diff options
Diffstat (limited to 'compiler/rustc_data_structures/src/graph/dominators/mod.rs')
| -rw-r--r-- | compiler/rustc_data_structures/src/graph/dominators/mod.rs | 22 |
1 files changed, 10 insertions, 12 deletions
diff --git a/compiler/rustc_data_structures/src/graph/dominators/mod.rs b/compiler/rustc_data_structures/src/graph/dominators/mod.rs index e76bdac2864..a7de709ba72 100644 --- a/compiler/rustc_data_structures/src/graph/dominators/mod.rs +++ b/compiler/rustc_data_structures/src/graph/dominators/mod.rs @@ -242,7 +242,9 @@ pub fn dominators<G: ControlFlowGraph>(graph: G) -> Dominators<G::Node> { immediate_dominators[*node] = Some(pre_order_to_real[idom[idx]]); } - Dominators { post_order_rank, immediate_dominators } + let start_node = graph.start_node(); + immediate_dominators[start_node] = None; + Dominators { start_node, post_order_rank, immediate_dominators } } /// Evaluate the link-eval virtual forest, providing the currently minimum semi @@ -308,6 +310,7 @@ fn compress( /// Tracks the list of dominators for each node. #[derive(Clone, Debug)] pub struct Dominators<N: Idx> { + start_node: N, 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 @@ -316,14 +319,14 @@ pub struct Dominators<N: Idx> { } impl<Node: Idx> Dominators<Node> { - /// Whether the given Node has an immediate dominator. + /// Returns true if node is reachable from the start node. pub fn is_reachable(&self, node: Node) -> bool { - self.immediate_dominators[node].is_some() + node == self.start_node || self.immediate_dominators[node].is_some() } - pub fn immediate_dominator(&self, node: Node) -> Node { - assert!(self.is_reachable(node), "node {node:?} is not reachable"); - self.immediate_dominators[node].unwrap() + /// Returns the immediate dominator of node, if any. + pub fn immediate_dominator(&self, node: Node) -> Option<Node> { + self.immediate_dominators[node] } /// Provides an iterator over each dominator up the CFG, for the given Node. @@ -357,12 +360,7 @@ impl<'dom, Node: Idx> Iterator for Iter<'dom, Node> { fn next(&mut self) -> Option<Self::Item> { if let Some(node) = self.node { - let dom = self.dominators.immediate_dominator(node); - if dom == node { - self.node = None; // reached the root - } else { - self.node = Some(dom); - } + self.node = self.dominators.immediate_dominator(node); Some(node) } else { None |