Eliminate unvarying comparison warnings for unsigned values being tested for less than zero.
Eliminate unvarying comparison warnings for unsigned values being tested
for less than zero.


Former-commit-id: 5e67448f670dee04ab5c5e6132076a936d3c317e
darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,darkbuck/Halide,Trass3r/Halide