RefTy = dyn_cast<FunctionType>(Ty)) {
    if (isNestedPointer(RefTy->getReturnType()))
      return true;
    for (const Type *ArgTy : RefTy->params())
      if (isNestedPointer(ArgTy))
        return true;
    return false;
  }
  if (const ArrayType *RefTy = dyn_cast<ArrayType>(Ty))
    return isNestedPointer(RefTy->getElementType());
  return false;
}
 
bool isSpvIntrinsic(const Value *Arg) {
  if (const auto *II = dyn_cast<IntrinsicInst>(Arg))
    if (Function *F = II->getCalledFunction())
      if (F->getName().starts_with("llvm.spv."))
        return true;
  return false;
}
 
// Function to create continued instructions for SPV_INTEL_long_composites
// extension
SmallVector<MachineInstr *, 4>
createContinuedInstructions(MachineIRBuilder &MIRBuilder, unsigned Opcode,
                            unsigned MinWC, unsigned ContinuedOpcode,
                            ArrayRef<Register> Args, Register ReturnRegister,
                            Register TypeID) {
 
  SmallVector<MachineInstr *, 4> Instructions;
  constexpr unsigned MaxWordCount = UINT16_MAX;
  const size_t NumElements = Args.size();
  size_t MaxNumElements = MaxWordCount - MinWC;
  size_t SPIRVStructNumElements = NumElements;
 
  if (NumElements > MaxNumElements) {
    // Do adjustments for continued instructions which always had only one
    // minumum word count.
    SPIRVStructNumElements = MaxNumElements;
    MaxNumElements = MaxWordCount - 1;
  }
 
  auto MIB =
      MIRBuilder.buildInstr(Opcode).addDef(ReturnRegister).addUse(TypeID);
 
  for (size_t I = 0; I < SPIRVStructNumElements; ++I)
    MIB.addUse(Args[I]);
 
  Instructions.push_back(MIB.getInstr());
 
  for (size_t I = SPIRVStructNumElements; I < NumElements;
       I += MaxNumElements) {
    auto MIB = MIRBuilder.buildInstr(ContinuedOpcode);
    for (size_t J = I; J < std::min(I + MaxNumElements, NumElements); ++J)
      MIB.addUse(Args[J]);
    Instructions.push_back(MIB.getInstr());
  }
  return Instructions;
}
 
SmallVector<unsigned, 1>
getSpirvLoopControlOperandsFromLoopMetadata(MDNode *LoopMD) {
  unsigned LC = SPIRV::LoopControl::None;
  // Currently used only to store PartialCount value. Later when other
  // LoopControls are added - this map should be sorted before making
  // them loop_merge operands to satisfy 3.23. Loop Control requirements.
  std::vector<std::pair<unsigned, unsigned>> MaskToValueMap;
  if (findOptionMDForLoopID(LoopMD, "llvm.loop.unroll.disable")) {
    LC |= SPIRV::LoopControl::DontUnroll;
  } else {
    if (findOptionMDForLoopID(LoopMD, "llvm.loop.unroll.enable") ||
        findOptionMDForLoopID(LoopMD, "llvm.loop.unroll.full")) {
      LC |= SPIRV::LoopControl::Unroll;
    }
    if (MDNode *CountMD =
            findOptionMDForLoopID(LoopMD, "llvm.loop.unroll.count")) {
      if (auto *CI =
              mdconst::extract_or_null<ConstantInt>(CountMD->getOperand(1))) {
        unsigned Count = CI->getZExtValue();
        if (Count != 1) {
          LC |= SPIRV::LoopControl::PartialCount;
          MaskToValueMap.emplace_back(
              std::make_pair(SPIRV::LoopControl::PartialCount, Count));
        }
      }
    }
  }
  SmallVector<unsigned, 1> Result = {LC};
  for (auto &[Mask, Val] : MaskToValueMap)
    Result.push_back(Val);
  return Result;
}
 
