re PR target/81504 (gcc-7 regression: vec_st in loop misoptimized)

re PR target/81504 (gcc-7 regression: vec_st  in loop misoptimized)

2017-08-25  Bill Schmidt  <wschmidt@linux.vnet.ibm.com>

	PR target/81504
	* config/rs6000/rs6000-p8swap.c (find_alignment_op): Add reference
	parameter and_insn and return it.
	(recombine_lvx_pattern): Insert a copy to ensure availability of
	the base register of the copied masking operation at the point of
	the instruction replacement.
	(recombine_stvx_pattern): Likewise.

From-SVN: r251355