/*---------------------------------------------------------------------------+
| reg_divide.c |
| |
| Divide one FPU_REG by another and put the result in a destination FPU_REG.|
| |
| Copyright (C) 1996 |
| W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia |
| E-mail billm@jacobi.maths.monash.edu.au |
| |
| Return value is the tag of the answer, or-ed with FPU_Exception if |
| one was raised, or -1 on internal error. |
| |
+---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------+
| The destination may be any FPU_REG, including one of the source FPU_REGs. |
+---------------------------------------------------------------------------*/
#include "exception.h"
#include "reg_constant.h"
#include "fpu_emu.h"
#include "fpu_system.h"
/*
Divide one register by another and put the result into a third register.
*/
int FPU_div(int flags, int rm, int control_w)
{
FPU_REG x, y;
FPU_REG const *a, *b, *st0_ptr, *st_ptr;
FPU_REG *dest;
u_char taga, tagb, signa, signb, sign, saved_sign;
int tag, deststnr;
if ( flags & DEST_RM )
deststnr = rm;
else
deststnr = 0;
if ( flags & REV )
{
b = &st(0);
st0_ptr = b;
tagb = FPU_gettag0();
if ( flags & LOADED )
{
a = (FPU_REG *)rm;
taga = flags & 0x0f;
}
else
{
a = &st(rm);
st_ptr = a;
taga = FPU_gettagi(rm);
}
}
else
{
a = &st(0);
st0_ptr = a;
taga = FPU_gettag0();
if ( flags & LOADED )
{
b = (FPU_REG *)rm;
tagb = flags & 0x0f;
}
else
{
b = &st(rm);
st_ptr = b;
tagb = FPU_gettagi(rm);
}
}
signa = getsign(a);
signb = getsign(b);
sign = signa ^ signb;
dest = &st(deststnr);
saved_sign = getsign(dest);
if ( !(taga | tagb) )
{
/* Both regs Valid, this should be the most common case. */
reg_copy(a, &x);
reg_copy(b, &y);
setpositive(&x);
setpositive(&y);
tag = FPU_u_div(&x, &y, dest, control_w, sign);
if ( tag < 0 )
return tag;
FPU_settagi(deststnr, tag);
return tag;
}
if ( taga == TAG_Special )
taga = FPU_Special(a);
if ( tagb == TAG_Special )
tagb = FPU_Special(b);
if ( ((taga == TAG_Valid) && (tagb == TW_Denormal))
|| ((taga == TW_Denormal) && (tagb == TAG_Valid))
|| ((taga == TW_Denormal) && (tagb == TW_Denormal)) )
{
if ( denormal_operand() < 0 )
return FPU_Exception;
FPU_to_exp16(a, &x);
FPU_to_exp16(b, &y);
tag = FPU_u_div(&x, &y, dest, control_w, sign);
if ( tag < 0 )
return tag;
FPU_settagi(deststnr, tag);
return tag;
}
else if ( (taga <= TW_Denormal) && (tagb <= TW_Denormal) )
{
if ( tagb != TAG_Zero )
{
/* Want to find Zero/Valid */
if ( tagb == TW_Denormal )
{
if ( denormal_operand() < 0 )
return FPU_Exception;
}
/* The result is zero. */
FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr);
setsign(dest, sign);
return TAG_Zero;
}
/* We have an exception condition, either 0/0 or Valid/Zero. */
if ( taga == TAG_Zero )
{
/* 0/0 */
return arith_invalid(deststnr);
}
/* Valid/Zero */
return FPU_divide_by_zero(deststnr, sign);
}
/* Must have infinities, NaNs, etc */
else if ( (taga == TW_NaN) || (tagb == TW_NaN) )
{
if ( flags & LOADED )
return real_2op_NaN((FPU_REG *)rm, flags & 0x0f, 0, st0_ptr);
if ( flags & DEST_RM )
{
int tag;
tag = FPU_gettag0();
if ( tag == TAG_Special )
tag = FPU_Special(st0_ptr);
return real_2op_NaN(st0_ptr, tag, rm, (flags & REV) ? st0_ptr : &st(rm));
}
else
{
int tag;
tag = FPU_gettagi(rm);
if ( tag == TAG_Special )
tag = FPU_Special(&st(rm));
return real_2op_NaN(&st(rm), tag, 0, (flags & REV) ? st0_ptr : &st(rm));
}
}
else if (taga == TW_Infinity)
{
if (tagb == TW_Infinity)
{
/* infinity/infinity */
return arith_invalid(deststnr);
}
else
{
/* tagb must be Valid or Zero */
if ( (tagb == TW_Denormal) && (denormal_operand() < 0) )
return FPU_Exception;
/* Infinity divided by Zero or Valid does
not raise and exception, but returns Infinity */
FPU_copy_to_regi(a, TAG_Special, deststnr);
setsign(dest, sign);
return taga;
}
}
else if (tagb == TW_Infinity)
{
if ( (taga == TW_Denormal) && (denormal_operand() < 0) )
return FPU_Exception;
/* The result is zero. */
FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr);
setsign(dest, sign);
return TAG_Zero;
}
#ifdef PARANOID
else
{
EXCEPTION(EX_INTERNAL|0x102);
return FPU_Exception;
}
#endif /* PARANOID */
return 0;
}