SmallVector<unsigned, 1> getSpirvLoopControlOperandsFromLoopMetadata(Loop *L) {
  return getSpirvLoopControlOperandsFromLoopMetadata(L->getLoopID());
}
 
const std::set<unsigned> &getTypeFoldingSupportedOpcodes() {
  // clang-format off
  static const std::set<unsigned> TypeFoldingSupportingOpcs = {
    TargetOpcode::G_ADD,
    TargetOpcode::G_FADD,
    TargetOpcode::G_STRICT_FADD,
    TargetOpcode::G_SUB,
    TargetOpcode::G_FSUB,
    TargetOpcode::G_STRICT_FSUB,
    TargetOpcode::G_MUL,
    TargetOpcode::G_FMUL,
    TargetOpcode::G_STRICT_FMUL,
    TargetOpcode::G_SDIV,
    TargetOpcode::G_UDIV,
    TargetOpcode::G_FDIV,
    TargetOpcode::G_STRICT_FDIV,
    TargetOpcode::G_SREM,
    TargetOpcode::G_UREM,
    TargetOpcode::G_FREM,
    TargetOpcode::G_STRICT_FREM,
    TargetOpcode::G_FNEG,
    TargetOpcode::G_CONSTANT,
    TargetOpcode::G_FCONSTANT,
    TargetOpcode::G_AND,
    TargetOpcode::G_OR,
    TargetOpcode::G_XOR,
    TargetOpcode::G_SHL,
    TargetOpcode::G_ASHR,
    TargetOpcode::G_LSHR,
    TargetOpcode::G_SELECT,
    TargetOpcode::G_EXTRACT_VECTOR_ELT,
  };
  // clang-format on
  return TypeFoldingSupportingOpcs;
}
 
bool isTypeFoldingSupported(unsigned Opcode) {
  return getTypeFoldingSupportedOpcodes().count(Opcode) > 0;
}
 
// Traversing [g]MIR accounting for pseudo-instructions.
MachineInstr *passCopy(MachineInstr *Def, const MachineRegisterInfo *MRI) {
  return (Def->getOpcode() == SPIRV::ASSIGN_TYPE ||
          Def->getOpcode() == TargetOpcode::COPY)
             ? MRI->getVRegDef(Def->getOperand(1).getReg())
             : Def;
}
 
MachineInstr *getDef(const MachineOperand &MO, const MachineRegisterInfo *MRI) {
  if (MachineInstr *Def = MRI->getVRegDef(MO.getReg()))
    return passCopy(Def, MRI);
  return nullptr;
}
 
MachineInstr *getImm(const MachineOperand &MO, const MachineRegisterInfo *MRI) {
  if (MachineInstr *Def = getDef(MO, MRI)) {
    if (Def->getOpcode() == TargetOpcode::G_CONSTANT ||
        Def->getOpcode() == SPIRV::OpConstantI)
      return Def;
  }
  return nullptr;
}
 
int64_t foldImm(const MachineOperand &MO, const MachineRegisterInfo *MRI) {
  if (MachineInstr *Def = getImm(MO, MRI)) {
    if (Def->getOpcode() == SPIRV::OpConstantI)
      return Def->getOperand(2).getImm();
    if (Def->getOpcode() == TargetOpcode::G_CONSTANT)
      return Def->getOperand(1).getCImm()->getZExtValue();
  }
  llvm_unreachable("Unexpected integer constant pattern");
}
 
unsigned getArrayComponentCount(const MachineRegisterInfo *MRI,
                                const MachineInstr *ResType) {
  return foldImm(ResType->getOperand(2), MRI);
}
 
bool matchPeeledArrayPattern(const StructType *Ty, Type *&OriginalElementType,
                             uint64_t &TotalSize) {
  // An array of N padded structs is represented as {[N-1 x <{T, pad}>], T}.
  if (Ty->getStructNumElements() != 2)
    return false;
 
  Type *FirstElement = Ty->getStructElementType(0);
  Type *SecondElement = Ty->getStructElementType(1);
 
  if (!FirstElement->isArrayTy())
    return false;
 
  Type *ArrayElementType = FirstElement->getArrayElementType();
  if (!ArrayElementType->isStructTy() ||
      ArrayElementType->getStructNumElements() != 2)
    return false;
 
