e_fmodf.c

/* e_fmodf.c -- float version of e_fmod.c.
 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
 */

/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunPro, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice
 * is preserved.
 * ====================================================
 */

/*
 * __ieee754_fmodf(x,y)
 * Return x mod y in exact arithmetic
 * Method: shift and subtract
 */

#ifndef __FDLIBM_H__
#include "fdlibm.h"
#endif

#ifndef __have_fpu_fmod

float __ieee754_fmodf(float x, float y)
{
	int32_t n, hx, hy, hz, ix, iy, sx, i;

	static const float one = 1.0;
	static const float Zero[] = { 0.0, -0.0 };

	GET_FLOAT_WORD(hx, x);
	GET_FLOAT_WORD(hy, y);
	sx = hx & IC(0x80000000);			/* sign of x */
	hx ^= sx;							/* |x| */
	hy &= IC(0x7fffffff);				/* |y| */

	/* purge off exception values */
	if (hy == 0 || (hx >= IC(0x7f800000)) ||	/* y=0,or x not finite */
		(hy > IC(0x7f800000)))				/* or y is NaN */
		return (x * y) / (x * y);
	if (hx < hy)
		return x;						/* |x|<|y| return x */
	if (hx == hy)
		return Zero[(uint32_t) sx >> 31];	/* |x|=|y| return x*0 */

	/* determine ix = ilogb(x) */
	if (hx < IC(0x00800000))
	{									/* subnormal x */
		for (ix = -126, i = (hx << 8); i > 0; i <<= 1)
			ix -= 1;
	} else
		ix = (hx >> 23) - 127;

	/* determine iy = ilogb(y) */
	if (hy < IC(0x00800000))
	{									/* subnormal y */
		for (iy = -126, i = (hy << 8); i >= 0; i <<= 1)
			iy -= 1;
	} else
		iy = (hy >> 23) - 127;

	/* set up {hx,lx}, {hy,ly} and align y to x */
	if (ix >= -126)
		hx = IC(0x00800000) | (IC(0x007fffff) & hx);
	else
	{									/* subnormal x, shift x to normal */
		n = -126 - ix;
		hx = hx << n;
	}
	if (iy >= -126)
		hy = IC(0x00800000) | (IC(0x007fffff) & hy);
	else
	{									/* subnormal y, shift y to normal */
		n = -126 - iy;
		hy = hy << n;
	}

	/* fix point fmod */
	n = ix - iy;
	while (n--)
	{
		hz = hx - hy;
		if (hz < 0)
		{
			hx = hx + hx;
		} else
		{
			if (hz == 0)				/* return sign(x)*0 */
				return Zero[(uint32_t) sx >> 31];
			hx = hz + hz;
		}
	}
	hz = hx - hy;
	if (hz >= 0)
	{
		hx = hz;
	}

	/* convert back to floating value and restore the sign */
	if (hx == 0)						/* return sign(x)*0 */
		return Zero[(uint32_t) sx >> 31];
	while (hx < IC(0x00800000))
	{									/* normalize x */
		hx = hx + hx;
		iy -= 1;
	}
	if (iy >= -126)
	{									/* normalize output */
		hx = ((hx - IC(0x00800000)) | ((iy + 127) << 23));
		SET_FLOAT_WORD(x, hx | sx);
	} else
	{									/* subnormal output */
		n = -126 - iy;
		hx >>= n;
		SET_FLOAT_WORD(x, hx | sx);
		x *= one;						/* create necessary signal */
	}
	return x;							/* exact output */
}

#endif

float __fmodf(float x, float y)
{
	if ((isinf(x) || y == 0.0F) && _LIB_VERSION != _IEEE_ && !isunordered(x, y))
		/* fmod(+-Inf,y) or fmod(x,0) */
		return __kernel_standard_f(x, y, y, KMATHERRF_FMOD);
	return __ieee754_fmodf(x, y);
}

__typeof(__fmodf) fmodf __attribute__((weak, alias("__fmodf")));