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Split NamedMatch::MatchNonterminal in two.

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The `Lrc` is only relevant within `transcribe()`. There, the `Lrc` is
helpful for the non-`NtTT` cases, because the entire nonterminal is
cloned. But for the `NtTT` cases the inner token tree is cloned (a full
clone) and so the `Lrc` is of no help.

This commit splits the `NtTT` and non-`NtTT` cases, avoiding the useless
`Lrc` in the former case, for the following effect on macro-heavy
crates.
- It reduces the total number of allocations a lot.
- It increases the size of some of the remaining allocations.
- It doesn't affect *peak* memory usage, because the larger allocations
  are short-lived.

This overall gives a speed win.
This commit is contained in:
Nicholas Nethercote 2022-03-23 11:46:22 +11:00
parent 904e70a7b0
commit 6817442ec7
3 changed files with 81 additions and 71 deletions
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52
compiler/rustc_expand/src/mbe/macro_parser.rs
View file

@ -105,7 +105,7 @@ type NamedMatchVec = SmallVec<[NamedMatch; 4]>;
// This type is used a lot. Make sure it doesn't unintentionally get bigger.
#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
rustc_data_structures::static_assert_size!(NamedMatchVec, 72);
rustc_data_structures::static_assert_size!(NamedMatchVec, 168);
/// Represents a single "position" (aka "matcher position", aka "item"), as
/// described in the module documentation.
@ -278,22 +278,20 @@ pub(super) fn count_names(ms: &[TokenTree]) -> usize {
})
}
/// `NamedMatch` is a pattern-match result for a single `token::MATCH_NONTERMINAL`:
/// so it is associated with a single ident in a parse, and all
/// `MatchedNonterminal`s in the `NamedMatch` have the same non-terminal type
/// (expr, item, etc). Each leaf in a single `NamedMatch` corresponds to a
/// single `token::MATCH_NONTERMINAL` in the `TokenTree` that produced it.
/// `NamedMatch` is a pattern-match result for a single metavar. All
/// `MatchedNtNonTt`s in the `NamedMatch` have the same non-terminal type
/// (expr, item, etc).
///
/// The in-memory structure of a particular `NamedMatch` represents the match
/// that occurred when a particular subset of a matcher was applied to a
/// particular token tree.
///
/// The width of each `MatchedSeq` in the `NamedMatch`, and the identity of
/// the `MatchedNonterminal`s, will depend on the token tree it was applied
/// to: each `MatchedSeq` corresponds to a single `TTSeq` in the originating
/// the `MatchedNtNonTts`s, will depend on the token tree it was applied
/// to: each `MatchedSeq` corresponds to a single repetition in the originating
/// token tree. The depth of the `NamedMatch` structure will therefore depend
/// only on the nesting depth of `ast::TTSeq`s in the originating
/// token tree it was derived from.
/// only on the nesting depth of repetitions in the originating token tree it
/// was derived from.
///
/// In layman's terms: `NamedMatch` will form a tree representing nested matches of a particular
/// meta variable. For example, if we are matching the following macro against the following
@ -312,24 +310,32 @@ pub(super) fn count_names(ms: &[TokenTree]) -> usize {
/// ```rust
/// MatchedSeq([
/// MatchedSeq([
/// MatchedNonterminal(a),
/// MatchedNonterminal(b),
/// MatchedNonterminal(c),
/// MatchedNonterminal(d),
/// MatchedNtNonTt(a),
/// MatchedNtNonTt(b),
/// MatchedNtNonTt(c),
/// MatchedNtNonTt(d),
/// ]),
/// MatchedSeq([
/// MatchedNonterminal(a),
/// MatchedNonterminal(b),
/// MatchedNonterminal(c),
/// MatchedNonterminal(d),
/// MatchedNonterminal(e),
/// MatchedNtNonTt(a),
/// MatchedNtNonTt(b),
/// MatchedNtNonTt(c),
/// MatchedNtNonTt(d),
/// MatchedNtNonTt(e),
/// ])
/// ])
/// ```
#[derive(Debug, Clone)]
crate enum NamedMatch {
MatchedSeq(Lrc<NamedMatchVec>),
MatchedNonterminal(Lrc<Nonterminal>),
// This variant should never hold an `NtTT`. `MatchedNtTt` should be used
// for that case.
MatchedNtNonTt(Lrc<Nonterminal>),
// `NtTT` is handled without any cloning when transcribing, unlike other
// nonterminals. Therefore, an `Lrc` isn't helpful and causes unnecessary
// allocations. Hence this separate variant.
MatchedNtTt(rustc_ast::tokenstream::TokenTree),
}
/// Takes a slice of token trees `ms` representing a matcher which successfully matched input
@ -669,7 +675,11 @@ impl<'tt> TtParser<'tt> {
}
Ok(nt) => nt,
};
item.push_match(match_cur, MatchedNonterminal(Lrc::new(nt)));
let m = match nt {
Nonterminal::NtTT(tt) => MatchedNtTt(tt),
_ => MatchedNtNonTt(Lrc::new(nt)),
};
item.push_match(match_cur, m);
item.idx += 1;
item.match_cur += 1;
} else {

