Look at the assembly instructions below. These instructions will be pipelined to

Question

Look at the assembly instructions below. These instructions will be pipelined to speed up the code execution. Unfortunately the code cannot be pipelined as is due to data dependencies. Add 'NOP' instruction in the code below at the appropriate locations to ensure that pipelining can be accomplished. (blank means do not add a NOP", 1NOP means add one line of "NOP, 2NOP means add two lines of 'NOP, 3NOP means add three lines of NOP) mov $10, 9seax Choose add $2, %eax Choose mov $4, %ebx Choose mov $5, %ecx Choose add $1, %ebx Choose add $1, %ecx Choose

Explanation / Answer

//pipeline can be done with NOP

solution:

mov $10, %eax

3NOP

add $2, %eax

(blank/No NOP)

mov $4, %ebx

(blank/No NOP)

mov $5, %ecx

2NOP

add $1, %ebx

(blank/No NOP)

add $1, %ecx

3NOP

add %ecx, %eax

(blank/No NOP)

add %ebx, %eax $10, %eax

Explanation:

Instruction Cycle 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

mov $10, %eax F D E M W

NOP

NOP

NOP

add $2, %eax F D E M W

mov $4, %ebx F D E M W

mov $5, %ecx F D E M W

NOP

NOP

add $1, %ebx F D E M W

add $1, %ecx F D E M W

NOP

NOP

NOP

add %ecx, %eax F D E M W   

add %ebx, %eax F D E M W

where f->fetch, D->decode, E->excute, M-> memory access, W-> write

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