mirror of
https://github.com/torvalds/linux.git
synced 2024-11-12 07:01:57 +00:00
1da177e4c3
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
375 lines
9.1 KiB
C
375 lines
9.1 KiB
C
/*---------------------------------------------------------------------------+
|
|
| reg_add_sub.c |
|
|
| |
|
|
| Functions to add or subtract two registers and put the result in a third. |
|
|
| |
|
|
| Copyright (C) 1992,1993,1997 |
|
|
| W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia |
|
|
| E-mail billm@suburbia.net |
|
|
| |
|
|
| |
|
|
+---------------------------------------------------------------------------*/
|
|
|
|
/*---------------------------------------------------------------------------+
|
|
| For each function, the destination may be any FPU_REG, including one of |
|
|
| the source FPU_REGs. |
|
|
| Each function returns 0 if the answer is o.k., otherwise a non-zero |
|
|
| value is returned, indicating either an exception condition or an |
|
|
| internal error. |
|
|
+---------------------------------------------------------------------------*/
|
|
|
|
#include "exception.h"
|
|
#include "reg_constant.h"
|
|
#include "fpu_emu.h"
|
|
#include "control_w.h"
|
|
#include "fpu_system.h"
|
|
|
|
static
|
|
int add_sub_specials(FPU_REG const *a, u_char taga, u_char signa,
|
|
FPU_REG const *b, u_char tagb, u_char signb,
|
|
FPU_REG *dest, int deststnr, int control_w);
|
|
|
|
/*
|
|
Operates on st(0) and st(n), or on st(0) and temporary data.
|
|
The destination must be one of the source st(x).
|
|
*/
|
|
int FPU_add(FPU_REG const *b, u_char tagb, int deststnr, int control_w)
|
|
{
|
|
FPU_REG *a = &st(0);
|
|
FPU_REG *dest = &st(deststnr);
|
|
u_char signb = getsign(b);
|
|
u_char taga = FPU_gettag0();
|
|
u_char signa = getsign(a);
|
|
u_char saved_sign = getsign(dest);
|
|
int diff, tag, expa, expb;
|
|
|
|
if ( !(taga | tagb) )
|
|
{
|
|
expa = exponent(a);
|
|
expb = exponent(b);
|
|
|
|
valid_add:
|
|
/* Both registers are valid */
|
|
if (!(signa ^ signb))
|
|
{
|
|
/* signs are the same */
|
|
tag = FPU_u_add(a, b, dest, control_w, signa, expa, expb);
|
|
}
|
|
else
|
|
{
|
|
/* The signs are different, so do a subtraction */
|
|
diff = expa - expb;
|
|
if (!diff)
|
|
{
|
|
diff = a->sigh - b->sigh; /* This works only if the ms bits
|
|
are identical. */
|
|
if (!diff)
|
|
{
|
|
diff = a->sigl > b->sigl;
|
|
if (!diff)
|
|
diff = -(a->sigl < b->sigl);
|
|
}
|
|
}
|
|
|
|
if (diff > 0)
|
|
{
|
|
tag = FPU_u_sub(a, b, dest, control_w, signa, expa, expb);
|
|
}
|
|
else if ( diff < 0 )
|
|
{
|
|
tag = FPU_u_sub(b, a, dest, control_w, signb, expb, expa);
|
|
}
|
|
else
|
|
{
|
|
FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr);
|
|
/* sign depends upon rounding mode */
|
|
setsign(dest, ((control_w & CW_RC) != RC_DOWN)
|
|
? SIGN_POS : SIGN_NEG);
|
|
return TAG_Zero;
|
|
}
|
|
}
|
|
|
|
if ( tag < 0 )
