[PATCH 1/8] arm64: Import latest version of Cortex Strings' memcmp
Mark Rutland
mark.rutland at arm.com
Wed May 12 06:28:32 PDT 2021
Hi Robin,
On Tue, May 11, 2021 at 05:12:31PM +0100, Robin Murphy wrote:
> From: Sam Tebbs <sam.tebbs at arm.com>
>
> 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
What's the licensing/copyright situation here?
Because below...
>
> Signed-off-by: Sam Tebbs <sam.tebbs at arm.com>
> [ rm: update attribution and commit message ]
> Signed-off-by: Robin Murphy <robin.murphy at arm.com>
> ---
> arch/arm64/lib/memcmp.S | 330 ++++++++++++++--------------------------
> 1 file changed, 111 insertions(+), 219 deletions(-)
>
> diff --git a/arch/arm64/lib/memcmp.S b/arch/arm64/lib/memcmp.S
> index c0671e793ea9..498f0d9941d9 100644
> --- a/arch/arm64/lib/memcmp.S
> +++ b/arch/arm64/lib/memcmp.S
> @@ -1,247 +1,139 @@
> /* SPDX-License-Identifier: GPL-2.0-only */
... this says 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
> */
... but this referenced file says "SPDX-License-Identifier: MIT", and I
don't know when this relicensing is legitimate.
Thanks,
Mark.
>
> #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
> + subs limit, limit, 8
> + b.lo L(less8)
>
> - /* Not reached the limit, must have found a diff. */
> - tbz limit_wd, #63, .Lnot_limit
> + ldr data1, [src1], 8
> + ldr data2, [src2], 8
> + cmp data1, data2
> + b.ne L(return)
>
> - /* 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
> + subs limit, limit, 8
> + b.gt L(more16)
>
> - orr diff, diff, mask
> - b .Lnot_limit
> + ldr data1, [src1, limit]
> + ldr data2, [src2, limit]
> + b L(return)
>
> -.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. */
> +L(more16):
> + ldr data1, [src1], 8
> + ldr data2, [src2], 8
> + cmp data1, data2
> + bne L(return)
>
> - 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 )
> + /* Jump directly to comparing the last 16 bytes for 32 byte (or less)
> + strings. */
> + subs limit, limit, 16
> + b.ls L(last_bytes)
>
> - orr data1, data1, tmp2
> - orr data2, data2, tmp2
> - b .Lstart_realigned
> + /* 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)
>
> - /*src1 and src2 have different alignment offset.*/
> -.Lmisaligned8:
> - cmp limit, #8
> - b.lo .Ltiny8proc /*limit < 8: compare byte by byte*/
> + /* 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
>
> - 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.*/
> + /* 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)
>
> - 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 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
> +
> + .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.eq .Lstart_align
> -1:
> - sub result, data1, data2
> + 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
>
> -.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)
> EXPORT_SYMBOL_NOKASAN(memcmp)
> --
> 2.21.0.dirty
>
>
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