Instruction

Question 1

Multiplication of constant using barrel shifter

Answer 1

• by 2^n
  ~~~
  MOV Ra,Rb,LSL #n
  ~~~
• by 2^n+1
  ~~~
  ADD Ra,Ra,Ra,LSL #n
  ~~~
• by 2^n-1
  ~~~
  RSB Ra,Ra,Ra LSL #n
  ~~~
• by 6
• by 10 and add extra number

Question 2

features of MUL instr

Answer 2

1. ̥second operand can’t be immediate
2. result register must diff from first operand
3. cycles depend on core type
4. if S bit set — c flag is meaningless