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|
/*---------------------------------------------------------------------------+
| fpu_etc.c |
| |
| Implement a few FPU instructions. |
| |
| Copyright (C) 1992,1993,1994,1997 |
| W. Metzenthen, 22 Parker St, Ormond, Vic 3163, |
| Australia. E-mail billm@suburbia.net |
| |
| |
+---------------------------------------------------------------------------*/
#include "fpu_system.h"
#include "exception.h"
#include "fpu_emu.h"
#include "status_w.h"
#include "reg_constant.h"
static void fchs(FPU_REG *st0_ptr, u_char st0tag)
{
if ( st0tag ^ TAG_Empty )
{
signbyte(st0_ptr) ^= SIGN_NEG;
clear_C1();
}
else
FPU_stack_underflow();
}
static void fabs(FPU_REG *st0_ptr, u_char st0tag)
{
if ( st0tag ^ TAG_Empty )
{
setpositive(st0_ptr);
clear_C1();
}
else
FPU_stack_underflow();
}
static void ftst_(FPU_REG *st0_ptr, u_char st0tag)
{
switch (st0tag)
{
case TAG_Zero:
setcc(SW_C3);
break;
case TAG_Valid:
if (getsign(st0_ptr) == SIGN_POS)
setcc(0);
else
setcc(SW_C0);
break;
case TAG_Special:
switch ( FPU_Special(st0_ptr) )
{
case TW_Denormal:
if (getsign(st0_ptr) == SIGN_POS)
setcc(0);
else
setcc(SW_C0);
if ( denormal_operand() < 0 )
{
#ifdef PECULIAR_486
/* This is weird! */
if (getsign(st0_ptr) == SIGN_POS)
setcc(SW_C3);
#endif /* PECULIAR_486 */
return;
}
break;
case TW_NaN:
setcc(SW_C0|SW_C2|SW_C3); /* Operand is not comparable */
EXCEPTION(EX_Invalid);
break;
case TW_Infinity:
if (getsign(st0_ptr) == SIGN_POS)
setcc(0);
else
setcc(SW_C0);
break;
default:
setcc(SW_C0|SW_C2|SW_C3); /* Operand is not comparable */
EXCEPTION(EX_INTERNAL|0x14);
break;
}
break;
case TAG_Empty:
setcc(SW_C0|SW_C2|SW_C3);
EXCEPTION(EX_StackUnder);
break;
}
}
static void fxam(FPU_REG *st0_ptr, u_char st0tag)
{
int c = 0;
switch (st0tag)
{
case TAG_Empty:
c = SW_C3|SW_C0;
break;
case TAG_Zero:
c = SW_C3;
break;
case TAG_Valid:
c = SW_C2;
break;
case TAG_Special:
switch ( FPU_Special(st0_ptr) )
{
case TW_Denormal:
c = SW_C2|SW_C3; /* Denormal */
break;
case TW_NaN:
/* We also use NaN for unsupported types. */
if ( (st0_ptr->sigh & 0x80000000) && (exponent(st0_ptr) == EXP_OVER) )
c = SW_C0;
break;
case TW_Infinity:
c = SW_C2|SW_C0;
break;
}
}
if ( getsign(st0_ptr) == SIGN_NEG )
c |= SW_C1;
setcc(c);
}
static FUNC_ST0 const fp_etc_table[] = {
fchs, fabs, (FUNC_ST0)FPU_illegal, (FUNC_ST0)FPU_illegal,
ftst_, fxam, (FUNC_ST0)FPU_illegal, (FUNC_ST0)FPU_illegal
};
void FPU_etc(void)
{
(fp_etc_table[FPU_rm])(&st(0), FPU_gettag0());
}
|
