C++ MDNode::operands方法代码示例

void TargetLoweringObjectFileCOFF::emitModuleFlags(
    MCStreamer &Streamer, ArrayRef<Module::ModuleFlagEntry> ModuleFlags,
    const TargetMachine &TM) const {
  MDNode *LinkerOptions = nullptr;

  for (const auto &MFE : ModuleFlags) {
    StringRef Key = MFE.Key->getString();
    if (Key == "Linker Options")
      LinkerOptions = cast<MDNode>(MFE.Val);
  }

  if (LinkerOptions) {
    // Emit the linker options to the linker .drectve section.  According to the
    // spec, this section is a space-separated string containing flags for
    // linker.
    MCSection *Sec = getDrectveSection();
    Streamer.SwitchSection(Sec);
    for (const auto &Option : LinkerOptions->operands()) {
      for (const auto &Piece : cast<MDNode>(Option)->operands()) {
        // Lead with a space for consistency with our dllexport implementation.
        std::string Directive(" ");
        Directive.append(cast<MDString>(Piece)->getString());
        Streamer.EmitBytes(Directive);
      }
    }
  }
}

/// \brief Map a distinct MDNode.
///
/// Distinct nodes are not uniqued, so they must always recreated.
static Metadata *mapDistinctNode(const MDNode *Node,
                                 SmallVectorImpl<MDNode *> &Cycles,
                                 ValueToValueMapTy &VM, RemapFlags Flags,
                                 ValueMapTypeRemapper *TypeMapper,
                                 ValueMaterializer *Materializer) {
  assert(Node->isDistinct() && "Expected distinct node");

  MDNode *NewMD = MDNode::replaceWithDistinct(Node->clone());
  remap(Node, NewMD, Cycles, VM, Flags, TypeMapper, Materializer);

  // Track any cycles beneath this node.
  for (Metadata *Op : NewMD->operands())
    if (auto *Node = dyn_cast_or_null<MDNode>(Op))
      if (!Node->isResolved())
        Cycles.push_back(Node);

  return NewMD;
}

bool Loop::isAnnotatedParallel() const {
  MDNode *DesiredLoopIdMetadata = getLoopID();

  if (!DesiredLoopIdMetadata)
      return false;

  // The loop branch contains the parallel loop metadata. In order to ensure
  // that any parallel-loop-unaware optimization pass hasn't added loop-carried
  // dependencies (thus converted the loop back to a sequential loop), check
  // that all the memory instructions in the loop contain parallelism metadata
  // that point to the same unique "loop id metadata" the loop branch does.
  for (BasicBlock *BB : this->blocks()) {
    for (Instruction &I : *BB) {
      if (!I.mayReadOrWriteMemory())
        continue;

      // The memory instruction can refer to the loop identifier metadata
      // directly or indirectly through another list metadata (in case of
      // nested parallel loops). The loop identifier metadata refers to
      // itself so we can check both cases with the same routine.
      MDNode *LoopIdMD =
          I.getMetadata(LLVMContext::MD_mem_parallel_loop_access);

      if (!LoopIdMD)
        return false;

      bool LoopIdMDFound = false;
      for (const MDOperand &MDOp : LoopIdMD->operands()) {
        if (MDOp == DesiredLoopIdMetadata) {
          LoopIdMDFound = true;
          break;
        }
      }

      if (!LoopIdMDFound)
        return false;
    }
  }
  return true;
}

Optional<MDNode *> llvm::makeFollowupLoopID(
    MDNode *OrigLoopID, ArrayRef<StringRef> FollowupOptions,
    const char *InheritOptionsExceptPrefix, bool AlwaysNew) {
  if (!OrigLoopID) {
    if (AlwaysNew)
      return nullptr;
    return None;
  }

  assert(OrigLoopID->getOperand(0) == OrigLoopID);

  bool InheritAllAttrs = !InheritOptionsExceptPrefix;
  bool InheritSomeAttrs =
      InheritOptionsExceptPrefix && InheritOptionsExceptPrefix[0] != '\0';
  SmallVector<Metadata *, 8> MDs;
  MDs.push_back(nullptr);

  bool Changed = false;
  if (InheritAllAttrs || InheritSomeAttrs) {
    for (const MDOperand &Existing : drop_begin(OrigLoopID->operands(), 1)) {
      MDNode *Op = cast<MDNode>(Existing.get());

      auto InheritThisAttribute = [InheritSomeAttrs,
                                   InheritOptionsExceptPrefix](MDNode *Op) {
        if (!InheritSomeAttrs)
          return false;

