diff --git a/lib/Debugger/RuntimeInfo.cpp b/lib/Debugger/RuntimeInfo.cpp
new file mode 100644
index 0000000..5d45104
--- /dev/null
+++ b/lib/Debugger/RuntimeInfo.cpp
@@ -0,0 +1,69 @@
+//===-- RuntimeInfo.cpp - Compute and cache info about running program ----===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file was developed by the LLVM research group and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the RuntimeInfo and related classes, by querying and
+// cachine information from the running inferior process.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Debugger/InferiorProcess.h"
+#include "llvm/Debugger/ProgramInfo.h"
+#include "llvm/Debugger/RuntimeInfo.h"
+using namespace llvm;
+
+//===----------------------------------------------------------------------===//
+// StackFrame class implementation
+
+StackFrame::StackFrame(RuntimeInfo &ri, void *ParentFrameID)
+  : RI(ri), SourceInfo(0) {
+  FrameID = RI.getInferiorProcess().getPreviousFrame(ParentFrameID);
+  if (FrameID == 0) throw "Stack frame does not exist!";
+
+  // Compute lazily as needed.
+  FunctionDesc = 0;
+}
+
+const GlobalVariable *StackFrame::getFunctionDesc() {
+  if (FunctionDesc == 0)
+    FunctionDesc = RI.getInferiorProcess().getSubprogramDesc(FrameID);
+  return FunctionDesc;
+}
+
+/// getSourceLocation - Return the source location that this stack frame is
+/// sitting at.
+void StackFrame::getSourceLocation(unsigned &lineNo, unsigned &colNo,
+                                   const SourceFileInfo *&sourceInfo) {
+  if (SourceInfo == 0) {
+    const GlobalVariable *SourceDesc = 0;
+    RI.getInferiorProcess().getFrameLocation(FrameID, LineNo,ColNo, SourceDesc);
+    SourceInfo = &RI.getProgramInfo().getSourceFile(SourceDesc);
+  }
+
+  lineNo = LineNo;
+  colNo = ColNo;
+  sourceInfo = SourceInfo;
+}
+
+//===----------------------------------------------------------------------===//
+// RuntimeInfo class implementation
+
+/// materializeFrame - Create and process all frames up to and including the
+/// specified frame number.  This throws an exception if the specified frame
+/// ID is nonexistant.
+void RuntimeInfo::materializeFrame(unsigned ID) {
+  assert(ID >= CallStack.size() && "no need to materialize this frame!");
+  void *CurFrame = 0;
+  if (!CallStack.empty())
+    CurFrame = CallStack.back().getFrameID();
+
+  while (CallStack.size() <= ID) {
+    CallStack.push_back(StackFrame(*this, CurFrame));
+    CurFrame = CallStack.back().getFrameID();
+  }
+}