sysdeps/ieee754/dbl-64/s_ceil.c

   1 /* @(#)s_ceil.c 5.1 93/09/24 */
   2 /*
   3  * ====================================================
   4  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   5  *
   6  * Developed at SunPro, a Sun Microsystems, Inc. business.
   7  * Permission to use, copy, modify, and distribute this
   8  * software is freely granted, provided that this notice
   9  * is preserved.
  10  * ====================================================
  11  */
  12
  13 /*
  14  * ceil(x)
  15  * Return x rounded toward -inf to integral value
  16  * Method:
  17  *      Bit twiddling.
  18  */
  19
  20 #define NO_MATH_REDIRECT
  21 #include <math.h>
  22 #include <math_private.h>
  23 #include <libm-alias-double.h>
  24 #include <math-use-builtins.h>
  25
  26 double
  27 __ceil (double x)
  28 {
  29 #if USE_CEIL_BUILTIN
  30   return __builtin_ceil (x);
  31 #else
  32   /* Use generic implementation.  */
  33   int64_t i0, i;
  34   int32_t j0;
  35   EXTRACT_WORDS64 (i0, x);
  36   j0 = ((i0 >> 52) & 0x7ff) - 0x3ff;
  37   if (j0 <= 51)
  38     {
  39       if (j0 < 0)
  40         {
  41           /* return 0 * sign(x) if |x| < 1  */
  42           if (i0 < 0)
  43             i0 = INT64_C (0x8000000000000000);
  44           else if (i0 != 0)
  45             i0 = INT64_C (0x3ff0000000000000);
  46         }
  47       else
  48         {
  49           i = INT64_C (0x000fffffffffffff) >> j0;
  50           if ((i0 & i) == 0)
  51             return x;                   /* x is integral  */
  52           if (i0 > 0)
  53             i0 += UINT64_C (0x0010000000000000) >> j0;
  54           i0 &= ~i;
  55         }
  56     }
  57   else
  58     {
  59       if (j0 == 0x400)
  60         return x + x;                   /* inf or NaN  */
  61       else
  62         return x;                       /* x is integral  */
  63     }
  64   INSERT_WORDS64 (x, i0);
  65   return x;
  66 #endif /* ! USE_CEIL_BUILTIN  */
  67 }
  68 #ifndef __ceil
  69 libm_alias_double (__ceil, ceil)
  70 #endif