[unix-history] / usr / src / lib / libc / quad / ashrdi3.c

/*-
* Copyright (c) 1992 The Regents of the University of California.
* All rights reserved.
*
* This software was developed by the Computer Systems Engineering group
* at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
* contributed to Berkeley.
*
* %sccs.include.redist.c%
*/

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)ashrdi3.c   5.6 (Berkeley) %G%";
#endif /* LIBC_SCCS and not lint */

#include "quad.h"

/*
* Shift a (signed) quad value right (arithmetic shift right).
*/
quad
__ashrdi3(quad a, qshift_t shift)
{
       union uu aa;

       aa.q = a;
       if (shift >= LONG_BITS) {
               long s;

               /*
                * Smear bits rightward using the machine's right-shift
                * method, whether that is sign extension or zero fill,
                * to get the `sign word' s.  Note that shifting by
                * LONG_BITS is undefined, so we shift (LONG_BITS-1),
                * then 1 more, to get our answer.
                */
               s = (aa.sl[H] >> (LONG_BITS - 1)) >> 1;
               aa.ul[L] = shift >= QUAD_BITS ? s :
                   aa.sl[H] >> (shift - LONG_BITS);
               aa.ul[H] = s;
       } else if (shift > 0) {
               aa.ul[L] = (aa.ul[L] >> shift) |
                   (aa.ul[H] << (LONG_BITS - shift));
               aa.sl[H] >>= shift;
       }
       return (aa.q);
}