Vectorizing HIRLAM 4: complicated access patterns examined.

[Paul Brook]

> 	When compiling for 64bit, there is an extra cast:
> 	In the 64bit case however, the vectorizer dumps show that the
> 	access-function returned for the index to array b is much more compilcated
> 	- the dataref analyzer doesn't seem to be able to extract the
> 	evolution/step in this case, and concludes that the access is
> 	non-consecutive:
> 	...
>
> Ah yes, this was a well-known issue in the days long before vectorization
> ...
>
> In 1997, Richard Henderson hacked g77 to generate 64-bit array indices
> on 64-bit machines to prevent these casts, which inhibited all sorts
> of run-of-the-mill induction variable analysis ...
>
> This is probably quite invasive.

I thought we'd also fixed this in gfortran. Array indices should be 64-bit 
(aka gfc_array_index_type) on 64-bit targets.

I guess you could also try -fdefault-integer-8, though that might 
break/pessimize other things.

Paul