lib/libc/gen/floatunditf_ieee754.c

   1 /*      $NetBSD: floatunditf_ieee754.c,v 1.1 2014/01/30 15:06:18 joerg Exp $    */
   2
   3 /*-
   4  * Copyright (c) 2014 Joerg Sonnenberger <joerg@NetBSD.org>.
   5  * All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  *
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in
  15  *    the documentation and/or other materials provided with the
  16  *    distribution.
  17  *
  18  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  19  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  20  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  21  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
  22  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  23  * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
  24  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  25  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
  26  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  27  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  28  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  29  * SUCH DAMAGE.
  30  */
  31
  32 #include <sys/cdefs.h>
  33 __RCSID("$NetBSD: floatunditf_ieee754.c,v 1.1 2014/01/30 15:06:18 joerg Exp $");
  34
  35 #include <math.h>
  36 #include <machine/ieee.h>
  37 #include <limits.h>
  38
  39 #ifdef __HAVE_LONG_DOUBLE
  40
  41 long double __floatunditf(uint64_t x);
  42
  43 /*
  44  * Convert uint64_t to long double.
  45  */
  46 long double
  47 __floatunditf(uint64_t x)
  48 {
  49         int exponent, zeros;
  50         union ieee_ext_u ux;
  51
  52         /* Use the easier conversion routine for uint32_t if possible. */
  53         if (x <= UINT32_MAX)
  54                 return (long double)(uint32_t)x;
  55
  56         zeros = __builtin_clzll(x);
  57 #ifdef LDBL_IMPLICIT_NBIT
  58         exponent = 64 - zeros;
  59         x <<= zeros + 1;
  60 #else
  61         exponent = 63 - zeros;
  62         x <<= zeros;
  63 #endif
  64
  65         ux.extu_exp = EXT_EXP_BIAS + exponent;
  66         ux.extu_frach = (x >> (64 - EXT_FRACHBITS));
  67         x <<= EXT_FRACHBITS;
  68 #ifdef EXT_FRACHMBITS
  69         ux.extu_frachm = (x >> (64 - EXT_FRACHMBITS));
  70         x <<= EXT_FRACHMBITS;
  71 #endif
  72 #ifdef EXT_FRACLMBITS
  73         ux.extu_fraclm = (x >> (64 - EXT_FRACLMBITS));
  74         x <<= EXT_FRACLMBITS;
  75 #endif
  76         ux.extu_fracl = (x >> (64 - EXT_FRACLBITS));
  77         ux.extu_sign = 0;
  78
  79         return ux.extu_ld;
  80 }
  81 #endif /* __HAVE_LONG_DOUBLE */