39. Shift Instructions Examples

• Count is an immediate value:

      shl    eax, 5
  

• Specification of count greater than 31 is not allowed.

• If greater, only the least significant 5 bits are actually used.

• CL version of shift is useful if shift count is known at run time,

  • e.g. when the shift count is a parameter in a procedure call.

   

• Only CL register can be used.

• Shift count value should be loaded into CL:

      mov    cl, 5
      shl    ax, cl