diff --git a/compiler/rustc_middle/src/hir/map/mod.rs b/compiler/rustc_middle/src/hir/map/mod.rs index 305ba1ef3bbc8..2f3a6ee601b15 100644 --- a/compiler/rustc_middle/src/hir/map/mod.rs +++ b/compiler/rustc_middle/src/hir/map/mod.rs @@ -31,9 +31,18 @@ pub struct Map<'hir> { /// An iterator that walks up the ancestor tree of a given `HirId`. /// Constructed using `tcx.hir().parent_iter(hir_id)`. -pub struct ParentHirIterator<'hir> { +struct ParentHirIterator<'hir> { current_id: HirId, map: Map<'hir>, + // Cache the current value of `hir_owner_nodes` to avoid repeatedly calling the same query for + // the same owner, which will uselessly record many times the same query dependency. + current_owner_nodes: Option<&'hir OwnerNodes<'hir>>, +} + +impl<'hir> ParentHirIterator<'hir> { + fn new(map: Map<'hir>, current_id: HirId) -> ParentHirIterator<'hir> { + ParentHirIterator { current_id, map, current_owner_nodes: None } + } } impl<'hir> Iterator for ParentHirIterator<'hir> { @@ -44,13 +53,22 @@ impl<'hir> Iterator for ParentHirIterator<'hir> { return None; } - // There are nodes that do not have entries, so we need to skip them. - let parent_id = self.map.tcx.parent_hir_id(self.current_id); + let HirId { owner, local_id } = self.current_id; - if parent_id == self.current_id { - self.current_id = CRATE_HIR_ID; - return None; - } + let parent_id = if local_id == ItemLocalId::ZERO { + // We go from an owner to its parent, so clear the cache. + self.current_owner_nodes = None; + self.map.tcx.hir_owner_parent(owner) + } else { + let owner_nodes = + self.current_owner_nodes.get_or_insert_with(|| self.map.tcx.hir_owner_nodes(owner)); + let parent_local_id = owner_nodes.nodes[local_id].parent; + // HIR indexing should have checked that. + debug_assert_ne!(parent_local_id, local_id); + HirId { owner, local_id: parent_local_id } + }; + + debug_assert_ne!(parent_id, self.current_id); self.current_id = parent_id; return Some(parent_id); @@ -479,7 +497,7 @@ impl<'hir> Map<'hir> { /// until the crate root is reached. Prefer this over your own loop using `parent_id`. #[inline] pub fn parent_id_iter(self, current_id: HirId) -> impl Iterator + 'hir { - ParentHirIterator { current_id, map: self } + ParentHirIterator::new(self, current_id) } /// Returns an iterator for the nodes in the ancestor tree of the `current_id`