lib/libc/quad/floatundisf_ieee754.c

   1 /*      $NetBSD: floatundisf_ieee754.c,v 1.2 2013/08/24 00:51:48 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: floatundisf_ieee754.c,v 1.2 2013/08/24 00:51:48 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 #include "quad.h"
  43
  44 float __floatundisf(u_quad_t);
  45
  46 /*
  47  * Convert unsigned quad to float.
  48  */
  49 float
  50 __floatundisf(u_quad_t x)
  51 {
  52         union ieee_single_u ux = { .sngu_f = 0.0 };
  53
  54         if (x == 0)
  55                 return 0.0;
  56         if (x == 1)
  57                 return 1.0;
  58
  59 #if defined(_LP64) || defined(__mips_n32)
  60         u_int l = __builtin_clzll(x);
  61         x <<= (l + 1);  /* clear implicit bit */
  62
  63         ux.sngu_frac = x >> (64 - SNG_FRACBITS);
  64 #else
  65         union uu u = { .uq = x };
  66         uint32_t frac;
  67         u_int l;
  68         if (u.ul[H] == 0) {
  69                 l = __builtin_clz(u.ul[L]);
  70                 frac = u.ul[L] << (l + 1);      /* clear implicit bit */
  71                 l += 32;
  72         } else {
  73                 l = __builtin_clz(u.ul[H]);
  74                 frac = u.ul[H] << (l + 1);      /* clear implicit bit */
  75                 frac |= u.ul[L] >> (32 - (l + 1));
  76         }
  77
  78         ux.sngu_frac = frac >> (32 - SNG_FRACBITS);
  79 #endif
  80         ux.sngu_exp = SNG_EXP_BIAS + 63 - l;
  81
  82         return ux.sngu_f;
  83 }