SPIRVNonSemanticDebugHandler.cpp

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//===-- SPIRVNonSemanticDebugHandler.cpp - NSDI AsmPrinter handler -*- 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
//
//===----------------------------------------------------------------------===//
 
#include "SPIRVNonSemanticDebugHandler.h"
#include "MCTargetDesc/SPIRVMCTargetDesc.h"
#include "SPIRVSubtarget.h"
#include "SPIRVTargetMachine.h"
#include "SPIRVUtils.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVectorExtras.h"
#include "llvm/ADT/Twine.h"
#include "llvm/BinaryFormat/Dwarf.h"
#include "llvm/CodeGen/AsmPrinter.h"
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/IR/DebugInfo.h"
#include "llvm/IR/DebugInfoMetadata.h"
#include "llvm/IR/DebugProgramInstruction.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/IR/InstIterator.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Module.h"
#include "llvm/MC/MCInst.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/Path.h"
#include <cassert>
 
using namespace llvm;
 
namespace {
 
/// Look up \p Key in a register map and return its value, or std::nullopt when
/// the key is absent.
template <typename MapT>
static std::optional<MCRegister> lookupOptReg(const MapT &Map,
                                              typename MapT::key_type Key) {
  auto It = Map.find(Key);
  if (It == Map.end())
    return std::nullopt;
  assert(It->second.isValid() && "invalid register stored in map");
  return It->second;
}
 
enum : uint32_t {
  NSDIFlagIsProtected = 1u << 0,
  NSDIFlagIsPrivate = 1u << 1,
  NSDIFlagIsPublic = NSDIFlagIsPrivate | NSDIFlagIsProtected,
  NSDIFlagIsLocal = 1u << 2,
  NSDIFlagIsDefinition = 1u << 3,
  NSDIFlagFwdDecl = 1u << 4,
  NSDIFlagArtificial = 1u << 5,
  NSDIFlagExplicit = 1u << 6,
  NSDIFlagPrototyped = 1u << 7,
  NSDIFlagObjectPointer = 1u << 8,
  NSDIFlagStaticMember = 1u << 9,
  NSDIFlagIndirectVariable = 1u << 10,
  NSDIFlagLValueReference = 1u << 11,
  NSDIFlagRValueReference = 1u << 12,
  NSDIFlagIsOptimized = 1u << 13,
  NSDIFlagIsEnumClass = 1u << 14,
  NSDIFlagTypePassByValue = 1u << 15,
  NSDIFlagTypePassByReference = 1u << 16,
  NSDIFlagUnknownPhysicalLayout = 1u << 17,
};
 
static uint32_t mapDIFlagsToNonSemantic(DINode::DIFlags DFlags) {
  uint32_t Flags = 0;
  if ((DFlags & DINode::FlagAccessibility) == DINode::FlagPublic)
    Flags |= NSDIFlagIsPublic;
  if ((DFlags & DINode::FlagAccessibility) == DINode::FlagProtected)
    Flags |= NSDIFlagIsProtected;
  if ((DFlags & DINode::FlagAccessibility) == DINode::FlagPrivate)
    Flags |= NSDIFlagIsPrivate;
  if (DFlags & DINode::FlagFwdDecl)
    Flags |= NSDIFlagFwdDecl;
  if (DFlags & DINode::FlagArtificial)
    Flags |= NSDIFlagArtificial;
  if (DFlags & DINode::FlagExplicit)
    Flags |= NSDIFlagExplicit;
  if (DFlags & DINode::FlagPrototyped)
    Flags |= NSDIFlagPrototyped;
  if (DFlags & DINode::FlagObjectPointer)
    Flags |= NSDIFlagObjectPointer;
  if (DFlags & DINode::FlagStaticMember)
    Flags |= NSDIFlagStaticMember;
  if (DFlags & DINode::FlagLValueReference)
    Flags |= NSDIFlagLValueReference;
  if (DFlags & DINode::FlagRValueReference)
    Flags |= NSDIFlagRValueReference;
  if (DFlags & DINode::FlagTypePassByValue)
    Flags |= NSDIFlagTypePassByValue;
  if (DFlags & DINode::FlagTypePassByReference)
    Flags |= NSDIFlagTypePassByReference;
  if (DFlags & DINode::FlagEnumClass)
    Flags |= NSDIFlagIsEnumClass;
  return Flags;
}
 
static uint32_t transDebugFlags(const DINode *DN) {
  uint32_t Flags = 0;
  if (const auto *GV = dyn_cast<DIGlobalVariable>(DN)) {
    if (GV->isLocalToUnit())
      Flags |= NSDIFlagIsLocal;
    if (GV->isDefinition())
      Flags |= NSDIFlagIsDefinition;
  }
  if (const auto *SP = dyn_cast<DISubprogram>(DN)) {
    if (SP->isLocalToUnit())
      Flags |= NSDIFlagIsLocal;
    if (SP->isOptimized())
      Flags |= NSDIFlagIsOptimized;
    if (SP->isDefinition())
      Flags |= NSDIFlagIsDefinition;
    Flags |= mapDIFlagsToNonSemantic(SP->getFlags());
  }
  if (DN->getTag() == dwarf::DW_TAG_reference_type)
    Flags |= NSDIFlagLValueReference;
  if (DN->getTag() == dwarf::DW_TAG_rvalue_reference_type)
    Flags |= NSDIFlagRValueReference;
  if (const auto *Ty = dyn_cast<DIType>(DN))
    Flags |= mapDIFlagsToNonSemantic(Ty->getFlags());
  if (const auto *LV = dyn_cast<DILocalVariable>(DN))
    Flags |= mapDIFlagsToNonSemantic(LV->getFlags());
  return Flags;
}
 
// Map a DWARF composite tag to a NonSemantic.Shader.DebugInfo Composite Type
// value: Class 0, Structure 1, Union 2.
static uint32_t mapCompositeTypeTag(unsigned Tag) {
  switch (Tag) {
  case dwarf::DW_TAG_class_type:
    return 0;
  case dwarf::DW_TAG_structure_type:
    return 1;
  case dwarf::DW_TAG_union_type:
    return 2;
  default:
    reportFatalInternalError("unexpected DWARF composite tag " + Twine(Tag) +
                             ". Expecting 0, 1 or 2");
  }
}
 
static const MachineInstr *
findLastFunctionOpVariableDeclaration(const MachineFunction &MF,
                                      SPIRV::ModuleAnalysisInfo &MAI) {
 
  // We iterate over the instructions to find the last OpVariable instruction if
  // any. The following SPIRV rule is used to terminate the traversal earlier:
  // SPIR-V 2.16.1, Function Structure: "All OpVariable instructions in a
  // function must be in the first block in the function. These instructions,
  // together with any intermixed OpLine and OpNoLine instructions, must be the
  // first instructions in that block."
  const MachineInstr *LastOpVariable = nullptr;
  bool SeenOpVariable = false;
  for (const MachineInstr &MI : MF.front()) {
    if (MI.getOpcode() == SPIRV::OpVariable) {
      SeenOpVariable = true;
      if (!MAI.getSkipEmission(&MI))
        LastOpVariable = &MI;
      continue;
    }
 
    bool CanInterleaveWithOpVariable =
        MI.getOpcode() == SPIRV::OpLine || MI.getOpcode() == SPIRV::OpNoLine;
    if (SeenOpVariable && !CanInterleaveWithOpVariable &&
        !MAI.getSkipEmission(&MI))
      break;
  }
  return LastOpVariable;
}
 
} // namespace
 
SPIRVNonSemanticDebugHandler::SPIRVNonSemanticDebugHandler(AsmPrinter &AP)
    : DebugHandlerBase(&AP),
      CLOpts(static_cast<const SPIRVTargetMachine &>(AP.TM).getCLOpts()) {}
 
// Map DWARF source language codes to NonSemantic.Shader.DebugInfo.100 source
// language codes. Values are from the SourceLanguage enum in the
// NonSemantic.Shader.DebugInfo.100 specification, section 4.3.
unsigned SPIRVNonSemanticDebugHandler::toNSDISrcLang(unsigned DwarfSrcLang) {
  switch (DwarfSrcLang) {
  case dwarf::DW_LANG_OpenCL:
    return 3; // OpenCL_C
  case dwarf::DW_LANG_OpenCL_CPP:
    return 4; // OpenCL_CPP
  case dwarf::DW_LANG_CPP_for_OpenCL:
    return 6; // CPP_for_OpenCL
  case dwarf::DW_LANG_GLSL:
    return 2; // GLSL
  case dwarf::DW_LANG_HLSL:
    return 5; // HLSL
  case dwarf::DW_LANG_SYCL:
    return 7; // SYCL
  case dwarf::DW_LANG_Zig:
    return 12; // Zig
  default:
    return 0; // Unknown
  }
}
 
static bool isBooleanType(const DIBasicType *BT) {
  return BT->getEncoding() == dwarf::DW_ATE_boolean;
}
 
// \p Value truncated to the width of \p BT, or 0 or 1 for a boolean.
static uint64_t constantBits(uint64_t Value, const DIBasicType *BT) {
  // A boolean is one of two values and a DIBasicType may give it no size, so
  // masking to its width would turn every true into a false.
  if (isBooleanType(BT))
    return Value != 0;
  unsigned Width = BT->getSizeInBits();
  return Width >= 64 ? Value : Value & ((uint64_t(1) << Width) - 1);
}
 
// \p Value truncated to the width of \p BT. APInt::getZExtValue() asserts
// above 64 bits, so the truncation comes first.
static uint64_t constantBits(const APInt &Value, const DIBasicType *BT) {
  unsigned Width = isBooleanType(BT) ? 1 : BT->getSizeInBits();
  return constantBits(Value.getActiveBits() > 64
                          ? Value.trunc(std::min(Width, 64u)).getZExtValue()
                          : Value.getZExtValue(),
                      BT);
}
 
// The DIBasicType that \p Ty resolves to through any typedefs, or null.
static const DIBasicType *stripToScalarType(const DIType *Ty) {
  // A cv-qualified type gets no DebugType, so its variable has no
  // DebugLocalVariable and its records are dropped.
  //
  // Since visitDIDerivedType accepts a cyclic typedef chain, this stops once it
  // reaches an already seen type.
  SmallPtrSet<const DIDerivedType *, 4> Seen;
  while (const auto *DT = dyn_cast_or_null<DIDerivedType>(Ty)) {
    if (DT->getTag() != dwarf::DW_TAG_typedef || !Seen.insert(DT).second)
      return nullptr;
    Ty = DT->getBaseType();
  }
 
  const auto *BT = dyn_cast_or_null<DIBasicType>(Ty);
  if (!BT)
    return nullptr;
 
  // OpTypeBool carries no width, so a boolean of any size is accepted.
  if (isBooleanType(BT))
    return BT;
 
  unsigned Size = BT->getSizeInBits();
  switch (BT->getEncoding()) {
  case dwarf::DW_ATE_signed:
  case dwarf::DW_ATE_unsigned:
  case dwarf::DW_ATE_signed_char:
  case dwarf::DW_ATE_unsigned_char:
    return Size == 8 || Size == 16 || Size == 32 || Size == 64 ? BT : nullptr;
  case dwarf::DW_ATE_float:
    // SPIR-V has no 8-bit float.
    return Size == 16 || Size == 32 || Size == 64 ? BT : nullptr;
  default:
    return nullptr;
  }
}
 
// Collect distinct DILocations and DILocalVariables from LLVM IR.
//
// DILocations come from instruction debug locations and from the debug records
// attached to them. DebugLine pre-emission and MIR lookups assume every
// machine-instruction debug location already appeared here; a codegen-only
// location would not be collected and emission will be skipped.
//
// DILocalVariables come from the DbgVariableRecords attached to instructions
// and from the retained nodes of each DISubprogram. Retained nodes are needed
// because a variable with no remaining debug record (e.g. optimized away) must
// still get a DebugLocalVariable.
static void collectDebugLocationsAndLocalVariables(
    const Module &M, SetVector<const DILocation *> &Locations,
    SetVector<const DILocalVariable *> &LVs) {
  for (const Function &F : M) {
    const DISubprogram *SP = F.getSubprogram();
    if (!SP)
      continue;
    for (const MDNode *N : SP->getRetainedNodes())
      if (const auto *LV = dyn_cast_or_null<DILocalVariable>(N))
        LVs.insert(LV);
    for (const Instruction &I : instructions(F)) {
      if (const DILocation *DL = I.getDebugLoc().get())
        Locations.insert(DL);
      for (DbgRecord &DR : I.getDbgRecordRange()) {
        if (const DILocation *DL = DR.getDebugLoc().get())
          Locations.insert(DL);
        if (const auto *DVR = dyn_cast<DbgVariableRecord>(&DR))
          if (const DILocalVariable *LV = DVR->getVariable())
            LVs.insert(LV);
      }
    }
  }
}
 
// Insert \p S and its enclosing DILexicalBlock/DINamespace/DILexicalBlockFile
// chain into \p Out, parent before child, so single-pass emission never needs
// a forward reference for the Parent operand.
static void collectLexicalBlockChain(const DIScope *S,
                                     SetVector<const DIScope *> &Out) {
  // Walk up child-first, then insert in reverse to get parents in first.
  SmallVector<const DIScope *, 8> Chain;
  while (S && !Out.contains(S) &&
         isa<DILexicalBlock, DINamespace, DILexicalBlockFile>(S)) {
    Chain.push_back(S);
    S = S->getScope();
  }
  Out.insert(Chain.rbegin(), Chain.rend());
}
 
void SPIRVNonSemanticDebugHandler::beginModule(Module *M) {
  // The base class sets Asm = nullptr when the module has no compile units,
  // and initializes lexical scope tracking otherwise.
  DebugHandlerBase::beginModule(M);
 
  if (!Asm)
    return;
 
  CompileUnits.clear();
  DebugTypes.clear();
  EnumCompileUnits.clear();
  Subprograms.clear();
  UniqueDebugLocations.clear();
  GlobalVariableDebugInfoMap.clear();
  LocalVariables.clear();
  DebugLocalVariableRegs.clear();
  DebugExpressionRegs.clear();
  LexicalBlocks.clear();
  DebugScopeRegs.clear();
  ScopesInProgress.clear();
  HasRelaxedExtInst = false;
  FailedScopes.clear();
  DebugInlinedAtRegs.clear();
  ScopeToPathOpStringReg.clear();
  DebugSourceRegByFileStr.clear();
  OpStringContentCache.clear();
  ScalarTypeCache.clear();
  ScalarConstantCache.clear();
  ConstantValueRegs.clear();
  DebugOperationCache.clear();
  DebugExpressionCache.clear();
  ModuleScopeIds.clear();
  GlobalDIEmitted = false;
  GlobalNSDIEnabled = false;
  CurrentMAI = nullptr;
#ifndef NDEBUG
  NonSemanticOpStringsSectionEmitted = false;
#endif
  CachedDebugInfoNoneReg = MCRegister();
  CachedEmptyStringReg = MCRegister();
  CachedOpTypeVoidReg = MCRegister();
  CachedOpTypeInt32Reg = MCRegister();
 
