Struct rustc_query_system::dep_graph::graph::CurrentDepGraph

pub(in dep_graph) struct CurrentDepGraph<K> {
    data: Lock<IndexVec<DepNodeIndex, DepNodeData<K>>>,
    node_to_node_index: Sharded<FxHashMap<DepNode<K>, DepNodeIndex>>,
    forbidden_edge: Option<EdgeFilter>,
    anon_id_seed: Fingerprint,
    total_read_count: AtomicU64,
    total_duplicate_read_count: AtomicU64,
}

CurrentDepGraph stores the dependency graph for the current session. It will be populated as we run queries or tasks.

The nodes in it are identified by an index (DepNodeIndex). The data for each node is stored in its DepNodeData, found in the data field.

We never remove nodes from the graph: they are only added.

This struct uses two locks internally. The data and node_to_node_index fields are locked separately. Operations that take a DepNodeIndex typically just access the data field.

The only operation that must manipulate both locks is adding new nodes, in which case we first acquire the node_to_node_index lock and then, once a new node is to be inserted, acquire the lock on data.

Fields

data: Lock<IndexVec<DepNodeIndex, DepNodeData<K>>>

node_to_node_index: Sharded<FxHashMap<DepNode<K>, DepNodeIndex>>

forbidden_edge: Option<EdgeFilter>

Used to trap when a specific edge is added to the graph. This is used for debug purposes and is only active with debug_assertions.

anon_id_seed: Fingerprint

Anonymous DepNodes are nodes whose IDs we compute from the list of their edges. This has the beneficial side-effect that multiple anonymous nodes can be coalesced into one without changing the semantics of the dependency graph. However, the merging of nodes can lead to a subtle problem during red-green marking: The color of an anonymous node from the current session might "shadow" the color of the node with the same ID from the previous session. In order to side-step this problem, we make sure that anonymous NodeIds allocated in different sessions don't overlap. This is implemented by mixing a session-key into the ID fingerprint of each anon node. The session-key is just a random number generated when the DepGraph is created.

total_read_count: AtomicU64

These are simple counters that are for profiling and debugging and only active with debug_assertions.

total_duplicate_read_count: AtomicU64

Implementations

impl<K: DepKind> CurrentDepGraph<K>

pub(in dep_graph::graph) fn new(
    prev_graph_node_count: usize
) -> CurrentDepGraph<K>

pub(in dep_graph::graph) fn complete_task(
    &self,
    node: DepNode<K>,
    task_deps: TaskDeps<K>,
    fingerprint: Fingerprint
) -> DepNodeIndex

pub(in dep_graph::graph) fn complete_anon_task(
    &self,
    kind: K,
    task_deps: TaskDeps<K>
) -> DepNodeIndex

pub(in dep_graph::graph) fn alloc_node(
    &self,
    dep_node: DepNode<K>,
    edges: SmallVec<[DepNodeIndex; 8]>,
    fingerprint: Fingerprint
) -> DepNodeIndex

pub(in dep_graph::graph) fn intern_node(
    &self,
    dep_node: DepNode<K>,
    edges: SmallVec<[DepNodeIndex; 8]>,
    fingerprint: Fingerprint
) -> DepNodeIndex