|
|
{
|
|
setsign(dest, saved_sign);
|
|
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)) )
|
|
{
|
|
FPU_REG x, y;
|
|
|
|
if ( denormal_operand() < 0 )
|
|
return FPU_Exception;
|
|
|
|
FPU_to_exp16(a, &x);
|
|
FPU_to_exp16(b, &y);
|
|
a = &x;
|
|
b = &y;
|
|
expa = exponent16(a);
|
|
expb = exponent16(b);
|
|
goto valid_add;
|
|
}
|
|
|
|
if ( (taga == TW_NaN) || (tagb == TW_NaN) )
|
|
{
|
|
if ( deststnr == 0 )
|
|
return real_2op_NaN(b, tagb, deststnr, a);
|
|
else
|
|
return real_2op_NaN(a, taga, deststnr, a);
|
|
}
|
|
|
|
return add_sub_specials(a, taga, signa, b, tagb, signb,
|
|
dest, deststnr, control_w);
|
|
}
|
|
|
|
|
|
/* Subtract b from a. (a-b) -> dest */
|
|
int FPU_sub(int flags, int rm, int control_w)
|
|
{
|
|
FPU_REG const *a, *b;
|
|
FPU_REG *dest;
|
|
u_char taga, tagb, signa, signb, saved_sign, sign;
|
|
int diff, tag = 0, expa, expb, deststnr;
|
|
|
|
a = &st(0);
|
|
taga = FPU_gettag0();
|
|
|
|
deststnr = 0;
|
|
if ( flags & LOADED )
|
|
{
|
|
b = (FPU_REG *)rm;
|
|
tagb = flags & 0x0f;
|
|
}
|
|
else
|
|
{
|
|
b = &st(rm);
|
|
tagb = FPU_gettagi(rm);
|
|
|
|
if ( flags & DEST_RM )
|
|
deststnr = rm;
|
|
}
|
|
|
|
signa = getsign(a);
|
|
signb = getsign(b);
|
|
|
|
if ( flags & REV )
|
|
{
|
|
signa ^= SIGN_NEG;
|
|
signb ^= SIGN_NEG;
|
|
}
|
|
|
|
dest = &st(deststnr);
|
|
saved_sign = getsign(dest);
|
|
|
|
if ( !(taga | tagb) )
|
|
{
|
|
expa = exponent(a);
|
|
expb = exponent(b);
|
|
|
|
valid_subtract:
|
|
/* Both registers are valid */
|
|
|
|
diff = expa - expb;
|
|
|
|
if (!diff)
|
|
{
|
|
diff = a->sigh - b->sigh; /* Works only if ms bits are identical */
|
|
if (!diff)
|
|
{
|
|
diff = a->sigl > b->sigl;
|
|
if (!diff)
|
|
diff = -(a->sigl < b->sigl);
|
|
}
|
|
}
|
|
|
|
switch ( (((int)signa)*2 + signb) / SIGN_NEG )
|
|
{
|
|
case 0: /* P - P */
|
|
case 3: /* N - N */
|
|
if (diff > 0)
|
|
{
|
|
/* |a| > |b| */
|
|
tag = FPU_u_sub(a, b, dest, control_w, signa, expa, expb);
|
|
}
|
|
else if ( diff == 0 )
|
|
{
|
|
FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr);
|
|
|
|
/* sign depends upon rounding mode */
|
|
setsign(dest, ((control_w & CW_RC) != RC_DOWN)
|
|
? SIGN_POS : SIGN_NEG);
|
|
return TAG_Zero;
|
|
}
|
|
else
|
|
{
|
|
sign = signa ^ SIGN_NEG;
|
|
tag = FPU_u_sub(b, a, dest, control_w, sign, expb, expa);
|
|
}
|
|
break;
|
|
case 1: /* P - N */
|
|
tag = FPU_u_add(a, b, dest, control_w, SIGN_POS, expa, expb);
|
|
break;
|
|
case 2: /* N - P */
|
|
tag = FPU_u_add(a, b, dest, control_w, SIGN_NEG, expa, expb);
|
|
break;
|
|
#ifdef PARANOID
|
|
default:
|
|
EXCEPTION(EX_INTERNAL|0x111);
|
|
return -1;
|
|
#endif
|
|
}
|
|
if ( tag < 0 )
|
|
{
|
|
setsign(dest, saved_sign);
|
|
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)) )
|
|
{
|
|
FPU_REG x, y;
|
|
|
|
if ( denormal_operand() < 0 )
|
|
return FPU_Exception;
|
|
|
|
FPU_to_exp16(a, &x);
