Re: s390{,x} ABI incompatibility between gcc 4.0 and 4.1

[Joern RENNECKE <joern dot rennecke at st dot com>]

Jakub Jelinek wrote:

>  
>
>
> If we use MIN (tree_low_cst (TYPE_SIZE (type), 0), BIGGEST_ALIGNMENT)
> here, I'm afraid that would be much bigger ABI incompatibility.
> Currently, say
> typedef char __attribute__((vector_size (64))) v64qi;
> is 64 bytes aligned on most arches, even when BIGGEST_ALIGNMENT is much
> smaller.
> GCC 4.0.x on s390{,x} aligned vector_size 1/2/4/8/64/128/... types
> to their size, just vector_size 16 and 32 has been 8 bytes aligned
> (BIGGEST_ALIGNMENT).
>  
That sounds very strange.  Is there a rationale for that, or is this a 
SNAFU?

> Not capping to BIGGEST_ALIGNMENT might have issues with some object formats
> though, if they don't support ridiculously big aligments.
>  
We have MAX_OFILE_ALIGNMENT for that.