From: "Philippe Mathieu-Daudé" <f4bug@amsat.org>
To: Paul Burton <paul.burton@mips.com>,
"linux-mips@vger.kernel.org" <linux-mips@vger.kernel.org>
Cc: Paul Burton <pburton@wavecomp.com>,
Alexander Lobakin <alobakin@dlink.ru>
Subject: Re: [PATCH] MIPS: Drop 32-bit asm string functions
Date: Wed, 9 Oct 2019 14:19:48 +0200 [thread overview]
Message-ID: <0a625df3-dff6-0dcc-d0bd-63845d450ca3@amsat.org> (raw)
In-Reply-To: <20191008194552.2176475-1-paul.burton@mips.com>
On 10/8/19 9:46 PM, Paul Burton wrote:
> We have assembly implementations of strcpy(), strncpy(), strcmp() &
> strncmp() which:
>
> - Are simple byte-at-a-time loops with no particular optimizations. As
> a comment in the code describes, they're "rather naive".
>
> - Offer no clear performance advantage over the generic C
> implementations - in microbenchmarks performed by Alexander Lobakin
> the asm functions sometimes win & sometimes lose, but generally not
> by large margins in either direction.
Maybe add: "See URL below for full benchmark results."
>
> - Don't support 64-bit kernels, where we already make use of the
> generic C implementations.
>
> - Tend to bloat kernel code size due to inlining.
>
> - Don't support CONFIG_FORTIFY_SOURCE.
>
> - Won't support nanoMIPS without rework.
>
> For all of these reasons, delete the asm implementations & make use of
> the generic C implementations for 32-bit kernels just like we already do
> for 64-bit kernels.
>
> Signed-off-by: Paul Burton <paul.burton@mips.com>
> URL: https://lore.kernel.org/linux-mips/a2a35f1cf58d6db19eb4af9b4ae21e35@dlink.ru/
> Cc: Alexander Lobakin <alobakin@dlink.ru>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> ---
>
> arch/mips/include/asm/string.h | 123 ---------------------------------
> 1 file changed, 123 deletions(-)
>
> diff --git a/arch/mips/include/asm/string.h b/arch/mips/include/asm/string.h
> index 4b938c55b397..1de3bbce8e88 100644
> --- a/arch/mips/include/asm/string.h
> +++ b/arch/mips/include/asm/string.h
> @@ -10,129 +10,6 @@
> #ifndef _ASM_STRING_H
> #define _ASM_STRING_H
>
> -#if !defined(__OPTIMIZE__) || !defined(CONFIG_FORTIFY_SOURCE)
> -
> -/*
> - * Most of the inline functions are rather naive implementations so I just
> - * didn't bother updating them for 64-bit ...
> - */
> -#ifdef CONFIG_32BIT
> -
> -#ifndef IN_STRING_C
> -
> -#define __HAVE_ARCH_STRCPY
> -static __inline__ char *strcpy(char *__dest, __const__ char *__src)
> -{
> - char *__xdest = __dest;
> -
> - __asm__ __volatile__(
> - ".set\tnoreorder\n\t"
> - ".set\tnoat\n"
> - "1:\tlbu\t$1,(%1)\n\t"
> - "addiu\t%1,1\n\t"
> - "sb\t$1,(%0)\n\t"
> - "bnez\t$1,1b\n\t"
> - "addiu\t%0,1\n\t"
> - ".set\tat\n\t"
> - ".set\treorder"
> - : "=r" (__dest), "=r" (__src)
> - : "0" (__dest), "1" (__src)
> - : "memory");
> -
> - return __xdest;
> -}
> -
> -#define __HAVE_ARCH_STRNCPY
> -static __inline__ char *strncpy(char *__dest, __const__ char *__src, size_t __n)
> -{
> - char *__xdest = __dest;
> -
> - if (__n == 0)
> - return __xdest;
> -
> - __asm__ __volatile__(
> - ".set\tnoreorder\n\t"
> - ".set\tnoat\n"
> - "1:\tlbu\t$1,(%1)\n\t"
> - "subu\t%2,1\n\t"
> - "sb\t$1,(%0)\n\t"
> - "beqz\t$1,2f\n\t"
> - "addiu\t%0,1\n\t"
> - "bnez\t%2,1b\n\t"
> - "addiu\t%1,1\n"
> - "2:\n\t"
> - ".set\tat\n\t"
> - ".set\treorder"
> - : "=r" (__dest), "=r" (__src), "=r" (__n)
> - : "0" (__dest), "1" (__src), "2" (__n)
> - : "memory");
> -
> - return __xdest;
> -}
> -
> -#define __HAVE_ARCH_STRCMP
> -static __inline__ int strcmp(__const__ char *__cs, __const__ char *__ct)
> -{
> - int __res;
> -
> - __asm__ __volatile__(
> - ".set\tnoreorder\n\t"
> - ".set\tnoat\n\t"
> - "lbu\t%2,(%0)\n"
> - "1:\tlbu\t$1,(%1)\n\t"
> - "addiu\t%0,1\n\t"
> - "bne\t$1,%2,2f\n\t"
> - "addiu\t%1,1\n\t"
> - "bnez\t%2,1b\n\t"
> - "lbu\t%2,(%0)\n\t"
> -#if defined(CONFIG_CPU_R3000)
> - "nop\n\t"
> -#endif
> - "move\t%2,$1\n"
> - "2:\tsubu\t%2,$1\n"
> - "3:\t.set\tat\n\t"
> - ".set\treorder"
> - : "=r" (__cs), "=r" (__ct), "=r" (__res)
> - : "0" (__cs), "1" (__ct));
> -
> - return __res;
> -}
> -
> -#endif /* !defined(IN_STRING_C) */
> -
> -#define __HAVE_ARCH_STRNCMP
> -static __inline__ int
> -strncmp(__const__ char *__cs, __const__ char *__ct, size_t __count)
> -{
> - int __res;
> -
> - __asm__ __volatile__(
> - ".set\tnoreorder\n\t"
> - ".set\tnoat\n"
> - "1:\tlbu\t%3,(%0)\n\t"
> - "beqz\t%2,2f\n\t"
> - "lbu\t$1,(%1)\n\t"
> - "subu\t%2,1\n\t"
> - "bne\t$1,%3,3f\n\t"
> - "addiu\t%0,1\n\t"
> - "bnez\t%3,1b\n\t"
> - "addiu\t%1,1\n"
> - "2:\n\t"
> -#if defined(CONFIG_CPU_R3000)
> - "nop\n\t"
> -#endif
> - "move\t%3,$1\n"
> - "3:\tsubu\t%3,$1\n\t"
> - ".set\tat\n\t"
> - ".set\treorder"
> - : "=r" (__cs), "=r" (__ct), "=r" (__count), "=r" (__res)
> - : "0" (__cs), "1" (__ct), "2" (__count));
> -
> - return __res;
> -}
> -#endif /* CONFIG_32BIT */
> -#endif /* !defined(__OPTIMIZE__) || !defined(CONFIG_FORTIFY_SOURCE) */
> -
> #define __HAVE_ARCH_MEMSET
> extern void *memset(void *__s, int __c, size_t __count);
>
>
next prev parent reply other threads:[~2019-10-09 12:19 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-08 19:46 [PATCH] MIPS: Drop 32-bit asm string functions Paul Burton
2019-10-09 12:19 ` Philippe Mathieu-Daudé [this message]
2019-10-09 21:58 ` Paul Burton
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