lib/libc/gen/floatunsidf_ieee754.c

   1 /*      $NetBSD: floatunsidf_ieee754.c,v 1.1 2013/08/23 16:01:35 matt Exp $     */
   2
   3 /*-
   4  * Copyright (c) 2013 The NetBSD Foundation, Inc.
   5  * All rights reserved.
   6  *
   7  * This code is derived from software contributed to The NetBSD Foundation
   8  * by Matt Thomas of 3am Software Foundry.
   9  *
  10  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions
  12  * are met:
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
  20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
  21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
  23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  29  * POSSIBILITY OF SUCH DAMAGE.
  30  */
  31
  32 #include <sys/cdefs.h>
  33 #if defined(LIBC_SCCS) && !defined(lint)
  34 __RCSID("$NetBSD: floatunsidf_ieee754.c,v 1.1 2013/08/23 16:01:35 matt Exp $");
  35 #endif /* LIBC_SCCS and not lint */
  36
  37 #if defined(SOFTFLOAT) || defined(__ARM_EABI__)
  38 #include "softfloat/softfloat-for-gcc.h"
  39 #endif
  40
  41 #include <machine/ieee.h>
  42
  43 double __floatunsidf(uint32_t);
  44
  45 /*
  46  * Convert (unsigned) int to double.
  47  */
  48 double
  49 __floatunsidf(uint32_t x)
  50 {
  51         union ieee_double_u u;
  52
  53         if (x == 0)
  54                 return 0.0;
  55         if (x == 1)
  56                 return 1.0;
  57
  58         u_int l = __builtin_clz(x);
  59         x <<= (l + 1);  /* clear implicit bit */
  60
  61         u.dblu_sign = 0;
  62         u.dblu_exp = DBL_EXP_BIAS + 31 - l;
  63         u.dblu_frach = x >> (32 - DBL_FRACHBITS);
  64         u.dblu_fracl = x << (32 - DBL_FRACHBITS);
  65
  66         return u.dblu_d;
  67 }