xref: /illumos-gate/usr/src/lib/libc/sparc/fp/_Q_div.c (revision 1da57d551424de5a9d469760be7c4b4d4f10a755)

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2003 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#include "quad.h"

static const double C[] = {
	0.0,
	1.0,
	68719476736.0,
	402653184.0,
	24.0,
	16.0,
	3.66210937500000000000e-04,
	1.52587890625000000000e-05,
	1.43051147460937500000e-06,
	5.96046447753906250000e-08,
	3.72529029846191406250e-09,
	2.18278728425502777100e-11,
	8.52651282912120223045e-14,
	3.55271367880050092936e-15,
	1.30104260698260532081e-18,
	8.67361737988403547206e-19,
	2.16840434497100886801e-19,
	3.17637355220362627151e-22,
	7.75481824268463445192e-26,
	4.62223186652936604733e-33,
	9.62964972193617926528e-35,
	4.70197740328915003187e-38,
	2.75506488473973634680e-40,
};

#define	zero		C[0]
#define	one		C[1]
#define	two36		C[2]
#define	three2p27	C[3]
#define	three2p3	C[4]
#define	two4		C[5]
#define	three2m13	C[6]
#define	twom16		C[7]
#define	three2m21	C[8]
#define	twom24		C[9]
#define	twom28		C[10]
#define	three2m37	C[11]
#define	three2m45	C[12]
#define	twom48		C[13]
#define	three2m61	C[14]
#define	twom60		C[15]
#define	twom62		C[16]
#define	three2m73	C[17]
#define	three2m85	C[18]
#define	three2m109	C[19]
#define	twom113		C[20]
#define	twom124		C[21]
#define	three2m133	C[22]

static const unsigned int
	fsr_re = 0x00000000u,
	fsr_rn = 0xc0000000u;

#ifdef __sparcv9

/*
 * _Qp_div(pz, x, y) sets *pz = *x / *y.
 */
void
_Qp_div(union longdouble *pz, const union longdouble *x,
	const union longdouble *y)

#else

/*
 * _Q_div(x, y) returns *x / *y.
 */
union longdouble
_Q_div(const union longdouble *x, const union longdouble *y)

#endif /* __sparcv9 */

{
	union longdouble	z;
	union xdouble		u;
	double			c, d, ry, xx[4], yy[5], zz[5];
	unsigned int		xm, ym, fsr, lx, ly, wx[3], wy[3];
	unsigned int		msw, frac2, frac3, frac4, rm;
	int			ibit, ex, ey, ez, sign;

	xm = x->l.msw & 0x7fffffff;
	ym = y->l.msw & 0x7fffffff;
	sign = (x->l.msw ^ y->l.msw) & ~0x7fffffff;

	__quad_getfsrp(&fsr);

	/* handle nan and inf cases */
	if (xm >= 0x7fff0000 || ym >= 0x7fff0000) {
		/* handle nan cases according to V9 app. B */
		if (QUAD_ISNAN(*y)) {
			if (!(y->l.msw & 0x8000)) {
				/* snan, signal invalid */
				if (fsr & FSR_NVM) {
					__quad_fdivq(x, y, &Z);
				} else {
					Z = *y;
					Z.l.msw |= 0x8000;
					fsr = (fsr & ~FSR_CEXC) | FSR_NVA |
					    FSR_NVC;
					__quad_setfsrp(&fsr);
				}
				QUAD_RETURN(Z);
			} else if (QUAD_ISNAN(*x) && !(x->l.msw & 0x8000)) {
				/* snan, signal invalid */
				if (fsr & FSR_NVM) {
					__quad_fdivq(x, y, &Z);
				} else {
					Z = *x;
					Z.l.msw |= 0x8000;
					fsr = (fsr & ~FSR_CEXC) | FSR_NVA |
					    FSR_NVC;
					__quad_setfsrp(&fsr);
				}
				QUAD_RETURN(Z);
			}
			Z = *y;
			QUAD_RETURN(Z);
		}
		if (QUAD_ISNAN(*x)) {
			if (!(x->l.msw & 0x8000)) {
				/* snan, signal invalid */
				if (fsr & FSR_NVM) {
					__quad_fdivq(x, y, &Z);
				} else {
					Z = *x;
					Z.l.msw |= 0x8000;
					fsr = (fsr & ~FSR_CEXC) | FSR_NVA |
					    FSR_NVC;
					__quad_setfsrp(&fsr);
				}
				QUAD_RETURN(Z);
			}
			Z = *x;
			QUAD_RETURN(Z);
		}
		if (xm == 0x7fff0000) {
			/* x is inf */
			if (ym == 0x7fff0000) {
				/* inf / inf, signal invalid */
				if (fsr & FSR_NVM) {
					__quad_fdivq(x, y, &Z);
				} else {
					Z.l.msw = 0x7fffffff;
					Z.l.frac2 = Z.l.frac3 =
					    Z.l.frac4 = 0xffffffff;
					fsr = (fsr & ~FSR_CEXC) | FSR_NVA |
					    FSR_NVC;
					__quad_setfsrp(&fsr);
				}
				QUAD_RETURN(Z);
			}
			/* inf / finite, return inf */
			Z.l.msw = sign | 0x7fff0000;
			Z.l.frac2 = Z.l.frac3 = Z.l.frac4 = 0;
			QUAD_RETURN(Z);
		}
		/* y is inf */
		Z.l.msw = sign;
		Z.l.frac2 = Z.l.frac3 = Z.l.frac4 = 0;
		QUAD_RETURN(Z);
	}

