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:
diff = expa - expb;
if (!diff) {
diff = a->sigh - b->sigh;
if (!diff) {
diff = a->sigl > b->sigl;
if (!diff)
diff = -(a->sigl < b->sigl);
}
}
switch ((((int)signa) * 2 + signb) / SIGN_NEG) {
case 0:
case 3:
if (diff > 0) {
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);
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:
tag =
FPU_u_add(a, b, dest, control_w, SIGN_POS, expa,
expb);
break;
case 2:
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);
}
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:
if (!(signa ^ signb)) {
tag =
FPU_u_add(a, b, dest, control_w, signa, expa, expb);
} else {
diff = expa - expb;
if (!diff) {
diff = a->sigh - b->sigh;
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);
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);
}
/*
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;
}
static int
math_emulate(struct trapframe * tframe)
{
unsigned char FPU_modrm;
unsigned short code;
#ifdef LOOKAHEAD_LIMIT
int lookahead_limit = LOOKAHEAD_LIMIT;
#endif
#ifdef PARANOID
if (emulating) {
printf("ERROR: wm-FPU-emu is not RE-ENTRANT!\n");
}
REENTRANT_CHECK(ON);
#endif /* PARANOID */
if ((((struct pcb *) curproc->p_addr)->pcb_flags & FP_SOFTFP) == 0) {
finit();
control_word = __INITIAL_NPXCW__;
((struct pcb *) curproc->p_addr)->pcb_flags |= FP_SOFTFP;
}
FPU_info = tframe;
FPU_ORIG_EIP = FPU_EIP; /* --pink-- */
if (FPU_CS != 0x001f) {
printf("math_emulate: %x : %x\n", FPU_CS, FPU_EIP);
panic("FPU emulation in kernel");
}
#ifdef notyet
/* We cannot handle emulation in v86-mode */
if (FPU_EFLAGS & 0x00020000) {
FPU_ORIG_EIP = FPU_EIP;
math_abort(FPU_info, SIGILL);
}
#endif
FPU_lookahead = FPU_LOOKAHEAD;
if (curproc->p_flag & P_TRACED)
FPU_lookahead = 0;
do_another_FPU_instruction:
REENTRANT_CHECK(OFF);
code = fuword((u_int *) FPU_EIP);
REENTRANT_CHECK(ON);
if ((code & 0xff) == 0x9b) { /* fwait */
if (status_word & SW_Summary)
goto do_the_FPU_interrupt;
else {
FPU_EIP++;
goto FPU_instruction_done;
}
}
if (status_word & SW_Summary) {
/* Ignore the error for now if the current instruction is a
* no-wait control instruction */
/* The 80486 manual contradicts itself on this topic, so I use
* the following list of such instructions until I can check
* on a real 80486: fninit, fnstenv, fnsave, fnstsw, fnstenv,
* fnclex. */
if (!((((code & 0xf803) == 0xe003) || /* fnclex, fninit,
* fnstsw */
(((code & 0x3003) == 0x3001) && /* fnsave, fnstcw,
* fnstenv, fnstsw */
((code & 0xc000) != 0xc000))))) {
/* This is a guess about what a real FPU might do to
* this bit: */
/* status_word &= ~SW_Summary; ****/
/* We need to simulate the action of the kernel to FPU
* interrupts here. Currently, the "real FPU" part of
* the kernel (0.99.10) clears the exception flags,
* sets the registers to empty, and passes information
* back to the interrupted process via the cs selector
* and operand selector, so we do the same. */
do_the_FPU_interrupt:
cs_selector &= 0xffff0000;
cs_selector |= (status_word & ~SW_Top) | ((top & 7) << SW_Top_Shift);
operand_selector = tag_word();
status_word = 0;
top = 0;
{
int r;
for (r = 0; r < 8; r++) {
regs[r].tag = TW_Empty;
}
}
REENTRANT_CHECK(OFF);
math_abort(SIGFPE);
}
}
FPU_entry_eip = FPU_ORIG_EIP = FPU_EIP;
if ((code & 0xff) == 0x66) { /* size prefix */
FPU_EIP++;
REENTRANT_CHECK(OFF);
code = fuword((u_int *) FPU_EIP);
REENTRANT_CHECK(ON);
}
FPU_EIP += 2;
FPU_modrm = code >> 8;
FPU_rm = FPU_modrm & 7;
if (FPU_modrm < 0300) {
/* All of these instructions use the mod/rm byte to get a data
* address */
get_address(FPU_modrm);
if (!(code & 1)) {
unsigned short status1 = status_word;
FPU_st0_ptr = &st(0);
FPU_st0_tag = FPU_st0_ptr->tag;
