ashrdi3.c revision 70949
1/*- 2 * Copyright (c) 1992, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * This software was developed by the Computer Systems Engineering group 6 * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and 7 * contributed to Berkeley. 8 * 9 * Redistribution and use in source and binary forms, with or without 10 * modification, are permitted provided that the following conditions 11 * are met: 12 * 1. Redistributions of source code must retain the above copyright 13 * notice, this list of conditions and the following disclaimer. 14 * 2. Redistributions in binary form must reproduce the above copyright 15 * notice, this list of conditions and the following disclaimer in the 16 * documentation and/or other materials provided with the distribution. 17 * 3. All advertising materials mentioning features or use of this software 18 * must display the following acknowledgement: 19 * This product includes software developed by the University of 20 * California, Berkeley and its contributors. 21 * 4. Neither the name of the University nor the names of its contributors 22 * may be used to endorse or promote products derived from this software 23 * without specific prior written permission. 24 * 25 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 26 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 27 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 28 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 29 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 30 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 31 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 32 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 33 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 34 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 35 * SUCH DAMAGE. 36 * 37 * $FreeBSD: head/sys/libkern/ashrdi3.c 70949 2001-01-12 07:28:46Z benno $ 38 */ 39 40#include <libkern/quad.h> 41 42/* 43 * Shift a (signed) quad value right (arithmetic shift right). 44 */ 45quad_t 46__ashrdi3(a, shift) 47 quad_t a; 48 qshift_t shift; 49{ 50 union uu aa; 51 52 aa.q = a; 53 if (shift >= LONG_BITS) { 54 long s; 55 56 /* 57 * Smear bits rightward using the machine's right-shift 58 * method, whether that is sign extension or zero fill, 59 * to get the `sign word' s. Note that shifting by 60 * LONG_BITS is undefined, so we shift (LONG_BITS-1), 61 * then 1 more, to get our answer. 62 */ 63 s = (aa.sl[H] >> (LONG_BITS - 1)) >> 1; 64 aa.ul[L] = shift >= QUAD_BITS ? s : 65 aa.sl[H] >> (shift - LONG_BITS); 66 aa.ul[H] = s; 67 } else if (shift > 0) { 68 aa.ul[L] = (aa.ul[L] >> shift) | 69 (aa.ul[H] << (LONG_BITS - shift)); 70 aa.sl[H] >>= shift; 71 } 72 return (aa.q); 73} 74