Work around clang's lack of support for ternary operator on vectors.
Work around clang's lack of support for ternary operator on vectors.


Former-commit-id: 7abd470e990167425ddbb30ae350eb39b25858ee
darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide