[Bug tree-optimization/56531] New: SLP load permutations cannot share the load between and inside SLP instances

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56531

             Bug #: 56531
           Summary: SLP load permutations cannot share the load between
                    and inside SLP instances
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Keywords: missed-optimization, wrong-code
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: rguenth@gcc.gnu.org
            Blocks: 56270


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.