  Type *T_in_struct = ArrayElementType->getStructElementType(0);
  if (T_in_struct != SecondElement)
    return false;
 
  auto *Padding_in_struct =
      dyn_cast<TargetExtType>(ArrayElementType->getStructElementType(1));
  if (!Padding_in_struct || Padding_in_struct->getName() != "spirv.Padding")
    return false;
 
  const uint64_t ArraySize = FirstElement->getArrayNumElements();
  TotalSize = ArraySize + 1;
  OriginalElementType = ArrayElementType;
  return true;
}
 
Type *reconstitutePeeledArrayType(Type *Ty) {
  if (!Ty->isStructTy())
    return Ty;
 
  auto *STy = cast<StructType>(Ty);
  Type *OriginalElementType = nullptr;
  uint64_t TotalSize = 0;
  if (matchPeeledArrayPattern(STy, OriginalElementType, TotalSize)) {
    Type *ResultTy = ArrayType::get(
        reconstitutePeeledArrayType(OriginalElementType), TotalSize);
    return ResultTy;
  }
 
  SmallVector<Type *, 4> NewElementTypes;
  bool Changed = false;
  for (Type *ElementTy : STy->elements()) {
    Type *NewElementTy = reconstitutePeeledArrayType(ElementTy);
    if (NewElementTy != ElementTy)
      Changed = true;
    NewElementTypes.push_back(NewElementTy);
  }
 
  if (!Changed)
    return Ty;
 
  Type *ResultTy;
  if (STy->isLiteral())
    ResultTy =
        StructType::get(STy->getContext(), NewElementTypes, STy->isPacked());
  else {
    auto *NewTy = StructType::create(STy->getContext(), STy->getName());
    NewTy->setBody(NewElementTypes, STy->isPacked());
    ResultTy = NewTy;
  }
  return ResultTy;
}
 
std::optional<SPIRV::LinkageType::LinkageType>
getSpirvLinkageTypeFor(const SPIRVSubtarget &ST, const GlobalValue &GV) {
  if (GV.hasLocalLinkage())
    return std::nullopt;
 
  if (GV.isDeclarationForLinker()) {
    // Interface variables must not get Import linkage.
    if (const auto *GVar = dyn_cast<GlobalVariable>(&GV)) {
      auto SC = addressSpaceToStorageClass(GVar->getAddressSpace(), ST);
      if (SC == SPIRV::StorageClass::Input ||
          SC == SPIRV::StorageClass::Output ||
          SC == SPIRV::StorageClass::PushConstant)
        return std::nullopt;
    }
    return SPIRV::LinkageType::Import;
  }
 
  if (GV.hasHiddenVisibility())
    return std::nullopt;
 
  if (GV.hasLinkOnceODRLinkage() &&
      ST.canUseExtension(SPIRV::Extension::SPV_KHR_linkonce_odr))
    return SPIRV::LinkageType::LinkOnceODR;
 
  if (GV.hasWeakLinkage() &&
      ST.canUseExtension(SPIRV::Extension::SPV_AMD_weak_linkage))
    return SPIRV::LinkageType::WeakAMD;
 
  return SPIRV::LinkageType::Export;
}
 
Function *getOrCreateBackendServiceFunction(Module &M) {
  std::string ServiceFunName = SPIRV_BACKEND_SERVICE_FUN_NAME;
  if (!getVacantFunctionName(M, ServiceFunName))
    report_fatal_error(
        "cannot allocate a name for the internal service function");
  if (Function *SF = M.getFunction(ServiceFunName)) {
    if (SF->getInstructionCount() > 0)
      report_fatal_error(
          "Unexpected combination of global variables and function pointers");
    return SF;
  }
  Function *SF = Function::Create(
      FunctionType::get(Type::getVoidTy(M.getContext()), {}, false),
      GlobalValue::PrivateLinkage, ServiceFunName, M);
  SF->addFnAttr(SPIRV_BACKEND_SERVICE_FUN_NAME, "");
  return SF;
}
 
} // namespace llvm