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

From: Jeremy Fitzhardinge
Date: Thu Feb 15 2007 - 19:14:07 EST


Andrew Morton wrote:
> hm. So if I have
>
> struct bar {
> unsigned long b;
> } __attribute__((packed));
>
> struct foo {
> unsigned long u;
> struct bar b;
> };
>
> then the compiler can see that foo.b.b is well-aligned, regardless of the
> packedness.

In Ralf's code, the structure is anonymous, and is used to declare a
pointer type, which is initialized from a void *. So I think the
compiler isn't allowed to assume anything about its alignment.

J
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