lib/libc/quad/floatdidf_ieee754.c

   1 /*      $NetBSD: floatdidf_ieee754.c,v 1.1 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: floatdidf_ieee754.c,v 1.1 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 <limits.h>
  42 #include <machine/ieee.h>
  43 #include "quad.h"
  44
  45 double __floatdidf(quad_t);
  46
  47 /*
  48  * Convert signed quad to double.
  49  */
  50 double
  51 __floatdidf(quad_t x)
  52 {
  53         union ieee_double_u ux = { .dblu_d = 0.0 };
  54
  55         if (x == 0)
  56                 return 0.0;
  57         if (x == 1)
  58                 return 1.0;
  59
  60         if (x < 0) {
  61                 if (x == QUAD_MIN)
  62                         return -0x1.0p63;
  63                 ux.dblu_sign = 1;
  64                 x = -x;
  65         }
  66         u_int l = __builtin_clzll(x);
  67         x <<= (l + 1);  /* clear implicit bit */
  68         x >>= 64 - (DBL_FRACHBITS + DBL_FRACLBITS);
  69         union uu u = { .uq = x };
  70         ux.dblu_frach = u.ul[H];
  71         ux.dblu_fracl = u.ul[L];
  72         ux.dblu_exp = DBL_EXP_BIAS + 63 - l;
  73
  74         return ux.dblu_d;
  75 }