lib/libm/src/s_nextafterf.c

   1 /* s_nextafterf.c -- float version of s_nextafter.c.
   2  * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
   3  */
   4
   5 /*
   6  * ====================================================
   7  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   8  *
   9  * Developed at SunPro, a Sun Microsystems, Inc. business.
  10  * Permission to use, copy, modify, and distribute this
  11  * software is freely granted, provided that this notice
  12  * is preserved.
  13  * ====================================================
  14  *
  15  * $NetBSD: s_nextafterf.c,v 1.8 2011/04/18 15:59:09 drochner Exp $
  16  */
  17
  18 #include <math.h>
  19 #include "math_private.h"
  20
  21 float
  22 nextafterf(float x, float y)
  23 {
  24         int32_t hx,hy,ix,iy;
  25
  26         GET_FLOAT_WORD(hx,x);
  27         GET_FLOAT_WORD(hy,y);
  28         ix = hx&0x7fffffff;             /* |x| */
  29         iy = hy&0x7fffffff;             /* |y| */
  30
  31         if((ix>0x7f800000) ||   /* x is nan */
  32            (iy>0x7f800000))     /* y is nan */
  33            return x+y;
  34         if(x==y) return y;              /* x=y, return y */
  35         if(ix==0) {                             /* x == 0 */
  36             SET_FLOAT_WORD(x,(hy&0x80000000)|1);/* return +-minsubnormal */
  37             y = x*x;
  38             if(y==x) return y; else return x;   /* raise underflow flag */
  39         }
  40         if(hx>=0) {                             /* x > 0 */
  41             if(hx>hy) {                         /* x > y, x -= ulp */
  42                 hx -= 1;
  43             } else {                            /* x < y, x += ulp */
  44                 hx += 1;
  45             }
  46         } else {                                /* x < 0 */
  47             if(hy>=0||hx>hy){                   /* x < y, x -= ulp */
  48                 hx -= 1;
  49             } else {                            /* x > y, x += ulp */
  50                 hx += 1;
  51             }
  52         }
  53         hy = hx&0x7f800000;
  54         if(hy>=0x7f800000) return x+x;  /* overflow  */
  55         if(hy<0x00800000) {             /* underflow */
  56             y = x*x;
  57             if(y!=x) {          /* raise underflow flag */
  58                 SET_FLOAT_WORD(y,hx);
  59                 return y;
  60             }
  61         }
  62         SET_FLOAT_WORD(x,hx);
  63         return x;
  64 }