ashrdi3.c revision 116189
11541Srgrimes/*- 21541Srgrimes * Copyright (c) 1992, 1993 31541Srgrimes * The Regents of the University of California. All rights reserved. 41541Srgrimes * 51541Srgrimes * This software was developed by the Computer Systems Engineering group 61541Srgrimes * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and 71541Srgrimes * contributed to Berkeley. 81541Srgrimes * 91541Srgrimes * Redistribution and use in source and binary forms, with or without 101541Srgrimes * modification, are permitted provided that the following conditions 111541Srgrimes * are met: 121541Srgrimes * 1. Redistributions of source code must retain the above copyright 131541Srgrimes * notice, this list of conditions and the following disclaimer. 141541Srgrimes * 2. Redistributions in binary form must reproduce the above copyright 151541Srgrimes * notice, this list of conditions and the following disclaimer in the 161541Srgrimes * documentation and/or other materials provided with the distribution. 171541Srgrimes * 3. All advertising materials mentioning features or use of this software 181541Srgrimes * must display the following acknowledgement: 191541Srgrimes * This product includes software developed by the University of 201541Srgrimes * California, Berkeley and its contributors. 211541Srgrimes * 4. Neither the name of the University nor the names of its contributors 221541Srgrimes * may be used to endorse or promote products derived from this software 231541Srgrimes * without specific prior written permission. 241541Srgrimes * 251541Srgrimes * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 261541Srgrimes * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 271541Srgrimes * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 281541Srgrimes * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 291541Srgrimes * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 301541Srgrimes * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 311541Srgrimes * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 321541Srgrimes * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 331541Srgrimes * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 341541Srgrimes * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 351541Srgrimes * SUCH DAMAGE. 361541Srgrimes */ 371541Srgrimes 38116189Sobrien#include <sys/cdefs.h> 39116189Sobrien__FBSDID("$FreeBSD: head/sys/libkern/ashrdi3.c 116189 2003-06-11 05:37:42Z obrien $"); 40116189Sobrien 4170949Sbenno#include <libkern/quad.h> 421541Srgrimes 431541Srgrimes/* 441541Srgrimes * Shift a (signed) quad value right (arithmetic shift right). 451541Srgrimes */ 461541Srgrimesquad_t 471541Srgrimes__ashrdi3(a, shift) 481541Srgrimes quad_t a; 491541Srgrimes qshift_t shift; 501541Srgrimes{ 511541Srgrimes union uu aa; 521541Srgrimes 531541Srgrimes aa.q = a; 541541Srgrimes if (shift >= LONG_BITS) { 551541Srgrimes long s; 561541Srgrimes 571541Srgrimes /* 581541Srgrimes * Smear bits rightward using the machine's right-shift 591541Srgrimes * method, whether that is sign extension or zero fill, 601541Srgrimes * to get the `sign word' s. Note that shifting by 611541Srgrimes * LONG_BITS is undefined, so we shift (LONG_BITS-1), 621541Srgrimes * then 1 more, to get our answer. 631541Srgrimes */ 641541Srgrimes s = (aa.sl[H] >> (LONG_BITS - 1)) >> 1; 651541Srgrimes aa.ul[L] = shift >= QUAD_BITS ? s : 661541Srgrimes aa.sl[H] >> (shift - LONG_BITS); 671541Srgrimes aa.ul[H] = s; 681541Srgrimes } else if (shift > 0) { 691541Srgrimes aa.ul[L] = (aa.ul[L] >> shift) | 701541Srgrimes (aa.ul[H] << (LONG_BITS - shift)); 711541Srgrimes aa.sl[H] >>= shift; 721541Srgrimes } 731541Srgrimes return (aa.q); 741541Srgrimes} 75