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Commit 43de30d3 authored by Sam Tebbs's avatar Sam Tebbs Committed by Will Deacon
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arm64: Import latest version of Cortex Strings' memcmp 

Import the latest version of the former Cortex Strings - now
Arm Optimized Routines - memcmp function based on the upstream
code of string/aarch64/memcmp.S at commit e823e3a from
https://github.com/ARM-software/optimized-routines

Note that for simplicity Arm have chosen to contribute this code
to Linux under GPLv2 rather than the original MIT license.
Signed-off-by: default avatarSam Tebbs <sam.tebbs@arm.com>
[ rm: update attribution and commit message ]
Signed-off-by: default avatarRobin Murphy <robin.murphy@arm.com>
Acked-by: default avatarMark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/2889de2d41054f3f508fb3addad784a3606ef383.1622128527.git.robin.murphy@arm.comSigned-off-by: default avatarWill Deacon <will@kernel.org>
parent c4681547
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arch/arm64/lib/memcmp.S
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/* SPDX-License-Identifier: GPL-2.0-only */
/*
* Copyright (C) 2013 ARM Ltd.
* Copyright (C) 2013 Linaro.
* Copyright (c) 2013-2020, Arm Limited.
*
* This code is based on glibc cortex strings work originally authored by Linaro
* be found @
*
* http://bazaar.launchpad.net/~linaro-toolchain-dev/cortex-strings/trunk/
* files/head:/src/aarch64/
* Adapted from the original at:
* https://github.com/ARM-software/optimized-routines/blob/master/string/aarch64/memcmp.S
*/
#include <linux/linkage.h>
#include <asm/assembler.h>
/*
* compare memory areas(when two memory areas' offset are different,
* alignment handled by the hardware)
*
* Parameters:
* x0 - const memory area 1 pointer
* x1 - const memory area 2 pointer
* x2 - the maximal compare byte length
* Returns:
* x0 - a compare result, maybe less than, equal to, or greater than ZERO
*/
/* Assumptions:
*
* ARMv8-a, AArch64, unaligned accesses.
*/
#define L(label) .L ## label
/* Parameters and result. */
src1 .req x0
src2 .req x1
limit .req x2
result .req x0
#define src1 x0
#define src2 x1
#define limit x2
#define result w0
/* Internal variables. */
data1 .req x3
data1w .req w3
data2 .req x4
data2w .req w4
has_nul .req x5
diff .req x6
endloop .req x7
tmp1 .req x8
tmp2 .req x9
tmp3 .req x10
pos .req x11
limit_wd .req x12
mask .req x13
#define data1 x3
#define data1w w3
#define data1h x4
#define data2 x5
#define data2w w5
#define data2h x6
#define tmp1 x7
#define tmp2 x8
SYM_FUNC_START_WEAK_PI(memcmp)
cbz limit, .Lret0
eor tmp1, src1, src2
tst tmp1, #7
b.ne .Lmisaligned8
ands tmp1, src1, #7
b.ne .Lmutual_align
sub limit_wd, limit, #1 /* limit != 0, so no underflow. */
lsr limit_wd, limit_wd, #3 /* Convert to Dwords. */
/*
* The input source addresses are at alignment boundary.
* Directly compare eight bytes each time.
*/
.Lloop_aligned:
ldr data1, [src1], #8
ldr data2, [src2], #8
.Lstart_realigned:
subs limit_wd, limit_wd, #1
eor diff, data1, data2 /* Non-zero if differences found. */
csinv endloop, diff, xzr, cs /* Last Dword or differences. */
cbz endloop, .Lloop_aligned
/* Not reached the limit, must have found a diff. */
tbz limit_wd, #63, .Lnot_limit
/* Limit % 8 == 0 => the diff is in the last 8 bytes. */
ands limit, limit, #7
b.eq .Lnot_limit
/*
* The remained bytes less than 8. It is needed to extract valid data
* from last eight bytes of the intended memory range.
*/
lsl limit, limit, #3 /* bytes-> bits. */
mov mask, #~0
CPU_BE( lsr mask, mask, limit )
CPU_LE( lsl mask, mask, limit )
bic data1, data1, mask
bic data2, data2, mask
orr diff, diff, mask
b .Lnot_limit
.Lmutual_align:
/*
* Sources are mutually aligned, but are not currently at an
* alignment boundary. Round down the addresses and then mask off
* the bytes that precede the start point.
