NumberHighestOneBit.java

/*
This file is part of jpcsp.

Jpcsp is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

Jpcsp 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 for more details.

You should have received a copy of the GNU General Public License
along with Jpcsp.  If not, see <http://www.gnu.org/licenses/>.
 */
package jpcsp.Allegrex.compiler.nativeCode;

/**
 * @author gid15
 *
 */
public class NumberHighestOneBit extends AbstractNativeCodeSequence {
	private static final int[] precomputedSpecial1 = new int[256];

	static {
		for (int n = 0; n < precomputedSpecial1.length; n++) {
			precomputedSpecial1[n] = computeSpecial1(n);
		}
	}

	static public void call(int valueReg, int bitReg) {
		int value = getRegisterValue(valueReg);
		int bit = getRegisterValue(bitReg);

		for (; bit > 0; bit--) {
			if (((value >>> bit) & 1) != 0) {
				break;
			}
		}

		setRegisterValue(bitReg, bit);
	}

	static private int computeSpecial1(int n) {
		if ((n & 255) == 0)
			return 0;
		if ((n & 128) == 0)
			return 1;
		if ((n & 64) == 0)
			return 0;
		if ((n & 32) == 0)
			return 2;
		if ((n & 16) == 0)
			return 3;
		if ((n & 8) == 0)
			return 4;
		return 0;
	}

	static public void callSpecial1(int valueReg) {
		int value = getRegisterValue(valueReg);
		int result = precomputedSpecial1[value & 0xFF];
		setGprV0(result);
	}
}