//===- OrcRemoteTargetClient.h - Orc Remote-target Client -------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file defines the OrcRemoteTargetClient class and helpers. This class
// can be used to communicate over an RawByteChannel with an
// OrcRemoteTargetServer instance to support remote-JITing.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_EXECUTIONENGINE_ORC_ORCREMOTETARGETCLIENT_H
#define LLVM_EXECUTIONENGINE_ORC_ORCREMOTETARGETCLIENT_H

#include "llvm/ADT/Optional.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ExecutionEngine/JITSymbol.h"
#include "llvm/ExecutionEngine/JITLink/JITLinkMemoryManager.h"
#include "llvm/ExecutionEngine/Orc/IndirectionUtils.h"
#include "llvm/ExecutionEngine/Orc/OrcRemoteTargetRPCAPI.h"
#include "llvm/ExecutionEngine/RuntimeDyld.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/Error.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/Format.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/Memory.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
#include <cassert>
#include <cstdint>
#include <memory>
#include <string>
#include <tuple>
#include <utility>
#include <vector>

#define DEBUG_TYPE "orc-remote"

namespace llvm {
namespace orc {
namespace remote {

/// This class provides utilities (including memory manager, indirect stubs
/// manager, and compile callback manager types) that support remote JITing
/// in ORC.
///
/// Each of the utility classes talks to a JIT server (an instance of the
/// OrcRemoteTargetServer class) via an RPC system (see RPCUtils.h) to carry out
/// its actions.
class OrcRemoteTargetClient
    : public rpc::SingleThreadedRPCEndpoint<rpc::RawByteChannel> {
public:
  /// Remote-mapped RuntimeDyld-compatible memory manager.
  class RemoteRTDyldMemoryManager : public RuntimeDyld::MemoryManager {
    friend class OrcRemoteTargetClient;

  public:
    ~RemoteRTDyldMemoryManager() {
      Client.destroyRemoteAllocator(Id);
      LLVM_DEBUG(dbgs() << "Destroyed remote allocator " << Id << "\n");
    }

    RemoteRTDyldMemoryManager(const RemoteRTDyldMemoryManager &) = delete;
    RemoteRTDyldMemoryManager &
    operator=(const RemoteRTDyldMemoryManager &) = delete;
    RemoteRTDyldMemoryManager(RemoteRTDyldMemoryManager &&) = default;
    RemoteRTDyldMemoryManager &operator=(RemoteRTDyldMemoryManager &&) = delete;

    uint8_t *allocateCodeSection(uintptr_t Size, unsigned Alignment,
                                 unsigned SectionID,
                                 StringRef SectionName) override {
      Unmapped.back().CodeAllocs.emplace_back(Size, Alignment);
      uint8_t *Alloc = reinterpret_cast<uint8_t *>(
          Unmapped.back().CodeAllocs.back().getLocalAddress());
      LLVM_DEBUG(dbgs() << "Allocator " << Id << " allocated code for "
                        << SectionName << ": " << Alloc << " (" << Size
                        << " bytes, alignment " << Alignment << ")\n");
      return Alloc;
    }

    uint8_t *allocateDataSection(uintptr_t Size, unsigned Alignment,
                                 unsigned SectionID, StringRef SectionName,
                                 bool IsReadOnly) override {
      if (IsReadOnly) {
        Unmapped.back().RODataAllocs.emplace_back(Size, Alignment);
        uint8_t *Alloc = reinterpret_cast<uint8_t *>(
            Unmapped.back().RODataAllocs.back().getLocalAddress());
        LLVM_DEBUG(dbgs() << "Allocator " << Id << " allocated ro-data for "
                          << SectionName << ": " << Alloc << " (" << Size
                          << " bytes, alignment " << Alignment << ")\n");
        return Alloc;
      } // else...

      Unmapped.back().RWDataAllocs.emplace_back(Size, Alignment);
      uint8_t *Alloc = reinterpret_cast<uint8_t *>(
          Unmapped.back().RWDataAllocs.back().getLocalAddress());
      LLVM_DEBUG(dbgs() << "Allocator " << Id << " allocated rw-data for "
                        << SectionName << ": " << Alloc << " (" << Size
                        << " bytes, alignment " << Alignment << ")\n");
      return Alloc;
    }

    void reserveAllocationSpace(uintptr_t CodeSize, uint32_t CodeAlign,
                                uintptr_t RODataSize, uint32_t RODataAlign,
                                uintptr_t RWDataSize,
                                uint32_t RWDataAlign) override {
      Unmapped.push_back(ObjectAllocs());