	/* handle zero cases */
	if (xm == 0 || ym == 0) {
		if (QUAD_ISZERO(*x)) {
			if (QUAD_ISZERO(*y)) {
				/* zero / zero, signal invalid */
				if (fsr & FSR_NVM) {
					__quad_fdivq(x, y, &Z);
				} else {
					Z.l.msw = 0x7fffffff;
					Z.l.frac2 = Z.l.frac3 =
					    Z.l.frac4 = 0xffffffff;
					fsr = (fsr & ~FSR_CEXC) | FSR_NVA |
					    FSR_NVC;
					__quad_setfsrp(&fsr);
				}
				QUAD_RETURN(Z);
			}
			/* zero / nonzero, return zero */
			Z.l.msw = sign;
			Z.l.frac2 = Z.l.frac3 = Z.l.frac4 = 0;
			QUAD_RETURN(Z);
		}
		if (QUAD_ISZERO(*y)) {
			/* nonzero / zero, signal zero divide */
			if (fsr & FSR_DZM) {
				__quad_fdivq(x, y, &Z);
			} else {
				Z.l.msw = sign | 0x7fff0000;
				Z.l.frac2 = Z.l.frac3 = Z.l.frac4 = 0;
				fsr = (fsr & ~FSR_CEXC) | FSR_DZA | FSR_DZC;
				__quad_setfsrp(&fsr);
			}
			QUAD_RETURN(Z);
		}
	}

	/* now x and y are finite, nonzero */
	__quad_setfsrp(&fsr_re);

	/* get their normalized significands and exponents */
	ex = (int)(xm >> 16);
	lx = xm & 0xffff;
	if (ex) {
		lx |= 0x10000;
		wx[0] = x->l.frac2;
		wx[1] = x->l.frac3;
		wx[2] = x->l.frac4;
	} else {
		if (lx | (x->l.frac2 & 0xfffe0000)) {
			wx[0] = x->l.frac2;
			wx[1] = x->l.frac3;
			wx[2] = x->l.frac4;
			ex = 1;
		} else if (x->l.frac2 | (x->l.frac3 & 0xfffe0000)) {
			lx = x->l.frac2;
			wx[0] = x->l.frac3;
			wx[1] = x->l.frac4;
			wx[2] = 0;
			ex = -31;
		} else if (x->l.frac3 | (x->l.frac4 & 0xfffe0000)) {
			lx = x->l.frac3;
			wx[0] = x->l.frac4;
			wx[1] = wx[2] = 0;
			ex = -63;
		} else {
			lx = x->l.frac4;
			wx[0] = wx[1] = wx[2] = 0;
			ex = -95;
		}
		while ((lx & 0x10000) == 0) {
			lx = (lx << 1) | (wx[0] >> 31);
			wx[0] = (wx[0] << 1) | (wx[1] >> 31);
			wx[1] = (wx[1] << 1) | (wx[2] >> 31);
			wx[2] <<= 1;
			ex--;
		}
	}
	ez = ex;

	ey = (int)(ym >> 16);
	ly = ym & 0xffff;
	if (ey) {
		ly |= 0x10000;
		wy[0] = y->l.frac2;
		wy[1] = y->l.frac3;
		wy[2] = y->l.frac4;
	} else {
		if (ly | (y->l.frac2 & 0xfffe0000)) {
			wy[0] = y->l.frac2;
			wy[1] = y->l.frac3;
			wy[2] = y->l.frac4;
			ey = 1;
		} else if (y->l.frac2 | (y->l.frac3 & 0xfffe0000)) {
			ly = y->l.frac2;
			wy[0] = y->l.frac3;
			wy[1] = y->l.frac4;
			wy[2] = 0;
			ey = -31;
		} else if (y->l.frac3 | (y->l.frac4 & 0xfffe0000)) {
			ly = y->l.frac3;
			wy[0] = y->l.frac4;
			wy[1] = wy[2] = 0;
			ey = -63;
		} else {
			ly = y->l.frac4;
			wy[0] = wy[1] = wy[2] = 0;
			ey = -95;
		}
		while ((ly & 0x10000) == 0) {
			ly = (ly << 1) | (wy[0] >> 31);
			wy[0] = (wy[0] << 1) | (wy[1] >> 31);
			wy[1] = (wy[1] << 1) | (wy[2] >> 31);
			wy[2] <<= 1;
			ey--;
		}
	}
	ez -= ey - 0x3fff;

