From fe09bb518d9dfb270a6f3562b50b96272524b42c Mon Sep 17 00:00:00 2001 From: Tyler Mandry Date: Thu, 10 Oct 2019 16:38:05 -0700 Subject: [PATCH] Add expanded type cache to OpaqueTypeExpander --- src/librustc/ty/util.rs | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-) diff --git a/src/librustc/ty/util.rs b/src/librustc/ty/util.rs index d0e95a18c59fc..35bd42fd74432 100644 --- a/src/librustc/ty/util.rs +++ b/src/librustc/ty/util.rs @@ -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, + // Cache of all expansions we've seen so far. This is a critical + // 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>, @@ -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 { @@ -743,6 +753,7 @@ impl<'tcx> TyCtxt<'tcx> { let mut visitor = OpaqueTypeExpander { seen_opaque_tys: FxHashSet::default(), + expanded_cache: FxHashMap::default(), primary_def_id: def_id, found_recursion: false, tcx: self,