  // Collect compile-unit info: file paths and source languages.
  for (const DICompileUnit *CU : M->debug_compile_units()) {
    const DIFile *File = CU->getFile();
    CompileUnitInfo Info;
    Info.TheCU = CU;
    if (sys::path::is_absolute(File->getFilename()))
      Info.FilePath = File->getFilename();
    else
      sys::path::append(Info.FilePath, File->getDirectory(),
                        File->getFilename());
    // getName() returns the language code regardless of whether the name is
    // versioned. getUnversionedName() would assert on versioned names.
    Info.SpirvSourceLanguage = toNSDISrcLang(CU->getSourceLanguage().getName());
    CompileUnits.push_back(std::move(Info));
    for (const DICompositeType *ET : CU->getEnumTypes())
      EnumCompileUnits.try_emplace(ET, CU);
  }
 
  // Collect DWARF version from module flags. For CodeView modules there is no
  // "Dwarf Version" flag; DwarfVersion remains 0, which is the correct value
  // for the DebugCompilationUnit DWARF Version operand in that case.
  if (const NamedMDNode *Flags = M->getNamedMetadata("llvm.module.flags")) {
    for (const auto *Op : Flags->operands()) {
      const MDOperand &NameOp = Op->getOperand(1);
      if (NameOp.equalsStr("Dwarf Version"))
        DwarfVersion =
            cast<ConstantInt>(
                cast<ConstantAsMetadata>(Op->getOperand(2))->getValue())
                ->getSExtValue();
    }
  }
 
  // Find all debug info types that may be referenced by NSDI instructions.
  // Member types are not roots: each one is emitted only from its composite.
  DebugInfoFinder Finder;
  Finder.processModule(*M);
  copy_if(Finder.types(), std::back_inserter(DebugTypes), [](const DIType *Ty) {
    return Ty->getTag() != dwarf::DW_TAG_member;
  });
 
  Subprograms.assign(Finder.subprograms().begin(), Finder.subprograms().end());
 
  // Walk LLVM globals to map each DIGlobalVariable to its llvm::GlobalVariable.
  DenseMap<const DIGlobalVariable *, const GlobalVariable *> DIGVToLLVMGV;
  for (const GlobalVariable &G : M->globals()) {
    SmallVector<DIGlobalVariableExpression *> GVEs;
    G.getDebugInfo(GVEs);
    for (DIGlobalVariableExpression *GVE : GVEs) {
      if (const DIGlobalVariable *GV = GVE->getVariable()) {
        DIGVToLLVMGV.try_emplace(GV, &G);
      }
    }
  }
 
  for (const DIGlobalVariableExpression *GVE : Finder.global_variables()) {
    const DIGlobalVariable *GV = GVE->getVariable();
    const DIExpression *Expr = GVE->getExpression();
    GlobalVariableDebugInfoMap.try_emplace(
        GV, GlobalVariableDebugInfo{Expr, DIGVToLLVMGV.lookup(GV)});
  }
 
  collectDebugLocationsAndLocalVariables(*M, UniqueDebugLocations,
                                         LocalVariables);
 
  // DILexicalBlock and DINamespace scopes are lowered to DebugLexicalBlock.
  // DILexicalBlockFile is lowered to DebugLexicalBlockDiscriminator.
  // Collect them in parent-before-child order so they can be emitted in a
  // single pass.
  for (const DIScope *S : Finder.scopes())
    collectLexicalBlockChain(S, LexicalBlocks);
}
 
// The emitted SPIR-V id of \p MI, or an invalid register when \p MI defines
// no result.
static MCRegister getResultId(const MachineInstr &MI,
                              SPIRV::ModuleAnalysisInfo &MAI) {
  if (MI.getNumOperands() == 0 || !MI.getOperand(0).isReg() ||
      !MI.getOperand(0).isDef())
    return MCRegister();
  return MAI.getRegisterAlias(MI.getMF(), MI.getOperand(0).getReg());
}
 
void SPIRVNonSemanticDebugHandler::prepareModuleOutput(
    const SPIRVSubtarget &ST, SPIRV::ModuleAnalysisInfo &MAI) {
  if (CompileUnits.empty())
    return;
  if (!ST.canUseExtension(SPIRV::Extension::SPV_KHR_non_semantic_info))
    return;
 
  // Add the extension to requirements so OpExtension is output.
  MAI.Reqs.addExtension(SPIRV::Extension::SPV_KHR_non_semantic_info);
 
  HasRelaxedExtInst =
      CLOpts.debug_scope_forward_refs &&
      ST.canUseExtension(
          SPIRV::Extension::SPV_KHR_relaxed_extended_instruction);
  if (HasRelaxedExtInst)
    MAI.Reqs.addExtension(
        SPIRV::Extension::SPV_KHR_relaxed_extended_instruction);
 
  // Add the NonSemantic.Shader.DebugInfo.100 entry to ExtInstSetMap so that
  // outputOpExtInstImports() emits the OpExtInstImport instruction. Allocate a
  // fresh result ID for it now; the same ID is used in emitExtInst() operands.
  if (!MAI.ExtInstSetMap.count(NSSet))
    MAI.ExtInstSetMap[NSSet] = MAI.getNextIDRegister();
 
  for (const MachineInstr *MI : MAI.getMSInstrs(SPIRV::MB_TypeConstVars)) {
    if (MCRegister Id = getResultId(*MI, MAI))
      ModuleScopeIds.insert(Id);
  }
}
 
void SPIRVNonSemanticDebugHandler::emitMCInst(MCInst &Inst) {
  Asm->OutStreamer->emitInstruction(Inst, Asm->getSubtargetInfo());
}
 
MCRegister
SPIRVNonSemanticDebugHandler::emitOpString(StringRef S,
                                           SPIRV::ModuleAnalysisInfo &MAI) {
  MCRegister Reg = MAI.getNextIDRegister();
  MCInst Inst;
  Inst.setOpcode(SPIRV::OpString);
  Inst.addOperand(MCOperand::createReg(Reg));
  addStringImm(S, Inst);
  emitMCInst(Inst);
  return Reg;
}
 
MCRegister SPIRVNonSemanticDebugHandler::emitOpStringIfNew(
    StringRef S, SPIRV::ModuleAnalysisInfo &MAI) {
#ifndef NDEBUG
  assert(!NonSemanticOpStringsSectionEmitted &&
         "emitOpStringIfNew is only valid while emitting SPIR-V section 7");
#endif
  auto [It, Inserted] = OpStringContentCache.try_emplace(S, MCRegister());
  if (Inserted)
    It->second = emitOpString(S, MAI);
 
  return It->second;
}
 
MCRegister SPIRVNonSemanticDebugHandler::getCachedOpStringReg(StringRef S) {
#ifndef NDEBUG
  assert(NonSemanticOpStringsSectionEmitted &&
         "getCachedOpStringReg requires emitNonSemanticDebugStrings() first");
#endif
  auto It = OpStringContentCache.find(S);
  assert(It != OpStringContentCache.end() &&
         "NSDI OpString missing from cache; emitNonSemanticDebugStrings must "
         "cache every string used in section 10");
  return It->second;
}
 
MCRegister SPIRVNonSemanticDebugHandler::emitAndCacheScopePathOpStringReg(
    const DIScope *Scope, SPIRV::ModuleAnalysisInfo &MAI) {
  auto [It, Inserted] = ScopeToPathOpStringReg.try_emplace(Scope, MCRegister());
  if (Inserted)
    It->second = emitOpStringIfNew(getDebugFullPath(Scope), MAI);
  return It->second;
}
 
MCRegister SPIRVNonSemanticDebugHandler::getCachedScopePathOpStringReg(
    const DIScope *Scope, bool UseEmptyPathIfNullScope) {
  if (!Scope) {
    assert(UseEmptyPathIfNullScope &&
           "null scope path lookup requires UseEmptyPathIfNullScope");
    assert(CachedEmptyStringReg.isValid() &&
           "empty path OpString must be cached in emitNonSemanticDebugStrings");
    return CachedEmptyStringReg;
  }
  auto It = ScopeToPathOpStringReg.find(Scope);
  assert(It != ScopeToPathOpStringReg.end() &&
         "path OpString must be cached in emitNonSemanticDebugStrings");
  MCRegister FileStrReg = It->second;
  assert(FileStrReg.isValid() && "path OpString id must be valid once cached");
  return FileStrReg;
}
 
MCRegister SPIRVNonSemanticDebugHandler::emitOpConstantI32(
    uint32_t Value, MCRegister I32TypeReg, SPIRV::ModuleAnalysisInfo &MAI) {
  return findOrEmitConstant(SPIRV::OpConstantI, I32TypeReg, Value,
                            /*Width=*/32, MAI);
}
 
bool SPIRVNonSemanticDebugHandler::markForwardReferencedOperands(
    ArrayRef<MCRegister> Operands) {
  bool HasForwardRef = false;
  for (auto &Entry : ScopesInProgress) {
    InProgressScope &InProgress = Entry.second;
    assert(InProgress.Id.isValid() &&
           "in-progress scope must have a reserved id");
    if (!is_contained(Operands, InProgress.Id))
      continue;
    InProgress.ForwardReferenced = true;
    HasForwardRef = true;
  }
  return HasForwardRef;
}
 
MCRegister SPIRVNonSemanticDebugHandler::emitExtInst(
    SPIRV::NonSemanticExtInst::NonSemanticExtInst Opcode,
    MCRegister VoidTypeReg, MCRegister ExtInstSetReg,
    ArrayRef<MCRegister> Operands, SPIRV::ModuleAnalysisInfo &MAI,
    std::optional<MCRegister> ResultReg) {
  assert((!ResultReg || ResultReg->isValid()) &&
         "ResultReg must be a valid id when provided");
  MCRegister Reg = ResultReg ? *ResultReg : MAI.getNextIDRegister();
 
  // An operand that is still an in-progress scope id is a forward reference.
  // Tag the instruction with OpExtInstWithForwardRefsKHR and remember the id:
  // if that scope later fails, the id still needs a definition.
  bool HasForwardRef =
      HasRelaxedExtInst && markForwardReferencedOperands(Operands);
 
  MCInst Inst;
  Inst.setOpcode(HasForwardRef ? SPIRV::OpExtInstWithForwardRefsKHR
                               : SPIRV::OpExtInst);
  Inst.addOperand(MCOperand::createReg(Reg));
  Inst.addOperand(MCOperand::createReg(VoidTypeReg));
  Inst.addOperand(MCOperand::createReg(ExtInstSetReg));
  Inst.addOperand(MCOperand::createImm(static_cast<int64_t>(Opcode)));
  for (MCRegister R : Operands)
    Inst.addOperand(MCOperand::createReg(R));
  emitMCInst(Inst);
  return Reg;
}
 
MCRegister SPIRVNonSemanticDebugHandler::getOrEmitOpTypeVoidReg(
    SPIRV::ModuleAnalysisInfo &MAI) {
  if (!CachedOpTypeVoidReg.isValid())
    CachedOpTypeVoidReg = findOrEmitOpTypeVoid(MAI);
  return CachedOpTypeVoidReg;
}
 
MCRegister SPIRVNonSemanticDebugHandler::getOrEmitOpTypeInt32Reg(
    SPIRV::ModuleAnalysisInfo &MAI) {
  if (!CachedOpTypeInt32Reg.isValid())
    CachedOpTypeInt32Reg = findOrEmitOpTypeInt32(MAI);
  return CachedOpTypeInt32Reg;
}
 
MCRegister SPIRVNonSemanticDebugHandler::findOrEmitOpTypeVoid(
    SPIRV::ModuleAnalysisInfo &MAI) {
  for (const MachineInstr *MI : MAI.getMSInstrs(SPIRV::MB_TypeConstVars)) {
    if (MI->getOpcode() == SPIRV::OpTypeVoid)
      return MAI.getRegisterAlias(MI->getMF(), MI->getOperand(0).getReg());
  }
  MCRegister Reg = MAI.getNextIDRegister();
  MCInst Inst;
  Inst.setOpcode(SPIRV::OpTypeVoid);
  Inst.addOperand(MCOperand::createReg(Reg));
  emitMCInst(Inst);
  return Reg;
}
 
// Whether declaring \p BT's SPIR-V type would require a capability. The type
// width determines the requirement: Int8, Int16, Int64, Float16 and Float64 in
// SPIRVModuleAnalysis::collectReqs(). A boolean and a 32-bit scalar are free.
static bool scalarTypeNeedsCapability(const DIBasicType *BT) {
  if (isBooleanType(BT))
    return false;
  unsigned Width = BT->getSizeInBits();
  return Width != 32;
}
 
MCRegister SPIRVNonSemanticDebugHandler::findOrEmitScalarType(
    const DIBasicType *BT, SPIRV::ModuleAnalysisInfo &MAI) {
  bool IsBool = isBooleanType(BT);
  bool IsFloat = BT->getEncoding() == dwarf::DW_ATE_float;
  unsigned Opcode = IsBool    ? SPIRV::OpTypeBool
                    : IsFloat ? SPIRV::OpTypeFloat
                              : SPIRV::OpTypeInt;
  // Two DIBasicTypes can describe one SPIR-V type, and OpTypeBool has no
  // width, so the key is the opcode and the width rather than the node.
  int64_t Width = IsBool ? 0 : BT->getSizeInBits();
 
  // OpTypeInt 32 0 is already owned by getOrEmitOpTypeInt32Reg(), which every
  // line and column constant needs. Declaring a second one is a duplicate type
  // declaration, which the validator rejects.
  if (Opcode == SPIRV::OpTypeInt && Width == 32)
    return getOrEmitOpTypeInt32Reg(MAI);
 
  auto [CacheIt, Inserted] =
      ScalarTypeCache.try_emplace({Opcode, Width}, MCRegister());
  if (!Inserted)
    return CacheIt->second;
 
  // The backend writes every integer type with signedness 0, so a signed and
  // an unsigned DIBasicType of the same width share one OpTypeInt.
  for (const MachineInstr *MI : MAI.getMSInstrs(SPIRV::MB_TypeConstVars)) {
    if (MI->getOpcode() != Opcode)
      continue;
    if (IsBool || (MI->getOperand(1).getImm() == Width &&
                   (IsFloat || MI->getOperand(2).getImm() == 0))) {
      CacheIt->second =
          MAI.getRegisterAlias(MI->getMF(), MI->getOperand(0).getReg());
      return CacheIt->second;
    }
  }
 
  // A non-semantic instruction "has no semantic impact, and can be safely
  // removed from the module", so debug info must leave the module's
  // requirements alone. Declaring OpTypeInt 64 forces Int64, which Vulkan ties
  // to a device feature, so this returns nothing if the type requires a new
  // capability.
  if (scalarTypeNeedsCapability(BT))
    return MCRegister();
 
  MCRegister Reg = MAI.getNextIDRegister();
  MCInst Inst;
  Inst.setOpcode(Opcode);
  Inst.addOperand(MCOperand::createReg(Reg));
  if (!IsBool) {
    Inst.addOperand(MCOperand::createImm(Width));
    if (!IsFloat)
      Inst.addOperand(MCOperand::createImm(0));
  }
  emitMCInst(Inst);
  CacheIt->second = Reg;
  return Reg;
}
 