	/* extract the significands into doubles */
	c = twom16;
	xx[0] = (double)((int)lx) * c;
	yy[0] = (double)((int)ly) * c;

	c *= twom24;
	xx[0] += (double)((int)(wx[0] >> 8)) * c;
	yy[1] = (double)((int)(wy[0] >> 8)) * c;

	c *= twom24;
	xx[1] = (double)((int)(((wx[0] << 16) |
	    (wx[1] >> 16)) & 0xffffff)) * c;
	yy[2] = (double)((int)(((wy[0] << 16) |
	    (wy[1] >> 16)) & 0xffffff)) * c;

	c *= twom24;
	xx[2] = (double)((int)(((wx[1] << 8) |
	    (wx[2] >> 24)) & 0xffffff)) * c;
	yy[3] = (double)((int)(((wy[1] << 8) |
	    (wy[2] >> 24)) & 0xffffff)) * c;

	c *= twom24;
	xx[3] = (double)((int)(wx[2] & 0xffffff)) * c;
	yy[4] = (double)((int)(wy[2] & 0xffffff)) * c;

	/* approximate the reciprocal of y */
	ry = one / ((yy[0] + yy[1]) + yy[2]);

	/* compute the first five "digits" of the quotient */
	zz[0] = (ry * (xx[0] + xx[1]) + three2p27) - three2p27;
	xx[0] = ((xx[0] - zz[0] * yy[0]) - zz[0] * yy[1]) + xx[1];
	d = zz[0] * yy[2];
	c = (d + three2m13) - three2m13;
	xx[0] -= c;
	xx[1] = xx[2] - (d - c);
	d = zz[0] * yy[3];
	c = (d + three2m37) - three2m37;
	xx[1] -= c;
	xx[2] = xx[3] - (d - c);
	d = zz[0] * yy[4];
	c = (d + three2m61) - three2m61;
	xx[2] -= c;
	xx[3] = c - d;

	zz[1] = (ry * (xx[0] + xx[1]) + three2p3) - three2p3;
	xx[0] = ((xx[0] - zz[1] * yy[0]) - zz[1] * yy[1]) + xx[1];
	d = zz[1] * yy[2];
	c = (d + three2m37) - three2m37;
	xx[0] -= c;
	xx[1] = xx[2] - (d - c);
	d = zz[1] * yy[3];
	c = (d + three2m61) - three2m61;
	xx[1] -= c;
	xx[2] = xx[3] - (d - c);
	d = zz[1] * yy[4];
	c = (d + three2m85) - three2m85;
	xx[2] -= c;
	xx[3] = c - d;

	zz[2] = (ry * (xx[0] + xx[1]) + three2m21) - three2m21;
	xx[0] = ((xx[0] - zz[2] * yy[0]) - zz[2] * yy[1]) + xx[1];
	d = zz[2] * yy[2];
	c = (d + three2m61) - three2m61;
	xx[0] -= c;
	xx[1] = xx[2] - (d - c);
	d = zz[2] * yy[3];
	c = (d + three2m85) - three2m85;
	xx[1] -= c;
	xx[2] = xx[3] - (d - c);
	d = zz[2] * yy[4];
	c = (d + three2m109) - three2m109;
	xx[2] -= c;
	xx[3] = c - d;

	zz[3] = (ry * (xx[0] + xx[1]) + three2m45) - three2m45;
	xx[0] = ((xx[0] - zz[3] * yy[0]) - zz[3] * yy[1]) + xx[1];
	d = zz[3] * yy[2];
	c = (d + three2m85) - three2m85;
	xx[0] -= c;
	xx[1] = xx[2] - (d - c);
	d = zz[3] * yy[3];
	c = (d + three2m109) - three2m109;
	xx[1] -= c;
	xx[2] = xx[3] - (d - c);
	d = zz[3] * yy[4];
	c = (d + three2m133) - three2m133;
	xx[2] -= c;
	xx[3] = c - d;

	zz[4] = (ry * (xx[0] + xx[1]) + three2m73) - three2m73;

	/* reduce to three doubles, making sure zz[1] is positive */
	zz[0] += zz[1] - twom48;
	zz[1] = twom48 + zz[2] + zz[3];
	zz[2] = zz[4];

