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Call compute_locs once per rule.
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Currently it's called in `parse_tt` every time a match rule is invoked.
This commit moves it so it's called instead once per match rule, in
`compile_declarative_macro. This is a performance win.

The commit also moves `compute_locs` out of `TtParser`, because there's
no longer any reason for it to be in there.
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@nnethercote
nnethercote committed Apr 6, 2022
1 parent 7300bd6 commit 238d907
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Showing 2 changed files with 123 additions and 114 deletions.
186 changes: 89 additions & 97 deletions compiler/rustc_expand/src/mbe/macro_parser.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -106,7 +106,7 @@ rustc_data_structures::static_assert_size!(NamedMatchVec, 48);
///
/// This means a matcher can be represented by `&[MatcherLoc]`, and traversal mostly involves
/// simply incrementing the current matcher position index by one.
enum MatcherLoc {
pub(super) enum MatcherLoc {
Token {
token: Token,
},
Expand Down Expand Up @@ -138,6 +138,78 @@ enum MatcherLoc {
Eof,
}

pub(super) fn compute_locs(sess: &ParseSess, matcher: &[TokenTree]) -> Vec<MatcherLoc> {
fn inner(
sess: &ParseSess,
tts: &[TokenTree],
locs: &mut Vec<MatcherLoc>,
next_metavar: &mut usize,
seq_depth: usize,
) {
for tt in tts {
match tt {
TokenTree::Token(token) => {
locs.push(MatcherLoc::Token { token: token.clone() });
}
TokenTree::Delimited(_, delimited) => {
locs.push(MatcherLoc::Delimited);
inner(sess, &delimited.all_tts, locs, next_metavar, seq_depth);
}
TokenTree::Sequence(_, seq) => {
// We can't determine `idx_first_after` and construct the final
// `MatcherLoc::Sequence` until after `inner()` is called and the sequence end
// pieces are processed. So we push a dummy value (`Eof` is cheapest to
// construct) now, and overwrite it with the proper value below.
let dummy = MatcherLoc::Eof;
locs.push(dummy);

let next_metavar_orig = *next_metavar;
let op = seq.kleene.op;
let idx_first = locs.len();
let idx_seq = idx_first - 1;
inner(sess, &seq.tts, locs, next_metavar, seq_depth + 1);

if let Some(separator) = &seq.separator {
locs.push(MatcherLoc::SequenceSep { separator: separator.clone() });
locs.push(MatcherLoc::SequenceKleeneOpAfterSep { idx_first });
} else {
locs.push(MatcherLoc::SequenceKleeneOpNoSep { op, idx_first });
}

// Overwrite the dummy value pushed above with the proper value.
locs[idx_seq] = MatcherLoc::Sequence {
op,
num_metavar_decls: seq.num_captures,
idx_first_after: locs.len(),
next_metavar: next_metavar_orig,
seq_depth,
};
}
&TokenTree::MetaVarDecl(span, bind, kind) => {
locs.push(MatcherLoc::MetaVarDecl {
span,
bind,
kind,
next_metavar: *next_metavar,
seq_depth,
});
*next_metavar += 1;
}
TokenTree::MetaVar(..) | TokenTree::MetaVarExpr(..) => unreachable!(),
}
}
}

let mut locs = vec![];
let mut next_metavar = 0;
inner(sess, matcher, &mut locs, &mut next_metavar, /* seq_depth */ 0);

// A final entry is needed for eof.
locs.push(MatcherLoc::Eof);

locs
}

/// A single matcher position, representing the state of matching.
struct MatcherPos {
/// The index into `TtParser::locs`, which represents the "dot".
Expand Down Expand Up @@ -301,9 +373,6 @@ fn token_name_eq(t1: &Token, t2: &Token) -> bool {
pub struct TtParser {
macro_name: Ident,

