SLP load permutations are currently severely restricted (only 000..111... is
supported) and they do not share the load (ICE before the fix for PR56270).
This is because vinfo->vectorized_stmt of the underlying group load includes
the very first permutation of the very first SLP instance.
The fix here is to make vinfo->vectorized_stmt the group load itself and
hook in the permutation only on the consumer.