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perf(es/minifier): Speed up merge_sequences_in_exprs by caching computation #9843

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merged 10 commits into from
Jan 7, 2025
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perf(es/minifier): Speed up merge_sequences_in_exprs by caching computation #9843

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605cc82
cache ident usages
CPunisher Jan 5, 2025
7031cc8
cache top retain check
CPunisher Jan 5, 2025
7d2ca52
fix is_top_retain
CPunisher Jan 5, 2025
cfeeac9
fix a_idx
CPunisher Jan 5, 2025
92dd8b4
simply optimization
CPunisher Jan 6, 2025
6a92f9b
invalidate
CPunisher Jan 6, 2025
3e036e5
fix
CPunisher Jan 6, 2025
dd165fb
add invalidate
CPunisher Jan 7, 2025
9ddccb8
fix
CPunisher Jan 7, 2025
75045a4
Create forty-maps-smoke.md
kdy1 Jan 7, 2025
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6 changes: 6 additions & 0 deletions .changeset/forty-maps-smoke.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,6 @@
---
swc_core: patch
swc_ecma_minifier: patch
---

perf(es/minifier): Speed up `merge_sequences_in_exprs` by caching computation
141 changes: 93 additions & 48 deletions crates/swc_ecma_minifier/src/compress/optimize/sequences.rs
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Original file line number Diff line number Diff line change
@@ -1,14 +1,14 @@
use std::{iter::once, mem::take};

use rustc_hash::FxHashSet;
use swc_common::{pass::Either, util::take::Take, Spanned, DUMMY_SP};
use swc_ecma_ast::*;
use swc_ecma_usage_analyzer::{
alias::{collect_infects_from, AccessKind, AliasConfig},
util::is_global_var_with_pure_property_access,
};
use swc_ecma_utils::{
contains_arguments, contains_this_expr, prepend_stmts, ExprExt, IdentUsageFinder, StmtLike,
Type, Value,
contains_arguments, contains_this_expr, prepend_stmts, ExprExt, StmtLike, Type, Value,
};
use swc_ecma_visit::{noop_visit_type, Visit, VisitWith};
#[cfg(feature = "debug")]
Expand All @@ -23,7 +23,10 @@ use crate::{
util::{is_directive, is_ident_used_by, replace_expr},
},
option::CompressOptions,
util::{idents_used_by, idents_used_by_ignoring_nested, ExprOptExt, ModuleItemExt},
util::{
idents_used_by, idents_used_by_ignoring_nested, ExprOptExt, IdentUsageCollector,
ModuleItemExt,
},
};

/// Methods related to the option `sequences`. All methods are noop if
Expand Down Expand Up @@ -821,22 +824,17 @@ impl Optimizer<'_> {
)
};

let mut merge_seq_cache = MergeSequenceCache::new(exprs.len());
loop {
let mut did_work = false;

for idx in 0..exprs.len() {
for j in idx..exprs.len() {
let (a1, a2) = exprs.split_at_mut(idx);

if a1.is_empty() || a2.is_empty() {
break;
}

let mut changed = false;
for a_idx in 0..exprs.len().saturating_sub(1) {
for b_idx in (a_idx + 1)..exprs.len() {
let (a1, a2) = exprs.split_at_mut(a_idx + 1);
let a = a1.last_mut().unwrap();
let b = &mut a2[b_idx - a_idx - 1];

if self.options.unused && self.options.sequences() {
if let (Mergable::Var(av), Mergable::Var(bv)) = (&mut *a, &mut a2[j - idx])
{
if let (Mergable::Var(av), Mergable::Var(bv)) = (&mut *a, &mut *b) {
// We try dropping variable assignments first.

// Currently, we only drop variable declarations if they have the same
Expand All @@ -847,7 +845,7 @@ impl Optimizer<'_> {

match bv.init.as_deref_mut() {
Some(b_init) => {
if IdentUsageFinder::find(&an.to_id(), b_init) {
if is_ident_used_by(an.to_id(), b_init) {
log_abort!(
"We can't duplicated binding because \
initializer uses the previous declaration of \
Expand All @@ -859,14 +857,16 @@ impl Optimizer<'_> {
if let Some(a_init) = av.init.take() {
let b_seq = b_init.force_seq();
b_seq.exprs.insert(0, a_init);
merge_seq_cache.invalidate(a_idx);
merge_seq_cache.invalidate(b_idx);

self.changed = true;
report_change!(
"Moving initializer sequentially as they have \
a same name"
);
av.name.take();
continue;
break;
} else {
self.changed = true;
report_change!(
Expand All @@ -875,7 +875,7 @@ impl Optimizer<'_> {
an.id
);
av.name.take();
continue;
break;
}
}
None => {
Expand All @@ -890,13 +890,15 @@ impl Optimizer<'_> {
//
// prints 5
bv.init = av.init.take();
merge_seq_cache.invalidate(a_idx);
merge_seq_cache.invalidate(b_idx);
self.changed = true;
report_change!(
"Moving initializer to the next variable \
declaration as they have the same name"
);
av.name.take();
continue;
break;
}
}
}
Expand All @@ -906,26 +908,36 @@ impl Optimizer<'_> {

