Subversion Repositories or1k

/*
 * Optmized version of the ip_fast_csum() function
 * Used for calculating IP header checksum
 *
 * Return: 16bit checksum, complemented
 *
 * Inputs:
 *      in0: address of buffer to checksum (char *)
 *      in1: length of the buffer (int)
 *
 * Copyright (C) 2002 Intel Corp.
 * Copyright (C) 2002 Ken Chen <kenneth.w.chen@intel.com>
 */

#include <asm/asmmacro.h>

/*
 * Since we know that most likely this function is called with buf aligned
 * on 4-byte boundary and 20 bytes in length, we can execution rather quickly
 * versus calling generic version of do_csum, which has lots of overhead in
 * handling various alignments and sizes.  However, due to lack of constrains
 * put on the function input argument, cases with alignment not on 4-byte or
 * size not equal to 20 bytes will be handled by the generic do_csum function.
 */

#define in0     r32
#define in1     r33
#define ret0    r8

GLOBAL_ENTRY(ip_fast_csum)
        .prologue
        .body
        cmp.ne  p6,p7=5,in1     // size other than 20 byte?
        and     r14=3,in0       // is it aligned on 4-byte?
        add     r15=4,in0       // second source pointer
        ;;
        cmp.ne.or.andcm p6,p7=r14,r0
        ;;
(p7)    ld4     r20=[in0],8
(p7)    ld4     r21=[r15],8
(p6)    br.spnt .generic
        ;;
        ld4     r22=[in0],8
        ld4     r23=[r15],8
        ;;
        ld4     r24=[in0]
        add     r20=r20,r21
        add     r22=r22,r23
        ;;
        add     r20=r20,r22
        ;;
        add     r20=r20,r24
        ;;
        shr.u   ret0=r20,16     // now need to add the carry
        zxt2    r20=r20
        ;;
        add     r20=ret0,r20
        ;;
        shr.u   ret0=r20,16     // add carry again
        zxt2    r20=r20
        ;;
        add     r20=ret0,r20
        ;;
        shr.u   ret0=r20,16
        zxt2    r20=r20
        ;;
        add     r20=ret0,r20
        ;;
        andcm   ret0=-1,r20
        .restore sp             // reset frame state
        br.ret.sptk.many b0
        ;;

.generic:
        .prologue
        .save ar.pfs, r35
        alloc   r35=ar.pfs,2,2,2,0
        .save rp, r34
        mov     r34=b0
        .body
        dep.z   out1=in1,2,30
        mov     out0=in0
        ;;
        br.call.sptk.many b0=do_csum
        ;;
        andcm   ret0=-1,ret0
        mov     ar.pfs=r35
        mov     b0=r34
        br.ret.sptk.many b0
END(ip_fast_csum)