[ORC] Add a utility to support dumping JIT'd objects to disk for debugging.

Adds a DumpObjects utility that can be used to dump JIT'd objects to disk.
Instances of DebugObjects may be used by ObjectTransformLayer as no-op
transforms.

This patch also adds an ObjectTransformLayer to LLJIT and an example of how
to use this utility to dump JIT'd objects in LLJIT.

2 files changed, 82 insertions, 0 deletions

diff --git a/llvm/examples/LLJITExamples/LLJITDumpObjects/CMakeLists.txt b/llvm/examples/LLJITExamples/LLJITDumpObjects/CMakeLists.txt
new file mode 100644
index 00000000000..bf3bc7193ae
--- /dev/null
+++ b/llvm/examples/LLJITExamples/LLJITDumpObjects/CMakeLists.txt
@@ -0,0 +1,12 @@
+set(LLVM_LINK_COMPONENTS
+  Core
+  ExecutionEngine
+  IRReader
+  OrcJIT
+  Support
+  nativecodegen
+  )
+
+add_llvm_example(LLJITDumpObjects
+  LLJITDumpObjects.cpp
+  )
diff --git a/llvm/examples/LLJITExamples/LLJITDumpObjects/LLJITDumpObjects.cpp b/llvm/examples/LLJITExamples/LLJITDumpObjects/LLJITDumpObjects.cpp
new file mode 100644
index 00000000000..875292a2e09
--- /dev/null
+++ b/llvm/examples/LLJITExamples/LLJITDumpObjects/LLJITDumpObjects.cpp
@@ -0,0 +1,70 @@
+//===----- 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/StringMap.h"
+#include "llvm/ExecutionEngine/Orc/DebugUtils.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;
+
+cl::opt<bool> DumpJITdObjects("dump-jitted-objects",
+                              cl::desc("dump jitted objects"), cl::Optional,
+                              cl::init(true));
+
+cl::opt<std::string> DumpDir("dump-dir",
+                             cl::desc("directory to dump objects to"),
+                             cl::Optional, cl::init(""));
+
+cl::opt<std::string> DumpFileStem("dump-file-stem",
+                                  cl::desc("Override default dump names"),
+                                  cl::Optional, cl::init(""));
+
+int main(int argc, char *argv[]) {
+  // Initialize LLVM.
+  InitLLVM X(argc, argv);
+
+  InitializeNativeTarget();
+  InitializeNativeTargetAsmPrinter();
+
+  cl::ParseCommandLineOptions(argc, argv, "HowToUseLLJIT");
+  ExitOnErr.setBanner(std::string(argv[0]) + ": ");
+
+  outs()
+      << "Usage notes:\n"
+         "  Use -debug-only=orc on debug builds to see log messages of objects "
+         "being dumped\n"
+         "  Specify -dump-dir to specify a dump directory\n"
+         "  Specify -dump-file-stem to override the dump file stem\n"
+         "  Specify -dump-jitted-objects=false to disable dumping\n";
+
+  auto J = ExitOnErr(LLJITBuilder().create());
+
+  if (DumpJITdObjects)
+    J->getObjTransformLayer().setTransform(DumpObjects(DumpDir, DumpFileStem));
+
+  auto M = ExitOnErr(parseExampleModule(Add1Example, "add1"));
+
+  ExitOnErr(J->addIRModule(std::move(M)));
+
+  // Look up the JIT'd function, cast it to a function pointer, then call it.
+  auto Add1Sym = ExitOnErr(J->lookup("add1"));
+  int (*Add1)(int) = (int (*)(int))Add1Sym.getAddress();
+
+  int Result = Add1(42);
+  outs() << "add1(42) = " << Result << "\n";
+
+  return 0;
+}