C++ GlobalValue::hasLocalLinkage方法代码示例

void FunctionImportGlobalProcessing::processGlobalForThinLTO(GlobalValue &GV) {
  bool DoPromote = false;
  if (GV.hasLocalLinkage() &&
      ((DoPromote = shouldPromoteLocalToGlobal(&GV)) || isPerformingImport())) {
    // Once we change the name or linkage it is difficult to determine
    // again whether we should promote since shouldPromoteLocalToGlobal needs
    // to locate the summary (based on GUID from name and linkage). Therefore,
    // use DoPromote result saved above.
    GV.setName(getName(&GV, DoPromote));
    GV.setLinkage(getLinkage(&GV, DoPromote));
    if (!GV.hasLocalLinkage())
      GV.setVisibility(GlobalValue::HiddenVisibility);
  } else
    GV.setLinkage(getLinkage(&GV, /* DoPromote */ false));

  // Remove functions imported as available externally defs from comdats,
  // as this is a declaration for the linker, and will be dropped eventually.
  // It is illegal for comdats to contain declarations.
  auto *GO = dyn_cast_or_null<GlobalObject>(&GV);
  if (GO && GO->isDeclarationForLinker() && GO->hasComdat()) {
    // The IRMover should not have placed any imported declarations in
    // a comdat, so the only declaration that should be in a comdat
    // at this point would be a definition imported as available_externally.
    assert(GO->hasAvailableExternallyLinkage() &&
           "Expected comdat on definition (possibly available external)");
    GO->setComdat(nullptr);
  }
}

void ThinLTOGlobalProcessing::processGlobalForThinLTO(GlobalValue &GV) {
  if (GV.hasLocalLinkage() &&
      (doPromoteLocalToGlobal(&GV) || isPerformingImport())) {
    GV.setName(getName(&GV));
    GV.setLinkage(getLinkage(&GV));
    if (!GV.hasLocalLinkage())
      GV.setVisibility(GlobalValue::HiddenVisibility);
    if (isModuleExporting())
      NewExportedValues.insert(&GV);
    return;
  }
  GV.setLinkage(getLinkage(&GV));
}

static bool shouldInternalize(const GlobalValue &GV,
                              const std::set<std::string> &ExternalNames,
                              bool OnlyHidden) {
  if (OnlyHidden && !GV.hasHiddenVisibility())
    return false;

  // Function must be defined here
  if (GV.isDeclaration())
    return false;

  // Available externally is really just a "declaration with a body".
  if (GV.hasAvailableExternallyLinkage())
    return false;

  // Assume that dllexported symbols are referenced elsewhere
  if (GV.hasDLLExportStorageClass())
    return false;

  // Already has internal linkage
  if (GV.hasLocalLinkage())
    return false;

  // Marked to keep external?
  if (ExternalNames.count(GV.getName()))
    return false;

  return true;
}

static void DumpSymbolNameForGlobalValue(GlobalValue &GV) {
  // Private linkage and available_externally linkage don't exist in symtab.
  if (GV.hasPrivateLinkage() || GV.hasLinkerPrivateLinkage() ||
      GV.hasLinkerPrivateWeakLinkage() || GV.hasAvailableExternallyLinkage())
    return;
  
  const std::string SymbolAddrStr = "        "; // Not used yet...
  char TypeChar = TypeCharForSymbol(GV);
  if ((TypeChar != 'U') && UndefinedOnly)
    return;
  if ((TypeChar == 'U') && DefinedOnly)
    return;
  if (GV.hasLocalLinkage () && ExternalOnly)
    return;
  if (OutputFormat == posix) {
    outs() << GV.getName () << " " << TypeCharForSymbol(GV) << " "
           << SymbolAddrStr << "\n";
  } else if (OutputFormat == bsd) {
    outs() << SymbolAddrStr << " " << TypeCharForSymbol(GV) << " "
           << GV.getName () << "\n";
  } else if (OutputFormat == sysv) {
    std::string PaddedName (GV.getName ());
    while (PaddedName.length () < 20)
      PaddedName += " ";
    outs() << PaddedName << "|" << SymbolAddrStr << "|   "
           << TypeCharForSymbol(GV)
           << "  |                  |      |     |\n";
  }
}

// getOrInsertFunction - Look up the specified function in the module symbol
// table.  If it does not exist, add a prototype for the function and return
// it.  This is nice because it allows most passes to get away with not handling
// the symbol table directly for this common task.
//
Constant *Module::getOrInsertFunction(StringRef Name,
                                      FunctionType *Ty,
                                      AttrListPtr AttributeList) {
  // See if we have a definition for the specified function already.
  GlobalValue *F = getNamedValue(Name);
  if (F == 0) {
    // Nope, add it
    Function *New = Function::Create(Ty, GlobalVariable::ExternalLinkage, Name);
    if (!New->isIntrinsic())       // Intrinsics get attrs set on construction
      New->setAttributes(AttributeList);
    FunctionList.push_back(New);
    return New;                    // Return the new prototype.
  }