// Whether the constant \p MI holds \p Value, read as two words when \p IsWide.
static bool constantHasValue(const MachineInstr &MI, uint64_t Value,
                             bool IsWide) {
  unsigned Words = IsWide ? 2 : 1;
  if (MI.getNumOperands() < 2 + Words)
    return false;
  uint64_t Found = 0;
  for (unsigned I = 0; I < Words; ++I) {
    if (!MI.getOperand(2 + I).isImm())
      return false;
    Found |= static_cast<uint64_t>(
                 static_cast<uint32_t>(MI.getOperand(2 + I).getImm()))
             << (32 * I);
  }
  return Found == Value;
}
 
MCRegister SPIRVNonSemanticDebugHandler::findModuleConstant(
    unsigned Opcode, MCRegister TypeReg, uint64_t Value, bool IsBool,
    bool IsWide, SPIRV::ModuleAnalysisInfo &MAI) {
  for (const MachineInstr *MI : MAI.getMSInstrs(SPIRV::MB_TypeConstVars)) {
    if (MI->getOpcode() != Opcode || MI->getNumOperands() < 2)
      continue;
    if (MAI.getRegisterAlias(MI->getMF(), MI->getOperand(1).getReg()) !=
        TypeReg)
      continue;
    // A boolean holds its value in its opcode, so there is nothing to compare.
    if (!IsBool && !constantHasValue(*MI, Value, IsWide))
      continue;
    return MAI.getRegisterAlias(MI->getMF(), MI->getOperand(0).getReg());
  }
  return MCRegister();
}
 
// \p Width is 0 for a boolean, whose value lives in \p Opcode.
MCRegister SPIRVNonSemanticDebugHandler::findOrEmitConstant(
    unsigned Opcode, MCRegister TypeReg, uint64_t Value, unsigned Width,
    SPIRV::ModuleAnalysisInfo &MAI) {
  bool IsBool = Width == 0;
  bool IsWide = Width == 64;
 
  auto [CacheIt, Inserted] =
      ScalarConstantCache.try_emplace({TypeReg.id(), Value}, MCRegister());
  if (!Inserted)
    return CacheIt->second;
 
  MCRegister Found =
      findModuleConstant(Opcode, TypeReg, Value, IsBool, IsWide, MAI);
  if (Found.isValid()) {
    CacheIt->second = Found;
    return Found;
  }
 
  MCRegister Reg = MAI.getNextIDRegister();
  MCInst Inst;
  Inst.setOpcode(Opcode);
  Inst.addOperand(MCOperand::createReg(Reg));
  Inst.addOperand(MCOperand::createReg(TypeReg));
  if (!IsBool) {
    // OpConstant's Value is "the bit pattern for the constant. Types 32 bits
    // wide or smaller take one word. Larger types take multiple words, with
    // low-order words appearing first" (SPIR-V specification, OpConstant).
    Inst.addOperand(MCOperand::createImm(static_cast<int64_t>(Lo_32(Value))));
    if (IsWide) {
      Inst.addOperand(MCOperand::createImm(static_cast<int64_t>(Hi_32(Value))));
    } else if (Width == 16) {
      // A 16-bit float takes one word, the same as a 32-bit one, so the text
      // printer needs the width to pick the right APFloat semantics.
      Inst.setFlags(SPIRV::INST_PRINTER_WIDTH16);
    }
  }
  emitMCInst(Inst);
  CacheIt->second = Reg;
  return Reg;
}
 
MCRegister SPIRVNonSemanticDebugHandler::findOrEmitScalarConstant(
    const DIBasicType *BT, uint64_t Value, SPIRV::ModuleAnalysisInfo &MAI) {
  MCRegister TypeReg = findOrEmitScalarType(BT, MAI);
  if (!TypeReg.isValid())
    return MCRegister();
 
  bool IsBool = isBooleanType(BT);
  bool IsFloat = BT->getEncoding() == dwarf::DW_ATE_float;
  unsigned Opcode =
      IsBool    ? (Value ? SPIRV::OpConstantTrue : SPIRV::OpConstantFalse)
      : IsFloat ? SPIRV::OpConstantF
                : SPIRV::OpConstantI;
  return findOrEmitConstant(Opcode, TypeReg, Value,
                            IsBool ? 0 : BT->getSizeInBits(), MAI);
}
 
MCRegister SPIRVNonSemanticDebugHandler::findOrEmitOpTypeInt32(
    SPIRV::ModuleAnalysisInfo &MAI) {
  for (const MachineInstr *MI : MAI.getMSInstrs(SPIRV::MB_TypeConstVars)) {
    if (MI->getOpcode() == SPIRV::OpTypeInt &&
        MI->getOperand(1).getImm() == 32 && MI->getOperand(2).getImm() == 0)
      return MAI.getRegisterAlias(MI->getMF(), MI->getOperand(0).getReg());
  }
  MCRegister Reg = MAI.getNextIDRegister();
  MCInst Inst;
  Inst.setOpcode(SPIRV::OpTypeInt);
  Inst.addOperand(MCOperand::createReg(Reg));
  Inst.addOperand(MCOperand::createImm(32)); // width
  Inst.addOperand(MCOperand::createImm(0));  // signedness (unsigned)
  emitMCInst(Inst);
  return Reg;
}
 
// Each node emits its dependencies first. E.g. for `void f() { struct L; }`,
// node L emits f, then L. Entering a scope reserves its result id. For
// `struct S { S *p; }`, S* is a back edge. When forward references are
// enabled, that id is used with OpExtInstWithForwardRefsKHR, and a later
// failure defines it as DebugInfoNone only when an emitted instruction already
// named it. Otherwise the edge is dropped and the reserved id stays unused.
auto SPIRVNonSemanticDebugHandler::getOrCreateDebugScope(const DIScope *S)
    -> EmitResult<MCRegister> {
  if (!S || FailedScopes.contains(S))
    return EmitResult<MCRegister>::unsupported();
  if (auto Reg = lookupOptReg(DebugScopeRegs, S))
    return EmitResult<MCRegister>::emitted(*Reg);
 
  // Mark the scope node as in progress while its dependencies are
  // resolved/emitted.
  auto [InProgressIt, FirstVisit] = ScopesInProgress.try_emplace(S);
  if (!FirstVisit) { // We hit a back edge, it is not the first insertion.
    if (!HasRelaxedExtInst)
      return EmitResult<MCRegister>::inProgress(); // No support for forward
                                                   // refs.
    // Use the reserved id for the back edge when forward references are
    // supported.
    MCRegister ReservedId = InProgressIt->second.Id;
    assert(ReservedId.isValid() && "in-progress scope must have a reserved id");
    return EmitResult<MCRegister>::emitted(ReservedId);
  }
 
  // Reserve the result id first: a dependency may refer back to this scope.
  assert(CurrentMAI && "debug scope id allocation requires CurrentMAI");
  MCRegister Id = CurrentMAI->getNextIDRegister();
  assert(Id.isValid() && "debug scope id must be a valid register");
  InProgressIt->second.Id = Id;
 
  EmitResult<PreparedScope> P = emitDebugScope(S);
  assert((!HasRelaxedExtInst || P.Status != EmitStatus::InProgress) &&
         "InProgress is only returned when forward references are unsupported");
  if (!P) {
    // Emission during recursion updates the container. Look the scope up again.
    InProgressIt = ScopesInProgress.find(S);
    assert(InProgressIt != ScopesInProgress.end() &&
           "scope must stay in progress until its instruction is emitted");
    bool ForwardReferenced = InProgressIt->second.ForwardReferenced;
    ScopesInProgress.erase(InProgressIt);
    // P here is either unsupported or in progress. When forward references are
    // supported, P can only be unsupported. Define the id only when an
    // already-emitted instruction named it.
    if (ForwardReferenced) {
      assert(HasRelaxedExtInst &&
             "a forward reference requires relaxed extended instructions");
      assert(P.Status == EmitStatus::Unsupported &&
             "a forward-referenced scope fails as unsupported");
      SPIRV::ModuleAnalysisInfo &MAI = *CurrentMAI;
      emitExtInst(SPIRV::NonSemanticExtInst::DebugInfoNone,
                  getOrEmitOpTypeVoidReg(MAI), MAI.getExtInstSetReg(NSSet), {},
                  MAI, Id);
    }
 
    // InProgress is a dropped back edge (when forward references are not
    // supported). Leave it out of FailedScopes so a later walk can retry the
    // scope. Regardless of forward references, cache unsupported scopes to
    // avoid retrying them.
    if (P.Status == EmitStatus::Unsupported)
      FailedScopes.insert(S);
    return P.Status == EmitStatus::InProgress
               ? EmitResult<MCRegister>::inProgress()
               : EmitResult<MCRegister>::unsupported();
  }
 
  // The scope was successfully emitted.
  SPIRV::ModuleAnalysisInfo &MAI = *CurrentMAI;
  MCRegister Reg =
      emitExtInst(P.Value->Opcode, getOrEmitOpTypeVoidReg(MAI),
                  MAI.getExtInstSetReg(NSSet), P.Value->Operands, MAI, Id);
  assert(Reg == Id &&
         "debug scope result id must reuse the id reserved at entry");
  ScopesInProgress.erase(S);
  assert(!GlobalNSDIEnabled &&
         "debug type or scope created after module-scope NSDI emission");
  DebugScopeRegs[S] = Reg;
  return EmitResult<MCRegister>::emitted(Reg);
}
 
auto SPIRVNonSemanticDebugHandler::emitDebugTypeBasic(
    const DIBasicType *BT, MCRegister I32TypeReg,
    SPIRV::ModuleAnalysisInfo &MAI) -> EmitResult<PreparedScope> {
  if (!isUInt<32>(BT->getSizeInBits()))
    return EmitResult<PreparedScope>::unsupported();
 
  MCRegister NameReg = getCachedOpStringReg(BT->getName());
  MCRegister SizeReg = emitOpConstantI32(
      static_cast<uint32_t>(BT->getSizeInBits()), I32TypeReg, MAI);
 
  // Map DWARF base type encodings to NSDI encoding codes per
  // NonSemantic.Shader.DebugInfo.100 specification, section 4.5.
  unsigned Encoding = 0; // Unspecified
  switch (BT->getEncoding()) {
  case dwarf::DW_ATE_address:
    Encoding = 1;
    break;
  case dwarf::DW_ATE_boolean:
    Encoding = 2;
    break;
  case dwarf::DW_ATE_float:
    Encoding = 3;
    break;
  case dwarf::DW_ATE_signed:
    Encoding = 4;
    break;
  case dwarf::DW_ATE_signed_char:
    Encoding = 5;
    break;
  case dwarf::DW_ATE_unsigned:
    Encoding = 6;
    break;
  case dwarf::DW_ATE_unsigned_char:
    Encoding = 7;
    break;
  }
  MCRegister EncodingReg = emitOpConstantI32(Encoding, I32TypeReg, MAI);
  MCRegister FlagsReg = emitOpConstantI32(0, I32TypeReg, MAI);
  return EmitResult<PreparedScope>::emitted(
      PreparedScope{SPIRV::NonSemanticExtInst::DebugTypeBasic,
                    {NameReg, SizeReg, EncodingReg, FlagsReg}});
}
 
auto SPIRVNonSemanticDebugHandler::emitDebugScope(const DIScope *S)
    -> EmitResult<PreparedScope> {
  assert(CurrentMAI && "emitDebugScope requires CurrentMAI");
  SPIRV::ModuleAnalysisInfo &MAI = *CurrentMAI;
  MCRegister ExtInstSetReg = MAI.getExtInstSetReg(NSSet);
  MCRegister VoidTypeReg = getOrEmitOpTypeVoidReg(MAI);
  MCRegister I32TypeReg = getOrEmitOpTypeInt32Reg(MAI);
 
  if (const auto *BT = dyn_cast<DIBasicType>(S))
    return emitDebugTypeBasic(BT, I32TypeReg, MAI);
  if (const auto *ST = dyn_cast<DISubroutineType>(S))
    return emitDebugTypeFunctionForSubroutineType(ST, MAI);
  if (const auto *CT = dyn_cast<DICompositeType>(S))
    return emitDebugTypeForCompositeType(CT, VoidTypeReg, I32TypeReg,
                                         ExtInstSetReg, MAI);
  if (const auto *DT = dyn_cast<DIDerivedType>(S))
    return emitDebugTypeForDerivedType(DT, VoidTypeReg, I32TypeReg,
                                       ExtInstSetReg, MAI);
  if (isa<DILexicalBlock, DINamespace>(S))
    return emitDebugLexicalBlock(S, VoidTypeReg, I32TypeReg, ExtInstSetReg,
                                 MAI);
  if (const auto *LBF = dyn_cast<DILexicalBlockFile>(S))
    return emitDebugLexicalBlockDiscriminator(LBF, VoidTypeReg, I32TypeReg,
                                              ExtInstSetReg, MAI);
  if (const auto *SP = dyn_cast<DISubprogram>(S)) {
    if (SP->isDefinition())
      return emitDebugFunction(SP, VoidTypeReg, I32TypeReg, ExtInstSetReg, MAI);
    return emitDebugFunctionDeclaration(SP, VoidTypeReg, I32TypeReg,
                                        ExtInstSetReg, MAI);
  }
  return EmitResult<PreparedScope>::unsupported();
}
 
auto SPIRVNonSemanticDebugHandler::emitDebugTypeForCompositeType(
    const DICompositeType *CT, MCRegister VoidTypeReg, MCRegister I32TypeReg,
    MCRegister ExtInstSetReg, SPIRV::ModuleAnalysisInfo &MAI)
    -> EmitResult<PreparedScope> {
  switch (CT->getTag()) {
  case dwarf::DW_TAG_array_type:
    // A vector is an array with DINode::FlagVector. A plain array is the
    // same tag without it. A matrix is also lowered to a DW_TAG_array_type
    // (two subranges), so it is indistinguishable from a 2D array here and
    // is emitted as a DebugTypeArray.
    //
    // FIXME: Emitting a matrix as a DebugTypeArray is valid but loses the
    // matrix shape. DWARF has no matrix tag, so distinguishing a matrix needs
    // a new DINode flag analogous to FlagVector, set on the array, plus a way
    // to carry column-major vs row-major traits. Array-of-vectors alone would
    // not disambiguate a matrix from a genuine array of vectors. Once the
    // frontend marks matrices, route them to a DebugTypeMatrix path here.
    if (CT->isVector())
      return emitDebugTypeVector(CT, MAI);
    return emitDebugTypeArray(CT, MAI);
  case dwarf::DW_TAG_structure_type:
  case dwarf::DW_TAG_class_type:
  case dwarf::DW_TAG_union_type:
    return emitDebugTypeComposite(CT, VoidTypeReg, I32TypeReg, ExtInstSetReg,
                                  MAI);
  case dwarf::DW_TAG_enumeration_type:
    return emitDebugTypeEnum(CT, VoidTypeReg, I32TypeReg, ExtInstSetReg, MAI);
  default:
    return EmitResult<PreparedScope>::unsupported();
  }
}
 
auto SPIRVNonSemanticDebugHandler::emitDebugTypeForDerivedType(
    const DIDerivedType *DT, MCRegister VoidTypeReg, MCRegister I32TypeReg,
    MCRegister ExtInstSetReg, SPIRV::ModuleAnalysisInfo &MAI)
    -> EmitResult<PreparedScope> {
  switch (DT->getTag()) {
  case dwarf::DW_TAG_pointer_type:
    return emitDebugTypePointer(DT, MAI);
  case dwarf::DW_TAG_typedef:
    return emitDebugTypedef(DT, VoidTypeReg, I32TypeReg, ExtInstSetReg, MAI);
  case dwarf::DW_TAG_member:
    return emitDebugTypeMember(DT, VoidTypeReg, I32TypeReg, ExtInstSetReg, MAI);
  default:
    return EmitResult<PreparedScope>::unsupported();
  }
}
 
auto SPIRVNonSemanticDebugHandler::emitDebugTypePointer(
    const DIDerivedType *PT, SPIRV::ModuleAnalysisInfo &MAI)
    -> EmitResult<PreparedScope> {
  // A DWARF address space is required to determine the SPIR-V storage class.
  // Skip pointer types that do not carry one.
  if (!PT->getDWARFAddressSpace().has_value())
    return EmitResult<PreparedScope>::unsupported();
 
