(15 pts) 3. A Compiler designer is trying to decide between two code sequences f
ID: 3791677 • Letter: #
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(15 pts) 3. A Compiler designer is trying to decide between two code sequences for a computer. The hardware designer have supplied the following facts, there are 4 category of instruction class, A, B, C and D, the CPI for each is given below category of the instuction CPI for this struction class CPI For a particular HLL statement, the compiler writer is considering two code sequences that requires the following instruction counts Code Instruction Counts for instruction class sequence G.1 5 pts): Which code sequence execute the most instruction (3.2 5 pts): Which code sequence will be faster G.3 5 pts): What is the overall CPI for each sequence?Explanation / Answer
1.Which code sequence executes the most instruction ?
Let's count the number of cycles needed to execute each code:
First code sequence: No. of cycles = 2x1 + 1x2 + 2x3 + 2x5 = 20 cycles.
Second code sequnce : No. of cycles = 4x1 + 1x2 + 2x3 +1x5 = 17 cycles.
Therefore the firstcode sequence executes the most instruction.
2.Which code squence will be faster?
Let's count the number of cycles needed to execute each code:
First code: No. of cycles = 2x1 + 1x2 + 2x3 + 2x5 = 20 cycles.
Second code: No. of cycles = 4x1 + 1x2 + 2x3 +1x5 = 17 cycles.
Therefore the second code is faster because it requires less number of cycles to execute.
(# cycles 1)/(# of cycles 2) = 20/17 = 1.17…
Therefore the second code 2 is faster than the first code by 1.17 times.
3.What is the overall CPI for each squence?
CPI1= CPU_cycles1/ Instruction_count1= 20/7 = 2.8
CPI2= CPU_cycles2/ Instruction_count2= 17/8 = 2.1
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