挑最差的 3 號出來研究

 3. Bypasses stalled add     108     107     92     109

case 3: independent branch, taken

  addi x10, x0, 80
  addi x11, x0, 2
  div  x1, x10, x11       # x1 = 40
  add  x2, x1, x1        # waits for DIV; x2 = 80
  beq  x0, x0, target    # ready without DIV
  addi x2, x0, 99        # skipped architecturally
  target: mul x3, x10, x11  # x3 = 160

分析的部分趕工中，晚點補上!

另外加了一個 sequence 讓有 rename recovery 的 out of order cpu 平反一下

  addi x10, x0, 120
  addi x11, x0, 3

  div  x1, x10, x11      # x1 = 40
  div  x2, x1,  x11      # Waits for first DIV; x2 = 13
  add  x3, x2,  x2       # Waits for second DIV; x3 = 26
  beq  x1, x0,  done     # Needs only first DIV; NOT taken

  # Independent of both divides: a chain of useful younger work
  addi x4,  x0,  7
  addi x5,  x4,  1
  addi x6,  x5,  1
  addi x7,  x6,  1
  addi x8,  x7,  1
  addi x9,  x8,  1
  addi x10, x9,  1
  addi x11, x10, 1
  addi x12, x11, 1
  addi x13, x12, 1
  addi x14, x13, 1

  done:
  add  x20, x14, x3      # Joins both dependency chains; x20 = 43