common.opt: Add option ftree-vect-loop-version.

common.opt: Add option ftree-vect-loop-version.

        * common.opt: Add option ftree-vect-loop-version.
        * params.def: Add --param vect-max-version-checks.
        * doc/invoke.texi: Document ftree-vect-loop-version and
        --param vect-max-version-checks.
        * tree-vectorizer.h (_loop_vec_info): Add ptr_mask and
        may_misalign_stmts and defines for accessors.
        * tree-vectorizer.c : (new_loop_vec_info): VEC_alloc for
        LOOP_VINFO_MAY_MISALIGN_STMTS.
        (destroy_loop_vec_info): VEC_free for
        LOOP_VINFO_MAY_MISALIGN_STMTS.
        * tree-vect-analyze.c (vect_compute_data_ref_alignment):
        Update documentation.
        (vect_update_misalignment_for_peel): New.
        (vect_enhance_data_refs_alignment): Update to choose loop
        peeling or loop versioning if appropriate for the (potentially)
        unaligned data references in the loop.
        (vect_analyze_data_refs_alignment): Remove call to
        vect_enhance_data_refs_alignment so the checks can be done
        earlier.
        (vect_analyze_loop): Add call to vect_enhance_data_refs_alignment
        and move up call to vect_analyze_data_refs_alignment.
        * tree-vect-transform.c (vect_create_cond_for_align_checks): New.
        (vect_transform_loop): Add call to loop_version.

From-SVN: r103941