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BSD 4_3 release
[unix-history] / usr / src / bin / as / bignum2.c
/*
* Copyright (c) 1982 Regents of the University of California.
* All rights reserved. The Berkeley software License Agreement
* specifies the terms and conditions for redistribution.
*/
#ifndef lint
static char sccsid[] = "@(#)bignum2.c 5.1 (Berkeley) 4/30/85";
#endif not lint
#include <stdio.h>
#include "as.h"
Bignum Znumber; /* zero reference */
#define MINEXP -32768 /* never generate; reserved for id 0 */
Bignum intconvert(number, convto)
Bignum number;
int convto;
{
reg int i;
if (number.num_tag == convto)
return(number);
if (ty_nbyte[number.num_tag] > ty_nbyte[convto] && (passno == 2)){
yywarning("Conversion between %s and %s looses significance",
ty_string[number.num_tag],
ty_string[convto]);
}
for (i = ty_nbyte[convto]; i < ty_nbyte[TYPO]; i++)
number.num_uchar[i] = 0;
return(number);
}
#define CONV(src, dst) (((src) << TYPLG) + (dst))
Bignum floatconvert(number, convto)
Bignum number;
int convto;
{
reg u_int *bp; /* r11 */
int loss = 0;
int gain = 0;
int mixs = 0;
Ovf ovf;
if (number.num_tag == convto)
return(number);
bp = &number.num_uint[0];
#ifdef lint
*bp = *bp;
#endif lint
switch(CONV(number.num_tag, convto)){
case CONV(TYPF, TYPD): asm("cvtfd (r11), (r11)"); break;
case CONV(TYPF, TYPG): mixs++; break;
case CONV(TYPF, TYPH): mixs++; break;
case CONV(TYPD, TYPF): asm("cvtdf (r11), (r11)"); break;
case CONV(TYPD, TYPG): mixs++; break;
case CONV(TYPD, TYPH): mixs++; break;
case CONV(TYPG, TYPF): mixs++; break;
case CONV(TYPG, TYPD): mixs++; break;
case CONV(TYPG, TYPH): mixs++; break;
case CONV(TYPH, TYPF): mixs++; break;
case CONV(TYPH, TYPD): mixs++; break;
case CONV(TYPH, TYPG): mixs++; break;
default: panic("Bad floating point conversion?");
}
if ((gain || mixs || loss) && (passno == 2)){
yywarning("Converting from %s to %s: %s ",
ty_string[number.num_tag],
ty_string[convto],
gain ? "gains significance" :
(loss ? "looses significance" : "mixs exponent formats")
);
}
if (mixs){
number = bignumconvert(number, convto, &ovf);
if (ovf && passno == 2){
yywarning("Floating conversion over/underflowed\n");
}
} else {
number.num_tag = convto;
}
return(number);
}
/*
* Convert a big number between various representations
*/
Bignum bignumconvert(number, toconv, ovfp)
Bignum number;
int toconv;
Ovf *ovfp;
{
int tag;
*ovfp = 0;
tag = number.num_tag;
if (tag == toconv)
return(number);
if (tag == TYPUNPACKED){
return(bignumpack(number, toconv, ovfp));
}
if (toconv == TYPUNPACKED){
return(bignumunpack(number, ovfp));
}
return(bignumpack(bignumunpack(number, ovfp), toconv, ovfp));
}
Bignum bignumunpack(Packed, ovfp)
Bignum Packed;
Ovf *ovfp;
{
Bignum Mantissa;
Bignum Enumber;
reg int i;
int j;
int k;
reg struct ty_bigdesc *p;
reg chptr packed;
reg chptr mantissa;
reg chptr enumber;
u_short exponent;
int sign;
int mask;
p = &ty_bigdesc[Packed.num_tag];
*ovfp = 0;
Mantissa = Znumber;
sign = 0;
exponent = 0;
mantissa = CH_FIELD(Mantissa);
enumber = CH_FIELD(Enumber);
packed = CH_FIELD(Packed);
if (isclear(packed)){
Mantissa.num_tag = TYPUNPACKED;
Mantissa.num_exponent = MINEXP;
return(Mantissa);
}
/*
* map the packed number into the mantissa, using
* the unpacking map
*/
mapnumber(mantissa, packed, 16, p->b_upmmap);
/*
* perform the mantissa shifting.
* This may appear to overflow; all that is lost
* is low order bits of the exponent.
*/
(void)numshift(p->b_mlshift, mantissa, mantissa);
/*
* handle sign and exponent
*/
switch(Packed.num_tag){
case TYPB:
case TYPW:
case TYPL:
case TYPO:
case TYPQ:
sign = 0;
exponent = p->b_eexcess;
if (mantissa[HOC] & SIGNBIT){
sign = -1;
*ovfp |= numnegate(mantissa, mantissa);
}
/*
* Normalize the packed by left shifting,
* adjusting the exponent as we go.
* Do a binary weighted left shift for some speed.
