📄 reg_compare.c
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/*---------------------------------------------------------------------------+
| reg_compare.c |
| |
| Compare two floating point registers |
| |
| Copyright (C) 1992,1993,1994 |
| W. Metzenthen, 22 Parker St, Ormond, Vic 3163, |
| Australia. E-mail billm@vaxc.cc.monash.edu.au |
| |
| |
+---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------+
| 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"
int compare(FPU_REG const *b)
{
int diff;
if ( FPU_st0_ptr->tag | b->tag )
{
if ( FPU_st0_ptr->tag == TW_Zero )
{
if ( b->tag == TW_Zero ) return COMP_A_eq_B;
if ( b->tag == TW_Valid )
{
return ((b->sign == SIGN_POS) ? COMP_A_lt_B : COMP_A_gt_B)
#ifdef DENORM_OPERAND
| ((b->exp <= EXP_UNDER) ?
COMP_Denormal : 0)
#endif DENORM_OPERAND
;
}
}
else if ( b->tag == TW_Zero )
{
if ( FPU_st0_ptr->tag == TW_Valid )
{
return ((FPU_st0_ptr->sign == SIGN_POS) ? COMP_A_gt_B
: COMP_A_lt_B)
#ifdef DENORM_OPERAND
| ((FPU_st0_ptr->exp <= EXP_UNDER )
? COMP_Denormal : 0 )
#endif DENORM_OPERAND
;
}
}
if ( FPU_st0_ptr->tag == TW_Infinity )
{
if ( (b->tag == TW_Valid) || (b->tag == TW_Zero) )
{
return ((FPU_st0_ptr->sign == SIGN_POS) ? COMP_A_gt_B
: COMP_A_lt_B)
#ifdef DENORM_OPERAND
| (((b->tag == TW_Valid) && (b->exp <= EXP_UNDER)) ?
COMP_Denormal : 0 )
#endif DENORM_OPERAND
;
}
else if ( b->tag == TW_Infinity )
{
/* The 80486 book says that infinities can be equal! */
return (FPU_st0_ptr->sign == b->sign) ? COMP_A_eq_B :
((FPU_st0_ptr->sign == SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B);
}
/* Fall through to the NaN code */
}
else if ( b->tag == TW_Infinity )
{
if ( (FPU_st0_ptr->tag == TW_Valid) || (FPU_st0_ptr->tag == TW_Zero) )
{
return ((b->sign == SIGN_POS) ? COMP_A_lt_B : COMP_A_gt_B)
#ifdef DENORM_OPERAND
| (((FPU_st0_ptr->tag == TW_Valid)
&& (FPU_st0_ptr->exp <= EXP_UNDER)) ?
COMP_Denormal : 0)
#endif DENORM_OPERAND
;
}
/* Fall through to the NaN code */
}
/* The only possibility now should be that one of the arguments
is a NaN */
if ( (FPU_st0_ptr->tag == TW_NaN) || (b->tag == TW_NaN) )
{
if ( ((FPU_st0_ptr->tag == TW_NaN) && !(FPU_st0_ptr->sigh & 0x40000000))
|| ((b->tag == TW_NaN) && !(b->sigh & 0x40000000)) )
/* At least one arg is a signaling NaN */
return COMP_No_Comp | COMP_SNaN | COMP_NaN;
else
/* Neither is a signaling NaN */
return COMP_No_Comp | COMP_NaN;
}
EXCEPTION(EX_Invalid);
}
#ifdef PARANOID
if (!(FPU_st0_ptr->sigh & 0x80000000)) EXCEPTION(EX_Invalid);
if (!(b->sigh & 0x80000000)) EXCEPTION(EX_Invalid);
#endif PARANOID
if (FPU_st0_ptr->sign != b->sign)
{
return ((FPU_st0_ptr->sign == SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B)
#ifdef DENORM_OPERAND
|
( ((FPU_st0_ptr->exp <= EXP_UNDER) || (b->exp <= EXP_UNDER)) ?
COMP_Denormal : 0)
#endif DENORM_OPERAND
;
}
diff = FPU_st0_ptr->exp - b->exp;
if ( diff == 0 )
{
diff = FPU_st0_ptr->sigh - b->sigh; /* Works only if ms bits are
identical */
if ( diff == 0 )
{
diff = FPU_st0_ptr->sigl > b->sigl;
if ( diff == 0 )
diff = -(FPU_st0_ptr->sigl < b->sigl);
}
}
if ( diff > 0 )
{
return ((FPU_st0_ptr->sign == SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B)
#ifdef DENORM_OPERAND
|
( ((FPU_st0_ptr->exp <= EXP_UNDER) || (b->exp <= EXP_UNDER)) ?
COMP_Denormal : 0)
#endif DENORM_OPERAND
;
}
if ( diff < 0 )
{
return ((FPU_st0_ptr->sign == SIGN_POS) ? COMP_A_lt_B : COMP_A_gt_B)
#ifdef DENORM_OPERAND
|
( ((FPU_st0_ptr->exp <= EXP_UNDER) || (b->exp <= EXP_UNDER)) ?
COMP_Denormal : 0)
#endif DENORM_OPERAND
;
}
return COMP_A_eq_B
#ifdef DENORM_OPERAND
|
( ((FPU_st0_ptr->exp <= EXP_UNDER) || (b->exp <= EXP_UNDER)) ?
COMP_Denormal : 0)
#endif DENORM_OPERAND
;
}
/* This function requires that st(0) is not empty */
int compare_st_data(void)
{
int f, c;
c = compare(&FPU_loaded_data);
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();
}
return 0;
}
static int compare_st_st(int nr)
{
int f, c;
if ( !NOT_EMPTY_0 || !NOT_EMPTY(nr) )
{
setcc(SW_C3 | SW_C2 | SW_C0);
/* Stack fault */
EXCEPTION(EX_StackUnder);
return !(control_word & CW_Invalid);
}
c = compare(&st(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();
}
return 0;
}
static int compare_u_st_st(int nr)
{
int f, c;
if ( !NOT_EMPTY_0 || !NOT_EMPTY(nr) )
{
setcc(SW_C3 | SW_C2 | SW_C0);
/* Stack fault */
EXCEPTION(EX_StackUnder);
return !(control_word & CW_Invalid);
}
c = compare(&st(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();
}
return 0;
}
/*---------------------------------------------------------------------------*/
void fcom_st()
{
/* fcom st(i) */
compare_st_st(FPU_rm);
}
void fcompst()
{
/* fcomp st(i) */
if ( !compare_st_st(FPU_rm) )
pop();
}
void fcompp()
{
/* fcompp */
if (FPU_rm != 1)
{
FPU_illegal();
return;
}
if ( !compare_st_st(1) )
{
pop(); FPU_st0_ptr = &st(0);
pop();
}
}
void fucom_()
{
/* fucom st(i) */
compare_u_st_st(FPU_rm);
}
void fucomp()
{
/* fucomp st(i) */
if ( !compare_u_st_st(FPU_rm) )
pop();
}
void fucompp()
{
/* fucompp */
if (FPU_rm == 1)
{
if ( !compare_u_st_st(1) )
{
pop(); FPU_st0_ptr = &st(0);
pop();
}
}
else
FPU_illegal();
}
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