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Improve efficiency of has_back_edge(...)

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This commit is contained in:
Bryan Garza 2023-01-06 22:04:25 +00:00
parent 7618163a1c
commit 1bbd655888
2 changed files with 18 additions and 10 deletions
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7
compiler/rustc_data_structures/src/graph/dominators/mod.rs
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@ -304,13 +304,18 @@ fn compress(
}
}
/// Tracks the list of dominators for each node.
#[derive(Clone, Debug)]
pub struct Dominators<N: Idx> {
post_order_rank: IndexVec<N, usize>,
// Even though we track only the immediate dominator of each node, it's
// possible to get its full list of dominators by looking up the dominator
// of each dominator. (See the `impl Iterator for Iter` definition).
immediate_dominators: IndexVec<N, Option<N>>,
}
impl<Node: Idx> Dominators<Node> {
/// Whether the given Node has an immediate dominator.
pub fn is_reachable(&self, node: Node) -> bool {
self.immediate_dominators[node].is_some()
}
@ -320,6 +325,8 @@ impl<Node: Idx> Dominators<Node> {
self.immediate_dominators[node].unwrap()
}
/// Provides an iterator over each dominator up the CFG, for the given Node.
/// See the `impl Iterator for Iter` definition to understand how this works.
pub fn dominators(&self, node: Node) -> Iter<'_, Node> {
assert!(self.is_reachable(node), "node {node:?} is not reachable");
Iter { dominators: self, node: Some(node) }