	/* if the third term might lie on a rounding boundary, perturb it */
	if (zz[2] == (twom62 + zz[2]) - twom62) {
		/* here we just need to get the sign of the remainder */
		c = (((((xx[0] - zz[4] * yy[0]) - zz[4] * yy[1]) + xx[1]) +
		    (xx[2] - zz[4] * yy[2])) + (xx[3] - zz[4] * yy[3]))
		    - zz[4] * yy[4];
		if (c < zero)
			zz[2] -= twom124;
		else if (c > zero)
			zz[2] += twom124;
	}

	/*
	 * propagate carries/borrows, using round-to-negative-infinity mode
	 * to make all terms nonnegative (note that we can't encounter a
	 * borrow so large that the roundoff is unrepresentable because
	 * we took care to make zz[1] positive above)
	 */
	__quad_setfsrp(&fsr_rn);
	c = zz[1] + zz[2];
	zz[2] += (zz[1] - c);
	zz[1] = c;
	c = zz[0] + zz[1];
	zz[1] += (zz[0] - c);
	zz[0] = c;

	/* check for borrow */
	if (c < one) {
		/* postnormalize */
		zz[0] += zz[0];
		zz[1] += zz[1];
		zz[2] += zz[2];
		ez--;
	}

	/* if exponent > 0 strip off integer bit, else denormalize */
	if (ez > 0) {
		ibit = 1;
		zz[0] -= one;
	} else {
		ibit = 0;
		if (ez > -128)
			u.l.hi = (unsigned int)(0x3fe + ez) << 20;
		else
			u.l.hi = 0x37e00000;
		u.l.lo = 0;
		zz[0] *= u.d;
		zz[1] *= u.d;
		zz[2] *= u.d;
		ez = 0;
	}

	/* the first 48 bits of fraction come from zz[0] */
	u.d = d = two36 + zz[0];
	msw = u.l.lo;
	zz[0] -= (d - two36);

	u.d = d = two4 + zz[0];
	frac2 = u.l.lo;
	zz[0] -= (d - two4);

	/* the next 32 come from zz[0] and zz[1] */
	u.d = d = twom28 + (zz[0] + zz[1]);
	frac3 = u.l.lo;
	zz[0] -= (d - twom28);

	/* condense the remaining fraction; errors here won't matter */
	c = zz[0] + zz[1];
	zz[1] = ((zz[0] - c) + zz[1]) + zz[2];
	zz[0] = c;

	/* get the last word of fraction */
	u.d = d = twom60 + (zz[0] + zz[1]);
	frac4 = u.l.lo;
	zz[0] -= (d - twom60);

	/* keep track of what's left for rounding; note that the error */
	/* in computing c will be non-negative due to rounding mode */
	c = zz[0] + zz[1];

	/* get the rounding mode, fudging directed rounding modes */
	/* as though the result were positive */
	rm = fsr >> 30;
	if (sign)
		rm ^= (rm >> 1);

	/* round and raise exceptions */
	fsr &= ~FSR_CEXC;
	if (c != zero) {
		fsr |= FSR_NXC;

		/* decide whether to round the fraction up */
		if (rm == FSR_RP || (rm == FSR_RN && (c > twom113 ||
		    (c == twom113 && ((frac4 & 1) || (c - zz[0] !=
		    zz[1])))))) {
			/* round up and renormalize if necessary */
			if (++frac4 == 0)
				if (++frac3 == 0)
					if (++frac2 == 0)
						if (++msw == 0x10000) {
							msw = 0;
							ez++;
						}
		}
	}

	/* check for under/overflow */
	if (ez >= 0x7fff) {
		if (rm == FSR_RN || rm == FSR_RP) {
			z.l.msw = sign | 0x7fff0000;
			z.l.frac2 = z.l.frac3 = z.l.frac4 = 0;
		} else {
			z.l.msw = sign | 0x7ffeffff;
			z.l.frac2 = z.l.frac3 = z.l.frac4 = 0xffffffff;
		}
		fsr |= FSR_OFC | FSR_NXC;
	} else {
		z.l.msw = sign | (ez << 16) | msw;
		z.l.frac2 = frac2;
		z.l.frac3 = frac3;
		z.l.frac4 = frac4;

		/* !ibit => exact result was tiny before rounding, */
		/* t nonzero => result delivered is inexact */
		if (!ibit) {
			if (c != zero)
				fsr |= FSR_UFC | FSR_NXC;
			else if (fsr & FSR_UFM)
				fsr |= FSR_UFC;
		}
	}

	if ((fsr & FSR_CEXC) & (fsr >> 23)) {
		__quad_setfsrp(&fsr);
		__quad_fdivq(x, y, &Z);
	} else {
		Z = z;
		fsr |= (fsr & 0x1f) << 5;
		__quad_setfsrp(&fsr);
	}
	QUAD_RETURN(Z);
}