[pixel shader]
float4 main() : SV_target
{
    float4 ret = float4(2, 2, 2, 2);
    ret.yxz.yx += float2(0.1, 0.2);
    ret.w.x -= 0.3;
    ret.wzyx.zyx.yx.x *= 0.4;
    return ret;
}

[test]
todo(glsl) draw quad
probe (0, 0) rgba (2.1, 2.2, 0.8, 1.7)