9 files changed, 58 insertions, 4 deletions

diff --git a/Cargo.lock b/Cargo.lock
index 71223218d..9f7a1d019 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -274,6 +274,17 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "28b9d6de7f49e22cf97ad17fc4036ece69300032f45f78f30b4a4482cdc3f4a6"
 
 [[package]]
+name = "countme"
+version = "2.0.0-pre.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c5716604cba7c02a846ecad3f4a3fd2d2b641faccc2a24a51efb21aff0d01f35"
+dependencies = [
+ "dashmap",
+ "once_cell",
+ "rustc-hash",
+]
+
+[[package]]
 name = "crc32fast"
 version = "1.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -350,6 +361,16 @@ dependencies = [
 ]
 
 [[package]]
+name = "dashmap"
+version = "4.0.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e77a43b28d0668df09411cb0bc9a8c2adc40f9a048afe863e05fd43251e8e39c"
+dependencies = [
+ "cfg-if 1.0.0",
+ "num_cpus",
+]
+
+[[package]]
 name = "dissimilar"
 version = "1.0.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -1260,6 +1281,7 @@ name = "profile"
 version = "0.0.0"
 dependencies = [
  "cfg-if 1.0.0",
+ "countme",
  "jemalloc-ctl",
  "la-arena",
  "libc",
@@ -1375,10 +1397,11 @@ checksum = "b5eb417147ba9860a96cfe72a0b93bf88fee1744b5636ec99ab20c1aa9376581"
 
 [[package]]
 name = "rowan"
-version = "0.12.0"
+version = "0.12.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "bea4527c692099becd37ec777cfd6949d0534348528d2fc84ee420d2d5fac83d"
+checksum = "24c2d78254049413f9d73495f883e7fa0b7a7d4b88468cd72a3bbbd0ad585cd1"
 dependencies = [
+ "countme",
  "hashbrown",
  "memoffset",
  "rustc-hash",
diff --git a/crates/hir_def/src/item_tree.rs b/crates/hir_def/src/item_tree.rs
index 1226d7d85..b8d7608e7 100644
--- a/crates/hir_def/src/item_tree.rs
+++ b/crates/hir_def/src/item_tree.rs
@@ -21,6 +21,7 @@ use hir_expand::{
     HirFileId, InFile,
 };
 use la_arena::{Arena, Idx, RawIdx};
+use profile::Count;
 use rustc_hash::FxHashMap;
 use smallvec::SmallVec;
 use syntax::{ast, match_ast};
@@ -67,6 +68,8 @@ impl GenericParamsId {
 /// The item tree of a source file.
 #[derive(Debug, Eq, PartialEq)]
 pub struct ItemTree {
+    _c: Count<Self>,
+
     top_level: SmallVec<[ModItem; 1]>,
     attrs: FxHashMap<AttrOwner, RawAttrs>,
 
@@ -116,7 +119,12 @@ impl ItemTree {
     }
 
     fn empty() -> Self {
-        Self { top_level: Default::default(), attrs: Default::default(), data: Default::default() }
+        Self {
+            _c: Count::new(),
+            top_level: Default::default(),
+            attrs: Default::default(),
+            data: Default::default(),
+        }
     }
 
     fn shrink_to_fit(&mut self) {
diff --git a/crates/hir_def/src/nameres.rs b/crates/hir_def/src/nameres.rs
index 93931a21a..bd3ea9b8b 100644
--- a/crates/hir_def/src/nameres.rs
+++ b/crates/hir_def/src/nameres.rs
@@ -59,6 +59,7 @@ use std::sync::Arc;
 use base_db::{CrateId, Edition, FileId};
 use hir_expand::{diagnostics::DiagnosticSink, name::Name, InFile};
 use la_arena::Arena;
+use profile::Count;
 use rustc_hash::FxHashMap;
 use stdx::format_to;
 use syntax::{ast, AstNode};
@@ -75,6 +76,7 @@ use crate::{
 /// Contains all top-level defs from a macro-expanded crate
 #[derive(Debug, PartialEq, Eq)]
 pub struct DefMap {
+    _c: Count<Self>,
     parent: Option<Arc<DefMap>>,
     root: LocalModuleId,
     modules: Arena<ModuleData>,
@@ -215,6 +217,7 @@ impl DefMap {
         let mut modules: Arena<ModuleData> = Arena::default();
         let root = modules.alloc(ModuleData::default());
         DefMap {
+            _c: Count::new(),
             parent: None,
             krate,
             edition,
diff --git a/crates/ide/src/status.rs b/crates/ide/src/status.rs
index e10d7c3a4..137c38c0d 100644
--- a/crates/ide/src/status.rs
+++ b/crates/ide/src/status.rs
@@ -38,6 +38,7 @@ pub(crate) fn status(db: &RootDatabase, file_id: Option<FileId>) -> String {
     format_to!(buf, "{}\n", syntax_tree_stats(db));
     format_to!(buf, "{} (macros)\n", macro_syntax_tree_stats(db));
     format_to!(buf, "{} total\n", memory_usage());
+    format_to!(buf, "\ncounts:\n{}", profile::countme::get_all());
 
     if let Some(file_id) = file_id {
         format_to!(buf, "\nfile info:\n");
@@ -60,6 +61,7 @@ pub(crate) fn status(db: &RootDatabase, file_id: Option<FileId>) -> String {
             None => format_to!(buf, "does not belong to any crate"),
         }
     }
+
     buf
 }
 
diff --git a/crates/profile/Cargo.toml b/crates/profile/Cargo.toml
index f7231c2b8..cc7da27f7 100644
--- a/crates/profile/Cargo.toml
+++ b/crates/profile/Cargo.toml
@@ -14,6 +14,7 @@ once_cell = "1.3.1"
 cfg-if = "1"
 libc = "0.2.73"
 la-arena = { version = "0.2.0", path = "../../lib/arena" }
+countme = { version = "2.0.0-pre.2", features = ["enable"] }
 jemalloc-ctl = { version = "0.3.3", optional = true }
 
 [target.'cfg(target_os = "linux")'.dependencies]
diff --git a/crates/profile/src/hprof.rs b/crates/profile/src/hprof.rs
index 8957ea016..29d2ed518 100644
--- a/crates/profile/src/hprof.rs
+++ b/crates/profile/src/hprof.rs
@@ -3,6 +3,7 @@ use once_cell::sync::Lazy;
 use std::{
     cell::RefCell,
     collections::{BTreeMap, HashSet},
+    env,
     io::{stderr, Write},
     sync::{
         atomic::{AtomicBool, Ordering},
@@ -18,7 +19,8 @@ use crate::tree::{Idx, Tree};
 /// env RA_PROFILE=foo|bar|baz   // enabled only selected entries
 /// env RA_PROFILE=*@3>10        // dump everything, up to depth 3, if it takes more than 10 ms
 pub fn init() {
-    let spec = std::env::var("RA_PROFILE").unwrap_or_default();
+    countme::enable(env::var("RA_COUNT").is_ok());
+    let spec = env::var("RA_PROFILE").unwrap_or_default();
     init_from(&spec);
 }
 
diff --git a/crates/profile/src/lib.rs b/crates/profile/src/lib.rs
index aa6ccc36c..79dba47d5 100644
--- a/crates/profile/src/lib.rs
+++ b/crates/profile/src/lib.rs
@@ -15,6 +15,13 @@ pub use crate::{
     stop_watch::{StopWatch, StopWatchSpan},
 };
 
+pub use countme;
+/// Include `_c: Count<Self>` field in important structs to count them.
+///
+/// To view the counts, run with `RA_COUNT=1`. The overhead of disabled count is
+/// almost zero.
+pub use countme::Count;
+
 thread_local!(static IN_SCOPE: RefCell<bool> = RefCell::new(false));
 
 /// Allows to check if the current code is withing some dynamic scope, can be
diff --git a/crates/rust-analyzer/src/cli/analysis_stats.rs b/crates/rust-analyzer/src/cli/analysis_stats.rs
index fd1407e60..66416f709 100644
--- a/crates/rust-analyzer/src/cli/analysis_stats.rs
+++ b/crates/rust-analyzer/src/cli/analysis_stats.rs
@@ -2,6 +2,7 @@
 //! errors.
 
 use std::{
+    env,
     path::PathBuf,
     time::{SystemTime, UNIX_EPOCH},
 };
@@ -295,6 +296,10 @@ impl AnalysisStatsCmd {
             report_metric("total memory", memory.allocated.megabytes() as u64, "MB");
         }
 
+        if env::var("RA_COUNT").is_ok() {
+            eprintln!("{}", profile::countme::get_all());
+        }
+
         if self.memory_usage && verbosity.is_verbose() {
             print_memory_usage(host, vfs);
         }
diff --git a/docs/dev/README.md b/docs/dev/README.md
index dd2bfc493..24197b332 100644
--- a/docs/dev/README.md
+++ b/docs/dev/README.md
@@ -251,6 +251,9 @@ RA_PROFILE=*@3>10        // dump everything, up to depth 3, if it takes more tha
 
 In particular, I have `export RA_PROFILE='*>10'` in my shell profile.
 
+We also have a "counting" profiler which counts number of instances of popular structs.
+It is enabled by `RA_COUNT=1`.
+
 To measure time for from-scratch analysis, use something like this:
 
 ```