xref: /illumos-gate/usr/src/lib/libm/common/Q/fmodl.c (revision ddc0e0b5)

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (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 2011 Nexenta Systems, Inc.  All rights reserved.
 */
/*
 * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#pragma weak __fmodl = fmodl

#include "libm.h"

static const int
	is = -0x7fffffff - 1,
	im = 0x0000ffff,
	iu = 0x00010000;

static const long double
	zero = 0.0L,
	one = 1.0L;

#ifdef __LITTLE_ENDIAN
#define	__H0(x) *(3 + (int *) &x)
#define	__H1(x) *(2 + (int *) &x)
#define	__H2(x) *(1 + (int *) &x)
#define	__H3(x) *(0 + (int *) &x)
#else
#define	__H0(x) *(0 + (int *) &x)
#define	__H1(x) *(1 + (int *) &x)
#define	__H2(x) *(2 + (int *) &x)
#define	__H3(x) *(3 + (int *) &x)
#endif

long double
fmodl(long double x, long double y) {
	long double a, b;
	int n, ix, iy, k, sx;
	int hx;
	int x0, y0, z0, carry;
	unsigned x1, x2, x3, y1, y2, y3, z1, z2, z3;

	hx = __H0(x);
	x1 = __H1(x);
	x2 = __H2(x);
	x3 = __H3(x);
	y0 = __H0(y);
	y1 = __H1(y);
	y2 = __H2(y);
	y3 = __H3(y);

	sx = hx & 0x80000000;
	x0 = hx ^ sx;
	y0 &= 0x7fffffff;

	/* purge off exception values */
	if (x0 >= 0x7fff0000 ||	/* !finitel(x) */
	    (y0 > 0x7fff0000) || (y0 == 0x7fff0000 && ((y1 | y2 | y3) != 0)) ||
	    (y0 | y1 | y2 | y3) == 0)	/* isnanl(y) || y = 0 */
		return ((x * y) / (x * y));
	a = fabsl(x);
	b = fabsl(y);
	if (a <= b) {
		if (a < b)
			return (x);
		else
			return (zero * x);
	}
	/* determine ix = ilogbl(x) */
	if (x0 < iu) {		/* subnormal x */
		ix = -16382;
		while (x0 == 0) {
			ix -= 16;
			x0 = x1 >> 16;
			x1 = (x1 << 16) | (x2 >> 16);
			x2 = (x2 << 16) | (x3 >> 16);
			x3 = (x3 << 16);
		}
		while (x0 < iu) {
			ix -= 1;
			x0 = (x0 << 1) | (x1 >> 31);
			x1 = (x1 << 1) | (x2 >> 31);
			x2 = (x2 << 1) | (x3 >> 31);
			x3 <<= 1;
		}
	} else {
		ix = (x0 >> 16) - 16383;
		x0 = iu | (x0 & im);
	}

	/* determine iy = ilogbl(y) */
	if (y0 < iu) {		/* subnormal y */
		iy = -16382;
		while (y0 == 0) {
			iy -= 16;
			y0 = y1 >> 16;
			y1 = (y1 << 16) | (y2 >> 16);
			y2 = (y2 << 16) | (y3 >> 16);
			y3 = (y3 << 16);
		}
		while (y0 < iu) {
			iy -= 1;
			y0 = (y0 << 1) | (y1 >> 31);
			y1 = (y1 << 1) | (y2 >> 31);
			y2 = (y2 << 1) | (y3 >> 31);
			y3 <<= 1;
		}
	} else {
		iy = (y0 >> 16) - 16383;
		y0 = iu | (y0 & im);
	}