*/
k = 0;
for (j = 4; j >= 0; --j){
i = 1 << j; /* 16, 8, 4, 2, 1 */
while(1){
if (k >= p->b_msigbits)
break;
mask = ONES(i) << (CH_BITS - i);
if (mantissa[HOC] & mask)
break;
(void)numshift(i, mantissa, mantissa);
k += i;
exponent -= i;
}
}
assert(mantissa[HOC] & SIGNBIT, "integer <<ing");
/*
* now, kick the most significant bit off the top
*/
(void)numshift(1, mantissa, mantissa);
break;
default:
/*
* map the exponent into the local area.
*/
Enumber = Znumber;
mapnumber(enumber, packed, 2, p->b_upemap);
/*
* Extract the exponent, and get rid
* of the sign bit
*/
exponent = Enumber.num_ushort[0] & ONES(15);
/*
* shift the exponent, and get rid of high order
* trash
*/
exponent >>= p->b_ershift;
exponent &= ONES(p->b_esigbits);
/*
* un excess the exponent
*/
exponent -= p->b_eexcess;
/*
* extract and extend the sign bit
*/
sign = (Enumber.num_ushort[0] & ~ONES(15)) ? -1 : 0;
}
/*
* Assemble the pieces, and return the number
*/
Mantissa.num_tag = TYPUNPACKED;
Mantissa.num_sign = sign;
Mantissa.num_exponent = exponent;
return(Mantissa);
}
Bignum bignumpack(Unpacked, toconv, ovfp)
Bignum Unpacked;
int toconv;
Ovf *ovfp;
{
Bignum Back;
Bignum Enumber;
Bignum Temp;
short exponent;
char sign;
reg struct ty_bigdesc *p;
reg chptr back;
reg chptr enumber;
reg chptr temp;
reg chptr unpacked;
int i,j;
if (Unpacked.num_tag != TYPUNPACKED)
panic("Argument to bignumpack is not unpacked");
*ovfp = 0;
Back = Znumber;
Temp = Znumber;
Back.num_tag = toconv;
back = CH_FIELD(Back);
temp = CH_FIELD(Temp);
enumber = CH_FIELD(Enumber);
unpacked = CH_FIELD(Unpacked);
p = &ty_bigdesc[toconv];
exponent = Unpacked.num_exponent;
sign = Unpacked.num_sign;
if (exponent == MINEXP)
return(Back); /* identically zero */
switch(toconv){
case TYPB:
case TYPW:
case TYPL:
case TYPQ:
case TYPO:
/*
* Put back in the assumed high order fraction
* bit that is always a 1.
*/
(void)numshift(-1, temp, unpacked);
temp[HOC] |= SIGNBIT;
if (exponent > p->b_eexcess){
/*
* Construct the largest positive integer
*/
(void)numclear(temp);
(void)num1comp(temp, temp);
temp[HOC] &= ~SIGNBIT;
sign = sign;
*ovfp |= OVF_OVERFLOW;
} else
if (exponent <= 0){
/*
* chop the temp; underflow to integer 0
*/
(void)numclear(temp);
sign = 0;
*ovfp |= OVF_UNDERFLOW;
} else {
/*
* denormalize the temp.
* This will again chop, by shifting
* bits off the right end into oblivion.
*/
for (j = 4; j >= 0; --j){
i = 1 << j; /* 16, 8, 4, 2, 1 */
while(exponent + i <= p->b_eexcess){
numshift(-i, temp, temp);
exponent += i;
}
}
}
/*
* negate the temp if the sign is set
*/
if (sign)
*ovfp |= numnegate(temp, temp);
/*
* Stuff the temp number into the return area
*/
mapnumber(back, temp, 16, p->b_pmmap);
return(Back);
default:
/*
* Shift the mantissa to the right, filling in zeroes on
* the left. This aligns the least significant bit
* on the bottom of a byte, something that upround
* will use.
* Put the result into a temporary.
* Even though the shift may be zero, there
* is still a copy involved here.
*/
(void)numshift(-(p->b_mlshift), temp, unpacked);
/*
* Perform the rounding by adding in 0.5 ulp's
*/
exponent = upround(&Temp, p, exponent);
/*
* Do a range check on the exponent, in preparation
* to stuffing it in.
*/
if ((short)(exponent + p->b_eexcess) == 0){
/*
* Sorry, no gradual underflow on the
* VAX. Chop this beasty totally to zero
*/
goto zeroret;
} else
if ((short)(exponent + p->b_eexcess) < 0){
/*
* True underflow will happen;
* Chop everything to positive zero
*/
zeroret:
(void)numclear(temp);
exponent = 0;
sign = 0; /* avoid reserved operand! */
*ovfp |= OVF_UNDERFLOW;
} else
if ((unsigned)(exponent + p->b_eexcess)
>= (unsigned)(1 << p->b_esigbits)){
/*
* Construct the largest magnitude possible
* floating point unpacked: 0.{1}111111111
*/
(void)numclear(temp);
(void)num1comp(temp, temp);
exponent = ONES(p->b_esigbits);
sign = sign;
*ovfp |= OVF_OVERFLOW;
} else {
/*
* The exponent will fit.