      LLVM_DEBUG(dbgs() << "Allocator " << Id << " reserved:\n");

      if (CodeSize != 0) {
        Unmapped.back().RemoteCodeAddr =
            Client.reserveMem(Id, CodeSize, CodeAlign);

        LLVM_DEBUG(
            dbgs() << "  code: "
                   << format("0x%016" PRIx64, Unmapped.back().RemoteCodeAddr)
                   << " (" << CodeSize << " bytes, alignment " << CodeAlign
                   << ")\n");
      }

      if (RODataSize != 0) {
        Unmapped.back().RemoteRODataAddr =
            Client.reserveMem(Id, RODataSize, RODataAlign);

        LLVM_DEBUG(
            dbgs() << "  ro-data: "
                   << format("0x%016" PRIx64, Unmapped.back().RemoteRODataAddr)
                   << " (" << RODataSize << " bytes, alignment " << RODataAlign
                   << ")\n");
      }

      if (RWDataSize != 0) {
        Unmapped.back().RemoteRWDataAddr =
            Client.reserveMem(Id, RWDataSize, RWDataAlign);

        LLVM_DEBUG(
            dbgs() << "  rw-data: "
                   << format("0x%016" PRIx64, Unmapped.back().RemoteRWDataAddr)
                   << " (" << RWDataSize << " bytes, alignment " << RWDataAlign
                   << ")\n");
      }
    }

    bool needsToReserveAllocationSpace() override { return true; }

    void registerEHFrames(uint8_t *Addr, uint64_t LoadAddr,
                          size_t Size) override {
      UnfinalizedEHFrames.push_back({LoadAddr, Size});
    }

    void deregisterEHFrames() override {
      for (auto &Frame : RegisteredEHFrames) {
        // FIXME: Add error poll.
        Client.deregisterEHFrames(Frame.Addr, Frame.Size);
      }
    }

    void notifyObjectLoaded(RuntimeDyld &Dyld,
                            const object::ObjectFile &Obj) override {
      LLVM_DEBUG(dbgs() << "Allocator " << Id << " applied mappings:\n");
      for (auto &ObjAllocs : Unmapped) {
        mapAllocsToRemoteAddrs(Dyld, ObjAllocs.CodeAllocs,
                               ObjAllocs.RemoteCodeAddr);
        mapAllocsToRemoteAddrs(Dyld, ObjAllocs.RODataAllocs,
                               ObjAllocs.RemoteRODataAddr);
        mapAllocsToRemoteAddrs(Dyld, ObjAllocs.RWDataAllocs,
                               ObjAllocs.RemoteRWDataAddr);
        Unfinalized.push_back(std::move(ObjAllocs));
      }
      Unmapped.clear();
    }

    bool finalizeMemory(std::string *ErrMsg = nullptr) override {
      LLVM_DEBUG(dbgs() << "Allocator " << Id << " finalizing:\n");

      for (auto &ObjAllocs : Unfinalized) {
        if (copyAndProtect(ObjAllocs.CodeAllocs, ObjAllocs.RemoteCodeAddr,
                           sys::Memory::MF_READ | sys::Memory::MF_EXEC))
          return true;

        if (copyAndProtect(ObjAllocs.RODataAllocs, ObjAllocs.RemoteRODataAddr,
                           sys::Memory::MF_READ))
          return true;

        if (copyAndProtect(ObjAllocs.RWDataAllocs, ObjAllocs.RemoteRWDataAddr,
                           sys::Memory::MF_READ | sys::Memory::MF_WRITE))
          return true;
      }
      Unfinalized.clear();

      for (auto &EHFrame : UnfinalizedEHFrames) {
        if (auto Err = Client.registerEHFrames(EHFrame.Addr, EHFrame.Size)) {
          // FIXME: Replace this once finalizeMemory can return an Error.
          handleAllErrors(std::move(Err), [&](ErrorInfoBase &EIB) {
            if (ErrMsg) {
              raw_string_ostream ErrOut(*ErrMsg);
              EIB.log(ErrOut);
            }
          });
          return false;
        }
      }
      RegisteredEHFrames = std::move(UnfinalizedEHFrames);
      UnfinalizedEHFrames = {};

      return false;
    }

  private:
    class Alloc {
    public:
      Alloc(uint64_t Size, unsigned Align)
          : Size(Size), Align(Align), Contents(new char[Size + Align - 1]) {}

      Alloc(const Alloc &) = delete;
      Alloc &operator=(const Alloc &) = delete;
      Alloc(Alloc &&) = default;
      Alloc &operator=(Alloc &&) = default;

      uint64_t getSize() const { return Size; }

      unsigned getAlign() const { return Align; }

      char *getLocalAddress() const {
        uintptr_t LocalAddr = reinterpret_cast<uintptr_t>(Contents.get());
        LocalAddr = alignTo(LocalAddr, Align);
        return reinterpret_cast<char *>(LocalAddr);
      }

      void setRemoteAddress(JITTargetAddress RemoteAddr) {
        this->RemoteAddr = RemoteAddr;
      }

      JITTargetAddress getRemoteAddress() const { return RemoteAddr; }

    private:
      uint64_t Size;
      unsigned Align;
      std::unique_ptr<char[]> Contents;
      JITTargetAddress RemoteAddr = 0;
    };

    struct ObjectAllocs {
      ObjectAllocs() = default;
      ObjectAllocs(const ObjectAllocs &) = delete;
      ObjectAllocs &operator=(const ObjectAllocs &) = delete;
      ObjectAllocs(ObjectAllocs &&) = default;
      ObjectAllocs &operator=(ObjectAllocs &&) = default;

      JITTargetAddress RemoteCodeAddr = 0;
      JITTargetAddress RemoteRODataAddr = 0;
      JITTargetAddress RemoteRWDataAddr = 0;
      std::vector<Alloc> CodeAllocs, RODataAllocs, RWDataAllocs;
    };

    RemoteRTDyldMemoryManager(OrcRemoteTargetClient &Client,
                              ResourceIdMgr::ResourceId Id)
        : Client(Client), Id(Id) {
      LLVM_DEBUG(dbgs() << "Created remote allocator " << Id << "\n");
    }

    // Maps all allocations in Allocs to aligned blocks
    void mapAllocsToRemoteAddrs(RuntimeDyld &Dyld, std::vector<Alloc> &Allocs,
                                JITTargetAddress NextAddr) {
      for (auto &Alloc : Allocs) {
        NextAddr = alignTo(NextAddr, Alloc.getAlign());
        Dyld.mapSectionAddress(Alloc.getLocalAddress(), NextAddr);
        LLVM_DEBUG(
            dbgs() << "     " << static_cast<void *>(Alloc.getLocalAddress())
                   << " -> " << format("0x%016" PRIx64, NextAddr) << "\n");
        Alloc.setRemoteAddress(NextAddr);

        // Only advance NextAddr if it was non-null to begin with,
        // otherwise leave it as null.
        if (NextAddr)
          NextAddr += Alloc.getSize();
      }
    }

    // Copies data for each alloc in the list, then set permissions on the
    // segment.
    bool copyAndProtect(const std::vector<Alloc> &Allocs,
                        JITTargetAddress RemoteSegmentAddr,
                        unsigned Permissions) {
      if (RemoteSegmentAddr) {
        assert(!Allocs.empty() && "No sections in allocated segment");

        for (auto &Alloc : Allocs) {
          LLVM_DEBUG(dbgs() << "  copying section: "
                            << static_cast<void *>(Alloc.getLocalAddress())
                            << " -> "
                            << format("0x%016" PRIx64, Alloc.getRemoteAddress())
                            << " (" << Alloc.getSize() << " bytes)\n";);

          if (Client.writeMem(Alloc.getRemoteAddress(), Alloc.getLocalAddress(),
                              Alloc.getSize()))
            return true;
        }

        LLVM_DEBUG(dbgs() << "  setting "
                          << (Permissions & sys::Memory::MF_READ ? 'R' : '-')
                          << (Permissions & sys::Memory::MF_WRITE ? 'W' : '-')
                          << (Permissions & sys::Memory::MF_EXEC ? 'X' : '-')
                          << " permissions on block: "
                          << format("0x%016" PRIx64, RemoteSegmentAddr)
                          << "\n");
        if (Client.setProtections(Id, RemoteSegmentAddr, Permissions))
          return true;
      }
      return false;
    }

    OrcRemoteTargetClient &Client;
    ResourceIdMgr::ResourceId Id;
    std::vector<ObjectAllocs> Unmapped;
    std::vector<ObjectAllocs> Unfinalized;

    struct EHFrame {
      JITTargetAddress Addr;
      uint64_t Size;
    };
    std::vector<EHFrame> UnfinalizedEHFrames;
    std::vector<EHFrame> RegisteredEHFrames;
  };

  class RPCMMAlloc : public jitlink::JITLinkMemoryManager::Allocation {
    using AllocationMap = DenseMap<unsigned, sys::MemoryBlock>;
    using FinalizeContinuation =
        jitlink::JITLinkMemoryManager::Allocation::FinalizeContinuation;
    using ProtectionFlags = sys::Memory::ProtectionFlags;
    using SegmentsRequestMap =
        DenseMap<unsigned, jitlink::JITLinkMemoryManager::SegmentRequest>;

    RPCMMAlloc(OrcRemoteTargetClient &Client, ResourceIdMgr::ResourceId Id)
        : Client(Client), Id(Id) {}

  public:
    static Expected<std::unique_ptr<RPCMMAlloc>>
    Create(OrcRemoteTargetClient &Client, ResourceIdMgr::ResourceId Id,
           const SegmentsRequestMap &Request) {
      auto *MM = new RPCMMAlloc(Client, Id);

      if (Error Err = MM->allocateHostBlocks(Request))
        return std::move(Err);

      if (Error Err = MM->allocateTargetBlocks())
        return std::move(Err);

      return std::unique_ptr<RPCMMAlloc>(MM);
    }

    MutableArrayRef<char> getWorkingMemory(ProtectionFlags Seg) override {
      assert(HostSegBlocks.count(Seg) && "No allocation for segment");
      return {static_cast<char *>(HostSegBlocks[Seg].base()),
              HostSegBlocks[Seg].allocatedSize()};
    }

    JITTargetAddress getTargetMemory(ProtectionFlags Seg) override {
      assert(TargetSegBlocks.count(Seg) && "No allocation for segment");
      return pointerToJITTargetAddress(TargetSegBlocks[Seg].base());
    }

    void finalizeAsync(FinalizeContinuation OnFinalize) override {
      // Host allocations (working memory) remain ReadWrite.
      OnFinalize(copyAndProtect());
    }

    Error deallocate() override {
      // TODO: Cannot release target allocation. RPCAPI has no function
      // symmetric to reserveMem(). Add RPC call like freeMem()?
      return errorCodeToError(sys::Memory::releaseMappedMemory(HostAllocation));
    }

  private:
    OrcRemoteTargetClient &Client;
    ResourceIdMgr::ResourceId Id;
    AllocationMap HostSegBlocks;
    AllocationMap TargetSegBlocks;
    JITTargetAddress TargetSegmentAddr;
    sys::MemoryBlock HostAllocation;

    Error allocateHostBlocks(const SegmentsRequestMap &Request) {
      unsigned TargetPageSize = Client.getPageSize();

      if (!isPowerOf2_64(static_cast<uint64_t>(TargetPageSize)))
        return make_error<StringError>("Host page size is not a power of 2",
                                       inconvertibleErrorCode());

      auto TotalSize = calcTotalAllocSize(Request, TargetPageSize);
      if (!TotalSize)
        return TotalSize.takeError();

      // Allocate one slab to cover all the segments.
      const sys::Memory::ProtectionFlags ReadWrite =
          static_cast<sys::Memory::ProtectionFlags>(sys::Memory::MF_READ |
                                                    sys::Memory::MF_WRITE);
      std::error_code EC;
      HostAllocation =
          sys::Memory::allocateMappedMemory(*TotalSize, nullptr, ReadWrite, EC);
      if (EC)
        return errorCodeToError(EC);

      char *SlabAddr = static_cast<char *>(HostAllocation.base());
#ifndef NDEBUG
      char *SlabAddrEnd = SlabAddr + HostAllocation.allocatedSize();
#endif

      // Allocate segment memory from the slab.
      for (auto &KV : Request) {
        const auto &Seg = KV.second;

        uint64_t SegmentSize = Seg.getContentSize() + Seg.getZeroFillSize();
        uint64_t AlignedSegmentSize = alignTo(SegmentSize, TargetPageSize);

        // Zero out zero-fill memory.
        char *ZeroFillBegin = SlabAddr + Seg.getContentSize();
        memset(ZeroFillBegin, 0, Seg.getZeroFillSize());

        // Record the block for this segment.
        HostSegBlocks[KV.first] =
            sys::MemoryBlock(SlabAddr, AlignedSegmentSize);

        SlabAddr += AlignedSegmentSize;
        assert(SlabAddr <= SlabAddrEnd && "Out of range");
      }

      return Error::success();
    }

    Error allocateTargetBlocks() {
      // Reserve memory for all blocks on the target. We need as much space on
      // the target as we allocated on the host.
      TargetSegmentAddr = Client.reserveMem(Id, HostAllocation.allocatedSize(),
                                            Client.getPageSize());
      if (!TargetSegmentAddr)
        return make_error<StringError>("Failed to reserve memory on the target",
                                       inconvertibleErrorCode());

      // Map memory blocks into the allocation, that match the host allocation.
      JITTargetAddress TargetAllocAddr = TargetSegmentAddr;
      for (const auto &KV : HostSegBlocks) {
        size_t TargetAllocSize = KV.second.allocatedSize();

        TargetSegBlocks[KV.first] =
            sys::MemoryBlock(jitTargetAddressToPointer<void *>(TargetAllocAddr),
                             TargetAllocSize);

        TargetAllocAddr += TargetAllocSize;
        assert(TargetAllocAddr - TargetSegmentAddr <=
                   HostAllocation.allocatedSize() &&
               "Out of range on target");
      }

      return Error::success();
    }

    Error copyAndProtect() {
      unsigned Permissions = 0u;

      // Copy segments one by one.
      for (auto &KV : TargetSegBlocks) {
        Permissions |= KV.first;

        const sys::MemoryBlock &TargetBlock = KV.second;
        const sys::MemoryBlock &HostBlock = HostSegBlocks.lookup(KV.first);

        size_t TargetAllocSize = TargetBlock.allocatedSize();
        auto TargetAllocAddr = pointerToJITTargetAddress(TargetBlock.base());
        auto *HostAllocBegin = static_cast<const char *>(HostBlock.base());

        bool CopyErr =
            Client.writeMem(TargetAllocAddr, HostAllocBegin, TargetAllocSize);
        if (CopyErr)
          return createStringError(inconvertibleErrorCode(),
                                   "Failed to copy %d segment to the target",
                                   KV.first);
      }

      // Set permission flags for all segments at once.
      bool ProtectErr =
          Client.setProtections(Id, TargetSegmentAddr, Permissions);
      if (ProtectErr)
        return createStringError(inconvertibleErrorCode(),
                                 "Failed to apply permissions for %d segment "
                                 "on the target",
                                 Permissions);
      return Error::success();
    }

    static Expected<size_t>
    calcTotalAllocSize(const SegmentsRequestMap &Request,
                       unsigned TargetPageSize) {
      size_t TotalSize = 0;
      for (const auto &KV : Request) {
        const auto &Seg = KV.second;

        if (Seg.getAlignment() > TargetPageSize)
          return make_error<StringError>("Cannot request alignment higher than "
                                         "page alignment on target",
                                         inconvertibleErrorCode());

        TotalSize = alignTo(TotalSize, TargetPageSize);
        TotalSize += Seg.getContentSize();
        TotalSize += Seg.getZeroFillSize();
      }

      return TotalSize;
    }
  };

  class RemoteJITLinkMemoryManager : public jitlink::JITLinkMemoryManager {
  public:
    RemoteJITLinkMemoryManager(OrcRemoteTargetClient &Client,
                               ResourceIdMgr::ResourceId Id)
        : Client(Client), Id(Id) {}

    RemoteJITLinkMemoryManager(const RemoteJITLinkMemoryManager &) = delete;
    RemoteJITLinkMemoryManager(RemoteJITLinkMemoryManager &&) = default;

    RemoteJITLinkMemoryManager &
    operator=(const RemoteJITLinkMemoryManager &) = delete;
    RemoteJITLinkMemoryManager &
    operator=(RemoteJITLinkMemoryManager &&) = delete;

    ~RemoteJITLinkMemoryManager() {
      Client.destroyRemoteAllocator(Id);
      LLVM_DEBUG(dbgs() << "Destroyed remote allocator " << Id << "\n");
    }

    Expected<std::unique_ptr<Allocation>>
    allocate(const SegmentsRequestMap &Request) override {
      return RPCMMAlloc::Create(Client, Id, Request);
    }

  private:
    OrcRemoteTargetClient &Client;
    ResourceIdMgr::ResourceId Id;
  };

  /// Remote indirect stubs manager.
  class RemoteIndirectStubsManager : public IndirectStubsManager {
  public:
    RemoteIndirectStubsManager(OrcRemoteTargetClient &Client,
                               ResourceIdMgr::ResourceId Id)
        : Client(Client), Id(Id) {}

    ~RemoteIndirectStubsManager() override {
      Client.destroyIndirectStubsManager(Id);
    }

    Error createStub(StringRef StubName, JITTargetAddress StubAddr,
                     JITSymbolFlags StubFlags) override {
      if (auto Err = reserveStubs(1))
        return Err;

      return createStubInternal(StubName, StubAddr, StubFlags);
    }

    Error createStubs(const StubInitsMap &StubInits) override {
      if (auto Err = reserveStubs(StubInits.size()))
        return Err;

      for (auto &Entry : StubInits)
        if (auto Err = createStubInternal(Entry.first(), Entry.second.first,
                                          Entry.second.second))
          return Err;

      return Error::success();
    }

    JITEvaluatedSymbol findStub(StringRef Name, bool ExportedStubsOnly) override {
      auto I = StubIndexes.find(Name);
      if (I == StubIndexes.end())
        return nullptr;
      auto Key = I->second.first;
      auto Flags = I->second.second;
      auto StubSymbol = JITEvaluatedSymbol(getStubAddr(Key), Flags);
      if (ExportedStubsOnly && !StubSymbol.getFlags().isExported())
        return nullptr;
      return StubSymbol;
    }

