Merge #4489

4489: Memory allocation optimization r=matklad a=simonvandel

I did some profiling using DHAT, and this was what I could easily optimize without much knowledge of the codebase.

This speeds up analysis-stats on rust-analyser by ~4% on my local machine.

**Benchmark**
➜  rust-analyzer-base git:(master) hyperfine --min-runs=2 '/home/simon/Documents/rust-analyzer/target/release/rust-analyzer analysis-stats .' '/home/simon/Documents/rust-analyzer-base/target/release/rust-analyzer analysis-stats .'
Benchmark #1: /home/simon/Documents/rust-analyzer/target/release/rust-analyzer analysis-stats .
  Time (mean ± σ):     49.621 s ±  0.317 s    [User: 48.725 s, System: 0.792 s]
  Range (min … max):   49.397 s … 49.846 s    2 runs

Benchmark #2: /home/simon/Documents/rust-analyzer-base/target/release/rust-analyzer analysis-stats .
  Time (mean ± σ):     51.764 s ±  0.045 s    [User: 50.882 s, System: 0.756 s]
  Range (min … max):   51.733 s … 51.796 s    2 runs

Summary
  '/home/simon/Documents/rust-analyzer/target/release/rust-analyzer analysis-stats .' ran
    1.04 ± 0.01 times faster than '/home/simon/Documents/rust-analyzer-base/target/release/rust-analyzer analysis-stats .'

Co-authored-by: Simon Vandel Sillesen <simon.vandel@gmail.com>

diff --git a/crates/ra_mbe/src/mbe_expander/transcriber.rs b/crates/ra_mbe/src/mbe_expander/transcriber.rs
index 4b173edd3f9103b6eb7b84d474d51884d97cb25b..7c9bb4d00e1a2f5f4d036eaa53393c8a5b77a7a9 100644 (file)
--- a/crates/ra_mbe/src/mbe_expander/transcriber.rs
+++ b/crates/ra_mbe/src/mbe_expander/transcriber.rs
@@ -1,4 +1,4 @@
-//! Transcraber takes a template, like `fn $ident() {}`, a set of bindings like
+//! Transcriber takes a template, like `fn $ident() {}`, a set of bindings like
 //! `$ident => foo`, interpolates variables in the template, to get `fn foo() {}`
 
 use ra_syntax::SmolStr;
@@ -53,7 +53,8 @@ fn get(&self, name: &str, nesting: &mut [NestingState]) -> Result<&Fragment, Exp
 pub(super) fn transcribe(template: &tt::Subtree, bindings: &Bindings) -> ExpandResult<tt::Subtree> {
     assert!(template.delimiter == None);
     let mut ctx = ExpandCtx { bindings: &bindings, nesting: Vec::new() };
-    expand_subtree(&mut ctx, template)
+    let mut arena: Vec<tt::TokenTree> = Vec::new();
+    expand_subtree(&mut ctx, template, &mut arena)
 }
 
 #[derive(Debug)]
@@ -73,8 +74,13 @@ struct ExpandCtx<'a> {
     nesting: Vec<NestingState>,
 }
 
-fn expand_subtree(ctx: &mut ExpandCtx, template: &tt::Subtree) -> ExpandResult<tt::Subtree> {
-    let mut buf: Vec<tt::TokenTree> = Vec::new();
+fn expand_subtree(
+    ctx: &mut ExpandCtx,
+    template: &tt::Subtree,
+    arena: &mut Vec<tt::TokenTree>,
+) -> ExpandResult<tt::Subtree> {
+    // remember how many elements are in the arena now - when returning, we want to drain exactly how many elements we added. This way, the recursive uses of the arena get their own "view" of the arena, but will reuse the allocation
+    let start_elements = arena.len();
     let mut err = None;
     for op in parse_template(template) {
         let op = match op {
@@ -85,25 +91,27 @@ fn expand_subtree(ctx: &mut ExpandCtx, template: &tt::Subtree) -> ExpandResult<t
             }
         };
         match op {
-            Op::TokenTree(tt @ tt::TokenTree::Leaf(..)) => buf.push(tt.clone()),
+            Op::TokenTree(tt @ tt::TokenTree::Leaf(..)) => arena.push(tt.clone()),
             Op::TokenTree(tt::TokenTree::Subtree(tt)) => {
-                let ExpandResult(tt, e) = expand_subtree(ctx, tt);
+                let ExpandResult(tt, e) = expand_subtree(ctx, tt, arena);
                 err = err.or(e);
-                buf.push(tt.into());
+                arena.push(tt.into());
             }
             Op::Var { name, kind: _ } => {
                 let ExpandResult(fragment, e) = expand_var(ctx, name);
                 err = err.or(e);
-                push_fragment(&mut buf, fragment);
+                push_fragment(arena, fragment);
             }
             Op::Repeat { subtree, kind, separator } => {
-                let ExpandResult(fragment, e) = expand_repeat(ctx, subtree, kind, separator);
+                let ExpandResult(fragment, e) = expand_repeat(ctx, subtree, kind, separator, arena);
                 err = err.or(e);
-                push_fragment(&mut buf, fragment)
+                push_fragment(arena, fragment)
             }
         }
     }
-    ExpandResult(tt::Subtree { delimiter: template.delimiter, token_trees: buf }, err)
+    // drain the elements added in this instance of expand_subtree
+    let tts = arena.drain(start_elements..arena.len()).collect();
+    ExpandResult(tt::Subtree { delimiter: template.delimiter, token_trees: tts }, err)
 }
 
