Esempio n. 1
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DICompileUnit *DIBuilder::createCompileUnit(
    unsigned Lang, StringRef Filename, StringRef Directory, StringRef Producer,
    bool isOptimized, StringRef Flags, unsigned RunTimeVer, StringRef SplitName,
    DebugEmissionKind Kind, uint64_t DWOId, bool EmitDebugInfo) {

  assert(((Lang <= dwarf::DW_LANG_Fortran08 && Lang >= dwarf::DW_LANG_C89) ||
          (Lang <= dwarf::DW_LANG_hi_user && Lang >= dwarf::DW_LANG_lo_user)) &&
         "Invalid Language tag");
  assert(!Filename.empty() &&
         "Unable to create compile unit without filename");

  assert(!CUNode && "Can only make one compile unit per DIBuilder instance");
  CUNode = DICompileUnit::getDistinct(
      VMContext, Lang, DIFile::get(VMContext, Filename, Directory), Producer,
      isOptimized, Flags, RunTimeVer, SplitName, Kind, nullptr,
      nullptr, nullptr, nullptr, nullptr, DWOId);

  // Create a named metadata so that it is easier to find cu in a module.
  // Note that we only generate this when the caller wants to actually
  // emit debug information. When we are only interested in tracking
  // source line locations throughout the backend, we prevent codegen from
  // emitting debug info in the final output by not generating llvm.dbg.cu.
  if (EmitDebugInfo) {
    NamedMDNode *NMD = M.getOrInsertNamedMetadata("llvm.dbg.cu");
    NMD->addOperand(CUNode);
  }

  trackIfUnresolved(CUNode);
  return CUNode;
}
Esempio n. 2
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/// createVariable - Create a new descriptor for the specified variable.
DIVariable DIBuilder::createLocalVariable(unsigned Tag, DIDescriptor Scope,
                                          StringRef Name, DIFile File,
                                          unsigned LineNo, DIType Ty,
                                          bool AlwaysPreserve, unsigned Flags,
                                          unsigned ArgNo) {
  Value *Elts[] = {
    GetTagConstant(VMContext, Tag),
    getNonCompileUnitScope(Scope),
    MDString::get(VMContext, Name),
    File,
    ConstantInt::get(Type::getInt32Ty(VMContext), (LineNo | (ArgNo << 24))),
    Ty,
    ConstantInt::get(Type::getInt32Ty(VMContext), Flags),
    Constant::getNullValue(Type::getInt32Ty(VMContext))
  };
  MDNode *Node = MDNode::get(VMContext, Elts);
  if (AlwaysPreserve) {
    // The optimizer may remove local variable. If there is an interest
    // to preserve variable info in such situation then stash it in a
    // named mdnode.
    DISubprogram Fn(getDISubprogram(Scope));
    NamedMDNode *FnLocals = getOrInsertFnSpecificMDNode(M, Fn);
    FnLocals->addOperand(Node);
  }
  return DIVariable(Node);
}
Esempio n. 3
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void LLVMAddNamedMetadataOperand2(LLVMModuleRef M, const char *name,
                                  LLVMMetadataRef Val) {
  NamedMDNode *N = unwrap(M)->getOrInsertNamedMetadata(name);
  if (!N)
    return;
  if (!Val)
    return;
  N->addOperand(unwrap<MDNode>(Val));
}
Esempio n. 4
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static void
ModuleMetaSet(Module *module, StringRef MetaName, StringRef ValueStr) {
  NamedMDNode *node = module->getNamedMetadata(MetaName);
  if (node)
    module->eraseNamedMetadata(node);
  node = module->getOrInsertNamedMetadata(MetaName);
  MDString *value = MDString::get(module->getContext(), ValueStr);
  node->addOperand(MDNode::get(module->getContext(),
                   makeArrayRef(static_cast<Value*>(value))));
}
Esempio n. 5
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/// Insert all of the named MDNodes in Src into the Dest module.
void IRLinker::linkNamedMDNodes() {
  const NamedMDNode *SrcModFlags = SrcM->getModuleFlagsMetadata();
  for (const NamedMDNode &NMD : SrcM->named_metadata()) {
    // Don't link module flags here. Do them separately.
    if (&NMD == SrcModFlags)
      continue;
    NamedMDNode *DestNMD = DstM.getOrInsertNamedMetadata(NMD.getName());
    // Add Src elements into Dest node.
    for (const MDNode *Op : NMD.operands())
      DestNMD->addOperand(Mapper.mapMDNode(*Op));
  }
}
Esempio n. 6
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/// linkNamedMDNodes - Insert all of the named mdnodes in Src into the Dest
/// module.
void ModuleLinker::linkNamedMDNodes() {
  const NamedMDNode *SrcModFlags = SrcM->getModuleFlagsMetadata();
  for (Module::const_named_metadata_iterator I = SrcM->named_metadata_begin(),
       E = SrcM->named_metadata_end(); I != E; ++I) {
    // Don't link module flags here. Do them separately.
    if (&*I == SrcModFlags) continue;
    NamedMDNode *DestNMD = DstM->getOrInsertNamedMetadata(I->getName());
    // Add Src elements into Dest node.
    for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
      DestNMD->addOperand(MapValue(I->getOperand(i), ValueMap,
                                   RF_None, &TypeMap));
  }
}
Esempio n. 7
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DICompileUnit DIBuilder::createCompileUnit(unsigned Lang, StringRef Filename,
                                           StringRef Directory,
                                           StringRef Producer, bool isOptimized,
                                           StringRef Flags, unsigned RunTimeVer,
                                           StringRef SplitName,
                                           DebugEmissionKind Kind,
                                           bool EmitDebugInfo) {

  assert(((Lang <= dwarf::DW_LANG_OCaml && Lang >= dwarf::DW_LANG_C89) ||
          (Lang <= dwarf::DW_LANG_hi_user && Lang >= dwarf::DW_LANG_lo_user)) &&
         "Invalid Language tag");
  assert(!Filename.empty() &&
         "Unable to create compile unit without filename");
  Value *TElts[] = {HeaderBuilder::get(DW_TAG_base_type).get(VMContext)};
  TempEnumTypes = MDNode::getTemporary(VMContext, TElts);

  TempRetainTypes = MDNode::getTemporary(VMContext, TElts);

  TempSubprograms = MDNode::getTemporary(VMContext, TElts);

  TempGVs = MDNode::getTemporary(VMContext, TElts);

  TempImportedModules = MDNode::getTemporary(VMContext, TElts);

