Migrate borrowck dataflow impls to new framework #68241

ecstatic-morse · 2020-01-15T06:31:21Z

This uses #65672 to implement the dataflow analyses needed by borrowck. These include all the InitializedPlaces analyses as well as Borrows. Additionally, this PR contains several independent changes around the dataflow API which improve performance and make it more ergonomic.

An optimization that inhibits the caching of block transfer functions for acyclic MIR (~0.3% I-CNT savings).
A ResultsVisitor for dataflow results that is more efficient than ResultsCursor when we have to visit every statement unconditionally (~0.3% I-CNT savings).
An into_engine method on Analysis that selects the appropriate Engine constructor.
A contains method for ResultsCursor as a shorthand for .get().contains().
A find_descendants helper on MovePath that replaces has_any_child_of on the old FlowsAtLocation

These changes made porting the dataflow analyses much easier. Finally, this PR removes some now-unused code in dataflow/at_location.rs and elsewhere.

You can view the perf results for the final version of this PR here. Here's an example of the graphviz diagrams that are generated for the MaybeInitializedPlaces analysis.

ecstatic-morse · 2020-01-15T06:32:27Z

@bors try
@rust-timer queue

rust-timer · 2020-01-15T09:23:35Z

Queued 31ca0fd7b109756a7c52baff29870d7831f3e723 with parent 4b172cc, future comparison URL.

ecstatic-morse · 2020-01-15T22:45:07Z

Now without caching block transfer functions on acyclic MIR.

@bors try
@rust-timer queue

rust-timer · 2020-01-16T01:53:38Z

Queued b685c41b5ae4fe1476ec71023ad348b57781105c with parent 3291ae3, future comparison URL.

rust-timer · 2020-01-16T06:01:35Z

Finished benchmarking try commit b685c41b5ae4fe1476ec71023ad348b57781105c, comparison URL.

ecstatic-morse · 2020-01-20T06:50:02Z

Once more but using a Visitor instead of a ResultsCursor. This should indicate whether ResultsCursor has meaningful overhead. I suspect it does not, but I'm happy to be proved wrong.

@bors try
@rust-timer queue

pnkfelix · 2020-02-11T03:26:16Z

Okay I'm done with the review.

I had some nits, but they are mostly about clarifying the commit messages or the commit history, along with a few small stylistic issues; so the fixes should be easy.

r=me after fixes are made.

ecstatic-morse · 2020-02-11T22:18:36Z

@pnkfelix I believe all of your concerns have been addressed and I have put the mutate_place for TerminatorKind::Yield in the correct place. Feel free to look at the new comment on Analysis::into_engine, but in the meantime:

@bors r=pnkfelix

bors · 2020-02-11T22:18:38Z

📌 Commit 5f40fe9 has been approved by pnkfelix

ecstatic-morse · 2020-02-11T22:19:29Z

@bors rollup=never

…ls, r=pnkfelix Migrate borrowck dataflow impls to new framework This uses rust-lang#65672 to implement the dataflow analyses needed by borrowck. These include all the `InitializedPlaces` analyses as well as `Borrows`. Additionally, this PR contains several independent changes around the dataflow API which improve performance and make it more ergonomic. * An optimization that inhibits the caching of block transfer functions for acyclic MIR (~0.3% I-CNT savings). * A `ResultsVisitor` for dataflow results that is more efficient than `ResultsCursor` when we have to visit every statement unconditionally (~0.3% I-CNT savings). * An `into_engine` method on `Analysis` that selects the appropriate `Engine` constructor. * A `contains` method for `ResultsCursor` as a shorthand for `.get().contains()`. * A `find_descendants` helper on `MovePath` that replaces `has_any_child_of` on the old `FlowsAtLocation` These changes made porting the dataflow analyses much easier. Finally, this PR removes some now-unused code in `dataflow/at_location.rs` and elsewhere. You can view the perf results for the final version of this PR [here](https://perf.rust-lang.org/compare.html?start=29b854fb741809c29764e33fc17c32ba9c6523ba&end=6e516c1410c18cfe4eb6d030a39fdb73c8d8a4fe). Here's an example of the graphviz diagrams that are generated for the `MaybeInitializedPlaces` analysis. ![image](https://user-images.githubusercontent.com/29463364/72846117-c3e97d80-3c54-11ea-8171-3d48981c9ddd.png)

Dylan-DPC-zz · 2020-02-12T12:57:45Z

@bors p=1

bors · 2020-02-12T13:17:05Z

⌛ Testing commit 5f40fe9 with merge 2ed25f0...

