[lno] vectorizer patch: minor fixes

[Dorit Naishlos <DORIT at il dot ibm dot com>]

The following patch to the vectorizer includes:
- Support vectorization of assignment stmts
- A check to make sure that defs in the loop are not used outside the loop,
until proper support is added.
- A fix, following http://gcc.gnu.org/ml/gcc-bugs/2004-02/msg01138.html.
- A fix, following a comment from Falk Hueffner suggesting to replace
unsigned_intSI_type_node with size_type_node in the creation of variables
within the vectorizer.

dorit

        * tree-vectorizer.h (assignment_vec_info_type): New enum value for
        stmt_vec_info_type.
        * tree-vectorizer.c (vect_transform_assignment): New function.
        Support vectorization of assignment stmts.
        (vect_transform_stmt): Call vect_transform_assignment.
        (vect_is_supportable_assignment): New function.
        (vect_analyze_operations): Call vect_is_supportable_assignment.

        (vect_create_index_for_array_ref): Replace unsigned_intSI_type_node
        with size_type_node.
        (vect_transform_loop_bound): Likewise.

        (get_vectype_for_scalar_type): Avoid division by 0.

        (vect_analyze_operations): Apply check for no-uses-out-of-loop also
        to stmts that are marked irrelevant.


(See attached file: vect_patch_Feb25)

Attachment: vect_patch_Feb25
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