[理工] 計組-data dependency

[SiriusCloud (古月小楓)]

Given 4 instructions , how many unique comparions

(between register source and destinations) are

necessary to find all of the RAW,WAR,WAW data dependences,

Answer for the case of 4 instructions , and then

derive a general equations for N instructions .

Assume that all instructions have one register

destination and two register source.

(answer)

For four instructions , the number of unique comparions:

(2(3) + 2(2) + 2(1)) + (2(3) + 2(2) + 2(1)) + (3 + 2 + 1 ) = 30
^^^^^^^^^^^^^^^^^^^^   ^^^^^^^^^^^^^^^^^^^^   ^^^^^^^^^^^^
↑RAW                     ↑WAR                 ↑WAW


                                              n-1
The general equation for N instructions = 5 * Σ  i = (5*(n -1)*n) / 2
                                              i=1


想請問的是4道指令答案是怎麼推導的呢？

還有一般式如何推導出來？

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※ 發信站: 批踢踢實業坊(ptt.cc) 
◆ From: 114.41.129.247
推 CrazyBoss:A=B+C
→ CrazyBoss:C=A-B
→ CrazyBoss:D=A+C
→ CrazyBoss:A=B*C
→ CrazyBoss:已RAW為例:第一輪A與下面3個指令等號左邊的2個Reg比2(3)
→ CrazyBoss:          第二輪C與下面2個指令等號左邊的2個Reg比2(2)
→ CrazyBoss:再來應該會了
推 jim055006:太清楚了....樓上好強大~~
→ SiriusCloud:不好意思 請問等號左邊有兩個reg @@???
推 CrazyBoss:右邊，不好意思打錯