[Bug target/38496] Gcc misaligns arrays when stack is forced follow the x8632 ABI

[pinskia at gmail dot com]

------- Comment #16 from pinskia at gmail dot com  2008-12-15 21:39 -------
Subject: Re:  Gcc misaligns arrays when stack is forced follow the x8632 ABI



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On Dec 15, 2008, at 1:33 PM, "whaley at cs dot utsa dot edu"
<gcc-bugzilla@gcc.gnu.org 
 > wrote:

>
>
> ------- Comment #15 from whaley at cs dot utsa dot edu  2008-12-15  
> 21:32 -------
>> GCC chose to change the *unwritten* standard for the ABI in use for  
>> IA32 GNU/Linux.
>
> This is not true.  Prior to this change, gcc followed the *written*  
> standard
> provided by the LSB.

LSB was written years after we had already did this back in gcc 3.0.  
Please check the history before saying gcc followed a written standard  
when none existed when this change was done.

> You chose to violate the standard, or to put as you seem
> to prefer, you chose to declare that you followed no standard, as  
> the written
> standard previously used by pretty much all OSes on the x86 was  
> suddenly
> unusable.
>
>> The SCO document may have been useful before SSE, but processor  
>> architecture and language developments have made it problematic for  
>> many years.
>
> This is not even trivially true.  SSE requires no change in the ABI  
> to support:
> it is purely convenience to start with a known 16-byte alignment: an  
> andb and a
> register save/restore fixes the problem completely, without  
> abandoning the
> standard.  I believe gcc still abides by this "problematic for many  
> years"
> standard in all respects except stack alignment, which is a trivial  
> problem to
> solve and still abide by the standard.  So, you abandoned standard  
> compliance
> to solve a minor irritant, that you yourself have fixed in the new  
> 4.4 series.
> From 4.4 on, you broke the standard for no gain at all, since you  
> have now
> added the minor complexity of manually aligning the stack anyway.
>
> Of course the standard seems outdated to us: it is supporting an  
> architecture
> that is decades old, and that is the strength of it.  If you want  
> the shiny new
> stuff, you go to x86-64.
>
>
> -- 
>
>
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38496
>


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38496