60
compiler/rustc_expand/src/mbe/macro_rules.rs
View file

@ -4,11 +4,11 @@ use crate::expand::{ensure_complete_parse, parse_ast_fragment, AstFragment, AstF
use crate::mbe;
use crate::mbe::macro_check;
use crate::mbe::macro_parser::{Error, ErrorReported, Failure, Success, TtParser};
use crate::mbe::macro_parser::{MatchedNonterminal, MatchedSeq};
use crate::mbe::macro_parser::{MatchedNtTt, MatchedSeq};
use crate::mbe::transcribe::transcribe;
use rustc_ast as ast;
use rustc_ast::token::{self, NonterminalKind, NtTT, Token, TokenKind::*};
use rustc_ast::token::{self, NonterminalKind, Token, TokenKind::*};
use rustc_ast::tokenstream::{DelimSpan, TokenStream};
use rustc_ast::{NodeId, DUMMY_NODE_ID};
use rustc_ast_pretty::pprust;
@ -470,22 +470,20 @@ pub fn compile_declarative_macro(
MatchedSeq(ref s) => s
.iter()
.map(|m| {
if let MatchedNonterminal(ref nt) = *m {
if let NtTT(ref tt) = **nt {
let mut tts = vec![];
mbe::quoted::parse(
tt.clone().into(),
true,
&sess.parse_sess,
def.id,
features,
edition,
&mut tts,
);
let tt = tts.pop().unwrap();
valid &= check_lhs_nt_follows(&sess.parse_sess, features, &def, &tt);
return tt;
}
if let MatchedNtTt(ref tt) = *m {
let mut tts = vec![];
mbe::quoted::parse(
tt.clone().into(),
true,
&sess.parse_sess,
def.id,
features,
edition,
&mut tts,
);
let tt = tts.pop().unwrap();
valid &= check_lhs_nt_follows(&sess.parse_sess, features, &def, &tt);
return tt;
}
sess.parse_sess.span_diagnostic.span_bug(def.span, "wrong-structured lhs")
})
@ -497,20 +495,18 @@ pub fn compile_declarative_macro(
MatchedSeq(ref s) => s
.iter()
.map(|m| {
if let MatchedNonterminal(ref nt) = *m {
if let NtTT(ref tt) = **nt {
let mut tts = vec![];
mbe::quoted::parse(
tt.clone().into(),
false,
&sess.parse_sess,
def.id,
features,
edition,
&mut tts,
);
return tts.pop().unwrap();
}
if let MatchedNtTt(ref tt) = *m {
let mut tts = vec![];
mbe::quoted::parse(
tt.clone().into(),
false,
&sess.parse_sess,
def.id,
features,
edition,
&mut tts,
);
return tts.pop().unwrap();
}
sess.parse_sess.span_diagnostic.span_bug(def.span, "wrong-structured lhs")
})

