re PR tree-optimization/32573 (ice for legal code with -O3)

re PR tree-optimization/32573 (ice for legal code with -O3)

	PR tree-optimization/32573
	PR middle-end/32946
	* tree-data-ref.c (initialize_data_dependence_relation): Clear
	DDR_SUBSCRIPTS, DDR_DIR_VECTS and DDR_DIST_VECTS at the beginning.
	(finalize_ddr_dependent): Clear DDR_SUBSCRIPTS after freeing it.
	(build_classic_dist_vector): Return false rather than true if
	DDR_ARE_DEPENDENT is non-NULL at the beginning.  Return false
	if either subscript_dependence_tester_1 or build_classic_dist_vector_1
	returned false.  Don't call save_dist_v before calling
	build_classic_dist_vector_1.
	(free_dependence_relation): Don't guard freeing DDR_SUBSCRIPTS
	with NULL DDR_ARE_DEPENDENT.  Also free DDR_DIST_VECTS and/or
	DDR_DIR_VECTS vectors.

	* gcc.dg/pr32573.c: New test.

From-SVN: r127750