FULL PRODUCT VERSION :
java version "1.6.0-beta2"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.6.0-beta2-b72)
Java HotSpot(TM) Client VM (build 1.6.0-beta2-b72, mixed mode)


ADDITIONAL OS VERSION INFORMATION :
Linux cehost 2.6.15-1.1831_FC4 #1 Tue Feb 7 13:37:42 EST 2006 i686 i686 i386 GNU/Linux

EXTRA RELEVANT SYSTEM CONFIGURATION :
Pentium4 Northwood, 2.6ghz

A DESCRIPTION OF THE PROBLEM :
I use some encryption code in my application and just for interest I thought benchmarking it would be quite interesting. The code was ported from C (not by me) and performs quite poor on hotspot.
Please don't comment on code-quality, it is just an example where code generated by hotspot does not perform as well as it could.

Here are some numbers for the original version:
IBM 1.4.2:                             2.29874488529263mb/s
Hotspot 1.3.1 Server:         1.6164489848700376mb/s
Hotspot 6.0b72 Server:     1.5088873464707124mb/s

Numbers for the tuned Version:
Hotspot 1.3.1 Server:       2.9244896765514414mb/s
Hotspot 6.0b72 Server:   2.7785495971103082mb/s
IBM 1.4.2:                           2.7506312220847015mb/s

Both times the Hotspot 1.3.1 Server  compiler produces faster code, thats why I marked it as regression.
The main problem seems to be the access to member-variables inside of code(), IBM can optimize this quite well whereas Hotspot has some troubles with the code.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Run the sample-code attached with the server compiler.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Mustang's c2 should at least be faster than 1.3.1's hotspot server compiler.
ACTUAL -
6.0b72 is always slower than 1.3.1, IBM seems to handle member-field access much better on P4.

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
1.) Not tuned version:
-----------------------------------------------------------------------
/* PORTED TO JAVA BY ROBERT NEILD November 1999 */

/* PC1 Cipher Algorithm ( Pukall Cipher 1 ) */
/* By Alexander PUKALL 1991 */
/* free code no restriction to use */
/* please include the name of the Author in the final software */
/* the Key is 128 bits */

/* Only the K zone change in the two routines */
/* You can create a single routine with the two parts in it */

public class PC1_Stream
{
	int ax, bx, cx, dx, si, tmp, x1a2, res, i, inter, cfc, cfd, compte;
	int x1a0[] = new int[8];
	byte cle[] = new byte[17]; // Hold key
	private boolean usedAsEncrypter = false;
	private boolean alreadyUsed = false;

	/**
	 * Creates a PC1_InputStream. Decodes an input stream of encoded data.
	 * @param in  The input stream to decode.
	 * @param password 16 byte encryption key
	 */

	public PC1_Stream(byte[] password)
	{
		System.arraycopy(password, 0, cle, 0, Math.min(16, password.length));
	}

	private void assemble()
	{
		x1a0[0] = ((cle[0] * 256) + cle[1]);

		code();
		inter = res;

		x1a0[1] = (x1a0[0] ^ ((cle[2] * 256) + cle[3]));
		code();
		inter = (inter ^ res);

		x1a0[2] = (x1a0[1] ^ ((cle[4] * 256) + cle[5]));
		code();
		inter = (inter ^ res);

		x1a0[3] = (x1a0[2] ^ ((cle[6] * 256) + cle[7]));
		code();
		inter = (inter ^ res);

		x1a0[4] = (x1a0[3] ^ ((cle[8] * 256) + cle[9]));
		code();
		inter = (inter ^ res);

		x1a0[5] = (x1a0[4] ^ ((cle[10] * 256) + cle[11]));
		code();
		inter = (inter ^ res);

		x1a0[6] = (x1a0[5] ^ ((cle[12] * 256) + cle[13]));
		code();
		inter = (inter ^ res);

		x1a0[7] = (x1a0[6] ^ ((cle[14] * 256) + cle[15]));
		code();
		inter = (inter ^ res);

		i = 0;
	}

	void code()
	{
		dx = (x1a2 + i);
		ax = x1a0[i];

		cx = 0x015a;
		bx = 0x4e35;

		tmp = ax;
		ax = si;
		si = tmp;

		tmp = ax;
		ax = dx;
		dx = tmp;

