|
Packit |
6c4009 |
/* Copyright (C) 2013-2018 Free Software Foundation, Inc.
|
|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
This file is part of the GNU C Library.
|
|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
The GNU C Library is free software; you can redistribute it and/or
|
|
Packit |
6c4009 |
modify it under the terms of the GNU Lesser General Public
|
|
Packit |
6c4009 |
License as published by the Free Software Foundation; either
|
|
Packit |
6c4009 |
version 2.1 of the License, or (at your option) any later version.
|
|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
The GNU C Library is distributed in the hope that it will be useful,
|
|
Packit |
6c4009 |
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
Packit |
6c4009 |
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
Packit |
6c4009 |
Lesser General Public License for more details.
|
|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
You should have received a copy of the GNU Lesser General Public
|
|
Packit |
6c4009 |
License along with the GNU C Library. If not, see
|
|
Packit |
6c4009 |
<http://www.gnu.org/licenses/>. */
|
|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
#include <sysdep.h>
|
|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
/* Assumptions:
|
|
Packit |
6c4009 |
*
|
|
Packit |
6c4009 |
* ARMv8-a, AArch64
|
|
Packit |
6c4009 |
*/
|
|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
#define REP8_01 0x0101010101010101
|
|
Packit |
6c4009 |
#define REP8_7f 0x7f7f7f7f7f7f7f7f
|
|
Packit |
6c4009 |
#define REP8_80 0x8080808080808080
|
|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
/* Parameters and result. */
|
|
Packit |
6c4009 |
#define src1 x0
|
|
Packit |
6c4009 |
#define src2 x1
|
|
Packit |
6c4009 |
#define limit x2
|
|
Packit |
6c4009 |
#define result x0
|
|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
/* Internal variables. */
|
|
Packit |
6c4009 |
#define data1 x3
|
|
Packit |
6c4009 |
#define data1w w3
|
|
Packit |
6c4009 |
#define data2 x4
|
|
Packit |
6c4009 |
#define data2w w4
|
|
Packit |
6c4009 |
#define has_nul x5
|
|
Packit |
6c4009 |
#define diff x6
|
|
Packit |
6c4009 |
#define syndrome x7
|
|
Packit |
6c4009 |
#define tmp1 x8
|
|
Packit |
6c4009 |
#define tmp2 x9
|
|
Packit |
6c4009 |
#define tmp3 x10
|
|
Packit |
6c4009 |
#define zeroones x11
|
|
Packit |
6c4009 |
#define pos x12
|
|
Packit |
6c4009 |
#define limit_wd x13
|
|
Packit |
6c4009 |
#define mask x14
|
|
Packit |
6c4009 |
#define endloop x15
|
|
Packit |
6c4009 |
#define count mask
|
|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
ENTRY_ALIGN_AND_PAD (strncmp, 6, 7)
|
|
Packit |
6c4009 |
DELOUSE (0)
|
|
Packit |
6c4009 |
DELOUSE (1)
|
|
Packit |
6c4009 |
DELOUSE (2)
|
|
Packit |
6c4009 |
cbz limit, L(ret0)
|
|
Packit |
6c4009 |
eor tmp1, src1, src2
|
|
Packit |
6c4009 |
mov zeroones, #REP8_01
|
|
Packit |
6c4009 |
tst tmp1, #7
|
|
Packit |
6c4009 |
and count, src1, #7
|
|
Packit |
6c4009 |
b.ne L(misaligned8)
|
|
Packit |
6c4009 |
cbnz count, L(mutual_align)
|
|
Packit |
6c4009 |
/* Calculate the number of full and partial words -1. */
|
|
Packit |
6c4009 |
sub limit_wd, limit, #1 /* limit != 0, so no underflow. */
|
|
Packit |
6c4009 |
lsr limit_wd, limit_wd, #3 /* Convert to Dwords. */
|
|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
/* NUL detection works on the principle that (X - 1) & (~X) & 0x80
|
|
Packit |
6c4009 |
(=> (X - 1) & ~(X | 0x7f)) is non-zero iff a byte is zero, and
|
|
Packit |
6c4009 |
can be done in parallel across the entire word. */
|
|
Packit |
6c4009 |
/* Start of performance-critical section -- one 64B cache line. */
|
|
Packit |
6c4009 |
L(loop_aligned):
|
|
Packit |
6c4009 |
ldr data1, [src1], #8
|
|
Packit |
6c4009 |
ldr data2, [src2], #8
|
|
Packit |
6c4009 |
