Question

Question 12) Consider the following MIPS code. DADDIU Loop: L.D L.D MUL.D S.D DADDIU DADDIU DSUBU BNEZ R4, Rx, #512 F2, (Rx) F4, 0(Ry) F4, F4, F2 F4, (Ry) Rx, Rx, #8 Rx, Rx, #8 R20, R4, Rx R20, Loop last address :load vector1 load vector2 multiply vectors store result increment address increment address ;limit calculation ;Loop a) What will be total number of dynamic instructions in this program? b) The code now runs on a MIPS processor with one ALU unit in an in-order execution. The latencies of each instruction are as follows: DADDIU/DSUBU - 3 cycles, L.D/S.D - 2 cycles, MUL.D-5 cycles, BNEZ - 1 cycle. What is the execution time in cycles for the above program?

Answer 1

a)

The dynamic instruction in the program is that instruction which is actually executed by the program during the execution.

Here, the dynamic instruction count depends on the number of the execution of the loop instruction.

Here, the loop executes until the value of R20 is not computed zero.

The number to time loop needs to be exited to get R20 value to 0  is 64.

Total dynamic instruction count = 1 + 64(8) = 513

b) Number of cycles for the execution of the above program is

= _^$\sum$ (Instrcution count of each insutction * Cycles required for that instruction)   

=1*3 + 64(2 + 2 + 5 +2 + 3 + 3 + 3 +1 )

=1347