prim_ops.c

u-boot 源代码

/****************************************************************************
*
*			Realmode X86 Emulator Library
*
*		Copyright (C) 1991-2004 SciTech Software, Inc.
*		     Copyright (C) David Mosberger-Tang
*		       Copyright (C) 1999 Egbert Eich
*
*  ========================================================================
*
*  Permission to use, copy, modify, distribute, and sell this software and
*  its documentation for any purpose is hereby granted without fee,
*  provided that the above copyright notice appear in all copies and that
*  both that copyright notice and this permission notice appear in
*  supporting documentation, and that the name of the authors not be used
*  in advertising or publicity pertaining to distribution of the software
*  without specific, written prior permission.	The authors makes no
*  representations about the suitability of this software for any purpose.
*  It is provided "as is" without express or implied warranty.
*
*  THE AUTHORS DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
*  INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
*  EVENT SHALL THE AUTHORS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
*  CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF
*  USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
*  OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
*  PERFORMANCE OF THIS SOFTWARE.
*
*  ========================================================================
*
* Language:	ANSI C
* Environment:	Any
* Developer:	Kendall Bennett
*
* Description:	This file contains the code to implement the primitive
*		machine operations used by the emulation code in ops.c
*
* Carry Chain Calculation
*
* This represents a somewhat expensive calculation which is
* apparently required to emulate the setting of the OF343364 and AF flag.
* The latter is not so important, but the former is.  The overflow
* flag is the XOR of the top two bits of the carry chain for an
* addition (similar for subtraction).  Since we do not want to
* simulate the addition in a bitwise manner, we try to calculate the
* carry chain given the two operands and the result.
*
* So, given the following table, which represents the addition of two
* bits, we can derive a formula for the carry chain.
*
* a   b	  cin	r     cout
* 0   0	  0	0     0
* 0   0	  1	1     0
* 0   1	  0	1     0
* 0   1	  1	0     1
* 1   0	  0	1     0
* 1   0	  1	0     1
* 1   1	  0	0     1
* 1   1	  1	1     1
*
* Construction of table for cout:
*
* ab
* r  \	00   01	  11  10
* |------------------
* 0  |	 0    1	   1   1
* 1  |	 0    0	   1   0
*
* By inspection, one gets:  cc = ab +  r'(a + b)
*
* That represents alot of operations, but NO CHOICE....
*
* Borrow Chain Calculation.
*
* The following table represents the subtraction of two bits, from
* which we can derive a formula for the borrow chain.
*
* a   b	  bin	r     bout
* 0   0	  0	0     0
* 0   0	  1	1     1
* 0   1	  0	1     1
* 0   1	  1	0     1
* 1   0	  0	1     0
* 1   0	  1	0     0
* 1   1	  0	0     0
* 1   1	  1	1     1
*
* Construction of table for cout:
*
* ab
* r  \	00   01	  11  10
* |------------------
* 0  |	 0    1	   0   0
* 1  |	 1    1	   1   0
*
* By inspection, one gets:  bc = a'b +	r(a' + b)
*
****************************************************************************/

#include <common.h>

#define PRIM_OPS_NO_REDEFINE_ASM

#if defined(CONFIG_BIOSEMU)

#include "x86emu/x86emui.h"

/*------------------------- Global Variables ------------------------------*/

static u32 x86emu_parity_tab[8] =
{
    0x96696996,
    0x69969669,
    0x69969669,
    0x96696996,
    0x69969669,
    0x96696996,
    0x96696996,
    0x69969669,
};

#define PARITY(x)   (((x86emu_parity_tab[(x) / 32] >> ((x) % 32)) & 1) == 0)
#define XOR2(x)	    (((x) ^ ((x)>>1)) & 0x1)
/*----------------------------- Implementation ----------------------------*/
int abs(int v)
{
	return (v>0)?v:-v;
}

