[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, 15 insertions, 12 deletions

diff --git a/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.h b/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.h
index 4aeab819179..f9c1d4db30b 100644
--- a/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.h
+++ b/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.h
@@ -28,9 +28,11 @@ std::error_code Check(std::error_code Err) {
   }
   return Err;
 }
+
 } // end anonymous namespace
 
 class RuntimeDyldELF : public RuntimeDyldImpl {
+
   void resolveRelocation(const SectionEntry &Section, uint64_t Offset,
                          uint64_t Value, uint32_t Type, int64_t Addend,
                          uint64_t SymOffset = 0);
@@ -81,9 +83,11 @@ class RuntimeDyldELF : public RuntimeDyldImpl {
       return 1;
   }
 
-  void findPPC64TOCSection(ObjectImage &Obj, ObjSectionToIDMap &LocalSections,
+  void findPPC64TOCSection(const ObjectFile &Obj,
+                           ObjSectionToIDMap &LocalSections,
                            RelocationValueRef &Rel);
-  void findOPDEntrySection(ObjectImage &Obj, ObjSectionToIDMap &LocalSections,
+  void findOPDEntrySection(const ObjectFile &Obj,
+                           ObjSectionToIDMap &LocalSections,
                            RelocationValueRef &Rel);
 
   uint64_t findGOTEntry(uint64_t LoadAddr, uint64_t Offset);
@@ -104,24 +108,23 @@ class RuntimeDyldELF : public RuntimeDyldImpl {
   SmallVector<SID, 2> RegisteredEHFrameSections;
 
 public:
-  RuntimeDyldELF(RTDyldMemoryManager *mm) : RuntimeDyldImpl(mm) {}
+  RuntimeDyldELF(RTDyldMemoryManager *mm);
+  virtual ~RuntimeDyldELF();
+
+  std::unique_ptr<RuntimeDyld::LoadedObjectInfo>
+  loadObject(const object::ObjectFile &O) override;
 
   void resolveRelocation(const RelocationEntry &RE, uint64_t Value) override;
   relocation_iterator
   processRelocationRef(unsigned SectionID, relocation_iterator RelI,
-                       ObjectImage &Obj, ObjSectionToIDMap &ObjSectionToID,
+                       const ObjectFile &Obj,
+                       ObjSectionToIDMap &ObjSectionToID,
                        const SymbolTableMap &Symbols, StubMap &Stubs) override;
-  bool isCompatibleFormat(const ObjectBuffer *Buffer) const override;
-  bool isCompatibleFile(const object::ObjectFile *Buffer) const override;
+  bool isCompatibleFile(const object::ObjectFile &Obj) const override;
   void registerEHFrames() override;
   void deregisterEHFrames() override;
-  void finalizeLoad(ObjectImage &ObjImg,
+  void finalizeLoad(const ObjectFile &Obj,
                     ObjSectionToIDMap &SectionMap) override;
-  virtual ~RuntimeDyldELF();
-
-  static std::unique_ptr<ObjectImage>
-  createObjectImage(std::unique_ptr<ObjectBuffer> InputBuffer);
-  static ObjectImage *createObjectImageFromFile(std::unique_ptr<object::ObjectFile> Obj);
 };
 
 } // end namespace llvm