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Auto merge of #127421 - cjgillot:cache-iter, r=fmease

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Cache hir_owner_nodes in ParentHirIterator.

Lint level computation may traverse deep HIR trees using that iterator. This calls `hir_owner_nodes` many times for the same HIR owner, which is wasterful.

This PR caches the value to allow a more efficient iteration scheme.

r? ghost for perf
This commit is contained in:
bors 2024-07-08 01:19:32 +00:00
commit b1de36ff34
1 changed files with 26 additions and 8 deletions
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34
compiler/rustc_middle/src/hir/map/mod.rs
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@ -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<Item = HirId> + '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`