|
|
FPU_to_exp16(b, &y);
|
|
a = &x;
|
|
b = &y;
|
|
expa = exponent16(a);
|
|
expb = exponent16(b);
|
|
|
|
goto valid_subtract;
|
|
}
|
|
|
|
if ( (taga == TW_NaN) || (tagb == TW_NaN) )
|
|
{
|
|
FPU_REG const *d1, *d2;
|
|
if ( flags & REV )
|
|
{
|
|
d1 = b;
|
|
d2 = a;
|
|
}
|
|
else
|
|
{
|
|
d1 = a;
|
|
d2 = b;
|
|
}
|
|
if ( flags & LOADED )
|
|
return real_2op_NaN(b, tagb, deststnr, d1);
|
|
if ( flags & DEST_RM )
|
|
return real_2op_NaN(a, taga, deststnr, d2);
|
|
else
|
|
return real_2op_NaN(b, tagb, deststnr, d2);
|
|
}
|
|
|
|
return add_sub_specials(a, taga, signa, b, tagb, signb ^ SIGN_NEG,
|
|
dest, deststnr, control_w);
|
|
}
|
|
|
|
|
|
static
|
|
int add_sub_specials(FPU_REG const *a, u_char taga, u_char signa,
|
|
FPU_REG const *b, u_char tagb, u_char signb,
|
|
FPU_REG *dest, int deststnr, int control_w)
|
|
{
|
|
if ( ((taga == TW_Denormal) || (tagb == TW_Denormal))
|
|
&& (denormal_operand() < 0) )
|
|
return FPU_Exception;
|
|
|
|
if (taga == TAG_Zero)
|
|
{
|
|
if (tagb == TAG_Zero)
|
|
{
|
|
/* Both are zero, result will be zero. */
|
|
u_char different_signs = signa ^ signb;
|
|
|
|
FPU_copy_to_regi(a, TAG_Zero, deststnr);
|
|
if ( different_signs )
|
|
{
|
|
/* Signs are different. */
|
|
/* Sign of answer depends upon rounding mode. */
|
|
setsign(dest, ((control_w & CW_RC) != RC_DOWN)
|
|
? SIGN_POS : SIGN_NEG);
|
|
}
|
|
else
|
|
setsign(dest, signa); /* signa may differ from the sign of a. */
|
|
return TAG_Zero;
|
|
}
|
|
else
|
|
{
|
|
reg_copy(b, dest);
|
|
if ( (tagb == TW_Denormal) && (b->sigh & 0x80000000) )
|
|
{
|
|
/* A pseudoDenormal, convert it. */
|
|
addexponent(dest, 1);
|
|
tagb = TAG_Valid;
|
|
}
|
|
else if ( tagb > TAG_Empty )
|
|
tagb = TAG_Special;
|
|
setsign(dest, signb); /* signb may differ from the sign of b. */
|
|
FPU_settagi(deststnr, tagb);
|
|
return tagb;
|
|
}
|
|
}
|
|
else if (tagb == TAG_Zero)
|
|
{
|
|
reg_copy(a, dest);
|
|
if ( (taga == TW_Denormal) && (a->sigh & 0x80000000) )
|
|
{
|
|
/* A pseudoDenormal */
|
|
addexponent(dest, 1);
|
|
taga = TAG_Valid;
|
|
}
|
|
else if ( taga > TAG_Empty )
|
|
taga = TAG_Special;
|
|
setsign(dest, signa); /* signa may differ from the sign of a. */
|
|
FPU_settagi(deststnr, taga);
|
|
return taga;
|
|
}
|
|
else if (taga == TW_Infinity)
|
|
{
|
|
if ( (tagb != TW_Infinity) || (signa == signb) )
|
|
{
|
|
FPU_copy_to_regi(a, TAG_Special, deststnr);
|
|
setsign(dest, signa); /* signa may differ from the sign of a. */
|
|
return taga;
|
|
}
|
|
/* Infinity-Infinity is undefined. */
|
|
return arith_invalid(deststnr);
|
|
}
|
|
else if (tagb == TW_Infinity)
|
|
{
|
|
FPU_copy_to_regi(b, TAG_Special, deststnr);
|
|
setsign(dest, signb); /* signb may differ from the sign of b. */
|
|
return tagb;
|
|
}
|
|
|
|
#ifdef PARANOID
|
|
EXCEPTION(EX_INTERNAL|0x101);
|
|
#endif
|
|
|
|
return FPU_Exception;
|
|
}
|
|
|