  MCRegister BaseReg;
  if (const DIType *BaseTy = PT->getBaseType()) {
    EmitResult<MCRegister> Base = getOrCreateDebugScope(BaseTy);
    if (!Base)
      return EmitResult<PreparedScope>::failure(Base);
    BaseReg = *Base.Value;
  } else {
    // No getBaseType() (typical for void*): use DebugInfoNone as Base Type,
    // same as SPIRV-LLVM-Translator (see issue #109287 and the DISABLED
    // spirv-val run in debug-type-pointer.ll). spirv-val may still reject this
    // encoding; see https://github.com/KhronosGroup/SPIRV-Registry/pull/287.
    BaseReg = CachedDebugInfoNoneReg;
  }
 
  MCRegister I32TypeReg = getOrEmitOpTypeInt32Reg(MAI);
  MCRegister DebugTypePointerFlagsReg =
      emitOpConstantI32(transDebugFlags(PT), I32TypeReg, MAI);
 
  // For SPIR-V targets, Clang sets DwarfAddressSpace to the LLVM IR address
  // space, which addressSpaceToStorageClass expects.
  const auto &ST = static_cast<const SPIRVSubtarget &>(Asm->getSubtargetInfo());
  MCRegister StorageClassReg = emitOpConstantI32(
      addressSpaceToStorageClass(PT->getDWARFAddressSpace().value(), ST),
      I32TypeReg, MAI);
 
  return EmitResult<PreparedScope>::emitted(
      PreparedScope{SPIRV::NonSemanticExtInst::DebugTypePointer,
                    {BaseReg, StorageClassReg, DebugTypePointerFlagsReg}});
}
 
auto SPIRVNonSemanticDebugHandler::emitDebugTypeFunctionForSubroutineType(
    const DISubroutineType *ST, SPIRV::ModuleAnalysisInfo &MAI)
    -> EmitResult<PreparedScope> {
  MCRegister VoidTypeReg = getOrEmitOpTypeVoidReg(MAI);
  MCRegister I32TypeReg = getOrEmitOpTypeInt32Reg(MAI);
  MCRegister DebugTypeFunctionFlagsReg =
      emitOpConstantI32(transDebugFlags(ST), I32TypeReg, MAI);
  DITypeArray TA = ST->getTypeArray();
  SmallVector<MCRegister, 8> Ops;
  Ops.push_back(DebugTypeFunctionFlagsReg);
  // Empty DI type tuple: no explicit return or parameter slots (hand-written IR
  // may use !{}). Emit void-only prototype. Same as SPIRV-LLVM-Translator when
  // DISubroutineType::getTypeArray() has zero elements.
  if (TA.empty()) {
    Ops.push_back(VoidTypeReg);
  } else {
    for (unsigned I = 0, E = TA.size(); I != E; ++I) {
      bool IsReturnType = (I == 0);
      EmitResult<MCRegister> Slot =
          mapDISignatureTypeToReg(TA[I], VoidTypeReg, IsReturnType);
      // No emitted DebugType* id for this slot (e.g., pointer that
      // was skipped due missing address space, etc.).
      if (!Slot)
        return EmitResult<PreparedScope>::failure(Slot);
      Ops.push_back(*Slot.Value);
    }
  }
  return EmitResult<PreparedScope>::emitted(
      PreparedScope{SPIRV::NonSemanticExtInst::DebugTypeFunction, Ops});
}
 
// Match SPIRV-LLVM-Translator's selection logic for the Parent operand.
auto SPIRVNonSemanticDebugHandler::resolveScope(const DIScope *Scope,
                                                const DICompileUnit *FallbackCU)
    -> EmitResult<MCRegister> {
  if (!CLOpts.debug_lexical_block_discriminator_scope)
    while (const auto *LBF = dyn_cast_or_null<DILexicalBlockFile>(Scope))
      Scope = LBF->getScope();
 
  // These scopes have their own debug instruction.
  if (isa_and_nonnull<DIType, DILexicalBlock, DINamespace, DISubprogram,
                      DILexicalBlockFile>(Scope))
    return getOrCreateDebugScope(Scope);
 
  // For a file, compile-unit, or absent scope, fall back to a compile unit.
  auto CUResult = [](std::optional<MCRegister> Reg) {
    return Reg ? EmitResult<MCRegister>::emitted(*Reg)
               : EmitResult<MCRegister>::unsupported();
  };
  if (FallbackCU)
    return CUResult(lookupOptReg(DebugScopeRegs, FallbackCU));
 
  if (CompileUnits.empty())
    return EmitResult<MCRegister>::unsupported();
 
  return CUResult(lookupOptReg(DebugScopeRegs, CompileUnits[0].TheCU));
}
 
auto SPIRVNonSemanticDebugHandler::emitDebugLexicalBlock(
    const DIScope *S, MCRegister VoidTypeReg, MCRegister I32TypeReg,
    MCRegister ExtInstSetReg, SPIRV::ModuleAnalysisInfo &MAI)
    -> EmitResult<PreparedScope> {
  assert((isa<DILexicalBlock, DINamespace>(S)) &&
         "S must be a DILexicalBlock or DINamespace in emitDebugLexicalBlock");
  EmitResult<MCRegister> Parent = resolveScope(S->getScope());
  if (!Parent)
    return EmitResult<PreparedScope>::failure(Parent);
 
  MCRegister FileStrReg = getCachedScopePathOpStringReg(
      S->getFile(), /*UseEmptyPathIfNullScope=*/true);
  MCRegister SrcReg = getOrEmitDebugSourceForFileStrReg(FileStrReg, VoidTypeReg,
                                                        ExtInstSetReg, MAI);
 
  SmallVector<MCRegister, 5> Ops;
  if (const auto *LB = dyn_cast<DILexicalBlock>(S)) {
    MCRegister LineReg = emitOpConstantI32(static_cast<uint32_t>(LB->getLine()),
                                           I32TypeReg, MAI);
    MCRegister ColReg = emitOpConstantI32(
        static_cast<uint32_t>(LB->getColumn()), I32TypeReg, MAI);
    Ops = {SrcReg, LineReg, ColReg, *Parent.Value};
  } else {
    const auto *NS = cast<DINamespace>(S);
    // DINamespace carries no line/column info.
    MCRegister LineReg = emitOpConstantI32(0, I32TypeReg, MAI);
    MCRegister ColReg = emitOpConstantI32(0, I32TypeReg, MAI);
    MCRegister NameReg = getCachedOpStringReg(NS->getName());
    Ops = {SrcReg, LineReg, ColReg, *Parent.Value, NameReg};
  }
 
  return EmitResult<PreparedScope>::emitted(
      PreparedScope{SPIRV::NonSemanticExtInst::DebugLexicalBlock, Ops});
}
 
auto SPIRVNonSemanticDebugHandler::emitDebugLexicalBlockDiscriminator(
    const DILexicalBlockFile *LBF, MCRegister VoidTypeReg,
    MCRegister I32TypeReg, MCRegister ExtInstSetReg,
    SPIRV::ModuleAnalysisInfo &MAI) -> EmitResult<PreparedScope> {
  assert(LBF && "LBF must not be null");
  EmitResult<MCRegister> Parent = resolveScope(LBF->getScope());
  if (!Parent)
    return EmitResult<PreparedScope>::failure(Parent);
 
  MCRegister FileStrReg = getCachedScopePathOpStringReg(
      LBF->getFile(), /*UseEmptyPathIfNullScope=*/true);
  MCRegister SrcReg = getOrEmitDebugSourceForFileStrReg(FileStrReg, VoidTypeReg,
                                                        ExtInstSetReg, MAI);
  MCRegister DiscReg = emitOpConstantI32(
      static_cast<uint32_t>(LBF->getDiscriminator()), I32TypeReg, MAI);
  return EmitResult<PreparedScope>::emitted(
      PreparedScope{SPIRV::NonSemanticExtInst::DebugLexicalBlockDiscriminator,
                    {SrcReg, DiscReg, *Parent.Value}});
}
 
MCRegister SPIRVNonSemanticDebugHandler::getOrEmitDebugInlinedAt(
    const DILocation *IA, MCRegister VoidTypeReg, MCRegister I32TypeReg,
    MCRegister ExtInstSetReg, SPIRV::ModuleAnalysisInfo &MAI) {
  assert(IA && "IA must not be null in getOrEmitDebugInlinedAt");
 
  if (MCRegister Cached = DebugInlinedAtRegs.lookup(IA))
    return Cached;
 
  EmitResult<MCRegister> Scope = resolveScope(IA->getScope());
  if (!Scope)
    return MCRegister();
 
  MCRegister LineReg =
      emitOpConstantI32(static_cast<uint32_t>(IA->getLine()), I32TypeReg, MAI);
 
  SmallVector<MCRegister, 3> Ops{LineReg, *Scope.Value};
  // Recurse before building this instruction's operands so an outer
  // inlined-at link is always available.
  if (const DILocation *Outer = IA->getInlinedAt()) {
    MCRegister OuterReg = getOrEmitDebugInlinedAt(
        Outer, VoidTypeReg, I32TypeReg, ExtInstSetReg, MAI);
    if (!OuterReg.isValid())
      return MCRegister();
    Ops.push_back(OuterReg);
  }
 
  MCRegister Reg = emitExtInst(SPIRV::NonSemanticExtInst::DebugInlinedAt,
                               VoidTypeReg, ExtInstSetReg, Ops, MAI);
  DebugInlinedAtRegs[IA] = Reg;
  return Reg;
}
 
auto SPIRVNonSemanticDebugHandler::emitDebugFunctionDeclaration(
    const DISubprogram *SP, MCRegister VoidTypeReg, MCRegister I32TypeReg,
    MCRegister ExtInstSetReg, SPIRV::ModuleAnalysisInfo &MAI)
    -> EmitResult<PreparedScope> {
  assert(SP && "SP must not be null in emitDebugFunctionDeclaration");
  assert(!SP->isDefinition() &&
         "SP must not be a definition in emitDebugFunctionDeclaration");
 
  // The IR verifier already enforces that this cannot be null.
  EmitResult<MCRegister> FnTy = getOrCreateDebugScope(SP->getType());
  if (!FnTy)
    return EmitResult<PreparedScope>::failure(FnTy);
 
  EmitResult<MCRegister> Parent = resolveScope(SP->getScope(), SP->getUnit());
  if (!Parent)
    return EmitResult<PreparedScope>::failure(Parent);
 
  MCRegister FileStrReg = getCachedScopePathOpStringReg(SP);
 
  MCRegister NameReg = getCachedOpStringReg(SP->getName());
  MCRegister LinkageReg = getCachedOpStringReg(SP->getLinkageName());
  MCRegister SrcReg = getOrEmitDebugSourceForFileStrReg(FileStrReg, VoidTypeReg,
                                                        ExtInstSetReg, MAI);
 
  MCRegister LineReg =
      emitOpConstantI32(static_cast<uint32_t>(SP->getLine()), I32TypeReg, MAI);
  MCRegister ColReg = emitOpConstantI32(0, I32TypeReg, MAI);
 
  uint32_t FlagsVal = transDebugFlags(SP);
  // TODO: When composite scopes are DebugFunctionDeclaration parents (available
  // in DebugScopeRegs), sync declaration Flags with SPIRV-LLVM-Translator.
  FlagsVal &= ~NSDIFlagIsDefinition;
  MCRegister FlagsReg = emitOpConstantI32(FlagsVal, I32TypeReg, MAI);
 
  return EmitResult<PreparedScope>::emitted(
      PreparedScope{SPIRV::NonSemanticExtInst::DebugFunctionDeclaration,
                    {NameReg, *FnTy.Value, SrcReg, LineReg, ColReg,
                     *Parent.Value, LinkageReg, FlagsReg}});
}
 
auto SPIRVNonSemanticDebugHandler::emitDebugFunction(
    const DISubprogram *SP, MCRegister VoidTypeReg, MCRegister I32TypeReg,
    MCRegister ExtInstSetReg, SPIRV::ModuleAnalysisInfo &MAI)
    -> EmitResult<PreparedScope> {
  assert(SP && "SP must not be null in emitDebugFunction");
  assert(SP->isDefinition() && "SP must be a definition in emitDebugFunction");
 
  EmitResult<MCRegister> FnTy = getOrCreateDebugScope(SP->getType());
  if (!FnTy)
    return EmitResult<PreparedScope>::failure(FnTy);
 
  EmitResult<MCRegister> Parent = resolveScope(SP->getScope(), SP->getUnit());
  if (!Parent)
    return EmitResult<PreparedScope>::failure(Parent);
 
  MCRegister NameReg = getCachedOpStringReg(SP->getName());
  MCRegister LinkageReg = getCachedOpStringReg(SP->getLinkageName());
  MCRegister FileStrReg = getCachedScopePathOpStringReg(SP);
  MCRegister SrcReg = getOrEmitDebugSourceForFileStrReg(FileStrReg, VoidTypeReg,
                                                        ExtInstSetReg, MAI);
 
  MCRegister LineReg =
      emitOpConstantI32(static_cast<uint32_t>(SP->getLine()), I32TypeReg, MAI);
  // LLVM's DISubprogram has no column field but SPIR-V expects one in
  // DebugFunction.
  MCRegister ColReg = emitOpConstantI32(0, I32TypeReg, MAI);
  MCRegister FlagsReg = emitOpConstantI32(transDebugFlags(SP), I32TypeReg, MAI);
  MCRegister ScopeLineReg = emitOpConstantI32(
      static_cast<uint32_t>(SP->getScopeLine()), I32TypeReg, MAI);
 
