Merge pull request #19991 from Veykril/push-kzqoxzmxqnkl

perf: Bring back `EMPTY` item tree deduplication

Author: Veykril

src/tools/rust-analyzer/crates/hir-def/src/item_tree.rs

@@ -86,9 +86,10 @@ impl fmt::Debug for RawVisibilityId {
  }
 }
 
-#[salsa_macros::tracked(returns(ref))]
-pub(crate) fn file_item_tree_query(db: &dyn DefDatabase, file_id: HirFileId) -> ItemTree {
+#[salsa_macros::tracked(returns(deref))]
+pub(crate) fn file_item_tree_query(db: &dyn DefDatabase, file_id: HirFileId) -> Arc<ItemTree> {
  let _p = tracing::info_span!("file_item_tree_query", ?file_id).entered();
+ static EMPTY: OnceLock<Arc<ItemTree>> = OnceLock::new();
 
  let ctx = lower::Ctx::new(db, file_id);
  let syntax = db.parse_or_expand(file_id);
@@ -116,28 +117,49 @@ pub(crate) fn file_item_tree_query(db: &dyn DefDatabase, file_id: HirFileId) ->
  },
  }
  };
-
- item_tree.shrink_to_fit();
- item_tree
+ let ItemTree { top_level, top_attrs, attrs, vis, big_data, small_data } = &item_tree;
+ if small_data.is_empty()
+ && big_data.is_empty()
+ && top_level.is_empty()
+ && attrs.is_empty()
+ && top_attrs.is_empty()
+ && vis.arena.is_empty()
+ {
+ EMPTY
+ .get_or_init(|| {
+ Arc::new(ItemTree {
+ top_level: Box::new([]),
+ attrs: FxHashMap::default(),
+ small_data: FxHashMap::default(),
+ big_data: FxHashMap::default(),
+ top_attrs: RawAttrs::EMPTY,
+ vis: ItemVisibilities { arena: ThinVec::new() },
+ })
+ })
+ .clone()
+ } else {
+ item_tree.shrink_to_fit();
+ Arc::new(item_tree)
+ }
 }
 
-#[salsa_macros::tracked(returns(ref))]
+#[salsa_macros::tracked(returns(deref))]
 pub(crate) fn block_item_tree_query(db: &dyn DefDatabase, block: BlockId) -> Arc<ItemTree> {
  let _p = tracing::info_span!("block_item_tree_query", ?block).entered();
- // Blocks have a tendency to be empty due to macro calls that do not expand to items,
- // so deduplicate this case via `Arc` to reduce the size of the query storage here.
  static EMPTY: OnceLock<Arc<ItemTree>> = OnceLock::new();
 
  let loc = block.lookup(db);
  let block = loc.ast_id.to_node(db);
 
  let ctx = lower::Ctx::new(db, loc.ast_id.file_id);
  let mut item_tree = ctx.lower_block(&block);
- if item_tree.small_data.is_empty()
- && item_tree.big_data.is_empty()
- && item_tree.top_level.is_empty()
- && item_tree.attrs.is_empty()
- && item_tree.top_attrs.is_empty()
+ let ItemTree { top_level, top_attrs, attrs, vis, big_data, small_data } = &item_tree;
+ if small_data.is_empty()
+ && big_data.is_empty()
+ && top_level.is_empty()
+ && attrs.is_empty()
+ && top_attrs.is_empty()
+ && vis.arena.is_empty()
  {
  EMPTY
  .get_or_init(|| {
@@ -163,7 +185,6 @@ pub struct ItemTree {
  top_attrs: RawAttrs,
  attrs: FxHashMap<FileAstId<ast::Item>, RawAttrs>,
  vis: ItemVisibilities,
- // FIXME: They values store the key, turn this into a FxHashSet<ModItem> instead?
  big_data: FxHashMap<FileAstId<ast::Item>, BigModItem>,
  small_data: FxHashMap<FileAstId<ast::Item>, SmallModItem>,
 }

src/tools/rust-analyzer/crates/hir-def/src/item_tree/lower.rs

@@ -383,8 +383,8 @@ impl<'a> Ctx<'a> {
  });
  match &vis {
  RawVisibility::Public => RawVisibilityId::PUB,
- RawVisibility::Module(path, explicitiy) if path.segments().is_empty() => {
- match (path.kind, explicitiy) {
+ RawVisibility::Module(path, explicitness) if path.segments().is_empty() => {
+ match (path.kind, explicitness) {
  (PathKind::SELF, VisibilityExplicitness::Explicit) => {
  RawVisibilityId::PRIV_EXPLICIT
  }