re PR tree-optimization/66949 (ICE at -O2 and -O3 on x86_64-linux-gnu in tree_ssa_phi...

re PR tree-optimization/66949 (ICE at -O2 and -O3 on x86_64-linux-gnu in tree_ssa_phiopt_worker, at tree-ssa-phiopt.c:335)

	PR tree-optimization/66949
	* tree-ssa-phiopt.c (tree_ssa_phiopt_worker): Don't call
	single_non_singleton_phi_for_edges to get the PHI from
	factor_out_conditional_conversion.  Use NULL_TREE instead of NULL.
	(factor_out_conditional_conversion): Adjust declaration.  Make it
	return the newly-created PHI.

	* gcc.dg/torture/pr66949-1.c: New test.
	* gcc.dg/torture/pr66949-2.c: New test.

From-SVN: r231457