re PR tree-optimization/68240 (compilation hangs on valid code at -O1 and above on x86_64-linux-gnu)

2015-11-10  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/68240
	* tree-ssa-sccvn.c (cond_stmts_equal_p): Handle commutative compares
	properly.
	(visit_phi): For PHIs with just a single executable edge
	take its value directly.
	(expressions_equal_p): Handle VN_TOP properly.

	* gcc.dg/torture/pr68240.c: New testcase.

From-SVN: r230095