re PR tree-optimization/85478 (ICE with single element vector)

Fix PR85478

gcc/ChangeLog:

2018-04-24  Andreas Krebbel  <krebbel@linux.ibm.com>

	PR tree-optimization/85478
	* tree-vect-loop.c (vect_analyze_loop_2): Do not call
	vect_grouped_store_supported for single element vectors.

gcc/testsuite/ChangeLog:

2018-04-24  Andreas Krebbel  <krebbel@linux.ibm.com>

	PR tree-optimization/85478
	* g++.dg/pr85478.C: New test.

From-SVN: r259593