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Remove the loop from Parser::bump().

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The loop is there to handle a `NoDelim` open/close token. This commit
changes `TokenCursor::inlined_next` so it never returns such a token.
This is a performance win because the conditional test in `bump()` is
removed.

If the parser needs changing in the future to handle `NoDelim` tokens,
then `inlined_next()` can easily be changed to return them.
This commit is contained in:
Nicholas Nethercote 2022-04-20 12:22:42 +10:00
parent 3cd5e34617
commit b09522a634
1 changed files with 34 additions and 29 deletions
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63
compiler/rustc_parse/src/parser/mod.rs
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@ -242,12 +242,17 @@ struct TokenCursorFrame {
delim: token::DelimToken,
span: DelimSpan,
tree_cursor: tokenstream::Cursor,
close_delim: bool,
need_to_produce_close_delim: bool,
}
impl TokenCursorFrame {
fn new(span: DelimSpan, delim: DelimToken, tts: TokenStream, close_delim: bool) -> Self {
TokenCursorFrame { delim, span, tree_cursor: tts.into_trees(), close_delim }
fn new(span: DelimSpan, delim: DelimToken, tts: TokenStream) -> Self {
TokenCursorFrame {
delim,
span,
tree_cursor: tts.into_trees(),
need_to_produce_close_delim: delim != DelimToken::NoDelim,
}
}
}
@ -261,28 +266,32 @@ impl TokenCursor {
fn inlined_next(&mut self, desugar_doc_comments: bool) -> (Token, Spacing) {
loop {
if let Some((tree, spacing)) = self.frame.tree_cursor.next_with_spacing() {
return match tree {
match tree {
TokenTree::Token(token) => match (desugar_doc_comments, &token) {
(true, &Token { kind: token::DocComment(_, attr_style, data), span }) => {
self.desugar(attr_style, data, span)
return self.desugar(attr_style, data, span);
}
_ => (token, spacing),
_ => return (token, spacing),
},
TokenTree::Delimited(sp, delim, tts) => {
// Set `open_delim` to true here because we deal with it immediately.
let frame = TokenCursorFrame::new(sp, delim, tts, false);
let frame = TokenCursorFrame::new(sp, delim, tts);
self.stack.push(mem::replace(&mut self.frame, frame));
(Token::new(token::OpenDelim(delim), sp.open), Spacing::Alone)
if delim != DelimToken::NoDelim {
return (Token::new(token::OpenDelim(delim), sp.open), Spacing::Alone);
}
// No open delimeter to return; continue on to the next iteration.
}
};
} else if !self.frame.close_delim {
self.frame.close_delim = true;
} else if self.frame.need_to_produce_close_delim {
self.frame.need_to_produce_close_delim = false;
return (
Token::new(token::CloseDelim(self.frame.delim), self.frame.span.close),
Spacing::Alone,
);
} else if let Some(frame) = self.stack.pop() {
self.frame = frame;
// Back to the parent frame; continue on to the next iteration.
} else {
return (Token::new(token::Eof, DUMMY_SP), Spacing::Alone);
}
@ -333,7 +342,6 @@ impl TokenCursor {
.cloned()
.collect::<TokenStream>()
},
true,
),
));
@ -422,7 +430,7 @@ impl<'a> Parser<'a> {
desugar_doc_comments: bool,
subparser_name: Option<&'static str>,
) -> Self {
let start_frame = TokenCursorFrame::new(DelimSpan::dummy(), token::NoDelim, tokens, true);
let start_frame = TokenCursorFrame::new(DelimSpan::dummy(), token::NoDelim, tokens);
let mut parser = Parser {
sess,
@ -993,24 +1001,21 @@ impl<'a> Parser<'a> {
/// Advance the parser by one token.
pub fn bump(&mut self) {
let fallback_span = self.token.span;
loop {
let (mut next, spacing) = self.token_cursor.inlined_next(self.desugar_doc_comments);
self.token_cursor.num_next_calls += 1;
// We've retrieved an token from the underlying
// cursor, so we no longer need to worry about
// an unglued token. See `break_and_eat` for more details
self.token_cursor.break_last_token = false;
if next.span.is_dummy() {
// Tweak the location for better diagnostics, but keep syntactic context intact.
next.span = fallback_span.with_ctxt(next.span.ctxt());
}
if !matches!(
next.kind,
token::OpenDelim(token::NoDelim) | token::CloseDelim(token::NoDelim)
) {
return self.inlined_bump_with((next, spacing));
}
let (mut next, spacing) = self.token_cursor.inlined_next(self.desugar_doc_comments);
self.token_cursor.num_next_calls += 1;
// We've retrieved an token from the underlying
// cursor, so we no longer need to worry about
// an unglued token. See `break_and_eat` for more details
self.token_cursor.break_last_token = false;
if next.span.is_dummy() {
// Tweak the location for better diagnostics, but keep syntactic context intact.
next.span = fallback_span.with_ctxt(next.span.ctxt());
}
debug_assert!(!matches!(
next.kind,
token::OpenDelim(token::NoDelim) | token::CloseDelim(token::NoDelim)
));
self.inlined_bump_with((next, spacing))
}
/// Look-ahead `dist` tokens of `self.token` and get access to that token there.