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|
/************************************************************************
ST register functions
************************************************************************/
/*
remember that the OP ST bit is maintained in lastparity
*/
/*
setstat sets the ST_OP bit according to lastparity
It must be called before reading the ST register.
*/
static void setstat(void)
{
int i;
UINT8 a;
I.STATUS &= ~ ST_OP;
/* We set the parity bit. */
a = lastparity;
for (i=0; i<8; i++) /* 8 bits to test */
{
if (a & 1) /* If current bit is set */
I.STATUS ^= ST_OP; /* we toggle the ST_OP bit */
a >>= 1; /* Next bit. */
}
}
/*
getstat sets emulator's lastparity variable according to 9900's STATUS bits.
It must be called on interrupt return, or when, for some reason,
the emulated program sets the STATUS register directly.
*/
static void getstat(void)
{
#if (USE_ST_MASK)
I.STATUS &= ST_MASK; /* unused bits are forced to 0 */
#endif
if (I.STATUS & ST_OP)
lastparity = 1;
else
lastparity = 0;
#if HAS_MAPPING
I.cur_map = (I.STATUS & ST_MF) ? 1 : 0;
#endif
}
/*
A few words about the following functions.
A big portability issue is the behavior of the ">>" instruction with the sign bit, which has
not been normalised. Every compiler does whatever it thinks smartest.
My code assumed that when shifting right signed numbers, the operand is left-filled with a
copy of sign bit, and that when shifting unsigned variables, it is left-filled with 0s.
This is probably the most logical behaviour, and it is the behavior of CW PRO3 - most time
(the exception is that ">>=" instructions always copy the sign bit (!)). But some compilers
are bound to disagree.
So, I had to create special functions with predefined tables included, so that this code work
on every compiler. BUT this is a real slow-down.
So, you might have to include a few lines in assembly to make this work better.
Sorry about this, this problem is really unpleasant and absurd, but it is not my fault.
*/
static const UINT16 right_shift_mask_table[17] =
{
0xFFFF,
0x7FFF,
0x3FFF,
0x1FFF,
0x0FFF,
0x07FF,
0x03FF,
0x01FF,
0x00FF,
0x007F,
0x003F,
0x001F,
0x000F,
0x0007,
0x0003,
0x0001,
0x0000
};
static const UINT16 inverted_right_shift_mask_table[17] =
{
0x0000,
0x8000,
0xC000,
0xE000,
0xF000,
0xF800,
0xFC00,
0xFE00,
0xFF00,
0xFF80,
0xFFC0,
0xFFE0,
0xFFF0,
0xFFF8,
0xFFFC,
0xFFFE,
0xFFFF
};
INLINE UINT16 logical_right_shift(UINT16 val, int c)
{
return((val>>c) & right_shift_mask_table[c]);
}
INLINE INT16 arithmetic_right_shift(INT16 val, int c)
{
if (val < 0)
return((val>>c) | inverted_right_shift_mask_table[c]);
else
return((val>>c) & right_shift_mask_table[c]);