* Bias it up, and the common code will stuff it.
*/
exponent += p->b_eexcess;
}
exponent <<= p->b_ershift;
/*
* mask out trash for the sign, and put in the sign.
*/
exponent &= ONES(15);
if (sign)
exponent |= ~ONES(15);
Enumber.num_ushort[0] = exponent;
/*
* Map the unpacked exponent into the value going back
*/
mapnumber(back, enumber, 2, p->b_pemap);
/*
* Stuff the unpacked mantissa into the return area
*/
mapnumber(back, temp, 16, p->b_pmmap);
return(Back);
}
/*NOTREACHED*/
}
mapnumber(chp1, chp2, nbytes, themap)
chptr chp1, chp2;
int nbytes;
char *themap;
{
reg int i;
reg u_char *p1, *p2;
p1 = (u_char *)chp1;
p2 = (u_char *)chp2;
for (i = 0; i < nbytes; i++){
switch(themap[i]){
case NOTAKE:
break;
default:
p1[themap[i]] |= p2[i];
break;
}
}
}
#define UPSHIFT 2
/*
* round in 1/2 ulp in the number, possibly modifying
* the binary exponent if there was total carry out.
* Return the modified exponent
*/
int upround(numberp, p, exponent)
reg Bignum *numberp;
reg struct ty_bigdesc *p;
int exponent;
{
reg u_char *bytep;
int nbytes;
int byteindex;
int hofractionbit;
int ovffractionbit;
reg int ovfbitindex;
reg chptr number;
static Bignum ulp;
/*
* Find out the byte index of the byte containing the ulp
*/
number = CH_FIELD(numberp[0]);
bytep = numberp->num_uchar;
nbytes = (p->b_msigbits - 1) + p->b_mlshift;
assert((nbytes % 8) == 0, "mantissa sig bits");
nbytes /= 8;
byteindex = 15 - nbytes;
assert(byteindex >= 0, "ulp in outer space");
/*
* Shift the number to the right by two places,
* so that we can do full arithmetic without overflowing
* to the left.
*/
numshift(-UPSHIFT, number, number);
/*
* Construct the missing high order fraction bit
*/
ovfbitindex = 8 - (p->b_mlshift + UPSHIFT);
assert(ovfbitindex >= 0, "Shifted byte 15 into byte 14");
hofractionbit = (0x01 << ovfbitindex);
ovffractionbit = (0x02 << ovfbitindex);
bytep[15] |= hofractionbit;
/*
* construct the unit in the last place, and it
* to the fraction
*/
ulp.num_uchar[byteindex] |= (0x80 >> UPSHIFT);
numaddv(number, number, CH_FIELD(ulp));
ulp.num_uchar[byteindex] &= ~(0x80 >> UPSHIFT);
/*
* Check if there was an overflow,
* and adjust by shifting.
* Also, bring the number back into canonical
* unpacked form by left shifting by two to undeo
* what we did before.
*/
if (bytep[15] & ovffractionbit){
exponent += 1;
numshift(UPSHIFT - 1, number, number);
} else {
numshift(UPSHIFT, number, number);
}
/*
* Clear off trash in the unused bits of the high
* order byte of the number
*/
bytep[15] &= ONES(8 - p->b_mlshift);
return(exponent);
}
#ifdef DEBUG
bignumprint(number)
Bignum number;
{
printf("Bignum: %s (exp: %d, sign: %d) 0x%08x%08x%08x%08x",
ty_string[number.num_tag],
number.num_exponent,
number.num_sign,
number.num_uint[3],
number.num_uint[2],
number.num_uint[1],
number.num_uint[0]);
switch(number.num_tag){
case TYPB:
case TYPW:
case TYPL:
case TYPQ:
case TYPO:
case TYPUNPACKED:
break;
case TYPF:
printf(" == %10.8e", number.num_num.numFf_float.Ff_value);
break;
case TYPD:
printf(" == %20.17e", number.num_num.numFd_float.Fd_value);
break;
case TYPG:
case TYPH:
break;
}
}
numprintovf(ovf)
Ovf ovf;
{
int i;
static struct ovftab{
Ovf which;
char *print;
} ovftab[] = {
OVF_POSOVF, "posovf",
OVF_MAXINT, "maxint",
OVF_ADDV, "addv",
OVF_LSHIFT, "lshift",
OVF_F, "F float",
OVF_D, "D float",
OVF_G, "G float",
OVF_H, "H float",
OVF_OVERFLOW, "cvt overflow",
OVF_UNDERFLOW, "cvt underflow",
0, 0
};
for(i = 0; ovftab[i].which; i++){
if (ovf & ovftab[i].which)
printf("Overflow(%s) ", ovftab[i].print);
}
}
#endif DEBUG
Continuous source code history from original PDP-7 UNIX to FreeBSD 2, the first fully unencumbered FreeBSD release.