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perf(codegen): reduce memory allocations in generate_line_offset_tables #13054

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Merged
merged 1 commit into from
Aug 13, 2025
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perf(codegen): reduce memory allocations in generate_line_offset_tables #13054

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7 changes: 4 additions & 3 deletions crates/oxc_codegen/src/sourcemap_builder.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -325,6 +325,7 @@ impl<'a> SourcemapBuilder<'a> {
column_offsets_id: None,
});

let mut columns = vec![]; // Used as a buffer to reduce memory reallocations.
let remaining = &content.as_bytes()[line_byte_offset as usize..];
for (byte_offset_from_line_start, b) in remaining.iter().enumerate() {
#[expect(clippy::cast_possible_truncation)]
Expand All @@ -350,7 +351,7 @@ impl<'a> SourcemapBuilder<'a> {
line.column_offsets_id =
Some(ColumnOffsetsId::from_usize(column_offsets.len()));

let mut columns = vec![];
columns.clear();

// Loop through rest of line char-by-char.
// `chunk_byte_offset` in this loop is byte offset from start of this 1st
Expand Down Expand Up @@ -395,7 +396,7 @@ impl<'a> SourcemapBuilder<'a> {
// Record column offsets
column_offsets.push(ColumnOffsets {
byte_offset_to_first: byte_offset_from_line_start,
columns: columns.into_boxed_slice(),
columns: columns.into_iter().collect(),
});

// Revert back to outer loop for next line
Expand All @@ -409,7 +410,7 @@ impl<'a> SourcemapBuilder<'a> {
// Record column offsets
column_offsets.push(ColumnOffsets {
byte_offset_to_first: byte_offset_from_line_start,
columns: columns.into_boxed_slice(),
columns: columns.into_iter().collect(),
});

break 'lines;
Expand Down
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