Merge #9206

9206: minor: Speed up fst items lookup during completions r=SomeoneToIgnore a=SomeoneToIgnore

Part of https://github.com/rust-analyzer/rust-analyzer/issues/7542

A number of profile calls added for `import_on_the_fly` contents.
Before:
<img width="606" alt="Screenshot 2021-06-11 at 00 19 13" src="https://user-images.githubusercontent.com/2690773/121598998-22321e80-ca4b-11eb-9a3d-dc9cb2936705.png">

After:
<img width="859" alt="Screenshot 2021-06-11 at 00 19 27" src="https://user-images.githubusercontent.com/2690773/121599022-2a8a5980-ca4b-11eb-82b6-13ab0ed56d58.png">

As a result, low hanging fruit was spotted: crazy amount of `fst_path` calls. Reducing that won ~200ms in the `import_on_the_fly @ sel` case in the `integrated_completion_benchmark`:

<img width="861" alt="Screenshot 2021-06-11 at 00 19 38" src="https://user-images.githubusercontent.com/2690773/121599277-7d641100-ca4b-11eb-8667-53206994de27.png">

I'm not sure how to proceed with the remaining `???` marks in such methods as `collect_import_map` though: there's nothing but library calls in cycles, but maybe I'll come up with something later.

Co-authored-by: Kirill Bulatov <[email protected]>

1 files changed, 1 insertions, 0 deletions

diff --git a/crates/hir_def/src/lang_item.rs b/crates/hir_def/src/lang_item.rs
index 9e90f745c..3a45cbfa1 100644
--- a/crates/hir_def/src/lang_item.rs
+++ b/crates/hir_def/src/lang_item.rs
@@ -141,6 +141,7 @@ impl LangItems {
     ) where
         T: Into<AttrDefId> + Copy,
     {
+        let _p = profile::span("collect_lang_item");
         if let Some(lang_item_name) = lang_attr(db, item) {
             self.items.entry(lang_item_name).or_insert_with(|| constructor(item));
         }