<li>vec4 - force vec4 mode in vertex shader</li>
<li>spill_fs - force spilling of all registers in the scalar backend (useful to debug spilling code)</li>
<li>spill_vec4 - force spilling of all registers in the vec4 backend (useful to debug spilling code)</li>
+ <li>norbc - disable single sampled render buffer compression</li>
</ul>
</ul>