    JITEvaluatedSymbol findPointer(StringRef Name) override {
      auto I = StubIndexes.find(Name);
      if (I == StubIndexes.end())
        return nullptr;
      auto Key = I->second.first;
      auto Flags = I->second.second;
      return JITEvaluatedSymbol(getPtrAddr(Key), Flags);
    }

    Error updatePointer(StringRef Name, JITTargetAddress NewAddr) override {
      auto I = StubIndexes.find(Name);
      assert(I != StubIndexes.end() && "No stub pointer for symbol");
      auto Key = I->second.first;
      return Client.writePointer(getPtrAddr(Key), NewAddr);
    }

  private:
    struct RemoteIndirectStubsInfo {
      JITTargetAddress StubBase;
      JITTargetAddress PtrBase;
      unsigned NumStubs;
    };

    using StubKey = std::pair<uint16_t, uint16_t>;

    Error reserveStubs(unsigned NumStubs) {
      if (NumStubs <= FreeStubs.size())
        return Error::success();

      unsigned NewStubsRequired = NumStubs - FreeStubs.size();
      JITTargetAddress StubBase;
      JITTargetAddress PtrBase;
      unsigned NumStubsEmitted;

      if (auto StubInfoOrErr = Client.emitIndirectStubs(Id, NewStubsRequired))
        std::tie(StubBase, PtrBase, NumStubsEmitted) = *StubInfoOrErr;
      else
        return StubInfoOrErr.takeError();

      unsigned NewBlockId = RemoteIndirectStubsInfos.size();
      RemoteIndirectStubsInfos.push_back({StubBase, PtrBase, NumStubsEmitted});

      for (unsigned I = 0; I < NumStubsEmitted; ++I)
        FreeStubs.push_back(std::make_pair(NewBlockId, I));

      return Error::success();
    }

    Error createStubInternal(StringRef StubName, JITTargetAddress InitAddr,
                             JITSymbolFlags StubFlags) {
      auto Key = FreeStubs.back();
      FreeStubs.pop_back();
      StubIndexes[StubName] = std::make_pair(Key, StubFlags);
      return Client.writePointer(getPtrAddr(Key), InitAddr);
    }

    JITTargetAddress getStubAddr(StubKey K) {
      assert(RemoteIndirectStubsInfos[K.first].StubBase != 0 &&
             "Missing stub address");
      return RemoteIndirectStubsInfos[K.first].StubBase +
             K.second * Client.getIndirectStubSize();
    }

    JITTargetAddress getPtrAddr(StubKey K) {
      assert(RemoteIndirectStubsInfos[K.first].PtrBase != 0 &&
             "Missing pointer address");
      return RemoteIndirectStubsInfos[K.first].PtrBase +
             K.second * Client.getPointerSize();
    }

    OrcRemoteTargetClient &Client;
    ResourceIdMgr::ResourceId Id;
    std::vector<RemoteIndirectStubsInfo> RemoteIndirectStubsInfos;
    std::vector<StubKey> FreeStubs;
    StringMap<std::pair<StubKey, JITSymbolFlags>> StubIndexes;
  };

  class RemoteTrampolinePool : public TrampolinePool {
  public:
    RemoteTrampolinePool(OrcRemoteTargetClient &Client) : Client(Client) {}

  private:
    Error grow() override {
      JITTargetAddress BlockAddr = 0;
      uint32_t NumTrampolines = 0;
      if (auto TrampolineInfoOrErr = Client.emitTrampolineBlock())
        std::tie(BlockAddr, NumTrampolines) = *TrampolineInfoOrErr;
      else
        return TrampolineInfoOrErr.takeError();

      uint32_t TrampolineSize = Client.getTrampolineSize();
      for (unsigned I = 0; I < NumTrampolines; ++I)
        AvailableTrampolines.push_back(BlockAddr + (I * TrampolineSize));

      return Error::success();
    }

    OrcRemoteTargetClient &Client;
  };

  /// Remote compile callback manager.
  class RemoteCompileCallbackManager : public JITCompileCallbackManager {
  public:
    RemoteCompileCallbackManager(OrcRemoteTargetClient &Client,
                                 ExecutionSession &ES,
                                 JITTargetAddress ErrorHandlerAddress)
        : JITCompileCallbackManager(
              std::make_unique<RemoteTrampolinePool>(Client), ES,
              ErrorHandlerAddress) {}
  };

