Refactored vectorize to remove common expand code
Refactored vectorize to remove common expand code

Former-commit-id: 44ddbd6db1cbe2e6452c68cc22954b79ae056c63
Trass3r/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide