* gcc.c-torture/execute/pr58387.c: New test.

	* tree-ssa-dom.c (cprop_into_successor_phis): Also propagate
	edge implied equivalences into successor phis.
	* tree-ssa-threadupdate.c (phi_args_equal_on_edges): Moved into
	here from tree-ssa-threadedge.c.
	(mark_threaded_blocks): When threading through a joiner, if both
	successors of the joiner's clone reach the same block, verify the
	PHI arguments are equal.  If not, cancel the jump threading request.
	* tree-ssa-threadedge.c (phi_args_equal_on_edges): Moved into
	tree-ssa-threadupdate.c
	(thread_across_edge): Don't check PHI argument equality when
	threading through joiner block here.

From-SVN: r202660