nsz Git - musl/blob - src/math/floorf.c

   1 /* origin: FreeBSD /usr/src/lib/msun/src/s_floorf.c */
   2 /*
   3  * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
   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  * floorf(x)
  17  * Return x rounded toward -inf to integral value
  18  * Method:
  19  *      Bit twiddling.
  20  * Exception:
  21  *      Inexact flag raised if x not equal to floorf(x).
  22  */
  23
  24 #include "libm.h"
  25
  26 static const float huge = 1.0e30;
  27
  28 float floorf(float x)
  29 {
  30         int32_t i0,j0;
  31         uint32_t i;
  32
  33         GET_FLOAT_WORD(i0, x);
  34         // FIXME: signed shift
  35         j0 = ((i0>>23)&0xff) - 0x7f;
  36         if (j0 < 23) {
  37                 if (j0 < 0) {  /* |x| < 1 */
  38                         /* raise inexact if x != 0 */
  39                         if (huge+x > (float)0.0) {
  40                                 if (i0 >= 0)  /* x >= 0 */
  41                                         i0 = 0;
  42                                 else if ((i0&0x7fffffff) != 0)
  43                                         i0 = 0xbf800000;
  44                         }
  45                 } else {
  46                         i = 0x007fffff>>j0;
  47                         if ((i0&i) == 0)
  48                                 return x; /* x is integral */
  49                         /* raise inexact flag */
  50                         if (huge+x > (float)0.0) {
  51                                 if (i0 < 0)
  52                                         i0 += 0x00800000>>j0;
  53                                 i0 &= ~i;
  54                         }
  55                 }
  56         } else {
  57                 if (j0 == 0x80)  /* inf or NaN */
  58                         return x+x;
  59                 else
  60                         return x;  /* x is integral */
  61         }
  62         SET_FLOAT_WORD(x, i0);
  63         return x;
  64 }