 fn expand_var(ctx: &mut ExpandCtx, v: &SmolStr) -> ExpandResult<Fragment> {
@@ -155,6 +163,7 @@ fn expand_repeat(
     template: &tt::Subtree,
     kind: RepeatKind,
     separator: Option<Separator>,
+    arena: &mut Vec<tt::TokenTree>,
 ) -> ExpandResult<Fragment> {
     let mut buf: Vec<tt::TokenTree> = Vec::new();
     ctx.nesting.push(NestingState { idx: 0, at_end: false, hit: false });
@@ -165,7 +174,7 @@ fn expand_repeat(
     let mut counter = 0;
 
     loop {
-        let ExpandResult(mut t, e) = expand_subtree(ctx, template);
+        let ExpandResult(mut t, e) = expand_subtree(ctx, template, arena);
         let nesting_state = ctx.nesting.last_mut().unwrap();
         if nesting_state.at_end || !nesting_state.hit {
             break;

diff --git a/crates/ra_parser/src/lib.rs b/crates/ra_parser/src/lib.rs
index e08ad4dae673c05849be77039389f62f0c3a6d6a..eeb8ad66bd16b3df4339141b111cbf12c094f47a 100644 (file)
--- a/crates/ra_parser/src/lib.rs
+++ b/crates/ra_parser/src/lib.rs
@@ -25,7 +25,7 @@
 pub use syntax_kind::SyntaxKind;
 
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
-pub struct ParseError(pub String);
+pub struct ParseError(pub Box<String>);
 
 /// `TokenSource` abstracts the source of the tokens parser operates on.
 ///

diff --git a/crates/ra_parser/src/parser.rs b/crates/ra_parser/src/parser.rs
index faa63d53f2c221293ea080198b88e1992b2a01d1..4f59b0a2356fe7a6ee33b7143e703176e1e93be2 100644 (file)
--- a/crates/ra_parser/src/parser.rs
+++ b/crates/ra_parser/src/parser.rs
@@ -192,7 +192,7 @@ pub(crate) fn bump_remap(&mut self, kind: SyntaxKind) {
     /// structured errors with spans and notes, like rustc
     /// does.
     pub(crate) fn error<T: Into<String>>(&mut self, message: T) {
-        let msg = ParseError(message.into());
+        let msg = ParseError(Box::new(message.into()));
         self.push_event(Event::Error { msg })
     }
 

diff --git a/crates/ra_syntax/src/syntax_node.rs b/crates/ra_syntax/src/syntax_node.rs
index f9d379abf3c1eddab868a5912f08c065538734b9..e566af7e87acc2271a192c8d50b0ee0413817cad 100644 (file)
--- a/crates/ra_syntax/src/syntax_node.rs
+++ b/crates/ra_syntax/src/syntax_node.rs
@@ -70,6 +70,6 @@ pub fn finish_node(&mut self) {
     }
 
     pub fn error(&mut self, error: ra_parser::ParseError, text_pos: TextSize) {
-        self.errors.push(SyntaxError::new_at_offset(error.0, text_pos))
+        self.errors.push(SyntaxError::new_at_offset(*error.0, text_pos))
     }
 }

diff --git a/crates/ra_tt/src/buffer.rs b/crates/ra_tt/src/buffer.rs
index 14b3f707df3b612df2539558f823c329beedddf7..5967f44cd08def64eb740335f25a67f9e049985b 100644 (file)
--- a/crates/ra_tt/src/buffer.rs
+++ b/crates/ra_tt/src/buffer.rs
@@ -42,7 +42,9 @@ fn new_inner(
         buffers: &mut Vec<Box<[Entry<'t>]>>,
         next: Option<EntryPtr>,
     ) -> usize {
-        let mut entries = vec![];
+        // Must contain everything in tokens and then the Entry::End
+        let start_capacity = tokens.len() + 1;
+        let mut entries = Vec::with_capacity(start_capacity);
         let mut children = vec![];
 
         for (idx, tt) in tokens.iter().enumerate() {