Added a performance test for clamped vector load.
Added a performance test for clamped vector load.


Former-commit-id: 3ba0e8342eb199abedee326be62674b977418cc2
Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide