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arm64: Import latest version of Cortex Strings' memcmp

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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: Sam Tebbs <sam.tebbs@arm.com>
[ rm: update attribution and commit message ]
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/2889de2d41054f3f508fb3addad784a3606ef383.1622128527.git.robin.murphy@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Sam Tebbs 2021-05-27 16:34:41 +01:00 committed by Will Deacon
parent c4681547bc
commit 43de30d367
1 changed files with 111 additions and 219 deletions
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330
arch/arm64/lib/memcmp.S
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@ -1,247 +1,139 @@
/* SPDX-License-Identifier: GPL-2.0-only */ /* SPDX-License-Identifier: GPL-2.0-only */
/* /*
* Copyright (C) 2013 ARM Ltd. * Copyright (c) 2013-2020, Arm Limited.
* Copyright (C) 2013 Linaro.
* *
* This code is based on glibc cortex strings work originally authored by Linaro * Adapted from the original at:
* be found @ * https://github.com/ARM-software/optimized-routines/blob/master/string/aarch64/memcmp.S
*
* http://bazaar.launchpad.net/~linaro-toolchain-dev/cortex-strings/trunk/
* files/head:/src/aarch64/
*/ */
#include <linux/linkage.h> #include <linux/linkage.h>
#include <asm/assembler.h> #include <asm/assembler.h>
/* /* Assumptions:
* compare memory areas(when two memory areas' offset are different, *
* alignment handled by the hardware) * ARMv8-a, AArch64, unaligned accesses.
* */
* Parameters:
* x0 - const memory area 1 pointer #define L(label) .L ## label
* 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
*/
/* Parameters and result. */ /* Parameters and result. */
src1 .req x0 #define src1 x0
src2 .req x1 #define src2 x1
limit .req x2 #define limit x2
result .req x0 #define result w0
/* Internal variables. */ /* Internal variables. */
data1 .req x3 #define data1 x3
data1w .req w3 #define data1w w3
data2 .req x4 #define data1h x4
data2w .req w4 #define data2 x5
has_nul .req x5 #define data2w w5
diff .req x6 #define data2h x6
endloop .req x7 #define tmp1 x7
tmp1 .req x8 #define tmp2 x8
tmp2 .req x9
tmp3 .req x10
pos .req x11
limit_wd .req x12
mask .req x13
SYM_FUNC_START_WEAK_PI(memcmp) SYM_FUNC_START_WEAK_PI(memcmp)
cbz limit, .Lret0 subs limit, limit, 8
eor tmp1, src1, src2 b.lo L(less8)
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. */ ldr data1, [src1], 8
tbz limit_wd, #63, .Lnot_limit ldr data2, [src2], 8
cmp data1, data2
b.ne L(return)
/* Limit % 8 == 0 => the diff is in the last 8 bytes. */ subs limit, limit, 8
ands limit, limit, #7 b.gt L(more16)
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 ldr data1, [src1, limit]
b .Lnot_limit ldr data2, [src2, limit]
b L(return)
.Lmutual_align: L(more16):
/* ldr data1, [src1], 8
* Sources are mutually aligned, but are not currently at an ldr data2, [src2], 8
* alignment boundary. Round down the addresses and then mask off cmp data1, data2
* the bytes that precede the start point. bne L(return)
*/
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.*/ /* Jump directly to comparing the last 16 bytes for 32 byte (or less)
neg tmp1, tmp1/* Bits to alignment -64. */ strings. */
mov tmp2, #~0 subs limit, limit, 16
/*mask off the non-intended bytes before the start address.*/ b.ls L(last_bytes)
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 /* We overlap loads between 0-32 bytes at either side of SRC1 when we
orr data2, data2, tmp2 try to align, so limit it only to strings larger than 128 bytes. */
b .Lstart_realigned cmp limit, 96
b.ls L(loop16)
/*src1 and src2 have different alignment offset.*/ /* Align src1 and adjust src2 with bytes not yet done. */
.Lmisaligned8: and tmp1, src1, 15
cmp limit, #8 add limit, limit, tmp1
b.lo .Ltiny8proc /*limit < 8: compare byte by byte*/ sub src1, src1, tmp1
sub src2, src2, tmp1
and tmp1, src1, #7 /* Loop performing 16 bytes per iteration using aligned src1.
neg tmp1, tmp1 Limit is pre-decremented by 16 and must be larger than zero.
add tmp1, tmp1, #8/*valid length in the first 8 bytes of src1*/ Exit if <= 16 bytes left to do or if the data is not equal. */
and tmp2, src2, #7 .p2align 4
neg tmp2, tmp2 L(loop16):
add tmp2, tmp2, #8/*valid length in the first 8 bytes of src2*/ ldp data1, data1h, [src1], 16
subs tmp3, tmp1, tmp2 ldp data2, data2h, [src2], 16
csel pos, tmp1, tmp2, hi /*Choose the maximum.*/ subs limit, limit, 16
ccmp data1, data2, 0, hi
ccmp data1h, data2h, 0, eq
b.eq L(loop16)
sub limit, limit, pos cmp data1, data2
/*compare the proceeding bytes in the first 8 byte segment.*/ bne L(return)
.Ltinycmp: mov data1, data1h
ldrb data1w, [src1], #1 mov data2, data2h
ldrb data2w, [src2], #1 cmp data1, data2
subs pos, pos, #1 bne L(return)
ccmp data1w, data2w, #0, ne /* NZCV = 0b0000. */
b.eq .Ltinycmp /* Compare last 1-16 bytes using unaligned access. */
cbnz pos, 1f /*diff occurred before the last byte.*/ 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
.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 cmp data1w, data2w
b.eq .Lstart_align b.ne L(return)
1: sub limit, limit, 4
sub result, data1, data2 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 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
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) SYM_FUNC_END_PI(memcmp)
EXPORT_SYMBOL_NOKASAN(memcmp) EXPORT_SYMBOL_NOKASAN(memcmp)