re PR tree-optimization/76490 (when use -O2 -fcheck-founds compiler appears to hang and consumes all memory)

2016-08-17  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/76490
	* tree-vrp.c (update_value_range): Preserve overflow infinities
	when intersecting with ranges from get_range_info.
	(operand_less_p): Handle overflow infinities correctly.
	(value_range_constant_singleton): Use vrp_operand_equal_p
	to handle overflow max/min correctly.
	(vrp_valueize): Likewise.
	(union_ranges): Likewise.
	(intersect_ranges): Likewise.
	(vrp_visit_phi_node): Improve iteration limitation to only
	apply when we'll possibly re-visit the PHI via a changed argument
	on the backedge.

	* gfortran.fortran-torture/compile/pr76490.f90: New testcase.
	* gcc.dg/pr52904.c: XFAIL.

From-SVN: r239529