[U-Boot] [PATCH 1/3] memcpy: use 32-bit copies if possible

[Peter Tyser]

Hi Alessandro,

> --- a/lib_generic/string.c
> +++ b/lib_generic/string.c
> @@ -449,7 +449,16 @@ char * bcopy(const char * src, char * dest, int count)
>  void * memcpy(void * dest,const void *src,size_t count)
>  {
>  	char *tmp = (char *) dest, *s = (char *) src;
> +	u32 *d32 = (u32 *)dest, *s32 = (u32 *) src;
>  
> +	/* if both are aligned, use 32-bit copy */
> +	if ( (((int)dest & 3) | ((int)src & 3) | (count & 3)) == 0 ) {
> +		count /= 4;
> +		while (count--)
> +			*d32++ = *s32++;
> +		return dest;
> +	}
> +	/* else, use 1-byte copy */
>  	while (count--)
>  		*tmp++ = *s++;

If we're adding this logic, what about adding it such that:

if (src/dest are 32-bit aligned and count > 3) {
	perform 32-bit copies till count <= 3
}
perform remaining 8-bit copies till count == 0

You'd still get the performance boost but not have the requirement that
count is evenly divisible by 4.  You could do byte copies before the
32-bit copies to align the src/dest in some cases, but that might be
overkill...

Same comment goes for the memset implementation.

Best,
Peter