mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-15 17:40:06 +00:00
04277e02d7
* All files with FSF copyright notices: Update copyright dates using scripts/update-copyrights. * locale/programs/charmap-kw.h: Regenerated. * locale/programs/locfile-kw.h: Likewise.
103 lines
3.3 KiB
ArmAsm
103 lines
3.3 KiB
ArmAsm
/* Optimized strlen implementation for PowerPC32/POWER7 using cmpb insn.
|
|
Copyright (C) 2010-2019 Free Software Foundation, Inc.
|
|
Contributed by Luis Machado <luisgpm@br.ibm.com>.
|
|
This file is part of the GNU C Library.
|
|
|
|
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/>. */
|
|
|
|
#include <sysdep.h>
|
|
|
|
/* int [r3] strlen (char *s [r3]) */
|
|
.machine power7
|
|
ENTRY (strlen)
|
|
CALL_MCOUNT
|
|
dcbt 0,r3
|
|
clrrwi r4,r3,2 /* Align the address to word boundary. */
|
|
rlwinm r6,r3,3,27,28 /* Calculate padding. */
|
|
li r0,0 /* Word with null chars to use with cmpb. */
|
|
li r5,-1 /* MASK = 0xffffffffffffffff. */
|
|
lwz r12,0(r4) /* Load word from memory. */
|
|
#ifdef __LITTLE_ENDIAN__
|
|
slw r5,r5,r6
|
|
#else
|
|
srw r5,r5,r6 /* MASK = MASK >> padding. */
|
|
#endif
|
|
orc r9,r12,r5 /* Mask bits that are not part of the string. */
|
|
cmpb r10,r9,r0 /* Check for null bytes in WORD1. */
|
|
cmpwi cr7,r10,0 /* If r10 == 0, no null's have been found. */
|
|
bne cr7,L(done)
|
|
|
|
mtcrf 0x01,r4
|
|
|
|
/* Are we now aligned to a doubleword boundary? If so, skip to
|
|
the main loop. Otherwise, go through the alignment code. */
|
|
|
|
bt 29,L(loop)
|
|
|
|
/* Handle WORD2 of pair. */
|
|
lwzu r12,4(r4)
|
|
cmpb r10,r12,r0
|
|
cmpwi cr7,r10,0
|
|
bne cr7,L(done)
|
|
|
|
/* Main loop to look for the end of the string. Since it's a
|
|
small loop (< 8 instructions), align it to 32-bytes. */
|
|
.p2align 5
|
|
L(loop):
|
|
/* Load two words, compare and merge in a
|
|
single register for speed. This is an attempt
|
|
to speed up the null-checking process for bigger strings. */
|
|
|
|
lwz r12, 4(r4)
|
|
lwzu r11, 8(r4)
|
|
cmpb r10,r12,r0
|
|
cmpb r9,r11,r0
|
|
or r8,r9,r10 /* Merge everything in one word. */
|
|
cmpwi cr7,r8,0
|
|
beq cr7,L(loop)
|
|
|
|
/* OK, one (or both) of the words contains a null byte. Check
|
|
the first word and decrement the address in case the first
|
|
word really contains a null byte. */
|
|
|
|
cmpwi cr6,r10,0
|
|
addi r4,r4,-4
|
|
bne cr6,L(done)
|
|
|
|
/* The null byte must be in the second word. Adjust the address
|
|
again and move the result of cmpb to r10 so we can calculate the
|
|
length. */
|
|
|
|
mr r10,r9
|
|
addi r4,r4,4
|
|
|
|
/* r10 has the output of the cmpb instruction, that is, it contains
|
|
0xff in the same position as the null byte in the original
|
|
word from the string. Use that to calculate the length. */
|
|
L(done):
|
|
#ifdef __LITTLE_ENDIAN__
|
|
addi r9, r10, -1 /* Form a mask from trailing zeros. */
|
|
andc r9, r9, r10
|
|
popcntw r0, r9 /* Count the bits in the mask. */
|
|
#else
|
|
cntlzw r0,r10 /* Count leading zeros before the match. */
|
|
#endif
|
|
subf r5,r3,r4
|
|
srwi r0,r0,3 /* Convert leading zeros to bytes. */
|
|
add r3,r5,r0 /* Compute final length. */
|
|
blr
|
|
END (strlen)
|
|
libc_hidden_builtin_def (strlen)
|