*/
bic src1, src1, #7
bic src2, src2, #7
ldr data1, [src1], #8
ldr data2, [src2], #8
/*
* We can not add limit with alignment offset(tmp1) here. Since the
* addition probably make the limit overflown.
*/
sub limit_wd, limit, #1/*limit != 0, so no underflow.*/
and tmp3, limit_wd, #7
lsr limit_wd, limit_wd, #3
add tmp3, tmp3, tmp1
add limit_wd, limit_wd, tmp3, lsr #3
add limit, limit, tmp1/* Adjust the limit for the extra. */
lsl tmp1, tmp1, #3/* Bytes beyond alignment -> bits.*/
neg tmp1, tmp1/* Bits to alignment -64. */
mov tmp2, #~0
/*mask off the non-intended bytes before the start address.*/
CPU_BE( lsl tmp2, tmp2, tmp1 )/*Big-endian.Early bytes are at MSB*/
/* Little-endian. Early bytes are at LSB. */
CPU_LE( lsr tmp2, tmp2, tmp1 )
orr data1, data1, tmp2
orr data2, data2, tmp2
b .Lstart_realigned
/*src1 and src2 have different alignment offset.*/
.Lmisaligned8:
cmp limit, #8
b.lo .Ltiny8proc /*limit < 8: compare byte by byte*/
and tmp1, src1, #7
neg tmp1, tmp1
add tmp1, tmp1, #8/*valid length in the first 8 bytes of src1*/
and tmp2, src2, #7
neg tmp2, tmp2
add tmp2, tmp2, #8/*valid length in the first 8 bytes of src2*/
subs tmp3, tmp1, tmp2
csel pos, tmp1, tmp2, hi /*Choose the maximum.*/
sub limit, limit, pos
/*compare the proceeding bytes in the first 8 byte segment.*/
.Ltinycmp:
ldrb data1w, [src1], #1
ldrb data2w, [src2], #1
subs pos, pos, #1
ccmp data1w, data2w, #0, ne /* NZCV = 0b0000. */
b.eq .Ltinycmp
cbnz pos, 1f /*diff occurred before the last byte.*/
cmp data1w, data2w
b.eq .Lstart_align
1:
sub result, data1, data2
subs limit, limit, 8
b.lo L(less8)
ldr data1, [src1], 8
ldr data2, [src2], 8
cmp data1, data2
b.ne L(return)
subs limit, limit, 8
b.gt L(more16)
ldr data1, [src1, limit]
ldr data2, [src2, limit]
b L(return)
L(more16):
ldr data1, [src1], 8
ldr data2, [src2], 8
cmp data1, data2
bne L(return)
/* Jump directly to comparing the last 16 bytes for 32 byte (or less)
strings. */
subs limit, limit, 16
b.ls L(last_bytes)
/* We overlap loads between 0-32 bytes at either side of SRC1 when we
try to align, so limit it only to strings larger than 128 bytes. */
cmp limit, 96
b.ls L(loop16)
/* Align src1 and adjust src2 with bytes not yet done. */
and tmp1, src1, 15
add limit, limit, tmp1
sub src1, src1, tmp1
sub src2, src2, tmp1
/* Loop performing 16 bytes per iteration using aligned src1.
Limit is pre-decremented by 16 and must be larger than zero.
Exit if <= 16 bytes left to do or if the data is not equal. */
.p2align 4
L(loop16):
ldp data1, data1h, [src1], 16
ldp data2, data2h, [src2], 16
subs limit, limit, 16
ccmp data1, data2, 0, hi
ccmp data1h, data2h, 0, eq
b.eq L(loop16)
cmp data1, data2
bne L(return)
mov data1, data1h
mov data2, data2h
cmp data1, data2
bne L(return)
/* Compare last 1-16 bytes using unaligned access. */
L(last_bytes):
add src1, src1, limit
add src2, src2, limit
ldp data1, data1h, [src1]
ldp data2, data2h, [src2]
cmp data1, data2
bne L(return)
mov data1, data1h
mov data2, data2h
cmp data1, data2
/* Compare data bytes and set return value to 0, -1 or 1. */
L(return):
#ifndef __AARCH64EB__
rev data1, data1
rev data2, data2
#endif
cmp data1, data2
L(ret_eq):
cset result, ne
cneg result, result, lo
ret
.Lstart_align:
lsr limit_wd, limit, #3
cbz limit_wd, .Lremain8
ands xzr, src1, #7
b.eq .Lrecal_offset
/*process more leading bytes to make src1 aligned...*/
add src1, src1, tmp3 /*backwards src1 to alignment boundary*/
add src2, src2, tmp3
sub limit, limit, tmp3
lsr limit_wd, limit, #3
cbz limit_wd, .Lremain8
/*load 8 bytes from aligned SRC1..*/
ldr data1, [src1], #8
ldr data2, [src2], #8
subs limit_wd, limit_wd, #1
eor diff, data1, data2 /*Non-zero if differences found.*/
csinv endloop, diff, xzr, ne
cbnz endloop, .Lunequal_proc
/*How far is the current SRC2 from the alignment boundary...*/
and tmp3, tmp3, #7
.Lrecal_offset:/*src1 is aligned now..*/
neg pos, tmp3
.Lloopcmp_proc:
/*
* Divide the eight bytes into two parts. First,backwards the src2
* to an alignment boundary,load eight bytes and compare from
* the SRC2 alignment boundary. If all 8 bytes are equal,then start
* the second part's comparison. Otherwise finish the comparison.
* This special handle can garantee all the accesses are in the
* thread/task space in avoid to overrange access.
*/
ldr data1, [src1,pos]
ldr data2, [src2,pos]
eor diff, data1, data2 /* Non-zero if differences found. */
cbnz diff, .Lnot_limit
/*The second part process*/
ldr data1, [src1], #8
ldr data2, [src2], #8
eor diff, data1, data2 /* Non-zero if differences found. */
subs limit_wd, limit_wd, #1
csinv endloop, diff, xzr, ne/*if limit_wd is 0,will finish the cmp*/
cbz endloop, .Lloopcmp_proc
.Lunequal_proc:
cbz diff, .Lremain8
/* There is difference occurred in the latest comparison. */
.Lnot_limit:
/*
* For little endian,reverse the low significant equal bits into MSB,then
* following CLZ can find how many equal bits exist.
*/
CPU_LE( rev diff, diff )
CPU_LE( rev data1, data1 )
CPU_LE( rev data2, data2 )
/*
* The MS-non-zero bit of DIFF marks either the first bit
* that is different, or the end of the significant data.
* Shifting left now will bring the critical information into the
* top bits.
*/
clz pos, diff
lsl data1, data1, pos
lsl data2, data2, pos
/*
* We need to zero-extend (char is unsigned) the value and then
* perform a signed subtraction.
*/
lsr data1, data1, #56
sub result, data1, data2, lsr #56
.p2align 4
/* Compare up to 8 bytes. Limit is [-8..-1]. */
L(less8):
adds limit, limit, 4
b.lo L(less4)
ldr data1w, [src1], 4
ldr data2w, [src2], 4
cmp data1w, data2w
b.ne L(return)
sub limit, limit, 4
L(less4):
adds limit, limit, 4
beq L(ret_eq)
L(byte_loop):
ldrb data1w, [src1], 1
ldrb data2w, [src2], 1
subs limit, limit, 1
ccmp data1w, data2w, 0, ne /* NZCV = 0b0000. */
b.eq L(byte_loop)
sub result, data1w, data2w
ret
.Lremain8:
/* Limit % 8 == 0 =>. all data are equal.*/
ands limit, limit, #7
b.eq .Lret0
.Ltiny8proc:
ldrb data1w, [src1], #1
ldrb data2w, [src2], #1
subs limit, limit, #1
ccmp data1w, data2w, #0, ne /* NZCV = 0b0000. */
b.eq .Ltiny8proc
sub result, data1, data2
ret
.Lret0:
mov result, #0
ret
SYM_FUNC_END_PI(memcmp)
EXPORT_SYMBOL_NOKASAN(memcmp)
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