Annotation of sys/lib/libkern/ashrdi3.c, Revision 1.1
1.1 ! nbrk 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. Neither the name of the University nor the names of its contributors
! 18: * may be used to endorse or promote products derived from this software
! 19: * without specific prior written permission.
! 20: *
! 21: * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
! 22: * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
! 23: * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
! 24: * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
! 25: * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
! 26: * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
! 27: * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
! 28: * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
! 29: * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
! 30: * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
! 31: * SUCH DAMAGE.
! 32: */
! 33:
! 34: #if defined(LIBC_SCCS) && !defined(lint)
! 35: static char rcsid[] = "$OpenBSD: ashrdi3.c,v 1.5 2004/11/28 07:23:41 mickey Exp $";
! 36: #endif /* LIBC_SCCS and not lint */
! 37:
! 38: #include "quad.h"
! 39:
! 40: /*
! 41: * Shift a (signed) quad value right (arithmetic shift right).
! 42: */
! 43: quad_t
! 44: __ashrdi3(quad_t a, qshift_t shift)
! 45: {
! 46: union uu aa;
! 47:
! 48: if (shift == 0)
! 49: return(a);
! 50: aa.q = a;
! 51: if (shift >= INT_BITS) {
! 52: int s;
! 53:
! 54: /*
! 55: * Smear bits rightward using the machine's right-shift
! 56: * method, whether that is sign extension or zero fill,
! 57: * to get the `sign word' s. Note that shifting by
! 58: * INT_BITS is undefined, so we shift (INT_BITS-1),
! 59: * then 1 more, to get our answer.
! 60: */
! 61: /* LINTED inherits machine dependency */
! 62: s = (aa.sl[H] >> (INT_BITS - 1)) >> 1;
! 63: /* LINTED inherits machine dependency*/
! 64: aa.ul[L] = aa.sl[H] >> (shift - INT_BITS);
! 65: aa.ul[H] = s;
! 66: } else {
! 67: aa.ul[L] = (aa.ul[L] >> shift) |
! 68: (aa.ul[H] << (INT_BITS - shift));
! 69: /* LINTED inherits machine dependency */
! 70: aa.sl[H] >>= shift;
! 71: }
! 72: return (aa.q);
! 73: }
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