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Annotation of src/lib/libc/quad/floatundidf_ieee754.c, Revision 1.2

1.2     ! mlelstv     1: /*     $NetBSD: floatundidf_ieee754.c,v 1.1 2013/08/24 00:51:48 matt Exp $     */
1.1       matt        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)
1.2     ! mlelstv    34: __RCSID("$NetBSD: floatundidf_ieee754.c,v 1.1 2013/08/24 00:51:48 matt Exp $");
1.1       matt       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: /*
                     46:  * Convert unsigned quad to double.
                     47:  */
                     48: double
                     49: __floatundidf(u_quad_t x)
                     50: {
                     51:        union ieee_double_u ux = { .dblu_d = 0.0 };
                     52:
                     53:        if (x == 0)
                     54:                return 0.0;
                     55:
                     56:        u_int l = __builtin_clzll(x);
                     57:        x <<= (l + 1);  /* clear implicit bit */
                     58:        x >>= 64 - (DBL_FRACHBITS + DBL_FRACLBITS);
                     59:        union uu u = { .uq = x };
                     60:        ux.dblu_frach = u.ul[H];
                     61:        ux.dblu_fracl = u.ul[L];
                     62:        ux.dblu_exp = DBL_EXP_BIAS + 63 - l;
                     63:
                     64:        return ux.dblu_d;
                     65: }

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