Title
Dynamic history-length fitting: a third level of adaptivity for branch prediction
Abstract
Accurate branch prediction is essential for obtaining high performance in pipelined superscalar processors that execute instructions speculatively. Some of the best current predictors combine a part of the branch address with a fixed amount of global history of branch outcomes in order to make a prediction. These predictors cannot perform uniformly well across all workloads because the best amount of history to be used depends on the code, the input data and the frequency of context switches. Consequently, all predictors that use a fixed history length are therefore unable to perform up to their maximum potential.We introduce a method---called DHLF---that dynamically determines the optimum history length during execution, adapting to the specific requirements of any code, input data and system workload. Our proposal adds an extra level of adaptivity to two-level adaptive branch predictors. The DHLF method can be applied to any one of the predictors that combine global branch history with the branch address. We apply the DHLF method to gshare (dhlf-gshare) and obtain near-optimal results for all SPECint95 benchmarks, with and without context switches. Some results are also presented for gskewed (dhlf-gskewed), confirming that other predictors can benefit from our proposal.
Year
DOI
Venue
1998
10.1145/279358.279379
Proceedings of the 40th Annual International Symposium on Computer Architecture
Keywords
Field
DocType
branch prediction
Computer science,Workload,Speculative execution,Parallel computing,Real-time computing,Superscalar,Branch predictor,Context switch
Conference
Volume
Issue
ISSN
26
3
0163-5964
ISBN
Citations 
PageRank 
0-8186-8491-7
50
4.23
References 
Authors
12
3
Name
Order
Citations
PageRank
Toni Juan152041.42
Sanji Sanjeevan2504.23
Juan J. Navarro332342.90