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/* Optimized version of the standard memchr() function.
This file is part of the GNU C Library.
Copyright (C) 2000, 2001, 2003 Free Software Foundation, Inc.
Contributed by Dan Pop <Dan.Pop@cern.ch>.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
/* Return: the address of the first occurence of chr in str or NULL
Inputs:
in0: str
in1: chr
in2: byte count
This implementation assumes little endian mode. For big endian mode,
the instruction czx1.r should be replaced by czx1.l.
The algorithm is fairly straightforward: search byte by byte until we
we get to a word aligned address, then search word by word as much as
possible; the remaining few bytes are searched one at a time.
The word by word search is performed by xor-ing the word with a word
containing chr in every byte. If there is a hit, the result will
contain a zero byte in the corresponding position. The presence and
position of that zero byte is detected with a czx instruction.
All the loops in this function could have had the internal branch removed
if br.ctop and br.cloop could be predicated :-(. */
#include <sysdep.h>
#undef ret
#define saved_pr r15
#define saved_lc r16
#define chr r17
#define len r18
#define pos0 r20
#define val r21
#define tmp r24
#define chrx8 r25
#define loopcnt r30
#define str in0
ENTRY(__memchr)
.prologue
alloc r2 = ar.pfs, 3, 0, 29, 32
#include "softpipe.h"
.rotr value[MEMLAT+1], addr[MEMLAT+3], aux[2], poschr[2]
.rotp p[MEMLAT+3]
.save ar.lc, saved_lc
mov saved_lc = ar.lc /* save the loop counter */
.save pr, saved_pr
mov saved_pr = pr /* save the predicates */
.body
mov ret0 = str
and tmp = 7, str /* tmp = str % 8 */
cmp.ne p7, p0 = r0, r0 /* clear p7 */
extr.u chr = in1, 0, 8 /* chr = (unsigned char) in1 */
mov len = in2
cmp.gtu p6, p0 = 16, in2 /* use a simple loop for short */
(p6) br.cond.spnt .srchfew ;; /* searches */
sub loopcnt = 8, tmp /* loopcnt = 8 - tmp */
cmp.eq p6, p0 = tmp, r0
(p6) br.cond.sptk .str_aligned;;
sub len = len, loopcnt
adds loopcnt = -1, loopcnt;;
mov ar.lc = loopcnt
.l1:
ld1 val = [ret0], 1
;;
cmp.eq p6, p0 = val, chr
(p6) br.cond.spnt .foundit
br.cloop.sptk .l1 ;;
.str_aligned:
cmp.ne p6, p0 = r0, r0 /* clear p6 */
shr.u loopcnt = len, 3 /* loopcnt = len / 8 */
and len = 7, len ;; /* remaining len = len & 7 */
adds loopcnt = -1, loopcnt
mov ar.ec = MEMLAT + 3
mux1 chrx8 = chr, @brcst ;; /* get a word full of chr */
mov ar.lc = loopcnt
mov pr.rot = 1 << 16 ;;
.l2:
(p[0]) mov addr[0] = ret0
(p[0]) ld8 value[0] = [ret0], 8
(p[MEMLAT]) xor aux[0] = value[MEMLAT], chrx8
(p[MEMLAT+1]) czx1.r poschr[0] = aux[1]
(p[MEMLAT+2]) cmp.ne p7, p0 = 8, poschr[1]
(p7) br.cond.dpnt .foundit
br.ctop.dptk .l2
.srchfew:
adds loopcnt = -1, len
cmp.eq p6, p0 = len, r0
(p6) br.cond.spnt .notfound ;;
mov ar.lc = loopcnt
.l3:
ld1 val = [ret0], 1
;;
cmp.eq p6, p0 = val, chr
(p6) br.cond.dpnt .foundit
br.cloop.sptk .l3 ;;
.notfound:
cmp.ne p6, p0 = r0, r0 /* clear p6 (p7 was already 0 when we got here) */
mov ret0 = r0 ;; /* return NULL */
.foundit:
.pred.rel "mutex" p6, p7
(p6) adds ret0 = -1, ret0 /* if we got here from l1 or l3 */
(p7) add ret0 = addr[MEMLAT+2], poschr[1] /* if we got here from l2 */
mov pr = saved_pr, -1
mov ar.lc = saved_lc
br.ret.sptk.many b0
END(__memchr)
weak_alias(__memchr, memchr)
weak_alias(__memchr, __ubp_memchr)
libc_hidden_def(memchr)
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