        // Skip malformatted attribute metadata nodes.
        if (Op->getNumOperands() == 0)
          return true;
        Metadata *NameMD = Op->getOperand(0).get();
        if (!isa<MDString>(NameMD))
          return true;
        StringRef AttrName = cast<MDString>(NameMD)->getString();

        // Do not inherit excluded attributes.
        return !AttrName.startswith(InheritOptionsExceptPrefix);
      };

      if (InheritThisAttribute(Op))
        MDs.push_back(Op);
      else
        Changed = true;
    }
  } else {
    // Modified if we dropped at least one attribute.
    Changed = OrigLoopID->getNumOperands() > 1;
  }

  bool HasAnyFollowup = false;
  for (StringRef OptionName : FollowupOptions) {
    MDNode *FollowupNode = findOptionMDForLoopID(OrigLoopID, OptionName);
    if (!FollowupNode)
      continue;

    HasAnyFollowup = true;
    for (const MDOperand &Option : drop_begin(FollowupNode->operands(), 1)) {
      MDs.push_back(Option.get());
      Changed = true;
    }
  }

  // Attributes of the followup loop not specified explicity, so signal to the
  // transformation pass to add suitable attributes.
  if (!AlwaysNew && !HasAnyFollowup)
    return None;

  // If no attributes were added or remove, the previous loop Id can be reused.
  if (!AlwaysNew && !Changed)
    return OrigLoopID;

  // No attributes is equivalent to having no !llvm.loop metadata at all.
  if (MDs.size() == 1)
    return nullptr;

  // Build the new loop ID.
  MDTuple *FollowupLoopID = MDNode::get(OrigLoopID->getContext(), MDs);
  FollowupLoopID->replaceOperandWith(0, FollowupLoopID);
  return FollowupLoopID;
}

bool Loop::isAnnotatedParallel() const {
  MDNode *DesiredLoopIdMetadata = getLoopID();

  if (!DesiredLoopIdMetadata)
    return false;

  MDNode *ParallelAccesses =
      findOptionMDForLoop(this, "llvm.loop.parallel_accesses");
  SmallPtrSet<MDNode *, 4>
      ParallelAccessGroups; // For scalable 'contains' check.
  if (ParallelAccesses) {
    for (const MDOperand &MD : drop_begin(ParallelAccesses->operands(), 1)) {
      MDNode *AccGroup = cast<MDNode>(MD.get());
      assert(isValidAsAccessGroup(AccGroup) &&
             "List item must be an access group");
      ParallelAccessGroups.insert(AccGroup);
    }
  }

  // The loop branch contains the parallel loop metadata. In order to ensure
  // that any parallel-loop-unaware optimization pass hasn't added loop-carried
  // dependencies (thus converted the loop back to a sequential loop), check
  // that all the memory instructions in the loop belong to an access group that
  // is parallel to this loop.
  for (BasicBlock *BB : this->blocks()) {
    for (Instruction &I : *BB) {
      if (!I.mayReadOrWriteMemory())
        continue;

      if (MDNode *AccessGroup = I.getMetadata(LLVMContext::MD_access_group)) {
        auto ContainsAccessGroup = [&ParallelAccessGroups](MDNode *AG) -> bool {
          if (AG->getNumOperands() == 0) {
            assert(isValidAsAccessGroup(AG) && "Item must be an access group");
            return ParallelAccessGroups.count(AG);
          }

          for (const MDOperand &AccessListItem : AG->operands()) {
            MDNode *AccGroup = cast<MDNode>(AccessListItem.get());
            assert(isValidAsAccessGroup(AccGroup) &&
                   "List item must be an access group");
            if (ParallelAccessGroups.count(AccGroup))
              return true;
          }
          return false;
        };

        if (ContainsAccessGroup(AccessGroup))
          continue;
      }

      // The memory instruction can refer to the loop identifier metadata
      // directly or indirectly through another list metadata (in case of
      // nested parallel loops). The loop identifier metadata refers to
      // itself so we can check both cases with the same routine.
      MDNode *LoopIdMD =
          I.getMetadata(LLVMContext::MD_mem_parallel_loop_access);

      if (!LoopIdMD)
        return false;

      bool LoopIdMDFound = false;
      for (const MDOperand &MDOp : LoopIdMD->operands()) {
        if (MDOp == DesiredLoopIdMetadata) {
          LoopIdMDFound = true;
          break;
        }
      }

      if (!LoopIdMDFound)
        return false;
    }
  }
  return true;
}