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Extend Printer::buf on demand.

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So that 55 entries (at 48 bytes each) don't need to be eagerly
initialized on creation.

This speeds up numerous rust-perf benchmark runs, by up to 3%.
This commit is contained in:
Nicholas Nethercote 2018-04-28 07:33:34 +10:00
parent f76f6fbdea
commit 989815d567
1 changed files with 23 additions and 7 deletions
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30
src/libsyntax/print/pp.rs
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@ -247,12 +247,14 @@ pub fn mk_printer<'a>(out: Box<io::Write+'a>, linewidth: usize) -> Printer<'a> {
debug!("mk_printer {}", linewidth);
Printer {
out,
buf_len: n,
buf_max_len: n,
margin: linewidth as isize,
space: linewidth as isize,
left: 0,
right: 0,
buf: vec![BufEntry { token: Token::Eof, size: 0 }; n],
// Initialize a single entry; advance_right() will extend it on demand
// up to `buf_max_len` elements.
buf: vec![BufEntry::default()],
left_total: 0,
right_total: 0,
scan_stack: VecDeque::new(),
@ -263,7 +265,7 @@ pub fn mk_printer<'a>(out: Box<io::Write+'a>, linewidth: usize) -> Printer<'a> {
pub struct Printer<'a> {
out: Box<io::Write+'a>,
buf_len: usize,
buf_max_len: usize,
/// Width of lines we're constrained to
margin: isize,
/// Number of spaces left on line
@ -297,6 +299,12 @@ struct BufEntry {
size: isize,
}
impl Default for BufEntry {
fn default() -> Self {
BufEntry { token: Token::Eof, size: 0 }
}
}
impl<'a> Printer<'a> {
pub fn last_token(&mut self) -> Token {
self.buf[self.right].token.clone()
@ -322,7 +330,9 @@ impl<'a> Printer<'a> {
self.right_total = 1;
self.left = 0;
self.right = 0;
} else { self.advance_right(); }
} else {
self.advance_right();
}
debug!("pp Begin({})/buffer Vec<{},{}>",
b.offset, self.left, self.right);
self.buf[self.right] = BufEntry { token: token, size: -self.right_total };
@ -349,7 +359,9 @@ impl<'a> Printer<'a> {
self.right_total = 1;
self.left = 0;
self.right = 0;
} else { self.advance_right(); }
} else {
self.advance_right();
}
debug!("pp Break({})/buffer Vec<{},{}>",
b.offset, self.left, self.right);
self.check_stack(0);
@ -408,7 +420,11 @@ impl<'a> Printer<'a> {
}
pub fn advance_right(&mut self) {
self.right += 1;
self.right %= self.buf_len;
self.right %= self.buf_max_len;
// Extend the buf if necessary.
if self.right == self.buf.len() {
self.buf.push(BufEntry::default());
}
assert_ne!(self.right, self.left);
}
pub fn advance_left(&mut self) -> io::Result<()> {
@ -438,7 +454,7 @@ impl<'a> Printer<'a> {
}
self.left += 1;
self.left %= self.buf_len;
self.left %= self.buf_max_len;
left_size = self.buf[self.left].size;
}