re PR tree-optimization/88427 (ICE: tree check: expected integer_cst, have plus_expr in get_len, at tree.h:5617)

2018-12-10  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/88427
	* vr-values.c (vr_values::extract_range_from_phi_node):
	Handle symbolic ranges conservatively when trying to drop
	to Inf +- 1.

	* gcc.dg/pr88427.c: New testcase.

From-SVN: r266955