bjoernager/rust
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Use variables rather than lengths directly

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This commit is contained in:
Mark Rousskov 2021-05-09 18:59:52 -04:00
parent 345ada0e1b
commit cc63ec32fb
1 changed files with 14 additions and 11 deletions
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25
compiler/rustc_data_structures/src/graph/dominators/mod.rs
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@ -27,18 +27,19 @@ pub fn dominators<G: ControlFlowGraph>(graph: G) -> Dominators<G::Node> {
IndexVec::from_elem_n(None, graph.num_nodes()); IndexVec::from_elem_n(None, graph.num_nodes());
pre_order_to_real.push(graph.start_node()); pre_order_to_real.push(graph.start_node());
real_to_pre_order[graph.start_node()] = Some(0); real_to_pre_order[graph.start_node()] = Some(0);
let mut idx = 1;
let mut post_order_idx = 0; let mut post_order_idx = 0;
'recurse: while let Some(frame) = stack.last_mut() { 'recurse: while let Some(frame) = stack.last_mut() {
while let Some(successor) = frame.iter.next() { while let Some(successor) = frame.iter.next() {
if real_to_pre_order[successor].is_none() { if real_to_pre_order[successor].is_none() {
real_to_pre_order[successor] = Some(idx); let pre_order_idx = pre_order_to_real.len();
parent[idx] = Some(frame.node);
pre_order_to_real.push(successor); real_to_pre_order[successor] = Some(pre_order_idx);
parent[pre_order_idx] = Some(frame.node);
pre_order_to_real.push(successor);
stack
.push(PreOrderFrame { node: pre_order_idx, iter: graph.successors(successor) });
stack.push(PreOrderFrame { node: idx, iter: graph.successors(successor) });
idx += 1;
continue 'recurse; continue 'recurse;
} }
} }
@ -48,13 +49,15 @@ pub fn dominators<G: ControlFlowGraph>(graph: G) -> Dominators<G::Node> {
stack.pop(); stack.pop();
} }
let mut idom = IndexVec::from_elem_n(0, pre_order_to_real.len()); let reachable_vertices = pre_order_to_real.len();
let mut semi = IndexVec::from_fn_n(std::convert::identity, pre_order_to_real.len());
let mut idom = IndexVec::from_elem_n(0, reachable_vertices);
let mut semi = IndexVec::from_fn_n(std::convert::identity, reachable_vertices);
let mut label = semi.clone(); let mut label = semi.clone();
let mut bucket = IndexVec::from_elem_n(vec![], pre_order_to_real.len()); let mut bucket = IndexVec::from_elem_n(vec![], reachable_vertices);
let mut lastlinked = None; let mut lastlinked = None;
for w in (1..pre_order_to_real.len()).rev() { for w in (1..reachable_vertices).rev() {
// Optimization: process buckets just once, at the start of the // Optimization: process buckets just once, at the start of the
// iteration. Do not explicitly empty the bucket (even though it will // iteration. Do not explicitly empty the bucket (even though it will
// not be used again), to save some instructions. // not be used again), to save some instructions.
@ -84,7 +87,7 @@ pub fn dominators<G: ControlFlowGraph>(graph: G) -> Dominators<G::Node> {
// processed elements; lastlinked represents the divider. // processed elements; lastlinked represents the divider.
lastlinked = Some(w); lastlinked = Some(w);
} }
for w in 1..pre_order_to_real.len() { for w in 1..reachable_vertices {
if idom[w] != semi[w] { if idom[w] != semi[w] {
idom[w] = idom[idom[w]]; idom[w] = idom[idom[w]];
} }