diff -r 000000000000 -r 9a66ca7c79fa src/share/classes/com/sun/tools/javac/util/Bits.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/share/classes/com/sun/tools/javac/util/Bits.java	Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,222 @@
+/*
+ * Copyright 1999-2005 Sun Microsystems, Inc.  All Rights Reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Sun designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Sun in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ */
+
+package com.sun.tools.javac.util;
+
+/** A class for extensible, mutable bit sets.
+ *
+ *  <p><b>This is NOT part of any API supported by Sun Microsystems.  If
+ *  you write code that depends on this, you do so at your own risk.
+ *  This code and its internal interfaces are subject to change or
+ *  deletion without notice.</b>
+ */
+public class Bits {
+
+
+    private final static int wordlen = 32;
+    private final static int wordshift = 5;
+    private final static int wordmask = wordlen - 1;
+
+    private int[] bits;
+
+    /** Construct an initially empty set.
+     */
+    public Bits() {
+        this(new int[1]);
+    }
+
+    /** Construct a set consisting initially of given bit vector.
+     */
+    public Bits(int[] bits) {
+        this.bits = bits;
+    }
+
+    /** Construct a set consisting initially of given range.
+     */
+    public Bits(int start, int limit) {
+        this();
+        inclRange(start, limit);
+    }
+
+    private void sizeTo(int len) {
+        if (bits.length < len) {
+            int[] newbits = new int[len];
+            System.arraycopy(bits, 0, newbits, 0, bits.length);
+            bits = newbits;
+        }
+    }
+
+    /** This set = {}.
+     */
+    public void clear() {
+        for (int i = 0; i < bits.length; i++) bits[i] = 0;
+    }
+
+    /** Return a copy of this set.
+     */
+    public Bits dup() {
+        int[] newbits = new int[bits.length];
+        System.arraycopy(bits, 0, newbits, 0, bits.length);
+        return new Bits(newbits);
+    }
+
+    /** Include x in this set.
+     */
+    public void incl(int x) {
+        assert x >= 0;
+        sizeTo((x >>> wordshift) + 1);
+        bits[x >>> wordshift] = bits[x >>> wordshift] |
+            (1 << (x & wordmask));
+    }
+
+
+    /** Include [start..limit) in this set.
+     */
+    public void inclRange(int start, int limit) {
+        sizeTo((limit >>> wordshift) + 1);
+        for (int x = start; x < limit; x++)
+            bits[x >>> wordshift] = bits[x >>> wordshift] |
+                (1 << (x & wordmask));
+    }
+
+    /** Exclude x from this set.
+     */
+    public void excl(int x) {
+        assert x >= 0;
+        sizeTo((x >>> wordshift) + 1);
+        bits[x >>> wordshift] = bits[x >>> wordshift] &
+            ~(1 << (x & wordmask));
+    }
+
+    /** Is x an element of this set?
+     */
+    public boolean isMember(int x) {
+        return
+            0 <= x && x < (bits.length << wordshift) &&
+            (bits[x >>> wordshift] & (1 << (x & wordmask))) != 0;
+    }
+
+    /** this set = this set & xs.
+     */
+    public Bits andSet(Bits xs) {
+        sizeTo(xs.bits.length);
+        for (int i = 0; i < xs.bits.length; i++)
+            bits[i] = bits[i] & xs.bits[i];
+        return this;
+    }
+
+    /** this set = this set | xs.
+     */
+    public Bits orSet(Bits xs) {
+        sizeTo(xs.bits.length);
+        for (int i = 0; i < xs.bits.length; i++)
+            bits[i] = bits[i] | xs.bits[i];
+        return this;
+    }
+
+    /** this set = this set \ xs.
+     */
+    public Bits diffSet(Bits xs) {
+        for (int i = 0; i < bits.length; i++) {
+            if (i < xs.bits.length) {
+                bits[i] = bits[i] & ~xs.bits[i];
+            }
+        }
+        return this;
+    }
+
+    /** this set = this set ^ xs.
+     */
+    public Bits xorSet(Bits xs) {
+        sizeTo(xs.bits.length);
+        for (int i = 0; i < xs.bits.length; i++)
+            bits[i] = bits[i] ^ xs.bits[i];
+        return this;
+    }
+
+    /** Count trailing zero bits in an int. Algorithm from "Hacker's
+     *  Delight" by Henry S. Warren Jr. (figure 5-13)
+     */
+    private static int trailingZeroBits(int x) {
+        assert wordlen == 32;
+        if (x == 0) return 32;
+        int n = 1;
+        if ((x & 0xffff) == 0) { n += 16; x >>>= 16; }
+        if ((x & 0x00ff) == 0) { n +=  8; x >>>=  8; }
+        if ((x & 0x000f) == 0) { n +=  4; x >>>=  4; }
+        if ((x & 0x0003) == 0) { n +=  2; x >>>=  2; }
+        return n - (x&1);
+    }
+
+    /** Return the index of the least bit position >= x that is set.
+     *  If none are set, returns -1.  This provides a nice way to iterate
+     *  over the members of a bit set:
+     *  <pre>
+     *  for (int i = bits.nextBit(0); i>=0; i = bits.nextBit(i+1)) ...
+     *  </pre>
+     */
+    public int nextBit(int x) {
+        int windex = x >>> wordshift;
+        if (windex >= bits.length) return -1;
+        int word = bits[windex] & ~((1 << (x & wordmask))-1);
+        while (true) {
+            if (word != 0)
+                return (windex << wordshift) + trailingZeroBits(word);
+            windex++;
+            if (windex >= bits.length) return -1;
+            word = bits[windex];
+        }
+    }
+
+    /** a string representation of this set.
+     */
+    public String toString() {
+        char[] digits = new char[bits.length * wordlen];
+        for (int i = 0; i < bits.length * wordlen; i++)
+            digits[i] = isMember(i) ? '1' : '0';
+        return new String(digits);
+    }
+
+    /** Test Bits.nextBit(int). */
+    public static void main(String[] args) {
+        java.util.Random r = new java.util.Random();
+        Bits bits = new Bits();
+        int dupCount = 0;
+        for (int i=0; i<125; i++) {
+            int k;
+            do {
+                k = r.nextInt(250);
+            } while (bits.isMember(k));
+            System.out.println("adding " + k);
+            bits.incl(k);
+        }
+        int count = 0;
+        for (int i = bits.nextBit(0); i >= 0; i = bits.nextBit(i+1)) {
+            System.out.println("found " + i);
+            count ++;
+        }
+        if (count != 125) throw new Error();
+    }
+}