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​​Polonius Roadmap

​​Roadmap

​​Extending Polonius to cover the full semantics

• ​​Integrating liveness polonius#104

• ​​Extend analysis to compute use-live and drop-live variables at each point

• ​​Extend rustc to emit use, drop, and def facts for variables

• ​​Extend rustc to emit types of variables, or at least regions that appear in those types

• ​​Combine to compute which regions are live at which point

• ​​Land changes to polonius

• ​​Land changes to rustc

• ​​Extend drop-live analysis to consider initialization

• ​​Integrating move / overwrite analysis (a la Lark)

• ​​Describe desired rules

• ​​Generate required facts and implement rules to generate errors in polonius

• ​​Report move errors from rustc

• ​​Handling higher-ranked things (intersects universes and traits group)

• ​​see also this blog post and this conversation on zulip

• ​​currently on hold

• ​​Integrating outlives relations (blogpost)

• ​​Validating correctness

• ​​rustc tests: lqd has started an analysis of rustc’s test suite behaviour under `-Zpolonius`

• ​​Cover Polonius’ behaviour in a lot more tests, in both polonius and rustc repos

• ​​Experimental, more precise variant of polonius that doesn’t track subset relations (discussion thread, polonius issue with more details)

​​Benchmarking suite

• ​​Instrument rustc to dump timing measurements + tuple counts for each fn in a crate

• ​​Run instrumented rustc over crates from https://perf.rust-lang.org/ and perhaps other sources

• ​​Assemble data into a spreadsheet and attempt to select outlier functions

• ​​Extract data from them and store into polonius repository to form a benchmarking suite

• ​​Bonus: modify travis setup to do measurements =)

​​Rustc Performance

• ​​Identify outliers in performance + memory usage

• ​​Examine outliers to characterize why they are slow

• ​​Identify "common case" overhead and some representative tests

• ​​Try to figure out why that is slow

• ​​Extract the facts and do isolated testing of Polonius

• ​​Explore the ‘location insensitive first’ variant

• ​​Initially, just use a filter for whether to try the more complex variants

• ​​Later, can we use the more complex variants to 

​​Documentation

• ​​What design document do we want and when?

• ​​Videos and things to try and explain

• ​​Introduction to Polonius (sort of done, Niko has to post)

• ​​More complex examples, like the dreaded #47680.

• ​​Walk through a simple example and connect it to the code

• ​​here is where we compute this relation

• ​​here is how data is transferred between rustc

• ​​here is how the datafrog code works

• ​​How datafrog-opt works and how it relates to the naive check

​​2019.03.21

​​Tasks: