atomic accesses

[David Daney]

Segher Boessenkool wrote:
> The Linux kernel, and probably some user-space applications and libraries
> as well, depend on GCC guaranteeing (a variant of) the following:
> 
>     "any access to a naturally aligned scalar object in memory
>     that is not a bit-field will be performed by a single machine
>     instruction whenever possible"
> 
> and it seems the current compiler actually does work like this.
> 
> I propose we add this text to the GCC manual (where?), so at least they
> are right if/when they blame us for breaking that promise :-)
> 
> Comments?  Flames?
> 

It seems like a good idea.

This seems somewhat like other issues we have dealt with concerning 
thread safety.  Perhaps an entire section addressing code generation 
issues related to correct multi-threaded semantics.

David Daney