Table of Contents
Branch prediction techniques
Dynamic branch prediction
Basic idea
Penalties (Predict/ actual) BPT improves only the T/T case In what’s below the number of stall cycles (bubbles) is for a simple pipe. It would be larger for deeper pipes.
Branch prediction tables and buffers
Simplest design
Improve prediction accuracy (2-bit saturating counter scheme) Property: takes two wrong predictions before it changes T to NT (and vice-versa)
More than 2 bits
Where to put the BPT
Performance of BPT’s
Prediction accuracy
Branch Table Buffers
BTB layout
Decoupled BPT and BTB
Decoupled BTB
Correlated or 2-level branch prediction
What should a good predictor do?
General idea
Classification
Two level Global predictors
Two level per-address predictors
Evaluation
Pentium Pro
Return jump stack
Resume buffer
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Author: cselab
Email: baer@cs
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