Re: [PATCH] Optimize generic get_unaligned / put_unaligned implementations.

[Jeremy Fitzhardinge <jeremy@goop.org>]

Ralf Baechle wrote:
> Gcc info page says:
>
> [...]
> `packed'
>      The `packed' attribute specifies that a variable or structure field
>      should have the smallest possible alignment--one byte for a
>      variable, and one bit for a field, unless you specify a larger
>      value with the `aligned' attribute.
> [...]
>
> Qed?

So that the compiler has to assume that if its accessing this __packed
structure, it may be embedded unaligned within something else? And
because the pointer is cast through (void *) it isn't allowed to use
alias analysis to notice that the pointer wasn't originally (apparently)
unaligned.

Seems sound to me.

    J