  Value *Elts[] = {HeaderBuilder::get(dwarf::DW_TAG_compile_unit)
                       .concat(Lang)
                       .concat(Producer)
                       .concat(isOptimized)
                       .concat(Flags)
                       .concat(RunTimeVer)
                       .concat(SplitName)
                       .concat(Kind)
                       .get(VMContext),
                   createFilePathPair(VMContext, Filename, Directory),
                   TempEnumTypes, TempRetainTypes, TempSubprograms, TempGVs,
                   TempImportedModules};

  MDNode *CUNode = MDNode::get(VMContext, Elts);

  // Create a named metadata so that it is easier to find cu in a module.
  // Note that we only generate this when the caller wants to actually
  // emit debug information. When we are only interested in tracking
  // source line locations throughout the backend, we prevent codegen from
  // emitting debug info in the final output by not generating llvm.dbg.cu.
  if (EmitDebugInfo) {
    NamedMDNode *NMD = M.getOrInsertNamedMetadata("llvm.dbg.cu");
    NMD->addOperand(CUNode);
  }

  return DICompileUnit(CUNode);
}
Esempio n. 8
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/// Insert all of the named MDNodes in Src into the Dest module.
void IRLinker::linkNamedMDNodes() {
  const NamedMDNode *SrcModFlags = SrcM.getModuleFlagsMetadata();
  for (const NamedMDNode &NMD : SrcM.named_metadata()) {
    // Don't link module flags here. Do them separately.
    if (&NMD == SrcModFlags)
      continue;
    NamedMDNode *DestNMD = DstM.getOrInsertNamedMetadata(NMD.getName());
    // Add Src elements into Dest node.
    for (const MDNode *op : NMD.operands())
      DestNMD->addOperand(MapMetadata(
          op, ValueMap, RF_MoveDistinctMDs | RF_NullMapMissingGlobalValues,
          &TypeMap, &GValMaterializer));
  }
}
Esempio n. 9
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/// createCompileUnit - A CompileUnit provides an anchor for all debugging
/// information generated during this instance of compilation.
void DIBuilder::createCompileUnit(unsigned Lang, StringRef Filename,
                                  StringRef Directory, StringRef Producer,
                                  bool isOptimized, StringRef Flags,
                                  unsigned RunTimeVer) {
  assert(((Lang <= dwarf::DW_LANG_Python && Lang >= dwarf::DW_LANG_C89) ||
          (Lang <= dwarf::DW_LANG_hi_user && Lang >= dwarf::DW_LANG_lo_user)) &&
         "Invalid Language tag");
  assert(!Filename.empty() &&
         "Unable to create compile unit without filename");
  Value *TElts[] = { GetTagConstant(VMContext, DW_TAG_base_type) };
  TempEnumTypes = MDNode::getTemporary(VMContext, TElts);
  Value *THElts[] = { TempEnumTypes };
  MDNode *EnumHolder = MDNode::get(VMContext, THElts);

  TempRetainTypes = MDNode::getTemporary(VMContext, TElts);
  Value *TRElts[] = { TempRetainTypes };
  MDNode *RetainHolder = MDNode::get(VMContext, TRElts);

  TempSubprograms = MDNode::getTemporary(VMContext, TElts);
  Value *TSElts[] = { TempSubprograms };
  MDNode *SPHolder = MDNode::get(VMContext, TSElts);

  TempGVs = MDNode::getTemporary(VMContext, TElts);
  Value *TVElts[] = { TempGVs };
  MDNode *GVHolder = MDNode::get(VMContext, TVElts);

  Value *Elts[] = {
    GetTagConstant(VMContext, dwarf::DW_TAG_compile_unit),
    Constant::getNullValue(Type::getInt32Ty(VMContext)),
    ConstantInt::get(Type::getInt32Ty(VMContext), Lang),
    MDString::get(VMContext, Filename),
    MDString::get(VMContext, Directory),
    MDString::get(VMContext, Producer),
    // Deprecate isMain field.
    ConstantInt::get(Type::getInt1Ty(VMContext), true), // isMain
    ConstantInt::get(Type::getInt1Ty(VMContext), isOptimized),
    MDString::get(VMContext, Flags),
    ConstantInt::get(Type::getInt32Ty(VMContext), RunTimeVer),
    EnumHolder,
    RetainHolder,
    SPHolder,
    GVHolder
  };
  TheCU = DICompileUnit(MDNode::get(VMContext, Elts));

  // Create a named metadata so that it is easier to find cu in a module.
  NamedMDNode *NMD = M.getOrInsertNamedMetadata("llvm.dbg.cu");
  NMD->addOperand(TheCU);
}
Esempio n. 10
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    CopyConnectedComponent(Module * dest_, Module * src_, llvmutil_Property copyGlobal_, void * data_, ValueToValueMapTy & VMap_)
    : dest(dest_), src(src_), copyGlobal(copyGlobal_), data(data_), VMap(VMap_), DI(NULL) {
        if(NamedMDNode * NMD = src->getNamedMetadata("llvm.module.flags")) {
            NamedMDNode * New = dest->getOrInsertNamedMetadata(NMD->getName());
            for (unsigned i = 0; i < NMD->getNumOperands(); i++) {
                New->addOperand(MapValue(NMD->getOperand(i), VMap));
            }
        }

        if(NamedMDNode * CUN = src->getNamedMetadata("llvm.dbg.cu")) {
            DI = new DIBuilder(*dest);
            DICompileUnit CU(CUN->getOperand(0));
            NCU = DI->createCompileUnit(CU.getLanguage(), CU.getFilename(), CU.getDirectory(), CU.getProducer(), CU.isOptimized(), CU.getFlags(), CU.getRunTimeVersion());
        }
    }
Esempio n. 11
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void Module::convertLibraryListToMetadata() const {
  if (LibraryList.size() == 0)
    return;
  // Get the DepLib node
  NamedMDNode *Node = getNamedMetadata("DepLibs");
  assert(Node && "DepLibs metadata node missing");
  // Erase all existing operands
  Node->dropAllReferences();
  // Add all libraries from the library list
  for (Module::lib_iterator I = lib_begin(), E = lib_end(); I != E; ++I) {
    MDString *value = MDString::get(getContext(), *I);
    Node->addOperand(MDNode::get(getContext(),
                                 makeArrayRef(static_cast<Value*>(value))));
  }
}
Esempio n. 12
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bool ReduceCrashingNamedMDOps::TestNamedMDOps(
    std::vector<const MDNode *> &NamedMDOps) {
  // Convert list to set for fast lookup...
  SmallPtrSet<const MDNode *, 32> OldMDNodeOps;
  for (unsigned i = 0, e = NamedMDOps.size(); i != e; ++i) {
    OldMDNodeOps.insert(NamedMDOps[i]);
  }

  outs() << "Checking for crash with only " << OldMDNodeOps.size();
  if (OldMDNodeOps.size() == 1)
    outs() << " named metadata operand: ";
  else
    outs() << " named metadata operands: ";

