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refactor(sourcemap): align Base64 chars lookup table to cache line #4535

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graphite-app merged 1 commit into from
Jul 30, 2024
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refactor(sourcemap): align Base64 chars lookup table to cache line #4535

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refactor(sourcemap): align Base64 chars lookup table to cache line (#… 
…4535)

Align the Base64 chars lookup table in sourcemap generator so it occupies a single cache line.
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@overlookmotel
overlookmotel committed Jul 30, 2024
commit 7c42ffcd06766c3b6141f47f9d884e945db01e5f
13 changes: 11 additions & 2 deletions crates/oxc_sourcemap/src/encode.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -168,7 +168,16 @@ fn encode_vlq_diff(out: &mut String, a: u32, b: u32) {
encode_vlq(out, i64::from(a) - i64::from(b));
}

const B64_CHARS: &[u8] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
// Align chars lookup table on 64 so occupies a single cache line
#[repr(align(64))]
struct Aligned64([u8; 64]);

static B64_CHARS: Aligned64 = Aligned64([
b'A', b'B', b'C', b'D', b'E', b'F', b'G', b'H', b'I', b'J', b'K', b'L', b'M', b'N', b'O', b'P',
b'Q', b'R', b'S', b'T', b'U', b'V', b'W', b'X', b'Y', b'Z', b'a', b'b', b'c', b'd', b'e', b'f',
b'g', b'h', b'i', b'j', b'k', b'l', b'm', b'n', b'o', b'p', b'q', b'r', b's', b't', b'u', b'v',
b'w', b'x', b'y', b'z', b'0', b'1', b'2', b'3', b'4', b'5', b'6', b'7', b'8', b'9', b'+', b'/',
]);

#[allow(clippy::cast_possible_truncation, clippy::cast_sign_loss)]
fn encode_vlq(out: &mut String, num: i64) {
Expand All @@ -180,7 +189,7 @@ fn encode_vlq(out: &mut String, num: i64) {
if num > 0 {
digit |= 1 << 5;
}
out.push(B64_CHARS[digit as usize] as char);
out.push(B64_CHARS.0[digit as usize] as char);
if num == 0 {
break;
}
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