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  * $FreeBSD: head/lib/msun/src/s_nextafterf.c 176451 2008-02-22 02:30:36Z das $
  16  */
  17
  18 #include "math.h"
  19 #include "math_private.h"
  20
  21 float
  22 nextafterf(float x, float y)
  23 {
  24         volatile float t;
  25         int32_t hx,hy,ix,iy;
  26
  27         GET_FLOAT_WORD(hx,x);
  28         GET_FLOAT_WORD(hy,y);
  29         ix = hx&0x7fffffff;             /* |x| */
  30         iy = hy&0x7fffffff;             /* |y| */
  31
  32         if((ix>0x7f800000) ||   /* x is nan */
  33            (iy>0x7f800000))     /* y is nan */
  34            return x+y;
  35         if(x==y) return y;              /* x=y, return y */
  36         if(ix==0) {                             /* x == 0 */
  37             SET_FLOAT_WORD(x,(hy&0x80000000)|1);/* return +-minsubnormal */
  38             t = x*x;
  39             if(t==x) return t; else return x;   /* raise underflow flag */
  40         }
  41         if(hx>=0) {                             /* x > 0 */
  42             if(hx>hy) {                         /* x > y, x -= ulp */
  43                 hx -= 1;
  44             } else {                            /* x < y, x += ulp */
  45                 hx += 1;
  46             }
  47         } else {                                /* x < 0 */
  48             if(hy>=0||hx>hy){                   /* x < y, x -= ulp */
  49                 hx -= 1;
  50             } else {                            /* x > y, x += ulp */
  51                 hx += 1;
  52             }
  53         }
  54         hy = hx&0x7f800000;
  55         if(hy>=0x7f800000) return x+x;  /* overflow  */
  56         if(hy<0x00800000) {             /* underflow */
  57             t = x*x;
  58             if(t!=x) {          /* raise underflow flag */
  59                 SET_FLOAT_WORD(y,hx);
  60                 return y;
  61             }
  62         }
  63         SET_FLOAT_WORD(x,hx);
  64         return x;
  65 }