  ValueToValueMapTy VMap;
  Module *M = CloneModule(BD.getProgram(), VMap).release();

  // This is a little wasteful. In the future it might be good if we could have
  // these dropped during cloning.
  for (auto &NamedMD : BD.getProgram()->named_metadata()) {
    // Drop the old one and create a new one
    M->eraseNamedMetadata(M->getNamedMetadata(NamedMD.getName()));
    NamedMDNode *NewNamedMDNode =
        M->getOrInsertNamedMetadata(NamedMD.getName());
    for (MDNode *op : NamedMD.operands())
      if (OldMDNodeOps.count(op))
        NewNamedMDNode->addOperand(cast<MDNode>(MapMetadata(op, VMap)));
  }

  // Verify that this is still valid.
  legacy::PassManager Passes;
  Passes.add(createVerifierPass(/*FatalErrors=*/false));
  Passes.run(*M);

  // Try running on the hacked up program...
  if (TestFn(BD, M)) {
    // Make sure to use instruction pointers that point into the now-current
    // module, and that they don't include any deleted blocks.
    NamedMDOps.clear();
    for (const MDNode *Node : OldMDNodeOps)
      NamedMDOps.push_back(cast<MDNode>(*VMap.getMappedMD(Node)));

    BD.setNewProgram(M); // It crashed, keep the trimmed version...
    return true;
  }
  delete M; // It didn't crash, try something else.
  return false;
}
Esempio n. 13
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  bool
  SpecializationTable::addSpecialization(Function* parent,
      ConstSpecScheme scheme, Function* specialization, bool record)
  {
    assert(parent != NULL);
    assert(specialization != NULL);

    SpecTable::iterator cursor = this->specialized.find(specialization);
    //Specialization* spec = this->specialized.lookup(specialization->getName());
    if (cursor != this->specialized.end()) {
      return false;
    }

    Specialization* parentSpec = this->getSpecialization(parent);

    Specialization* spec = new Specialization();
    spec->handle = specialization;
    spec->parent = parentSpec;
    spec->args = scheme;
    this->specialized[specialization] = spec;

    //.GetOrCreateValue(specialization->getName(), spec);
    parentSpec->children.push_back(spec);

#if RECORD_IN_METADATA
    // Add the meta-data
    if (record) {
      NamedMDNode* md = this->module->getOrInsertNamedMetadata(
          "previrt::specializations");

      const unsigned int arg_count = parent->getArgumentList().size();
      Value** vals = new Value*[2 + arg_count];
      vals[0] = MDString::get(parent->getContext(), parent->getName());
      vals[1] = MDString::get(parent->getContext(), specialization->getName());
      for (unsigned int i = 0; i < parent->getArgumentList().size(); ++i) {
        vals[i+2] = scheme[i];
      }

      ArrayRef<Value*> ar_vals(vals, vals+2+arg_count);
      MDNode* nde = MDNode::get(this->module->getContext(), ar_vals);

      md->addOperand(nde);
    }
#endif /* RECORD_IN_METADATA */

    return true;
  }
Esempio n. 14
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void Module::addNeededRecord(StringRef DynFile, GlobalValue *GV) {
  if (DynFile.empty()) {
    // We never resolved this symbol, even after linking.
    // This should only happen in a shared object.
    // It is safe to ignore this symbol, and let the dynamic loader
    // figure out where it comes from.
    return;
  }
  std::string Key = NeededPrefix;
  Key += DynFile;
  // Get the node for this file.
  NamedMDNode *Node = getOrInsertNamedMetadata(Key);
  // Add this global value's name to the list.
  MDString *value = MDString::get(getContext(), GV->getName());
  Node->addOperand(MDNode::get(getContext(),
                   makeArrayRef(static_cast<Value*>(value))));
}
Esempio n. 15
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/// createCompileUnit - A CompileUnit provides an anchor for all debugging
/// information generated during this instance of compilation.
DICompileUnit DIBuilder::createCompileUnit(unsigned Lang, StringRef Filename,
                                           StringRef Directory,
                                           StringRef Producer, bool isOptimized,
                                           StringRef Flags, unsigned RunTimeVer,
                                           StringRef SplitName) {
  assert(((Lang <= dwarf::DW_LANG_Python && Lang >= dwarf::DW_LANG_C89) ||
          (Lang <= dwarf::DW_LANG_hi_user && Lang >= dwarf::DW_LANG_lo_user)) &&
         "Invalid Language tag");
  assert(!Filename.empty() &&
         "Unable to create compile unit without filename");
  Value *TElts[] = { GetTagConstant(VMContext, DW_TAG_base_type) };
  TempEnumTypes = MDNode::getTemporary(VMContext, TElts);

  TempRetainTypes = MDNode::getTemporary(VMContext, TElts);

  TempSubprograms = MDNode::getTemporary(VMContext, TElts);

  TempGVs = MDNode::getTemporary(VMContext, TElts);

  TempImportedModules = MDNode::getTemporary(VMContext, TElts);

  Value *Elts[] = {
    GetTagConstant(VMContext, dwarf::DW_TAG_compile_unit),
    createFilePathPair(VMContext, Filename, Directory),
    ConstantInt::get(Type::getInt32Ty(VMContext), Lang),
    MDString::get(VMContext, Producer),
    ConstantInt::get(Type::getInt1Ty(VMContext), isOptimized),
    MDString::get(VMContext, Flags),
    ConstantInt::get(Type::getInt32Ty(VMContext), RunTimeVer),
    TempEnumTypes,
    TempRetainTypes,
    TempSubprograms,
    TempGVs,
    TempImportedModules,
    MDString::get(VMContext, SplitName)
  };

  MDNode *CUNode = MDNode::get(VMContext, Elts);

  // Create a named metadata so that it is easier to find cu in a module.
  NamedMDNode *NMD = M.getOrInsertNamedMetadata("llvm.dbg.cu");
  NMD->addOperand(CUNode);

  return DICompileUnit(CUNode);
}
Esempio n. 16
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DICompileUnit *DIBuilder::createCompileUnit(
    unsigned Lang, StringRef Filename, StringRef Directory, StringRef Producer,
    bool isOptimized, StringRef Flags, unsigned RunTimeVer, StringRef SplitName,
    DebugEmissionKind Kind, bool EmitDebugInfo) {

    assert(((Lang <= dwarf::DW_LANG_Fortran08 && Lang >= dwarf::DW_LANG_C89) ||
            (Lang <= dwarf::DW_LANG_hi_user && Lang >= dwarf::DW_LANG_lo_user)) &&
           "Invalid Language tag");
    assert(!Filename.empty() &&
           "Unable to create compile unit without filename");