L(start_realigned):
|
|
Packit |
6c4009 |
subs limit_wd, limit_wd, #1
|
|
Packit |
6c4009 |
sub tmp1, data1, zeroones
|
|
Packit |
6c4009 |
orr tmp2, data1, #REP8_7f
|
|
Packit |
6c4009 |
eor diff, data1, data2 /* Non-zero if differences found. */
|
|
Packit |
6c4009 |
csinv endloop, diff, xzr, pl /* Last Dword or differences. */
|
|
Packit |
6c4009 |
bics has_nul, tmp1, tmp2 /* Non-zero if NUL terminator. */
|
|
Packit |
6c4009 |
ccmp endloop, #0, #0, eq
|
|
Packit |
6c4009 |
b.eq L(loop_aligned)
|
|
Packit |
6c4009 |
/* End of performance-critical section -- one 64B cache line. */
|
|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
/* Not reached the limit, must have found the end or a diff. */
|
|
Packit |
6c4009 |
tbz limit_wd, #63, L(not_limit)
|
|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
/* Limit % 8 == 0 => all bytes significant. */
|
|
Packit |
6c4009 |
ands limit, limit, #7
|
|
Packit |
6c4009 |
b.eq L(not_limit)
|
|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
lsl limit, limit, #3 /* Bits -> bytes. */
|
|
Packit |
6c4009 |
mov mask, #~0
|
|
Packit |
6c4009 |
#ifdef __AARCH64EB__
|
|
Packit |
6c4009 |
lsr mask, mask, limit
|
|
Packit |
6c4009 |
#else
|
|
Packit |
6c4009 |
lsl mask, mask, limit
|
|
Packit |
6c4009 |
#endif
|
|
Packit |
6c4009 |
bic data1, data1, mask
|
|
Packit |
6c4009 |
bic data2, data2, mask
|
|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
/* Make sure that the NUL byte is marked in the syndrome. */
|
|
Packit |
6c4009 |
orr has_nul, has_nul, mask
|
|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
L(not_limit):
|
|
Packit |
6c4009 |
orr syndrome, diff, has_nul
|
|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
#ifndef __AARCH64EB__
|
|
Packit |
6c4009 |
rev syndrome, syndrome
|
|
Packit |
6c4009 |
rev data1, data1
|
|
Packit |
6c4009 |
/* The MS-non-zero bit of the syndrome marks either the first bit
|
|
Packit |
6c4009 |
that is different, or the top bit of the first zero byte.
|
|
Packit |
6c4009 |
Shifting left now will bring the critical information into the
|
|
Packit |
6c4009 |
top bits. */
|
|
Packit |
6c4009 |
clz pos, syndrome
|
|
Packit |
6c4009 |
rev data2, data2
|
|
Packit |
6c4009 |
lsl data1, data1, pos
|
|
Packit |
6c4009 |
lsl data2, data2, pos
|
|
Packit |
6c4009 |
/* But we need to zero-extend (char is unsigned) the value and then
|
|
Packit |
6c4009 |
perform a signed 32-bit subtraction. */
|
|
Packit |
6c4009 |
lsr data1, data1, #56
|
|
Packit |
6c4009 |
sub result, data1, data2, lsr #56
|
|
Packit |
6c4009 |
RET
|
|
Packit |
6c4009 |
#else
|
|
Packit |
6c4009 |
/* For big-endian we cannot use the trick with the syndrome value
|
|
Packit |
6c4009 |
as carry-propagation can corrupt the upper bits if the trailing
|
|
Packit |
6c4009 |
bytes in the string contain 0x01. */
|
|
Packit |
6c4009 |
/* However, if there is no NUL byte in the dword, we can generate
|
|
Packit |
6c4009 |
the result directly. We can't just subtract the bytes as the
|
|
Packit |
6c4009 |
MSB might be significant. */
|
|
Packit |
6c4009 |
cbnz has_nul, 1f
|
|
Packit |
6c4009 |
cmp data1, data2
|
|
Packit |
6c4009 |
cset result, ne
|
|
Packit |
6c4009 |
cneg result, result, lo
|
|
Packit |
6c4009 |
RET
|
|
Packit |
6c4009 |
1:
|
|
Packit |
6c4009 |
/* Re-compute the NUL-byte detection, using a byte-reversed value. */
|
|
Packit |
6c4009 |
rev tmp3, data1
|
|
Packit |
6c4009 |
sub tmp1, tmp3, zeroones
|
|
Packit |
6c4009 |
orr tmp2, tmp3, #REP8_7f
|
|
Packit |
6c4009 |
bic has_nul, tmp1, tmp2
|
|
Packit |
6c4009 |
rev has_nul, has_nul
|
|
Packit |
6c4009 |
orr syndrome, diff, has_nul
|
|
Packit |
6c4009 |
clz pos, syndrome
|
|
Packit |
6c4009 |
/* The MS-non-zero bit of the syndrome marks either the first bit
|
|
Packit |
6c4009 |
that is different, or the top bit of the first zero byte.
