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/*
* 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.
*/
.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
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