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More diddling with theory

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peteraa 2019-10-17 19:20:34 +02:00
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@ -95,9 +95,8 @@
#+end_src #+end_src
* Question 3 - Branch prediction * Question 3 - Branch prediction
Consider a 2 bit branch predictor with only 4 slots where the decision to take a branch or Consider a 2 bit branch predictor with only 4 slots for a 32 bit architecture, where the decision to
not is decided in accordance to the following table take a branch or not is decided in accordance to the following table:
#+begin_src text #+begin_src text
state || predict taken || next state if taken || next state if not taken || state || predict taken || next state if taken || next state if not taken ||
=======||=================||=======================||==========================|| =======||=================||=======================||==========================||
@ -108,7 +107,6 @@
#+end_src #+end_src
At some point during execution the program counter is ~0xc~ and the branch predictor table looks like this: At some point during execution the program counter is ~0xc~ and the branch predictor table looks like this:
#+begin_src text #+begin_src text
slot || value slot || value
======||======== ======||========
@ -118,7 +116,7 @@
11 || 01 11 || 01
#+end_src #+end_src
For the following program:
#+begin_src asm #+begin_src asm
0xc addi x1, x3, 10 0xc addi x1, x3, 10
0x10 add x2, x1, x1 0x10 add x2, x1, x1
@ -190,10 +188,13 @@
} }
#+END_SRC #+END_SRC
** TODO Branch predictor is underspecified, needs to be cleaned up
** Your task ** Your task
Your job is to implement a test that checks how many misses occur for a 2 bit branch predictor with 4 slots. Your job is to implement a test that checks how many misses occur for a 2 bit branch predictor with 8 slots.
For this task it is probably smart to use something else than a ~Map[(Int, Boolean)]~ The rule table is the same as in question 3.
For simplicitys sake, assume that every value in the table is initialized to 00.
For this task it is necessary to use something more sophisticated than ~Map[(Int, Boolean)]~ to represent
your branch predictor model.
The skeleton code is located in ~testRunner.scala~ and can be run using testOnly FiveStage.ProfileTest. The skeleton code is located in ~testRunner.scala~ and can be run using testOnly FiveStage.ProfileTest.