1. Performance-oriented Peephole Optimisation of Balsa Dual-Rail Circuits
Luis Tarazona and Doug Edwards
Advanced Processor Technologies Group
School of Computer Science

2. Syntax-directed compilation
Used in Tangram and Balsa
One-to-one mapping of each language construct into a network of handshake components (HCs)
Benefits:
Transparency and flexibility to the designer
Drawback: medium-low performance
Solutions to this have been proposed using:
Control resynthesis
Peephole optimisation

3. Related work
Tangram and Balsa compilers perform some peephole optimisations as a post processing step
T. Chelcea has proposed resynthesis and peephole optimisations for Balsa, targeting a burst-mode back-end
Plana et al. have proposed some optimised HCs for Balsa targeting single rail and dual-rail back-ends
Main interest of this work is on dual-rail back-ends due to its potential immunity to process variability.

4. The optimisations Eliminating redundant FalseVariable components
New Concurrent RTZ Fetch component
Conditional parallel/sequencer component: ParSeq

5. Eliminating redundant FVs
i -> then
CMD
end
Targets active input control
Single access, single read-port FalseVariable or eagerFalseVariable HCs

6. Eliminating redundant FVs - Example
a, b -> then
o <- a + b
end
Latency and area reduction
Preserves external behaviour

7. Wires-only dual-rail Fetch and its STG
Concurrent RTZ Fetch
Wires-only dual-rail Fetch and its STG

8. New concurrent RTZ Fetch and its STG

9. The ParSeq
Acts conditionally as a Concur (parallel) or as a Sequencer HC
Few opportunities to apply it in the design examples available
Perhaps caused by its inexistence at that time?
Interesting increase in performance, though.

10. Handshake circuit implementation||

11. Optimised ParSeq Schematics

12. Simulation Results
Pre-layout, transistor-level simulations, 180nm technology

13. Conclusions and Future Work
To incorporate the optimisations into the Balsa design flow
ParSeq as a construct or as a peephole optimisation?
To evaluate other peephole and HCs optimisations currently under study

14. Thank you very much! Questions? Acknowledgement
Thanks to Luis Plana, Andrew, Charlie and Will for their suggestions and comments.
This work and PhD are supported by EPSCR and UoM School of Computer Science scholarships.