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perf(mangler): optimize handling of collecting lived scope ids (#8724)

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Just some low-hanging fruit optimization.

I initially want to dedupe for reference scopes, so that we can avoid calling `scope_tree.ancestors(used_scope_id).take_while(|s_id| *s_id != scope_id)` for duplicate `used_scope_id` but the overhead of calling `unique` or `dedup` is over the improvement.
This commit is contained in:
Dunqing 2025-01-26 10:53:48 +00:00
parent c79206850c
commit e472ced05f
3 changed files with 45 additions and 21 deletions
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33
crates/oxc_mangler/src/lib.rs
View file

@ -1,4 +1,3 @@
use std::iter;
use std::ops::Deref;
use fixedbitset::FixedBitSet;
@ -193,10 +192,7 @@ impl Mangler {
// Walk down the scope tree and assign a slot number for each symbol.
// It is possible to do this in a loop over the symbol list,
// but walking down the scope tree seems to generate a better code.
for scope_id in iter::once(scope_tree.root_scope_id())
.chain(scope_tree.iter_all_child_ids(scope_tree.root_scope_id()))
{
let bindings = scope_tree.get_bindings(scope_id);
for (scope_id, bindings) in scope_tree.iter_bindings() {
if bindings.is_empty() {
continue;
}
@ -227,33 +223,28 @@ impl Mangler {
tmp_bindings.clear();
tmp_bindings.extend(bindings.values().copied());
tmp_bindings.sort_unstable();
for (symbol_id, assigned_slot) in
for (&symbol_id, assigned_slot) in
tmp_bindings.iter().zip(reusable_slots.iter().copied())
{
slots[symbol_id.index()] = assigned_slot;
// If the symbol is declared by `var`, then it can be hoisted to
// parent, so we need to include the scope where it is declared.
// (for cases like `function foo() { { var x; let y; } }`)
let declared_scope_id =
ast_nodes.get_node(symbol_table.get_declaration(*symbol_id)).scope_id();
ast_nodes.get_node(symbol_table.get_declaration(symbol_id)).scope_id();
// Calculate the scope ids that this symbol is alive in.
let lived_scope_ids = symbol_table
.get_resolved_references(*symbol_id)
.flat_map(|reference| {
let used_scope_id = ast_nodes.get_node(reference.node_id()).scope_id();
.get_resolved_references(symbol_id)
.map(|reference| ast_nodes.get_node(reference.node_id()).scope_id())
.chain([scope_id, declared_scope_id])
.flat_map(|used_scope_id| {
scope_tree.ancestors(used_scope_id).take_while(|s_id| *s_id != scope_id)
})
// also include scopes that this symbol was declared (for cases like `function foo() { { var x; let y; } }`)
.chain(
scope_tree
.ancestors(declared_scope_id)
.take_while(|s_id| *s_id != scope_id),
)
.chain(iter::once(scope_id));
});
// Since the slot is now assigned to this symbol, it is alive in all the scopes that this symbol is alive in.
for scope_id in lived_scope_ids {
slot_liveness[assigned_slot].insert(scope_id.index());
}
slot_liveness[assigned_slot].extend(lived_scope_ids.map(oxc_index::Idx::index));
}
}

2
crates/oxc_minifier/tests/mangler/mod.rs
View file

@ -44,6 +44,8 @@ fn mangler() {
"function _() { var x; let y; }", // x and y should have different names
"function _() { { var x; var y; } }", // x and y should have different names
"function _() { { var x; let y; } }", // x and y should have different names
"function _() { let a; { let b; { let c; { let d; var x; } } } }",
"function _() { let a; { let b; { let c; { console.log(a); let d; var x; } } } }",
];
let top_level_cases = [
"function foo(a) {a}",

31
crates/oxc_minifier/tests/mangler/snapshots/mangler.snap
View file

@ -181,6 +181,37 @@ function _() {
}
}
function _() { let a; { let b; { let c; { let d; var x; } } } }
function _() {
let a;
{
let a;
{
let a;
{
let a;
var b;
}
}
}
}
function _() { let a; { let b; { let c; { console.log(a); let d; var x; } } } }
function _() {
let a;
{
let c;
{
let c;
{
console.log(a);
let c;
var b;
}
}
}
}
function foo(a) {a}
function a(a) {
a;