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perf: Filter out and process fixed constraints first in region expansion

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Should reduce the number of elements as well as branches in the
extremely hot loop and process_constraint in benchmarks such as
unicode_normalization
This commit is contained in:
Markus Westerlind 2020-01-07 21:45:49 +01:00 • committed by Markus Westerlind
parent 9fe05e9456
commit 343eee6082
1 changed files with 33 additions and 16 deletions
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49
src/librustc/infer/lexical_region_resolve/mod.rs
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@ -295,30 +295,49 @@ impl<'cx, 'tcx> LexicalResolver<'cx, 'tcx> {
}
fn expansion(&self, var_values: &mut LexicalRegionResolutions<'tcx>) {
let mut process_constraint = |constraint: &Constraint<'tcx>| {
let (a_region, b_vid, b_data, retain) = match *constraint {
let mut changed = false;
let mut constraints = Vec::new();
for constraint in self.data.constraints.keys() {
let (a_region, b_vid, b_data) = match *constraint {
Constraint::RegSubVar(a_region, b_vid) => {
let b_data = var_values.value_mut(b_vid);
(a_region, b_vid, b_data, false)
(a_region, b_vid, b_data)
}
Constraint::VarSubVar(a_vid, b_vid) => match *var_values.value(a_vid) {
VarValue::ErrorValue => return (false, false),
VarValue::ErrorValue => continue,
VarValue::Value(a_region) => {
let b_data = var_values.value_mut(b_vid);
let retain = match *b_data {
VarValue::Value(ReStatic) | VarValue::ErrorValue => false,
_ => true,
};
(a_region, b_vid, b_data, retain)
match *b_data {
VarValue::Value(ReStatic) | VarValue::ErrorValue => (),
_ => constraints.push((a_vid, b_vid)),
}
(a_region, b_vid, b_data)
}
},
Constraint::RegSubReg(..) | Constraint::VarSubReg(..) => {
// These constraints are checked after expansion
// is done, in `collect_errors`.
return (false, false);
continue;
}
};
let edge_changed = self.expand_node(a_region, b_vid, b_data);
if edge_changed {
changed = true
}
}
let mut process_constraint = |a_vid, b_vid| {
let (a_region, b_data, retain) = match *var_values.value(a_vid) {
VarValue::ErrorValue => return (false, false),
VarValue::Value(a_region) => {
let b_data = var_values.value_mut(b_vid);
let retain = match *b_data {
VarValue::Value(ReStatic) | VarValue::ErrorValue => false,
_ => true,
};
(a_region, b_data, retain)
}
};
let changed = self.expand_node(a_region, b_vid, b_data);
(changed, retain)
};
@ -326,15 +345,13 @@ impl<'cx, 'tcx> LexicalResolver<'cx, 'tcx> {
// Using bitsets to track the remaining elements is faster than using a
// `Vec` by itself (which requires removing elements, which requires
// element shuffling, which is slow).
let constraints: Vec<_> = self.data.constraints.keys().collect();
let mut live_indices: BitSet<usize> = BitSet::new_filled(constraints.len());
let mut killed_indices: BitSet<usize> = BitSet::new_empty(constraints.len());
let mut changed = true;
while changed {
changed = false;
for index in live_indices.iter() {
let constraint = constraints[index];
let (edge_changed, retain) = process_constraint(constraint);
let (a_vid, b_vid) = constraints[index];
let (edge_changed, retain) = process_constraint(a_vid, b_vid);
changed |= edge_changed;
if !retain {
let changed = killed_indices.insert(index);
@ -790,8 +807,8 @@ impl<'cx, 'tcx> LexicalResolver<'cx, 'tcx> {
self.var_infos[node_idx].origin.span(),
&format!(
"collect_error_for_expanding_node() could not find \
error for var {:?} in universe {:?}, lower_bounds={:#?}, \
upper_bounds={:#?}",
error for var {:?} in universe {:?}, lower_bounds={:#?}, \
upper_bounds={:#?}",
node_idx, node_universe, lower_bounds, upper_bounds
),
);