Add catalyst executor server side to catalyst

doc/releases/changelog-dev.md

@@ -77,6 +77,10 @@
     [(#3031)](https://github.com/PennyLaneAI/catalyst/pull/3031)
     [(#3030)](https://github.com/PennyLaneAI/catalyst/pull/3030)
 
+  - The `catalyst-executor` server side is now added to Catalyst that receives objects, maps them
+    and calls them.
+    [(#3088)](https://github.com/PennyLaneAI/catalyst/pull/3088)
+
 * A `BufferizableOpInterface` implementation is now added for `catalyst.launch_kernel` operation and it is now bufferizable.
   [(#3024)](https://github.com/PennyLaneAI/catalyst/pull/3024)
 

runtime/Makefile

@@ -61,7 +61,7 @@ ifeq ($(ENABLE_TRANSPORT), ON)
 endif
 
 ifeq ($(ENABLE_EXECUTOR), ON)
-	BUILD_TARGETS += rt_executor
+	BUILD_TARGETS += rt_executor catalyst-executor
 endif
 
 .PHONY: help

runtime/lib/executor/CMakeLists.txt

@@ -1,5 +1,8 @@
 ###############################################
-# library catalyst_executor_session + rt_executor #
+# catalyst_executor_session + rt_executor + catalyst-executor
+#   HOST  rt_executor                 the C ABI a compiled program calls, over handles
+#         catalyst_executor_session   the ORC client it drives
+#   NODE  catalyst-executor           the ORC server: receives objects, maps them, calls them
 ###############################################
 
 find_package(LLVM CONFIG REQUIRED)
@@ -61,3 +64,30 @@ if(NOT APPLE)
 else()
     set_property(TARGET rt_executor APPEND PROPERTY BUILD_RPATH @loader_path)
 endif()
+
+# catalyst-executor
+
+llvm_map_components_to_libnames(_executor_bin_llvm_libs
+    orcjit orctargetprocess orcshared support
+)
+
+add_executable(catalyst-executor executor.cpp)
+
+target_include_directories(catalyst-executor SYSTEM PRIVATE ${LLVM_INCLUDE_DIRS})
+
+target_link_libraries(catalyst-executor PRIVATE
+    ${_executor_bin_llvm_libs}
+    pthread
+    ${CMAKE_DL_LIBS}
+)
+
+target_compile_options(catalyst-executor PRIVATE -fno-rtti)
+
+if(APPLE)
+    target_link_options(catalyst-executor PRIVATE -Wl,-export_dynamic)
+else()
+    target_link_options(catalyst-executor PRIVATE -Wl,--export-dynamic)
+endif()
+
+set_target_properties(catalyst-executor PROPERTIES
+    RUNTIME_OUTPUT_DIRECTORY ${CMAKE_LIBRARY_OUTPUT_DIRECTORY})

runtime/lib/executor/ExecutorSession.cpp

@@ -247,6 +247,11 @@ Expected<std::unique_ptr<MemoryBuffer>> getFile(const Twine &filename)
     return createFileError(filename, F.getError());
 }
 
+void discardEPC(Expected<std::unique_ptr<SimpleRemoteEPC>> &EPC)
+{
+    consumeError(EPC ? (*EPC)->disconnect() : EPC.takeError());
+}
+
 } // namespace
 
 namespace catalyst::executor {
@@ -346,10 +351,7 @@ struct ExecutorSession {
         }
 
         if (timedOut) {
-            // Consume any error the forced socket shutdown produced before reporting the timeout.
-            if (!EPC) {
-                consumeError(EPC.takeError());
-            }
+            discardEPC(EPC);
             return createTCPSocketError("handshake with catalyst-executor timed out after " +
                                         Twine(timeoutSecs) +
                                         "s (is a catalyst-executor actually listening there?). "
@@ -362,7 +364,13 @@ struct ExecutorSession {
         JITTargetMachineBuilder JTMB((*EPC)->getTargetTriple());
         auto DL = JTMB.getDefaultDataLayoutForTarget();
         if (!DL) {
-            return DL.takeError();
+            discardEPC(EPC);
+            return joinErrors(
+                createStringError(llvm::inconvertibleErrorCode(),
+                                  "no data layout for the catalyst-executor's target triple '" +
+                                      (*EPC)->getTargetTriple().str() +
+                                      "'; this runtime may lack the LLVM backend for it"),
+                DL.takeError());
         }
 
         auto ES = std::make_unique<ExecutionSession>(std::move(*EPC));