/*
 * 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 2005 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#ident  "%Z%%M% %I%     %E% SMI"

#include <sys/asm_linkage.h>

/*
 * ip_ocsum(address, halfword_count, sum)
 * Do a 16 bit one's complement sum of a given number of (16-bit)
 * halfwords. The halfword pointer must not be odd.
 *      %o0 address; %o1 count; %o2 sum accumulator; %o4 temp
 *      %g2 and %g3 used in main loop
 *
 * (from @(#)ocsum.s 1.3 89/02/24 SMI)
 *
 */

        ENTRY(ip_ocsum)
        cmp     %o1, 31         ! less than 62 bytes?
        bl,a    .dohw           !   just do halfwords
        tst     %o1             ! delay slot, test count

        btst    31, %o0         ! (delay slot)
        bz      2f              ! if 32 byte aligned, skip
        nop

        !
        ! Do first halfwords until 32-byte aligned
        !
1:
        lduh    [%o0], %g2      ! read data
        add     %o0, 2, %o0     ! increment address
        add     %o2, %g2, %o2   ! add to accumulator, don't need carry yet
        btst    31, %o0         ! 32 byte aligned?
        bnz     1b
        sub     %o1, 1, %o1     ! decrement count
        !
        ! loop to add in 32 byte chunks
        ! The loads and adds are staggered to help avoid load/use
        ! interlocks on highly pipelined implementations, and double
        ! loads are used for 64-bit wide memory systems.
        !
2:
        sub     %o1, 16, %o1    ! decrement count to aid testing
4:
        ldd     [%o0], %g2      ! read data
        ldd     [%o0+8], %o4    ! read more data
        addcc   %o2, %g2, %o2   ! add to accumulator
        addxcc  %o2, %g3, %o2   ! add to accumulator with carry
        ldd     [%o0+16], %g2   ! read more data
        addxcc  %o2, %o4, %o2   ! add to accumulator with carry
        addxcc  %o2, %o5, %o2   ! add to accumulator with carry
        ldd     [%o0+24], %o4   ! read more data
        addxcc  %o2, %g2, %o2   ! add to accumulator with carry
        addxcc  %o2, %g3, %o2   ! add to accumulator with carry
        addxcc  %o2, %o4, %o2   ! add to accumulator
        addxcc  %o2, %o5, %o2   ! add to accumulator with carry
        addxcc  %o2, 0, %o2     ! if final carry, add it in
        subcc   %o1, 16, %o1    ! decrement count (in halfwords)
        bge     4b
        add     %o0, 32, %o0    ! delay slot, increment address

        add     %o1, 16, %o1    ! add back in
        !
        ! Do any remaining halfwords
        !
        b       .dohw
        tst     %o1             ! delay slot, for more to do

3:
        add     %o0, 2, %o0     ! increment address
        addcc   %o2, %g2, %o2   ! add to accumulator
        addxcc  %o2, 0, %o2     ! if carry, add it in
        subcc   %o1, 1, %o1     ! decrement count
.dohw:
        bg,a    3b              ! more to do?
        lduh    [%o0], %g2      ! read data

        !
        ! at this point the 32-bit accumulator
        ! has the result that needs to be returned in 16-bits
        !
        sll     %o2, 16, %o4    ! put low halfword in high halfword %o4
        addcc   %o4, %o2, %o2   ! add the 2 halfwords in high %o2, set carry
        srl     %o2, 16, %o2    ! shift to low halfword
        retl                    ! return
        addxcc  %o2, 0, %o0     ! add in carry if any. result in %o0
        SET_SIZE(ip_ocsum)