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diff --git a/include/lld/Core/Pass.h b/include/lld/Core/Pass.h
new file mode 100644
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+++ b/include/lld/Core/Pass.h
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+//===------ Core/Pass.h - Base class for linker passes --------------------===//
+//
+//                             The LLVM Linker
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLD_CORE_PASS_H
+#define LLD_CORE_PASS_H
+
+#include "lld/Core/Atom.h"
+#include "lld/Core/File.h"
+#include "lld/Core/Reference.h"
+#include "lld/Core/range.h"
+#include <vector>
+
+namespace lld {
+class MutableFile;
+
+/// Once the core linking is done (which resolves references, coalesces atoms
+/// and produces a complete Atom graph), the linker runs a series of passes
+/// on the Atom graph. The graph is modeled as a File, which means the pass
+/// has access to all the atoms and to File level attributes. Each pass does
+/// a particular transformation to the Atom graph or to the File attributes.
+///
+/// This is the abstract base class for all passes.  A Pass does its
+/// actual work in it perform() method.  It can iterator over Atoms in the
+/// graph using the *begin()/*end() atom iterator of the File.  It can add
+/// new Atoms to the graph using the File's addAtom() method.
+class Pass {
+public:
+  virtual ~Pass() { }
+
+  /// Do the actual work of the Pass.
+  virtual void perform(std::unique_ptr<MutableFile> &mergedFile) = 0;
+
+protected:
+  // Only subclassess can be instantiated.
+  Pass() { }
+};
+
+} // namespace lld
+
+#endif // LLD_CORE_PASS_H