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i8 and u8::to_string() specialisation (far less asm). #82576

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merged 6 commits into from
May 3, 2021
Merged

i8 and u8::to_string() specialisation (far less asm). #82576

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a69960a
u8::to_string() specialisation (far less asm).
gilescope Feb 26, 2021
d07c43a
Alternative LUT rather than dividing.
gilescope Mar 4, 2021
a678b9a
less uB in i8
gilescope Mar 4, 2021
e83378b
vec![0;4] is a fast path.
gilescope Mar 7, 2021
6a58b6a
Update library/alloc/src/string.rs
gilescope Mar 8, 2021
05330aa
Closer similarities.
gilescope Mar 8, 2021
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41 changes: 41 additions & 0 deletions library/alloc/src/string.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2224,6 +2224,47 @@ impl ToString for char {
}
}

#[stable(feature = "u8_to_string_specialization", since = "1.999.0")]
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@pickfire pickfire May 12, 2021 •
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What is with the since tag? Why 1.999?

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Already fixed on master.

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Ah sorry, wasn't sure what to put for that. Yes 1.54 makes sense, but at the time I didn't want to presume so put something a little further out.

impl ToString for u8 {
#[inline]
fn to_string(&self) -> String {
let mut buf = String::with_capacity(3);
let mut n = *self;
if n >= 10 {
if n >= 100 {
buf.push((b'0' + n / 100) as char);
n %= 100;
}
buf.push((b'0' + n / 10) as char);
n %= 10;
}
buf.push((b'0' + n) as char);
buf
}
}

#[stable(feature = "i8_to_string_specialization", since = "1.999.0")]
impl ToString for i8 {
#[inline]
fn to_string(&self) -> String {
let mut buf = String::with_capacity(4);
if self.is_negative() {
buf.push('-');
}
let mut n = self.unsigned_abs();
if n >= 10 {
if n >= 100 {
buf.push('1');
n -= 100;
}
buf.push((b'0' + n / 10) as char);
n %= 10;
}
buf.push((b'0' + n) as char);
buf
}
}

#[stable(feature = "str_to_string_specialization", since = "1.9.0")]
impl ToString for str {
#[inline]
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