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
  16 #include "math.h"
  17 #include "math_private.h"
  18
  19 float
  20 nextafterf(float x, float y)
  21 {
  22         int32_t hx,hy,ix,iy;
  23
  24         GET_FLOAT_WORD(hx,x);
  25         GET_FLOAT_WORD(hy,y);
  26         ix = hx&0x7fffffff;             /* |x| */
  27         iy = hy&0x7fffffff;             /* |y| */
  28
  29         if((ix>0x7f800000) ||   /* x is nan */
  30            (iy>0x7f800000))     /* y is nan */
  31            return x+y;
  32         if(x==y) return y;              /* x=y, return y */
  33         if(ix==0) {                             /* x == 0 */
  34             SET_FLOAT_WORD(x,(hy&0x80000000)|1);/* return +-minsubnormal */
  35             y = x*x;
  36             if(y==x) return y; else return x;   /* raise underflow flag */
  37         }
  38         if(hx>=0) {                             /* x > 0 */
  39             if(hx>hy) {                         /* x > y, x -= ulp */
  40                 hx -= 1;
  41             } else {                            /* x < y, x += ulp */
  42                 hx += 1;
  43             }
  44         } else {                                /* x < 0 */
  45             if(hy>=0||hx>hy){                   /* x < y, x -= ulp */
  46                 hx -= 1;
  47             } else {                            /* x > y, x += ulp */
  48                 hx += 1;
  49             }
  50         }
  51         hy = hx&0x7f800000;
  52         if(hy>=0x7f800000) return x+x;  /* overflow  */
  53         if(hy<0x00800000) {             /* underflow */
  54             y = x*x;
  55             if(y!=x) {          /* raise underflow flag */
  56                 SET_FLOAT_WORD(y,hx);
  57                 return y;
  58             }
  59         }
  60         SET_FLOAT_WORD(x,hx);
  61         return x;
  62 }