  SmallVector<MCRegister, 10> Ops = {NameReg,    *FnTy.Value, SrcReg,
                                     LineReg,    ColReg,      *Parent.Value,
                                     LinkageReg, FlagsReg,    ScopeLineReg};
 
  if (const DISubprogram *Decl = SP->getDeclaration()) {
    EmitResult<MCRegister> DeclRes = getOrCreateDebugScope(Decl);
    if (DeclRes)
      Ops.push_back(*DeclRes.Value);
  }
 
  return EmitResult<PreparedScope>::emitted(
      PreparedScope{SPIRV::NonSemanticExtInst::DebugFunction, Ops});
}
 
auto SPIRVNonSemanticDebugHandler::mapDISignatureTypeToReg(
    const DIType *Ty, MCRegister VoidTypeReg, bool ReturnType)
    -> EmitResult<MCRegister> {
  if (!Ty) {
    if (ReturnType)
      return EmitResult<MCRegister>::emitted(VoidTypeReg);
    assert(CachedDebugInfoNoneReg.isValid() &&
           "DebugInfoNone must be emitted before DISubroutineType operands");
    return EmitResult<MCRegister>::emitted(CachedDebugInfoNoneReg);
  }
  return getOrCreateDebugScope(Ty);
}
 
// NonSemantic.Shader.DebugInfo.100 debug operation encodings
// (section 4.5, "Debug Operations").
enum class NonSemanticDebugOp : uint32_t {
  Deref = 0,
  Plus = 1,
  Minus = 2,
  PlusUconst = 3,
  BitPiece = 4,
  Swap = 5,
  Xderef = 6,
  StackValue = 7,
  Constu = 8,
  Fragment = 9
};
 
static std::optional<NonSemanticDebugOp>
mapDwarfOpToNonSemanticOp(uint64_t DwarfOp) {
  switch (DwarfOp) {
  case dwarf::DW_OP_deref:
    return NonSemanticDebugOp::Deref;
  case dwarf::DW_OP_plus:
    return NonSemanticDebugOp::Plus;
  case dwarf::DW_OP_minus:
    return NonSemanticDebugOp::Minus;
  case dwarf::DW_OP_plus_uconst:
    return NonSemanticDebugOp::PlusUconst;
  case dwarf::DW_OP_bit_piece:
    return NonSemanticDebugOp::BitPiece;
  case dwarf::DW_OP_swap:
    return NonSemanticDebugOp::Swap;
  case dwarf::DW_OP_xderef:
    return NonSemanticDebugOp::Xderef;
  case dwarf::DW_OP_stack_value:
    return NonSemanticDebugOp::StackValue;
  case dwarf::DW_OP_constu:
    return NonSemanticDebugOp::Constu;
  case dwarf::DW_OP_LLVM_fragment:
    return NonSemanticDebugOp::Fragment;
  default:
    return std::nullopt;
  }
}
 
// The DebugOperation operand values for \p Op. Each becomes an OpConstant of
// OpTypeInt 32 0, so every argument must fit in 32 bits.
static std::optional<SmallVector<uint32_t, 3>>
mapExprOperand(const DIExpression::ExprOperand &Op) {
  std::optional<NonSemanticDebugOp> NSOp =
      mapDwarfOpToNonSemanticOp(Op.getOp());
  if (!NSOp)
    return std::nullopt;
 
  SmallVector<uint32_t, 3> Operands{static_cast<uint32_t>(*NSOp)};
  for (unsigned I = 0, E = Op.getNumArgs(); I != E; ++I) {
    uint64_t Arg = Op.getArg(I);
    if (!isUInt<32>(Arg))
      return std::nullopt;
    Operands.push_back(static_cast<uint32_t>(Arg));
  }
  return Operands;
}
 
std::optional<MCRegister> SPIRVNonSemanticDebugHandler::emitDebugOperation(
    const DIExpression::ExprOperand &Op, MCRegister VoidTypeReg,
    MCRegister I32TypeReg, MCRegister ExtInstSetReg,
    SPIRV::ModuleAnalysisInfo &MAI) {
  std::optional<SmallVector<uint32_t, 3>> Key = mapExprOperand(Op);
  if (!Key)
    return std::nullopt;
 
  auto [It, Inserted] = DebugOperationCache.try_emplace(std::move(*Key));
  if (!Inserted)
    return It->second;
 
  SmallVector<MCRegister, 3> Operands;
  for (uint32_t V : It->first)
    Operands.push_back(emitOpConstantI32(V, I32TypeReg, MAI));
  MCRegister Reg = emitExtInst(SPIRV::NonSemanticExtInst::DebugOperation,
                               VoidTypeReg, ExtInstSetReg, Operands, MAI);
  It->second = Reg;
  return Reg;
}
 
std::optional<MCRegister> SPIRVNonSemanticDebugHandler::emitDebugExpression(
    const DIExpression *Expr, MCRegister VoidTypeReg, MCRegister I32TypeReg,
    MCRegister ExtInstSetReg, SPIRV::ModuleAnalysisInfo &MAI) {
  assert(Expr && "Expr must not be null in emitDebugExpression");
 
  SmallVector<MCRegister> OperationRegs;
  for (const DIExpression::ExprOperand &Op : Expr->expr_ops()) {
    std::optional<MCRegister> OpReg =
        emitDebugOperation(Op, VoidTypeReg, I32TypeReg, ExtInstSetReg, MAI);
    if (!OpReg)
      return std::nullopt;
    OperationRegs.push_back(*OpReg);
  }
 
  auto [It, Inserted] =
      DebugExpressionCache.try_emplace(std::move(OperationRegs));
  if (!Inserted)
    return It->second;
 
  MCRegister Reg = emitExtInst(SPIRV::NonSemanticExtInst::DebugExpression,
                               VoidTypeReg, ExtInstSetReg, It->first, MAI);
  It->second = Reg;
  return Reg;
}
 
std::optional<MCRegister> SPIRVNonSemanticDebugHandler::emitDebugGlobalVariable(
    const DIGlobalVariable *GV, const GlobalVariableDebugInfo &Info,
    MCRegister VoidTypeReg, MCRegister I32TypeReg, MCRegister ExtInstSetReg,
    SPIRV::ModuleAnalysisInfo &MAI) {
  assert(GV && "GV must not be null in emitDebugGlobalVariable");
 
  EmitResult<MCRegister> Parent = resolveScope(GV->getScope());
  if (!Parent)
    return std::nullopt;
 
  MCRegister ParentReg = *Parent.Value;
 
  // TyReg: DebugInfoNone when GV has no DI type (as done in
  // SPIRV-LLVM-Translator). Declarations (isDefinition: false) can have null
  // getType() while definitions must have a non-null one (enforced by the IR
  // verifier).
  MCRegister TyReg = CachedDebugInfoNoneReg;
  if (const DIType *Ty = GV->getType()) {
    auto TyRegOpt = lookupOptReg(DebugScopeRegs, Ty);
    if (!TyRegOpt)
      return std::nullopt;
    TyReg = *TyRegOpt;
  }
 
  std::optional<MCRegister> StaticMemberRegOpt;
  if (const DIDerivedType *SM = GV->getStaticDataMemberDeclaration()) {
    // Do not create the member here, just look it up to avoid orphaning it.
    StaticMemberRegOpt = lookupOptReg(DebugScopeRegs, SM);
    if (!StaticMemberRegOpt)
      return std::nullopt;
  }
 
  MCRegister NameReg = getCachedOpStringReg(GV->getName());
  MCRegister LinkageReg = getCachedOpStringReg(GV->getLinkageName());
  MCRegister FileStrReg = getCachedScopePathOpStringReg(
      GV->getFile(), /*UseEmptyPathIfNullScope=*/true);
  MCRegister SrcReg = getOrEmitDebugSourceForFileStrReg(FileStrReg, VoidTypeReg,
                                                        ExtInstSetReg, MAI);
 
  MCRegister LineReg =
      emitOpConstantI32(static_cast<uint32_t>(GV->getLine()), I32TypeReg, MAI);
  // DIGlobalVariable or DIGlobalVariableExpression metadata carry no column
  // field. Column is hardcoded to 0 (because it can't be determined), matching
  // SPIRV-LLVM-Translator.
  MCRegister ColReg = emitOpConstantI32(0, I32TypeReg, MAI);
 
  // Variable: @g OpVariable id when !dbg matches; else a DebugExpression for
  // the GVE init value when no @g exists and the expression is non-empty; else
  // DebugInfoNone. As per spec, the DebugExpression must contain the constant
  // value of the variable that was optimized out. An empty expression contains
  // no value, so we emit DebugInfoNone instead.
  MCRegister VariableReg = CachedDebugInfoNoneReg;
  if (const GlobalVariable *LLVMGV = Info.LLVMGV) {
    MCRegister GVReg = MAI.getGlobalObjReg(LLVMGV);
    if (GVReg.isValid())
      VariableReg = GVReg;
  } else if (Info.Expr && Info.Expr->getNumElements() != 0) {
    if (auto ExprReg = emitDebugExpression(Info.Expr, VoidTypeReg, I32TypeReg,
                                           ExtInstSetReg, MAI))
      VariableReg = *ExprReg;
  }
 
  MCRegister FlagsReg = emitOpConstantI32(transDebugFlags(GV), I32TypeReg, MAI);
 
  SmallVector<MCRegister, 10> Ops = {NameReg,    TyReg,       SrcReg,
                                     LineReg,    ColReg,      ParentReg,
                                     LinkageReg, VariableReg, FlagsReg};
 
  if (StaticMemberRegOpt)
    Ops.push_back(*StaticMemberRegOpt);
 
  return emitExtInst(SPIRV::NonSemanticExtInst::DebugGlobalVariable,
                     VoidTypeReg, ExtInstSetReg, Ops, MAI);
}
 
std::optional<MCRegister> SPIRVNonSemanticDebugHandler::emitDebugLocalVariable(
    const DILocalVariable *LV, MCRegister VoidTypeReg, MCRegister I32TypeReg,
    MCRegister ExtInstSetReg, SPIRV::ModuleAnalysisInfo &MAI) {
  assert(LV && "LV must not be null in emitDebugLocalVariable");
 
  EmitResult<MCRegister> Parent = resolveScope(LV->getScope());
  if (!Parent)
    return std::nullopt;
 
  MCRegister TyReg = CachedDebugInfoNoneReg;
  if (const DIType *Ty = LV->getType()) {
    auto TyRegOpt = lookupOptReg(DebugScopeRegs, Ty);
    if (!TyRegOpt)
      return std::nullopt;
    TyReg = *TyRegOpt;
  }
 
  MCRegister NameReg = getCachedOpStringReg(LV->getName());
  MCRegister FileStrReg = getCachedScopePathOpStringReg(
      LV->getFile(), /*UseEmptyPathIfNullScope=*/true);
  MCRegister SrcReg = getOrEmitDebugSourceForFileStrReg(FileStrReg, VoidTypeReg,
                                                        ExtInstSetReg, MAI);
  MCRegister LineReg =
      emitOpConstantI32(static_cast<uint32_t>(LV->getLine()), I32TypeReg, MAI);
  // DILocalVariable has no column field. Column is hardcoded to 0.
  MCRegister ColReg = emitOpConstantI32(0, I32TypeReg, MAI);
  MCRegister FlagsReg = emitOpConstantI32(transDebugFlags(LV), I32TypeReg, MAI);
 
  SmallVector<MCRegister, 8> Ops = {NameReg, TyReg,         SrcReg,  LineReg,
                                    ColReg,  *Parent.Value, FlagsReg};
  if (unsigned Arg = LV->getArg())
    Ops.push_back(emitOpConstantI32(Arg, I32TypeReg, MAI));
 
  return emitExtInst(SPIRV::NonSemanticExtInst::DebugLocalVariable, VoidTypeReg,
                     ExtInstSetReg, Ops, MAI);
}
 
auto SPIRVNonSemanticDebugHandler::emitDebugTypeVector(
    const DICompositeType *VT, SPIRV::ModuleAnalysisInfo &MAI)
    -> EmitResult<PreparedScope> {
  const auto *BaseTy = dyn_cast_or_null<DIBasicType>(VT->getBaseType());
  if (!BaseTy)
    return EmitResult<PreparedScope>::unsupported();
 
  // DebugTypeVector models only 1D vectors (multi-subrange types cannot be
  // encoded).
  DINodeArray Elements = VT->getElements();
  if (Elements.size() != 1)
    return EmitResult<PreparedScope>::unsupported();
  const auto *SR = cast<DISubrange>(Elements[0]);
  const auto *CI = dyn_cast_if_present<ConstantInt *>(SR->getCount());
  if (!CI)
    return EmitResult<PreparedScope>::unsupported();
 
  EmitResult<MCRegister> Base = getOrCreateDebugScope(BaseTy);
  if (!Base)
    return EmitResult<PreparedScope>::failure(Base);
 
  MCRegister I32TypeReg = getOrEmitOpTypeInt32Reg(MAI);
  MCRegister CountReg = emitOpConstantI32(
      static_cast<uint32_t>(CI->getZExtValue()), I32TypeReg, MAI);
  return EmitResult<PreparedScope>::emitted(PreparedScope{
      SPIRV::NonSemanticExtInst::DebugTypeVector, {*Base.Value, CountReg}});
}
 
auto SPIRVNonSemanticDebugHandler::emitDebugTypeArray(
    const DICompositeType *AT, SPIRV::ModuleAnalysisInfo &MAI)
    -> EmitResult<PreparedScope> {
  // Unlike DebugTypeVector, the element may be any debug type, not only a
  // basic type. Create it first so this array names an id that already exists.
  EmitResult<MCRegister> Base = getOrCreateDebugScope(AT->getBaseType());
  if (!Base)
    return EmitResult<PreparedScope>::failure(Base);
 
  MCRegister I32TypeReg = getOrEmitOpTypeInt32Reg(MAI);
 
  SmallVector<MCRegister> Ops;
  Ops.push_back(*Base.Value);
 
  // One component count per DISubrange, in DWARF subrange order. Emit 0 for
  // counts that are not a compile-time constant (dynamic arrays). This matches
  // OpTypeRuntimeArray.
  for (const DINode *Element : AT->getElements()) {
    const auto *SR = dyn_cast<DISubrange>(Element);
    if (!SR)
      continue;
    // A DIVariable count (a variable-length array) is not a ConstantInt, so it
    // maps to 0 here. DebugTypeArray also allows a DebugLocalVariable or
    // DebugGlobalVariable id for it, but no frontend we target emits one. A
    // constant wider than 32 bits maps to 0 too, since the count operand is a
    // 32-bit OpConstant and such an array cannot occur in a shader.
    uint32_t Count = 0;
    if (const auto *CI = dyn_cast_if_present<ConstantInt *>(SR->getCount())) {
      const APInt &Value = CI->getValue();
      if (Value.getActiveBits() <= 32)
        Count = static_cast<uint32_t>(Value.getZExtValue());
    }
    Ops.push_back(emitOpConstantI32(Count, I32TypeReg, MAI));
  }
 
  return EmitResult<PreparedScope>::emitted(
      PreparedScope{SPIRV::NonSemanticExtInst::DebugTypeArray, Ops});
}
 
auto SPIRVNonSemanticDebugHandler::emitDebugTypeMember(
    const DIDerivedType *M, MCRegister VoidTypeReg, MCRegister I32TypeReg,
    MCRegister ExtInstSetReg, SPIRV::ModuleAnalysisInfo &MAI)
    -> EmitResult<PreparedScope> {
  EmitResult<MCRegister> Ty = getOrCreateDebugScope(M->getBaseType());
  if (!Ty)
    return EmitResult<PreparedScope>::failure(Ty);
 
  if (!isUInt<32>(M->getOffsetInBits()) || !isUInt<32>(M->getSizeInBits()))
    return EmitResult<PreparedScope>::unsupported();
 
