[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.

5 files changed, 86 insertions, 12 deletions

diff --git a/llvm/lib/ExecutionEngine/Orc/CMakeLists.txt b/llvm/lib/ExecutionEngine/Orc/CMakeLists.txt
index e615fd8f234..4a18f884744 100644
--- a/llvm/lib/ExecutionEngine/Orc/CMakeLists.txt
+++ b/llvm/lib/ExecutionEngine/Orc/CMakeLists.txt
@@ -2,6 +2,7 @@ add_llvm_library(LLVMOrcJIT
   CompileOnDemandLayer.cpp
   CompileUtils.cpp
   Core.cpp
+  DebugUtils.cpp
   ExecutionUtils.cpp
   IndirectionUtils.cpp
   IRCompileLayer.cpp
diff --git a/llvm/lib/ExecutionEngine/Orc/CompileUtils.cpp b/llvm/lib/ExecutionEngine/Orc/CompileUtils.cpp
index f8251627a4e..f5671d90420 100644
--- a/llvm/lib/ExecutionEngine/Orc/CompileUtils.cpp
+++ b/llvm/lib/ExecutionEngine/Orc/CompileUtils.cpp
@@ -43,8 +43,7 @@ SimpleCompiler::CompileResult SimpleCompiler::operator()(Module &M) {
   }
 
   auto ObjBuffer = std::make_unique<SmallVectorMemoryBuffer>(
-      std::move(ObjBufferSV),
-      "<in memory object compiled from " + M.getModuleIdentifier() + ">");
+      std::move(ObjBufferSV), M.getModuleIdentifier() + "-jitted-objectbuffer");
 
   auto Obj = object::ObjectFile::createObjectFile(ObjBuffer->getMemBufferRef());
 
diff --git a/llvm/lib/ExecutionEngine/Orc/DebugUtils.cpp b/llvm/lib/ExecutionEngine/Orc/DebugUtils.cpp
new file mode 100644
index 00000000000..4e573dad118
--- /dev/null
+++ b/llvm/lib/ExecutionEngine/Orc/DebugUtils.cpp
@@ -0,0 +1,68 @@
+//===---------- DebugUtils.cpp - Utilities for debugging ORC JITs ---------===//
+//
+// 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/ExecutionEngine/Orc/DebugUtils.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/Path.h"
+#include "llvm/Support/raw_ostream.h"
+
+#define DEBUG_TYPE "orc"
+
+namespace llvm {
+namespace orc {
+
+DumpObjects::DumpObjects(std::string DumpDir, std::string IdentifierOverride)
+    : DumpDir(std::move(DumpDir)),
+      IdentifierOverride(std::move(IdentifierOverride)) {
+
+  /// Discard any trailing separators.
+  while (!this->DumpDir.empty() &&
+         sys::path::is_separator(this->DumpDir.back()))
+    this->DumpDir.pop_back();
+}
+
+Expected<std::unique_ptr<MemoryBuffer>>
+DumpObjects::operator()(std::unique_ptr<MemoryBuffer> Obj) {
+  size_t Idx = 1;
+
+  std::string DumpPathStem;
+  raw_string_ostream(DumpPathStem)
+      << DumpDir << (DumpDir.empty() ? "" : "/") << getBufferIdentifier(*Obj);
+
+  std::string DumpPath = DumpPathStem + ".o";
+  while (sys::fs::exists(DumpPath)) {
+    DumpPath.clear();
+    raw_string_ostream(DumpPath) << DumpPathStem << "." << (++Idx) << ".o";
+  }
+
+  LLVM_DEBUG({
+    dbgs() << "Dumping object buffer [ " << (void *)Obj->getBufferStart()
+           << " -- " << (void *)(Obj->getBufferEnd() - 1) << " ] to "
+           << DumpPath << "\n";
+  });
+
+  std::error_code EC;
+  raw_fd_ostream DumpStream(DumpPath, EC);
+  if (EC)
+    return errorCodeToError(EC);
+  DumpStream.write(Obj->getBufferStart(), Obj->getBufferSize());
+
+  return Obj;
+}
+
+StringRef DumpObjects::getBufferIdentifier(MemoryBuffer &B) {
+  if (!IdentifierOverride.empty())
+    return IdentifierOverride;
+  StringRef Identifier = B.getBufferIdentifier();
+  Identifier.consume_back(".o");
+  return Identifier;
+}
+
+} // End namespace orc.
+} // End namespace llvm.
diff --git a/llvm/lib/ExecutionEngine/Orc/LLJIT.cpp b/llvm/lib/ExecutionEngine/Orc/LLJIT.cpp
index a80f78afe80..03f22e0c2a2 100644
--- a/llvm/lib/ExecutionEngine/Orc/LLJIT.cpp
+++ b/llvm/lib/ExecutionEngine/Orc/LLJIT.cpp
@@ -51,7 +51,7 @@ Error LLJIT::addIRModule(JITDylib &JD, ThreadSafeModule TSM) {
 Error LLJIT::addObjectFile(JITDylib &JD, std::unique_ptr<MemoryBuffer> Obj) {
   assert(Obj && "Can not add null object");
 
