When materializing on a VEC_PERM node we have to permute the
incoming vectors, not the outgoing one.
2021-01-05 Richard Biener <rguenther@suse.de>
PR tree-optimization/98516
* tree-vect-slp.c (vect_optimize_slp): Permute the incoming
lanes when materializing on a VEC_PERM node.
(vectorizable_slp_permutation): Dump the permute properly.
* gcc.dg/vect/bb-slp-pr98516-1.c: New testcase.
* gcc.dg/vect/bb-slp-pr98516-2.c: Likewise.