/// The matcher of the current rule.
locs: Vec<MatcherLoc>,

/// The set of current mps to be processed. This should be empty by the end of a successful
/// execution of `parse_tt_inner`.
cur_mps: Vec<MatcherPos>,
Expand All @@ -324,92 +393,13 @@ impl TtParser {
pub(super) fn new(macro_name: Ident) -> TtParser {
TtParser {
macro_name,
locs: vec![],
cur_mps: vec![],
next_mps: vec![],
bb_mps: vec![],
empty_matches: Lrc::new(smallvec![]),
}
}

/// Convert a `&[TokenTree]` to a `&[MatcherLoc]`. Note: this conversion happens every time the
/// macro is called, which may be many times if there are many call sites or if it is
/// recursive. This conversion is fairly cheap and the representation is sufficiently better
/// for matching than `&[TokenTree]` that it's a clear performance win even with the overhead.
/// But it might be possible to move the conversion outwards so it only occurs once per macro.
fn compute_locs(&mut self, sess: &ParseSess, matcher: &[TokenTree]) -> usize {
fn inner(
sess: &ParseSess,
tts: &[TokenTree],
locs: &mut Vec<MatcherLoc>,
next_metavar: &mut usize,
seq_depth: usize,
) {
for tt in tts {
match tt {
TokenTree::Token(token) => {
locs.push(MatcherLoc::Token { token: token.clone() });
}
TokenTree::Delimited(_, delimited) => {
locs.push(MatcherLoc::Delimited);
inner(sess, &delimited.all_tts, locs, next_metavar, seq_depth);
}
TokenTree::Sequence(_, seq) => {
// We can't determine `idx_first_after` and construct the final
// `MatcherLoc::Sequence` until after `inner()` is called and the sequence
// end pieces are processed. So we push a dummy value (`Eof` is cheapest to
// construct) now, and overwrite it with the proper value below.
let dummy = MatcherLoc::Eof;
locs.push(dummy);

let next_metavar_orig = *next_metavar;
let op = seq.kleene.op;
let idx_first = locs.len();
let idx_seq = idx_first - 1;
inner(sess, &seq.tts, locs, next_metavar, seq_depth + 1);

if let Some(separator) = &seq.separator {
locs.push(MatcherLoc::SequenceSep { separator: separator.clone() });
locs.push(MatcherLoc::SequenceKleeneOpAfterSep { idx_first });
} else {
locs.push(MatcherLoc::SequenceKleeneOpNoSep { op, idx_first });
}

// Overwrite the dummy value pushed above with the proper value.
locs[idx_seq] = MatcherLoc::Sequence {
op,
num_metavar_decls: seq.num_captures,
idx_first_after: locs.len(),
next_metavar: next_metavar_orig,
seq_depth,
};
}
&TokenTree::MetaVarDecl(span, bind, kind) => {
locs.push(MatcherLoc::MetaVarDecl {
span,
bind,
kind,
next_metavar: *next_metavar,
seq_depth,
});
*next_metavar += 1;
}
TokenTree::MetaVar(..) | TokenTree::MetaVarExpr(..) => unreachable!(),
}
}
}

self.locs.clear();
let mut next_metavar = 0;
inner(sess, matcher, &mut self.locs, &mut next_metavar, /* seq_depth */ 0);

// A final entry is needed for eof.
self.locs.push(MatcherLoc::Eof);

// This is the number of metavar decls.
next_metavar
}

/// Process the matcher positions of `cur_mps` until it is empty. In the process, this will
/// produce more mps in `next_mps` and `bb_mps`.
///
Expand All @@ -420,15 +410,15 @@ impl TtParser {
fn parse_tt_inner(
&mut self,
sess: &ParseSess,
num_metavar_decls: usize,
matcher: &[MatcherLoc],
token: &Token,
) -> Option<NamedParseResult> {
// Matcher positions that would be valid if the macro invocation was over now. Only
// modified if `token == Eof`.
let mut eof_mps = EofMatcherPositions::None;

