82 lines
1.3 KiB
C
82 lines
1.3 KiB
C
#include "libc/math/math.h"
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double remquo(double x, double y, int *quo)
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{
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union {double f; uint64_t i;} ux = {x}, uy = {y};
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int ex = ux.i>>52 & 0x7ff;
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int ey = uy.i>>52 & 0x7ff;
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int sx = ux.i>>63;
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int sy = uy.i>>63;
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uint32_t q;
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uint64_t i;
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uint64_t uxi = ux.i;
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*quo = 0;
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if (uy.i<<1 == 0 || isnan(y) || ex == 0x7ff)
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return (x*y)/(x*y);
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if (ux.i<<1 == 0)
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return x;
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/* normalize x and y */
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if (!ex) {
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for (i = uxi<<12; i>>63 == 0; ex--, i <<= 1);
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uxi <<= -ex + 1;
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} else {
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uxi &= -1ULL >> 12;
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uxi |= 1ULL << 52;
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}
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if (!ey) {
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for (i = uy.i<<12; i>>63 == 0; ey--, i <<= 1);
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uy.i <<= -ey + 1;
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} else {
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uy.i &= -1ULL >> 12;
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uy.i |= 1ULL << 52;
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}
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q = 0;
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if (ex < ey) {
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if (ex+1 == ey)
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goto end;
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return x;
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}
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/* x mod y */
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for (; ex > ey; ex--) {
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i = uxi - uy.i;
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if (i >> 63 == 0) {
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uxi = i;
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q++;
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}
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uxi <<= 1;
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q <<= 1;
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}
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i = uxi - uy.i;
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if (i >> 63 == 0) {
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uxi = i;
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q++;
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}
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if (uxi == 0)
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ex = -60;
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else
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for (; uxi>>52 == 0; uxi <<= 1, ex--);
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end:
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/* scale result and decide between |x| and |x|-|y| */
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if (ex > 0) {
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uxi -= 1ULL << 52;
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uxi |= (uint64_t)ex << 52;
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} else {
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uxi >>= -ex + 1;
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}
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ux.i = uxi;
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x = ux.f;
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if (sy)
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y = -y;
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if (ex == ey || (ex+1 == ey && (2*x > y || (2*x == y && q%2)))) {
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x -= y;
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q++;
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}
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q &= 0x7fffffff;
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*quo = sx^sy ? -(int)q : (int)q;
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return sx ? -x : x;
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}
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