40
compiler/rustc_expand/src/mbe/transcribe.rs
View file

@ -1,8 +1,8 @@
use crate::base::ExtCtxt;
use crate::mbe::macro_parser::{MatchedNonterminal, MatchedSeq, NamedMatch};
use crate::mbe::macro_parser::{MatchedNtNonTt, MatchedNtTt, MatchedSeq, NamedMatch};
use crate::mbe::{self, MetaVarExpr};
use rustc_ast::mut_visit::{self, MutVisitor};
use rustc_ast::token::{self, NtTT, Token, TokenKind};
use rustc_ast::token::{self, Nonterminal, Token, TokenKind};
use rustc_ast::tokenstream::{DelimSpan, TokenStream, TokenTree, TreeAndSpacing};
use rustc_data_structures::fx::FxHashMap;
use rustc_data_structures::sync::Lrc;
@ -233,25 +233,29 @@ pub(super) fn transcribe<'a>(
// the meta-var.
let ident = MacroRulesNormalizedIdent::new(orignal_ident);
if let Some(cur_matched) = lookup_cur_matched(ident, interp, &repeats) {
if let MatchedNonterminal(nt) = cur_matched {
let token = if let NtTT(tt) = &**nt {
match cur_matched {
MatchedNtTt(ref tt) => {
// `tt`s are emitted into the output stream directly as "raw tokens",
// without wrapping them into groups.
tt.clone()
} else {
let token = tt.clone();
result.push(token.into());
}
MatchedNtNonTt(ref nt) => {
// Other variables are emitted into the output stream as groups with
// `Delimiter::None` to maintain parsing priorities.
// `Interpolated` is currently used for such groups in rustc parser.
debug_assert!(!matches!(**nt, Nonterminal::NtTT(_)));
marker.visit_span(&mut sp);
TokenTree::token(token::Interpolated(nt.clone()), sp)
};
result.push(token.into());
} else {
// We were unable to descend far enough. This is an error.
return Err(cx.struct_span_err(
sp, /* blame the macro writer */
&format!("variable '{}' is still repeating at this depth", ident),
));
let token = TokenTree::token(token::Interpolated(nt.clone()), sp);
result.push(token.into());
}
MatchedSeq(..) => {
// We were unable to descend far enough. This is an error.
return Err(cx.struct_span_err(
sp, /* blame the macro writer */
&format!("variable '{}' is still repeating at this depth", ident),
));
}
}
} else {
// If we aren't able to match the meta-var, we push it back into the result but
@ -308,7 +312,7 @@ fn lookup_cur_matched<'a>(
let mut matched = matched;
for &(idx, _) in repeats {
match matched {
MatchedNonterminal(_) => break,
MatchedNtTt(_) | MatchedNtNonTt(_) => break,
MatchedSeq(ref ads) => matched = ads.get(idx).unwrap(),
}
}
@ -398,7 +402,7 @@ fn lockstep_iter_size(
let name = MacroRulesNormalizedIdent::new(name);
match lookup_cur_matched(name, interpolations, repeats) {
Some(matched) => match matched {
MatchedNonterminal(_) => LockstepIterSize::Unconstrained,
MatchedNtTt(_) | MatchedNtNonTt(_) => LockstepIterSize::Unconstrained,
MatchedSeq(ref ads) => LockstepIterSize::Constraint(ads.len(), name),
},
_ => LockstepIterSize::Unconstrained,
@ -445,7 +449,7 @@ fn count_repetitions<'a>(
sp: &DelimSpan,
) -> PResult<'a, usize> {
match matched {
MatchedNonterminal(_) => {
MatchedNtTt(_) | MatchedNtNonTt(_) => {
if declared_lhs_depth == 0 {
return Err(cx.struct_span_err(
sp.entire(),