1  /*
       2   * inspired by glibc-2.0.6/sysdeps/libm-ieee754/s_nextafterf.c
       3   *
       4   * gcc -O2 -S -DOP=+ gives faddp %st(1),%st
       5   * gcc -O2 -S -DOP=* gives fmulp %st(1),%st
       6   * gcc -O2 -S -DOP=- gives fsubrp %st(1),%st
       7   * gcc -O2 -S -DOP=/ gives fdivrp %st(1),%st
       8   */
       9  
      10  #ifndef OP
      11  #define OP *
      12  #endif
      13  
      14  typedef int int32_t __attribute__ ((__mode__ (  __SI__ ))) ;
      15  typedef unsigned int u_int32_t __attribute__ ((__mode__ (  __SI__ ))) ;
      16  
      17  typedef union
      18  {
      19    float value;
      20    u_int32_t word;
      21  } ieee_float_shape_type;
      22  
      23  float __nextafterf(float x, float y)
      24  {
      25   int32_t hx,hy,ix,iy;
      26  
      27   {
      28    ieee_float_shape_type gf_u;
      29    gf_u.value = x;
      30    hx = gf_u.word;
      31   }
      32   {
      33    ieee_float_shape_type gf_u;
      34    gf_u.value = y;
      35    hy = gf_u.word;
      36   }
      37   ix = hx&0x7fffffff;
      38   iy = hy&0x7fffffff;
      39  
      40   if ( ix > 0x7f800000 || iy > 0x7f800000 )
      41      return x+y;
      42   if (x == y) return x;
      43   if (ix == 0)
      44     {
      45      {
      46       ieee_float_shape_type sf_u;
      47       sf_u.word = (hy&0x80000000) | 1;
      48       x = sf_u.value;
      49      }
      50      y = x*x;
      51      if (y == x) return y; else return x;
      52     }
      53   if (hx >= 0)
      54     {
      55      if (hx > hy)
      56         hx -= 1;
      57      else
      58         hx += 1;
      59     }
      60   else
      61     {
      62      if (hy >= 0 || hx > hy)
      63         hx -= 1;
      64      else
      65         hx += 1;
      66     }
      67   hy = hx & 0x7f800000;
      68   if (hy >= 0x7f800000)
      69      return x+x;
      70   if (hy < 0x00800000)
      71     {
      72      y = x OP x;
      73      if (y != x)
      74        {
      75         ieee_float_shape_type sf_u;
      76         sf_u.word = hx;
      77         y = sf_u.value;
      78         return y;
      79        }
      80     }
      81   {
      82    ieee_float_shape_type sf_u;
      83    sf_u.word = hx;
      84    x = sf_u.value;
      85   }
      86   return x;
      87  }
      88  
      89