FULL PRODUCT VERSION :
java version "1.6.0_23"
Java(TM) SE Runtime Environment (build 1.6.0_23-b05)
Java HotSpot(TM) 64-Bit Server VM (build 19.0-b09, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 6.1.7600]
Linux localhost 2.6.36-gentoo-r5 #3 SMP PREEMPT Tue Dec 21 18:22:19 MSK 2010 x86_64 Intel(R) Core(TM)2 Duo CPU P8600 @ 2.40GHz GenuineIntel GNU/Linux

A DESCRIPTION OF THE PROBLEM :
Sometimes the loop conditions are substituted the wrong way during the optimization, causing the code to malfunction.

In the example included, the code should always terminate in finite time:
            short value = 0;
            do {
                sum += Integer.bitCount(value);
            } while (++value != 0);
However, the loop condition seem to be substituted by "true", so the loop becomes infinite.

This affects server versions of 32-bit and 64-bit JVMs of at least releases 1.6.0_23 under Windows and 1.6.0_24 under Linux.

In Linux (java 1.6.0_24), the java process takes both (all?) available CPU cores and can be killed only by signal 9.
In Windows (java 1.6.0_23), the process takes only one CPU core and can be killed from task manager.

The client version of 32-bit JVM runs normally.
java -Xint runs normally (but very slow).

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Compile and run the included source code.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The program outputs the lines like the following and stops:
1: 512
2: 519
3: 522
4: 517
doNotOptimizeOut value: -100663296

ACTUAL -
The program outputs the following lines and hangs:
1: 363
2: 348


REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
public class OptimizerBug {
    private static final int ITERATIONS = 1000;
    private static int doNotOptimizeOut = 0;

    public static long bitCountShort() {
        long t0 = System.currentTimeMillis();
        int sum = 0;
        for (int it = 0; it < ITERATIONS; ++it) {
            short value = 0;
            do {
                sum += Integer.bitCount(value);
            } while (++value != 0);
        }
        doNotOptimizeOut += sum;
        return System.currentTimeMillis() - t0;
    }

    public static void main(String[] args) {
        for (int i = 0; i < 4; ++i) {
            System.out.println((i + 1) + ": " + bitCountShort());
        }
        System.out.println("doNotOptimizeOut value: " + doNotOptimizeOut);
    }
}

---------- END SOURCE ----------