[v4] avoid alignment of static variables affecting stack's

[Jan Beulich]

>>> On 14.12.15 at 09:35, <richard.guenther@gmail.com> wrote:
> On Fri, Dec 11, 2015 at 2:54 PM, Bernd Schmidt <bschmidt@redhat.com> wrote:
>> On 12/11/2015 02:48 PM, Jan Beulich wrote:
>>>
>>> Function (or more narrow) scope static variables (as well as others not
>>> placed on the stack) should also not have any effect on the stack
>>> alignment. I noticed the issue first with Linux'es dynamic_pr_debug()
>>> construct using an 8-byte aligned sub-file-scope local variable.
>>>
>>> According to my checking bad behavior started with 4.6.x (4.5.3 was
>>> still okay), but generated code got quite a bit worse as of 4.9.0.
>>>
>>> [v4: Bail early, using is_global_var(), as requested by Bernd.]
>>
>>
>> In case I haven't made it obvious, this is OK.
> 
> But I wonder if it makes sense because shortly after the early-out we check
> 
>       if (TREE_STATIC (var)
>           || DECL_EXTERNAL (var)
>           || (TREE_CODE (origvar) == SSA_NAME && use_register_for_decl (var)))
> 
> so either there are obvious cleanup opportunities left or the patch is 
> broken.

Looks like a cleanup opportunity I overlooked when following
Bernd's advice.

Jan