|
|
Packit |
6c4009 |
Shifting left now will bring the critical information into the
|
|
Packit |
6c4009 |
top bits. */
|
|
Packit |
6c4009 |
lsl data1, data1, pos
|
|
Packit |
6c4009 |
lsl data2, data2, pos
|
|
Packit |
6c4009 |
/* But we need to zero-extend (char is unsigned) the value and then
|
|
Packit |
6c4009 |
perform a signed 32-bit subtraction. */
|
|
Packit |
6c4009 |
lsr data1, data1, #56
|
|
Packit |
6c4009 |
sub result, data1, data2, lsr #56
|
|
Packit |
6c4009 |
RET
|
|
Packit |
6c4009 |
#endif
|
|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
L(mutual_align):
|
|
Packit |
6c4009 |
/* Sources are mutually aligned, but are not currently at an
|
|
Packit |
6c4009 |
alignment boundary. Round down the addresses and then mask off
|
|
Packit |
6c4009 |
the bytes that precede the start point.
|
|
Packit |
6c4009 |
We also need to adjust the limit calculations, but without
|
|
Packit |
6c4009 |
overflowing if the limit is near ULONG_MAX. */
|
|
Packit |
6c4009 |
bic src1, src1, #7
|
|
Packit |
6c4009 |
bic src2, src2, #7
|
|
Packit |
6c4009 |
ldr data1, [src1], #8
|
|
Packit |
6c4009 |
neg tmp3, count, lsl #3 /* 64 - bits(bytes beyond align). */
|
|
Packit |
6c4009 |
ldr data2, [src2], #8
|
|
Packit |
6c4009 |
mov tmp2, #~0
|
|
Packit |
6c4009 |
sub limit_wd, limit, #1 /* limit != 0, so no underflow. */
|
|
Packit |
6c4009 |
#ifdef __AARCH64EB__
|
|
Packit |
6c4009 |
/* Big-endian. Early bytes are at MSB. */
|
|
Packit |
6c4009 |
lsl tmp2, tmp2, tmp3 /* Shift (count & 63). */
|
|
Packit |
6c4009 |
#else
|
|
Packit |
6c4009 |
/* Little-endian. Early bytes are at LSB. */
|
|
Packit |
6c4009 |
lsr tmp2, tmp2, tmp3 /* Shift (count & 63). */
|
|
Packit |
6c4009 |
#endif
|
|
Packit |
6c4009 |
and tmp3, limit_wd, #7
|
|
Packit |
6c4009 |
lsr limit_wd, limit_wd, #3
|
|
Packit |
6c4009 |
/* Adjust the limit. Only low 3 bits used, so overflow irrelevant. */
|
|
Packit |
6c4009 |
add limit, limit, count
|
|
Packit |
6c4009 |
add tmp3, tmp3, count
|
|
Packit |
6c4009 |
orr data1, data1, tmp2
|
|
Packit |
6c4009 |
orr data2, data2, tmp2
|
|
Packit |
6c4009 |
add limit_wd, limit_wd, tmp3, lsr #3
|
|
Packit |
6c4009 |
b L(start_realigned)
|
|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
.p2align 6
|
|
Packit |
6c4009 |
/* Don't bother with dwords for up to 16 bytes. */
|
|
Packit |
6c4009 |
L(misaligned8):
|
|
Packit |
6c4009 |
cmp limit, #16
|
|
Packit |
6c4009 |
b.hs L(try_misaligned_words)
|
|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
L(byte_loop):
|
|
Packit |
6c4009 |
/* Perhaps we can do better than this. */
|
|
Packit |
6c4009 |
ldrb data1w, [src1], #1
|
|
Packit |
6c4009 |
ldrb data2w, [src2], #1
|
|
Packit |
6c4009 |
subs limit, limit, #1
|
|
Packit |
6c4009 |
ccmp data1w, #1, #0, hi /* NZCV = 0b0000. */
|
|
Packit |
6c4009 |
ccmp data1w, data2w, #0, cs /* NZCV = 0b0000. */
|
|
Packit |
6c4009 |
b.eq L(byte_loop)
|
|
Packit |
6c4009 |
L(done):
|
|
Packit |
6c4009 |
sub result, data1, data2
|
|
Packit |
6c4009 |
RET
|
|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