}
/*
Set lae
*/
INLINE void setst_lae(INT16 val)
{
I.STATUS &= ~ (ST_LGT | ST_AGT | ST_EQ);
if (val > 0)
I.STATUS |= (ST_LGT | ST_AGT);
else if (val < 0)
I.STATUS |= ST_LGT;
else
I.STATUS |= ST_EQ;
}
/*
Set laep (BYTE)
*/
INLINE void setst_byte_laep(INT8 val)
{
I.STATUS &= ~ (ST_LGT | ST_AGT | ST_EQ);
if (val > 0)
I.STATUS |= (ST_LGT | ST_AGT);
else if (val < 0)
I.STATUS |= ST_LGT;
else
I.STATUS |= ST_EQ;
lastparity = val;
}
/*
For COC, CZC, and TB
*/
INLINE void setst_e(UINT16 val, UINT16 to)
{
if (val == to)
I.STATUS |= ST_EQ;
else
I.STATUS &= ~ ST_EQ;
}
/*
For CI, C, CB
*/
INLINE void setst_c_lae(UINT16 to, UINT16 val)
{
I.STATUS &= ~ (ST_LGT | ST_AGT | ST_EQ);
if (val == to)
I.STATUS |= ST_EQ;
else
{
if ( ((INT16) val) > ((INT16) to) )
I.STATUS |= ST_AGT;
if ( ((UINT16) val) > ((UINT16) to) )
I.STATUS |= ST_LGT;
}
}
/*
Set laeco for add
*/
INLINE INT16 setst_add_laeco(int a, int b)
{
UINT32 res;
INT16 res2;
I.STATUS &= ~ (ST_LGT | ST_AGT | ST_EQ | ST_C | ST_OV);
res = (a & 0xffff) + (b & 0xffff);
if (res & 0x10000)
I.STATUS |= ST_C;
if ((res ^ b) & (res ^ a) & 0x8000)
I.STATUS |= ST_OV;
#if (TMS99XX_MODEL == TMS9940_ID) || (TMS99XX_MODEL == TMS9985_ID)
if (((a & b) | ((a | b) & ~ res)) & 0x0800)
I.STATUS |= ST_DC;
#endif
res2 = (INT16) res;
if (res2 > 0)
I.STATUS |= ST_LGT | ST_AGT;
else if (res2 < 0)
I.STATUS |= ST_LGT;
else
I.STATUS |= ST_EQ;
return res2;
}
/*
Set laeco for subtract
*/
INLINE INT16 setst_sub_laeco(int a, int b)
{
UINT32 res;
INT16 res2;
I.STATUS &= ~ (ST_LGT | ST_AGT | ST_EQ | ST_C | ST_OV);
res = (a & 0xffff) - (b & 0xffff);
if (! (res & 0x10000))
I.STATUS |= ST_C;
if ((a ^ b) & (a ^ res) & 0x8000)
I.STATUS |= ST_OV;
#if (TMS99XX_MODEL == TMS9940_ID) || (TMS99XX_MODEL == TMS9985_ID)
if (((a & ~ b) | ((a | ~ b) & ~ res)) & 0x0800)
I.STATUS |= ST_DC;
#endif
res2 = (INT16) res;
if (res2 > 0)
I.STATUS |= ST_LGT | ST_AGT;
else if (res2 < 0)
I.STATUS |= ST_LGT;
else
I.STATUS |= ST_EQ;
return res2;
}
/*
Set laecop for add (BYTE)
*/
INLINE INT8 setst_addbyte_laecop(int a, int b)
{
unsigned int res;
INT8 res2;
I.STATUS &= ~ (ST_LGT | ST_AGT | ST_EQ | ST_C | ST_OV | ST_OP);
res = (a & 0xff) + (b & 0xff);
if (res & 0x100)
I.STATUS |= ST_C;
if ((res ^ b) & (res ^ a) & 0x80)
I.STATUS |= ST_OV;
#if (TMS99XX_MODEL == TMS9940_ID) || (TMS99XX_MODEL == TMS9985_ID)
if (((a & b) | ((a | b) & ~ res)) & 0x08)
I.STATUS |= ST_DC;
#endif
res2 = (INT8) res;
if (res2 > 0)
I.STATUS |= ST_LGT | ST_AGT;
else if (res2 < 0)
I.STATUS |= ST_LGT;
else
I.STATUS |= ST_EQ;
lastparity = res2;
return res2;
}
/*
Set laecop for subtract (BYTE)
*/
INLINE INT8 setst_subbyte_laecop(int a, int b)
{
unsigned int res;
INT8 res2;
