1. A 2bcgskew Fused by a RHSP Veerle Desmet Hans Vandierendonck Koen De Bosschere Ghent University Member HiPEAC

2. 1st JILP Championship Branch Prediction (CBP-1) --- December 5, 2004 2 A 2bcgskew Fused by a RHSP

3. 1st JILP Championship Branch Prediction (CBP-1) --- December 5, 2004 3 A 2bcgskew Fused by a RHSP 2bcgskew RHSP

4. 1st JILP Championship Branch Prediction (CBP-1) --- December 5, 2004 4 A 2bcgskew... 2bcgskew 4 component predictors: Bimodal Gshare (G0) Gshare (G1) Meta META selects between Majority vote BIM/G0/G1 BIM prediction [André Seznec, 2003]

5. 1st JILP Championship Branch Prediction (CBP-1) --- December 5, 2004 5 A 2bcgskew... 2bcgskew Shared prediction tables: 2 N-1 bias G0/G1 2 N-2 bias BIM/META 2 N-2 hysteresis bits BIM/G0/G1/META Indexing: Bimodal pure addr G0 addr + 12 global hist G1 addr + 24 global hist META addr + 3 global hist

6. 1st JILP Championship Branch Prediction (CBP-1) --- December 5, 2004 6 Fusion principle Hybrid selects component based on META- predictor follows outcome of one component Fusion learns patterns from component outcomes improved accuracy if component outcomes differ [Gabriel Loh, 2002] Component predictors fusion Component predictors meta

7. 1st JILP Championship Branch Prediction (CBP-1) --- December 5, 2004 7... Fused by... Extracts multiple bits from 2bcgskew 9 outcome bits: 2bcgskew BIM bias + hysteresis G0 bias + hysteresis G1 bias + hysteresis META bias + hysteresis

8. 1st JILP Championship Branch Prediction (CBP-1) --- December 5, 2004 8... a RHSP predictor RHSP [André Seznec, 2003]

9. 1st JILP Championship Branch Prediction (CBP-1) --- December 5, 2004 9 Information#bits Global History33 Local History6 Pseudo-tag8 Outcomes9 Bias1 Perceptron Predictor Local history table 512 entries indexed by branch address Pseudo-tag bits higher order address bits not used to select weights [André Seznec, 2003]

10. 1st JILP Championship Branch Prediction (CBP-1) --- December 5, 2004 10 InformationRedundancy#bits Global Historypure33 1 Local Historypure6 15 24 33 Pseudo-tagpure8 18 26 Outcomespure9 Biaspure1 Redundant History Perceptron Predictor 116 n h5h4h3h2h1h0 n-th order redundancy of h: h5h4h3h2h1h0 x4x3x2x1x0

11. 1st JILP Championship Branch Prediction (CBP-1) --- December 5, 2004 11 Redundant History Skewed Perceptron Predictor InformationRedundancy#bitsBank 1Bank 2Bank 3Bank 4 Global Historypure338889 1 8889 Local Historypure61212 151112 241111 330111 Pseudo-tagpure82222 182222 261212 Outcomespure99000 Biaspure11000 34272530

12. 1st JILP Championship Branch Prediction (CBP-1) --- December 5, 2004 12 Redundant History Skewed Perceptron Predictor Bank 1Bank 2Bank 3Bank 4 4 banks 32 entries = 5 bits index indexed by global history and rotation hashing function of branch address 8-bit weights MAC: (A+B, A-B) coding together 116 weights/entry 03510 a5a4 a0a1a2a3 r4r3r2r1r0 a8a7a6

13. 1st JILP Championship Branch Prediction (CBP-1) --- December 5, 2004 13 Budget 2bcgskew 32K bits Fusion RHSP predictor 29K bits Local history 3K bits

14. Performance???

15. The end