[PATCH] riscv:lib: optimize memcmp with ld insn

[Yipeng Zou]

在 2022/8/31 21:16, Conor.Dooley at microchip.com 写道:
> On 31/08/2022 14:07, Yipeng Zou wrote:
>> riscv:lib: optimize memcmp with ld insn
> Minor nit: "riscv: lib:
ok
>> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>>
>> Currently memcmp was implemented in c code(lib/string.c), which compare
>> memory per byte.
>>
>> This patch use ld insn compare memory per word to improve. From the test
>> Results, this will take several times optimized.
> Hey Yipeng,
> Could you share some more information about the tests you did?
> The test results showing the % improvement would be nice :)
> Thanks,
> Conor.

Ofcourse, But My board was not ready, So i just test this patch on qemu 
RV64 & RV32 .

Alloc 8,4,1KB buffer to compare, each loop 10k times.

Size(B)

	

8k

	

4k

	

1k

Min(ns)

	

40800

	

26500

	

15600

Min(ns)

	

16100

	

14200

	

12400

Size(B)

	

8k

	

4k

	

1k

AVG(ns)

	

46316

	

32302

	

17965

AVG(ns)

	

21281

	

16446

	

14316

>> Signed-off-by: Yipeng Zou <zouyipeng at huawei.com>
>> ---
>>    arch/riscv/include/asm/string.h |  3 ++
>>    arch/riscv/lib/Makefile         |  1 +
>>    arch/riscv/lib/memcmp.S         | 59 +++++++++++++++++++++++++++++++++
>>    3 files changed, 63 insertions(+)
>>    create mode 100644 arch/riscv/lib/memcmp.S
>>
>> diff --git a/arch/riscv/include/asm/string.h b/arch/riscv/include/asm/string.h
>> index 909049366555..3337b43d3803 100644
>> --- a/arch/riscv/include/asm/string.h
>> +++ b/arch/riscv/include/asm/string.h
>> @@ -18,6 +18,9 @@ extern asmlinkage void *__memcpy(void *, const void *, size_t);
>>    #define __HAVE_ARCH_MEMMOVE
>>    extern asmlinkage void *memmove(void *, const void *, size_t);
>>    extern asmlinkage void *__memmove(void *, const void *, size_t);
>> +#define __HAVE_ARCH_MEMCMP
>> +extern int memcmp(const void *, const void *, size_t);
>> +
>>    /* For those files which don't want to check by kasan. */
>>    #if defined(CONFIG_KASAN) && !defined(__SANITIZE_ADDRESS__)
>>    #define memcpy(dst, src, len) __memcpy(dst, src, len)
>> diff --git a/arch/riscv/lib/Makefile b/arch/riscv/lib/Makefile
>> index 25d5c9664e57..70773bf0c471 100644
>> --- a/arch/riscv/lib/Makefile
>> +++ b/arch/riscv/lib/Makefile
>> @@ -3,6 +3,7 @@ lib-y                   += delay.o
>>    lib-y                  += memcpy.o
>>    lib-y                  += memset.o
>>    lib-y                  += memmove.o
>> +lib-y                  += memcmp.o
>>    lib-$(CONFIG_MMU)      += uaccess.o
>>    lib-$(CONFIG_64BIT)    += tishift.o
>>
>> diff --git a/arch/riscv/lib/memcmp.S b/arch/riscv/lib/memcmp.S
>> new file mode 100644
>> index 000000000000..83af1c433e6f
>> --- /dev/null
>> +++ b/arch/riscv/lib/memcmp.S
>> @@ -0,0 +1,59 @@
>> +/* SPDX-License-Identifier: GPL-2.0-only */
>> +/*
>> + * Copyright (C) 2022 zouyipeng at huawei.com
>> + */
>> +#include <linux/linkage.h>
>> +#include <asm-generic/export.h>
>> +#include <asm/asm.h>
>> +
>> +/* argrments:
>> +* a0: addr0
>> +* a1: addr1
>> +* a2: size
>> +*/
>> +#define addr0  a0
>> +#define addr1  a1
>> +#define limit  a2
>> +
>> +#define data0  a3
>> +#define data1  a4
>> +#define tmp    t3
>> +#define aaddr  t4
>> +#define return a0
>> +
>> +/* load and compare */
>> +.macro LD_CMP op d0 d1 a0 a1 offset
>> +       \op \d0, 0(\a0)
>> +       \op \d1, 0(\a1)
>> +       addi \a0, \a0, \offset
>> +       addi \a1, \a1, \offset
>> +       sub tmp, \d0, \d1
>> +.endm
>> +
>> +ENTRY(memcmp)
>> +       /* test limit aligend with SZREG */
>> +       andi tmp, limit, SZREG - 1
>> +       /* load tail */
>> +       add aaddr, addr0, limit
>> +       sub aaddr, aaddr, tmp
>> +       add limit, addr0, limit
>> +
>> +.LloopWord:
>> +       sltu tmp, addr0, aaddr
>> +       beqz tmp, .LloopByte
>> +
>> +       LD_CMP REG_L data0 data1 addr0 addr1 SZREG
>> +       beqz tmp, .LloopWord
>> +       j .Lreturn
>> +
>> +.LloopByte:
>> +       sltu tmp, addr0, limit
>> +       beqz tmp, .Lreturn
>> +
>> +       LD_CMP lbu data0 data1 addr0 addr1 1
>> +       beqz tmp, .LloopByte
>> +.Lreturn:
>> +       mv return, tmp
>> +       ret
>> +END(memcmp)
>> +EXPORT_SYMBOL(memcmp);
>> --
>> 2.17.1
>>
-- 
Regards,
Yipeng Zou