You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
49 lines
1.2 KiB
49 lines
1.2 KiB
/*
|
|
* arch/alpha/lib/ev67-strlen.S
|
|
* 21264 version by Rick Gorton <rick.gorton@alpha-processor.com>
|
|
*
|
|
* Finds length of a 0-terminated string. Optimized for the
|
|
* Alpha architecture:
|
|
*
|
|
* - memory accessed as aligned quadwords only
|
|
* - uses bcmpge to compare 8 bytes in parallel
|
|
*
|
|
* 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
|
|
*/
|
|
|
|
.set noreorder
|
|
.set noat
|
|
|
|
.globl strlen
|
|
.ent strlen
|
|
.align 4
|
|
strlen:
|
|
ldq_u $1, 0($16) # L : load first quadword ($16 may be misaligned)
|
|
lda $2, -1($31) # E :
|
|
insqh $2, $16, $2 # U :
|
|
andnot $16, 7, $0 # E :
|
|
|
|
or $2, $1, $1 # E :
|
|
cmpbge $31, $1, $2 # E : $2 <- bitmask: bit i == 1 <==> i-th byte == 0
|
|
nop # E :
|
|
bne $2, $found # U :
|
|
|
|
$loop: ldq $1, 8($0) # L :
|
|
addq $0, 8, $0 # E : addr += 8
|
|
cmpbge $31, $1, $2 # E :
|
|
beq $2, $loop # U :
|
|
|
|
$found:
|
|
cttz $2, $3 # U0 :
|
|
addq $0, $3, $0 # E :
|
|
subq $0, $16, $0 # E :
|
|
ret $31, ($26) # L0 :
|
|
|
|
.end strlen
|
|
|