1. A processor comprising: storage memory to store an instruction stream that corresponds to a single program executable, the instruction stream comprising coded control instructions and other coded instructions, at least some of the other coded instructions having different instruction set architectures, each of at least some of the coded control instructions comprising control information that defines a rule for use in decoding a corresponding other coded instruction that is located in a subsequent part of the instruction stream; and a single instruction-decoder comprising a static-decode part and an instruction-decode part, the static-decode part to decode a coded control instruction in the instruction stream to obtain control information from the coded control instruction, the control information being usable by the instruction-decode part to decode a corresponding other coded instruction in the instruction stream.