  MCRegister NameReg = getCachedOpStringReg(M->getName());
  MCRegister FileStrReg = getCachedScopePathOpStringReg(
      M->getFile(), /*UseEmptyPathIfNullScope=*/true);
  MCRegister SrcReg = getOrEmitDebugSourceForFileStrReg(FileStrReg, VoidTypeReg,
                                                        ExtInstSetReg, MAI);
  MCRegister LineReg =
      emitOpConstantI32(static_cast<uint32_t>(M->getLine()), I32TypeReg, MAI);
 
  // DIDerivedType members carry no column, so emit 0.
  MCRegister ColReg = emitOpConstantI32(0, I32TypeReg, MAI);
  MCRegister OffsetReg = emitOpConstantI32(
      static_cast<uint32_t>(M->getOffsetInBits()), I32TypeReg, MAI);
  MCRegister SizeReg = emitOpConstantI32(
      static_cast<uint32_t>(M->getSizeInBits()), I32TypeReg, MAI);
  MCRegister FlagsReg = emitOpConstantI32(transDebugFlags(M), I32TypeReg, MAI);
 
  // In NonSemantic.Shader.DebugInfo a DebugTypeMember has no Parent operand:
  // only the composite references its members. This is by design, it drops the
  // Parent that OpenCL.DebugInfo.100 had, and it avoids a composite/member
  // reference cycle.
  //
  // FIXME: Static members are not handled yet: their constant initializer is
  // available but is not emitted as the optional Value operand, and under DWARF
  // 5 a static member is tagged DW_TAG_variable, which the caller's member loop
  // skips.
  return EmitResult<PreparedScope>::emitted(
      PreparedScope{SPIRV::NonSemanticExtInst::DebugTypeMember,
                    {NameReg, *Ty.Value, SrcReg, LineReg, ColReg, OffsetReg,
                     SizeReg, FlagsReg}});
}
 
auto SPIRVNonSemanticDebugHandler::emitDebugTypeComposite(
    const DICompositeType *CT, MCRegister VoidTypeReg, MCRegister I32TypeReg,
    MCRegister ExtInstSetReg, SPIRV::ModuleAnalysisInfo &MAI)
    -> EmitResult<PreparedScope> {
  // Parent and size before any member: a failure must stream nothing, or a
  // retry would emit the members again.
  EmitResult<MCRegister> Parent = resolveScope(CT->getScope());
  if (!Parent)
    return EmitResult<PreparedScope>::failure(Parent);
 
  if (!isUInt<32>(CT->getSizeInBits()))
    return EmitResult<PreparedScope>::unsupported();
 
  SmallVector<MCRegister, 8> MemberRegs;
  for (const DINode *Element : CT->getElements()) {
    const auto *M = dyn_cast<DIDerivedType>(Element);
    if (!M || M->getTag() != dwarf::DW_TAG_member)
      continue;
    EmitResult<MCRegister> Member = getOrCreateDebugScope(M);
    if (Member)
      MemberRegs.push_back(*Member.Value);
  }
 
  MCRegister NameReg = getCachedOpStringReg(CT->getName());
  MCRegister LinkageReg = getCachedOpStringReg(CT->getIdentifier());
  MCRegister FileStrReg = getCachedScopePathOpStringReg(
      CT->getFile(), /*UseEmptyPathIfNullScope=*/true);
  MCRegister SrcReg = getOrEmitDebugSourceForFileStrReg(FileStrReg, VoidTypeReg,
                                                        ExtInstSetReg, MAI);
 
  MCRegister TagReg =
      emitOpConstantI32(mapCompositeTypeTag(CT->getTag()), I32TypeReg, MAI);
  MCRegister LineReg =
      emitOpConstantI32(static_cast<uint32_t>(CT->getLine()), I32TypeReg, MAI);
  MCRegister ColReg = emitOpConstantI32(0, I32TypeReg, MAI);
 
  // A forward declaration has no known size or members: Size is DebugInfoNone.
  MCRegister SizeReg = CachedDebugInfoNoneReg;
  if (!CT->isForwardDecl())
    SizeReg = emitOpConstantI32(static_cast<uint32_t>(CT->getSizeInBits()),
                                I32TypeReg, MAI);
 
  MCRegister FlagsReg = emitOpConstantI32(transDebugFlags(CT), I32TypeReg, MAI);
 
  SmallVector<MCRegister> Ops = {NameReg,    TagReg,  SrcReg,
                                 LineReg,    ColReg,  *Parent.Value,
                                 LinkageReg, SizeReg, FlagsReg};
  Ops.append(MemberRegs.begin(), MemberRegs.end());
  return EmitResult<PreparedScope>::emitted(
      PreparedScope{SPIRV::NonSemanticExtInst::DebugTypeComposite, Ops});
}
 
auto SPIRVNonSemanticDebugHandler::emitDebugTypeEnum(
    const DICompositeType *ET, MCRegister VoidTypeReg, MCRegister I32TypeReg,
    MCRegister ExtInstSetReg, SPIRV::ModuleAnalysisInfo &MAI)
    -> EmitResult<PreparedScope> {
  // Skip incomplete enums.
  uint64_t Size = ET->getSizeInBits();
  if (Size == 0 || !isUInt<32>(Size))
    return EmitResult<PreparedScope>::unsupported();
 
  MCRegister UnderlyingReg = CachedDebugInfoNoneReg;
  if (const DIType *BaseTy = ET->getBaseType()) {
    EmitResult<MCRegister> Base = getOrCreateDebugScope(BaseTy);
    if (!Base)
      return EmitResult<PreparedScope>::failure(Base);
    UnderlyingReg = *Base.Value;
  }
 
  EmitResult<MCRegister> Parent =
      resolveScope(ET->getScope(), EnumCompileUnits.lookup(ET));
  if (!Parent)
    return EmitResult<PreparedScope>::failure(Parent);
 
  MCRegister NameReg = getCachedOpStringReg(ET->getName());
  MCRegister FileStrReg = getCachedScopePathOpStringReg(
      ET->getFile(), /*UseEmptyPathIfNullScope=*/true);
  MCRegister SrcReg = getOrEmitDebugSourceForFileStrReg(FileStrReg, VoidTypeReg,
                                                        ExtInstSetReg, MAI);
  MCRegister LineReg =
      emitOpConstantI32(static_cast<uint32_t>(ET->getLine()), I32TypeReg, MAI);
  // DICompositeType carries no column, so emit 0.
  MCRegister ColReg = emitOpConstantI32(0, I32TypeReg, MAI);
  MCRegister SizeReg =
      emitOpConstantI32(static_cast<uint32_t>(Size), I32TypeReg, MAI);
  MCRegister FlagsReg = emitOpConstantI32(transDebugFlags(ET), I32TypeReg, MAI);
 
  SmallVector<MCRegister> Ops = {NameReg, UnderlyingReg, SrcReg,  LineReg,
                                 ColReg,  *Parent.Value, SizeReg, FlagsReg};
 
  // Each Value is a 32-bit integer constant. Skip the Value and Name pair of an
  // enumerator whose value needs more bits. Otherwise, the truncation would
  // show a different value.
  for (const DINode *Element : ET->getElements()) {
    const auto *E = dyn_cast<DIEnumerator>(Element);
    if (!E)
      continue;
    const APInt &Value = E->getValue();
    if (E->isUnsigned() ? !Value.isIntN(32) : !Value.isSignedIntN(32))
      continue;
    uint32_t Bits = E->isUnsigned()
                        ? static_cast<uint32_t>(Value.getZExtValue())
                        : static_cast<uint32_t>(Value.getSExtValue());
    Ops.push_back(emitOpConstantI32(Bits, I32TypeReg, MAI));
    Ops.push_back(getCachedOpStringReg(E->getName()));
  }
 
  return EmitResult<PreparedScope>::emitted(
      PreparedScope{SPIRV::NonSemanticExtInst::DebugTypeEnum, Ops});
}
 
auto SPIRVNonSemanticDebugHandler::emitDebugTypedef(
    const DIDerivedType *TD, MCRegister VoidTypeReg, MCRegister I32TypeReg,
    MCRegister ExtInstSetReg, SPIRV::ModuleAnalysisInfo &MAI)
    -> EmitResult<PreparedScope> {
  EmitResult<MCRegister> Base = getOrCreateDebugScope(TD->getBaseType());
  if (!Base)
    return EmitResult<PreparedScope>::failure(Base);
 
  MCRegister NameReg = getCachedOpStringReg(TD->getName());
  MCRegister FileStrReg = getCachedScopePathOpStringReg(
      TD->getFile(), /*UseEmptyPathIfNullScope=*/true);
  MCRegister SrcReg = getOrEmitDebugSourceForFileStrReg(FileStrReg, VoidTypeReg,
                                                        ExtInstSetReg, MAI);
  MCRegister LineReg =
      emitOpConstantI32(static_cast<uint32_t>(TD->getLine()), I32TypeReg, MAI);
  // DIDerivedType typedefs carry no column, so emit 0.
  MCRegister ColReg = emitOpConstantI32(0, I32TypeReg, MAI);
 
  // Parent must be a lexical scope. Valid NSDI lexical scopes are
  // DebugCompilationUnit, DebugFunction, DebugLexicalBlock, or
  // DebugTypeComposite.
  EmitResult<MCRegister> Parent = resolveScope(TD->getScope());
  if (!Parent)
    return EmitResult<PreparedScope>::failure(Parent);
 
  return EmitResult<PreparedScope>::emitted(PreparedScope{
      SPIRV::NonSemanticExtInst::DebugTypedef,
      {NameReg, *Base.Value, SrcReg, LineReg, ColReg, *Parent.Value}});
}
 
void SPIRVNonSemanticDebugHandler::emitNonSemanticDebugStrings(
    SPIRV::ModuleAnalysisInfo &MAI) {
  if (CompileUnits.empty())
    return;
  // Check that prepareModuleOutput() registered the extended instruction set.
  // If the subtarget does not support the extension, neither strings nor ext
  // insts are emitted.
  if (!MAI.getExtInstSetReg(NSSet).isValid())
    return;
 
  for (const CompileUnitInfo &Info : CompileUnits) {
    if (Info.TheCU) {
      MCRegister PathReg = emitOpStringIfNew(Info.FilePath, MAI);
      ScopeToPathOpStringReg[Info.TheCU] = PathReg;
      if (const DIFile *F = Info.TheCU->getFile())
        ScopeToPathOpStringReg[F] = PathReg;
    }
  }
 
  for (const DISubprogram *SP : Subprograms) {
    emitOpStringIfNew(SP->getName(), MAI);
    emitOpStringIfNew(SP->getLinkageName(), MAI);
    emitAndCacheScopePathOpStringReg(SP, MAI);
  }
 
  for (const DIType *Ty : DebugTypes) {
    if (const auto *BT = dyn_cast<DIBasicType>(Ty)) {
      emitOpStringIfNew(BT->getName(), MAI);
      continue;
    }
    if (const auto *CT = dyn_cast<DICompositeType>(Ty)) {
      // Cache the enum's name, file path and enumerator names as OpStrings for
      // DebugTypeEnum.
      if (CT->getTag() == dwarf::DW_TAG_enumeration_type) {
        emitOpStringIfNew(CT->getName(), MAI);
        emitAndCacheScopePathOpStringReg(CT->getFile(), MAI);
        for (const DINode *Element : CT->getElements())
          if (const auto *E = dyn_cast<DIEnumerator>(Element))
            emitOpStringIfNew(E->getName(), MAI);
        continue;
      }
      // Cache the OpStrings each DebugTypeComposite and its DebugTypeMembers
      // use: the composite name, identifier (linkage name), and path, plus
      // each member name and path. Arrays and vectors have no such strings.
      if (CT->getTag() != dwarf::DW_TAG_structure_type &&
          CT->getTag() != dwarf::DW_TAG_class_type &&
          CT->getTag() != dwarf::DW_TAG_union_type)
        continue;
      emitOpStringIfNew(CT->getName(), MAI);
      emitOpStringIfNew(CT->getIdentifier(), MAI);
      emitAndCacheScopePathOpStringReg(CT->getFile(), MAI);
      for (const DINode *Element : CT->getElements()) {
        const auto *M = dyn_cast<DIDerivedType>(Element);
        if (!M || M->getTag() != dwarf::DW_TAG_member)
          continue;
        emitOpStringIfNew(M->getName(), MAI);
        emitAndCacheScopePathOpStringReg(M->getFile(), MAI);
      }
      continue;
    }
    // Cache the name and path OpStrings each DebugTypedef uses.
    const auto *TD = dyn_cast<DIDerivedType>(Ty);
    if (TD && TD->getTag() == dwarf::DW_TAG_typedef) {
      emitOpStringIfNew(TD->getName(), MAI);
      emitAndCacheScopePathOpStringReg(TD->getFile(), MAI);
    }
  }
 
  for (const auto &[GV, _] : GlobalVariableDebugInfoMap) {
    emitOpStringIfNew(GV->getName(), MAI);
    emitOpStringIfNew(GV->getLinkageName(), MAI);
    emitAndCacheScopePathOpStringReg(GV->getFile(), MAI);
  }
 
  for (const DILocalVariable *LV : LocalVariables) {
    emitOpStringIfNew(LV->getName(), MAI);
    emitAndCacheScopePathOpStringReg(LV->getFile(), MAI);
  }
 
  for (const DIScope *S : LexicalBlocks) {
    emitAndCacheScopePathOpStringReg(S->getFile(), MAI);
    if (const auto *NS = dyn_cast<DINamespace>(S))
      emitOpStringIfNew(NS->getName(), MAI);
  }
 
  for (const DILocation *DL : UniqueDebugLocations)
    emitAndCacheScopePathOpStringReg(DL->getScope(), MAI);
 
  CachedEmptyStringReg = emitOpStringIfNew("", MAI);
 
#ifndef NDEBUG
  NonSemanticOpStringsSectionEmitted = true;
#endif
}
 
void SPIRVNonSemanticDebugHandler::emitDebugFunctionDefinition(
    MCRegister DebugFunctionReg, MCRegister OpFunctionReg,
    SPIRV::ModuleAnalysisInfo &MAI) {
  assert(DebugFunctionReg.isValid() && OpFunctionReg.isValid() &&
         "DebugFunctionDefinition operands must be valid");
  MCRegister VoidTypeReg = getOrEmitOpTypeVoidReg(MAI);
  MCRegister ExtInstSetReg = MAI.getExtInstSetReg(NSSet);
  emitExtInst(SPIRV::NonSemanticExtInst::DebugFunctionDefinition, VoidTypeReg,
              ExtInstSetReg, {DebugFunctionReg, OpFunctionReg}, MAI);
}
 
void SPIRVNonSemanticDebugHandler::resetPerFunctionDebugState() {
  CurrentMF = nullptr;
  LastFunctionOpVariable = nullptr;
  DebugFunctionDefinitionEmitted = false;
  LastLineMI = nullptr;
  LastScopeMI = nullptr;
  Records.clear();
}
 
void SPIRVNonSemanticDebugHandler::preparePerFunctionDebug(
    const MachineFunction *MF) {
  resetPerFunctionDebugState();
  if (!GlobalNSDIEnabled || !CurrentMAI)
    return;
 
