Auto merge of #78489 - bugadani:array, r=estebank

Minor cleanup around incremental compilation

* Remove some short lived vectors
* Fix some typos
* Avoid some reallocations

5 files changed, 39 insertions, 44 deletions

diff --git a/compiler/rustc_graphviz/src/lib.rs b/compiler/rustc_graphviz/src/lib.rs
index 76e33bed97f..d332466160c 100644
--- a/compiler/rustc_graphviz/src/lib.rs
+++ b/compiler/rustc_graphviz/src/lib.rs
@@ -653,13 +653,13 @@ where
         writeln!(w, r#"    edge[{}];"#, content_attrs_str)?;
     }
 
+    let mut text = Vec::new();
     for n in g.nodes().iter() {
         write!(w, "    ")?;
         let id = g.node_id(n);
 
         let escaped = &g.node_label(n).to_dot_string();
 
-        let mut text = Vec::new();
         write!(text, "{}", id.as_slice()).unwrap();
 
         if !options.contains(&RenderOption::NoNodeLabels) {
@@ -677,6 +677,8 @@ where
 
         writeln!(text, ";").unwrap();
         w.write_all(&text[..])?;
+
+        text.clear();
     }
 
     for e in g.edges().iter() {
@@ -687,7 +689,6 @@ where
         let source_id = g.node_id(&source);
         let target_id = g.node_id(&target);
 
-        let mut text = Vec::new();
         write!(text, "{} -> {}", source_id.as_slice(), target_id.as_slice()).unwrap();
 
         if !options.contains(&RenderOption::NoEdgeLabels) {
@@ -701,6 +702,8 @@ where
 
         writeln!(text, ";").unwrap();
         w.write_all(&text[..])?;
+
+        text.clear();
     }
 
     writeln!(w, "}}")
diff --git a/compiler/rustc_incremental/src/assert_module_sources.rs b/compiler/rustc_incremental/src/assert_module_sources.rs
index 80448c01a26..17d8ac9c882 100644
--- a/compiler/rustc_incremental/src/assert_module_sources.rs
+++ b/compiler/rustc_incremental/src/assert_module_sources.rs
@@ -111,10 +111,12 @@ impl AssertModuleSource<'tcx> {
             (&user_path[..], None)
         };
 
-        let mut cgu_path_components = user_path.split('-').collect::<Vec<_>>();
+        let mut iter = user_path.split('-');
 
         // Remove the crate name
-        assert_eq!(cgu_path_components.remove(0), crate_name);
+        assert_eq!(iter.next().unwrap(), crate_name);
+
+        let cgu_path_components = iter.collect::<Vec<_>>();
 
         let cgu_name_builder = &mut CodegenUnitNameBuilder::new(self.tcx);
         let cgu_name =
diff --git a/compiler/rustc_incremental/src/persist/dirty_clean.rs b/compiler/rustc_incremental/src/persist/dirty_clean.rs
index f0a10885550..d55813f4cc5 100644
--- a/compiler/rustc_incremental/src/persist/dirty_clean.rs
+++ b/compiler/rustc_incremental/src/persist/dirty_clean.rs
@@ -160,7 +160,7 @@ pub fn check_dirty_clean_annotations(tcx: TyCtxt<'_>) {
 
         let mut all_attrs = FindAllAttrs {
             tcx,
-            attr_names: vec![sym::rustc_dirty, sym::rustc_clean],
+            attr_names: &[sym::rustc_dirty, sym::rustc_clean],
             found_attrs: vec![],
         };
         intravisit::walk_crate(&mut all_attrs, krate);
@@ -299,7 +299,7 @@ impl DirtyCleanVisitor<'tcx> {
 
                     // Represents a Trait Declaration
                     // FIXME(michaelwoerister): trait declaration is buggy because sometimes some of
-                    // the depnodes don't exist (because they legitametely didn't need to be
+                    // the depnodes don't exist (because they legitimately didn't need to be
                     // calculated)
                     //
                     // michaelwoerister and vitiral came up with a possible solution,
@@ -512,17 +512,17 @@ fn expect_associated_value(tcx: TyCtxt<'_>, item: &NestedMetaItem) -> Symbol {
 }
 
 // A visitor that collects all #[rustc_dirty]/#[rustc_clean] attributes from
-// the HIR. It is used to verfiy that we really ran checks for all annotated
+// the HIR. It is used to verify that we really ran checks for all annotated
 // nodes.
-pub struct FindAllAttrs<'tcx> {
+pub struct FindAllAttrs<'a, 'tcx> {
     tcx: TyCtxt<'tcx>,
-    attr_names: Vec<Symbol>,
+    attr_names: &'a [Symbol],
     found_attrs: Vec<&'tcx Attribute>,
 }
 
-impl FindAllAttrs<'tcx> {
+impl FindAllAttrs<'_, 'tcx> {
     fn is_active_attr(&mut self, attr: &Attribute) -> bool {
-        for attr_name in &self.attr_names {
+        for attr_name in self.attr_names {
             if self.tcx.sess.check_name(attr, *attr_name) && check_config(self.tcx, attr) {
                 return true;
             }
@@ -543,7 +543,7 @@ impl FindAllAttrs<'tcx> {
     }
 }
 
