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

…cheme.

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 .



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@222810 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/ExecutionEngine/JITEventListener.h

@@ -15,6 +15,7 @@
 #ifndef LLVM_EXECUTIONENGINE_JITEVENTLISTENER_H
 #define LLVM_EXECUTIONENGINE_JITEVENTLISTENER_H
 
+#include "RuntimeDyld.h"
 #include "llvm/Config/llvm-config.h"
 #include "llvm/IR/DebugLoc.h"
 #include "llvm/Support/DataTypes.h"
@@ -25,7 +26,10 @@ class Function;
 class MachineFunction;
 class OProfileWrapper;
 class IntelJITEventsWrapper;
-class ObjectImage;
+
+namespace object {
+  class ObjectFile;
+}
 
 /// JITEvent_EmittedFunctionDetails - Helper struct for containing information
 /// about a generated machine code function.
@@ -57,7 +61,7 @@ class JITEventListener {
 
 public:
   JITEventListener() {}
-  virtual ~JITEventListener();
+  virtual ~JITEventListener() {}
 
   /// NotifyObjectEmitted - Called after an object has been successfully
   /// emitted to memory.  NotifyFunctionEmitted will not be called for
@@ -67,11 +71,15 @@ class JITEventListener {
   /// The ObjectImage contains the generated object image
   /// with section headers updated to reflect the address at which sections
   /// were loaded and with relocations performed in-place on debug sections.
-  virtual void NotifyObjectEmitted(const ObjectImage &Obj) {}
+  virtual void NotifyObjectEmitted(const object::ObjectFile &Obj,
+                                   const RuntimeDyld::LoadedObjectInfo &L) {}
 
   /// NotifyFreeingObject - Called just before the memory associated with
   /// a previously emitted object is released.
-  virtual void NotifyFreeingObject(const ObjectImage &Obj) {}
+  virtual void NotifyFreeingObject(const object::ObjectFile &Obj) {}
+
+  // Get a pointe to the GDB debugger registration listener.
+  static JITEventListener *createGDBRegistrationListener();
 
 #if LLVM_USE_INTEL_JITEVENTS
   // Construct an IntelJITEventListener
@@ -105,7 +113,8 @@ class JITEventListener {
     return nullptr;
   }
 #endif // USE_OPROFILE
-
+private:
+  virtual void anchor();
 };
 
 } // end namespace llvm.

include/llvm/ExecutionEngine/RTDyldMemoryManager.h

@@ -22,7 +22,10 @@
 namespace llvm {
 
 class ExecutionEngine;
-class ObjectImage;
+
+  namespace object {
+    class ObjectFile;
+  }
 
 // RuntimeDyld clients often want to handle the memory management of
 // what gets placed where. For JIT clients, this is the subset of
@@ -109,7 +112,7 @@ class RTDyldMemoryManager {
   /// address space can use this call to remap the section addresses for the
   /// newly loaded object.
   virtual void notifyObjectLoaded(ExecutionEngine *EE,
-                                  const ObjectImage *) {}
+                                  const object::ObjectFile &) {}
 
   /// This method is called when object loading is complete and section page
   /// permissions can be applied.  It is up to the memory manager implementation

include/llvm/ExecutionEngine/RuntimeDyld.h

@@ -15,19 +15,19 @@
 #define LLVM_EXECUTIONENGINE_RUNTIMEDYLD_H
 
 #include "llvm/ADT/StringRef.h"
-#include "llvm/ExecutionEngine/ObjectBuffer.h"
 #include "llvm/ExecutionEngine/RTDyldMemoryManager.h"
 #include "llvm/Support/Memory.h"
+#include <memory>
 
 namespace llvm {
 
 namespace object {
   class ObjectFile;
+  template <typename T> class OwningBinary;
 }
 
 class RuntimeDyldImpl;
 class RuntimeDyldCheckerImpl;
-class ObjectImage;
 
