LXR linux/arch/alpha/lib/ev67-strcat.S

   1/* SPDX-License-Identifier: GPL-2.0 */
   2/*
   3 * arch/alpha/lib/ev67-strcat.S
   4 * 21264 version contributed by Rick Gorton <rick.gorton@alpha-processor.com>
   5 *
   6 * Append a null-terminated string from SRC to DST.
   7 *
   8 * Much of the information about 21264 scheduling/coding comes from:
   9 *      Compiler Writer's Guide for the Alpha 21264
  10 *      abbreviated as 'CWG' in other comments here
  11 *      ftp.digital.com/pub/Digital/info/semiconductor/literature/dsc-library.html
  12 * Scheduling notation:
  13 *      E       - either cluster
  14 *      U       - upper subcluster; U0 - subcluster U0; U1 - subcluster U1
  15 *      L       - lower subcluster; L0 - subcluster L0; L1 - subcluster L1
  16 * Try not to change the actual algorithm if possible for consistency.
  17 * Commentary: It seems bogus to walk the input string twice - once
  18 * to determine the length, and then again while doing the copy.
  19 * A significant (future) enhancement would be to only read the input
  20 * string once.
  21 */
  22
  23#include <asm/export.h>
  24        .text
  25
  26        .align 4
  27        .globl strcat
  28        .ent strcat
  29strcat:
  30        .frame $30, 0, $26
  31        .prologue 0
  32
  33        mov     $16, $0         # E : set up return value
  34        /* Find the end of the string.  */
  35        ldq_u   $1, 0($16)      # L : load first quadword (a0 may be misaligned)
  36        lda     $2, -1          # E :
  37        insqh   $2, $16, $2     # U :
  38
  39        andnot  $16, 7, $16     # E :
  40        or      $2, $1, $1      # E :
  41        cmpbge  $31, $1, $2     # E : bits set iff byte == 0
  42        bne     $2, $found      # U :
  43
  44$loop:  ldq     $1, 8($16)      # L :
  45        addq    $16, 8, $16     # E :
  46        cmpbge  $31, $1, $2     # E :
  47        beq     $2, $loop       # U :
  48
  49$found: cttz    $2, $3          # U0 :
  50        addq    $16, $3, $16    # E :
  51        /* Now do the append.  */
  52        mov     $26, $23        # E :
  53        br      __stxcpy        # L0 :
  54
  55        .end strcat
  56        EXPORT_SYMBOL(strcat)
  57