PR82289: Computing peeling costs for irrelevant drs

PR82289: Computing peeling costs for irrelevant drs

This PR shows that we weren't filtering out irrelevant stmts in
vect_get_peeling_costs_all_drs (unlike related loops in which
we iterate over all datarefs).

2017-09-22  Richard Sandiford  <richard.sandiford@linaro.org>

gcc/
	PR tree-optimization/82289
	* tree-vect-data-refs.c (vect_get_peeling_costs_all_drs): Check
	STMT_VINFO_RELEVANT_P.

gcc/testsuite/
	PR tree-optimization/82289
	* gcc.dg/vect/pr82289.c: New test.

From-SVN: r253103