label - vs
Mark the next instruction as having a label index.
where # identifies the label number.
For vs_2_0, and vs_2_x, the label number must be between between 0 and 15.
For vs_2_sw, vs_3_0 and vs_3_sw, the label number must be between between 0 and 2047.
|Vertex shader versions||1_1||2_0||2_x||2_sw||3_0||3_sw|
This instruction defines a label located at the next shader instruction. The label instruction can only be present directly after a ret instruction (which defines the end of the previous subroutine or main program).