/*----------------------------- Implementation ----------------------------*/


/*--------- Side effects helper functions -------*/

/****************************************************************************
REMARKS:
implements side efects for byte operations that don't overflow
****************************************************************************/

static void set_parity_flag(u32 res)
{
    CONDITIONAL_SET_FLAG(PARITY(res & 0xFF), F_PF);
}

static void set_szp_flags_8(u8 res)
{
    CONDITIONAL_SET_FLAG(res & 0x80, F_SF);
    CONDITIONAL_SET_FLAG(res == 0, F_ZF);
    set_parity_flag(res);
}

static void set_szp_flags_16(u16 res)
{
    CONDITIONAL_SET_FLAG(res & 0x8000, F_SF);
    CONDITIONAL_SET_FLAG(res == 0, F_ZF);
    set_parity_flag(res);
}

static void set_szp_flags_32(u32 res)
{
    CONDITIONAL_SET_FLAG(res & 0x80000000, F_SF);
    CONDITIONAL_SET_FLAG(res == 0, F_ZF);
    set_parity_flag(res);
}

static void no_carry_byte_side_eff(u8 res)
{
    CLEAR_FLAG(F_OF);
    CLEAR_FLAG(F_CF);
    CLEAR_FLAG(F_AF);
    set_szp_flags_8(res);
}

static void no_carry_word_side_eff(u16 res)
{
    CLEAR_FLAG(F_OF);
    CLEAR_FLAG(F_CF);
    CLEAR_FLAG(F_AF);
    set_szp_flags_16(res);
}

static void no_carry_long_side_eff(u32 res)
{
    CLEAR_FLAG(F_OF);
    CLEAR_FLAG(F_CF);
    CLEAR_FLAG(F_AF);
    set_szp_flags_32(res);
}

static void calc_carry_chain(int bits, u32 d, u32 s, u32 res, int set_carry)
{
    u32 cc;

    cc = (s & d) | ((~res) & (s | d));
    CONDITIONAL_SET_FLAG(XOR2(cc >> (bits - 2)), F_OF);
    CONDITIONAL_SET_FLAG(cc & 0x8, F_AF);
    if (set_carry) {
	CONDITIONAL_SET_FLAG(res & (1 << bits), F_CF);
    }
}

static void calc_borrow_chain(int bits, u32 d, u32 s, u32 res, int set_carry)
{
    u32 bc;

    bc = (res & (~d | s)) | (~d & s);
    CONDITIONAL_SET_FLAG(XOR2(bc >> (bits - 2)), F_OF);
    CONDITIONAL_SET_FLAG(bc & 0x8, F_AF);
    if (set_carry) {
	CONDITIONAL_SET_FLAG(bc & (1 << (bits - 1)), F_CF);
    }
}

/****************************************************************************
REMARKS:
Implements the AAA instruction and side effects.
****************************************************************************/
u16 aaa_word(u16 d)
{
    u16 res;
    if ((d & 0xf) > 0x9 || ACCESS_FLAG(F_AF)) {
	d += 0x6;
	d += 0x100;
	SET_FLAG(F_AF);
	SET_FLAG(F_CF);
    } else {
	CLEAR_FLAG(F_CF);
	CLEAR_FLAG(F_AF);
    }
    res = (u16)(d & 0xFF0F);
    set_szp_flags_16(res);
    return res;
}

/****************************************************************************
REMARKS:
Implements the AAA instruction and side effects.
****************************************************************************/
u16 aas_word(u16 d)
{
    u16 res;
    if ((d & 0xf) > 0x9 || ACCESS_FLAG(F_AF)) {
	d -= 0x6;
	d -= 0x100;
	SET_FLAG(F_AF);
	SET_FLAG(F_CF);
    } else {
	CLEAR_FLAG(F_CF);
	CLEAR_FLAG(F_AF);
    }
    res = (u16)(d & 0xFF0F);
    set_szp_flags_16(res);
    return res;
}

/****************************************************************************
REMARKS:
Implements the AAD instruction and side effects.
****************************************************************************/
u16 aad_word(u16 d)
{
    u16 l;
    u8 hb, lb;

    hb = (u8)((d >> 8) & 0xff);
    lb = (u8)((d & 0xff));
    l = (u16)((lb + 10 * hb) & 0xFF);

    no_carry_byte_side_eff(l & 0xFF);
    return l;
}

/****************************************************************************
REMARKS:
Implements the AAM instruction and side effects.
****************************************************************************/
u16 aam_word(u8 d)
{
    u16 h, l;

    h = (u16)(d / 10);
    l = (u16)(d % 10);
    l |= (u16)(h << 8);

    no_carry_byte_side_eff(l & 0xFF);
    return l;
}

/****************************************************************************
REMARKS:
Implements the ADC instruction and side effects.
****************************************************************************/
u8 adc_byte(u8 d, u8 s)
{
    u32 res;   /* all operands in native machine order */