while let Some(mut mp) = self.cur_mps.pop() {
match &self.locs[mp.idx] {
match &matcher[mp.idx] {
MatcherLoc::Token { token: t } => {
// If it's a doc comment, we just ignore it and move on to the next tt in the
// matcher. This is a bug, but #95267 showed that existing programs rely on
Expand Down Expand Up @@ -536,7 +526,7 @@ impl TtParser {
}
MatcherLoc::Eof => {
// We are past the matcher's end, and not in a sequence. Try to end things.
debug_assert_eq!(mp.idx, self.locs.len() - 1);
debug_assert_eq!(mp.idx, matcher.len() - 1);
if *token == token::Eof {
eof_mps = match eof_mps {
EofMatcherPositions::None => EofMatcherPositions::One(mp),
Expand All @@ -554,11 +544,10 @@ impl TtParser {
if *token == token::Eof {
Some(match eof_mps {
EofMatcherPositions::One(mut eof_mp) => {
assert_eq!(eof_mp.matches.len(), num_metavar_decls);
// Need to take ownership of the matches from within the `Lrc`.
Lrc::make_mut(&mut eof_mp.matches);
let matches = Lrc::try_unwrap(eof_mp.matches).unwrap().into_iter();
self.nameize(sess, matches)
self.nameize(sess, matcher, matches)
}
EofMatcherPositions::Multiple => {
Error(token.span, "ambiguity: multiple successful parses".to_string())
Expand All @@ -580,10 +569,8 @@ impl TtParser {
pub(super) fn parse_tt(
&mut self,
parser: &mut Cow<'_, Parser<'_>>,
matcher: &[TokenTree],
matcher: &[MatcherLoc],
) -> NamedParseResult {
let num_metavar_decls = self.compute_locs(parser.sess, matcher);

// A queue of possible matcher positions. We initialize it with the matcher position in
// which the "dot" is before the first token of the first token tree in `matcher`.
// `parse_tt_inner` then processes all of these possible matcher positions and produces
Expand All @@ -598,7 +585,7 @@ impl TtParser {

// Process `cur_mps` until either we have finished the input or we need to get some
// parsing from the black-box parser done.
if let Some(res) = self.parse_tt_inner(&parser.sess, num_metavar_decls, &parser.token) {
if let Some(res) = self.parse_tt_inner(&parser.sess, matcher, &parser.token) {
return res;
}

Expand Down Expand Up @@ -626,7 +613,7 @@ impl TtParser {
(0, 1) => {
// We need to call the black-box parser to get some nonterminal.
let mut mp = self.bb_mps.pop().unwrap();
let loc = &self.locs[mp.idx];
let loc = &matcher[mp.idx];
if let &MatcherLoc::MetaVarDecl {
span,
kind: Some(kind),
Expand Down Expand Up @@ -664,19 +651,23 @@ impl TtParser {

(_, _) => {
// Too many possibilities!
return self.ambiguity_error(parser.token.span);
return self.ambiguity_error(matcher, parser.token.span);
}
}

assert!(!self.cur_mps.is_empty());
}
}

fn ambiguity_error(&self, token_span: rustc_span::Span) -> NamedParseResult {
fn ambiguity_error(
&self,
matcher: &[MatcherLoc],
token_span: rustc_span::Span,
) -> NamedParseResult {
let nts = self
.bb_mps
.iter()
.map(|mp| match &self.locs[mp.idx] {
.map(|mp| match &matcher[mp.idx] {
MatcherLoc::MetaVarDecl { bind, kind: Some(kind), .. } => {
format!("{} ('{}')", kind, bind)
}
Expand All @@ -702,12 +693,13 @@ impl TtParser {
fn nameize<I: Iterator<Item = NamedMatch>>(
&self,
sess: &ParseSess,
matcher: &[MatcherLoc],
mut res: I,
) -> NamedParseResult {
// Make that each metavar has _exactly one_ binding. If so, insert the binding into the
// `NamedParseResult`. Otherwise, it's an error.
let mut ret_val = FxHashMap::default();
for loc in self.locs.iter() {
for loc in matcher {
if let &MatcherLoc::MetaVarDecl { span, bind, kind, .. } = loc {
if kind.is_some() {
match ret_val.entry(MacroRulesNormalizedIdent::new(bind)) {
Expand Down
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