/* Align the SRC1 to a dword by doing a bytewise compare and then do
|
|
Packit |
6c4009 |
the dword loop. */
|
|
Packit |
6c4009 |
L(try_misaligned_words):
|
|
Packit |
6c4009 |
lsr limit_wd, limit, #3
|
|
Packit |
6c4009 |
cbz count, L(do_misaligned)
|
|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
neg count, count
|
|
Packit |
6c4009 |
and count, count, #7
|
|
Packit |
6c4009 |
sub limit, limit, count
|
|
Packit |
6c4009 |
lsr limit_wd, limit, #3
|
|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
L(page_end_loop):
|
|
Packit |
6c4009 |
ldrb data1w, [src1], #1
|
|
Packit |
6c4009 |
ldrb data2w, [src2], #1
|
|
Packit |
6c4009 |
cmp data1w, #1
|
|
Packit |
6c4009 |
ccmp data1w, data2w, #0, cs /* NZCV = 0b0000. */
|
|
Packit |
6c4009 |
b.ne L(done)
|
|
Packit |
6c4009 |
subs count, count, #1
|
|
Packit |
6c4009 |
b.hi L(page_end_loop)
|
|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
L(do_misaligned):
|
|
Packit |
6c4009 |
/* Prepare ourselves for the next page crossing. Unlike the aligned
|
|
Packit |
6c4009 |
loop, we fetch 1 less dword because we risk crossing bounds on
|
|
Packit |
6c4009 |
SRC2. */
|
|
Packit |
6c4009 |
mov count, #8
|
|
Packit |
6c4009 |
subs limit_wd, limit_wd, #1
|
|
Packit |
6c4009 |
b.lo L(done_loop)
|
|
Packit |
6c4009 |
L(loop_misaligned):
|
|
Packit |
6c4009 |
and tmp2, src2, #0xff8
|
|
Packit |
6c4009 |
eor tmp2, tmp2, #0xff8
|
|
Packit |
6c4009 |
cbz tmp2, L(page_end_loop)
|
|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
ldr data1, [src1], #8
|
|
Packit |
6c4009 |
ldr data2, [src2], #8
|
|
Packit |
6c4009 |
sub tmp1, data1, zeroones
|
|
Packit |
6c4009 |
orr tmp2, data1, #REP8_7f
|
|
Packit |
6c4009 |
eor diff, data1, data2 /* Non-zero if differences found. */
|
|
Packit |
6c4009 |
bics has_nul, tmp1, tmp2 /* Non-zero if NUL terminator. */
|
|
Packit |
6c4009 |
ccmp diff, #0, #0, eq
|
|
Packit |
6c4009 |
b.ne L(not_limit)
|
|
Packit |
6c4009 |
subs limit_wd, limit_wd, #1
|
|
Packit |
6c4009 |
b.pl L(loop_misaligned)
|
|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
L(done_loop):
|
|
Packit |
6c4009 |
/* We found a difference or a NULL before the limit was reached. */
|
|
Packit |
6c4009 |
and limit, limit, #7
|
|
Packit |
6c4009 |
cbz limit, L(not_limit)
|
|
Packit |
6c4009 |
/* Read the last word. */
|
|
Packit |
6c4009 |
sub src1, src1, 8
|
|
Packit |
6c4009 |
sub src2, src2, 8
|
|
Packit |
6c4009 |
ldr data1, [src1, limit]
|
|
Packit |
6c4009 |
ldr data2, [src2, limit]
|
|
Packit |
6c4009 |
sub tmp1, data1, zeroones
|
|
Packit |
6c4009 |
orr tmp2, data1, #REP8_7f
|
|
Packit |
6c4009 |
eor diff, data1, data2 /* Non-zero if differences found. */
|
|
Packit |
6c4009 |
bics has_nul, tmp1, tmp2 /* Non-zero if NUL terminator. */
|
|
Packit |
6c4009 |
ccmp diff, #0, #0, eq
|
|
Packit |
6c4009 |
b.ne L(not_limit)
|
|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
L(ret0):
|
|
Packit |
6c4009 |
mov result, #0
|
|
Packit |
6c4009 |
RET
|
|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
END (strncmp)
|
|
Packit |
6c4009 |
libc_hidden_builtin_def (strncmp)
|