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! Copyright (C) 2013 Imagination Technologies Ltd.
!
! Licensed under LGPL v2.1 or later, see the file COPYING.LIB in this tarball.
.text
.global _memchr
.type _memchr,function
! D0Ar6 src
! D0Ar2 c
! D1Ar3 n
_memchr:
CMP D1Ar3, #0
BEQ $Lexit_fail
!! convert c to unsigned char
AND D0Ar2,D0Ar2,#0xff
MOV D0Ar6, D1Ar1
MOV D1Ar5, D0Ar6
!! test alignment
AND D1Ar5, D1Ar5, #7
CMP D1Ar5, #0
BNZ $Lunaligned_loop
!! length must be greater than or equal to 8 for aligned loop
CMP D1Ar3, #8
BGE $Laligned_setup
$Lunaligned_loop:
!! get 1 char from s
GETB D0Re0, [D0Ar6++]
!! increase alignment counter
ADD D1Ar5, D1Ar5, #1
!! decrement n
SUB D1Ar3, D1Ar3, #1
!! exit if we have a match
CMP D0Re0, D0Ar2
BZ $Lexit_success1
!! exit if we have hit the end of the string
CMP D1Ar3, #0
BZ $Lexit_fail
!! fall through if the buffer is aligned now
CMP D1Ar5, #8
BNE $Lunaligned_loop
!! fall through if there is more than 8 bytes left
CMP D1Ar3, #8
BLT $Lunaligned_loop
$Laligned_setup:
!! fill the c into 4 bytes
MOV D0Ar4, D0Ar2
LSL D0Ar4, D0Ar4, #8
ADD D0Ar4, D0Ar4, D0Ar2
LSL D0Ar4, D0Ar4, #8
ADD D0Ar4, D0Ar4, D0Ar2
LSL D0Ar4, D0Ar4, #8
ADD D0Ar4, D0Ar4, D0Ar2
!! divide n by 8
MOV D1Ar5, D1Ar3
LSR D1Ar5, D1Ar5, #3
$Laligned_loop:
!! get 8 chars from s
GETL D0Re0, D1Re0, [D0Ar6++]
!! decrement loop counter
SUB D1Ar5, D1Ar5, #1
!! test first 4 chars
XOR D0Re0, D0Re0, D0Ar4
!! test second 4 chars
MOV D0Ar2, D1Re0
XOR D1Re0, D0Ar2, D0Ar4
!! check for matches in the first 4 chars
MOV D0Ar2, D0Re0
ADDT D0Re0, D0Re0, #HI(0xfefefeff)
ADD D0Re0, D0Re0, #LO(0xfefefeff)
XOR D0Ar2, D0Ar2, #-1
AND D0Re0, D0Re0, D0Ar2
ANDMT D0Re0, D0Re0, #HI(0x80808080)
ANDMB D0Re0, D0Re0, #LO(0x80808080)
CMP D0Re0, #0
BNZ $Lmatch_word1
!! check for matches in the second 4 chars
MOV D1Ar1, D1Re0
ADDT D1Re0, D1Re0, #HI(0xfefefeff)
ADD D1Re0, D1Re0, #LO(0xfefefeff)
XOR D1Ar1, D1Ar1, #-1
AND D1Re0, D1Re0, D1Ar1
ANDMT D1Re0, D1Re0, #HI(0x80808080)
ANDMB D1Re0, D1Re0, #LO(0x80808080)
CMP D1Re0, #0
BNZ $Lmatch_word2
!! check if we have reached the end of the buffer
CMP D1Ar5, #0
BNE $Laligned_loop
!! exit if there are no chars left to check
AND D1Ar3, D1Ar3, #7
CMP D1Ar3, #0
BZ $Lexit_fail
!! recover c
AND D0Ar2, D0Ar4, #0xff
$Lbyte_loop:
!! get 1 char from s
GETB D0Re0, [D0Ar6++]
!! decrement n
SUB D1Ar3, D1Ar3, #1
!! exit if we have a match
CMP D0Re0, D0Ar2
BZ $Lexit_success1
!! fall through if we have run out of chars
CMP D1Ar3, #0
BNE $Lbyte_loop
$Lexit_fail:
MOV D0Re0, #0
B $Lend
$Lmatch_word1:
!! move the match word into D1Re0
MOV D1Re0, D0Re0
!! roll back the buffer pointer by 4 chars
SUB D0Ar6, D0Ar6, #4
$Lmatch_word2:
!! roll back the buffer pointer by 4 chars
SUB D0Ar6, D0Ar6, #4
!! exit if lowest byte is 0
MOV D1Ar1, D1Re0
AND D1Ar1, D1Ar1, #0xff
CMP D1Ar1, #0
BNE $Lexit_success2
!! advance buffer pointer to the next char
ADD D0Ar6, D0Ar6, #1
!! shift in the next lowest byte
LSR D1Re0, D1Re0, #8
!! exit if lowest byte is 0
MOV D1Ar1, D1Re0
AND D1Ar1, D1Ar1, #0xff
CMP D1Ar1, #0
BNE $Lexit_success2
!! advance buffer pointer to the next char
ADD D0Ar6, D0Ar6, #1
!! shift in the next lowest byte
LSR D1Re0, D1Re0, #8
!! exit if lowest byte is 0
MOV D1Ar1, D1Re0
AND D1Ar1, D1Ar1, #0xff
CMP D1Ar1, #0
BNE $Lexit_success2
!! the match must be in the last byte, exit
ADD D0Ar6, D0Ar6, #1
B $Lexit_success2
$Lexit_success1:
SUB D0Ar6, D0Ar6, #1
$Lexit_success2:
!! return the buffer pointer
MOV D0Re0, D0Ar6
$Lend:
MOV PC, D1RtP
.size _memchr,.-_memchr
libc_hidden_def(memchr)
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