CS350 Intro Computer Systems Homework

Homework 9 on Issues in Pipelining

While it increases the throughput of a computer system, pipelining presents challenges in data hazards, branch misprediction and return among others as we discussed in class. Fill the yellow cells of the spreadsheet with values when the three sets of instructions shown below are executed on the pipepline.

1. data hazards: page 27 of lecture note 04-pipeline-a.pptx:

   0x000: irmovq $10,%rdx
   0x00a: irmovq $3,%rax
   0x014: addq %rdx,%rax
   0x016: halt
   

2. branch misprediction: page 28 of lecture note 04-pipeline-a.pptx:

   0x000:    xorq %rax,%rax 
   0x002:    jne  t             # Not taken
   0x00b:    irmovq $1, %rax    # Fall through
   0x015:    nop
   0x016:    nop
   0x017:    nop
   0x018:    halt
   0x019: t: irmovq $3, %rdx    # Target (Should not execute)
   0x023:    irmovq $4, %rcx    # Should not execute
   0x02d:    irmovq $5, %rdx    # Should not execute
   

3. return: page 30 of lecture note 04-pipeline-a.pptx:

   0x000:    irmovq Stack,%rsp  # Intialize stack pointer
   0x00a:    nop                  # Avoid hazard on %rsp
   0x00b:    nop
   0x00c:    nop
   0x00d:    call p               # Procedure call
   0x016:    irmovq $5,%rsi       # Return point
   0x020:    halt
   0x020: .pos 0x20
   0x020: p: nop                   # procedure
   0x021:    nop
   0x022:    nop
   0x023:    ret
   0x024:    irmovq $1,%rax        # Should not be executed
   0x02e:    irmovq $2,%rcx        # Should not be executed
   0x038:    irmovq $3,%rdx        # Should not be executed
   0x042:    irmovq $4,%rbx        # Should not be executed
   0x100: .pos 0x100
   0x100: Stack:                   # Initial stack pointer