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Track changed bitsets in CFG propagation

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This reduces the amount of work done, especially in later iterations,
by only processing nodes whose predecessors changed in the previous
iteration, or earlier in the current iteration. This also has the side
effect of completely ignoring all unreachable nodes.
This commit is contained in:
Eric Holk 2021-12-16 17:15:35 -08:00
parent 7d11b336f3
commit f730bd0dad
1 changed files with 26 additions and 3 deletions
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29
compiler/rustc_typeck/src/check/generator_interior/drop_ranges/cfg_propagate.rs
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@ -10,10 +10,28 @@ impl DropRangesBuilder {
trace!("predecessors: {:#?}", preds.iter_enumerated().collect::<BTreeMap<_, _>>());
let mut new_state = BitSet::new_empty(self.num_values());
let mut changed_nodes = BitSet::new_empty(self.nodes.len());
let mut unchanged_mask = BitSet::new_filled(self.nodes.len());
changed_nodes.insert(0u32.into());
let mut propagate = || {
let mut changed = false;
unchanged_mask.insert_all();
for id in self.nodes.indices() {
trace!("processing {:?}, changed_nodes: {:?}", id, changed_nodes);
// Check if any predecessor has changed, and if not then short-circuit.
//
// We handle the start node specially, since it doesn't have any predecessors,
// but we need to start somewhere.
if match id.index() {
0 => !changed_nodes.contains(id),
_ => !preds[id].iter().any(|pred| changed_nodes.contains(*pred)),
} {
trace!("short-circuiting because none of {:?} have changed", preds[id]);
unchanged_mask.remove(id);
continue;
}
if id.index() == 0 {
new_state.clear();
} else {
@ -23,8 +41,7 @@ impl DropRangesBuilder {
};
for pred in &preds[id] {
let state = &self.nodes[*pred].drop_state;
new_state.intersect(state);
new_state.intersect(&self.nodes[*pred].drop_state);
}
for drop in &self.nodes[id].drops {
@ -35,9 +52,15 @@ impl DropRangesBuilder {
new_state.remove(*reinit);
}
changed |= self.nodes[id].drop_state.intersect(&new_state);
if self.nodes[id].drop_state.intersect(&new_state) {
changed_nodes.insert(id);
changed = true;
} else {
unchanged_mask.remove(id);
}
}
changed_nodes.intersect(&unchanged_mask);
changed
};