	/* fix point fmod */
	n = ix - iy;
	while (n--) {
		while (x0 == 0 && n >= 16) {
			n -= 16;
			x0 = x1 >> 16;
			x1 = (x1 << 16) | (x2 >> 16);
			x2 = (x2 << 16) | (x3 >> 16);
			x3 = (x3 << 16);
		}
		while (x0 < iu && n >= 1) {
			n -= 1;
			x0 = (x0 << 1) | (x1 >> 31);
			x1 = (x1 << 1) | (x2 >> 31);
			x2 = (x2 << 1) | (x3 >> 31);
			x3 = (x3 << 1);
		}
		carry = 0;
		z3 = x3 - y3;
		carry = (z3 > x3);
		if (carry == 0) {
			z2 = x2 - y2;
			carry = (z2 > x2);
		} else {
			z2 = x2 - y2 - 1;
			carry = (z2 >= x2);
		}
		if (carry == 0) {
			z1 = x1 - y1;
			carry = (z1 > x1);
		} else {
			z1 = x1 - y1 - 1;
			carry = (z1 >= x1);
		}
		z0 = x0 - y0 - carry;
		if (z0 < 0) {	/* double x */
			x0 = x0 + x0 + ((x1 & is) != 0);
			x1 = x1 + x1 + ((x2 & is) != 0);
			x2 = x2 + x2 + ((x3 & is) != 0);
			x3 = x3 + x3;
		} else {
			if (z0 == 0) {
				if ((z1 | z2 | z3) == 0) {	/* 0: done */
					__H0(a) = hx & is;
					__H1(a) = __H2(a) = __H3(a) = 0;
					return (a);
				}
			}
			/* x = z << 1 */
			z0 = z0 + z0 + ((z1 & is) != 0);
			z1 = z1 + z1 + ((z2 & is) != 0);
			z2 = z2 + z2 + ((z3 & is) != 0);
			z3 = z3 + z3;
			x0 = z0;
			x1 = z1;
			x2 = z2;
			x3 = z3;
		}
	}

	carry = 0;
	z3 = x3 - y3;
	carry = (z3 > x3);
	if (carry == 0) {
		z2 = x2 - y2;
		carry = (z2 > x2);
	} else {
		z2 = x2 - y2 - 1;
		carry = (z2 >= x2);
	}
	if (carry == 0) {
		z1 = x1 - y1;
		carry = (z1 > x1);
	} else {
		z1 = x1 - y1 - 1;
		carry = (z1 >= x1);
	}
	z0 = x0 - y0 - carry;
	if (z0 >= 0) {
		x0 = z0;
		x1 = z1;
		x2 = z2;
		x3 = z3;
	}
	/* convert back to floating value and restore the sign */
	if ((x0 | x1 | x2 | x3) == 0) {
		__H0(a) = hx & is;
		__H1(a) = __H2(a) = __H3(a) = 0;
		return (a);
	}
	while (x0 < iu) {
		if (x0 == 0) {
			iy -= 16;
			x0 = x1 >> 16;
			x1 = (x1 << 16) | (x2 >> 16);
			x2 = (x2 << 16) | (x3 >> 16);
			x3 = (x3 << 16);
		} else {
			x0 = x0 + x0 + ((x1 & is) != 0);
			x1 = x1 + x1 + ((x2 & is) != 0);
			x2 = x2 + x2 + ((x3 & is) != 0);
			x3 = x3 + x3;
			iy -= 1;
		}
	}

	/* normalize output */
	if (iy >= -16382) {
		__H0(a) = sx | (x0 - iu) | ((iy + 16383) << 16);
		__H1(a) = x1;
		__H2(a) = x2;
		__H3(a) = x3;
	} else {		/* subnormal output */
		n = -16382 - iy;
		k = n & 31;
		if (k != 0) {
			if (k <= 16) {
				x3 = (x2 << (32 - k)) | (x3 >> k);
				x2 = (x1 << (32 - k)) | (x2 >> k);
				x1 = (x0 << (32 - k)) | (x1 >> k);
				x0 >>= k;
			} else {
				x3 = (x2 << (32 - k)) | (x3 >> k);
				x2 = (x1 << (32 - k)) | (x2 >> k);
				x1 = (x0 << (32 - k)) | (x1 >> k);
				x0 = 0;
			}
		}
		while (n >= 32) {
			n -= 32;
			x3 = x2;
			x2 = x1;
			x1 = x0;
			x0 = 0;
		}
		__H0(a) = x0 | sx;
		__H1(a) = x1;
		__H2(a) = x2;
		__H3(a) = x3;
		a *= one;
	}
	return (a);
}