forked from Qortal/Brooklyn
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.
90 lines
2.8 KiB
90 lines
2.8 KiB
/* SPDX-License-Identifier: GPL-2.0 */ |
|
/* |
|
* arch/alpha/lib/ev67-strchr.S |
|
* 21264 version contributed by Rick Gorton <rick.gorton@alpha-processor.com> |
|
* |
|
* Return the address of a given character within a null-terminated |
|
* string, or null if it is not found. |
|
* |
|
* 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> |
|
#include <asm/regdef.h> |
|
|
|
.set noreorder |
|
.set noat |
|
|
|
.align 4 |
|
.globl strchr |
|
.ent strchr |
|
strchr: |
|
.frame sp, 0, ra |
|
.prologue 0 |
|
|
|
ldq_u t0, 0(a0) # L : load first quadword Latency=3 |
|
and a1, 0xff, t3 # E : 00000000000000ch |
|
insbl a1, 1, t5 # U : 000000000000ch00 |
|
insbl a1, 7, a2 # U : ch00000000000000 |
|
|
|
insbl t3, 6, a3 # U : 00ch000000000000 |
|
or t5, t3, a1 # E : 000000000000chch |
|
andnot a0, 7, v0 # E : align our loop pointer |
|
lda t4, -1 # E : build garbage mask |
|
|
|
mskqh t4, a0, t4 # U : only want relevant part of first quad |
|
or a2, a3, a2 # E : chch000000000000 |
|
inswl a1, 2, t5 # E : 00000000chch0000 |
|
inswl a1, 4, a3 # E : 0000chch00000000 |
|
|
|
or a1, a2, a1 # E : chch00000000chch |
|
or a3, t5, t5 # E : 0000chchchch0000 |
|
cmpbge zero, t0, t2 # E : bits set iff byte == zero |
|
cmpbge zero, t4, t4 # E : bits set iff byte is garbage |
|
|
|
/* This quad is _very_ serialized. Lots of stalling happens */ |
|
or t5, a1, a1 # E : chchchchchchchch |
|
xor t0, a1, t1 # E : make bytes == c zero |
|
cmpbge zero, t1, t3 # E : bits set iff byte == c |
|
or t2, t3, t0 # E : bits set iff char match or zero match |
|
|
|
andnot t0, t4, t0 # E : clear garbage bits |
|
cttz t0, a2 # U0 : speculative (in case we get a match) |
|
nop # E : |
|
bne t0, $found # U : |
|
|
|
/* |
|
* Yuk. This loop is going to stall like crazy waiting for the |
|
* data to be loaded. Not much can be done about it unless it's |
|
* unrolled multiple times - is that safe to do in kernel space? |
|
* Or would exception handling recovery code do the trick here? |
|
*/ |
|
$loop: ldq t0, 8(v0) # L : Latency=3 |
|
addq v0, 8, v0 # E : |
|
xor t0, a1, t1 # E : |
|
cmpbge zero, t0, t2 # E : bits set iff byte == 0 |
|
|
|
cmpbge zero, t1, t3 # E : bits set iff byte == c |
|
or t2, t3, t0 # E : |
|
cttz t3, a2 # U0 : speculative (in case we get a match) |
|
beq t0, $loop # U : |
|
|
|
$found: negq t0, t1 # E : clear all but least set bit |
|
and t0, t1, t0 # E : |
|
and t0, t3, t1 # E : bit set iff byte was the char |
|
addq v0, a2, v0 # E : Add in the bit number from above |
|
|
|
cmoveq t1, $31, v0 # E : Two mapping slots, latency = 2 |
|
nop |
|
nop |
|
ret # L0 : |
|
|
|
.end strchr |
|
EXPORT_SYMBOL(strchr)
|
|
|