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Optimize: reuse the real-to-preorder mapping as the visited set

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This commit is contained in:
Mark Rousskov 2021-05-09 12:56:58 -04:00
parent 8991002644
commit 345ada0e1b
1 changed files with 2 additions and 4 deletions
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6
compiler/rustc_data_structures/src/graph/dominators/mod.rs
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@ -19,11 +19,9 @@ struct PreOrderFrame<Node, Iter> {
pub fn dominators<G: ControlFlowGraph>(graph: G) -> Dominators<G::Node> {
// compute the post order index (rank) for each node
let mut post_order_rank = IndexVec::from_elem_n(0, graph.num_nodes());
let mut visited = BitSet::new_empty(graph.num_nodes());
let mut parent: IndexVec<usize, Option<usize>> = IndexVec::from_elem_n(None, graph.num_nodes());
let mut stack = vec![PreOrderFrame { node: 0, iter: graph.successors(graph.start_node()) }];
visited.insert(graph.start_node());
let mut pre_order_to_real = Vec::with_capacity(graph.num_nodes());
let mut real_to_pre_order: IndexVec<G::Node, Option<usize>> =
IndexVec::from_elem_n(None, graph.num_nodes());
@ -34,10 +32,10 @@ pub fn dominators<G: ControlFlowGraph>(graph: G) -> Dominators<G::Node> {
'recurse: while let Some(frame) = stack.last_mut() {
while let Some(successor) = frame.iter.next() {
if visited.insert(successor) {
if real_to_pre_order[successor].is_none() {
real_to_pre_order[successor] = Some(idx);
parent[idx] = Some(frame.node);
pre_order_to_real.push(successor);
real_to_pre_order[successor] = Some(idx);
stack.push(PreOrderFrame { node: idx, iter: graph.successors(successor) });
idx += 1;