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Justine Tunney 2020-06-15 07:18:57 -07:00
commit c91b3c5006
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81
libc/math/remquof.c Normal file
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#include "libc/math/math.h"
float remquof(float x, float y, int *quo)
{
union {float f; uint32_t i;} ux = {x}, uy = {y};
int ex = ux.i>>23 & 0xff;
int ey = uy.i>>23 & 0xff;
int sx = ux.i>>31;
int sy = uy.i>>31;
uint32_t q;
uint32_t i;
uint32_t uxi = ux.i;
*quo = 0;
if (uy.i<<1 == 0 || isnan(y) || ex == 0xff)
return (x*y)/(x*y);
if (ux.i<<1 == 0)
return x;
/* normalize x and y */
if (!ex) {
for (i = uxi<<9; i>>31 == 0; ex--, i <<= 1);
uxi <<= -ex + 1;
} else {
uxi &= -1U >> 9;
uxi |= 1U << 23;
}
if (!ey) {
for (i = uy.i<<9; i>>31 == 0; ey--, i <<= 1);
uy.i <<= -ey + 1;
} else {
uy.i &= -1U >> 9;
uy.i |= 1U << 23;
}
q = 0;
if (ex < ey) {
if (ex+1 == ey)
goto end;
return x;
}
/* x mod y */
for (; ex > ey; ex--) {
i = uxi - uy.i;
if (i >> 31 == 0) {
uxi = i;
q++;
}
uxi <<= 1;
q <<= 1;
}
i = uxi - uy.i;
if (i >> 31 == 0) {
uxi = i;
q++;
}
if (uxi == 0)
ex = -30;
else
for (; uxi>>23 == 0; uxi <<= 1, ex--);
end:
/* scale result and decide between |x| and |x|-|y| */
if (ex > 0) {
uxi -= 1U << 23;
uxi |= (uint32_t)ex << 23;
} else {
uxi >>= -ex + 1;
}
ux.i = uxi;
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;
}