Re: [PATCH 08/17] alpha: Implement xor_unlock_is_negative_byte

Linus Torvalds
2023-09-16T00:29:00Z

On Fri, 15 Sept 2023 at 11:37, Matthew Wilcox (Oracle)
<willy@infradead.org> wrote:
>
> + "1: ldl_l %0,%4\n"
> + " xor %0,%3,%0\n"
> + " xor %0,%3,%2\n"
> + " stl_c %0,%1\n"

What an odd thing to do.

Why don't you just save the old value? That double xor looks all kinds
of strange, and is a data dependency for no good reason that I can
see.

Why isn't this "ldl_l + mov %0,%2 + xor + stl_c" instead?

Not that I think alpha matters, but since I was looking through the
series, this just made me go "Whaa?"

Linus