    // TODO: Once we make DICompileUnit distinct, stop using temporaries here
    // (just start with operands assigned to nullptr).
    TempEnumTypes = MDTuple::getTemporary(VMContext, None);
    TempRetainTypes = MDTuple::getTemporary(VMContext, None);
    TempSubprograms = MDTuple::getTemporary(VMContext, None);
    TempGVs = MDTuple::getTemporary(VMContext, None);
    TempImportedModules = MDTuple::getTemporary(VMContext, None);

    // TODO: Switch to getDistinct().  We never want to merge compile units based
    // on contents.
    DICompileUnit *CUNode = DICompileUnit::get(
                                VMContext, Lang, DIFile::get(VMContext, Filename, Directory), Producer,
                                isOptimized, Flags, RunTimeVer, SplitName, Kind, TempEnumTypes.get(),
                                TempRetainTypes.get(), TempSubprograms.get(), TempGVs.get(),
                                TempImportedModules.get());

    // Create a named metadata so that it is easier to find cu in a module.
    // Note that we only generate this when the caller wants to actually
    // emit debug information. When we are only interested in tracking
    // source line locations throughout the backend, we prevent codegen from
    // emitting debug info in the final output by not generating llvm.dbg.cu.
    if (EmitDebugInfo) {
        NamedMDNode *NMD = M.getOrInsertNamedMetadata("llvm.dbg.cu");
        NMD->addOperand(CUNode);
    }

    trackIfUnresolved(CUNode);
    return CUNode;
}
Esempio n. 17
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DICompileUnit *DIBuilder::createCompileUnit(
    unsigned Lang, DIFile *File, StringRef Producer, bool isOptimized,
    StringRef Flags, unsigned RunTimeVer, StringRef SplitName,
    DICompileUnit::DebugEmissionKind Kind, uint64_t DWOId,
    bool SplitDebugInlining, bool DebugInfoForProfiling, bool GnuPubnames) {

  assert(((Lang <= dwarf::DW_LANG_Fortran08 && Lang >= dwarf::DW_LANG_C89) ||
          (Lang <= dwarf::DW_LANG_hi_user && Lang >= dwarf::DW_LANG_lo_user)) &&
         "Invalid Language tag");

  assert(!CUNode && "Can only make one compile unit per DIBuilder instance");
  CUNode = DICompileUnit::getDistinct(
      VMContext, Lang, File, Producer, isOptimized, Flags, RunTimeVer,
      SplitName, Kind, nullptr, nullptr, nullptr, nullptr, nullptr, DWOId,
      SplitDebugInlining, DebugInfoForProfiling, GnuPubnames);

  // Create a named metadata so that it is easier to find cu in a module.
  NamedMDNode *NMD = M.getOrInsertNamedMetadata("llvm.dbg.cu");
  NMD->addOperand(CUNode);
  trackIfUnresolved(CUNode);
  return CUNode;
}
Esempio n. 18
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/// Remove any debug info for global variables/functions in the given module for
/// which said global variable/function no longer exists (i.e. is null).
///
/// Debugging information is encoded in llvm IR using metadata. This is designed
/// such a way that debug info for symbols preserved even if symbols are
/// optimized away by the optimizer. This special pass removes debug info for
/// such symbols.
bool StripDeadDebugInfo::runOnModule(Module &M) {
  if (skipModule(M))
    return false;

  bool Changed = false;

  LLVMContext &C = M.getContext();

  // Find all debug info in F. This is actually overkill in terms of what we
  // want to do, but we want to try and be as resilient as possible in the face
  // of potential debug info changes by using the formal interfaces given to us
  // as much as possible.
  DebugInfoFinder F;
  F.processModule(M);

  // For each compile unit, find the live set of global variables/functions and
  // replace the current list of potentially dead global variables/functions
  // with the live list.
  SmallVector<Metadata *, 64> LiveGlobalVariables;
  DenseSet<DIGlobalVariableExpression *> VisitedSet;

  std::set<DIGlobalVariableExpression *> LiveGVs;
  for (GlobalVariable &GV : M.globals()) {
    SmallVector<DIGlobalVariableExpression *, 1> GVEs;
    GV.getDebugInfo(GVEs);
    for (auto *GVE : GVEs)
      LiveGVs.insert(GVE);
  }

  std::set<DICompileUnit *> LiveCUs;
  // Any CU referenced from a subprogram is live.
  for (DISubprogram *SP : F.subprograms()) {
    if (SP->getUnit())
      LiveCUs.insert(SP->getUnit());
  }

  bool HasDeadCUs = false;
  for (DICompileUnit *DIC : F.compile_units()) {
    // Create our live global variable list.
    bool GlobalVariableChange = false;
    for (auto *DIG : DIC->getGlobalVariables()) {
      if (DIG->getExpression() && DIG->getExpression()->isConstant())
        LiveGVs.insert(DIG);

      // Make sure we only visit each global variable only once.
      if (!VisitedSet.insert(DIG).second)
        continue;

      // If a global variable references DIG, the global variable is live.
      if (LiveGVs.count(DIG))
        LiveGlobalVariables.push_back(DIG);
      else
        GlobalVariableChange = true;
    }

    if (!LiveGlobalVariables.empty())
      LiveCUs.insert(DIC);
    else if (!LiveCUs.count(DIC))
      HasDeadCUs = true;

    // If we found dead global variables, replace the current global
    // variable list with our new live global variable list.
    if (GlobalVariableChange) {
      DIC->replaceGlobalVariables(MDTuple::get(C, LiveGlobalVariables));
      Changed = true;
    }

    // Reset lists for the next iteration.
    LiveGlobalVariables.clear();
  }

  if (HasDeadCUs) {
    // Delete the old node and replace it with a new one
    NamedMDNode *NMD = M.getOrInsertNamedMetadata("llvm.dbg.cu");
    NMD->clearOperands();
    if (!LiveCUs.empty()) {
      for (DICompileUnit *CU : LiveCUs)
        NMD->addOperand(CU);
    }
    Changed = true;
  }

  return Changed;
}
Esempio n. 19
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std::unique_ptr<Module>
llvm::CloneSubModule(const Module &M,
                     HandleGlobalVariableFtor HandleGlobalVariable,
                     HandleFunctionFtor HandleFunction, bool KeepInlineAsm) {

  ValueToValueMapTy VMap;

  // First off, we need to create the new module.
  std::unique_ptr<Module> New =
      llvm::make_unique<Module>(M.getModuleIdentifier(), M.getContext());

