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Optimize try_expand_impl_trait_type #65293

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Merged
merged 2 commits into from
Oct 16, 2019
Merged

Optimize try_expand_impl_trait_type #65293

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fe09bb5
Add expanded type cache to OpaqueTypeExpander
tmandry Oct 10, 2019
802554f
Only expand types that contain projections
tmandry Oct 10, 2019
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21 changes: 17 additions & 4 deletions src/librustc/ty/util.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -697,6 +697,9 @@ impl<'tcx> TyCtxt<'tcx> {
// that type, and when we finish expanding that type we remove the
// its DefId.
seen_opaque_tys: FxHashSet<DefId>,
// Cache of all expansions we've seen so far. This is a critical
// optimization for some large types produced by async fn trees.
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Suggested change
// optimization for some large types produced by async fn trees.
// optimization for some large types produced by `async fn` trees.

expanded_cache: FxHashMap<(DefId, SubstsRef<'tcx>), Ty<'tcx>>,
primary_def_id: DefId,
found_recursion: bool,
tcx: TyCtxt<'tcx>,
Expand All @@ -713,9 +716,16 @@ impl<'tcx> TyCtxt<'tcx> {
}
let substs = substs.fold_with(self);
if self.seen_opaque_tys.insert(def_id) {
let generic_ty = self.tcx.type_of(def_id);
let concrete_ty = generic_ty.subst(self.tcx, substs);
let expanded_ty = self.fold_ty(concrete_ty);
let expanded_ty = match self.expanded_cache.get(&(def_id, substs)) {
Some(expanded_ty) => expanded_ty,
None => {
let generic_ty = self.tcx.type_of(def_id);
let concrete_ty = generic_ty.subst(self.tcx, substs);
let expanded_ty = self.fold_ty(concrete_ty);
self.expanded_cache.insert((def_id, substs), expanded_ty);
expanded_ty
}
};
self.seen_opaque_tys.remove(&def_id);
Some(expanded_ty)
} else {
Expand All @@ -735,14 +745,17 @@ impl<'tcx> TyCtxt<'tcx> {
fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
if let ty::Opaque(def_id, substs) = t.kind {
self.expand_opaque_ty(def_id, substs).unwrap_or(t)
} else {
} else if t.has_projections() {
t.super_fold_with(self)
} else {
t
}
}
}

let mut visitor = OpaqueTypeExpander {
seen_opaque_tys: FxHashSet::default(),
expanded_cache: FxHashMap::default(),
primary_def_id: def_id,
found_recursion: false,
tcx: self,
Expand Down