[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, 48 insertions, 0 deletions

diff --git a/llvm/lib/ExecutionEngine/MCJIT/ObjectBuffer.h b/llvm/lib/ExecutionEngine/MCJIT/ObjectBuffer.h
new file mode 100644
index 0000000..92310f3
--- /dev/null
+++ b/llvm/lib/ExecutionEngine/MCJIT/ObjectBuffer.h
@@ -0,0 +1,48 @@
+//===--- ObjectBuffer.h - Utility class to wrap object memory ---*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file declares a wrapper class to hold the memory into which an
+// object will be generated.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_EXECUTIONENGINE_OBJECTBUFFER_H
+#define LLVM_EXECUTIONENGINE_OBJECTBUFFER_H
+
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/raw_ostream.h"
+
+namespace llvm {
+
+class ObjectMemoryBuffer : public MemoryBuffer {
+public:
+  template <unsigned N>
+  ObjectMemoryBuffer(SmallVector<char, N> SV)
+    : SV(SV), BufferName("<in-memory object>") {
+    init(this->SV.begin(), this->SV.end(), false);
+  }
+
+  template <unsigned N>
+  ObjectMemoryBuffer(SmallVector<char, N> SV, StringRef Name)
+    : SV(SV), BufferName(Name) {
+    init(this->SV.begin(), this->SV.end(), false);
+  }
+  const char* getBufferIdentifier() const override { return BufferName.c_str(); }
+
+  BufferKind getBufferKind() const override { return MemoryBuffer_Malloc; }
+
+private:
+  SmallVector<char, 4096> SV;
+  std::string BufferName;
+};
+
+} // namespace llvm
+
+#endif