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nhwn: optimize counting digits in line numbers

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This commit is contained in:
Nathan Nguyen 2021-02-17 23:44:37 -06:00
parent 93f6a4b9d8
commit 8a5c5681da
1 changed files with 12 additions and 1 deletions
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13
compiler/rustc_errors/src/emitter.rs
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@ -1713,7 +1713,18 @@ fn emit_messages_default(
let max_line_num_len = if self.ui_testing {
ANONYMIZED_LINE_NUM.len()
} else {
self.get_max_line_num(span, children).to_string().len()
// Instead of using .to_string().len(), we iteratively count the
// number of digits to avoid allocation. This strategy has sizable
// performance gains over the old string strategy.
let mut n = self.get_max_line_num(span, children);
let mut num_digits = 0;
loop {
num_digits += 1;
n /= 10;
if n == 0 {
break num_digits;
}
}
};
match self.emit_message_default(span, message, code, level, max_line_num_len, false) {