I.STATUS &= ~ (ST_LGT | ST_AGT | ST_EQ | ST_C | ST_OV | ST_OP);
res = (a & 0xff) - (b & 0xff);
if (! (res & 0x100))
I.STATUS |= ST_C;
if ((a ^ b) & (a ^ res) & 0x80)
I.STATUS |= ST_OV;
#if (TMS99XX_MODEL == TMS9940_ID) || (TMS99XX_MODEL == TMS9985_ID)
if (((a & ~ b) | ((a | ~ b) & ~ res)) & 0x08)
I.STATUS |= ST_DC;
#endif
res2 = (INT8) res;
if (res2 > 0)
I.STATUS |= ST_LGT | ST_AGT;
else if (res2 < 0)
I.STATUS |= ST_LGT;
else
I.STATUS |= ST_EQ;
lastparity = res2;
return res2;
}
/*
For NEG
*/
INLINE void setst_laeo(INT16 val)
{
I.STATUS &= ~ (ST_LGT | ST_AGT | ST_EQ | ST_OV);
if (val > 0)
I.STATUS |= ST_LGT | ST_AGT;
else if (val < 0)
{
I.STATUS |= ST_LGT;
if (((UINT16) val) == 0x8000)
I.STATUS |= ST_OV;
}
else
I.STATUS |= ST_EQ;
}
/*
Meat of SRA
*/
INLINE UINT16 setst_sra_laec(INT16 a, UINT16 c)
{
I.STATUS &= ~ (ST_LGT | ST_AGT | ST_EQ | ST_C);
if (c != 0)
{
a = arithmetic_right_shift(a, c-1);
if (a & 1) // The carry bit equals the last bit that is shifted out
I.STATUS |= ST_C;
a = arithmetic_right_shift(a, 1);
}
if (a > 0)
I.STATUS |= ST_LGT | ST_AGT;
else if (a < 0)
I.STATUS |= ST_LGT;
else
I.STATUS |= ST_EQ;
return a;
}
/*
Meat of SRL. Same algorithm as SRA, except that we fills in with 0s.
*/
INLINE UINT16 setst_srl_laec(UINT16 a,UINT16 c)
{
I.STATUS &= ~ (ST_LGT | ST_AGT | ST_EQ | ST_C);
if (c != 0)
{
a = logical_right_shift(a, c-1);
if (a & 1)
I.STATUS |= ST_C;
a = logical_right_shift(a, 1);
}
if (((INT16) a) > 0)
I.STATUS |= ST_LGT | ST_AGT;
else if (((INT16) a) < 0)
I.STATUS |= ST_LGT;
else
I.STATUS |= ST_EQ;
return a;
}
//
// Meat of SRC
//
INLINE UINT16 setst_src_laec(UINT16 a,UINT16 c)
{
I.STATUS &= ~ (ST_LGT | ST_AGT | ST_EQ | ST_C);
if (c != 0)
{
a = logical_right_shift(a, c) | (a << (16-c));
if (a & 0x8000) // The carry bit equals the last bit that is shifted out
I.STATUS |= ST_C;
}
if (((INT16) a) > 0)
I.STATUS |= ST_LGT | ST_AGT;
else if (((INT16) a) < 0)
I.STATUS |= ST_LGT;
else
I.STATUS |= ST_EQ;
return a;
}
//
// Meat of SLA
//
INLINE UINT16 setst_sla_laeco(UINT16 a, UINT16 c)
{
I.STATUS &= ~ (ST_LGT | ST_AGT | ST_EQ | ST_C | ST_OV);
if (c != 0)
{
{
register UINT16 mask;
register UINT16 ousted_bits;
mask = 0xFFFF << (16-c-1);
ousted_bits = a & mask;
if (ousted_bits) // If ousted_bits is neither all 0s
if (ousted_bits ^ mask) // nor all 1s,
I.STATUS |= ST_OV; // we set overflow
}
a <<= c-1;
if (a & 0x8000) // The carry bit equals the last bit that is shifted out
I.STATUS |= ST_C;
a <<= 1;
}
if (((INT16) a) > 0)
I.STATUS |= ST_LGT | ST_AGT;
else if (((INT16) a) < 0)
I.STATUS |= ST_LGT;
else
I.STATUS |= ST_EQ;
return a;
}
/***********************************************************************/
|