Subversion Repositories or1k

/*
 * arch/alpha/lib/ev67-strcat.S
 * 21264 version contributed by Rick Gorton <rick.gorton@alpha-processor.com>
 *
 * Append a null-terminated string from SRC to DST.
 *
 * Much of the information about 21264 scheduling/coding comes from:
 *      Compiler Writer's Guide for the Alpha 21264
 *      abbreviated as 'CWG' in other comments here
 *      ftp.digital.com/pub/Digital/info/semiconductor/literature/dsc-library.html
 * Scheduling notation:
 *      E       - either cluster
 *      U       - upper subcluster; U0 - subcluster U0; U1 - subcluster U1
 *      L       - lower subcluster; L0 - subcluster L0; L1 - subcluster L1
 * Try not to change the actual algorithm if possible for consistency.
 * Commentary: It seems bogus to walk the input string twice - once
 * to determine the length, and then again while doing the copy.
 * A significant (future) enhancement would be to only read the input
 * string once.
 */


        .text

        .align 4
        .globl strcat
        .ent strcat
strcat:
        .frame $30, 0, $26
        .prologue 0

        mov     $16, $0         # E : set up return value
        /* Find the end of the string.  */
        ldq_u   $1, 0($16)      # L : load first quadword (a0 may be misaligned)
        lda     $2, -1          # E :
        insqh   $2, $16, $2     # U :

        andnot  $16, 7, $16     # E :
        or      $2, $1, $1      # E :
        cmpbge  $31, $1, $2     # E : bits set iff byte == 0
        bne     $2, $found      # U :

$loop:  ldq     $1, 8($16)      # L :
        addq    $16, 8, $16     # E :
        cmpbge  $31, $1, $2     # E :
        beq     $2, $loop       # U :

$found: cttz    $2, $3          # U0 :
        addq    $16, $3, $16    # E :
        /* Now do the append.  */
        mov     $26, $23        # E :
        br      __stxcpy        # L0 :

        .end strcat