From: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Date: Mon, 23 Mar 2015 10:00:02 -0700
> Maybe the code could be something like
>
> void *memmove(void *dst, const void *src, size_t n);
> {
> // non-overlapping cases
> if (src + n <= dst)
> return memcpy(dst, src, n);
> if (dst + n <= src)
> return memcpy(dst, src, n);
>
> // overlapping, but we know we
> // (a) copy upwards
> // (b) initialize the result in at most chunks of 64
> if (dst+64 <= src)
> return memcpy(dst, src, n);
>
> .. do the backwards thing ..
> }
>
> (ok, maybe I got it wrong, but you get the idea).
>
> I *think* gcc should do ok on the above kind of code, and not generate
> wildly different code from your handcoded version.
Sure you could do that in C, but I really want to avoid using memcpy()
if dst and src overlap in any way at all.
Said another way, I don't want to codify that "64" thing. The next
chip could do 128 byte initializing stores.
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