-  return ObjLinkingLayer->add(JD, std::move(Obj), ES->allocateVModule());
+  return ObjTransformLayer.add(JD, std::move(Obj), ES->allocateVModule());
 }
 
 Expected<JITEvaluatedSymbol> LLJIT::lookupLinkerMangled(JITDylib &JD,
@@ -103,13 +103,13 @@ LLJIT::createCompileFunction(LLJITBuilderState &S,
 
 LLJIT::LLJIT(LLJITBuilderState &S, Error &Err)
     : ES(S.ES ? std::move(S.ES) : std::make_unique<ExecutionSession>()),
-      Main(this->ES->getMainJITDylib()), DL(""), CtorRunner(Main),
+      Main(this->ES->getMainJITDylib()), DL(""),
+      ObjLinkingLayer(createObjectLinkingLayer(S, *ES)),
+      ObjTransformLayer(*this->ES, *ObjLinkingLayer), CtorRunner(Main),
       DtorRunner(Main) {
 
   ErrorAsOutParameter _(&Err);
 
-  ObjLinkingLayer = createObjectLinkingLayer(S, *ES);
-
   if (auto DLOrErr = S.JTMB->getDefaultDataLayoutForTarget())
     DL = std::move(*DLOrErr);
   else {
@@ -124,7 +124,7 @@ LLJIT::LLJIT(LLJITBuilderState &S, Error &Err)
       return;
     }
     CompileLayer = std::make_unique<IRCompileLayer>(
-        *ES, *ObjLinkingLayer, std::move(*CompileFunction));
+        *ES, ObjTransformLayer, std::move(*CompileFunction));
   }
 
   if (S.NumCompileThreads > 0) {
diff --git a/llvm/lib/ExecutionEngine/Orc/ObjectTransformLayer.cpp b/llvm/lib/ExecutionEngine/Orc/ObjectTransformLayer.cpp
index 815517321b7..d18eb38a414 100644
--- a/llvm/lib/ExecutionEngine/Orc/ObjectTransformLayer.cpp
+++ b/llvm/lib/ExecutionEngine/Orc/ObjectTransformLayer.cpp
@@ -21,12 +21,18 @@ void ObjectTransformLayer::emit(MaterializationResponsibility R,
                                 std::unique_ptr<MemoryBuffer> O) {
   assert(O && "Module must not be null");
 
-  if (auto TransformedObj = Transform(std::move(O)))
-    BaseLayer.emit(std::move(R), std::move(*TransformedObj));
-  else {
-    R.failMaterialization();
-    getExecutionSession().reportError(TransformedObj.takeError());
+  // If there is a transform set then apply it.
+  if (Transform) {
+    if (auto TransformedObj = Transform(std::move(O)))
+      O = std::move(*TransformedObj);
+    else {
+      R.failMaterialization();
+      getExecutionSession().reportError(TransformedObj.takeError());
+      return;
+    }
   }
+
+  BaseLayer.emit(std::move(R), std::move(O));
 }
 
 } // End namespace orc.