111 lines
3.3 KiB
ArmAsm
111 lines
3.3 KiB
ArmAsm
|
/*
|
||
|
|
* arch/alpha/lib/ev67-strrchr.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
|
||
|
|
*/
|
||
|
|
|
||
|
|
#include <asm/export.h>
|
||
|
|
#include <asm/regdef.h>
|
||
|
|
|
||
|
|
.set noreorder
|
||
|
|
.set noat
|
||
|
|
|
||
|
|
.align 4
|
||
|
|
.ent strrchr
|
||
|
|
.globl strrchr
|
||
|
|
strrchr:
|
||
|
|
.frame sp, 0, ra
|
||
|
|
.prologue 0
|
||
|
|
|
||
|
|
and a1, 0xff, t2 # E : 00000000000000ch
|
||
|
|
insbl a1, 1, t4 # U : 000000000000ch00
|
||
|
|
insbl a1, 2, t5 # U : 0000000000ch0000
|
||
|
|
ldq_u t0, 0(a0) # L : load first quadword Latency=3
|
||
|
|
|
||
|
|
mov zero, t6 # E : t6 is last match aligned addr
|
||
|
|
or t2, t4, a1 # E : 000000000000chch
|
||
|
|
sll t5, 8, t3 # U : 00000000ch000000
|
||
|
|
mov zero, t8 # E : t8 is last match byte compare mask
|
||
|
|
|
||
|
|
andnot a0, 7, v0 # E : align source addr
|
||
|
|
or t5, t3, t3 # E : 00000000chch0000
|
||
|
|
sll a1, 32, t2 # U : 0000chch00000000
|
||
|
|
sll a1, 48, t4 # U : chch000000000000
|
||
|
|
|
||
|
|
or t4, a1, a1 # E : chch00000000chch
|
||
|
|
or t2, t3, t2 # E : 0000chchchch0000
|
||
|
|
or a1, t2, a1 # E : chchchchchchchch
|
||
|
|
lda t5, -1 # E : build garbage mask
|
||
|
|
|
||
|
|
cmpbge zero, t0, t1 # E : bits set iff byte == zero
|
||
|
|
mskqh t5, a0, t4 # E : Complete garbage mask
|
||
|
|
xor t0, a1, t2 # E : make bytes == c zero
|
||
|
|
cmpbge zero, t4, t4 # E : bits set iff byte is garbage
|
||
|
|
|
||
|
|
cmpbge zero, t2, t3 # E : bits set iff byte == c
|
||
|
|
andnot t1, t4, t1 # E : clear garbage from null test
|
||
|
|
andnot t3, t4, t3 # E : clear garbage from char test
|
||
|
|
bne t1, $eos # U : did we already hit the terminator?
|
||
|
|
|
||
|
|
/* Character search main loop */
|
||
|
|
$loop:
|
||
|
|
ldq t0, 8(v0) # L : load next quadword
|
||
|
|
cmovne t3, v0, t6 # E : save previous comparisons match
|
||
|
|
nop # : Latency=2, extra map slot (keep nop with cmov)
|
||
|
|
nop
|
||
|
|
|
||
|
|
cmovne t3, t3, t8 # E : Latency=2, extra map slot
|
||
|
|
nop # : keep with cmovne
|
||
|
|
addq v0, 8, v0 # E :
|
||
|
|
xor t0, a1, t2 # E :
|
||
|
|
|
||
|
|
cmpbge zero, t0, t1 # E : bits set iff byte == zero
|
||
|
|
cmpbge zero, t2, t3 # E : bits set iff byte == c
|
||
|
|
beq t1, $loop # U : if we havnt seen a null, loop
|
||
|
|
nop
|
||
|
|
|
||
|
|
/* Mask out character matches after terminator */
|
||
|
|
$eos:
|
||
|
|
negq t1, t4 # E : isolate first null byte match
|
||
|
|
and t1, t4, t4 # E :
|
||
|
|
subq t4, 1, t5 # E : build a mask of the bytes up to...
|
||
|
|
or t4, t5, t4 # E : ... and including the null
|
||
|
|
|
||
|
|
and t3, t4, t3 # E : mask out char matches after null
|
||
|
|
cmovne t3, t3, t8 # E : save it, if match found Latency=2, extra map slot
|
||
|
|
nop # : Keep with cmovne
|
||
|
|
nop
|
||
|
|
|
||
|
|
cmovne t3, v0, t6 # E :
|
||
|
|
nop # : Keep with cmovne
|
||
|
|
/* Locate the address of the last matched character */
|
||
|
|
ctlz t8, t2 # U0 : Latency=3 (0x40 for t8=0)
|
||
|
|
nop
|
||
|
|
|
||
|
|
cmoveq t8, 0x3f, t2 # E : Compensate for case when no match is seen
|
||
|
|
nop # E : hide the cmov latency (2) behind ctlz latency
|
||
|
|
lda t5, 0x3f($31) # E :
|
||
|
|
subq t5, t2, t5 # E : Normalize leading zero count
|
||
|
|
|
||
|
|
addq t6, t5, v0 # E : and add to quadword address
|
||
|
|
ret # L0 : Latency=3
|
||
|
|
nop
|
||
|
|
nop
|
||
|
|
|
||
|
|
.end strrchr
|
||
|
|
EXPORT_SYMBOL(strrchr)
|