tree-vrp.c (infer_value_range): Only count pointer uses and dereferences if -fdelete...

tree-vrp.c (infer_value_range): Only count pointer uses and dereferences if -fdelete-null-pointer-checks is enabled.

	* tree-vrp.c (infer_value_range): Only count pointer uses
	and dereferences if -fdelete-null-pointer-checks is enabled.

	* tree-vrp.c (find_assert_locations): Infer value ranges for
	single use pointers, but do not create ASSERT_EXPRs for them.
	When a non-null range is inferred for a pointer, backwards
	propagate that range to other equivalent pointers through the
	use-def chain.

	* gcc.dg/tree-ssa/20030730-1.c: No longer expected to fail.
	* gcc.dg/tree-ssa/20030730-2.c: No longer expected to fail.
	* g++.dg/tree-ssa/pr26406.C: New test.

From-SVN: r111848