Cross-API shader dev is fun you guys!!!!11

gistfile1.txt

        DECLARE_SAMPLER_IBUF(0, int1, zigzag8);
        DECLARE_SAMPLER_IBUF(1, int1, coeff_data);
        DECLARE_SAMPLER_IBUF(2, int1, dc_data);
        #ifdef MOTION
        #ifdef SUB_PLANE
        DECLARE_SAMPLER_U2D(3, i_img); // reference frame
        #else
        DECLARE_SAMPLER_U2D_GATHER(3, i_img); // reference frame
        #endif
        DECLARE_SAMPLER_IBUF(4, ivec2, motion_buf);
        DECLARE_IMAGE_R16I_BUF(1, dc_out_buf);
        #endif

        #define METAL_ARGD \
            METAL_ARG(constant frame_consts& u0) \
            METAL_ARG(device int1 *zigzag8) METAL_ARG(device int1 *coeff_data) METAL_ARG(device short1 *dc_data) \
            METAL_ARG(texture2d<ushort> i_img) METAL_ARG(rwtexture2d_ushort o_img) \
            METAL_ARG(device short2 *motion_buf) METAL_ARG(device short1 *dc_out_buf) \
            METAL_ARG(threadgroup uvec2 *ac_nonzero) METAL_ARG(threadgroup int *coeffs) METAL_ARG(threadgroup uint *dcf_linear)
        #define METAL_ARGS \
            METAL_ARG(u0) \
            METAL_ARG(zigzag8) METAL_ARG(coeff_data) METAL_ARG(dc_data) \
            METAL_ARG(i_img) METAL_ARG(o_img) \
            METAL_ARG(motion_buf) METAL_ARG(dc_out_buf) \
            METAL_ARG(ac_nonzero) METAL_ARG(coeffs) METAL_ARG(dcf_linear)
        
        #ifdef SUB_PLANE
        DECLARE_IMAGE_RG8UI_2D(0, o_img);
        #else
        DECLARE_IMAGE_R8UI_2D(0, o_img);
        #endif

        // ---- Shared utils
        
        int get_dc(uint offs METAL_ARGD)
        {
            return bufferFetch(dc_data, offs).x;
        }
        
        int coeff_data_v(uint offs METAL_ARGD)
        {
            return bufferFetch(coeff_data, offs).x;
        }
        
        // throughout this shader, "ptr" is always an array index in
        // units of 16-bit ints.
        #ifndef METAL_LANG
        int get_int16(uint ptr)
        {
            int val_pair = coeff_data_v(ptr >> 1);
            return bitfieldExtract(val_pair, int(ptr & 1) << 4, 16);
        }
        #else
        int get_int16(uint ptr METAL_ARGD)
        {
            return ((device short *) coeff_data)[ptr];
        }
        #endif