  /// Create an OrcRemoteTargetClient.
  /// Channel is the ChannelT instance to communicate on. It is assumed that
  /// the channel is ready to be read from and written to.
  static Expected<std::unique_ptr<OrcRemoteTargetClient>>
  Create(rpc::RawByteChannel &Channel, ExecutionSession &ES) {
    Error Err = Error::success();
    auto Client = std::unique_ptr<OrcRemoteTargetClient>(
        new OrcRemoteTargetClient(Channel, ES, Err));
    if (Err)
      return std::move(Err);
    return std::move(Client);
  }

  /// Call the int(void) function at the given address in the target and return
  /// its result.
  Expected<int> callIntVoid(JITTargetAddress Addr) {
    LLVM_DEBUG(dbgs() << "Calling int(*)(void) "
                      << format("0x%016" PRIx64, Addr) << "\n");
    return callB<exec::CallIntVoid>(Addr);
  }

  /// Call the int(int) function at the given address in the target and return
  /// its result.
  Expected<int> callIntInt(JITTargetAddress Addr, int Arg) {
    LLVM_DEBUG(dbgs() << "Calling int(*)(int) " << format("0x%016" PRIx64, Addr)
                      << "\n");
    return callB<exec::CallIntInt>(Addr, Arg);
  }

  /// Call the int(int, char*[]) function at the given address in the target and
  /// return its result.
  Expected<int> callMain(JITTargetAddress Addr,
                         const std::vector<std::string> &Args) {
    LLVM_DEBUG(dbgs() << "Calling int(*)(int, char*[]) "
                      << format("0x%016" PRIx64, Addr) << "\n");
    return callB<exec::CallMain>(Addr, Args);
  }

  /// Call the void() function at the given address in the target and wait for
  /// it to finish.
  Error callVoidVoid(JITTargetAddress Addr) {
    LLVM_DEBUG(dbgs() << "Calling void(*)(void) "
                      << format("0x%016" PRIx64, Addr) << "\n");
    return callB<exec::CallVoidVoid>(Addr);
  }

  /// Create an RCMemoryManager which will allocate its memory on the remote
  /// target.
  Expected<std::unique_ptr<RemoteRTDyldMemoryManager>>
  createRemoteMemoryManager() {
    auto Id = AllocatorIds.getNext();
    if (auto Err = callB<mem::CreateRemoteAllocator>(Id))
      return std::move(Err);
    return std::unique_ptr<RemoteRTDyldMemoryManager>(
        new RemoteRTDyldMemoryManager(*this, Id));
  }

  /// Create a JITLink-compatible memory manager which will allocate working
  /// memory on the host and target memory on the remote target.
  Expected<std::unique_ptr<RemoteJITLinkMemoryManager>>
  createRemoteJITLinkMemoryManager() {
    auto Id = AllocatorIds.getNext();
    if (auto Err = callB<mem::CreateRemoteAllocator>(Id))
      return std::move(Err);
    LLVM_DEBUG(dbgs() << "Created remote allocator " << Id << "\n");
    return std::unique_ptr<RemoteJITLinkMemoryManager>(
        new RemoteJITLinkMemoryManager(*this, Id));
  }

  /// Create an RCIndirectStubsManager that will allocate stubs on the remote
  /// target.
  Expected<std::unique_ptr<RemoteIndirectStubsManager>>
  createIndirectStubsManager() {
    auto Id = IndirectStubOwnerIds.getNext();
    if (auto Err = callB<stubs::CreateIndirectStubsOwner>(Id))
      return std::move(Err);
    return std::make_unique<RemoteIndirectStubsManager>(*this, Id);
  }

  Expected<RemoteCompileCallbackManager &>
  enableCompileCallbacks(JITTargetAddress ErrorHandlerAddress) {
    assert(!CallbackManager && "CallbackManager already obtained");

    // Emit the resolver block on the JIT server.
    if (auto Err = callB<stubs::EmitResolverBlock>())
      return std::move(Err);

    // Create the callback manager.
    CallbackManager.emplace(*this, ES, ErrorHandlerAddress);
    RemoteCompileCallbackManager &Mgr = *CallbackManager;
    return Mgr;
  }

  /// Search for symbols in the remote process. Note: This should be used by
  /// symbol resolvers *after* they've searched the local symbol table in the
  /// JIT stack.
  Expected<JITTargetAddress> getSymbolAddress(StringRef Name) {
    return callB<utils::GetSymbolAddress>(Name);
  }

  /// Get the triple for the remote target.
  const std::string &getTargetTriple() const { return RemoteTargetTriple; }

