tree-optimization/105053 - fix reduction chain epilogue generation

tree-optimization/105053 - fix reduction chain epilogue generation

When we optimize permutations in a reduction chain we have to
be careful to select the correct live-out stmt, otherwise the
reduction result will be unused and the retained scalar code will
execute only the number of vector iterations.

2022-03-25  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/105053
	* tree-vect-loop.c (vect_create_epilog_for_reduction): Pick
	the correct live-out stmt for a reduction chain.

	* g++.dg/vect/pr105053.cc: New testcase.