Implement LLVM JIT side of GDB JIT debugging interface

lib/ExecutionEngine/JIT/JITDebugRegisterer.h

Index: lib/ExecutionEngine/JIT/JITDebugRegisterer.h
===================================================================
--- lib/ExecutionEngine/JIT/JITDebugRegisterer.h	(revision 0)
+++ lib/ExecutionEngine/JIT/JITDebugRegisterer.h	(revision 0)
@@ -0,0 +1,116 @@
+//===-- JITDebugRegisterer.h - Register debug symbols for JIT -------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines a JITDebugRegisterer object that is used by the JIT to
+// register debug info with debuggers like GDB.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_EXECUTION_ENGINE_JIT_DEBUGREGISTERER_H
+#define LLVM_EXECUTION_ENGINE_JIT_DEBUGREGISTERER_H
+
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/Support/DataTypes.h"
+#include <string>
+
+// This must be kept in sync with gdb/gdb/jit.h .
+extern "C" {
+
+  typedef enum {
+    JIT_NOACTION = 0,
+    JIT_REGISTER_FN,
+    JIT_UNREGISTER_FN
+  } jit_actions_t;
+
+  struct jit_code_entry {
+    struct jit_code_entry *next_entry;
+    struct jit_code_entry *prev_entry;
+    const char *symfile_addr;
+    uint64_t symfile_size;
+  };
+
+  struct jit_descriptor {
+    uint32_t version;
+    // This should be jit_actions_t, but we want to be specific about the
+    // bit-width.
+    uint32_t action_flag;
+    struct jit_code_entry *relevant_entry;
+    struct jit_code_entry *first_entry;
+  };
+
+}
+
+namespace llvm {
+
+struct ELFSection;
+class Function;
+class TargetMachine;
+
+
+/// This class encapsulates information we want to send to the debugger.
+///
+struct DebugInfo {
+  uint8_t *FnStart;
+  uint8_t *FnEnd;
+  uint8_t *EhStart;
+  uint8_t *EhEnd;
+
+  DebugInfo() : FnStart(0), FnEnd(0), EhStart(0), EhEnd(0) {}
+};
+
+typedef DenseMap< const Function*, std::pair<std::string, jit_code_entry*> >
+  RegisteredFunctionsMap;
+
+/// This class registers debug info for JITed code with an attached debugger.
+/// Without proper debug info, GDB can't do things like source level debugging
+/// or even produce a proper stack trace on linux-x86_64.  To use this class,
+/// whenever a function is JITed, create a DebugInfo struct and pass it to the
+/// RegisterFunction method.  The method will then do whatever is necessary to
+/// inform the debugger about the JITed function.
+class JITDebugRegisterer {
+
+  TargetMachine &TM;
+
+  /// FnMap - A map of functions that have been registered to the associated
+  /// temporary files.  Used for cleanup.
+  RegisteredFunctionsMap FnMap;
+
+  /// MakeELF - Builds the ELF file in memory and returns a std::string that
+  /// contains the ELF.
+  std::string MakeELF(const Function *F, DebugInfo &I);
+
+public:
+  JITDebugRegisterer(TargetMachine &tm);
+
+  /// ~JITDebugRegisterer - Unregisters all code and frees symbol files.
+  ///
+  ~JITDebugRegisterer();
+
+  /// RegisterFunction - Register debug info for the given function with an
+  /// attached debugger.  Clients must call UnregisterFunction on all
+  /// registered functions before deleting them to free the associated symbol
+  /// file and unregister it from the debugger.
+  void RegisterFunction(const Function *F, DebugInfo &I);
+
+  /// UnregisterFunction - Unregister the debug info for the given function
+  /// from the debugger and free associated memory.
+  void UnregisterFunction(const Function *F);
+
+private:
+  /// UnregisterFunctionInternal - Unregister the debug info for the given
+  /// function from the debugger and delete any temporary files.  The private
+  /// version of this method does not remove the function from FnMap so that it
+  /// can be called while iterating over FnMap.
+  void UnregisterFunctionInternal(RegisteredFunctionsMap::iterator I);
+
+};
+
+} // end namespace llvm
+
+#endif // LLVM_EXECUTION_ENGINE_JIT_DEBUGREGISTERER_H