lib/libc/quad/fixdfdi_ieee754.c

   1 /*      $NetBSD: fixdfdi_ieee754.c,v 1.1 2013/08/24 00:51:48 matt Exp $ */
   2
   3 /*-
   4  * Copyright (c) 1992, 1993
   5  *      The Regents of the University of California.  All rights reserved.
   6  *
   7  * This software was developed by the Computer Systems Engineering group
   8  * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
   9  * contributed to Berkeley.
  10  *
  11  * Redistribution and use in source and binary forms, with or without
  12  * modification, are permitted provided that the following conditions
  13  * are met:
  14  * 1. Redistributions of source code must retain the above copyright
  15  *    notice, this list of conditions and the following disclaimer.
  16  * 2. Redistributions in binary form must reproduce the above copyright
  17  *    notice, this list of conditions and the following disclaimer in the
  18  *    documentation and/or other materials provided with the distribution.
  19  * 3. Neither the name of the University nor the names of its contributors
  20  *    may be used to endorse or promote products derived from this software
  21  *    without specific prior written permission.
  22  *
  23  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  33  * SUCH DAMAGE.
  34  */
  35
  36 #include <sys/cdefs.h>
  37 #if defined(LIBC_SCCS) && !defined(lint)
  38 __RCSID("$NetBSD: fixdfdi_ieee754.c,v 1.1 2013/08/24 00:51:48 matt Exp $");
  39 #endif /* LIBC_SCCS and not lint */
  40
  41 #if defined(SOFTFLOAT) || defined(__ARM_EABI__)
  42 #include "softfloat/softfloat-for-gcc.h"
  43 #endif
  44
  45 #include "quad.h"
  46 #include <limits.h>
  47 #include <stdbool.h>
  48 #include <machine/ieee.h>
  49
  50 /*
  51  * Convert double to signed quad.
  52  * Not sure what to do with negative numbers---for now, anything out
  53  * of range becomes UQUAD_MAX.
  54  */
  55 quad_t
  56 __fixdfdi(double x)
  57 {
  58         const union ieee_double_u ux = { .dblu_d = x };
  59         signed int exp = ux.dblu_exp - DBL_EXP_BIAS;
  60         const bool neg = ux.dblu_sign;
  61         quad_t r;
  62
  63         if (exp >= 62)
  64                 return neg ? QUAD_MIN : QUAD_MAX;
  65
  66         r = 1 << DBL_FRACHBITS;         /* implicit bit */
  67         r |= ux.dblu_frach;
  68         exp -= DBL_FRACHBITS;
  69         if (exp < 0) {
  70                 r >>= -exp;
  71         } else if (exp > 0) {
  72                 r <<= DBL_FRACLBITS;
  73                 r |= ux.dblu_fracl;
  74                 exp -= DBL_FRACLBITS;
  75                 if (exp < 0) {
  76                         r >>= -exp;
  77                 } else if (exp > 0) {
  78                         r <<= exp;
  79                 }
  80         }
  81         return neg ? -r : r;
  82 }