Re: [PATCH] Introduce compat_u64 and compat_s64 types

[Arnd Bergmann <arnd@arndb.de>]

On Saturday 16 June 2007, Arnd Bergmann wrote:
> On Saturday 16 June 2007, David Woodhouse wrote:
> > Will GCC know that it needs to emit code to handle that (mis)alignment?
> 
> I've tested this with gcc-4.0.3, and it does the right thing, which
> is to split a 4 byte aligned 64 bit load/store into two 32 bit accesses,
> if you pass -mstrict-align.

I just realized this was correct but slightly misleading. On powerpc, we
don't set the 'attribute((aligned(4)))' on compat_64, so there is never
a reason to handle the misalignment, even though it would work.

On x86_64, misaligned loads are always ok, so gcc never needs to
care about this, even attribute((packed)) does not cause byte access
here.

	Arnd <><