  Error terminateSession() { return callB<utils::TerminateSession>(); }

private:
  OrcRemoteTargetClient(rpc::RawByteChannel &Channel, ExecutionSession &ES,
                        Error &Err)
      : rpc::SingleThreadedRPCEndpoint<rpc::RawByteChannel>(Channel, true),
        ES(ES) {
    ErrorAsOutParameter EAO(&Err);

    addHandler<utils::RequestCompile>(
        [this](JITTargetAddress Addr) -> JITTargetAddress {
          if (CallbackManager)
            return CallbackManager->executeCompileCallback(Addr);
          return 0;
        });

    if (auto RIOrErr = callB<utils::GetRemoteInfo>()) {
      std::tie(RemoteTargetTriple, RemotePointerSize, RemotePageSize,
               RemoteTrampolineSize, RemoteIndirectStubSize) = *RIOrErr;
      Err = Error::success();
    } else
      Err = RIOrErr.takeError();
  }

  void deregisterEHFrames(JITTargetAddress Addr, uint32_t Size) {
    if (auto Err = callB<eh::RegisterEHFrames>(Addr, Size))
      ES.reportError(std::move(Err));
  }

  void destroyRemoteAllocator(ResourceIdMgr::ResourceId Id) {
    if (auto Err = callB<mem::DestroyRemoteAllocator>(Id)) {
      // FIXME: This will be triggered by a removeModuleSet call: Propagate
      //        error return up through that.
      llvm_unreachable("Failed to destroy remote allocator.");
      AllocatorIds.release(Id);
    }
  }

  void destroyIndirectStubsManager(ResourceIdMgr::ResourceId Id) {
    IndirectStubOwnerIds.release(Id);
    if (auto Err = callB<stubs::DestroyIndirectStubsOwner>(Id))
      ES.reportError(std::move(Err));
  }

  Expected<std::tuple<JITTargetAddress, JITTargetAddress, uint32_t>>
  emitIndirectStubs(ResourceIdMgr::ResourceId Id, uint32_t NumStubsRequired) {
    return callB<stubs::EmitIndirectStubs>(Id, NumStubsRequired);
  }

  Expected<std::tuple<JITTargetAddress, uint32_t>> emitTrampolineBlock() {
    return callB<stubs::EmitTrampolineBlock>();
  }

  uint32_t getIndirectStubSize() const { return RemoteIndirectStubSize; }
  uint32_t getPageSize() const { return RemotePageSize; }
  uint32_t getPointerSize() const { return RemotePointerSize; }

  uint32_t getTrampolineSize() const { return RemoteTrampolineSize; }

  Expected<std::vector<uint8_t>> readMem(char *Dst, JITTargetAddress Src,
                                         uint64_t Size) {
    return callB<mem::ReadMem>(Src, Size);
  }

  Error registerEHFrames(JITTargetAddress &RAddr, uint32_t Size) {
    // FIXME: Duplicate error and report it via ReportError too?
    return callB<eh::RegisterEHFrames>(RAddr, Size);
  }

  JITTargetAddress reserveMem(ResourceIdMgr::ResourceId Id, uint64_t Size,
                              uint32_t Align) {
    if (auto AddrOrErr = callB<mem::ReserveMem>(Id, Size, Align))
      return *AddrOrErr;
    else {
      ES.reportError(AddrOrErr.takeError());
      return 0;
    }
  }

  bool setProtections(ResourceIdMgr::ResourceId Id,
                      JITTargetAddress RemoteSegAddr, unsigned ProtFlags) {
    if (auto Err = callB<mem::SetProtections>(Id, RemoteSegAddr, ProtFlags)) {
      ES.reportError(std::move(Err));
      return true;
    } else
      return false;
  }

  bool writeMem(JITTargetAddress Addr, const char *Src, uint64_t Size) {
    if (auto Err = callB<mem::WriteMem>(DirectBufferWriter(Src, Addr, Size))) {
      ES.reportError(std::move(Err));
      return true;
    } else
      return false;
  }

  Error writePointer(JITTargetAddress Addr, JITTargetAddress PtrVal) {
    return callB<mem::WritePtr>(Addr, PtrVal);
  }

  static Error doNothing() { return Error::success(); }

  ExecutionSession &ES;
  std::function<void(Error)> ReportError;
  std::string RemoteTargetTriple;
  uint32_t RemotePointerSize = 0;
  uint32_t RemotePageSize = 0;
  uint32_t RemoteTrampolineSize = 0;
  uint32_t RemoteIndirectStubSize = 0;
  ResourceIdMgr AllocatorIds, IndirectStubOwnerIds;
  Optional<RemoteCompileCallbackManager> CallbackManager;
};

} // end namespace remote
} // end namespace orc
} // end namespace llvm

#undef DEBUG_TYPE

#endif // LLVM_EXECUTIONENGINE_ORC_ORCREMOTETARGETCLIENT_H