Revert "Revert "Favor free list allocation to bump pointer allocation.""

runtime/vm/bit_set.h

Index: runtime/vm/bit_set.h
diff --git a/runtime/vm/bit_set.h b/runtime/vm/bit_set.h
new file mode 100644
index 0000000000000000000000000000000000000000..7fba930d90300bb0ceff278dd699f9503c604eb9
--- /dev/null
+++ b/runtime/vm/bit_set.h
@@ -0,0 +1,53 @@
+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+#ifndef VM_BIT_SET_H_
+#define VM_BIT_SET_H_
+
+#include "vm/globals.h"
+
+namespace dart {
+
+// Just like its namesake in the STL, a BitSet object contains a fixed
+// length sequence of bits.
+template<intptr_t N>
+class BitSet {
+ public:
+  BitSet() {
+    Reset();
+  }
+
+  void Set(intptr_t i, bool value) {
+    ASSERT(i >= 0);
+    ASSERT(i < N);
+    uword mask = (static_cast<uword>(1) << (i % kBitsPerWord));
+    if (value) {
+      data_[i / kBitsPerWord] |= mask;
+    } else {
+      data_[i / kBitsPerWord] &= ~mask;
+    }
+  }
+
+  bool Test(intptr_t i) {
+    ASSERT(i >= 0);
+    ASSERT(i < N);
+    uword mask = (static_cast<uword>(1) << (i % kBitsPerWord));
+    return (data_[i / kBitsPerWord] & mask) != 0;
+  }
+
+  void Reset() {
+    memset(data_, 0, sizeof(data_));
+  }
+
+  intptr_t Size() const {
+    return N;
+  }
+
+ private:
+  uword data_[1 + ((N - 1) / kBitsPerWord)];
+};
+
+}  // namespace dart
+
+#endif  // VM_BIT_SET_H_