_mul64.s revision 7c478bd95313f5f23a4c958a745db2134aa03244
/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License, Version 1.0 only
* (the "License"). You may not use this file except in compliance
* with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or http://www.opensolaris.org/os/licensing.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright 2004 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
.ident "%Z%%M% %I% %E% SMI"
.file "%M%"
/
/ function __mul64(A,B:Longint):Longint;
/ {Overflow is not checked}
/
/ We essentially do multiply by longhand, using base 2**32 digits.
/ a b parameter A
/ x c d parameter B
/ ---------
/ ad bd
/ ac bc
/ -----------------
/ ac ad+bc bd
/
/ We can ignore ac and top 32 bits of ad+bc: if <> 0, overflow happened.
/
#include "SYS.h"
ENTRY(__mul64)
push %ebp
mov %esp,%ebp
pushl %esi
mov 12(%ebp),%eax / A.hi (a)
mull 16(%ebp) / Multiply A.hi by B.lo (produces ad)
xchg %ecx,%eax / ecx = bottom half of ad.
movl 8(%ebp),%eax / A.Lo (b)
movl %eax,%esi / Save A.lo for later
mull 16(%ebp) / Multiply A.Lo by B.LO (dx:ax = bd.)
addl %edx,%ecx / cx is ad
xchg %eax,%esi / esi is bd, eax = A.lo (d)
mull 20(%ebp) / Multiply A.lo * B.hi (producing bc)
addl %ecx,%eax / Produce ad+bc
movl %esi,%edx
xchg %eax,%edx
popl %esi
movl %ebp,%esp
popl %ebp
ret $16
SET_SIZE(__mul64)