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diff --git a/include/Support/DenseMap.h b/include/Support/DenseMap.h
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+++ b/include/Support/DenseMap.h
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+//===- DenseMap.h - A dense map implmentation -------------------*- C++ -*-===//
+// 
+//                     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 a dense map. A dense map template takes two
+// types. The first is the mapped type and the second is a functor
+// that maps its argument to a size_t. On instanciation a "null" value
+// can be provided to be used as a "does not exist" indicator in the
+// map. A member function grow() is provided that given the value of
+// the maximally indexed key (the argument of the functor) makes sure
+// the map has enough space for it.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef SUPPORT_DENSEMAP_H
+#define SUPPORT_DENSEMAP_H
+
+#include <vector>
+
+namespace llvm {
+
+template <typename T, typename ToIndexT>
+class DenseMap {
+    typedef typename ToIndexT::argument_type IndexT;
+    typedef std::vector<T> StorageT;
+    StorageT storage_;
+    T nullVal_;
+    ToIndexT toIndex_;
+
+public:
+    DenseMap() { }
+
+    explicit DenseMap(const T& val) : nullVal_(val) { }
+
+    typename StorageT::reference operator[](IndexT n) {
+        assert(toIndex_(n) < storage_.size() && "index out of bounds!");
+        return storage_[toIndex_(n)];
+    }
+
+    typename StorageT::const_reference operator[](IndexT n) const {
+        assert(toIndex_(n) < storage_.size() && "index out of bounds!");
+        return storage_[toIndex_(n)];
+    }
+
+    void clear() {
+        storage_.assign(storage_.size(), nullVal_);
+    }
+
+    void grow(IndexT n) {
+        storage_.resize(toIndex_(n) + 1, nullVal_);
+    }
+};
+
+} // End llvm namespace
+
+#endif