  CurrentMF = MF;
 
  if (MF->getFunction()
          .getFnAttribute(SPIRV_BACKEND_SERVICE_FUN_NAME)
          .isValid())
    return;
 
  const DISubprogram *SP = MF->getFunction().getSubprogram();
  if (!SP || !SP->isDefinition())
    return;
 
  // DebugFunctionDefinition is emitted after the last function-level
  // OpVariable. If there are none, it is emitted after the entry OpLabel.
  LastFunctionOpVariable =
      findLastFunctionOpVariableDeclaration(*MF, *CurrentMAI);
 
  analyzeDebugRecords(*MF);
}
 
void SPIRVNonSemanticDebugHandler::tryEmitDebugFunctionDefinition(
    SPIRV::ModuleAnalysisInfo &MAI) {
  if (DebugFunctionDefinitionEmitted || !GlobalNSDIEnabled)
    return;
 
  assert(CurrentMF && "no current MachineFunction");
  const Function &F = CurrentMF->getFunction();
  const DISubprogram *SP = F.getSubprogram();
  if (!SP || !SP->isDefinition())
    return;
 
  auto DFIt = DebugScopeRegs.find(SP);
  if (DFIt == DebugScopeRegs.end())
    return;
 
  MCRegister OpFunctionReg = MAI.getGlobalObjReg(&F);
  if (!OpFunctionReg.isValid())
    return;
 
  emitDebugFunctionDefinition(DFIt->second, OpFunctionReg, MAI);
  DebugFunctionDefinitionEmitted = true;
}
 
void SPIRVNonSemanticDebugHandler::beginFunctionImpl(
    const MachineFunction *MF) {
  preparePerFunctionDebug(MF);
}
 
void SPIRVNonSemanticDebugHandler::endFunctionImpl(const MachineFunction *MF) {
  (void)MF;
  resetPerFunctionDebugState();
}
 
void SPIRVNonSemanticDebugHandler::beginInstruction(const MachineInstr *MI) {
  assert(CurMI == nullptr && "CurMI must be null");
  CurMI = MI;
 
  if (!DebugFunctionDefinitionEmitted)
    return;
 
  emitAnalyzedRecords(MI);
 
  std::optional<const MachineInstr *> Target = resolveDebugLocTarget(MI);
  if (!Target)
    return;
 
  (void)emitDebugScopeForInstruction(*Target);
  emitDebugLineForInstruction(*Target);
}
 
// The register that holds the variable's address in \p MI, or std::nullopt
// when \p MI is not a declare this backend can describe.
//
// The spec requires DebugDeclare's Variable operand to be "the <id> of an
// OpVariable instruction that defines the local variable". MIR has no
// DBG_DECLARE, so what this looks for is an indirect DBG_VALUE whose location
// register an OpVariable defines.
static std::optional<Register>
getDebugDeclareStorageReg(const MachineInstr &MI) {
  // #dbg_declare is an indirect DBG_VALUE in MIR; #dbg_value is normally a
  // direct one except for the variadic case.
  if (!MI.isIndirectDebugValue())
    return std::nullopt;
 
  // A variadic #dbg_value becomes DBG_VALUE $noreg, 0, ... which is indirect
  // too, and $noreg is not virtual.
  Register LocReg = MI.getDebugOperand(0).getReg();
  if (!LocReg.isVirtual())
    return std::nullopt;
 
  // DebugDeclare can only encode the address of an OpVariable.
  // Other legitimate #dbg_declare cannot be encoded.
  // Examples: an access chain for a field, an OpFunctionParameter for a byval
  // argument, or a module-scope constant for a null or fixed address.
 
  // LocReg may also have no def at all: erasing dead storage leaves the
  // DBG_VALUE pointing at an undefined register. MachineVerifier permits that
  // because LiveDebugVariables normally clears it, but this pipeline has no
  // register allocation, so LiveDebugVariables never runs.
  const MachineInstr *Def = MI.getMF()->getRegInfo().getUniqueVRegDef(LocReg);
  if (!Def || Def->getOpcode() != SPIRV::OpVariable)
    return std::nullopt;
 
  return LocReg;
}
 
void SPIRVNonSemanticDebugHandler::emitDebugBinding(
    SPIRV::NonSemanticExtInst::NonSemanticExtInst Opcode,
    const MachineInstr *MI, MCRegister LocationReg) {
  assert(DebugFunctionDefinitionEmitted &&
         "DebugFunctionDefinition must be emitted");
  assert(CurrentMAI && "CurrentMAI must be set");
 
  auto VarRegOpt = lookupOptReg(DebugLocalVariableRegs, MI->getDebugVariable());
  if (!VarRegOpt)
    return;
 
  auto ExprRegOpt = lookupOptReg(DebugExpressionRegs, MI->getDebugExpression());
  if (!ExprRegOpt)
    return;
 
  if (!emitDebugScopeForInstruction(MI))
    return;
  emitDebugLineForInstruction(MI);
 
  SPIRV::ModuleAnalysisInfo &MAI = *CurrentMAI;
  MCRegister VoidTypeReg = getOrEmitOpTypeVoidReg(MAI);
  MCRegister ExtInstSetReg = MAI.getExtInstSetReg(NSSet);
  emitExtInst(Opcode, VoidTypeReg, ExtInstSetReg,
              {*VarRegOpt, LocationReg, *ExprRegOpt}, MAI);
}
 
// The scalar type and value of the constant \p MI assigns, or nullopt when
// this backend cannot name it.
static std::optional<std::pair<const DIBasicType *, uint64_t>>
getConstantDbgValueBits(const MachineInstr &MI) {
  if (!MI.isNonListDebugValue() || MI.isIndirectDebugValue())
    return std::nullopt;
 
  const MachineOperand &Value = MI.getDebugOperand(0);
  if (!Value.isImm() && !Value.isCImm() && !Value.isFPImm())
    return std::nullopt;
 
  const DILocalVariable *LV = MI.getDebugVariable();
  const DIBasicType *BT = LV ? stripToScalarType(LV->getType()) : nullptr;
  if (!BT)
    return std::nullopt;
 
  uint64_t Bits;
  if (Value.isImm())
    Bits = constantBits(static_cast<uint64_t>(Value.getImm()), BT);
  else if (Value.isCImm())
    Bits = constantBits(Value.getCImm()->getValue(), BT);
  else
    Bits = constantBits(Value.getFPImm()->getValueAPF().bitcastToAPInt(), BT);
  return std::make_pair(BT, Bits);
}
 
std::optional<MCRegister> SPIRVNonSemanticDebugHandler::getConstantValueReg(
    const MachineInstr &MI) const {
  std::optional<std::pair<const DIBasicType *, uint64_t>> Const =
      getConstantDbgValueBits(MI);
  if (!Const)
    return std::nullopt;
 
  auto It = ConstantValueRegs.find(*Const);
  if (It == ConstantValueRegs.end() || !It->second.isValid())
    return std::nullopt;
  return It->second;
}
 
static std::optional<Register> getDebugValueReg(const MachineInstr &MI) {
  if (!MI.isNonListDebugValue() || MI.isIndirectDebugValue())
    return std::nullopt;
 
  const MachineOperand &Value = MI.getDebugOperand(0);
  if (!Value.isReg())
    return std::nullopt;
 
  Register ValueReg = Value.getReg();
  if (!ValueReg.isVirtual())
    return std::nullopt;
 
  const MachineInstr *Def = MI.getMF()->getRegInfo().getUniqueVRegDef(ValueReg);
  if (!Def || (Def->isPseudo() && !Def->isPHI()) || Def->isMetaInstruction() ||
      Def->getNumOperands() == 0 || !Def->getOperand(0).isReg() ||
      !Def->getOperand(0).isDef() || Def->getOperand(0).getReg() != ValueReg)
    return std::nullopt;
 
  return ValueReg;
}
 
static bool isMergeInstruction(unsigned Opcode) {
  return Opcode == SPIRV::OpSelectionMerge || Opcode == SPIRV::OpLoopMerge ||
         Opcode == SPIRV::OpLoopControlINTEL;
}
 
// Whether \p MI becomes a SPIR-V instruction in the output.
static bool isEmitted(const MachineInstr *MI, SPIRV::ModuleAnalysisInfo &MAI) {
  return !MI->isMetaInstruction() && !MAI.getSkipEmission(MI);
}
 
static bool isDebugLocTarget(const MachineInstr *MI,
                             SPIRV::ModuleAnalysisInfo &MAI) {
  if (!isEmitted(MI, MAI))
    return false;
  switch (MI->getOpcode()) {
  case SPIRV::OpFunction:
  case SPIRV::OpFunctionParameter:
  case SPIRV::OpFunctionEnd:
  case SPIRV::OpLabel:
  case TargetOpcode::PHI:
    return false;
  default:
    return true;
  }
}
 
static const MachineInstr *
findAdjacentEmittedInstruction(const MachineInstr *MI,
                               SPIRV::ModuleAnalysisInfo &MAI, bool Forward) {
  for (const MachineInstr *Adj = Forward ? MI->getNextNode()
                                         : MI->getPrevNode();
       Adj; Adj = Forward ? Adj->getNextNode() : Adj->getPrevNode()) {
    if (!isEmitted(Adj, MAI))
      continue;
    return Adj;
  }
  return nullptr;
}
 
std::optional<const MachineInstr *>
SPIRVNonSemanticDebugHandler::resolveDebugLocTarget(const MachineInstr *MI) {
  assert(CurrentMAI && "CurrentMAI must be set");
  SPIRV::ModuleAnalysisInfo &MAI = *CurrentMAI;
 
  // Structural opcodes don't require a DebugLine/DebugScope, other opcodes
  // might have already been emitted in the module scope.
  if (!isDebugLocTarget(MI, MAI))
    return std::nullopt;
 
  // DebugLine/DebugScope can be emitted before a merge instruction, but not
  // after it (nothing may sit between the merge and its terminator). We can
  // use either the merge's or the terminator's debug info; we emit the
  // terminator's one.
  const MachineInstr *Prev = findAdjacentEmittedInstruction(MI, MAI, false);
  if (Prev && isMergeInstruction(Prev->getOpcode()))
    return std::nullopt;
 
  if (isMergeInstruction(MI->getOpcode())) {
    // Use the terminator's debug info; when we reach it later, the check
    // above skips it.
    MI = findAdjacentEmittedInstruction(MI, MAI, true);
    assert(MI && "Merge instruction must be followed by a terminator");
    // The assert is compiled out in a release build, and returning MI there
    // would give an engaged optional holding null.
    if (!MI)
      return std::nullopt;
  }
 
  return MI;
}
 
void SPIRVNonSemanticDebugHandler::resolveDebugRecord(
    const MachineInstr &MI, const MachineInstr *LastEmitted,
    const MachineDominatorTree &DomTree) {
  SPIRV::ModuleAnalysisInfo &MAI = *CurrentMAI;
  const MachineFunction &MF = *MI.getMF();
 
  // A record sits at its own position, except in a merge region: nothing may
  // be emitted between a merge and its terminator, so it belongs ahead of the
  // merge.
  const MachineInstr *Anchor =
      LastEmitted && isMergeInstruction(LastEmitted->getOpcode()) ? LastEmitted
                                                                  : &MI;
 
  // A #dbg_declare reaches Machine IR as an indirect DBG_VALUE. Its storage is
  // an OpVariable in the entry block, so it is in the output by the time any
  // record naming it is reached.
  if (std::optional<Register> LocReg = getDebugDeclareStorageReg(MI)) {
    MCRegister StorageReg = MAI.getRegisterAlias(&MF, *LocReg);
    if (StorageReg.isValid())
      placeRecord(SPIRV::NonSemanticExtInst::DebugDeclare, MI, StorageReg,
                  Anchor);
    return;
  }
 
  if (std::optional<MCRegister> ConstReg = getConstantValueReg(MI)) {
    placeRecord(SPIRV::NonSemanticExtInst::DebugValue, MI, *ConstReg, Anchor);
    return;
  }
 
  std::optional<Register> ValReg = getDebugValueReg(MI);
  if (!ValReg)
    return;
  MCRegister ValueReg = MAI.getRegisterAlias(&MF, *ValReg);
  if (!ValueReg.isValid())
    return;
 
  // NonSemantic.Shader.DebugInfo states that "Forward references are not
  // allowed, to be compliant with SPV_KHR_non_semantic_info", so the id has to
  // be in the output already. A module section precedes every function body.
  //
  // For anything else, SPIR-V requires a definition in a function block to
  // dominate a non-phi use, and requires a block to precede every block it
  // dominates, so a dominating definition is also one already printed. A
  // record naming a definition that does not dominate it is dropped.
  const MachineInstr *Def = MF.getRegInfo().getUniqueVRegDef(*ValReg);
  if (ModuleScopeIds.contains(ValueReg) ||
      (isEmitted(Def, MAI) && DomTree.dominates(Def, &MI)))
    placeRecord(SPIRV::NonSemanticExtInst::DebugValue, MI, ValueReg, Anchor);
}
 
void SPIRVNonSemanticDebugHandler::analyzeDebugRecords(
    const MachineFunction &MF) {
  assert(CurrentMAI && "CurrentMAI must be set");
 
  // Built on the first record rather than required as an analysis pass, which
  // would build a tree for every SPIR-V compilation.
  std::optional<MachineDominatorTree> DomTree;
 
  for (const MachineBasicBlock &MBB : MF) {
    const MachineInstr *LastEmitted = nullptr;
    for (const MachineInstr &MI : MBB) {
      if (MI.isDebugValueLike()) {
        if (!DomTree)
          DomTree.emplace(const_cast<MachineFunction &>(MF));
        resolveDebugRecord(MI, LastEmitted, *DomTree);
      }
 
      if (isEmitted(&MI, *CurrentMAI))
        LastEmitted = &MI;
    }
  }
}
 
void SPIRVNonSemanticDebugHandler::placeRecord(
    SPIRV::NonSemanticExtInst::NonSemanticExtInst Opcode,
    const MachineInstr &MI, MCRegister LocationReg,
    const MachineInstr *Anchor) {
  Records[Anchor].push_back({&MI, Opcode, LocationReg});
}
 
void SPIRVNonSemanticDebugHandler::emitAnalyzedRecords(
    const MachineInstr *Anchor) {
  auto It = Records.find(Anchor);
  if (It == Records.end())
    return;
  for (const DebugRecord &R : It->second)
    emitDebugBinding(R.Opcode, R.MI, R.LocationReg);
}
 
bool SPIRVNonSemanticDebugHandler::emitDebugScopeForInstruction(
    const MachineInstr *MI) {
  assert(DebugFunctionDefinitionEmitted &&
         "DebugFunctionDefinition must be emitted");
  assert(CurrentMAI && "CurrentMAI must be set");
 
