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| /* SPDX-License-Identifier: GPL-2.0 */
| /*
| * arch/alpha/lib/ev67-strncat.S
| * 21264 version contributed by Rick Gorton <rick.gorton@api-networks.com>
| *
| * Append no more than COUNT characters from the null-terminated string SRC
| * to the null-terminated string DST. Always null-terminate the new DST.
| *
| * This differs slightly from the semantics in libc in that we never write
| * past count, whereas libc may write to count+1. This follows the generic
| * implementation in lib/string.c and is, IMHO, more sensible.
| *
| * 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.
| */
|
| #include <asm/export.h>
| .text
|
| .align 4
| .globl strncat
| .ent strncat
| strncat:
| .frame $30, 0, $26
| .prologue 0
|
| mov $16, $0 # set up return value
| beq $18, $zerocount # U :
| /* Find the end of the string. */
| ldq_u $1, 0($16) # L : load first quadword ($16 may be misaligned)
| lda $2, -1($31) # E :
|
| insqh $2, $0, $2 # U :
| andnot $16, 7, $16 # E :
| nop # E :
| or $2, $1, $1 # E :
|
| nop # E :
| nop # 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 :
| nop # E :
| bsr $23, __stxncpy # L0 :/* Now do the append. */
|
| /* Worry about the null termination. */
|
| zapnot $1, $27, $2 # U : was last byte a null?
| cmplt $27, $24, $5 # E : did we fill the buffer completely?
| bne $2, 0f # U :
| ret # L0 :
|
| 0: or $5, $18, $2 # E :
| nop
| bne $2, 2f # U :
| and $24, 0x80, $3 # E : no zero next byte
|
| nop # E :
| bne $3, 1f # U :
| /* Here there are bytes left in the current word. Clear one. */
| addq $24, $24, $24 # E : end-of-count bit <<= 1
| nop # E :
|
| 2: zap $1, $24, $1 # U :
| nop # E :
| stq_u $1, 0($16) # L :
| ret # L0 :
|
| 1: /* Here we must clear the first byte of the next DST word */
| stb $31, 8($16) # L :
| nop # E :
| nop # E :
| ret # L0 :
|
| $zerocount:
| nop # E :
| nop # E :
| nop # E :
| ret # L0 :
|
| .end strncat
| EXPORT_SYMBOL(strncat)
|
|