    res = d + s;
    if (ACCESS_FLAG(F_CF)) res++;

    set_szp_flags_8(res);
    calc_carry_chain(8,s,d,res,1);

    return (u8)res;
}

/****************************************************************************
REMARKS:
Implements the ADC instruction and side effects.
****************************************************************************/
u16 adc_word(u16 d, u16 s)
{
    u32 res;   /* all operands in native machine order */

    res = d + s;
    if (ACCESS_FLAG(F_CF))
	res++;

    set_szp_flags_16((u16)res);
    calc_carry_chain(16,s,d,res,1);

    return (u16)res;
}

/****************************************************************************
REMARKS:
Implements the ADC instruction and side effects.
****************************************************************************/
u32 adc_long(u32 d, u32 s)
{
    u32 lo;    /* all operands in native machine order */
    u32 hi;
    u32 res;

    lo = (d & 0xFFFF) + (s & 0xFFFF);
    res = d + s;

    if (ACCESS_FLAG(F_CF)) {
	lo++;
	res++;
    }

    hi = (lo >> 16) + (d >> 16) + (s >> 16);

    set_szp_flags_32(res);
    calc_carry_chain(32,s,d,res,0);

    CONDITIONAL_SET_FLAG(hi & 0x10000, F_CF);

    return res;
}

/****************************************************************************
REMARKS:
Implements the ADD instruction and side effects.
****************************************************************************/
u8 add_byte(u8 d, u8 s)
{
    u32 res;   /* all operands in native machine order */

    res = d + s;
    set_szp_flags_8((u8)res);
    calc_carry_chain(8,s,d,res,1);

    return (u8)res;
}

/****************************************************************************
REMARKS:
Implements the ADD instruction and side effects.
****************************************************************************/
u16 add_word(u16 d, u16 s)
{
    u32 res;   /* all operands in native machine order */

    res = d + s;
    set_szp_flags_16((u16)res);
    calc_carry_chain(16,s,d,res,1);

    return (u16)res;
}

/****************************************************************************
REMARKS:
Implements the ADD instruction and side effects.
****************************************************************************/
u32 add_long(u32 d, u32 s)
{
    u32 res;

    res = d + s;
    set_szp_flags_32(res);
    calc_carry_chain(32,s,d,res,0);

    CONDITIONAL_SET_FLAG(res < d || res < s, F_CF);

    return res;
}

/****************************************************************************
REMARKS:
Implements the AND instruction and side effects.
****************************************************************************/
u8 and_byte(u8 d, u8 s)
{
    u8 res;    /* all operands in native machine order */

    res = d & s;

    no_carry_byte_side_eff(res);
    return res;
}

/****************************************************************************
REMARKS:
Implements the AND instruction and side effects.
****************************************************************************/
u16 and_word(u16 d, u16 s)
{
    u16 res;   /* all operands in native machine order */

    res = d & s;

    no_carry_word_side_eff(res);
    return res;
}

/****************************************************************************
REMARKS:
Implements the AND instruction and side effects.
****************************************************************************/
u32 and_long(u32 d, u32 s)
{
    u32 res;   /* all operands in native machine order */

    res = d & s;
    no_carry_long_side_eff(res);
    return res;
}

/****************************************************************************
REMARKS:
Implements the CMP instruction and side effects.
****************************************************************************/
u8 cmp_byte(u8 d, u8 s)
{
    u32 res;   /* all operands in native machine order */

    res = d - s;
    set_szp_flags_8((u8)res);
    calc_borrow_chain(8, d, s, res, 1);

    return d;
}

/****************************************************************************
REMARKS:
Implements the CMP instruction and side effects.
****************************************************************************/
u16 cmp_word(u16 d, u16 s)
{
    u32 res;   /* all operands in native machine order */

    res = d - s;
    set_szp_flags_16((u16)res);
    calc_borrow_chain(16, d, s, res, 1);

    return d;
}

/****************************************************************************
REMARKS:
Implements the CMP instruction and side effects.
****************************************************************************/
u32 cmp_long(u32 d, u32 s)
{
    u32 res;   /* all operands in native machine order */

    res = d - s;
    set_szp_flags_32(res);
    calc_borrow_chain(32, d, s, res, 1);

    return d;
}

/****************************************************************************
REMARKS:
Implements the DAA instruction and side effects.
****************************************************************************/
u8 daa_byte(u8 d)
{
    u32 res = d;