mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-22 13:00:06 +00:00
688903eb3e
* 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.
185 lines
5.4 KiB
ArmAsm
185 lines
5.4 KiB
ArmAsm
/* Copyright (C) 2012-2018 Free Software Foundation, Inc.
|
|
|
|
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/>. */
|
|
|
|
/* Assumptions:
|
|
*
|
|
* ARMv8-a, AArch64
|
|
*/
|
|
|
|
#include <sysdep.h>
|
|
|
|
#define REP8_01 0x0101010101010101
|
|
#define REP8_7f 0x7f7f7f7f7f7f7f7f
|
|
#define REP8_80 0x8080808080808080
|
|
|
|
/* Parameters and result. */
|
|
#define src1 x0
|
|
#define src2 x1
|
|
#define result x0
|
|
|
|
/* Internal variables. */
|
|
#define data1 x2
|
|
#define data1w w2
|
|
#define data2 x3
|
|
#define data2w w3
|
|
#define has_nul x4
|
|
#define diff x5
|
|
#define syndrome x6
|
|
#define tmp1 x7
|
|
#define tmp2 x8
|
|
#define tmp3 x9
|
|
#define zeroones x10
|
|
#define pos x11
|
|
|
|
/* Start of performance-critical section -- one 64B cache line. */
|
|
ENTRY_ALIGN(strcmp, 6)
|
|
|
|
DELOUSE (0)
|
|
DELOUSE (1)
|
|
eor tmp1, src1, src2
|
|
mov zeroones, #REP8_01
|
|
tst tmp1, #7
|
|
b.ne L(misaligned8)
|
|
ands tmp1, src1, #7
|
|
b.ne L(mutual_align)
|
|
/* NUL detection works on the principle that (X - 1) & (~X) & 0x80
|
|
(=> (X - 1) & ~(X | 0x7f)) is non-zero iff a byte is zero, and
|
|
can be done in parallel across the entire word. */
|
|
L(loop_aligned):
|
|
ldr data1, [src1], #8
|
|
ldr data2, [src2], #8
|
|
L(start_realigned):
|
|
sub tmp1, data1, zeroones
|
|
orr tmp2, data1, #REP8_7f
|
|
eor diff, data1, data2 /* Non-zero if differences found. */
|
|
bic has_nul, tmp1, tmp2 /* Non-zero if NUL terminator. */
|
|
orr syndrome, diff, has_nul
|
|
cbz syndrome, L(loop_aligned)
|
|
/* End of performance-critical section -- one 64B cache line. */
|
|
|
|
L(end):
|
|
#ifndef __AARCH64EB__
|
|
rev syndrome, syndrome
|
|
rev data1, data1
|
|
/* The MS-non-zero bit of the syndrome marks either the first bit
|
|
that is different, or the top bit of the first zero byte.
|
|
Shifting left now will bring the critical information into the
|
|
top bits. */
|
|
clz pos, syndrome
|
|
rev data2, data2
|
|
lsl data1, data1, pos
|
|
lsl data2, data2, pos
|
|
/* But we need to zero-extend (char is unsigned) the value and then
|
|
perform a signed 32-bit subtraction. */
|
|
lsr data1, data1, #56
|
|
sub result, data1, data2, lsr #56
|
|
RET
|
|
#else
|
|
/* For big-endian we cannot use the trick with the syndrome value
|
|
as carry-propagation can corrupt the upper bits if the trailing
|
|
bytes in the string contain 0x01. */
|
|
/* However, if there is no NUL byte in the dword, we can generate
|
|
the result directly. We can't just subtract the bytes as the
|
|
MSB might be significant. */
|
|
cbnz has_nul, 1f
|
|
cmp data1, data2
|
|
cset result, ne
|
|
cneg result, result, lo
|
|
RET
|
|
1:
|
|
/* Re-compute the NUL-byte detection, using a byte-reversed value. */
|
|
rev tmp3, data1
|
|
sub tmp1, tmp3, zeroones
|
|
orr tmp2, tmp3, #REP8_7f
|
|
bic has_nul, tmp1, tmp2
|
|
rev has_nul, has_nul
|
|
orr syndrome, diff, has_nul
|
|
clz pos, syndrome
|
|
/* The MS-non-zero bit of the syndrome marks either the first bit
|
|
that is different, or the top bit of the first zero byte.
|
|
Shifting left now will bring the critical information into the
|
|
top bits. */
|
|
lsl data1, data1, pos
|
|
lsl data2, data2, pos
|
|
/* But we need to zero-extend (char is unsigned) the value and then
|
|
perform a signed 32-bit subtraction. */
|
|
lsr data1, data1, #56
|
|
sub result, data1, data2, lsr #56
|
|
RET
|
|
#endif
|
|
|
|
L(mutual_align):
|
|
/* Sources are mutually aligned, but are not currently at an
|
|
alignment boundary. Round down the addresses and then mask off
|
|
the bytes that preceed the start point. */
|
|
bic src1, src1, #7
|
|
bic src2, src2, #7
|
|
lsl tmp1, tmp1, #3 /* Bytes beyond alignment -> bits. */
|
|
ldr data1, [src1], #8
|
|
neg tmp1, tmp1 /* Bits to alignment -64. */
|
|
ldr data2, [src2], #8
|
|
mov tmp2, #~0
|
|
#ifdef __AARCH64EB__
|
|
/* Big-endian. Early bytes are at MSB. */
|
|
lsl tmp2, tmp2, tmp1 /* Shift (tmp1 & 63). */
|
|
#else
|
|
/* Little-endian. Early bytes are at LSB. */
|
|
lsr tmp2, tmp2, tmp1 /* Shift (tmp1 & 63). */
|
|
#endif
|
|
orr data1, data1, tmp2
|
|
orr data2, data2, tmp2
|
|
b L(start_realigned)
|
|
|
|
L(misaligned8):
|
|
/* Align SRC1 to 8 bytes and then compare 8 bytes at a time, always
|
|
checking to make sure that we don't access beyond page boundary in
|
|
SRC2. */
|
|
tst src1, #7
|
|
b.eq L(loop_misaligned)
|
|
L(do_misaligned):
|
|
ldrb data1w, [src1], #1
|
|
ldrb data2w, [src2], #1
|
|
cmp data1w, #1
|
|
ccmp data1w, data2w, #0, cs /* NZCV = 0b0000. */
|
|
b.ne L(done)
|
|
tst src1, #7
|
|
b.ne L(misaligned8)
|
|
|
|
L(loop_misaligned):
|
|
/* Test if we are within the last dword of the end of a 4K page. If
|
|
yes then jump back to the misaligned loop to copy a byte at a time. */
|
|
and tmp1, src2, #0xff8
|
|
eor tmp1, tmp1, #0xff8
|
|
cbz tmp1, L(do_misaligned)
|
|
ldr data1, [src1], #8
|
|
ldr data2, [src2], #8
|
|
|
|
sub tmp1, data1, zeroones
|
|
orr tmp2, data1, #REP8_7f
|
|
eor diff, data1, data2 /* Non-zero if differences found. */
|
|
bic has_nul, tmp1, tmp2 /* Non-zero if NUL terminator. */
|
|
orr syndrome, diff, has_nul
|
|
cbz syndrome, L(loop_misaligned)
|
|
b L(end)
|
|
|
|
L(done):
|
|
sub result, data1, data2
|
|
RET
|
|
END(strcmp)
|
|
libc_hidden_builtin_def (strcmp)
|