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perf: Make barrel optimizer use Atom instead of String (#75592)
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### What?

Use `swc_atoms::Atom` instead of `String` in `next-swc`. 

### Why?

`Atom` does not allocate if another instance has the same value, meaning that `clone()` is a single atomic operation. But `String` allocates regardless of any other occurrence.
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@kdy1
kdy1 authored Feb 4, 2025
1 parent f998bdb commit c1d9a04
Showing 1 changed file with 38 additions and 40 deletions.
78 changes: 38 additions & 40 deletions crates/next-custom-transforms/src/transforms/optimize_barrel.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,7 @@ use std::collections::HashMap;

use serde::Deserialize;
use swc_core::{
atoms::{atom, Atom},
common::DUMMY_SP,
ecma::{
ast::*,
Expand Down Expand Up @@ -36,32 +37,29 @@ impl Fold for OptimizeBarrel {
for item in &items {
if let ModuleItem::ModuleDecl(ModuleDecl::Import(import_decl)) = item {
for spec in &import_decl.specifiers {
let src = import_decl.src.value.to_string();
let src = import_decl.src.value.clone();
match spec {
ImportSpecifier::Named(s) => {
local_idents.insert(
s.local.sym.to_string(),
s.local.sym.clone(),
(
src.clone(),
match &s.imported {
Some(n) => match &n {
ModuleExportName::Ident(n) => n.sym.to_string(),
ModuleExportName::Str(n) => n.value.to_string(),
ModuleExportName::Ident(n) => n.sym.clone(),
ModuleExportName::Str(n) => n.value.clone(),
},
None => s.local.sym.to_string(),
None => s.local.sym.clone(),
},
),
);
}
ImportSpecifier::Namespace(s) => {
local_idents
.insert(s.local.sym.to_string(), (src.clone(), "*".to_string()));
local_idents.insert(s.local.sym.clone(), (src.clone(), atom!("*")));
}
ImportSpecifier::Default(s) => {
local_idents.insert(
s.local.sym.to_string(),
(src.clone(), "default".to_string()),
);
local_idents
.insert(s.local.sym.clone(), (src.clone(), atom!("default")));
}
}
}
Expand Down Expand Up @@ -95,20 +93,20 @@ impl Fold for OptimizeBarrel {
match spec {
ExportSpecifier::Namespace(s) => {
let name_str = match &s.name {
ModuleExportName::Ident(n) => n.sym.to_string(),
ModuleExportName::Str(n) => n.value.to_string(),
ModuleExportName::Ident(n) => n.sym.clone(),
ModuleExportName::Str(n) => n.value.clone(),
};
if let Some(src) = &export_named.src {
export_map.push((
name_str.clone(),
src.value.to_string(),
"*".to_string(),
src.value.clone(),
atom!("*"),
));
} else if self.wildcard {
export_map.push((
name_str.clone(),
"".into(),
"*".to_string(),
Atom::default(),
atom!("*"),
));
} else {
is_barrel = false;
Expand All @@ -117,21 +115,21 @@ impl Fold for OptimizeBarrel {
}
ExportSpecifier::Named(s) => {
let orig_str = match &s.orig {
ModuleExportName::Ident(n) => n.sym.to_string(),
ModuleExportName::Str(n) => n.value.to_string(),
ModuleExportName::Ident(n) => n.sym.clone(),
ModuleExportName::Str(n) => n.value.clone(),
};
let name_str = match &s.exported {
Some(n) => match &n {
ModuleExportName::Ident(n) => n.sym.to_string(),
ModuleExportName::Str(n) => n.value.to_string(),
ModuleExportName::Ident(n) => n.sym.clone(),
ModuleExportName::Str(n) => n.value.clone(),
},
None => orig_str.clone(),
};

