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Describe how to generate graphviz diagrams for dataflow

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Dylan MacKenzie 2020-09-15 19:20:11 -07:00 committed by Joshua Nelson
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src/mir/dataflow.md
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@ -154,8 +154,24 @@ for (bb, block) in body.basic_blocks().iter_enumerated() {
}
```
### Graphviz Diagrams
When the results of a dataflow analysis are not what you expect, it often helps
to visualize them. This can be done with the `-Zdump-mir` flags described in
[Debugging MIR]. Start with `-Zdump-mir=F -Zdump-mir-dataflow`, where `F` is
either "all" or the name of the MIR body you are interested in.
These `.dot` files will be saved in your `mir_dump` directory and will have the
`NAME` of the analysis (e.g. `maybe_inits`) as part of their filename. Each
visualization will display the full dataflow state at entry and exit of each
block, as well as any changes that occur in each statement and terminator. See
the example below:
![A graphviz diagram for a dataflow analysis](../img/dataflow-graphviz-example.png)
["gen-kill" problems]: https://en.wikipedia.org/wiki/Data-flow_analysis#Bit_vector_problems
[*Static Program Analysis*]: https://cs.au.dk/~amoeller/spa/
[Debugging MIR]: ./debugging.html
[`AnalysisDomain`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_mir/dataflow/trait.AnalysisDomain.html
[`Analysis`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_mir/dataflow/trait.Analysis.html
[`Engine`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_mir/dataflow/struct.Engine.html

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src/mir/debugging.md
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@ -6,6 +6,8 @@ additional output formats, including:
* `-Zdump-mir-graphviz` - dumps a `.dot` file that represents MIR as a
control-flow graph
* `-Zdump-mir-dataflow` - dumps a `.dot` file showing the [dataflow state] at
each point in the control-flow graph
* `-Zdump-mir-spanview` - dumps an `.html` file that highlights the source
spans associated with MIR elements (including mouse-over actions to reveal
elements obscured by overlaps, and tooltips to view the MIR statements).
@ -87,3 +89,5 @@ rustc.main.002-006.NoLandingPads.before.mir
that appeared within the `main` function.)
TODO: anything else?
[dataflow state]: ./dataflow.html#graphviz-diagrams