		if (ax != 0)
		{
			ax = (ax * bx);
		}

		tmp = ax;
		ax = cx;
		cx = tmp;

		if (ax != 0)
		{
			ax = (ax * si);
			cx = (ax + cx);
		}

		tmp = ax;
		ax = si;
		si = tmp;
		ax = (ax * bx);
		dx = (cx + dx);

		ax = (ax + 1);

		x1a2 = dx;
		x1a0[i] = ax;

		res = (ax ^ dx);
		i = (i + 1);
	}

	/**
	 * Returns a plain byte, which has been unencrypted from the underlying
	 * InputStream.
	 * @see java.io.FilterInputStream
	 */

	public byte[] decrypt(byte[] encryptedData)
	{
		checkUsage(false);

		for (int i = 0; i < encryptedData.length; i++)
		{
			int c = encryptedData[i];

			assemble();
			cfc = (inter >> 8);
			cfd = (inter & 255);

			c = c ^ (cfc ^ cfd);

			for (compte = 0; compte <= 15; compte++)
			{
				/* we mix the plaintext byte with the key */
				cle[compte] = (byte) (cle[compte] ^ c);
			}

			encryptedData[i] = (byte) c;
		}

		return encryptedData;
	}

	public byte[] encrypt(byte[] data)
	{
		checkUsage(true);

		for (int i = 0; i < data.length; i++)
		{
			int c = data[i];

			assemble();
			cfc = (inter >> 8);
			cfd = (inter & 255);

			for (compte = 0; compte <= 15; compte++)
			{
				/* we mix the plaintext byte with the key */
				cle[compte] = (byte) (cle[compte] ^ c);
			}

			c = c ^ (cfc ^ cfd);
			data[i] = (byte) c;
		}

		return data;
	}

	private void checkUsage(boolean isEncrypter)
	{
		if (alreadyUsed)
		{
			if (usedAsEncrypter != isEncrypter)
			{
				throw new IllegalArgumentException("You may either use this class as encrypter or decrypter, not both!");
			}
		} else
		{
			alreadyUsed = true;
			usedAsEncrypter = isEncrypter;
		}
	}

	public static void main(String[] args)
	{
		byte[] testData = new byte[1024 * 1024];
		for (int i = 0; i < testData.length; i++)
		{
			testData[i] = (byte) (i % 127);
		}

		PC1_Stream dec = new PC1_Stream(testData);
		PC1_Stream enc = new PC1_Stream(testData);

		for (int i = 0; i < 5; i++)
		{
			enc.encrypt(testData);
			dec.decrypt(testData);
		}

		for (int m = 0; m < 10; m++)
		{
			int encCount = 50;
			System.out.println("Starte Verschl����sselung");
			long start = System.currentTimeMillis();
			for (int i = 0; i < encCount; i++)
			{
				enc.encrypt(testData);
				dec.decrypt(testData);
			}
			long end = System.currentTimeMillis();
			long duration = end - start;
			System.out.println("Encryption took: " + duration + " with " + ((double) encCount / ((double) duration / (double) 1000)) + "mb/s ");
		}
	}
}
------------------------------------------------------------------------------

2.) Slightly tuned version:
-----------------------------------------------------------------------------
public class PC1_Stream_tuned
{
	int si, x1a2;
	int x1a0[] = new int[8];
	byte cle[] = new byte[17]; // Hold key
	private boolean usedAsEncrypter = false;
	private boolean alreadyUsed = false;

	/**
	 * Creates a PC1_InputStream. Decodes an input stream of encoded data.
	 * @param in  The input stream to decode.
	 * @param password 16 byte encryption key
	 */

	public PC1_Stream_tuned(byte[] password)
	{
		System.arraycopy(password, 0, cle, 0, Math.min(16, password.length));
	}

	private int assemble()
	{
		x1a0[0] = ((cle[0] * 256) + cle[1]);

		int inter = code(0);

		x1a0[1] = (x1a0[0] ^ ((cle[2] * 256) + cle[3]));
		inter = inter ^ code(1);

		x1a0[2] = (x1a0[1] ^ ((cle[4] * 256) + cle[5]));
		inter = inter ^ code(2);

		x1a0[3] = (x1a0[2] ^ ((cle[6] * 256) + cle[7]));
		inter = inter ^ code(3);

