Vectorize the last stage with the appropriate width.
Vectorize the last stage with the appropriate width.


Former-commit-id: 6006f5d64b859e0605de6e4b838b0670e71863cd
darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide