* RLA, RRA, RLCA, RRCA are essentially optimized versions, one byte smaller and one M-cycle faster, of RL A, RR A, RLC A, RRC A.
* ADD A,A is one byte smaller and one M-cycle faster than SLA A.* Similarly, ADD HL,HL is 3 bytes smaller and one M-cycle faster than SLA L; RL H.
* DJNZ loop is one byte smaller and is as fast as DEC B; JR nz,loop on CPC.
* For a smaller conditional RST #38, use JR cc,-1. This will cause a conditional jump to the displacement byte (#FF) which is the RST #38 opcode.