[Bug middle-end/58041] Unaligned access to arrays in packed structure

["jamborm at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58041

Martin Jambor <jamborm at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|wschmidt at gcc dot gnu.org        |jamborm at gcc dot gnu.org

--- Comment #24 from Martin Jambor <jamborm at gcc dot gnu.org> ---
Created attachment 30594
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=30594&action=edit
Proposed patch

(In reply to Bill Schmidt from comment #20)
> After thinking it over some more, I think you are right, Martin.  We should
> go ahead with the optimization with the corrected alignment attached to the
> type.  Please go ahead with your patch.  I will run a round of regression
> testing on PowerPC (an architecture for which the generic test produces
> misaligned but legal memory references) as well.
> 
> Sorry for going back and forth on this.  I try to avoid wasting compile time
> on useless transformations, but in this case we will still see some benefit
> in some cases, and the code should be no worse than before when we don't.
> 

No worries, I'm currently bootstrapping and testing the attached
patch.  I'm bootstrapping on x86_64-linux and with bugs like this one,
any additional testing on other platforms is very welcome.

(In reply to Bill Schmidt from comment #21)
> My only comment on the patch would be to please add commentary indicating
> why the change is being made, and referencing this PR.  Something along the
> lines of:
> 
>   /* Ensure the memory reference carries the minimum alignment
>      requirement for the data type.  Some targets (e.g., ARM)
>      can't always handle an unaligned reference otherwise.  See PR58041.  */
> 
> ...or something like that.
> 

The alignment information should be there regardless of the target so
I just used the first sentence and the PR reference.  I hope that is
enough.  Thanks.