/* Stack underflow has priority */
if (NOT_EMPTY_0) {
switch ((code >> 1) & 3) {
case 0:
reg_load_single();
break;
case 1:
reg_load_int32();
break;
case 2:
reg_load_double();
break;
case 3:
reg_load_int16();
break;
}
/* No more access to user memory, it is safe
* to use static data now */
FPU_st0_ptr = &st(0);
FPU_st0_tag = FPU_st0_ptr->tag;
/* NaN operands have the next priority. */
/* We have to delay looking at st(0) until
* after loading the data, because that data
* might contain an SNaN */
if ((FPU_st0_tag == TW_NaN) ||
(FPU_loaded_data.tag == TW_NaN)) {
/* Restore the status word; we might
* have loaded a denormal. */
status_word = status1;
if ((FPU_modrm & 0x30) == 0x10) {
/* fcom or fcomp */
EXCEPTION(EX_Invalid);
setcc(SW_C3 | SW_C2 | SW_C0);
if (FPU_modrm & 0x08)
pop(); /* fcomp, so we pop. */
} else
real_2op_NaN(FPU_st0_ptr, &FPU_loaded_data, FPU_st0_ptr);
goto reg_mem_instr_done;
}
switch ((FPU_modrm >> 3) & 7) {
case 0: /* fadd */
reg_add(FPU_st0_ptr, &FPU_loaded_data, FPU_st0_ptr, control_word);
break;
case 1: /* fmul */
reg_mul(FPU_st0_ptr, &FPU_loaded_data, FPU_st0_ptr, control_word);
break;
case 2: /* fcom */
compare_st_data();
break;
case 3: /* fcomp */
compare_st_data();
pop();
break;
case 4: /* fsub */
reg_sub(FPU_st0_ptr, &FPU_loaded_data, FPU_st0_ptr, control_word);
break;
case 5: /* fsubr */
reg_sub(&FPU_loaded_data, FPU_st0_ptr, FPU_st0_ptr, control_word);
break;
case 6: /* fdiv */
reg_div(FPU_st0_ptr, &FPU_loaded_data, FPU_st0_ptr, control_word);
break;
case 7: /* fdivr */
if (FPU_st0_tag == TW_Zero)
status_word = status1; /* Undo any denorm tag,
* zero-divide has
* priority. */
reg_div(&FPU_loaded_data, FPU_st0_ptr, FPU_st0_ptr, control_word);
break;
}
} else {
if ((FPU_modrm & 0x30) == 0x10) {
int FPU_mul(FPU_REG const *b, u_char tagb, int deststnr, int control_w)
{
FPU_REG *a = &st(deststnr);
FPU_REG *dest = a;
u_char taga = FPU_gettagi(deststnr);
u_char saved_sign = getsign(dest);
u_char sign = (getsign(a) ^ getsign(b));
int tag;
if (!(taga | tagb)) {
tag =
FPU_u_mul(a, b, dest, control_w, sign,
exponent(a) + exponent(b));
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);
tag = FPU_u_mul(&x, &y, dest, control_w, sign,
exponent16(&x) + exponent16(&y));
if (tag < 0) {
setsign(dest, saved_sign);
return tag;
}
FPU_settagi(deststnr, tag);
return tag;
} else if ((taga <= TW_Denormal) && (tagb <= TW_Denormal)) {
if (((tagb == TW_Denormal) || (taga == TW_Denormal))
&& (denormal_operand() < 0))
return FPU_Exception;
FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr);
setsign(dest, sign);
return TAG_Zero;
}
else if ((taga == TW_NaN) || (tagb == TW_NaN)) {
return real_2op_NaN(b, tagb, deststnr, &st(0));
} else if (((taga == TW_Infinity) && (tagb == TAG_Zero))
|| ((tagb == TW_Infinity) && (taga == TAG_Zero))) {
return arith_invalid(deststnr);
} else if (((taga == TW_Denormal) || (tagb == TW_Denormal))
&& (denormal_operand() < 0)) {
return FPU_Exception;
} else if (taga == TW_Infinity) {
FPU_copy_to_regi(a, TAG_Special, deststnr);
setsign(dest, sign);
return TAG_Special;
} else if (tagb == TW_Infinity) {
FPU_copy_to_regi(b, TAG_Special, deststnr);
setsign(dest, sign);
return TAG_Special;
}
#ifdef PARANOID
else {
EXCEPTION(EX_INTERNAL | 0x102);
return FPU_Exception;
}
#endif
return 0;
}
void reg_add(FPU_REG *a, FPU_REG *b, FPU_REG *dest, int control_w)
{
int diff;
if ( !(a->tag | b->tag) )
{
/* Both registers are valid */
if (!(a->sign ^ b->sign))
{
/* signs are the same */
reg_u_add(a, b, dest, control_w);
dest->sign = a->sign;
return;
}
/* The signs are different, so do a subtraction */
diff = a->exp - b->exp;
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);
}
}
if (diff > 0)
