MIPS: Drop 32-bit asm string functions

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 <[email protected]>
URL: https://lore.kernel.org/linux-mips/[email protected]/
Cc: Alexander Lobakin <[email protected]>
Reviewed-by: Philippe Mathieu-Daudé <[email protected]>
Cc: [email protected]

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);