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Avoid building a get_or_init closure on the reverse-index lookup hot path #25

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Avoid building a get_or_init closure on the reverse-index lookup hot path #25

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21 changes: 13 additions & 8 deletions compiler/rustc_middle/src/dep_graph/serialized.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -167,8 +167,8 @@ struct LazyKindIndex {
}

impl LazyKindIndex {
/// Returns this kind's `key_fingerprint -> node index` map.
fn fingerprint_map(
/// Builds and returns this kind's `key_fingerprint -> node index` map.
fn build_fingerprint_map(
&self,
kind: DepKind,
nodes: &IndexSlice<SerializedDepNodeIndex, DepNode>,
Expand Down Expand Up @@ -235,12 +235,17 @@ impl SerializedDepGraph {
#[inline]
pub fn node_to_index_opt(&self, dep_node: &DepNode) -> Option<SerializedDepNodeIndex> {
let kind = self.reverse_index.kinds.get(dep_node.kind.as_usize())?;
let map = kind.fingerprint_map(
dep_node.kind,
&self.nodes,
&self.reverse_index.nodes_by_kind,
&self.profiler,
);
// perf: `get()` before `get_or_init()` keeps the build closure and its call
// off the hot path; the `Some` arm is then just an inlined `OnceLock` load.
let map = match kind.map.get() {
Some(map) => map,
None => kind.build_fingerprint_map(
dep_node.kind,
&self.nodes,
&self.reverse_index.nodes_by_kind,
&self.profiler,
),
};
map.get(&dep_node.key_fingerprint).copied()
}

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