In this paper, the authors propose an adaptive extensible processor in which custom instructions are generated and added after chip-fabrication. A reconfigurable functional unit is utilized to support this feature. The proposed reconfigurable functional unit is based on a matrix of functional units which is multi-cycle with the capability of conditional execution. A quantitative approach is utilized to fix the constraints of the architecture. Unlike previously proposed custom instructions, their include multiple exits. Conditional execution has been added to support the multi-exit feature of custom instructions.