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perf(syntax): pack ASCII identifier tables into single bitflag table #19088

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Merged
graphite-app merged 1 commit into from
Feb 7, 2026
Merged

perf(syntax): pack ASCII identifier tables into single bitflag table #19088

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1 change: 0 additions & 1 deletion Cargo.lock
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1 change: 0 additions & 1 deletion crates/oxc_syntax/Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -22,7 +22,6 @@ doctest = false
[dependencies]
oxc_allocator = { workspace = true }
oxc_ast_macros = { workspace = true }
oxc_data_structures = { workspace = true, features = ["assert_unchecked"] }
oxc_estree = { workspace = true }
oxc_index = { workspace = true }
oxc_span = { workspace = true }
Expand Down
60 changes: 21 additions & 39 deletions crates/oxc_syntax/src/identifier.rs
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Expand Up @@ -2,8 +2,6 @@

use unicode_id_start::{is_id_continue_unicode, is_id_start_unicode};

use oxc_data_structures::assert_unchecked;

use crate::line_terminator::{CR, LF, LS, PS};

pub const EOF: char = '\0';
Expand Down Expand Up @@ -83,38 +81,26 @@ pub fn is_white_space_single_line(c: char) -> bool {
matches!(c, SP | TAB) || is_irregular_whitespace(c)
}

const XX: bool = true;
const __: bool = false;
const ID_START: u8 = 1;
const ID_CONTINUE: u8 = 2;

#[repr(C, align(64))]
pub struct Align64<T>(pub(crate) T);

// `a`-`z`, `A`-`Z`, `$` (0x24), `_` (0x5F)
#[rustfmt::skip]
pub static ASCII_START: Align64<[bool; 128]> = Align64([
// 0 1 2 3 4 5 6 7 8 9 A B C D E F //
__, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // 0
__, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // 1
__, __, __, __, XX, __, __, __, __, __, __, __, __, __, __, __, // 2
__, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // 3
__, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, // 4
XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, __, __, __, __, XX, // 5
__, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, // 6
XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, __, __, __, __, __, // 7
]);

// `ASCII_START` + `0`-`9`
// Packed: ID_START | ID_CONTINUE per ASCII byte.
// `a`-`z`, `A`-`Z`, `$`, `_` get ID_START | ID_CONTINUE (3).
// `0`-`9` get ID_CONTINUE only (2).
#[rustfmt::skip]
pub static ASCII_CONTINUE: Align64<[bool; 128]> = Align64([
// 0 1 2 3 4 5 6 7 8 9 A B C D E F //
__, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // 0
__, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // 1
__, __, __, __, XX, __, __, __, __, __, __, __, __, __, __, __, // 2
XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, __, __, __, __, __, __, // 3
__, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, // 4
XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, __, __, __, __, XX, // 5
__, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, // 6
XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, __, __, __, __, __, // 7
pub static ASCII_ID_FLAGS: Align64<[u8; 128]> = Align64([
// 0 1 2 3 4 5 6 7 8 9 A B C D E F //
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 0
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 1
0, 0, 0, 0, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 2 $ = 3
2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 0, 0, 0, 0, 0, 0, // 3 0-9 = 2
0, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, // 4 A-Z = 3
3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 0, 0, 0, 0, 3, // 5 _ = 3
0, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, // 6 a-z = 3
3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 0, 0, 0, 0, 0, // 7
]);

/// Section 12.7 Detect `IdentifierStartChar`
Expand All @@ -128,7 +114,7 @@ pub fn is_identifier_start(c: char) -> bool {

#[inline]
pub fn is_identifier_start_ascii(c: char) -> bool {
ASCII_START.0[c as usize]
ASCII_ID_FLAGS.0[c as usize] & ID_START != 0
}

#[inline]
Expand All @@ -148,7 +134,7 @@ pub fn is_identifier_part(c: char) -> bool {

#[inline]
pub fn is_identifier_part_ascii(c: char) -> bool {
ASCII_CONTINUE.0[c as usize]
ASCII_ID_FLAGS.0[c as usize] & ID_CONTINUE != 0
}

#[inline]
Expand All @@ -171,7 +157,7 @@ pub fn is_identifier_name(name: &str) -> bool {

let mut chars = if first_byte.is_ascii() {
// First byte is ASCII
if !is_identifier_start_ascii(first_byte as char) {
if ASCII_ID_FLAGS.0[first_byte as usize] & ID_START == 0 {
return false;
}

Expand All @@ -196,9 +182,7 @@ pub fn is_identifier_name(name: &str) -> bool {

let next8 = next8_as_u64.to_ne_bytes();
for b in next8 {
// SAFETY: We just checked all these bytes are ASCII
unsafe { assert_unchecked!(b.is_ascii()) };
if !is_identifier_part_ascii(b as char) {
if ASCII_ID_FLAGS.0[b as usize] & ID_CONTINUE == 0 {
return false;
}
}
Expand All @@ -221,9 +205,7 @@ pub fn is_identifier_name(name: &str) -> bool {

let next4 = next4_as_u32.to_ne_bytes();
for b in next4 {
// SAFETY: We just checked all these bytes are ASCII
unsafe { assert_unchecked!(b.is_ascii()) };
if !is_identifier_part_ascii(b as char) {
if ASCII_ID_FLAGS.0[b as usize] & ID_CONTINUE == 0 {
return false;
}
}
Expand All @@ -237,7 +219,7 @@ pub fn is_identifier_name(name: &str) -> bool {
};

if b.is_ascii() {
if !is_identifier_part_ascii(b as char) {
if ASCII_ID_FLAGS.0[b as usize] & ID_CONTINUE == 0 {
return false;
}
} else {
Expand Down
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