[MCJIT] Clean up RuntimeDyld's quirky object-ownership/modification scheme.

Previously, when loading an object file, RuntimeDyld (1) took ownership of the
ObjectFile instance (and associated MemoryBuffer), (2) potentially modified the
object in-place, and (3) returned an ObjectImage that managed ownership of the
now-modified object and provided some convenience methods. This scheme accreted
over several years as features were tacked on to RuntimeDyld, and was both
unintuitive and unsafe (See e.g. http://llvm.org/PR20722).

This patch fixes the issue by removing all ownership and in-place modification
of object files from RuntimeDyld. Existing behavior, including debugger
registration, is preserved.

Noteworthy changes include:

(1) ObjectFile instances are now passed to RuntimeDyld by const-ref.
(2) The ObjectImage and ObjectBuffer classes have been removed entirely, they
    existed to model ownership within RuntimeDyld, and so are no longer needed.
(3) RuntimeDyld::loadObject now returns an instance of a new class,
    RuntimeDyld::LoadedObjectInfo, which can be used to construct a modified
    object suitable for registration with the debugger, following the existing
    debugger registration scheme.
(4) The JITRegistrar class has been removed, and the GDBRegistrar class has been
    re-written as a JITEventListener.

This should fix http://llvm.org/PR20722 .

llvm-svn: 222810

1 files changed, 38 insertions, 33 deletions

diff --git a/llvm/lib/ExecutionEngine/MCJIT/MCJIT.cpp b/llvm/lib/ExecutionEngine/MCJIT/MCJIT.cpp
index da5f03799e3..58cf4e5e6dd 100644
--- a/llvm/lib/ExecutionEngine/MCJIT/MCJIT.cpp
+++ b/llvm/lib/ExecutionEngine/MCJIT/MCJIT.cpp
@@ -11,8 +11,6 @@
 #include "llvm/ExecutionEngine/GenericValue.h"
 #include "llvm/ExecutionEngine/JITEventListener.h"
 #include "llvm/ExecutionEngine/MCJIT.h"
-#include "llvm/ExecutionEngine/ObjectBuffer.h"
-#include "llvm/ExecutionEngine/ObjectImage.h"
 #include "llvm/ExecutionEngine/SectionMemoryManager.h"
 #include "llvm/IR/DataLayout.h"
 #include "llvm/IR/DerivedTypes.h"
@@ -21,6 +19,7 @@
 #include "llvm/IR/Module.h"
 #include "llvm/MC/MCAsmInfo.h"
 #include "llvm/Object/Archive.h"
+#include "llvm/Object/ObjectFile.h"
 #include "llvm/PassManager.h"
 #include "llvm/Support/DynamicLibrary.h"
 #include "llvm/Support/ErrorHandling.h"
@@ -31,6 +30,8 @@
 
 using namespace llvm;
 
+void ObjectCache::anchor() {}
+
 namespace {
 
 static struct RegisterJIT {
@@ -74,6 +75,7 @@ MCJIT::MCJIT(std::unique_ptr<Module> M, std::unique_ptr<TargetMachine> tm,
 
   OwnedModules.addModule(std::move(First));
   setDataLayout(TM->getSubtargetImpl()->getDataLayout());
+  RegisterJITEventListener(JITEventListener::createGDBRegistrationListener());
 }
 
 MCJIT::~MCJIT() {
@@ -99,13 +101,13 @@ bool MCJIT::removeModule(Module *M) {
 }
 
 void MCJIT::addObjectFile(std::unique_ptr<object::ObjectFile> Obj) {
-  std::unique_ptr<ObjectImage> LoadedObject = Dyld.loadObject(std::move(Obj));
-  if (!LoadedObject || Dyld.hasError())
+  std::unique_ptr<RuntimeDyld::LoadedObjectInfo> L = Dyld.loadObject(*Obj);
+  if (Dyld.hasError())
     report_fatal_error(Dyld.getErrorString());
 
-  NotifyObjectEmitted(*LoadedObject);
+  NotifyObjectEmitted(*Obj, *L);
 
-  LoadedObjects.push_back(std::move(LoadedObject));
+  LoadedObjects.push_back(std::move(Obj));
 }
 
 void MCJIT::addObjectFile(object::OwningBinary<object::ObjectFile> Obj) {
@@ -125,7 +127,7 @@ void MCJIT::setObjectCache(ObjectCache* NewCache) {
   ObjCache = NewCache;
 }
 
-std::unique_ptr<ObjectBufferStream> MCJIT::emitObject(Module *M) {
+std::unique_ptr<MemoryBuffer> MCJIT::emitObject(Module *M) {
   MutexGuard locked(lock);
 
   // This must be a module which has already been added but not loaded to this
@@ -138,30 +140,32 @@ std::unique_ptr<ObjectBufferStream> MCJIT::emitObject(Module *M) {
   PM.add(new DataLayoutPass());
 
   // The RuntimeDyld will take ownership of this shortly
-  std::unique_ptr<ObjectBufferStream> CompiledObject(new ObjectBufferStream());
+  SmallVector<char, 4096> ObjBufferSV;
+  raw_svector_ostream ObjStream(ObjBufferSV);
 
