condcodes.hh

来自「M5,一个功能强大的多处理器系统模拟器.很多针对处理器架构,性能的研究都使用它作」· HH 代码 · 共 95 行

/*
 * Copyright (c) 2003, 2004, 2005
 * The Regents of The University of Michigan
 * All Rights Reserved
 *
 * This code is part of the M5 simulator.
 *
 * Permission is granted to use, copy, create derivative works and
 * redistribute this software and such derivative works for any
 * purpose, so long as the copyright notice above, this grant of
 * permission, and the disclaimer below appear in all copies made; and
 * so long as the name of The University of Michigan is not used in
 * any advertising or publicity pertaining to the use or distribution
 * of this software without specific, written prior authorization.
 *
 * THIS SOFTWARE IS PROVIDED AS IS, WITHOUT REPRESENTATION FROM THE
 * UNIVERSITY OF MICHIGAN AS TO ITS FITNESS FOR ANY PURPOSE, AND
 * WITHOUT WARRANTY BY THE UNIVERSITY OF MICHIGAN OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE. THE REGENTS OF THE UNIVERSITY OF MICHIGAN SHALL NOT BE
 * LIABLE FOR ANY DAMAGES, INCLUDING DIRECT, SPECIAL, INDIRECT,
 * INCIDENTAL, OR CONSEQUENTIAL DAMAGES, WITH RESPECT TO ANY CLAIM
 * ARISING OUT OF OR IN CONNECTION WITH THE USE OF THE SOFTWARE, EVEN
 * IF IT HAS BEEN OR IS HEREAFTER ADVISED OF THE POSSIBILITY OF SUCH
 * DAMAGES.
 *
 * Authors: Gabe Black
 */

#ifndef __BASE_CONDCODE_HH__
#define __BASE_CONDCODE_HH__

#include "base/bitfield.hh"
#include "base/trace.hh"

/**
 * Calculate the carry flag from an addition. This should work even when
 * a carry value is also added in.
 */
inline
bool
findCarry(int width, uint64_t dest, uint64_t src1, uint64_t src2) {
    int shift = width - 1;
    return ((~(dest >> shift) & 1) +
            ((src1 >> shift) & 1) +
            ((src2 >> shift) & 1)) & 0x2;
}

/**
 * Calculate the overflow flag from an addition.
 */
inline
bool
findOverflow(int width, uint64_t dest, uint64_t src1, uint64_t src2) {
    int shift = width - 1;
    return ((src1 ^ ~src2) & (src1 ^ dest)) & (1ULL << shift);
}

/**
 * Calculate the parity of a value. 1 is for odd parity and 0 is for even.
 */
inline
bool
findParity(int width, uint64_t dest) {
    dest &= mask(width);
    dest ^= (dest >> 32);
    dest ^= (dest >> 16);
    dest ^= (dest >> 8);
    dest ^= (dest >> 4);
    dest ^= (dest >> 2);
    dest ^= (dest >> 1);
    return dest & 1;
}

/**
 * Calculate the negative flag.
 */
inline
bool
findNegative(int width, uint64_t dest) {
    return bits(dest, width - 1, width - 1);
}

/**
 * Calculate the zero flag.
 */
inline
bool
findZero(int width, uint64_t dest) {
    return !(dest & mask(width));
}

#endif // __BASE_CONDCODE_HH__