autovectorization and aligned access

[Tim Prince]

ranjith kumar wrote:
> Hi,
>
>      Can anyone explain why gcc wont do
> autovectorization if the program contains un aligned
> acceses?
> There are instructions to acceses unaligned acceses.
> Instead of exploiting them why gcc produces scalar code??
>   
Vectorization is unlikely to be efficient, unless the loop can be 
adjusted so that all stores are aligned.  Unaligned loads generally 
aren't as efficient as scalar loads, so you will see scalar loads even 
in vectorized code.  Future CPUs are advertised as having more efficient 
support for un-aligned data, but gcc is rightly based on current 
production models.