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Justine Tunney 2020-06-15 07:18:57 -07:00
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libc/math/remquol.c Normal file
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#include "libc/math/libm.h"
#if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
long double remquol(long double x, long double y, int *quo)
{
return remquo(x, y, quo);
}
#elif (LDBL_MANT_DIG == 64 || LDBL_MANT_DIG == 113) && LDBL_MAX_EXP == 16384
long double remquol(long double x, long double y, int *quo)
{
union ldshape ux = {x}, uy = {y};
int ex = ux.i.se & 0x7fff;
int ey = uy.i.se & 0x7fff;
int sx = ux.i.se >> 15;
int sy = uy.i.se >> 15;
uint32_t q;
*quo = 0;
if (y == 0 || isnan(y) || ex == 0x7fff)
return (x*y)/(x*y);
if (x == 0)
return x;
/* normalize x and y */
if (!ex) {
ux.i.se = ex;
ux.f *= 0x1p120f;
ex = ux.i.se - 120;
}
if (!ey) {
uy.i.se = ey;
uy.f *= 0x1p120f;
ey = uy.i.se - 120;
}
q = 0;
if (ex >= ey) {
/* x mod y */
#if LDBL_MANT_DIG == 64
uint64_t i, mx, my;
mx = ux.i.m;
my = uy.i.m;
for (; ex > ey; ex--) {
i = mx - my;
if (mx >= my) {
mx = 2*i;
q++;
q <<= 1;
} else if (2*mx < mx) {
mx = 2*mx - my;
q <<= 1;
q++;
} else {
mx = 2*mx;
q <<= 1;
}
}
i = mx - my;
if (mx >= my) {
mx = i;
q++;
}
if (mx == 0)
ex = -120;
else
for (; mx >> 63 == 0; mx *= 2, ex--);
ux.i.m = mx;
#elif LDBL_MANT_DIG == 113
uint64_t hi, lo, xhi, xlo, yhi, ylo;
xhi = (ux.i2.hi & -1ULL>>16) | 1ULL<<48;
yhi = (uy.i2.hi & -1ULL>>16) | 1ULL<<48;
xlo = ux.i2.lo;
ylo = ux.i2.lo;
for (; ex > ey; ex--) {
hi = xhi - yhi;
lo = xlo - ylo;
if (xlo < ylo)
hi -= 1;
if (hi >> 63 == 0) {
xhi = 2*hi + (lo>>63);
xlo = 2*lo;
q++;
} else {
xhi = 2*xhi + (xlo>>63);
xlo = 2*xlo;
}
q <<= 1;
}
hi = xhi - yhi;
lo = xlo - ylo;
if (xlo < ylo)
hi -= 1;
if (hi >> 63 == 0) {
xhi = hi;
xlo = lo;
q++;
}
if ((xhi|xlo) == 0)
ex = -120;
else
for (; xhi >> 48 == 0; xhi = 2*xhi + (xlo>>63), xlo = 2*xlo, ex--);
ux.i2.hi = xhi;
ux.i2.lo = xlo;
#endif
}
/* scale result and decide between |x| and |x|-|y| */
if (ex <= 0) {
ux.i.se = ex + 120;
ux.f *= 0x1p-120f;
} else
ux.i.se = ex;
x = ux.f;
if (sy)
y = -y;
if (ex == ey || (ex+1 == ey && (2*x > y || (2*x == y && q%2)))) {
x -= y;
q++;
}
q &= 0x7fffffff;
*quo = sx^sy ? -(int)q : (int)q;
return sx ? -x : x;
}
#endif