* [PATCH] MIPS: Drop 32-bit asm string functions
@ 2019-10-08 19:46 Paul Burton
2019-10-09 12:19 ` Philippe Mathieu-Daudé
2019-10-09 21:58 ` Paul Burton
0 siblings, 2 replies; 3+ messages in thread
From: Paul Burton @ 2019-10-08 19:46 UTC (permalink / raw)
To: linux-mips; +Cc: Paul Burton, Alexander Lobakin
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.
- 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>
---
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);
--
2.23.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] MIPS: Drop 32-bit asm string functions
2019-10-08 19:46 [PATCH] MIPS: Drop 32-bit asm string functions Paul Burton
@ 2019-10-09 12:19 ` Philippe Mathieu-Daudé
2019-10-09 21:58 ` Paul Burton
1 sibling, 0 replies; 3+ messages in thread
From: Philippe Mathieu-Daudé @ 2019-10-09 12:19 UTC (permalink / raw)
To: Paul Burton, linux-mips; +Cc: Paul Burton, Alexander Lobakin
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);
>
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] MIPS: Drop 32-bit asm string functions
2019-10-08 19:46 [PATCH] MIPS: Drop 32-bit asm string functions Paul Burton
2019-10-09 12:19 ` Philippe Mathieu-Daudé
@ 2019-10-09 21:58 ` Paul Burton
1 sibling, 0 replies; 3+ messages in thread
From: Paul Burton @ 2019-10-09 21:58 UTC (permalink / raw)
To: Paul Burton; +Cc: linux-mips, Paul Burton, Alexander Lobakin, linux-mips
Hello,
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.
>
> - 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.
Applied to mips-next.
> commit 3c0be5849259
> https://git.kernel.org/mips/c/3c0be5849259
>
> Signed-off-by: Paul Burton <paul.burton@mips.com>
> URL: https://lore.kernel.org/linux-mips/a2a35f1cf58d6db19eb4af9b4ae21e35@dlink.ru/
> Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Thanks,
Paul
[ This message was auto-generated; if you believe anything is incorrect
then please email paul.burton@mips.com to report it. ]
^ permalink raw reply [flat|nested] 3+ messages in thread
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