arch/metag/lib/ip_fast_csum.S

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2
   3         .text
   4 /*
   5  * This is a version of ip_compute_csum() optimized for IP headers,
   6  * which always checksum on 4 octet boundaries.
   7  *
   8  * extern __sum16 ip_fast_csum(const void *iph, unsigned int ihl);
   9  *
  10  */
  11         .global _ip_fast_csum
  12         .type   _ip_fast_csum,function
  13 _ip_fast_csum:
  14         !! TXRPT needs loops - 1
  15         SUBS    TXRPT,D0Ar2,#1
  16         MOV     D0Re0,#0
  17         BLO     $Lfast_csum_exit
  18 $Lfast_csum_loop:
  19         GETD    D1Ar3,[D1Ar1++]
  20         ADDS    D0Re0,D0Re0,D1Ar3
  21         ADDCS   D0Re0,D0Re0,#1
  22         BR      $Lfast_csum_loop
  23         LSR     D0Ar4,D0Re0,#16
  24         AND     D0Re0,D0Re0,#0xffff
  25         AND     D0Ar4,D0Ar4,#0xffff
  26         ADD     D0Re0,D0Re0,D0Ar4
  27         LSR     D0Ar4,D0Re0,#16
  28         ADD     D0Re0,D0Re0,D0Ar4
  29         XOR     D0Re0,D0Re0,#-1
  30         AND     D0Re0,D0Re0,#0xffff
  31 $Lfast_csum_exit:
  32         MOV     PC,D1RtP
  33         .size _ip_fast_csum,.-_ip_fast_csum