Use target-features to etablish hvx single/double modes
Use target-features to etablish hvx single/double modes


Former-commit-id: bb10931ba291f45f65d27fb08e712f9c4470f659
Trass3r/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide