[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, 18 deletions

diff --git a/llvm/tools/llvm-rtdyld/llvm-rtdyld.cpp b/llvm/tools/llvm-rtdyld/llvm-rtdyld.cpp
index 87d381e994f..c38e42307dd 100644
--- a/llvm/tools/llvm-rtdyld/llvm-rtdyld.cpp
+++ b/llvm/tools/llvm-rtdyld/llvm-rtdyld.cpp
@@ -13,8 +13,6 @@
 
 #include "llvm/ADT/StringMap.h"
 #include "llvm/DebugInfo/DIContext.h"
-#include "llvm/ExecutionEngine/ObjectBuffer.h"
-#include "llvm/ExecutionEngine/ObjectImage.h"
 #include "llvm/ExecutionEngine/RuntimeDyld.h"
 #include "llvm/ExecutionEngine/RuntimeDyldChecker.h"
 #include "llvm/MC/MCAsmInfo.h"
@@ -207,23 +205,32 @@ static int printLineInfoForInput() {
     if (std::error_code EC = InputBuffer.getError())
       return Error("unable to read input: '" + EC.message() + "'");
 
-    std::unique_ptr<ObjectImage> LoadedObject;
+    ErrorOr<std::unique_ptr<ObjectFile>> MaybeObj(
+      ObjectFile::createObjectFile((*InputBuffer)->getMemBufferRef()));
+
+    if (std::error_code EC = MaybeObj.getError())
+      return Error("unable to create object file: '" + EC.message() + "'");
+
+    ObjectFile &Obj = **MaybeObj;
+
     // Load the object file
-    LoadedObject = Dyld.loadObject(
-        llvm::make_unique<ObjectBuffer>(std::move(*InputBuffer)));
-    if (!LoadedObject) {
+    std::unique_ptr<RuntimeDyld::LoadedObjectInfo> LoadedObjInfo =
+      Dyld.loadObject(Obj);
+
+    if (Dyld.hasError())
       return Error(Dyld.getErrorString());
-    }
 
     // Resolve all the relocations we can.
     Dyld.resolveRelocations();
 
+    OwningBinary<ObjectFile> DebugObj = LoadedObjInfo->getObjectForDebug(Obj);
+
     std::unique_ptr<DIContext> Context(
-        DIContext::getDWARFContext(*LoadedObject->getObjectFile()));
+      DIContext::getDWARFContext(*DebugObj.getBinary()));
 
     // Use symbol info to iterate functions in the object.
-    for (object::symbol_iterator I = LoadedObject->begin_symbols(),
-                                 E = LoadedObject->end_symbols();
+    for (object::symbol_iterator I = DebugObj.getBinary()->symbol_begin(),
+                                 E = DebugObj.getBinary()->symbol_end();
          I != E; ++I) {
       object::SymbolRef::Type SymType;
       if (I->getType(SymType)) continue;
@@ -268,11 +275,17 @@ static int executeInput() {
         MemoryBuffer::getFileOrSTDIN(InputFileList[i]);
     if (std::error_code EC = InputBuffer.getError())
       return Error("unable to read input: '" + EC.message() + "'");
-    std::unique_ptr<ObjectImage> LoadedObject;
+    ErrorOr<std::unique_ptr<ObjectFile>> MaybeObj(
+      ObjectFile::createObjectFile((*InputBuffer)->getMemBufferRef()));
+
+    if (std::error_code EC = MaybeObj.getError())
+      return Error("unable to create object file: '" + EC.message() + "'");
+
+    ObjectFile &Obj = **MaybeObj;
+
     // Load the object file
-    LoadedObject = Dyld.loadObject(
-        llvm::make_unique<ObjectBuffer>(std::move(*InputBuffer)));
-    if (!LoadedObject) {
+    Dyld.loadObject(Obj);
+    if (Dyld.hasError()) {
       return Error(Dyld.getErrorString());
     }
   }
@@ -512,14 +525,21 @@ static int linkAndVerify() {
     // Load the input memory buffer.
     ErrorOr<std::unique_ptr<MemoryBuffer>> InputBuffer =
         MemoryBuffer::getFileOrSTDIN(InputFileList[i]);
+
     if (std::error_code EC = InputBuffer.getError())
       return Error("unable to read input: '" + EC.message() + "'");
 
-    std::unique_ptr<ObjectImage> LoadedObject;
+    ErrorOr<std::unique_ptr<ObjectFile>> MaybeObj(
+      ObjectFile::createObjectFile((*InputBuffer)->getMemBufferRef()));
+
+    if (std::error_code EC = MaybeObj.getError())
+      return Error("unable to create object file: '" + EC.message() + "'");
+
+    ObjectFile &Obj = **MaybeObj;
+
     // Load the object file
-    LoadedObject = Dyld.loadObject(
-        llvm::make_unique<ObjectBuffer>(std::move(*InputBuffer)));
-    if (!LoadedObject) {
+    Dyld.loadObject(Obj);
+    if (Dyld.hasError()) {
       return Error(Dyld.getErrorString());
     }
   }