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|
/*---------------------------------------------------------------------------+
| reg_compare.c |
| |
| Compare two floating point registers |
| |
| Copyright (C) 1992,1993,1994,1997 |
| W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia |
| E-mail billm@suburbia.net |
| |
| |
+---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------+
| compare() is the core FPU_REG comparison function |
+---------------------------------------------------------------------------*/
#include "fpu_system.h"
#include "exception.h"
#include "fpu_emu.h"
#include "control_w.h"
#include "status_w.h"
static int compare(FPU_REG const *b, int tagb)
{
int diff, exp0, expb;
u_char st0_tag;
FPU_REG *st0_ptr;
FPU_REG x, y;
u_char st0_sign, signb = getsign(b);
st0_ptr = &st(0);
st0_tag = FPU_gettag0();
st0_sign = getsign(st0_ptr);
if ( tagb == TAG_Special )
tagb = FPU_Special(b);
if ( st0_tag == TAG_Special )
st0_tag = FPU_Special(st0_ptr);
if ( ((st0_tag != TAG_Valid) && (st0_tag != TW_Denormal))
|| ((tagb != TAG_Valid) && (tagb != TW_Denormal)) )
{
if ( st0_tag == TAG_Zero )
{
if ( tagb == TAG_Zero ) return COMP_A_eq_B;
if ( tagb == TAG_Valid )
return ((signb == SIGN_POS) ? COMP_A_lt_B : COMP_A_gt_B);
if ( tagb == TW_Denormal )
return ((signb == SIGN_POS) ? COMP_A_lt_B : COMP_A_gt_B)
| COMP_Denormal;
}
else if ( tagb == TAG_Zero )
{
if ( st0_tag == TAG_Valid )
return ((st0_sign == SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B);
if ( st0_tag == TW_Denormal )
return ((st0_sign == SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B)
| COMP_Denormal;
}
if ( st0_tag == TW_Infinity )
{
if ( (tagb == TAG_Valid) || (tagb == TAG_Zero) )
return ((st0_sign == SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B);
else if ( tagb == TW_Denormal )
return ((st0_sign == SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B)
| COMP_Denormal;
else if ( tagb == TW_Infinity )
{
/* The 80486 book says that infinities can be equal! */
return (st0_sign == signb) ? COMP_A_eq_B :
((st0_sign == SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B);
}
/* Fall through to the NaN code */
}
else if ( tagb == TW_Infinity )
{
if ( (st0_tag == TAG_Valid) || (st0_tag == TAG_Zero) )
return ((signb == SIGN_POS) ? COMP_A_lt_B : COMP_A_gt_B);
if ( st0_tag == TW_Denormal )
return ((signb == SIGN_POS) ? COMP_A_lt_B : COMP_A_gt_B)
| COMP_Denormal;
/* Fall through to the NaN code */
}
/* The only possibility now should be that one of the arguments
is a NaN */
if ( (st0_tag == TW_NaN) || (tagb == TW_NaN) )
{
int signalling = 0, unsupported = 0;
if ( st0_tag == TW_NaN )
{
signalling = (st0_ptr->sigh & 0xc0000000) == 0x80000000;
unsupported = !((exponent(st0_ptr) == EXP_OVER)
&& (st0_ptr->sigh & 0x80000000));
}
if ( tagb == TW_NaN )
{
signalling |= (b->sigh & 0xc0000000) == 0x80000000;
unsupported |= !((exponent(b) == EXP_OVER)
&& (b->sigh & 0x80000000));
}
if ( signalling || unsupported )
return COMP_No_Comp | COMP_SNaN | COMP_NaN;
else
/* Neither is a signaling NaN */
return COMP_No_Comp | COMP_NaN;
}
EXCEPTION(EX_Invalid);
}
if (st0_sign != signb)
{
return ((st0_sign == SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B)
| ( ((st0_tag == TW_Denormal) || (tagb == TW_Denormal)) ?
COMP_Denormal : 0);
}
if ( (st0_tag == TW_Denormal) || (tagb == TW_Denormal) )
{
FPU_to_exp16(st0_ptr, &x);
FPU_to_exp16(b, &y);
st0_ptr = &x;
b = &y;
exp0 = exponent16(st0_ptr);
expb = exponent16(b);
}
else
{
exp0 = exponent(st0_ptr);
expb = exponent(b);
}
#ifdef PARANOID
if (!(st0_ptr->sigh & 0x80000000)) EXCEPTION(EX_Invalid);
if (!(b->sigh & 0x80000000)) EXCEPTION(EX_Invalid);
#endif PARANOID
diff = exp0 - expb;
if ( diff == 0 )
{
diff = st0_ptr->sigh - b->sigh; /* Works only if ms bits are
identical */
if ( diff == 0 )
{
diff = st0_ptr->sigl > b->sigl;
if ( diff == 0 )
diff = -(st0_ptr->sigl < b->sigl);
}
}
if ( diff > 0 )
{
return ((st0_sign == SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B)
| ( ((st0_tag == TW_Denormal) || (tagb == TW_Denormal)) ?
