1  /* s_nexttoward.c
       2   * Special i387 version
       3   * Conversion from s_nextafter.c by Ulrich Drepper, Cygnus Support,
       4   * drepper@cygnus.com.
       5   */
       6  
       7  /*
       8   * ====================================================
       9   * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
      10   *
      11   * Developed at SunPro, a Sun Microsystems, Inc. business.
      12   * Permission to use, copy, modify, and distribute this
      13   * software is freely granted, provided that this notice
      14   * is preserved.
      15   * ====================================================
      16   */
      17  
      18  #if defined(LIBM_SCCS) && !defined(lint)
      19  static char rcsid[] = "$NetBSD: $";
      20  #endif
      21  
      22  /* IEEE functions
      23   *	nexttoward(x,y)
      24   *	return the next machine floating-point number of x in the
      25   *	direction toward y.
      26   *   Special cases:
      27   */
      28  
      29  #include <errno.h>
      30  #include <math.h>
      31  #include <math-barriers.h>
      32  #include <math_private.h>
      33  #include <float.h>
      34  
      35  double __nexttoward(double x, long double y)
      36  {
      37  	int32_t hx,ix,iy;
      38  	uint32_t lx,hy,ly,esy;
      39  
      40  	EXTRACT_WORDS(hx,lx,x);
      41  	GET_LDOUBLE_WORDS(esy,hy,ly,y);
      42  	ix = hx&0x7fffffff;		/* |x| */
      43  	iy = esy&0x7fff;		/* |y| */
      44  
      45  	/* Intel's extended format has the normally implicit 1 explicit
      46  	   present.  Sigh!  */
      47  	if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) ||   /* x is nan */
      48  	   ((iy>=0x7fff)&&((hy&0x7fffffff)|ly)!=0))        /* y is nan */
      49  	   return x+y;
      50  	if((long double) x==y) return y;	/* x=y, return y */
      51  	if((ix|lx)==0) {			/* x == 0 */
      52  	    double u;
      53  	    INSERT_WORDS(x,(esy&0x8000)<<16,1); /* return +-minsub */
      54  	    u = math_opt_barrier (x);
      55  	    u = u * u;
      56  	    math_force_eval (u);		/* raise underflow flag */
      57  	    return x;
      58  	}
      59  	if(hx>=0) {				/* x > 0 */
      60  	    if (x > y) {			/* x -= ulp */
      61  		if(lx==0) hx -= 1;
      62  		lx -= 1;
      63  	    } else {				/* x < y, x += ulp */
      64  		lx += 1;
      65  		if(lx==0) hx += 1;
      66  	    }
      67  	} else {				/* x < 0 */
      68  	    if (x < y) {			/* x -= ulp */
      69  		if(lx==0) hx -= 1;
      70  		lx -= 1;
      71  	    } else {				/* x > y, x += ulp */
      72  		lx += 1;
      73  		if(lx==0) hx += 1;
      74  	    }
      75  	}
      76  	hy = hx&0x7ff00000;
      77  	if(hy>=0x7ff00000) {
      78  	  double u = x+x;			/* overflow  */
      79  	  math_force_eval (u);
      80  	  __set_errno (ERANGE);
      81  	}
      82  	if(hy<0x00100000) {
      83  	    double u = x*x;			/* underflow */
      84  	    math_force_eval (u);		/* raise underflow flag */
      85  	    __set_errno (ERANGE);
      86  	}
      87  	INSERT_WORDS(x,hx,lx);
      88  	return x;
      89  }
      90  weak_alias (__nexttoward, nexttoward)
      91  #ifdef NO_LONG_DOUBLE
      92  strong_alias (__nexttoward, __nexttowardl)
      93  weak_alias (__nexttoward, nexttowardl)
      94  #endif