src/libm/e_fmod.c
author Ryan C. Gordon <icculus@icculus.org>
Mon, 21 May 2018 12:00:21 -0400
changeset 11994 8e094f91ddab
parent 11685 1788f503254d
permissions -rw-r--r--
thread: fixed compiler warnings on non-Linux systems that use pthread.

(static function rtkit_setpriority was unused, moved it in with rest of
__LINUX__ section.)
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/*
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 * ====================================================
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 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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 *
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 * Developed at SunPro, a Sun Microsystems, Inc. business.
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 * Permission to use, copy, modify, and distribute this
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 * software is freely granted, provided that this notice
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 * is preserved.
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 * ====================================================
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 */
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/*
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 * __ieee754_fmod(x,y)
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 * Return x mod y in exact arithmetic
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 * Method: shift and subtract
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 */
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#include "math_libm.h"
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#include "math_private.h"
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static const double one = 1.0, Zero[] = {0.0, -0.0,};
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double attribute_hidden __ieee754_fmod(double x, double y)
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{
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	int32_t n,hx,hy,hz,ix,iy,sx,i;
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	u_int32_t lx,ly,lz;
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	EXTRACT_WORDS(hx,lx,x);
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	EXTRACT_WORDS(hy,ly,y);
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	sx = hx&0x80000000;		/* sign of x */
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	hx ^=sx;		/* |x| */
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	hy &= 0x7fffffff;	/* |y| */
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    /* purge off exception values */
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	if((hy|ly)==0||(hx>=0x7ff00000)||	/* y=0,or x not finite */
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	  ((hy|((ly|-(int32_t)ly)>>31))>0x7ff00000))	/* or y is NaN */
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	    return (x*y)/(x*y);
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	if(hx<=hy) {
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	    if((hx<hy)||(lx<ly)) return x;	/* |x|<|y| return x */
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	    if(lx==ly)
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		return Zero[(u_int32_t)sx>>31];	/* |x|=|y| return x*0*/
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	}
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    /* determine ix = ilogb(x) */
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	if(hx<0x00100000) {	/* subnormal x */
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	    if(hx==0) {
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		for (ix = -1043, i=lx; i>0; i<<=1) ix -=1;
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	    } else {
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		for (ix = -1022,i=(hx<<11); i>0; i<<=1) ix -=1;
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	    }
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	} else ix = (hx>>20)-1023;
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    /* determine iy = ilogb(y) */
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	if(hy<0x00100000) {	/* subnormal y */
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	    if(hy==0) {
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		for (iy = -1043, i=ly; i>0; i<<=1) iy -=1;
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	    } else {
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		for (iy = -1022,i=(hy<<11); i>0; i<<=1) iy -=1;
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	    }
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	} else iy = (hy>>20)-1023;
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    /* set up {hx,lx}, {hy,ly} and align y to x */
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	if(ix >= -1022)
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	    hx = 0x00100000|(0x000fffff&hx);
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	else {		/* subnormal x, shift x to normal */
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	    n = -1022-ix;
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	    if(n<=31) {
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	        hx = (hx<<n)|(lx>>(32-n));
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	        lx <<= n;
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	    } else {
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		hx = lx<<(n-32);
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		lx = 0;
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	    }
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	}
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	if(iy >= -1022)
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	    hy = 0x00100000|(0x000fffff&hy);
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	else {		/* subnormal y, shift y to normal */
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	    n = -1022-iy;
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	    if(n<=31) {
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	        hy = (hy<<n)|(ly>>(32-n));
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	        ly <<= n;
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	    } else {
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		hy = ly<<(n-32);
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		ly = 0;
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	    }
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	}
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    /* fix point fmod */
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	n = ix - iy;
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	while(n--) {
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	    hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1;
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	    if(hz<0){hx = hx+hx+(lx>>31); lx = lx+lx;}
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	    else {
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	    	if((hz|lz)==0) 		/* return sign(x)*0 */
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		    return Zero[(u_int32_t)sx>>31];
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	    	hx = hz+hz+(lz>>31); lx = lz+lz;
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	    }
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	}
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	hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1;
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	if(hz>=0) {hx=hz;lx=lz;}
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    /* convert back to floating value and restore the sign */
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	if((hx|lx)==0) 			/* return sign(x)*0 */
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	    return Zero[(u_int32_t)sx>>31];
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	while(hx<0x00100000) {		/* normalize x */
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	    hx = hx+hx+(lx>>31); lx = lx+lx;
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	    iy -= 1;
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	}
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	if(iy>= -1022) {	/* normalize output */
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	    hx = ((hx-0x00100000)|((iy+1023)<<20));
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	    INSERT_WORDS(x,hx|sx,lx);
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	} else {		/* subnormal output */
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	    n = -1022 - iy;
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	    if(n<=20) {
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		lx = (lx>>n)|((u_int32_t)hx<<(32-n));
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		hx >>= n;
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	    } else if (n<=31) {
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		lx = (hx<<(32-n))|(lx>>n); hx = sx;
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	    } else {
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		lx = hx>>(n-32); hx = sx;
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	    }
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	    INSERT_WORDS(x,hx|sx,lx);
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	    x *= one;		/* create necessary signal */
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	}
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	return x;		/* exact output */
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}
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/*
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 * wrapper fmod(x,y)
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 */
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#ifndef _IEEE_LIBM
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double fmod(double x, double y)
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{
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	double z = __ieee754_fmod(x, y);
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	if (_LIB_VERSION == _IEEE_ || isnan(y) || isnan(x))
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		return z;
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	if (y == 0.0)
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		return __kernel_standard(x, y, 27); /* fmod(x,0) */
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	return z;
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}
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#else
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strong_alias(__ieee754_fmod, fmod)
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#endif
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libm_hidden_def(fmod)