[ORC] Add SimpleRemoteEPC: ExecutorProcessControl over SPS + abstract transport.

SimpleRemoteEPC is an ExecutorProcessControl implementation (with corresponding
new server class) that uses ORC SimplePackedSerialization (SPS) to serialize and
deserialize EPC-messages to/from byte-buffers. The byte-buffers are sent and
received via a new SimpleRemoteEPCTransport interface that can be implemented to
run SimpleRemoteEPC over whatever underlying transport system (IPC, RPC, network
sockets, etc.) best suits your use case.

The SimpleRemoteEPCServer class provides executor-side support. It uses a
customizable SimpleRemoteEPCServer::Dispatcher object to dispatch wrapper
function calls to prevent the RPC thread from being blocked (a problem in some
earlier remote-JIT server implementations). Almost all functionality (beyond the
bare basics needed to bootstrap) is implemented as wrapper functions to keep the
implementation simple and uniform.

Compared to previous remote JIT utilities (OrcRemoteTarget*,
OrcRPCExecutorProcessControl), more consideration has been given to
disconnection and error handling behavior: Graceful disconnection is now always
initiated by the ORC side of the connection, and failure at either end (or in
the transport) will result in Errors being delivered to both ends to enable
controlled tear-down of the JIT and Executor (in the Executor's case this means
"as controlled as the JIT'd code allows").

The introduction of SimpleRemoteEPC will allow us to remove other remote-JIT
support from ORC (including the legacy OrcRemoteTarget* code used by lli, and
the OrcRPCExecutorProcessControl and OrcRPCEPCServer classes), and then remove
ORC RPC itself.

The llvm-jitlink and llvm-jitlink-executor tools have been updated to use
SimpleRemoteEPC over file descriptors. Future commits will move lli and other
tools and example code to this system, and remove ORC RPC.

Author: lhames

llvm/include/llvm/ExecutionEngine/Orc/Core.h

@@ -1302,7 +1302,8 @@ class ExecutionSession {
   /// object.
   ExecutionSession(std::unique_ptr<ExecutorProcessControl> EPC);
 
-  /// End the session. Closes all JITDylibs.
+  /// End the session. Closes all JITDylibs and disconnects from the
+  /// executor.
   Error endSession();
 
   /// Get the ExecutorProcessControl object associated with this

llvm/include/llvm/ExecutionEngine/Orc/EPCGenericJITLinkMemoryManager.h

@@ -38,11 +38,6 @@ class EPCGenericJITLinkMemoryManager : public jitlink::JITLinkMemoryManager {
   EPCGenericJITLinkMemoryManager(ExecutorProcessControl &EPC, FuncAddrs FAs)
       : EPC(EPC), FAs(FAs) {}
 
-  /// Create using the standard memory allocation function names from the
-  /// ORCTargetProcess library.
-  static Expected<std::unique_ptr<EPCGenericJITLinkMemoryManager>>
-  CreateUsingOrcRTFuncs(ExecutorProcessControl &EPC);
-
   Expected<std::unique_ptr<Allocation>>
   allocate(const jitlink::JITLinkDylib *JD,
            const SegmentsRequestMap &Request) override;

llvm/include/llvm/ExecutionEngine/Orc/EPCGenericMemoryAccess.h

@@ -39,11 +39,6 @@ class EPCGenericMemoryAccess : public ExecutorProcessControl::MemoryAccess {
   EPCGenericMemoryAccess(ExecutorProcessControl &EPC, FuncAddrs FAs)
       : EPC(EPC), FAs(FAs) {}
 
-  /// Create using the standard memory access function names from the
-  /// ORCTargetProcess library.
-  static Expected<std::unique_ptr<EPCGenericMemoryAccess>>
-  CreateUsingOrcRTFuncs(ExecutorProcessControl &EPC);
-
   void writeUInt8sAsync(ArrayRef<tpctypes::UInt8Write> Ws,
                         WriteResultFn OnWriteComplete) override {
     using namespace shared;