 class RuntimeDyld {
   friend class RuntimeDyldCheckerImpl;
@@ -46,22 +46,35 @@ class RuntimeDyld {
   // Any relocations already associated with the symbol will be re-resolved.
   void reassignSectionAddress(unsigned SectionID, uint64_t Addr);
 public:
+
+  /// \brief Information about the loaded object.
+  class LoadedObjectInfo {
+    friend class RuntimeDyldImpl;
+  public:
+    LoadedObjectInfo(RuntimeDyldImpl &RTDyld, unsigned BeginIdx,
+                     unsigned EndIdx)
+      : RTDyld(RTDyld), BeginIdx(BeginIdx), EndIdx(EndIdx) { }
+
+    virtual ~LoadedObjectInfo() {}
+
+    virtual object::OwningBinary<object::ObjectFile>
+    getObjectForDebug(const object::ObjectFile &Obj) const = 0;
+
+    uint64_t getSectionLoadAddress(StringRef Name) const;
+
+  protected:
+    virtual void anchor();
+
+    RuntimeDyldImpl &RTDyld;
+    unsigned BeginIdx, EndIdx;
+  };
+
   RuntimeDyld(RTDyldMemoryManager *);
   ~RuntimeDyld();
 
-  /// Prepare the object contained in the input buffer for execution.
-  /// Ownership of the input buffer is transferred to the ObjectImage
-  /// instance returned from this function if successful. In the case of load
-  /// failure, the input buffer will be deleted.
-  std::unique_ptr<ObjectImage>
-  loadObject(std::unique_ptr<ObjectBuffer> InputBuffer);
-
-  /// Prepare the referenced object file for execution.
-  /// Ownership of the input object is transferred to the ObjectImage
-  /// instance returned from this function if successful. In the case of load
-  /// failure, the input object will be deleted.
-  std::unique_ptr<ObjectImage>
-  loadObject(std::unique_ptr<object::ObjectFile> InputObject);
+  /// Add the referenced object file to the list of objects to be loaded and
+  /// relocated.
+  std::unique_ptr<LoadedObjectInfo> loadObject(const object::ObjectFile &O);
 
   /// Get the address of our local copy of the symbol. This may or may not
   /// be the address used for relocation (clients can copy the data around

lib/ExecutionEngine/CMakeLists.txt

@@ -3,7 +3,6 @@
 add_llvm_library(LLVMExecutionEngine
   ExecutionEngine.cpp
   ExecutionEngineBindings.cpp
-  JITEventListener.cpp
   RTDyldMemoryManager.cpp
   TargetSelect.cpp
   )

lib/ExecutionEngine/ExecutionEngine.cpp

@@ -16,8 +16,7 @@
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/ExecutionEngine/GenericValue.h"
-#include "llvm/ExecutionEngine/ObjectBuffer.h"
-#include "llvm/ExecutionEngine/ObjectCache.h"
+#include "llvm/ExecutionEngine/JITEventListener.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DataLayout.h"
 #include "llvm/IR/DerivedTypes.h"
@@ -43,17 +42,15 @@ using namespace llvm;
 STATISTIC(NumInitBytes, "Number of bytes of global vars initialized");
 STATISTIC(NumGlobals  , "Number of global vars initialized");
 
-// Pin the vtable to this file.
-void ObjectCache::anchor() {}
-void ObjectBuffer::anchor() {}
-void ObjectBufferStream::anchor() {}
-
 ExecutionEngine *(*ExecutionEngine::MCJITCtor)(
     std::unique_ptr<Module> M, std::string *ErrorStr,
     RTDyldMemoryManager *MCJMM, std::unique_ptr<TargetMachine> TM) = nullptr;
 ExecutionEngine *(*ExecutionEngine::InterpCtor)(std::unique_ptr<Module> M,
                                                 std::string *ErrorStr) =nullptr;
 
+// Anchor for the JITEventListener class.
+void JITEventListener::anchor() {}
+
 ExecutionEngine::ExecutionEngine(std::unique_ptr<Module> M)
   : EEState(*this),
     LazyFunctionCreator(nullptr) {