[ORC] Add example showing how to initialize/deinitialize a JITDylib with LLJIT.

examples/OrcV2Examples/CMakeLists.txt

@@ -1,6 +1,7 @@
 add_subdirectory(LLJITDumpObjects)
 add_subdirectory(LLJITWithCustomObjectLinkingLayer)
 add_subdirectory(LLJITWithGDBRegistrationListener)
+add_subdirectory(LLJITWithInitializers)
 add_subdirectory(LLJITWithLazyReexports)
 add_subdirectory(LLJITWithObjectCache)
 add_subdirectory(LLJITWithObjectLinkingLayerPlugin)

examples/OrcV2Examples/LLJITWithInitializers/CMakeLists.txt

@@ -0,0 +1,13 @@
+set(LLVM_LINK_COMPONENTS
+  Core
+  ExecutionEngine
+  IRReader
+  JITLink
+  OrcJIT
+  Support
+  nativecodegen
+  )
+
+add_llvm_example(LLJITWithInitializers
+  LLJITWithInitializers.cpp
+  )

examples/OrcV2Examples/LLJITWithInitializers/LLJITWithInitializers.cpp

@@ -0,0 +1,97 @@
+//===----- LLJITDumpObjects.cpp - How to dump JIT'd objects with LLJIT ----===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+///
+/// This example demonstrates how to use LLJIT to:
+///   - Add absolute symbol definitions.
+///   - Run static constructors for a JITDylib.
+///   - Run static destructors for a JITDylib.
+///
+/// This example does not call any functions (e.g. main or equivalent)  between
+/// running the static constructors and running the static destructors.
+///
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/StringMap.h"
+#include "llvm/ExecutionEngine/Orc/LLJIT.h"
+#include "llvm/Support/InitLLVM.h"
+#include "llvm/Support/TargetSelect.h"
+#include "llvm/Support/raw_ostream.h"
+
+#include "../ExampleModules.h"
+
+using namespace llvm;
+using namespace llvm::orc;
+
+ExitOnError ExitOnErr;
+
+const llvm::StringRef ModuleWithInitializer =
+    R"(
+
+  @InitializersRunFlag = external global i32
+  @DeinitializersRunFlag = external global i32
+
+  declare i32 @__cxa_atexit(void (i8*)*, i8*, i8*)
+  @__dso_handle = external hidden global i8
+
+  @llvm.global_ctors =
+    appending global [1 x { i32, void ()*, i8* }]
+      [{ i32, void ()*, i8* } { i32 65535, void ()* @init_func, i8* null }]
+
+  define internal void @init_func() {
+  entry:
+    store i32 1, i32* @InitializersRunFlag
+    %0 = call i32 @__cxa_atexit(void (i8*)* @deinit_func, i8* null,
+                                i8* @__dso_handle)
+    ret void
+  }
+
+  define internal void @deinit_func(i8* %0) {
+    store i32 1, i32* @DeinitializersRunFlag
+    ret void
+  }
+
+)";
+
+int main(int argc, char *argv[]) {
+  // Initialize LLVM.
+  InitLLVM X(argc, argv);
+
+  InitializeNativeTarget();
+  InitializeNativeTargetAsmPrinter();
+
+  cl::ParseCommandLineOptions(argc, argv, "LLJITWithInitializers");
+  ExitOnErr.setBanner(std::string(argv[0]) + ": ");
+
+  auto J = ExitOnErr(LLJITBuilder().create());
+  auto M = ExitOnErr(parseExampleModule(ModuleWithInitializer, "M"));
+
+  // Load the module.
+  ExitOnErr(J->addIRModule(std::move(M)));
+
+  int32_t InitializersRunFlag = 0;
+  int32_t DeinitializersRunFlag = 0;
+
+  ExitOnErr(J->define(absoluteSymbols(
+      {{J->mangleAndIntern("InitializersRunFlag"),
+        JITEvaluatedSymbol::fromPointer(&InitializersRunFlag)},
+       {J->mangleAndIntern("DeinitializersRunFlag"),
+        JITEvaluatedSymbol::fromPointer(&DeinitializersRunFlag)}})));
+
+  // Run static initializers.
+  ExitOnErr(J->initialize(J->getMainJITDylib()));
+
+  // Run deinitializers.
+  ExitOnErr(J->deinitialize(J->getMainJITDylib()));
+
+  outs() << "InitializerRanFlag = " << InitializersRunFlag << "\n"
+         << "DeinitializersRunFlag = " << DeinitializersRunFlag << "\n";
+
+  return 0;
+}