Loop Counter Register
The only register in this bank is the current loop counter (aL) register. It automatically gets incremented in each execution of the loop - ps/endloop - ps block. So it can be used in the block for relative addressing if needed and is invalid to use it outside the loop.
|Pixel shader versions||1_1||1_2||1_3||1_4||2_0||2_sw||2_x||3_0||3_sw|
|Loop Counter Register||x||x|