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Speed up item_bodies for large match statements involving regions #57494

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merged 2 commits into from
Jan 13, 2019
Merged

Speed up item_bodies for large match statements involving regions #57494

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07600c9
Drop "solved" constraints during region expansion
dotdash Jan 9, 2019
5f402b8
Add a fast path for identical regions in lub_concrete_regions
dotdash Jan 10, 2019
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31 changes: 23 additions & 8 deletions src/librustc/infer/lexical_region_resolve/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,7 @@ use rustc_data_structures::graph::implementation::{
Direction, Graph, NodeIndex, INCOMING, OUTGOING,
};
use rustc_data_structures::indexed_vec::{Idx, IndexVec};
use smallvec::SmallVec;
use std::fmt;
use std::u32;
use ty::fold::TypeFoldable;
Expand Down Expand Up @@ -190,19 +191,24 @@ impl<'cx, 'gcx, 'tcx> LexicalResolver<'cx, 'gcx, 'tcx> {
match *constraint {
Constraint::RegSubVar(a_region, b_vid) => {
let b_data = var_values.value_mut(b_vid);
self.expand_node(a_region, b_vid, b_data)
(self.expand_node(a_region, b_vid, b_data), false)
}
Constraint::VarSubVar(a_vid, b_vid) => match *var_values.value(a_vid) {
VarValue::ErrorValue => false,
VarValue::ErrorValue => (false, false),
VarValue::Value(a_region) => {
let b_node = var_values.value_mut(b_vid);
self.expand_node(a_region, b_vid, b_node)
let changed = self.expand_node(a_region, b_vid, b_node);
let retain = match *b_node {
VarValue::Value(ReStatic) | VarValue::ErrorValue => false,
_ => true
};
(changed, retain)
}
},
Constraint::RegSubReg(..) | Constraint::VarSubReg(..) => {
// These constraints are checked after expansion
// is done, in `collect_errors`.
false
(false, false)
}
}
})
Expand Down Expand Up @@ -268,6 +274,13 @@ impl<'cx, 'gcx, 'tcx> LexicalResolver<'cx, 'gcx, 'tcx> {

fn lub_concrete_regions(&self, a: Region<'tcx>, b: Region<'tcx>) -> Region<'tcx> {
let tcx = self.tcx();

// Equal scopes can show up quite often, if the fixed point
// iteration converges slowly, skip them
if a == b {
return a;
}

match (a, b) {
(&ty::ReClosureBound(..), _)
| (_, &ty::ReClosureBound(..))
Expand Down Expand Up @@ -710,21 +723,23 @@ impl<'cx, 'gcx, 'tcx> LexicalResolver<'cx, 'gcx, 'tcx> {

fn iterate_until_fixed_point<F>(&self, tag: &str, mut body: F)
where
F: FnMut(&Constraint<'tcx>, &SubregionOrigin<'tcx>) -> bool,
F: FnMut(&Constraint<'tcx>, &SubregionOrigin<'tcx>) -> (bool, bool),
{
let mut constraints: SmallVec<[_; 16]> = self.data.constraints.iter().collect();
let mut iteration = 0;
let mut changed = true;
while changed {
changed = false;
iteration += 1;
debug!("---- {} Iteration {}{}", "#", tag, iteration);
for (constraint, origin) in &self.data.constraints {
let edge_changed = body(constraint, origin);
constraints.retain(|(constraint, origin)| {
let (edge_changed, retain) = body(constraint, origin);
if edge_changed {
debug!("Updated due to constraint {:?}", constraint);
changed = true;
}
}
retain
});
}
debug!("---- {} Complete after {} iteration(s)", tag, iteration);
}
Expand Down