		x1a0[4] = (x1a0[3] ^ ((cle[8] * 256) + cle[9]));
		inter = inter ^ code(4);

		x1a0[5] = (x1a0[4] ^ ((cle[10] * 256) + cle[11]));
		inter = inter ^ code(5);

		x1a0[6] = (x1a0[5] ^ ((cle[12] * 256) + cle[13]));
		inter = inter ^ code(6);

		x1a0[7] = (x1a0[6] ^ ((cle[14] * 256) + cle[15]));
		inter = inter ^ code(7);
		
		return inter;
	}

	protected int code(final int i)
	{
		int ax = x1a0[i];
		int dx = (x1a2 + i);
		int cx = 0x015a;
		int tmp;
		final int bx = 0x4e35;
	
		tmp = ax;
		ax = si;
		si = tmp;

		tmp = ax;
		ax = dx;
		dx = tmp;

		if (ax != 0)
		{
			ax = (ax * bx);
		}

		tmp = ax;
		ax = cx;
		cx = tmp;

		if (ax != 0)
		{
			ax = (ax * si);
			cx = (ax + cx);
		}

		tmp = ax;
		ax = si;
		si = tmp;
		
		ax = (ax * bx);
		dx = (cx + dx);
		ax++;

		x1a2 = dx;
		x1a0[i] = ax;

		return  (ax ^ dx);
	}

	/**
	 * Returns a plain byte, which has been unencrypted from the underlying
	 * InputStream.
	 * @see java.io.FilterInputStream
	 */

	public byte[] decrypt(byte[] encryptedData)
	{
		checkUsage(false);

		for (int i = 0; i < encryptedData.length; i++)
		{
			int c = encryptedData[i];

			int inter = assemble();
			int cfc = (inter >> 8);
			int cfd = (inter & 255);

			c = c ^ (cfc ^ cfd);

			for (int compte = 0; compte <= 15; compte++)
			{
				/* we mix the plaintext byte with the key */
				cle[compte] = (byte) (cle[compte] ^ c);
			}

			encryptedData[i] = (byte) c;
		}

		return encryptedData;
	}

	public byte[] encrypt(byte[] data)
	{
		checkUsage(true);

		for (int i = 0; i < data.length; i++)
		{
			int c = data[i];

			int inter = assemble();
			int cfc = (inter >> 8);
			int cfd = (inter & 255);

			for (int compte = 0; compte <= 15; compte++)
			{
				/* we mix the plaintext byte with the key */
				cle[compte] = (byte) (cle[compte] ^ c);
			}

			c = c ^ (cfc ^ cfd);
			data[i] = (byte) c;
		}

		return data;
	}

	private void checkUsage(boolean isEncrypter)
	{
		if (alreadyUsed)
		{
			if (usedAsEncrypter != isEncrypter)
			{
				throw new IllegalArgumentException("You may either use this class as encrypter or decrypter, not both!");
			}
		} else
		{
			alreadyUsed = true;
			usedAsEncrypter = isEncrypter;
		}
	}

	public static void main(String[] args)
	{
		byte[] testData = new byte[1024 * 1024];
		for (int i = 0; i < testData.length; i++)
		{
			testData[i] = (byte) (i % 127);
		}

		PC1_Stream_tuned dec = new PC1_Stream_tuned(testData);
		PC1_Stream_tuned enc = new PC1_Stream_tuned(testData);

		for (int i = 0; i < 5; i++)
		{
			enc.encrypt(testData);
			dec.decrypt(testData);
		}

		for (int m = 0; m < 10; m++)
		{
			int encCount = 50;
			System.out.println("Starte Verschl����sselung");
			long start = System.currentTimeMillis();
			for (int i = 0; i < encCount; i++)
			{
				enc.encrypt(testData);
				dec.decrypt(testData);
			}
			long end = System.currentTimeMillis();
			long duration = end - start;
			System.out.println("Encryption took: " + duration + " with " + ((double) encCount / ((double) duration / (double) 1000)) + "mb/s ");
		}
	}
}


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

CUSTOMER SUBMITTED WORKAROUND :
use IBM Jvm, try to not access member-variables too often.

Release Regression From : 1.3.1
The above release value was the last known release where this 
bug was known to work. Since then there has been a regression.