if let Some(src) = &export_named.src {
export_map.push((
name_str.clone(),
src.value.to_string(),
src.value.clone(),
orig_str.clone(),
));
} else if let Some((src, orig)) =
Expand All @@ -145,7 +143,7 @@ impl Fold for OptimizeBarrel {
} else if self.wildcard {
export_map.push((
name_str.clone(),
"".into(),
Atom::default(),
orig_str.clone(),
));
} else {
Expand Down Expand Up @@ -175,22 +173,22 @@ impl Fold for OptimizeBarrel {
match &export_decl.decl {
Decl::Class(class) => {
export_map.push((
class.ident.sym.to_string(),
"".into(),
"".into(),
class.ident.sym.clone(),
Atom::default(),
Atom::default(),
));
}
Decl::Fn(func) => {
export_map.push((
func.ident.sym.to_string(),
"".into(),
"".into(),
func.ident.sym.clone(),
Atom::default(),
Atom::default(),
));
}
Decl::Var(var) => {
let ids = collect_idents_in_var_decls(&var.decls);
for id in ids {
export_map.push((id, "".into(), "".into()));
export_map.push((id, Atom::default(), Atom::default()));
}
}
_ => {}
Expand Down Expand Up @@ -306,13 +304,13 @@ impl Fold for OptimizeBarrel {
}
}

fn collect_idents_in_array_pat(elems: &[Option<Pat>]) -> Vec<String> {
fn collect_idents_in_array_pat(elems: &[Option<Pat>]) -> Vec<Atom> {
let mut ids = Vec::new();

for elem in elems.iter().flatten() {
match elem {
Pat::Ident(ident) => {
ids.push(ident.sym.to_string());
ids.push(ident.sym.clone());
}
Pat::Array(array) => {
ids.extend(collect_idents_in_array_pat(&array.elems));
Expand All @@ -322,7 +320,7 @@ fn collect_idents_in_array_pat(elems: &[Option<Pat>]) -> Vec<String> {
}
Pat::Rest(rest) => {
if let Pat::Ident(ident) = &*rest.arg {
ids.push(ident.sym.to_string());
ids.push(ident.sym.clone());
}
}
_ => {}
Expand All @@ -332,19 +330,19 @@ fn collect_idents_in_array_pat(elems: &[Option<Pat>]) -> Vec<String> {
ids
}

fn collect_idents_in_object_pat(props: &[ObjectPatProp]) -> Vec<String> {
fn collect_idents_in_object_pat(props: &[ObjectPatProp]) -> Vec<Atom> {
let mut ids = Vec::new();

for prop in props {
match prop {
ObjectPatProp::KeyValue(KeyValuePatProp { key, value }) => {
if let PropName::Ident(ident) = key {
ids.push(ident.sym.to_string());
ids.push(ident.sym.clone());
}

match &**value {
Pat::Ident(ident) => {
ids.push(ident.sym.to_string());
ids.push(ident.sym.clone());
}
Pat::Array(array) => {
ids.extend(collect_idents_in_array_pat(&array.elems));
Expand All @@ -356,11 +354,11 @@ fn collect_idents_in_object_pat(props: &[ObjectPatProp]) -> Vec<String> {
}
}
ObjectPatProp::Assign(AssignPatProp { key, .. }) => {
ids.push(key.to_string());
ids.push(key.sym.clone());
}
ObjectPatProp::Rest(RestPat { arg, .. }) => {
if let Pat::Ident(ident) = &**arg {
ids.push(ident.sym.to_string());
ids.push(ident.sym.clone());
}
}
}
Expand All @@ -369,13 +367,13 @@ fn collect_idents_in_object_pat(props: &[ObjectPatProp]) -> Vec<String> {
ids
}

fn collect_idents_in_var_decls(decls: &[VarDeclarator]) -> Vec<String> {
fn collect_idents_in_var_decls(decls: &[VarDeclarator]) -> Vec<Atom> {
let mut ids = Vec::new();

for decl in decls {
match &decl.name {
Pat::Ident(ident) => {
ids.push(ident.sym.to_string());
ids.push(ident.sym.clone());
}
Pat::Array(array) => {
ids.extend(collect_idents_in_array_pat(&array.elems));
Expand Down

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