  New->setDataLayout(M.getDataLayout());
  New->setTargetTriple(M.getTargetTriple());
  if (KeepInlineAsm)
    New->setModuleInlineAsm(M.getModuleInlineAsm());

  // Copy global variables (but not initializers, yet).
  for (Module::const_global_iterator I = M.global_begin(), E = M.global_end();
       I != E; ++I) {
    GlobalVariable *GV = new GlobalVariable(
        *New, I->getType()->getElementType(), I->isConstant(), I->getLinkage(),
        (Constant *)nullptr, I->getName(), (GlobalVariable *)nullptr,
        I->getThreadLocalMode(), I->getType()->getAddressSpace());
    GV->copyAttributesFrom(I);
    VMap[I] = GV;
  }

  // Loop over the functions in the module, making external functions as before
  for (Module::const_iterator I = M.begin(), E = M.end(); I != E; ++I) {
    Function *NF =
        Function::Create(cast<FunctionType>(I->getType()->getElementType()),
                         I->getLinkage(), I->getName(), &*New);
    NF->copyAttributesFrom(I);
    VMap[I] = NF;
  }

  // Loop over the aliases in the module
  for (Module::const_alias_iterator I = M.alias_begin(), E = M.alias_end();
       I != E; ++I) {
    auto *PTy = cast<PointerType>(I->getType());
    auto *GA =
        GlobalAlias::create(PTy->getElementType(), PTy->getAddressSpace(),
                            I->getLinkage(), I->getName(), &*New);
    GA->copyAttributesFrom(I);
    VMap[I] = GA;
  }

  // Now that all of the things that global variable initializer can refer to
  // have been created, loop through and copy the global variable referrers
  // over...  We also set the attributes on the global now.
  for (Module::const_global_iterator I = M.global_begin(), E = M.global_end();
       I != E; ++I) {
    GlobalVariable &GV = *cast<GlobalVariable>(VMap[I]);
    HandleGlobalVariable(GV, *I, VMap);
  }

  // Similarly, copy over function bodies now...
  //
  for (Module::const_iterator I = M.begin(), E = M.end(); I != E; ++I) {
    Function &F = *cast<Function>(VMap[I]);
    HandleFunction(F, *I, VMap);
  }

  // And aliases
  for (Module::const_alias_iterator I = M.alias_begin(), E = M.alias_end();
       I != E; ++I) {
    GlobalAlias *GA = cast<GlobalAlias>(VMap[I]);
    if (const Constant *C = I->getAliasee())
      GA->setAliasee(MapValue(C, VMap));
  }

  // And named metadata....
  for (Module::const_named_metadata_iterator I = M.named_metadata_begin(),
                                             E = M.named_metadata_end();
       I != E; ++I) {
    const NamedMDNode &NMD = *I;
    NamedMDNode *NewNMD = New->getOrInsertNamedMetadata(NMD.getName());
    for (unsigned i = 0, e = NMD.getNumOperands(); i != e; ++i)
      NewNMD->addOperand(MapMetadata(NMD.getOperand(i), VMap));
  }

  return New;
}
Esempio n. 20
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Module *llvm::CloneModule(const Module *M, ValueToValueMapTy &VMap) {
  // First off, we need to create the new module.
  Module *New = new Module(M->getModuleIdentifier(), M->getContext());
  New->setDataLayout(M->getDataLayout());
  New->setTargetTriple(M->getTargetTriple());
  New->setModuleInlineAsm(M->getModuleInlineAsm());
   
  // Loop over all of the global variables, making corresponding globals in the
  // new module.  Here we add them to the VMap and to the new Module.  We
  // don't worry about attributes or initializers, they will come later.
  //
  for (Module::const_global_iterator I = M->global_begin(), E = M->global_end();
       I != E; ++I) {
    GlobalVariable *GV = new GlobalVariable(*New, 
                                            I->getType()->getElementType(),
                                            I->isConstant(), I->getLinkage(),
                                            (Constant*) nullptr, I->getName(),
                                            (GlobalVariable*) nullptr,
                                            I->getThreadLocalMode(),
                                            I->getType()->getAddressSpace());
    GV->copyAttributesFrom(I);
    VMap[I] = GV;
  }

  // Loop over the functions in the module, making external functions as before
  for (Module::const_iterator I = M->begin(), E = M->end(); I != E; ++I) {
    Function *NF =
      Function::Create(cast<FunctionType>(I->getType()->getElementType()),
                       I->getLinkage(), I->getName(), New);
    NF->copyAttributesFrom(I);
    VMap[I] = NF;
  }

  // Loop over the aliases in the module
  for (Module::const_alias_iterator I = M->alias_begin(), E = M->alias_end();
       I != E; ++I) {
    auto *PTy = cast<PointerType>(I->getType());
    auto *GA =
        GlobalAlias::create(PTy->getElementType(), PTy->getAddressSpace(),
                            I->getLinkage(), I->getName(), New);
    GA->copyAttributesFrom(I);
    VMap[I] = GA;
  }
  
  // Now that all of the things that global variable initializer can refer to
  // have been created, loop through and copy the global variable referrers
  // over...  We also set the attributes on the global now.
  //
  for (Module::const_global_iterator I = M->global_begin(), E = M->global_end();
       I != E; ++I) {
    GlobalVariable *GV = cast<GlobalVariable>(VMap[I]);
    if (I->hasInitializer())
      GV->setInitializer(MapValue(I->getInitializer(), VMap));
  }

  // Similarly, copy over function bodies now...
  //
  for (Module::const_iterator I = M->begin(), E = M->end(); I != E; ++I) {
    Function *F = cast<Function>(VMap[I]);
    if (!I->isDeclaration()) {
      Function::arg_iterator DestI = F->arg_begin();
      for (Function::const_arg_iterator J = I->arg_begin(); J != I->arg_end();
           ++J) {
        DestI->setName(J->getName());
        VMap[J] = DestI++;
      }

      SmallVector<ReturnInst*, 8> Returns;  // Ignore returns cloned.
      CloneFunctionInto(F, I, VMap, /*ModuleLevelChanges=*/true, Returns);
    }
  }

  // And aliases
  for (Module::const_alias_iterator I = M->alias_begin(), E = M->alias_end();
       I != E; ++I) {
    GlobalAlias *GA = cast<GlobalAlias>(VMap[I]);
    if (const Constant *C = I->getAliasee())
      GA->setAliasee(cast<GlobalObject>(MapValue(C, VMap)));
  }

  // And named metadata....
  for (Module::const_named_metadata_iterator I = M->named_metadata_begin(),
         E = M->named_metadata_end(); I != E; ++I) {
    const NamedMDNode &NMD = *I;
    NamedMDNode *NewNMD = New->getOrInsertNamedMetadata(NMD.getName());
    for (unsigned i = 0, e = NMD.getNumOperands(); i != e; ++i)
      NewNMD->addOperand(MapValue(NMD.getOperand(i), VMap));
  }

  return New;
}
Esempio n. 21
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std::unique_ptr<Module> llvm::CloneModule(
    const Module *M, ValueToValueMapTy &VMap,
    std::function<bool(const GlobalValue *)> ShouldCloneDefinition) {
  // First off, we need to create the new module.
  std::unique_ptr<Module> New =
      llvm::make_unique<Module>(M->getModuleIdentifier(), M->getContext());
  New->setDataLayout(M->getDataLayout());
  New->setTargetTriple(M->getTargetTriple());
  New->setModuleInlineAsm(M->getModuleInlineAsm());
   
  // Loop over all of the global variables, making corresponding globals in the
  // new module.  Here we add them to the VMap and to the new Module.  We
  // don't worry about attributes or initializers, they will come later.
  //
  for (Module::const_global_iterator I = M->global_begin(), E = M->global_end();
       I != E; ++I) {
    GlobalVariable *GV = new GlobalVariable(*New, 
                                            I->getValueType(),
                                            I->isConstant(), I->getLinkage(),
                                            (Constant*) nullptr, I->getName(),
                                            (GlobalVariable*) nullptr,
                                            I->getThreadLocalMode(),
                                            I->getType()->getAddressSpace());
    GV->copyAttributesFrom(&*I);
    VMap[&*I] = GV;
  }

  // Loop over the functions in the module, making external functions as before
  for (Module::const_iterator I = M->begin(), E = M->end(); I != E; ++I) {
    Function *NF =
        Function::Create(cast<FunctionType>(I->getValueType()),
                         I->getLinkage(), I->getName(), New.get());
    NF->copyAttributesFrom(&*I);
    VMap[&*I] = NF;
  }

  // Loop over the aliases in the module
  for (Module::const_alias_iterator I = M->alias_begin(), E = M->alias_end();
       I != E; ++I) {
    if (!ShouldCloneDefinition(&*I)) {
      // An alias cannot act as an external reference, so we need to create
      // either a function or a global variable depending on the value type.
      // FIXME: Once pointee types are gone we can probably pick one or the
      // other.
      GlobalValue *GV;
      if (I->getValueType()->isFunctionTy())
        GV = Function::Create(cast<FunctionType>(I->getValueType()),
                              GlobalValue::ExternalLinkage, I->getName(),
                              New.get());
      else
        GV = new GlobalVariable(
            *New, I->getValueType(), false, GlobalValue::ExternalLinkage,
            (Constant *)nullptr, I->getName(), (GlobalVariable *)nullptr,
            I->getThreadLocalMode(), I->getType()->getAddressSpace());
      VMap[&*I] = GV;
      // We do not copy attributes (mainly because copying between different
      // kinds of globals is forbidden), but this is generally not required for
      // correctness.
      continue;
    }
    auto *GA = GlobalAlias::create(I->getValueType(),
                                   I->getType()->getPointerAddressSpace(),
                                   I->getLinkage(), I->getName(), New.get());
    GA->copyAttributesFrom(&*I);
    VMap[&*I] = GA;
  }
  
  // Now that all of the things that global variable initializer can refer to
  // have been created, loop through and copy the global variable referrers
  // over...  We also set the attributes on the global now.
  //
  for (Module::const_global_iterator I = M->global_begin(), E = M->global_end();
       I != E; ++I) {
    GlobalVariable *GV = cast<GlobalVariable>(VMap[&*I]);
    if (!ShouldCloneDefinition(&*I)) {
      // Skip after setting the correct linkage for an external reference.
      GV->setLinkage(GlobalValue::ExternalLinkage);
      continue;
    }
    if (I->hasInitializer())
      GV->setInitializer(MapValue(I->getInitializer(), VMap));
  }

  // Similarly, copy over function bodies now...
  //
  for (Module::const_iterator I = M->begin(), E = M->end(); I != E; ++I) {
    Function *F = cast<Function>(VMap[&*I]);
    if (!ShouldCloneDefinition(&*I)) {
      // Skip after setting the correct linkage for an external reference.
      F->setLinkage(GlobalValue::ExternalLinkage);
      // Personality function is not valid on a declaration.
      F->setPersonalityFn(nullptr);
      continue;
    }
    if (!I->isDeclaration()) {
      Function::arg_iterator DestI = F->arg_begin();
      for (Function::const_arg_iterator J = I->arg_begin(); J != I->arg_end();
           ++J) {
        DestI->setName(J->getName());
        VMap[&*J] = &*DestI++;
      }

      SmallVector<ReturnInst*, 8> Returns;  // Ignore returns cloned.
      CloneFunctionInto(F, &*I, VMap, /*ModuleLevelChanges=*/true, Returns);
    }

    if (I->hasPersonalityFn())
      F->setPersonalityFn(MapValue(I->getPersonalityFn(), VMap));
  }

  // And aliases
  for (Module::const_alias_iterator I = M->alias_begin(), E = M->alias_end();
       I != E; ++I) {
    // We already dealt with undefined aliases above.
    if (!ShouldCloneDefinition(&*I))
      continue;
    GlobalAlias *GA = cast<GlobalAlias>(VMap[&*I]);
    if (const Constant *C = I->getAliasee())
      GA->setAliasee(MapValue(C, VMap));
  }

  // And named metadata....
  for (Module::const_named_metadata_iterator I = M->named_metadata_begin(),
         E = M->named_metadata_end(); I != E; ++I) {
    const NamedMDNode &NMD = *I;
    NamedMDNode *NewNMD = New->getOrInsertNamedMetadata(NMD.getName());
    for (unsigned i = 0, e = NMD.getNumOperands(); i != e; ++i)
      NewNMD->addOperand(MapMetadata(NMD.getOperand(i), VMap));
  }

  return New;
}
Esempio n. 22
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/// linkModuleFlagsMetadata - Merge the linker flags in Src into the Dest
/// module.
bool ModuleLinker::linkModuleFlagsMetadata() {
  const NamedMDNode *SrcModFlags = SrcM->getModuleFlagsMetadata();
  if (!SrcModFlags) return false;

  NamedMDNode *DstModFlags = DstM->getOrInsertModuleFlagsMetadata();

  // If the destination module doesn't have module flags yet, then just copy
  // over the source module's flags.
  if (DstModFlags->getNumOperands() == 0) {
    for (unsigned I = 0, E = SrcModFlags->getNumOperands(); I != E; ++I)
      DstModFlags->addOperand(SrcModFlags->getOperand(I));

    return false;
  }

  bool HasErr = false;

  // Otherwise, we have to merge them based on their behaviors. First,
  // categorize all of the nodes in the modules' module flags. If an error or
  // warning occurs, then emit the appropriate message(s).
  DenseMap<MDString*, MDNode*> ErrorNode;
  DenseMap<MDString*, MDNode*> WarningNode;
  DenseMap<MDString*, MDNode*> OverrideNode;
  DenseMap<MDString*, SmallSetVector<MDNode*, 8> > RequireNodes;
  SmallSetVector<MDString*, 16> SeenIDs;

  HasErr |= categorizeModuleFlagNodes(SrcModFlags, ErrorNode, WarningNode,
                                      OverrideNode, RequireNodes, SeenIDs);
  HasErr |= categorizeModuleFlagNodes(DstModFlags, ErrorNode, WarningNode,
                                      OverrideNode, RequireNodes, SeenIDs);

  // Check that there isn't both an error and warning node for a flag.
  for (SmallSetVector<MDString*, 16>::iterator
         I = SeenIDs.begin(), E = SeenIDs.end(); I != E; ++I) {
    MDString *ID = *I;
    if (ErrorNode[ID] && WarningNode[ID])
      HasErr = emitError("linking module flags '" + ID->getString() +
                         "': IDs have conflicting behaviors");
  }

  // Early exit if we had an error.
  if (HasErr) return true;

  // Get the destination's module flags ready for new operands.
  DstModFlags->dropAllReferences();

  // Add all of the module flags to the destination module.
  DenseMap<MDString*, SmallVector<MDNode*, 4> > AddedNodes;
  for (SmallSetVector<MDString*, 16>::iterator
         I = SeenIDs.begin(), E = SeenIDs.end(); I != E; ++I) {
    MDString *ID = *I;
    if (OverrideNode[ID]) {
      DstModFlags->addOperand(OverrideNode[ID]);
      AddedNodes[ID].push_back(OverrideNode[ID]);
    } else if (ErrorNode[ID]) {
      DstModFlags->addOperand(ErrorNode[ID]);
      AddedNodes[ID].push_back(ErrorNode[ID]);
    } else if (WarningNode[ID]) {
      DstModFlags->addOperand(WarningNode[ID]);
      AddedNodes[ID].push_back(WarningNode[ID]);
    }

    for (SmallSetVector<MDNode*, 8>::iterator
           II = RequireNodes[ID].begin(), IE = RequireNodes[ID].end();
         II != IE; ++II)
      DstModFlags->addOperand(*II);
  }

  // Now check that all of the requirements have been satisfied.
  for (SmallSetVector<MDString*, 16>::iterator
         I = SeenIDs.begin(), E = SeenIDs.end(); I != E; ++I) {
    MDString *ID = *I;
    SmallSetVector<MDNode*, 8> &Set = RequireNodes[ID];

    for (SmallSetVector<MDNode*, 8>::iterator
           II = Set.begin(), IE = Set.end(); II != IE; ++II) {
      MDNode *Node = *II;
      assert(isa<MDNode>(Node->getOperand(2)) &&
             "Module flag's third operand must be an MDNode!");
      MDNode *Val = cast<MDNode>(Node->getOperand(2));

      MDString *ReqID = cast<MDString>(Val->getOperand(0));
      Value *ReqVal = Val->getOperand(1);

      bool HasValue = false;
      for (SmallVectorImpl<MDNode*>::iterator
             RI = AddedNodes[ReqID].begin(), RE = AddedNodes[ReqID].end();
           RI != RE; ++RI) {
        MDNode *ReqNode = *RI;
        if (ReqNode->getOperand(2) == ReqVal) {
          HasValue = true;
          break;
        }
      }

      if (!HasValue)
        HasErr = emitError("linking module flags '" + ReqID->getString() +
                           "': does not have the required value");
    }
  }

  return HasErr;
}
Esempio n. 23
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// destructively move the contents of src into dest
// this assumes that the targets of the two modules are the same
// including the DataLayout and ModuleFlags (for example)
// and that there is no module-level assembly
static void jl_merge_module(Module *dest, std::unique_ptr<Module> src)
{
    assert(dest != src.get());
    for (Module::global_iterator I = src->global_begin(), E = src->global_end(); I != E;) {
        GlobalVariable *sG = &*I;
        GlobalValue *dG = dest->getNamedValue(sG->getName());
        ++I;
        // Replace a declaration with the definition:
        if (dG) {
            if (sG->isDeclaration()) {
                sG->replaceAllUsesWith(dG);
                sG->eraseFromParent();
                continue;
            }
            else {
                dG->replaceAllUsesWith(sG);
                dG->eraseFromParent();
            }
        }
        // Reparent the global variable:
        sG->removeFromParent();
        dest->getGlobalList().push_back(sG);
        // Comdat is owned by the Module, recreate it in the new parent:
        addComdat(sG);
    }

    for (Module::iterator I = src->begin(), E = src->end(); I != E;) {
        Function *sG = &*I;
        GlobalValue *dG = dest->getNamedValue(sG->getName());
        ++I;
        // Replace a declaration with the definition:
        if (dG) {
            if (sG->isDeclaration()) {
                sG->replaceAllUsesWith(dG);
                sG->eraseFromParent();
                continue;
            }
            else {
                dG->replaceAllUsesWith(sG);
                dG->eraseFromParent();
            }
        }
        // Reparent the global variable:
        sG->removeFromParent();
        dest->getFunctionList().push_back(sG);
        // Comdat is owned by the Module, recreate it in the new parent:
        addComdat(sG);
    }

    for (Module::alias_iterator I = src->alias_begin(), E = src->alias_end(); I != E;) {
        GlobalAlias *sG = &*I;
        GlobalValue *dG = dest->getNamedValue(sG->getName());
        ++I;
        if (dG) {
            if (!dG->isDeclaration()) { // aliases are always definitions, so this test is reversed from the above two
                sG->replaceAllUsesWith(dG);
                sG->eraseFromParent();
                continue;
            }
            else {
                dG->replaceAllUsesWith(sG);
                dG->eraseFromParent();
            }
        }
        sG->removeFromParent();
        dest->getAliasList().push_back(sG);
    }

    // metadata nodes need to be explicitly merged not just copied
    // so there are special passes here for each known type of metadata
    NamedMDNode *sNMD = src->getNamedMetadata("llvm.dbg.cu");
    if (sNMD) {
        NamedMDNode *dNMD = dest->getOrInsertNamedMetadata("llvm.dbg.cu");
#ifdef LLVM35
        for (NamedMDNode::op_iterator I = sNMD->op_begin(), E = sNMD->op_end(); I != E; ++I) {
            dNMD->addOperand(*I);
        }
#else
        for (unsigned i = 0, l = sNMD->getNumOperands(); i < l; i++) {
            dNMD->addOperand(sNMD->getOperand(i));
        }
#endif
    }
}
Esempio n. 24
0
/// Merge the linker flags in Src into the Dest module.
Error IRLinker::linkModuleFlagsMetadata() {
  // If the source module has no module flags, we are done.
  const NamedMDNode *SrcModFlags = SrcM->getModuleFlagsMetadata();
  if (!SrcModFlags)
    return Error::success();

  // If the destination module doesn't have module flags yet, then just copy
  // over the source module's flags.
  NamedMDNode *DstModFlags = DstM.getOrInsertModuleFlagsMetadata();
  if (DstModFlags->getNumOperands() == 0) {
    for (unsigned I = 0, E = SrcModFlags->getNumOperands(); I != E; ++I)
      DstModFlags->addOperand(SrcModFlags->getOperand(I));

    return Error::success();
  }

  // First build a map of the existing module flags and requirements.
  DenseMap<MDString *, std::pair<MDNode *, unsigned>> Flags;
  SmallSetVector<MDNode *, 16> Requirements;
  for (unsigned I = 0, E = DstModFlags->getNumOperands(); I != E; ++I) {
    MDNode *Op = DstModFlags->getOperand(I);
    ConstantInt *Behavior = mdconst::extract<ConstantInt>(Op->getOperand(0));
    MDString *ID = cast<MDString>(Op->getOperand(1));

    if (Behavior->getZExtValue() == Module::Require) {
      Requirements.insert(cast<MDNode>(Op->getOperand(2)));
    } else {
      Flags[ID] = std::make_pair(Op, I);
    }
  }

  // Merge in the flags from the source module, and also collect its set of
  // requirements.
  for (unsigned I = 0, E = SrcModFlags->getNumOperands(); I != E; ++I) {
    MDNode *SrcOp = SrcModFlags->getOperand(I);
    ConstantInt *SrcBehavior =
        mdconst::extract<ConstantInt>(SrcOp->getOperand(0));
    MDString *ID = cast<MDString>(SrcOp->getOperand(1));
    MDNode *DstOp;
    unsigned DstIndex;
    std::tie(DstOp, DstIndex) = Flags.lookup(ID);
    unsigned SrcBehaviorValue = SrcBehavior->getZExtValue();

    // If this is a requirement, add it and continue.
    if (SrcBehaviorValue == Module::Require) {
      // If the destination module does not already have this requirement, add
      // it.
      if (Requirements.insert(cast<MDNode>(SrcOp->getOperand(2)))) {
        DstModFlags->addOperand(SrcOp);
      }
      continue;
    }

    // If there is no existing flag with this ID, just add it.
    if (!DstOp) {
      Flags[ID] = std::make_pair(SrcOp, DstModFlags->getNumOperands());
      DstModFlags->addOperand(SrcOp);
      continue;
    }

    // Otherwise, perform a merge.
    ConstantInt *DstBehavior =
        mdconst::extract<ConstantInt>(DstOp->getOperand(0));
    unsigned DstBehaviorValue = DstBehavior->getZExtValue();

    // If either flag has override behavior, handle it first.
    if (DstBehaviorValue == Module::Override) {
      // Diagnose inconsistent flags which both have override behavior.
      if (SrcBehaviorValue == Module::Override &&
          SrcOp->getOperand(2) != DstOp->getOperand(2))
        return stringErr("linking module flags '" + ID->getString() +
                         "': IDs have conflicting override values");
      continue;
    } else if (SrcBehaviorValue == Module::Override) {
      // Update the destination flag to that of the source.
      DstModFlags->setOperand(DstIndex, SrcOp);
      Flags[ID].first = SrcOp;
      continue;
    }

    // Diagnose inconsistent merge behavior types.
    if (SrcBehaviorValue != DstBehaviorValue)
      return stringErr("linking module flags '" + ID->getString() +
                       "': IDs have conflicting behaviors");

    auto replaceDstValue = [&](MDNode *New) {
      Metadata *FlagOps[] = {DstOp->getOperand(0), ID, New};
      MDNode *Flag = MDNode::get(DstM.getContext(), FlagOps);
      DstModFlags->setOperand(DstIndex, Flag);
      Flags[ID].first = Flag;
    };

    // Perform the merge for standard behavior types.
    switch (SrcBehaviorValue) {
    case Module::Require:
    case Module::Override:
      llvm_unreachable("not possible");
    case Module::Error: {
      // Emit an error if the values differ.
      if (SrcOp->getOperand(2) != DstOp->getOperand(2))
        return stringErr("linking module flags '" + ID->getString() +
                         "': IDs have conflicting values");
      continue;
    }
    case Module::Warning: {
      // Emit a warning if the values differ.
      if (SrcOp->getOperand(2) != DstOp->getOperand(2)) {
        emitWarning("linking module flags '" + ID->getString() +
                    "': IDs have conflicting values");
      }
      continue;
    }
    case Module::Append: {
      MDNode *DstValue = cast<MDNode>(DstOp->getOperand(2));
      MDNode *SrcValue = cast<MDNode>(SrcOp->getOperand(2));
      SmallVector<Metadata *, 8> MDs;
      MDs.reserve(DstValue->getNumOperands() + SrcValue->getNumOperands());
      MDs.append(DstValue->op_begin(), DstValue->op_end());
      MDs.append(SrcValue->op_begin(), SrcValue->op_end());

      replaceDstValue(MDNode::get(DstM.getContext(), MDs));
      break;
    }
    case Module::AppendUnique: {
      SmallSetVector<Metadata *, 16> Elts;
      MDNode *DstValue = cast<MDNode>(DstOp->getOperand(2));
      MDNode *SrcValue = cast<MDNode>(SrcOp->getOperand(2));
      Elts.insert(DstValue->op_begin(), DstValue->op_end());
      Elts.insert(SrcValue->op_begin(), SrcValue->op_end());

      replaceDstValue(MDNode::get(DstM.getContext(),
                                  makeArrayRef(Elts.begin(), Elts.end())));
      break;
    }
    }
  }

  // Check all of the requirements.
  for (unsigned I = 0, E = Requirements.size(); I != E; ++I) {
    MDNode *Requirement = Requirements[I];
    MDString *Flag = cast<MDString>(Requirement->getOperand(0));
    Metadata *ReqValue = Requirement->getOperand(1);

    MDNode *Op = Flags[Flag].first;
    if (!Op || Op->getOperand(2) != ReqValue)
      return stringErr("linking module flags '" + Flag->getString() +
                       "': does not have the required value");
  }
  return Error::success();
}