-impl intravisit::Visitor<'tcx> for FindAllAttrs<'tcx> {
+impl intravisit::Visitor<'tcx> for FindAllAttrs<'_, 'tcx> {
     type Map = Map<'tcx>;
 
     fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<Self::Map> {
diff --git a/compiler/rustc_incremental/src/persist/fs.rs b/compiler/rustc_incremental/src/persist/fs.rs
index 4926f726f35..9fdf0a56d9d 100644
--- a/compiler/rustc_incremental/src/persist/fs.rs
+++ b/compiler/rustc_incremental/src/persist/fs.rs
@@ -765,7 +765,6 @@ pub fn garbage_collect_session_directories(sess: &Session) -> io::Result<()> {
 
     // Now garbage collect the valid session directories.
     let mut deletion_candidates = vec![];
-    let mut definitely_delete = vec![];
 
     for (lock_file_name, directory_name) in &lock_file_to_session_dir {
         debug!("garbage_collect_session_directories() - inspecting: {}", directory_name);
@@ -842,8 +841,11 @@ pub fn garbage_collect_session_directories(sess: &Session) -> io::Result<()> {
                             successfully acquired lock"
                     );
 
-                    // Note that we are holding on to the lock
-                    definitely_delete.push((crate_directory.join(directory_name), Some(lock)));
+                    delete_old(sess, &crate_directory.join(directory_name));
+
+                    // Let's make it explicit that the file lock is released at this point,
+                    // or rather, that we held on to it until here
+                    mem::drop(lock);
                 }
                 Err(_) => {
                     debug!(
@@ -880,26 +882,21 @@ pub fn garbage_collect_session_directories(sess: &Session) -> io::Result<()> {
         mem::drop(lock);
     }
 
-    for (path, lock) in definitely_delete {
-        debug!("garbage_collect_session_directories() - deleting `{}`", path.display());
+    Ok(())
+}
 
-        if let Err(err) = safe_remove_dir_all(&path) {
-            sess.warn(&format!(
-                "Failed to garbage collect incremental \
-                                compilation session directory `{}`: {}",
-                path.display(),
-                err
-            ));
-        } else {
-            delete_session_dir_lock_file(sess, &lock_file_path(&path));
-        }
+fn delete_old(sess: &Session, path: &Path) {
+    debug!("garbage_collect_session_directories() - deleting `{}`", path.display());
 
-        // Let's make it explicit that the file lock is released at this point,
-        // or rather, that we held on to it until here
-        mem::drop(lock);
+    if let Err(err) = safe_remove_dir_all(&path) {
+        sess.warn(&format!(
+            "Failed to garbage collect incremental compilation session directory `{}`: {}",
+            path.display(),
+            err
+        ));
+    } else {
+        delete_session_dir_lock_file(sess, &lock_file_path(&path));
     }
-
-    Ok(())
 }
 
 fn all_except_most_recent(
diff --git a/compiler/rustc_incremental/src/persist/save.rs b/compiler/rustc_incremental/src/persist/save.rs
index c43d4ad4049..45cef479a4f 100644
--- a/compiler/rustc_incremental/src/persist/save.rs
+++ b/compiler/rustc_incremental/src/persist/save.rs
@@ -153,7 +153,8 @@ fn encode_dep_graph(tcx: TyCtxt<'_>, encoder: &mut Encoder) {
         let total_node_count = serialized_graph.nodes.len();
         let total_edge_count = serialized_graph.edge_list_data.len();
 
-        let mut counts: FxHashMap<_, Stat> = FxHashMap::default();
+        let mut counts: FxHashMap<_, Stat> =
+            FxHashMap::with_capacity_and_hasher(total_node_count, Default::default());
 
         for (i, &node) in serialized_graph.nodes.iter_enumerated() {
             let stat = counts.entry(node.kind).or_insert(Stat {
@@ -170,14 +171,6 @@ fn encode_dep_graph(tcx: TyCtxt<'_>, encoder: &mut Encoder) {
         let mut counts: Vec<_> = counts.values().cloned().collect();
         counts.sort_by_key(|s| -(s.node_counter as i64));
 
-        let percentage_of_all_nodes: Vec<f64> = counts
-            .iter()
-            .map(|s| (100.0 * (s.node_counter as f64)) / (total_node_count as f64))
-            .collect();
-
-        let average_edges_per_kind: Vec<f64> =
-            counts.iter().map(|s| (s.edge_counter as f64) / (s.node_counter as f64)).collect();
-
         println!("[incremental]");
         println!("[incremental] DepGraph Statistics");
 
@@ -207,13 +200,13 @@ fn encode_dep_graph(tcx: TyCtxt<'_>, encoder: &mut Encoder) {
                   |------------------|"
         );
 
-        for (i, stat) in counts.iter().enumerate() {
+        for stat in counts.iter() {
             println!(
                 "[incremental]  {:<36}|{:>16.1}% |{:>12} |{:>17.1} |",
                 format!("{:?}", stat.kind),
-                percentage_of_all_nodes[i],
+                (100.0 * (stat.node_counter as f64)) / (total_node_count as f64), // percentage of all nodes
                 stat.node_counter,
-                average_edges_per_kind[i]
+                (stat.edge_counter as f64) / (stat.node_counter as f64), // average edges per kind
             );
         }