ROL : ROtate Left

The bits of the source register (snd) are rotated left by either

• a 4-bit immediate value (short immediate or extended immediate forms)
• the other register (si4) (short register or extended register forms)
• a 16-bit value (long immediate form).

Hint with YASEP32 : The ROR instruction rotates the bits right so if a register must be ROLed by more than 15 positions, ROR the register by 32-n positions. This saves two instruction bytes...

ROR 21 R1 ; 21 > 15 so a long instruction is used
ROL 11 R1 ; 11 < 15 so a short instruction is used