[Orc] Handle hangup messages in SimpleRemoteEPC

On the controller-side, handle `Hangup` messages from the executor. The executor passed `Error::success()` or a failure message as payload.

Hangups cause an immediate disconnect of the transport layer. The disconnect function may be called later again and so implementations should be prepared. `FDSimpleRemoteEPCTransport::disconnect()` already has a flag to check that:
cd1bd95d87/llvm/lib/ExecutionEngine/Orc/Shared/SimpleRemoteEPCUtils.cpp (L112)

Reviewed By: lhames

Differential Revision: https://reviews.llvm.org/D111527

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

@@ -94,7 +94,7 @@ public:
 
   /// Trigger disconnection from the transport. The implementation should
   /// respond by calling handleDisconnect on the client once disconnection
-  /// is complete.
+  /// is complete. May be called more than once and from different threads.
   virtual void disconnect() = 0;
 };
 

llvm/include/llvm/ExecutionEngine/Orc/SimpleRemoteEPC.h

@@ -96,6 +96,7 @@ private:
                      SimpleRemoteEPCArgBytesVector ArgBytes);
   void handleCallWrapper(uint64_t RemoteSeqNo, ExecutorAddr TagAddr,
                          SimpleRemoteEPCArgBytesVector ArgBytes);
+  Error handleHangup(SimpleRemoteEPCArgBytesVector ArgBytes);
 
   uint64_t getNextSeqNo() { return NextSeqNo++; }
   void releaseSeqNo(uint64_t SeqNo) {}

llvm/lib/ExecutionEngine/Orc/SimpleRemoteEPC.cpp

@@ -121,8 +121,10 @@ SimpleRemoteEPC::handleMessage(SimpleRemoteEPCOpcode OpC, uint64_t SeqNo,
       return std::move(Err);
     break;
   case SimpleRemoteEPCOpcode::Hangup:
-    return make_error<StringError>("Unexpected Hangup opcode",
-                                   inconvertibleErrorCode());
+    T->disconnect();
+    if (auto Err = handleHangup(std::move(ArgBytes)))
+      return std::move(Err);
+    return EndSession;
   case SimpleRemoteEPCOpcode::Result:
     if (auto Err = handleResult(SeqNo, TagAddr, std::move(ArgBytes)))
       return std::move(Err);
@@ -354,5 +356,19 @@ void SimpleRemoteEPC::handleCallWrapper(
       TagAddr.getValue(), ArgBytes);
 }
 
+Error SimpleRemoteEPC::handleHangup(SimpleRemoteEPCArgBytesVector ArgBytes) {
+  using namespace llvm::orc::shared;
+  auto WFR = WrapperFunctionResult::copyFrom(ArgBytes.data(), ArgBytes.size());
+  if (const char *ErrMsg = WFR.getOutOfBandError())
+    return make_error<StringError>(ErrMsg, inconvertibleErrorCode());
+
+  detail::SPSSerializableError Info;
+  SPSInputBuffer IB(WFR.data(), WFR.size());
+  if (!SPSArgList<SPSError>::deserialize(IB, Info))
+    return make_error<StringError>("Could not deserialize hangup info",
+                                   inconvertibleErrorCode());
+  return fromSPSSerializable(std::move(Info));
+}
+
 } // end namespace orc
 } // end namespace llvm