Migrate borrowck dataflow impls to new framework This uses #65672 to implement the dataflow analyses needed by borrowck. These include all the `InitializedPlaces` analyses as well as `Borrows`. Additionally, this PR contains several independent changes around the dataflow API which improve performance and make it more ergonomic. * An optimization that inhibits the caching of block transfer functions for acyclic MIR (~0.3% I-CNT savings). * A `ResultsVisitor` for dataflow results that is more efficient than `ResultsCursor` when we have to visit every statement unconditionally (~0.3% I-CNT savings). * An `into_engine` method on `Analysis` that selects the appropriate `Engine` constructor. * A `contains` method for `ResultsCursor` as a shorthand for `.get().contains()`. * A `find_descendants` helper on `MovePath` that replaces `has_any_child_of` on the old `FlowsAtLocation` These changes made porting the dataflow analyses much easier. Finally, this PR removes some now-unused code in `dataflow/at_location.rs` and elsewhere. You can view the perf results for the final version of this PR [here](https://perf.rust-lang.org/compare.html?start=29b854fb741809c29764e33fc17c32ba9c6523ba&end=6e516c1410c18cfe4eb6d030a39fdb73c8d8a4fe). Here's an example of the graphviz diagrams that are generated for the `MaybeInitializedPlaces` analysis. ![image](https://user-images.githubusercontent.com/29463364/72846117-c3e97d80-3c54-11ea-8171-3d48981c9ddd.png)

bors · 2020-02-12T16:25:06Z

☀️ Test successful - checks-azure
Approved by: pnkfelix
Pushing 2ed25f0 to master...

…ls2, r=eddyb Use `ResultsCursor` for `elaborate_drops` Some cleanup after rust-lang#68241. The old code was using a custom cursor-like struct called `InitializationData`.

Use `ResultsCursor` for `elaborate_drops` Some cleanup after #68241. The old code was using a custom cursor-like struct called `InitializationData`.

…sleywiser Combine `HaveBeenBorrowedLocals` and `IndirectlyMutableLocals` into one dataflow analysis This PR began as an attempt to port `HaveBeenBorrowedLocals` to the new dataflow framework (see #68241 for prior art). Along the way, I noticed that it could share most of its code with `IndirectlyMutableLocals` and then found a few bugs in the two analyses: - Neither one marked locals as borrowed after an `Rvalue::AddressOf`. - `IndirectlyMutableLocals` was missing a minor fix that `HaveBeenBorrowedLocals` got in #61069. This is not a problem today since it is only used during const-checking, where custom drop glue is forbidden. However, this may change some day. I decided to combine the two analyses so that they wouldn't diverge in the future while ensuring that they remain distinct types (called `MaybeBorrowedLocals` and `MaybeMutBorrowedLocals` to be consistent with the `Maybe{Un,}InitializedPlaces` naming scheme). I fixed the bugs and switched to exhaustive matching where possible to make them less likely in the future. Finally, I added comments explaining some of the finer points of the transfer function for these analyses (see #61069 and #65006).

@tmandry

…tmandry Use new dataflow framework for generators #65672 introduced a new dataflow framework that can handle arbitrarily complex transfer functions as well as ones expressed as a series of gen/kill operations. This PR ports the analyses used to implement generators to the new framework so that we can remove the old one. See #68241 for a prior example of this. The new framework has some superficial API changes, but this shouldn't alter the generator passes in any way. r? @tmandry