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http://reviews.gem5.org/r/2095/
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Review request for Default.
Repository: gem5
Description
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Changeset 9991:ae26c5a9ba33
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cpu: simple: Add support for using branch predictors
This changesets adds branch predictor support to the
BaseSimpleCPU. The simple CPUs normally don't need a branch predictor,
however, there are at least two cases where it can be desirable:
1) A simple CPU can be used to warm the branch predictor of an O3
CPU before switching to the slower O3 model.
2) The simple CPU can be used as a quick way of evaluating/debugging
new branch predictors since it exposes branch predictor
statistics.
Limitations:
* Since the simple CPU doesn't speculate, only one instruction will
be active in the branch predictor at a time (i.e., the branch
predictor will never see speculative branches).
* The outcome of a branch prediction does not affect the performance
of the simple CPU.
Diffs
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src/cpu/simple/BaseSimpleCPU.py 12a0efdde000
src/cpu/simple/base.hh 12a0efdde000
src/cpu/simple/base.cc 12a0efdde000
Diff: http://reviews.gem5.org/r/2095/diff/
Testing
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X86/quick/(fs|se) pass (modulo the additional statistics). We have used it for
a long time to warm branch predictors in several SMARTS-like sampling
strategies with good results.
Thanks,
Andreas Sandberg
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