   // Turn the machine code intermediate representation into bytes in memory
   // that may be executed.
-  if (TM->addPassesToEmitMC(PM, Ctx, CompiledObject->getOStream(),
-                            !getVerifyModules())) {
+  if (TM->addPassesToEmitMC(PM, Ctx, ObjStream, !getVerifyModules()))
     report_fatal_error("Target does not support MC emission!");
-  }
 
   // Initialize passes.
   PM.run(*M);
   // Flush the output buffer to get the generated code into memory
-  CompiledObject->flush();
+  ObjStream.flush();
+
+  std::unique_ptr<MemoryBuffer> CompiledObjBuffer(
+                                new ObjectMemoryBuffer(std::move(ObjBufferSV)));
 
   // If we have an object cache, tell it about the new object.
   // Note that we're using the compiled image, not the loaded image (as below).
   if (ObjCache) {
     // MemoryBuffer is a thin wrapper around the actual memory, so it's OK
     // to create a temporary object here and delete it after the call.
-    MemoryBufferRef MB = CompiledObject->getMemBuffer();
+    MemoryBufferRef MB = CompiledObjBuffer->getMemBufferRef();
     ObjCache->notifyObjectCompiled(M, MB);
   }
 
-  return CompiledObject;
+  return CompiledObjBuffer;
 }
 
 void MCJIT::generateCodeForModule(Module *M) {
@@ -176,14 +180,10 @@ void MCJIT::generateCodeForModule(Module *M) {
   if (OwnedModules.hasModuleBeenLoaded(M))
     return;
 
-  std::unique_ptr<ObjectBuffer> ObjectToLoad;
+  std::unique_ptr<MemoryBuffer> ObjectToLoad;
   // Try to load the pre-compiled object from cache if possible
-  if (ObjCache) {
-    if (std::unique_ptr<MemoryBuffer> PreCompiledObject =
-            ObjCache->getObject(M))
-      ObjectToLoad =
-          llvm::make_unique<ObjectBuffer>(std::move(PreCompiledObject));
-  }
+  if (ObjCache)
+    ObjectToLoad = ObjCache->getObject(M);
 
   // If the cache did not contain a suitable object, compile the object
   if (!ObjectToLoad) {
@@ -193,17 +193,18 @@ void MCJIT::generateCodeForModule(Module *M) {
 
   // Load the object into the dynamic linker.
   // MCJIT now owns the ObjectImage pointer (via its LoadedObjects list).
-  std::unique_ptr<ObjectImage> LoadedObject =
-      Dyld.loadObject(std::move(ObjectToLoad));
-  if (!LoadedObject)
-    report_fatal_error(Dyld.getErrorString());
+  ErrorOr<std::unique_ptr<object::ObjectFile>> LoadedObject =
+    object::ObjectFile::createObjectFile(ObjectToLoad->getMemBufferRef());
+  std::unique_ptr<RuntimeDyld::LoadedObjectInfo> L =
+    Dyld.loadObject(*LoadedObject.get());
 
-  // FIXME: Make this optional, maybe even move it to a JIT event listener
-  LoadedObject->registerWithDebugger();
+  if (Dyld.hasError())
+    report_fatal_error(Dyld.getErrorString());
 
-  NotifyObjectEmitted(*LoadedObject);
+  NotifyObjectEmitted(*LoadedObject.get(), *L);
 
-  LoadedObjects.push_back(std::move(LoadedObject));
+  Buffers.push_back(std::move(ObjectToLoad));
+  LoadedObjects.push_back(std::move(*LoadedObject));
 
   OwnedModules.markModuleAsLoaded(M);
 }
@@ -549,6 +550,7 @@ void MCJIT::RegisterJITEventListener(JITEventListener *L) {
   MutexGuard locked(lock);
   EventListeners.push_back(L);
 }
+
 void MCJIT::UnregisterJITEventListener(JITEventListener *L) {
   if (!L)
     return;
@@ -559,14 +561,17 @@ void MCJIT::UnregisterJITEventListener(JITEventListener *L) {
     EventListeners.pop_back();
   }
 }
-void MCJIT::NotifyObjectEmitted(const ObjectImage& Obj) {
+
+void MCJIT::NotifyObjectEmitted(const object::ObjectFile& Obj,
+                                const RuntimeDyld::LoadedObjectInfo &L) {
   MutexGuard locked(lock);
-  MemMgr.notifyObjectLoaded(this, &Obj);
+  MemMgr.notifyObjectLoaded(this, Obj);
   for (unsigned I = 0, S = EventListeners.size(); I < S; ++I) {
-    EventListeners[I]->NotifyObjectEmitted(Obj);
+    EventListeners[I]->NotifyObjectEmitted(Obj, L);
   }
 }
-void MCJIT::NotifyFreeingObject(const ObjectImage& Obj) {
+
+void MCJIT::NotifyFreeingObject(const object::ObjectFile& Obj) {
   MutexGuard locked(lock);
   for (JITEventListener *L : EventListeners)
     L->NotifyFreeingObject(Obj);