Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

fix: Avoid panic petgraph-related panic when inserting clone nodes to fix borrow checking errors #334

Merged
merged 1 commit into from
Sep 2, 2024
Merged

fix: Avoid panic petgraph-related panic when inserting clone nodes to fix borrow checking errors #334

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
35 changes: 24 additions & 11 deletions libs/pavexc/src/compiler/analyses/call_graph/borrow_checker/move_while_borrowed.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -70,11 +70,11 @@ pub(super) fn move_while_borrowed(
visited_nodes.insert(node_index);
let node = &call_graph[node_index];

let mut directly_borrows_from = IndexSet::new();
let mut transitively_borrows_from = IndexSet::new();
let mut directly_borrowed = IndexSet::new();
let mut captured = IndexSet::new();
if let Some(hydrated_component) = node.as_hydrated_component(component_db, computation_db) {
if let Computation::Callable(callable) = hydrated_component.computation() {
directly_borrows_from = callable
directly_borrowed = callable
.inputs_that_output_borrows_immutably_from()
.iter()
.map(|&i| {
Expand All @@ -86,7 +86,7 @@ pub(super) fn move_while_borrowed(
}
})
.collect();
transitively_borrows_from = callable
captured = callable
.inputs_with_lifetime_tied_with_output()
.iter()
.map(|&i| {
Expand All @@ -100,7 +100,7 @@ pub(super) fn move_while_borrowed(
.collect();
#[cfg(debug_assertions)]
{
assert!(directly_borrows_from.is_subset(&transitively_borrows_from));
assert!(directly_borrowed.is_subset(&captured));
}
}
}
Expand Down Expand Up @@ -132,7 +132,10 @@ pub(super) fn move_while_borrowed(
let Some(dependency_type) = dependency_type else {
continue 'inner;
};
if transitively_borrows_from.contains(&dependency_type) {
if captured.contains(&dependency_type) {
// The capture relationship is transitive:
// if `A` captures `B` and `B` captures `C`, then `A` also captures `C`.
// We update `node2captured_nodes` to reflect this.
let transitively_captured = node2captured_nodes
.get(&dependency_index)
.cloned()
Expand All @@ -142,7 +145,7 @@ pub(super) fn move_while_borrowed(
.or_default()
.extend(transitively_captured);
}
if directly_borrows_from.contains(&dependency_type) {
if directly_borrowed.contains(&dependency_type) {
node2captured_nodes
.entry(node_index)
.or_default()
Expand Down Expand Up @@ -192,18 +195,16 @@ pub(super) fn move_while_borrowed(
let edge_metadata = call_graph.edge_weight(*edge_id).unwrap();
let dependency_index = call_graph.edge_endpoints(*edge_id).unwrap().0;

if let Some(held) = node2captured_nodes.get(&dependency_index) {
borrowed_immutably_now.extend(held);
if let Some(captured) = node2captured_nodes.get(&dependency_index) {
borrowed_immutably_now.extend(captured);
}
match edge_metadata {
CallGraphEdgeMetadata::HappensBefore | CallGraphEdgeMetadata::Move => {}
CallGraphEdgeMetadata::ExclusiveBorrow => {
borrowed_mutably_now.insert(dependency_index);
return;
}
CallGraphEdgeMetadata::SharedBorrow => {
borrowed_immutably_now.insert(dependency_index);
return;
}
}
});
Expand Down Expand Up @@ -256,6 +257,18 @@ pub(super) fn move_while_borrowed(
borrowed.extend(&borrowed_later);
node2borrows.insert(node_index, borrowed);
visited_nodes.insert(node_index);

// Why is this necessary?
// We use `StableGraph` for our call graphs. For `StableGraph`, `DfsPostOrder` relies
// on `FixedBitSet` as the storage data structure for both discovered and finished
// nodes. The bit set is initialized with a fixed capacity equal to the number of nodes in
// the graph _at the time of its creation_. If we add new nodes to the graph after the
// bit set has been initialized, `petgraph` doesn't automatically grow the bit set capacity,
// causing a panic when we inevitably go past the initial capacity.
// To avoid this, we manually resize the bit set here, at the end of each
// iteration of the loop, before calling `dfs.next()`.
dfs.discovered.grow(call_graph.node_count());
dfs.finished.grow(call_graph.node_count());
}

CallGraph {
Expand Down