From b3390aeea68a59e65226d7df878af0ab0626e96d Mon Sep 17 00:00:00 2001
From: Domenic Quirl <DomenicQuirl@pm.me>
Date: Wed, 23 Jun 2021 13:42:49 +0200
Subject: [PATCH] speed up green node building by removing copies

---
 Cargo.toml           | 36 +++++++++++++++++++++---------------
 src/green/builder.rs | 40 ++++++++++++++++++++++++----------------
 src/green/node.rs    | 26 +++-----------------------
 3 files changed, 48 insertions(+), 54 deletions(-)

diff --git a/Cargo.toml b/Cargo.toml
index 6b82fef..736c570 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,32 +1,38 @@
 [package]
-edition = "2018"
-name = "cstree"
-version = "0.4.0"
-authors = ["Domenic Quirl <DomenicQuirl@pm.me>", "Aleksey Kladov <aleksey.kladov@gmail.com>"]
+edition   = "2018"
+name      = "cstree"
+version   = "0.4.0"
+authors   = [
+    "Domenic Quirl <DomenicQuirl@pm.me>",
+    "Aleksey Kladov <aleksey.kladov@gmail.com>",
+]
 description = "Library for generic lossless syntax trees"
-license = "MIT OR Apache-2.0"
+license   = "MIT OR Apache-2.0"
 repository = "https://github.com/domenicquirl/cstree"
-readme = "README.md"
+readme    = "README.md"
+
+[profile.release]
+debug = true
 
 [dependencies]
-lasso = "0.5"
+lasso     = { version="0.5", features=["inline-more"] }
 text-size = "1.0.0"
-fxhash= "0.2.1"
-parking_lot= "0.11.1"
+fxhash    = "0.2.1"
+parking_lot = "0.11.1"
 
 # Arc
 triomphe = "0.1.2"
 
 [dependencies.serde]
-version = "1.0"
-optional = true
+version        = "1.0"
+optional       = true
 default-features = false
-features = ["derive"]
+features       = ["derive"]
 
 [dev-dependencies]
-m_lexer = "0.0.4"
-serde_json = "1.0.61"
-serde_test = "1.0.119"
+m_lexer       = "0.0.4"
+serde_json    = "1.0.61"
+serde_test    = "1.0.119"
 crossbeam-utils = "0.8"
 
 [features]
diff --git a/src/green/builder.rs b/src/green/builder.rs
index 973c3d4..a5d753a 100644
--- a/src/green/builder.rs
+++ b/src/green/builder.rs
@@ -1,6 +1,9 @@
-use std::convert::TryFrom;
+use std::{
+    convert::TryFrom,
+    hash::{Hash, Hasher},
+};
 
-use fxhash::FxHashMap;
+use fxhash::{FxHashMap, FxHasher32};
 use text_size::TextSize;
 
 use crate::{
@@ -132,11 +135,11 @@ where
         }
 
         impl ChildrenIter {
-            fn new(data: [Option<GreenElement>; CHILDREN_CACHE_THRESHOLD], count: usize) -> Self {
+            fn new() -> Self {
                 ChildrenIter {
-                    data,
-                    idx: 0,
-                    len: count,
+                    data: [None, None, None],
+                    idx:  0,
+                    len:  0,
                 }
             }
         }
@@ -157,19 +160,24 @@ where
             }
         }
 
-        let mut data: [Option<GreenElement>; CHILDREN_CACHE_THRESHOLD] = [None, None, None];
-        let mut count = 0;
-
-        for child in children {
-            data[count] = Some(child);
-            count += 1;
+        let mut new_children = ChildrenIter::new();
+        let mut hasher = FxHasher32::default();
+        let mut text_len: TextSize = 0.into();
+        for (i, child) in children.into_iter().enumerate() {
+            text_len += child.text_len();
+            child.hash(&mut hasher);
+            new_children.data[i] = Some(child);
+            new_children.len += 1;
         }
-        let children = ChildrenIter::new(data, count);
 
-        let head = GreenNodeHead::from_child_iter(kind, children.clone());
+        let head = GreenNodeHead {
+            kind,
+            text_len,
+            child_hash: hasher.finish() as u32,
+        };
         self.nodes
-            .entry(head.clone())
-            .or_insert_with(|| GreenNode::from_head_and_children(head, children))
+            .entry(head)
+            .or_insert_with_key(|head| GreenNode::from_head_and_children(head.clone(), new_children))
             .clone()
     }
 
diff --git a/src/green/node.rs b/src/green/node.rs
index 1eab4d4..e0b8464 100644
--- a/src/green/node.rs
+++ b/src/green/node.rs
@@ -15,29 +15,9 @@ use triomphe::{Arc, HeaderWithLength, ThinArc};
 #[repr(align(2))] //to use 1 bit for pointer tagging. NB: this is an at-least annotation
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub(super) struct GreenNodeHead {
-    kind:       SyntaxKind,
-    text_len:   TextSize,
-    child_hash: u32,
-}
-
-impl GreenNodeHead {
-    #[inline]
-    pub(super) fn from_child_iter<I>(kind: SyntaxKind, children: I) -> Self
-    where
-        I: Iterator<Item = GreenElement>,
-    {
-        let mut hasher = FxHasher32::default();
-        let mut text_len: TextSize = 0.into();
-        for child in children {
-            text_len += child.text_len();
-            child.hash(&mut hasher);
-        }
-        Self {
-            kind,
-            text_len,
-            child_hash: hasher.finish() as u32,
-        }
-    }
+    pub(super) kind:       SyntaxKind,
+    pub(super) text_len:   TextSize,
+    pub(super) child_hash: u32,
 }
 
 /// Internal node in the immutable "green" tree.