llvm/include/llvm/ExecutionEngine/Orc/Shared/SimpleRemoteEPCUtils.h

@@ -0,0 +1,249 @@
+//===--- SimpleRemoteEPCUtils.h - Utils for Simple Remote EPC ---*- 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
+//
+//===----------------------------------------------------------------------===//
+//
+// Message definitions and other utilities for SimpleRemoteEPC and
+// SimpleRemoteEPCServer.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_EXECUTIONENGINE_ORC_SHARED_SIMPLEREMOTEEPCUTILS_H
+#define LLVM_EXECUTIONENGINE_ORC_SHARED_SIMPLEREMOTEEPCUTILS_H
+
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/StringMap.h"
+#include "llvm/ExecutionEngine/Orc/Shared/ExecutorAddress.h"
+#include "llvm/ExecutionEngine/Orc/Shared/SimplePackedSerialization.h"
+#include "llvm/Support/Error.h"
+
+#include <string>
+#include <thread>
+
+namespace llvm {
+namespace orc {
+
+namespace SimpleRemoteEPCDefaultBootstrapSymbolNames {
+extern const char *ExecutorSessionObjectName;
+extern const char *DispatchFnName;
+} // end namespace SimpleRemoteEPCDefaultBootstrapSymbolNames
+
+enum class SimpleRemoteEPCOpcode : uint8_t {
+  FirstOpC,
+  Setup = FirstOpC,
+  Hangup,
+  Result,
+  CallWrapper,
+  LastOpC = CallWrapper
+};
+
+struct SimpleRemoteEPCExecutorInfo {
+  std::string TargetTriple;
+  uint64_t PageSize;
+  StringMap<ExecutorAddress> BootstrapSymbols;
+
+  Expected<ExecutorAddress> getBootstrapSymbol(StringRef Name) const {
+    auto I = BootstrapSymbols.find(Name);
+    if (I == BootstrapSymbols.end())
+      return make_error<StringError>("Symbol \"" + Name +
+                                         "\" not found in "
+                                         "bootstrap symbols map",
+                                     inconvertibleErrorCode());
+    return I->second;
+  }
+
+  Error getBootstrapSymbols(
+      ArrayRef<std::pair<ExecutorAddress &, StringRef>> Pairs) const {
+    for (auto &KV : Pairs) {
+      if (auto A = getBootstrapSymbol(KV.second))
+        KV.first = *A;
+      else
+        return A.takeError();
+    }
+    return Error::success();
+  }
+};
+
+using SimpleRemoteEPCArgBytesVector = SmallVector<char, 128>;
+
+class SimpleRemoteEPCTransportClient {
+public:
+  enum HandleMessageAction { ContinueSession, EndSession };
+
+  virtual ~SimpleRemoteEPCTransportClient();
+
+  /// Handle receipt of a message.
+  ///
+  /// Returns an Error if the message cannot be handled, 'EndSession' if the
+  /// client will not accept any further messages, and 'ContinueSession'
+  /// otherwise.
+  virtual Expected<HandleMessageAction>
+  handleMessage(SimpleRemoteEPCOpcode OpC, uint64_t SeqNo,
+                ExecutorAddress TagAddr,
+                SimpleRemoteEPCArgBytesVector ArgBytes) = 0;
+
+  /// Handle a disconnection from the underlying transport. No further messages
+  /// should be sent to handleMessage after this is called.
+  /// Err may contain an Error value indicating unexpected disconnection. This
+  /// allows clients to log such errors, but no attempt should be made at
+  /// recovery (which should be handled inside the transport class, if it is
+  /// supported at all).
+  virtual void handleDisconnect(Error Err) = 0;
+};
+
+class SimpleRemoteEPCTransport {
+public:
+  virtual ~SimpleRemoteEPCTransport();
+
+  /// Send a SimpleRemoteEPC message.
+  ///
+  /// This function may be called concurrently. Subclasses should implement
+  /// locking if required for the underlying transport.
+  virtual Error sendMessage(SimpleRemoteEPCOpcode OpC, uint64_t SeqNo,
+                            ExecutorAddress TagAddr,
+                            ArrayRef<char> ArgBytes) = 0;
+
+  /// Trigger disconnection from the transport. The implementation should
+  /// respond by calling handleDisconnect on the client once disconnection
+  /// is complete.
+  virtual void disconnect() = 0;
+};
+
+/// Uses read/write on FileDescriptors for transport.
+class FDSimpleRemoteEPCTransport : public SimpleRemoteEPCTransport {
+public:
+  /// Create a FDSimpleRemoteEPCTransport using the given FDs for
+  /// reading (InFD) and writing (OutFD).
+  static Expected<std::unique_ptr<FDSimpleRemoteEPCTransport>>
+  Create(SimpleRemoteEPCTransportClient &C, int InFD, int OutFD);
+