  // Okay, the function exists.  Does it have externally visible linkage?
  if (F->hasLocalLinkage()) {
    // Clear the function's name.
    F->setName("");
    // Retry, now there won't be a conflict.
    Constant *NewF = getOrInsertFunction(Name, Ty);
    F->setName(Name);
    return NewF;
  }

  // If the function exists but has the wrong type, return a bitcast to the
  // right type.
  if (F->getType() != PointerType::getUnqual(Ty))
    return ConstantExpr::getBitCast(F, PointerType::getUnqual(Ty));

  // Otherwise, we just found the existing function or a prototype.
  return F;
}

/// Make sure GV is visible from both modules. Delete is true if it is
/// being deleted from this module.
/// This also makes sure GV cannot be dropped so that references from
/// the split module remain valid.
static void makeVisible(GlobalValue &GV, bool Delete) {
  bool Local = GV.hasLocalLinkage();
  if (Local)
    GV.setVisibility(GlobalValue::HiddenVisibility);

  if (Local || Delete) {
    GV.setLinkage(GlobalValue::ExternalLinkage);
    return;
  }

  if (!GV.hasLinkOnceLinkage()) {
    assert(!GV.isDiscardableIfUnused());
    return;
  }

  // Map linkonce* to weak* so that llvm doesn't drop this GV.
  switch(GV.getLinkage()) {
  default:
    llvm_unreachable("Unexpected linkage");
  case GlobalValue::LinkOnceAnyLinkage:
    GV.setLinkage(GlobalValue::WeakAnyLinkage);
    return;
  case GlobalValue::LinkOnceODRLinkage:
    GV.setLinkage(GlobalValue::WeakODRLinkage);
    return;
  }
}

/// Make sure GV is visible from both modules. Delete is true if it is
/// being deleted from this module.
/// This also makes sure GV cannot be dropped so that references from
/// the split module remain valid.
static void makeVisible(GlobalValue &GV, bool Delete, bool IsDeletePass) {
  bool Local = GV.hasLocalLinkage();
  if (Local || Delete) {
    // This changes members from private -> hidden -> causes linker errors when using llvm-link
    if (!IsDeletePass)
      GV.setLinkage(GlobalValue::ExternalLinkage);
    if (Local)
      GV.setVisibility(GlobalValue::HiddenVisibility);
    return;
  }

  if (!GV.hasLinkOnceLinkage()) {
    assert(!GV.isDiscardableIfUnused());
    return;
  }

  // Map linkonce* to weak* so that llvm doesn't drop this GV.
  switch(GV.getLinkage()) {
  default:
    llvm_unreachable("Unexpected linkage");
  case GlobalValue::LinkOnceAnyLinkage:
    GV.setLinkage(GlobalValue::WeakAnyLinkage);
    return;
  case GlobalValue::LinkOnceODRLinkage:
    GV.setLinkage(GlobalValue::WeakODRLinkage);
    return;
  }
}

static bool shouldInternalize(const GlobalValue &GV,
                              const std::set<std::string> &ExternalNames,
                              const std::set<std::string> &DSONames) {
  // Function must be defined here
  if (GV.isDeclaration())
    return false;

  // Available externally is really just a "declaration with a body".
  if (GV.hasAvailableExternallyLinkage())
    return false;

  // Already has internal linkage
  if (GV.hasLocalLinkage())
    return false;

  // Marked to keep external?
  if (ExternalNames.count(GV.getName()))
    return false;

  // Not needed for the symbol table?
  if (!DSONames.count(GV.getName()))
    return true;

  // Not a linkonce. Someone can depend on it being on the symbol table.
  if (!GV.hasLinkOnceLinkage())
    return false;

  // The address is not important, we can hide it.
  if (GV.hasUnnamedAddr())
    return true;

  // FIXME: Check if the address is used.
  return false;
}

void FunctionImportGlobalProcessing::processGlobalForThinLTO(GlobalValue &GV) {

  // Check the summaries to see if the symbol gets resolved to a known local
  // definition.
  if (GV.hasName()) {
    ValueInfo VI = ImportIndex.getValueInfo(GV.getGUID());
    if (VI) {
      // Need to check all summaries are local in case of hash collisions.
      bool IsLocal = VI.getSummaryList().size() &&
          llvm::all_of(VI.getSummaryList(),
                       [](const std::unique_ptr<GlobalValueSummary> &Summary) {
                         return Summary->isDSOLocal();
                       });
      if (IsLocal)
        GV.setDSOLocal(true);
    }
  }

  bool DoPromote = false;
  if (GV.hasLocalLinkage() &&
      ((DoPromote = shouldPromoteLocalToGlobal(&GV)) || isPerformingImport())) {
    // Once we change the name or linkage it is difficult to determine
    // again whether we should promote since shouldPromoteLocalToGlobal needs
    // to locate the summary (based on GUID from name and linkage). Therefore,
    // use DoPromote result saved above.
    GV.setName(getName(&GV, DoPromote));
    GV.setLinkage(getLinkage(&GV, DoPromote));
    if (!GV.hasLocalLinkage())
      GV.setVisibility(GlobalValue::HiddenVisibility);
  } else
    GV.setLinkage(getLinkage(&GV, /* DoPromote */ false));