  // The region is implicitly closed at each basic block boundary, so a
  // LastScopeMI from another block must be dropped before it is read below:
  // the new block needs its own DebugScope, and has no region left to close.
  if (LastScopeMI && MI->getParent() != LastScopeMI->getParent())
    LastScopeMI = nullptr;
 
  SPIRV::ModuleAnalysisInfo &MAI = *CurrentMAI;
  MCRegister VoidTypeReg = getOrEmitOpTypeVoidReg(MAI);
  MCRegister ExtInstSetReg = MAI.getExtInstSetReg(NSSet);
 
  const DILocation *CurDL = MI->getDebugLoc().get();
  if (!CurDL) {
    // No location for the current instruction.
    if (LastScopeMI) {
      // Close the current DebugScope region.
      emitExtInst(SPIRV::NonSemanticExtInst::DebugNoScope, VoidTypeReg,
                  ExtInstSetReg, {}, MAI);
      LastScopeMI = nullptr;
    }
    return true;
  }
 
  const DIScope *CurScope = CurDL->getScope();
  const DILocation *CurInlinedAt = CurDL->getInlinedAt();
 
  if (LastScopeMI) {
    const DILocation *LastDL = LastScopeMI->getDebugLoc().get();
    if (LastDL->getScope() == CurScope &&
        LastDL->getInlinedAt() == CurInlinedAt)
      return true;
  }
 
  EmitResult<MCRegister> CurScopeRes = resolveScope(CurScope);
  if (!CurScopeRes)
    return false;
 
  SmallVector<MCRegister, 2> Ops{*CurScopeRes.Value};
  if (CurInlinedAt) {
    // If the global emission did not include this inlined-at case, we skip it.
    MCRegister InlinedReg = DebugInlinedAtRegs.lookup(CurInlinedAt);
    if (!InlinedReg.isValid())
      return false;
    Ops.push_back(InlinedReg);
  }
 
  // A new DebugScope region is needed.
  emitExtInst(SPIRV::NonSemanticExtInst::DebugScope, VoidTypeReg, ExtInstSetReg,
              Ops, MAI);
 
  LastScopeMI = MI;
  return true;
}
 
void SPIRVNonSemanticDebugHandler::emitDebugLineForInstruction(
    const MachineInstr *MI) {
  assert(DebugFunctionDefinitionEmitted &&
         "DebugFunctionDefinition must be emitted");
  assert(CurrentMAI && "CurrentMAI must be set");
 
  // The region is implicitly closed at each basic block boundary, so a
  // LastLineMI from another block must be dropped before it is read below:
  // the new block needs its own DebugLine, and has no region left to close.
  if (LastLineMI && MI->getParent() != LastLineMI->getParent())
    LastLineMI = nullptr;
 
  SPIRV::ModuleAnalysisInfo &MAI = *CurrentMAI;
  MCRegister VoidTypeReg = getOrEmitOpTypeVoidReg(MAI);
  MCRegister ExtInstSetReg = MAI.getExtInstSetReg(NSSet);
 
  const DILocation *DL = MI->getDebugLoc().get();
  if (!DL) {
    // No location for the current instruction
    if (LastLineMI) {
      // Close the current DebugLine region.
      emitExtInst(SPIRV::NonSemanticExtInst::DebugNoLine, VoidTypeReg,
                  ExtInstSetReg, {}, MAI);
      LastLineMI = nullptr;
    }
    // No DebugLine region to close.
    return;
  }
 
  // At this point, there is a location for the current instruction.
  // If it matches the last emitted DebugLine, no new DebugLine region is
  // needed. Otherwise, emit a new DebugLine region and update LastLineMI.
 
  MCRegister FileStrReg = getCachedScopePathOpStringReg(
      DL->getScope(), /*UseEmptyPathIfNullScope=*/true);
  unsigned Line = DL->getLine();
  unsigned Col = DL->getColumn();
 
  unsigned I32TypeId = CachedOpTypeInt32Reg.id();
  MCRegister SrcReg = DebugSourceRegByFileStr.lookup(FileStrReg.id());
  MCRegister LineReg = ScalarConstantCache.lookup({I32TypeId, Line});
  MCRegister ColStartReg = ScalarConstantCache.lookup({I32TypeId, Col});
  MCRegister ColEndReg = ScalarConstantCache.lookup({I32TypeId, Col + 1});
 
  // The elements of each collected DILocation (DebugSource, line/column
  // constants) are pre-emitted from LLVM-IR instruction !dbg attachments and
  // debug-program records; MIR is expected to reuse those same locations (or
  // carry none). A lookup miss means codegen attached a source position whose
  // elements were never pre-emitted, and debug-line emission is skipped.
  if (!SrcReg.isValid() || !LineReg.isValid() || !ColStartReg.isValid() ||
      !ColEndReg.isValid())
    return;
 
  // Current location matches the last emitted DebugLine region.
  if (LastLineMI && MI->getDebugLoc() == LastLineMI->getDebugLoc())
    return;
 
  // A new DebugLine region is needed.
  emitExtInst(SPIRV::NonSemanticExtInst::DebugLine, VoidTypeReg, ExtInstSetReg,
              {SrcReg, LineReg, LineReg, ColStartReg, ColEndReg}, MAI);
 
  LastLineMI = MI;
}
 
void SPIRVNonSemanticDebugHandler::endInstruction() {
  const MachineInstr *MI = CurMI;
  CurMI = nullptr;
 
  if (!MI || !GlobalNSDIEnabled || !CurrentMF)
    return;
 
  if (DebugFunctionDefinitionEmitted || MI != LastFunctionOpVariable)
    return;
 
  // If this is the last function-level OpVariable, emit the
  // DebugFunctionDefinition. Otherwise, we had already done it before right
  // after the OpLabel (see notifyEntryLabelEmitted).
  assert(CurrentMAI && "CurrentMAI must be set");
  tryEmitDebugFunctionDefinition(*CurrentMAI);
}
 
void SPIRVNonSemanticDebugHandler::notifyEntryLabelEmitted(
    const MachineFunction &MF) {
  if (!GlobalNSDIEnabled || DebugFunctionDefinitionEmitted || !CurrentMF)
    return;
 
  assert(CurrentMF == &MF &&
         "notification does not match the current MachineFunction");
 
  if (LastFunctionOpVariable)
    return;
 
  // If there are no function-level OpVariables, emit the
  // DebugFunctionDefinition. Otherwise, DebugFunctionDefinition is emitted
  // after the last OpVariable (see endInstruction).
  tryEmitDebugFunctionDefinition(*CurrentMAI);
}
 
void SPIRVNonSemanticDebugHandler::collectDebugExpressions(
    const SPIRV::ModuleAnalysisInfo &MAI,
    SetVector<const DIExpression *> &Out) const {
  for (const MachineInstr *MI : MAI.DebugValueMIs)
    Out.insert(MI->getDebugExpression());
}
 
void SPIRVNonSemanticDebugHandler::emitNonSemanticGlobalDebugInfo(
    SPIRV::ModuleAnalysisInfo &MAI) {
  if (GlobalDIEmitted)
    return;
 
  GlobalDIEmitted = true;
 
  if (CompileUnits.empty()) {
    GlobalNSDIEnabled = false;
    return;
  }
 
  // Retrieve the ext inst set register allocated by prepareModuleOutput().
  MCRegister ExtInstSetReg = MAI.getExtInstSetReg(NSSet);
  if (!ExtInstSetReg.isValid()) {
    GlobalNSDIEnabled = false;
    return;
  }
 
#ifndef NDEBUG
  assert(NonSemanticOpStringsSectionEmitted &&
         "emitNonSemanticDebugStrings() must run before "
         "emitNonSemanticGlobalDebugInfo()");
#endif
 
  CurrentMAI = &MAI;
 
  MCRegister VoidTypeReg = getOrEmitOpTypeVoidReg(MAI);
  MCRegister I32TypeReg = getOrEmitOpTypeInt32Reg(MAI);
 
  CachedDebugInfoNoneReg = emitExtInst(SPIRV::NonSemanticExtInst::DebugInfoNone,
                                       VoidTypeReg, ExtInstSetReg, {}, MAI);
 
  // Emit integer constants shared across all NSDI instructions. The constant
  // cache ensures each value is emitted at most once even when referenced from
  // multiple instructions. All constants are pre-emitted before any DebugSource
  // so that the output order is: constants, then
  // DebugSource+DebugCompilationUnit pairs. This keeps OpConstant instructions
  // grouped before the OpExtInst instructions.
 
  // The Version operand of DebugCompilationUnit is the version of the
  // NonSemantic.Shader.DebugInfo instruction set, which is 100 for
  // "NonSemantic.Shader.DebugInfo.100" (NonSemanticShaderDebugInfo100Version).
  MCRegister DebugInfoVersionReg = emitOpConstantI32(100, I32TypeReg, MAI);
  MCRegister DwarfVersionReg =
      emitOpConstantI32(static_cast<uint32_t>(DwarfVersion), I32TypeReg, MAI);
 
  // Pre-emit source language constants for all compile units before entering
  // the DebugSource loop.
  SmallVector<MCRegister> SrcLangRegs =
      map_to_vector(CompileUnits, [&](const CompileUnitInfo &Info) {
        return emitOpConstantI32(Info.SpirvSourceLanguage, I32TypeReg, MAI);
      });
 
  // Emit DebugSource and DebugCompilationUnit for each compile unit.
  for (auto [Info, SrcLangReg] : llvm::zip(CompileUnits, SrcLangRegs)) {
    MCRegister FileStrReg = ScopeToPathOpStringReg.lookup(Info.TheCU);
    assert(FileStrReg.isValid() &&
           "CU path OpString must be emitted in emitNonSemanticDebugStrings");
    MCRegister DebugSourceReg = getOrEmitDebugSourceForFileStrReg(
        FileStrReg, VoidTypeReg, ExtInstSetReg, MAI);
    MCRegister CUDbgReg = emitExtInst(
        SPIRV::NonSemanticExtInst::DebugCompilationUnit, VoidTypeReg,
        ExtInstSetReg,
        {DebugInfoVersionReg, DwarfVersionReg, DebugSourceReg, SrcLangReg},
        MAI);
    if (Info.TheCU)
      DebugScopeRegs[Info.TheCU] = CUDbgReg;
  }
 
  for (const DIScope *S :
       concat<const DIScope *const>(LexicalBlocks, DebugTypes, Subprograms))
    getOrCreateDebugScope(S);
 
  // Emit DebugLocalVariable after DebugFunction and their lexical blocks so the
  // Parent operand can resolve. Record the ids for DebugDeclare.
  for (const DILocalVariable *LV : LocalVariables)
    if (auto LVReg = emitDebugLocalVariable(LV, VoidTypeReg, I32TypeReg,
                                            ExtInstSetReg, MAI))
      DebugLocalVariableRegs[LV] = *LVReg;
 
  // Opcodes like DebugDeclare are part of the function body, but
  // DebugExpression is not. For such opcodes, we collect the expressions
  // directly from the MIR to avoid inconsistencies with those in the LLVM IR
  // module.
  SetVector<const DIExpression *> Expressions;
  collectDebugExpressions(MAI, Expressions);
  for (const DIExpression *Expr : Expressions)
    if (auto ExprReg = emitDebugExpression(Expr, VoidTypeReg, I32TypeReg,
                                           ExtInstSetReg, MAI))
      DebugExpressionRegs[Expr] = *ExprReg;
 
  // Emit DebugGlobalVariable for each collected DIGlobalVariable.
  for (const auto &[GV, Info] : GlobalVariableDebugInfoMap)
    emitDebugGlobalVariable(GV, Info, VoidTypeReg, I32TypeReg, ExtInstSetReg,
                            MAI);
 
  // Emit DebugInlinedAt allowing recursive inlining.
  for (const DILocation *DL : UniqueDebugLocations)
    if (const DILocation *IA = DL->getInlinedAt())
      getOrEmitDebugInlinedAt(IA, VoidTypeReg, I32TypeReg, ExtInstSetReg, MAI);
 
  // Repeating the lookups emitDebugBinding() performs emits a type and a
  // constant only for an assignment that will reach a DebugValue.
  for (const MachineInstr *MI : MAI.DebugValueMIs) {
    std::optional<std::pair<const DIBasicType *, uint64_t>> Const =
        getConstantDbgValueBits(*MI);
    if (!Const)
      continue;
    if (!DebugLocalVariableRegs.contains(MI->getDebugVariable()) ||
        !DebugExpressionRegs.contains(MI->getDebugExpression()))
      continue;
    auto [It, Inserted] = ConstantValueRegs.try_emplace(*Const, MCRegister());
    if (Inserted)
      It->second = findOrEmitScalarConstant(Const->first, Const->second, MAI);
    if (!It->second.isValid())
      ConstantValueRegs.erase(It);
  }
 
  for (const DILocation *DL : UniqueDebugLocations) {
    emitOpConstantI32(DL->getLine(), I32TypeReg, MAI);
    emitOpConstantI32(DL->getColumn(), I32TypeReg, MAI);
    emitOpConstantI32(DL->getColumn() + 1, I32TypeReg, MAI);
    MCRegister FileStrReg =
        getCachedScopePathOpStringReg(DL->getScope(),
                                      /*UseEmptyPathIfNullScope=*/true);
    getOrEmitDebugSourceForFileStrReg(FileStrReg, VoidTypeReg, ExtInstSetReg,
                                      MAI);
  }
 
  GlobalNSDIEnabled = true;
}
 
SmallString<128>
SPIRVNonSemanticDebugHandler::getDebugFullPath(const DIScope *Scope) const {
  SmallString<128> Out;
  if (!Scope)
    return Out;
  StringRef Filename = Scope->getFilename();
  const auto Style = sys::path::Style::native;
  if (sys::path::is_absolute(Filename, Style))
    Out.assign(Filename.begin(), Filename.end());
  else {
    StringRef Dir = Scope->getDirectory();
    Out.assign(Dir.begin(), Dir.end());
    sys::path::append(Out, Style, Filename);
  }
  return Out;
}
 
MCRegister SPIRVNonSemanticDebugHandler::getOrEmitDebugSourceForFileStrReg(
    MCRegister FileStrReg, MCRegister VoidTypeReg, MCRegister ExtInstSetReg,
    SPIRV::ModuleAnalysisInfo &MAI) {
  const unsigned Key = FileStrReg.id();
  auto It = DebugSourceRegByFileStr.find(Key);
  if (It != DebugSourceRegByFileStr.end())
    return It->second;
 
  MCRegister DS = emitExtInst(SPIRV::NonSemanticExtInst::DebugSource,
                              VoidTypeReg, ExtInstSetReg, {FileStrReg}, MAI);
  DebugSourceRegByFileStr[Key] = DS;
  return DS;
}