+  /// Create a FDSimpleRemoteEPCTransport using the given FD for both
+  /// reading and writing.
+  static Expected<std::unique_ptr<FDSimpleRemoteEPCTransport>>
+  Create(SimpleRemoteEPCTransportClient &C, int FD) {
+    return Create(C, FD, FD);
+  }
+
+  ~FDSimpleRemoteEPCTransport() override;
+
+  Error sendMessage(SimpleRemoteEPCOpcode OpC, uint64_t SeqNo,
+                    ExecutorAddress TagAddr, ArrayRef<char> ArgBytes) override;
+
+  void disconnect() override;
+
+private:
+  FDSimpleRemoteEPCTransport(SimpleRemoteEPCTransportClient &C, int InFD,
+                             int OutFD);
+
+  Error readBytes(char *Dst, size_t Size, bool *IsEOF = nullptr);
+  int writeBytes(const char *Src, size_t Size);
+  void listenLoop();
+
+  std::mutex M;
+  SimpleRemoteEPCTransportClient &C;
+  std::thread ListenerThread;
+  int InFD, OutFD;
+};
+
+struct RemoteSymbolLookupSetElement {
+  std::string Name;
+  bool Required;
+};
+
+using RemoteSymbolLookupSet = std::vector<RemoteSymbolLookupSetElement>;
+
+struct RemoteSymbolLookup {
+  uint64_t H;
+  RemoteSymbolLookupSet Symbols;
+};
+
+namespace shared {
+
+using SPSRemoteSymbolLookupSetElement = SPSTuple<SPSString, bool>;
+
+using SPSRemoteSymbolLookupSet = SPSSequence<SPSRemoteSymbolLookupSetElement>;
+
+using SPSRemoteSymbolLookup = SPSTuple<uint64_t, SPSRemoteSymbolLookupSet>;
+
+/// Tuple containing target triple, page size, and bootstrap symbols.
+using SPSSimpleRemoteEPCExecutorInfo =
+    SPSTuple<SPSString, uint64_t,
+             SPSSequence<SPSTuple<SPSString, SPSExecutorAddress>>>;
+
+template <>
+class SPSSerializationTraits<SPSRemoteSymbolLookupSetElement,
+                             RemoteSymbolLookupSetElement> {
+public:
+  static size_t size(const RemoteSymbolLookupSetElement &V) {
+    return SPSArgList<SPSString, bool>::size(V.Name, V.Required);
+  }
+
+  static size_t serialize(SPSOutputBuffer &OB,
+                          const RemoteSymbolLookupSetElement &V) {
+    return SPSArgList<SPSString, bool>::serialize(OB, V.Name, V.Required);
+  }
+
+  static size_t deserialize(SPSInputBuffer &IB,
+                            RemoteSymbolLookupSetElement &V) {
+    return SPSArgList<SPSString, bool>::deserialize(IB, V.Name, V.Required);
+  }
+};
+
+template <>
+class SPSSerializationTraits<SPSRemoteSymbolLookup, RemoteSymbolLookup> {
+public:
+  static size_t size(const RemoteSymbolLookup &V) {
+    return SPSArgList<uint64_t, SPSRemoteSymbolLookupSet>::size(V.H, V.Symbols);
+  }
+
+  static size_t serialize(SPSOutputBuffer &OB, const RemoteSymbolLookup &V) {
+    return SPSArgList<uint64_t, SPSRemoteSymbolLookupSet>::serialize(OB, V.H,
+                                                                     V.Symbols);
+  }
+
+  static size_t deserialize(SPSInputBuffer &IB, RemoteSymbolLookup &V) {
+    return SPSArgList<uint64_t, SPSRemoteSymbolLookupSet>::deserialize(
+        IB, V.H, V.Symbols);
+  }
+};
+
+template <>
+class SPSSerializationTraits<SPSSimpleRemoteEPCExecutorInfo,
+                             SimpleRemoteEPCExecutorInfo> {
+public:
+  static size_t size(const SimpleRemoteEPCExecutorInfo &SI) {
+    return SPSSimpleRemoteEPCExecutorInfo::AsArgList ::size(
+        SI.TargetTriple, SI.PageSize, SI.BootstrapSymbols);
+  }
+
+  static bool serialize(SPSOutputBuffer &OB,
+                        const SimpleRemoteEPCExecutorInfo &SI) {
+    return SPSSimpleRemoteEPCExecutorInfo::AsArgList ::serialize(
+        OB, SI.TargetTriple, SI.PageSize, SI.BootstrapSymbols);
+  }
+
+  static bool deserialize(SPSInputBuffer &IB, SimpleRemoteEPCExecutorInfo &SI) {
+    return SPSSimpleRemoteEPCExecutorInfo::AsArgList ::deserialize(
+        IB, SI.TargetTriple, SI.PageSize, SI.BootstrapSymbols);
+  }
+};
+
+using SPSRunAsMainSignature = int64_t(SPSExecutorAddress,
+                                      SPSSequence<SPSString>);
+
+using SPSLoadDylibSignature =
+    SPSExpected<SPSExecutorAddress>(SPSExecutorAddress, SPSString, uint64_t);
+
+using SPSLookupSymbolsSignature =
+    SPSExpected<SPSSequence<SPSSequence<SPSExecutorAddress>>>(
+        SPSExecutorAddress, SPSSequence<SPSRemoteSymbolLookup>);
+
+} // end namespace shared
+} // end namespace orc
+} // end namespace llvm
+
+#endif // LLVM_EXECUTIONENGINE_ORC_SHARED_SIMPLEREMOTEEPCUTILS_H