Update prefetch descriptor computation
Update prefetch descriptor computation

ronen/Halide,psuriana/Halide,ronen/Halide,kgnk/Halide,ronen/Halide,kgnk/Halide,kgnk/Halide,kgnk/Halide,kgnk/Halide,kgnk/Halide,psuriana/Halide,psuriana/Halide,ronen/Halide,psuriana/Halide,psuriana/Halide,psuriana/Halide,kgnk/Halide,ronen/Halide,ronen/Halide,ronen/Halide,ronen/Halide,psuriana/Halide,kgnk/Halide