  // Remove functions imported as available externally defs from comdats,
  // as this is a declaration for the linker, and will be dropped eventually.
  // It is illegal for comdats to contain declarations.
  auto *GO = dyn_cast_or_null<GlobalObject>(&GV);
  if (GO && GO->isDeclarationForLinker() && GO->hasComdat()) {
    // The IRMover should not have placed any imported declarations in
    // a comdat, so the only declaration that should be in a comdat
    // at this point would be a definition imported as available_externally.
    assert(GO->hasAvailableExternallyLinkage() &&
           "Expected comdat on definition (possibly available external)");
    GO->setComdat(nullptr);
  }
}

static void raiseVisibilityOnValue(GlobalValue &V, GlobalRenamer &R) {
  if (V.hasLocalLinkage()) {
    if (R.needsRenaming(V))
      V.setName(R.getRename(V));
    V.setLinkage(GlobalValue::ExternalLinkage);
    V.setVisibility(GlobalValue::HiddenVisibility);
  }
  V.setUnnamedAddr(GlobalValue::UnnamedAddr::None);
  assert(!R.needsRenaming(V) && "Invalid global name.");
}

bool FunctionImportGlobalProcessing::isNonRenamableLocal(
    const GlobalValue &GV) const {
  if (!GV.hasLocalLinkage())
    return false;
  // This needs to stay in sync with the logic in buildModuleSummaryIndex.
  if (GV.hasSection())
    return true;
  if (Used.count(const_cast<GlobalValue *>(&GV)))
    return true;
  return false;
}

JITSymbolFlags llvm::JITSymbolFlags::fromGlobalValue(const GlobalValue &GV) {
  JITSymbolFlags Flags = JITSymbolFlags::None;
  if (GV.hasWeakLinkage() || GV.hasLinkOnceLinkage())
    Flags |= JITSymbolFlags::Weak;
  if (GV.hasCommonLinkage())
    Flags |= JITSymbolFlags::Common;
  if (!GV.hasLocalLinkage() && !GV.hasHiddenVisibility())
    Flags |= JITSymbolFlags::Exported;

  if (isa<Function>(GV))
    Flags |= JITSymbolFlags::Callable;
  else if (isa<GlobalAlias>(GV) &&
           isa<Function>(cast<GlobalAlias>(GV).getAliasee()))
    Flags |= JITSymbolFlags::Callable;

  return Flags;
}

static void DumpSymbolNameForGlobalValue(GlobalValue &GV) {
  // Private linkage and available_externally linkage don't exist in symtab.
  if (GV.hasPrivateLinkage() ||
      GV.hasLinkerPrivateLinkage() ||
      GV.hasLinkerPrivateWeakLinkage() ||
      GV.hasAvailableExternallyLinkage())
    return;
  char TypeChar = TypeCharForSymbol(GV);
  if (GV.hasLocalLinkage () && ExternalOnly)
    return;

  NMSymbol s;
  s.Address = object::UnknownAddressOrSize;
  s.Size = object::UnknownAddressOrSize;
  s.TypeChar = TypeChar;
  s.Name     = GV.getName();
  SymbolList.push_back(s);
}

bool IRLinker::shouldLink(GlobalValue *DGV, GlobalValue &SGV) {
  if (ValuesToLink.count(&SGV))
    return true;

  if (SGV.hasLocalLinkage())
    return true;

  if (DGV && !DGV->isDeclaration())
    return false;

  if (SGV.hasAvailableExternallyLinkage())
    return true;

  if (DoneLinkingBodies)
    return false;

  AddLazyFor(SGV, [this](GlobalValue &GV) { maybeAdd(&GV); });
  return ValuesToLink.count(&SGV);
}

static void keepGlobalValue(GlobalValue &GV,
                            std::vector<GlobalAlias *> &KeptAliases) {
  assert(!GV.hasLocalLinkage());

  if (auto *GA = dyn_cast<GlobalAlias>(&GV))
    KeptAliases.push_back(GA);

  switch (GV.getLinkage()) {
  default:
    break;
  case GlobalValue::LinkOnceAnyLinkage:
    GV.setLinkage(GlobalValue::WeakAnyLinkage);
    break;
  case GlobalValue::LinkOnceODRLinkage:
    GV.setLinkage(GlobalValue::WeakODRLinkage);
    break;
  }

  assert(!GV.isDiscardableIfUnused());
}