[PATCH] fix i386 memcpy

This patch shortens non-constant memcpy() by two bytes and fixes spurious
out-of-line constant memcpy().

# size vmlinux.org vmlinux
   text    data     bss     dec     hex filename
3954591 1553426  236544 5744561  57a7b1 vmlinux.org
3952615 1553426  236544 5742585  579ff9 vmlinux

Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/include/asm-i386/string.h b/include/asm-i386/string.h
index 1679983..6a78ac5 100644 (file)
--- a/include/asm-i386/string.h
+++ b/include/asm-i386/string.h
@@ -198,47 +198,80 @@ static inline void * __memcpy(void * to, const void * from, size_t n)
 int d0, d1, d2;
 __asm__ __volatile__(
        "rep ; movsl\n\t"
-       "testb $2,%b4\n\t"
-       "je 1f\n\t"
-       "movsw\n"
-       "1:\ttestb $1,%b4\n\t"
-       "je 2f\n\t"
-       "movsb\n"
-       "2:"
+       "movl %4,%%ecx\n\t"
+       "andl $3,%%ecx\n\t"
+#if 1  /* want to pay 2 byte penalty for a chance to skip microcoded rep? */
+       "jz 1f\n\t"
+#endif
+       "rep ; movsb\n\t"
+       "1:"
        : "=&c" (d0), "=&D" (d1), "=&S" (d2)
-       :"0" (n/4), "q" (n),"1" ((long) to),"2" ((long) from)
+       : "0" (n/4), "g" (n), "1" ((long) to), "2" ((long) from)
        : "memory");
 return (to);
 }
 
 /*
- * This looks horribly ugly, but the compiler can optimize it totally,
+ * This looks ugly, but the compiler can optimize it totally,
  * as the count is constant.
  */
 static inline void * __constant_memcpy(void * to, const void * from, size_t n)
 {
-       if (n <= 128)
-               return __builtin_memcpy(to, from, n);
-
-#define COMMON(x) \
-__asm__ __volatile__( \
-       "rep ; movsl" \
-       x \
-       : "=&c" (d0), "=&D" (d1), "=&S" (d2) \
-       : "0" (n/4),"1" ((long) to),"2" ((long) from) \
-       : "memory");
-{
-       int d0, d1, d2;
+       long esi, edi;
+       if (!n) return to;
+#if 1  /* want to do small copies with non-string ops? */
+       switch (n) {
+               case 1: *(char*)to = *(char*)from; return to;
+               case 2: *(short*)to = *(short*)from; return to;
+               case 4: *(int*)to = *(int*)from; return to;
+#if 1  /* including those doable with two moves? */
+               case 3: *(short*)to = *(short*)from;
+                       *((char*)to+2) = *((char*)from+2); return to;
+               case 5: *(int*)to = *(int*)from;
+                       *((char*)to+4) = *((char*)from+4); return to;
+               case 6: *(int*)to = *(int*)from;
+                       *((short*)to+2) = *((short*)from+2); return to;
+               case 8: *(int*)to = *(int*)from;
+                       *((int*)to+1) = *((int*)from+1); return to;
+#endif
+       }
+#endif
+       esi = (long) from;
+       edi = (long) to;
+       if (n >= 5*4) {
+               /* large block: use rep prefix */
+               int ecx;
+               __asm__ __volatile__(
+                       "rep ; movsl"
+                       : "=&c" (ecx), "=&D" (edi), "=&S" (esi)
+                       : "0" (n/4), "1" (edi),"2" (esi)
+                       : "memory"
+               );
+       } else {
+               /* small block: don't clobber ecx + smaller code */
+               if (n >= 4*4) __asm__ __volatile__("movsl"
+                       :"=&D"(edi),"=&S"(esi):"0"(edi),"1"(esi):"memory");
+               if (n >= 3*4) __asm__ __volatile__("movsl"
+                       :"=&D"(edi),"=&S"(esi):"0"(edi),"1"(esi):"memory");
+               if (n >= 2*4) __asm__ __volatile__("movsl"
+                       :"=&D"(edi),"=&S"(esi):"0"(edi),"1"(esi):"memory");
+               if (n >= 1*4) __asm__ __volatile__("movsl"
+                       :"=&D"(edi),"=&S"(esi):"0"(edi),"1"(esi):"memory");
+       }
        switch (n % 4) {
-               case 0: COMMON(""); return to;
-               case 1: COMMON("\n\tmovsb"); return to;
-               case 2: COMMON("\n\tmovsw"); return to;
-               default: COMMON("\n\tmovsw\n\tmovsb"); return to;
+               /* tail */
+               case 0: return to;
+               case 1: __asm__ __volatile__("movsb"
+                       :"=&D"(edi),"=&S"(esi):"0"(edi),"1"(esi):"memory");
+                       return to;
+               case 2: __asm__ __volatile__("movsw"
+                       :"=&D"(edi),"=&S"(esi):"0"(edi),"1"(esi):"memory");
+                       return to;
+               default: __asm__ __volatile__("movsw\n\tmovsb"
+                       :"=&D"(edi),"=&S"(esi):"0"(edi),"1"(esi):"memory");
+                       return to;
        }
 }
-  
-#undef COMMON
-}
 
 #define __HAVE_ARCH_MEMCPY