COMP_Denormal : 0);
}
if ( diff < 0 )
{
return ((st0_sign == SIGN_POS) ? COMP_A_lt_B : COMP_A_gt_B)
| ( ((st0_tag == TW_Denormal) || (tagb == TW_Denormal)) ?
COMP_Denormal : 0);
}
return COMP_A_eq_B
| ( ((st0_tag == TW_Denormal) || (tagb == TW_Denormal)) ?
COMP_Denormal : 0);
}
/* This function requires that st(0) is not empty */
int FPU_compare_st_data(FPU_REG const *loaded_data, u_char loaded_tag)
{
int f, c;
c = compare(loaded_data, loaded_tag);
if (c & COMP_NaN)
{
EXCEPTION(EX_Invalid);
f = SW_C3 | SW_C2 | SW_C0;
}
else
switch (c & 7)
{
case COMP_A_lt_B:
f = SW_C0;
break;
case COMP_A_eq_B:
f = SW_C3;
break;
case COMP_A_gt_B:
f = 0;
break;
case COMP_No_Comp:
f = SW_C3 | SW_C2 | SW_C0;
break;
#ifdef PARANOID
default:
EXCEPTION(EX_INTERNAL|0x121);
f = SW_C3 | SW_C2 | SW_C0;
break;
#endif PARANOID
}
setcc(f);
if (c & COMP_Denormal)
{
return denormal_operand() < 0;
}
return 0;
}
static int compare_st_st(int nr)
{
int f, c;
FPU_REG *st_ptr;
if ( !NOT_EMPTY(0) || !NOT_EMPTY(nr) )
{
setcc(SW_C3 | SW_C2 | SW_C0);
/* Stack fault */
EXCEPTION(EX_StackUnder);
return !(control_word & CW_Invalid);
}
st_ptr = &st(nr);
c = compare(st_ptr, FPU_gettagi(nr));
if (c & COMP_NaN)
{
setcc(SW_C3 | SW_C2 | SW_C0);
EXCEPTION(EX_Invalid);
return !(control_word & CW_Invalid);
}
else
switch (c & 7)
{
case COMP_A_lt_B:
f = SW_C0;
break;
case COMP_A_eq_B:
f = SW_C3;
break;
case COMP_A_gt_B:
f = 0;
break;
case COMP_No_Comp:
f = SW_C3 | SW_C2 | SW_C0;
break;
#ifdef PARANOID
default:
EXCEPTION(EX_INTERNAL|0x122);
f = SW_C3 | SW_C2 | SW_C0;
break;
#endif PARANOID
}
setcc(f);
if (c & COMP_Denormal)
{
return denormal_operand() < 0;
}
return 0;
}
static int compare_u_st_st(int nr)
{
int f, c;
FPU_REG *st_ptr;
if ( !NOT_EMPTY(0) || !NOT_EMPTY(nr) )
{
setcc(SW_C3 | SW_C2 | SW_C0);
/* Stack fault */
EXCEPTION(EX_StackUnder);
return !(control_word & CW_Invalid);
}
st_ptr = &st(nr);
c = compare(st_ptr, FPU_gettagi(nr));
if (c & COMP_NaN)
{
setcc(SW_C3 | SW_C2 | SW_C0);
if (c & COMP_SNaN) /* This is the only difference between
un-ordered and ordinary comparisons */
{
EXCEPTION(EX_Invalid);
return !(control_word & CW_Invalid);
}
return 0;
}
else
switch (c & 7)
{
case COMP_A_lt_B:
f = SW_C0;
break;
case COMP_A_eq_B:
f = SW_C3;
break;
case COMP_A_gt_B:
f = 0;
break;
case COMP_No_Comp:
f = SW_C3 | SW_C2 | SW_C0;
break;
#ifdef PARANOID
default:
EXCEPTION(EX_INTERNAL|0x123);
f = SW_C3 | SW_C2 | SW_C0;
break;
#endif PARANOID
}
setcc(f);
if (c & COMP_Denormal)
{
return denormal_operand() < 0;
}
return 0;
}
/*---------------------------------------------------------------------------*/
void fcom_st()
{
/* fcom st(i) */
compare_st_st(FPU_rm);
}
void fcompst()
{
/* fcomp st(i) */
if ( !compare_st_st(FPU_rm) )
FPU_pop();
}
void fcompp()
{
/* fcompp */
if (FPU_rm != 1)
{
FPU_illegal();
return;
}
if ( !compare_st_st(1) )
poppop();
}
void fucom_()
{
/* fucom st(i) */
compare_u_st_st(FPU_rm);
}
void fucomp()
{
/* fucomp st(i) */
if ( !compare_u_st_st(FPU_rm) )
FPU_pop();
}
void fucompp()
{
/* fucompp */
if (FPU_rm == 1)
{
if ( !compare_u_st_st(1) )
poppop();
}
else
FPU_illegal();
}
|
