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Remove some Vec allocations to improve performance #71268

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Merged
bors merged 4 commits into from
Apr 27, 2020
Merged

Remove some Vec allocations to improve performance #71268

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2000f91
Remove some `Vec` allocations in an effort to improve perf
estebank Apr 18, 2020
faeb040
Remove unnecessary allocation
estebank Apr 18, 2020
6c921c2
Use more `Iterator`s instead of `Vec`s
estebank Apr 18, 2020
e7e3001
Remove some allocations in predicate evaluation
estebank Apr 20, 2020
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Remove some allocations in predicate evaluation
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@estebank
estebank committed Apr 20, 2020
commit e7e3001557cc9a2e13bce599e374b474392eb779
7 changes: 3 additions & 4 deletions src/librustc_infer/traits/util.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -149,21 +149,20 @@ impl Elaborator<'tcx> {
// Get predicates declared on the trait.
let predicates = tcx.super_predicates_of(data.def_id());

let obligations = predicates.predicates.iter().map(|(pred, span)| {
let obligations = predicates.predicates.into_iter().map(|(pred, span)| {
predicate_obligation(
pred.subst_supertrait(tcx, &data.to_poly_trait_ref()),
Some(*span),
)
});
debug!("super_predicates: data={:?} predicates={:?}", data, &obligations);
debug!("super_predicates: data={:?}", data);

// Only keep those bounds that we haven't already seen.
// This is necessary to prevent infinite recursion in some
// cases. One common case is when people define
// `trait Sized: Sized { }` rather than `trait Sized { }`.
let visited = &mut self.visited;
let obligations =
obligations.filter(|obligation| visited.insert(&obligation.predicate));
let obligations = obligations.filter(|o| visited.insert(&o.predicate));

self.stack.extend(obligations);
}
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12 changes: 7 additions & 5 deletions src/librustc_trait_selection/traits/auto_trait.rs
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Expand Up @@ -281,7 +281,7 @@ impl AutoTraitFinder<'tcx> {
},
}));

let mut computed_preds: FxHashSet<_> = param_env.caller_bounds.iter().cloned().collect();
let computed_preds = param_env.caller_bounds.iter().cloned();
let mut user_computed_preds: FxHashSet<_> =
user_env.caller_bounds.iter().cloned().collect();

Expand Down Expand Up @@ -358,9 +358,11 @@ impl AutoTraitFinder<'tcx> {
_ => panic!("Unexpected error for '{:?}': {:?}", ty, result),
};

computed_preds.extend(user_computed_preds.iter().cloned());
let normalized_preds =
elaborate_predicates(tcx, computed_preds.iter().cloned()).map(|o| o.predicate);
let normalized_preds = elaborate_predicates(
tcx,
computed_preds.clone().chain(user_computed_preds.iter().cloned()),
)
.map(|o| o.predicate);
new_env =
ty::ParamEnv::new(tcx.mk_predicates(normalized_preds), param_env.reveal, None);
}
Expand Down Expand Up @@ -738,7 +740,7 @@ impl AutoTraitFinder<'tcx> {
if p.ty().skip_binder().has_infer_types() {
if !self.evaluate_nested_obligations(
ty,
v.clone().iter().cloned(),
v.into_iter(),
computed_preds,
fresh_preds,
predicates,
Expand Down