3_JumpPredictorsSimulation

Simulation of Jump Predictors

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University of Costa Rica

Belinda Brown, [email protected]

September, 2020

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Four types of jump predictor:

Average of time running less than 29 seconds for a sixteen million conditional jumps trace.

1.Bimodal (-bp 0):

Two bits counter Has four types of posible values:

• Strongly taken - 11 = 3
• Weakly taken - 10 = 2
• Weakly not taken - 01 = 1
• Strongly not taken - 00 = 0

Table counter & all couter init in Strongly not taken, also known as Decode History Table DHT

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                        Two bit table

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     MSB                                                  LSB
      X                                                    X
 bit address/prediction              -           Prediction/Conviction
  [taken/untaken]                    -                 How sure?

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branch-trace-gcc.trace.gz | branch -s < # > -bp < # > -gh < # > -ph < # >

-> file_name: Compress file entry

-> s: Branch History Table (BHT) size

-> gh: GShare size (given value)

-> ph: PShare size (given value)

2.Private History (-bp 1):

Table counter & all couter init in Strongly not taken Has four types of posible values:

• Strongly taken - 11 = 3
• Weakly taken - 10 = 2
• Weakly not taken - 01 = 1
• Strongly not taken - 00 = 0

Table counter & all couter init in Strongly not taken, also known as Decode History Table DHT

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                        Two bit table

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     MSB                                                  LSB
      X                                                    X
 bit address/prediction              -           Prediction/Conviction
  [taken/untaken]                    -                 How sure?

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branch-trace-gcc.trace.gz | branch -s < # > -bp < # > -gh < # > -ph < # >

-> file_name: Compress file entry

-> s: Branch History Table (BHT) size

-> gh: GShare size (given value)

-> ph: PShare size (given value)

This one follows the same logic but it consider all the history of each branch so the output is a table.

3.Global History (-bp 2):

Two bits counter plus a eregister that contains the history of the last branches. It's needed the last n bits as a result of the XOR operation between the counter and the history counter. All counter are initalize in strong not taken.

branch-trace-gcc.trace.gz | branch -s < # > -bp < # > -gh < # > -ph < # >

-> file_name: Compress file entry

-> s: Branch History Table (BHT) size

-> gh: GShare size (given value)

-> ph: PShare size (given value)

4."Tournament" (-bp 3):

This one choose between GShare and Pshare.

Compile Instructions

Remember the requested command:

gunzip -c branch-trace-gcc.trace.gz | branch -s < # > -bp < # > -gh < # > -ph < # >

Where:

-> file_name: Compress file entry

-> s: Branch History Table (BHT) size

-> gh: GShare size (given value)

-> ph: PShare size (given value)

Entry to run a general configuration ----> s = 16, bp = 0, gh = 4, ph = 3:

<path this reposity on your local machine>$ make run

Or entry for example:

<path this reposity on your local machine>$ make run BP <value>