tree-vect-slp.c (vect_get_and_check_slp_defs): For reduction chains try harder with operand swapping and instead of putting a...

2019-10-24  Richard Biener  <rguenther@suse.de>

	* tree-vect-slp.c (vect_get_and_check_slp_defs): For reduction
	chains try harder with operand swapping and instead of
	putting a shifted chain into the reduction operands put
	a repetition of the final reduction op there as if we'd
	reassociate the expression.

	* gcc.dg/vect/slp-reduc-10a.c: New testcase.
	* gcc.dg/vect/slp-reduc-10b.c: Likewise.
	* gcc.dg/vect/slp-reduc-10c.c: Likewise.
	* gcc.dg/vect/slp-reduc-10d.c: Likewise.
	* gcc.dg/vect/slp-reduc-10e.c: Likewise.

From-SVN: r277406