// Merge sequentially

match &mut a2[j - idx] {
match b {
Mergable::Var(b) => match b.init.as_deref_mut() {
Some(b) => {
if self.merge_sequential_expr(a, b)? {
did_work = true;
if !merge_seq_cache.is_top_retain(self, a, a_idx)
&& self.merge_sequential_expr(a, b)?
{
changed = true;
merge_seq_cache.invalidate(a_idx);
merge_seq_cache.invalidate(b_idx);
break;
}
}
None => continue,
},
Mergable::Expr(b) => {
if self.merge_sequential_expr(a, b)? {
did_work = true;
if !merge_seq_cache.is_top_retain(self, a, a_idx)
&& self.merge_sequential_expr(a, b)?
{
changed = true;
merge_seq_cache.invalidate(a_idx);
merge_seq_cache.invalidate(b_idx);
break;
}
}
Mergable::FnDecl(..) => continue,
Mergable::Drop => {
if self.drop_mergable_seq(a)? {
did_work = true;
changed = true;
merge_seq_cache.invalidate(a_idx);
merge_seq_cache.invalidate(b_idx);
break;
}
}
Expand Down Expand Up @@ -972,16 +984,16 @@ impl Optimizer<'_> {
_ => {}
}

match &a2[j - idx] {
match b {
Mergable::Var(e2) => {
if let Some(e2) = &e2.init {
if !self.is_skippable_for_seq(Some(a), e2) {
break;
}
}

if let Some(id) = a1.last_mut().unwrap().id() {
if IdentUsageFinder::find(&id, &**e2) {
if let Some(id) = a.id() {
if merge_seq_cache.is_ident_used_by(&id, &**e2, b_idx) {
break;
}
}
Expand All @@ -991,9 +1003,8 @@ impl Optimizer<'_> {
break;
}

if let Some(id) = a1.last_mut().unwrap().id() {
// TODO(kdy1): Optimize
if IdentUsageFinder::find(&id, &**e2) {
if let Some(id) = a.id() {
if merge_seq_cache.is_ident_used_by(&id, &**e2, b_idx) {
break;
}
}
Expand All @@ -1019,7 +1030,7 @@ impl Optimizer<'_> {
}
}

if !did_work {
if !changed {
break;
}
}
Expand Down Expand Up @@ -1527,10 +1538,6 @@ impl Optimizer<'_> {
///
/// Returns [Err] iff we should stop checking.
fn merge_sequential_expr(&mut self, a: &mut Mergable, b: &mut Expr) -> Result<bool, ()> {
if let Mergable::Drop = a {
return Ok(false);
}

#[cfg(feature = "debug")]
let _tracing = {
let b_str = dump(&*b, false);
Expand All @@ -1552,16 +1559,6 @@ impl Optimizer<'_> {
)
};

// Respect top_retain
if let Some(a_id) = a.id() {
if a_id.0 == "arguments"
|| (matches!(a, Mergable::Var(_) | Mergable::FnDecl(_))
&& !self.may_remove_ident(&Ident::from(a_id)))
{
return Ok(false);
}
}

match &*b {
Expr::Arrow(..)
| Expr::Fn(..)
Expand Down Expand Up @@ -1801,7 +1798,7 @@ impl Optimizer<'_> {

if !self.is_skippable_for_seq(Some(a), &b_left.id.clone().into()) {
// Let's be safe
if IdentUsageFinder::find(&b_left.to_id(), &b_assign.right) {
if is_ident_used_by(b_left.to_id(), &b_assign.right) {
return Ok(false);
}

Expand All @@ -1817,7 +1814,7 @@ impl Optimizer<'_> {
return Ok(false);
}

if IdentUsageFinder::find(&b_left.to_id(), &b_assign.right) {
if is_ident_used_by(b_left.to_id(), &b_assign.right) {
return Err(());
}

Expand Down Expand Up @@ -2710,6 +2707,54 @@ impl Mergable<'_> {
}
}

#[derive(Debug, Default)]
struct MergeSequenceCache {
ident_usage_cache: Vec<Option<FxHashSet<Id>>>,
top_retain_cache: Vec<Option<bool>>,
}

impl MergeSequenceCache {
fn new(cap: usize) -> Self {
Self {
ident_usage_cache: vec![None; cap],
top_retain_cache: vec![None; cap],
}
}

fn is_ident_used_by<N: VisitWith<IdentUsageCollector>>(
&mut self,
ident: &Id,
node: &N,
node_id: usize,
) -> bool {
let idents = self.ident_usage_cache[node_id].get_or_insert_with(|| idents_used_by(node));
idents.contains(ident)
}

fn invalidate(&mut self, node_id: usize) {
self.ident_usage_cache[node_id] = None;
}

fn is_top_retain(&mut self, optimizer: &Optimizer, a: &Mergable, node_id: usize) -> bool {
*self.top_retain_cache[node_id].get_or_insert_with(|| {
if let Mergable::Drop = a {
return true;
}

if let Some(a_id) = a.id() {
if a_id.0 == "arguments"
|| (matches!(a, Mergable::Var(_) | Mergable::FnDecl(_))
&& !optimizer.may_remove_ident(&Ident::from(a_id)))
{
return true;
}
}

false
})
}
}

/// Returns true for trivial bool/numeric literals
pub(crate) fn is_trivial_lit(e: &Expr) -> bool {
match e {
Expand Down
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