{
reg_u_sub(a, b, dest, control_w);
dest->sign = a->sign;
}
else if ( diff == 0 )
{
reg_move(&CONST_Z, dest);
/* sign depends upon rounding mode */
dest->sign = ((control_w & CW_RC) != RC_DOWN)
? SIGN_POS : SIGN_NEG;
}
else
{
reg_u_sub(b, a, dest, control_w);
dest->sign = b->sign;
}
return;
}
else
{
if ( (a->tag == TW_NaN) || (b->tag == TW_NaN) )
{
real_2op_NaN(a, b, dest);
return;
}
else if (a->tag == TW_Zero)
{
if (b->tag == TW_Zero)
{
char different_signs = a->sign ^ b->sign;
/* Both are zero, result will be zero. */
reg_move(a, dest);
if (different_signs)
{
/* Signs are different. */
/* Sign of answer depends upon rounding mode. */
dest->sign = ((control_w & CW_RC) != RC_DOWN)
? SIGN_POS : SIGN_NEG;
}
}
else
reg_move(b, dest);
return;
}
else if (b->tag == TW_Zero)
{
reg_move(a, dest);
return;
}
else if (a->tag == TW_Infinity)
{
if (b->tag != TW_Infinity)
{
reg_move(a, dest);
return;
}
/* They are both + or - infinity */
if (a->sign == b->sign)
{
reg_move(a, dest);
return;
}
reg_move(&CONST_QNaN, dest); /* inf - inf is undefined. */
return;
}
else if (b->tag == TW_Infinity)
{
reg_move(b, dest);
return;
}
}
#ifdef PARANOID
EXCEPTION(EX_INTERNAL|0x101);
#endif
}
/* Subtract b from a. (a-b) -> dest */
void reg_sub(FPU_REG *a, FPU_REG *b, FPU_REG *dest, int control_w)
{
int diff;
if ( !(a->tag | b->tag) )
{
/* Both registers are valid */
diff = a->exp - b->exp;
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 (a->sign*2 + b->sign)
{
case 0: /* P - P */
case 3: /* N - N */
if (diff > 0)
{
reg_u_sub(a, b, dest, control_w);
dest->sign = a->sign;
}
else if ( diff == 0 )
{
reg_move(&CONST_Z, dest);
/* sign depends upon rounding mode */
dest->sign = ((control_w & CW_RC) != RC_DOWN)
? SIGN_POS : SIGN_NEG;
}
else
{
reg_u_sub(b, a, dest, control_w);
dest->sign = a->sign ^ SIGN_POS^SIGN_NEG;
}
return;
case 1: /* P - N */
reg_u_add(a, b, dest, control_w);
dest->sign = SIGN_POS;
return;
case 2: /* N - P */
reg_u_add(a, b, dest, control_w);
dest->sign = SIGN_NEG;
return;
}
}
else
{
if ( (a->tag == TW_NaN) || (b->tag == TW_NaN) )
{
real_2op_NaN(a, b, dest);
return;
}
else if (b->tag == TW_Zero)
{
if (a->tag == TW_Zero)
{
char same_signs = !(a->sign ^ b->sign);
/* Both are zero, result will be zero. */
reg_move(a, dest); /* Answer for different signs. */
if (same_signs)
{
/* Sign depends upon rounding mode */
dest->sign = ((control_w & CW_RC) != RC_DOWN)
? SIGN_POS : SIGN_NEG;
}
}
else
reg_move(a, dest);
return;
}
else if (a->tag == TW_Zero)
{
reg_move(b, dest);
dest->sign ^= SIGN_POS^SIGN_NEG;
return;
}
else if (a->tag == TW_Infinity)
{
if (b->tag != TW_Infinity)
{
reg_move(a, dest);
return;
}
if (a->sign == b->sign)
{
reg_move(&CONST_QNaN, dest);
return;
}
reg_move(a, dest);
return;
}
else if (b->tag == TW_Infinity)
{
reg_move(b, dest);
dest->sign ^= SIGN_POS^SIGN_NEG;
return;
}
}
#ifdef PARANOID
EXCEPTION(EX_INTERNAL|0x110);
#endif
}
/*
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, u16 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);
}
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)) {
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) {
if (tagb == TW_Denormal) {
if (denormal_operand() < 0)
return FPU_Exception;
}
FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr);
setsign(dest, sign);
return TAG_Zero;
}
if (taga == TAG_Zero) {
return arith_invalid(deststnr);
}
return FPU_divide_by_zero(deststnr, sign);
}
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) {
return arith_invalid(deststnr);
} else {
if ((tagb == TW_Denormal) && (denormal_operand() < 0))
return FPU_Exception;
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;
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
return 0;
}