Replace speculative Rc lists with an indexed arena - #89
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WalkthroughThe parser now stores speculative nodes, child sequences, diagnostics, and related payloads in a parser-owned recognition arena addressed by compact IDs. Recognition, recovery, outcome selection, deduplication, boundary folding, and parse-tree materialization use arena helpers. Poem
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Copy/Paste DetectionFound 10 duplication(s) across 2 changed Rust file(s) (threshold: 100 tokens). Show duplicationsFound a 27 line (145 tokens) duplication in the following files:
fn generated_match_token_recovers_missing_token_from_context_follow() {
let atn = generated_match_recovery_atn();
let data = RecognizerData::new(
"Mini.g4",
Vocabulary::new(
[None, Some("'X'"), Some("'Y'")],
[None, Some("X"), Some("Y")],
[None::<&str>, None, None],
),
);
let mut parser = BaseParser::new(
CommonTokenStream::new(Source {
tokens: vec![TestToken::eof("parser-test", 3, 1, 3)],
index: 0,
}),
data,
);
parser.rule_context_stack = vec![
RuleContextFrame {
rule_index: 0,
invoking_state: 0,
},
RuleContextFrame {
rule_index: 1,
invoking_state: 1,
},
];Found a 29 line (123 tokens) duplication in the following files:
let boundary = left_recursive_boundary(atn, state, *target);
outcomes.extend(
self.recognize_state_fast(
atn,
FastRecognizeRequest {
state_number: *target,
stop_state,
index,
rule_start_index,
decision_start_index: next_decision_start_index,
precedence,
depth: depth + 1,
recovery_symbols: Rc::clone(&epsilon_recovery_symbols),
recovery_state: epsilon_recovery_state,
},
visiting,
memo,
expected,
)
.into_iter()
.map(|mut outcome| {
if let Some(rule_index) = boundary {
let boundary = self.arena_boundary_node(rule_index);
self.arena_prepend(&mut outcome.nodes, boundary);
}
outcome
}),
);
}Found a 33 line (115 tokens) duplication in the following files:
outcomes.extend(
self.recognize_state(
atn,
RecognizeRequest {
state_number: *target,
stop_state,
index,
rule_start_index,
decision_start_index: next_decision_start_index,
init_action_rules,
predicates,
semantics,
rule_args,
member_actions,
return_actions,
local_int_arg,
member_values: member_values.clone(),
return_values: return_values.clone(),
rule_alt_number: next_alt_number,
track_alt_numbers,
consumed_eof,
precedence,
depth: depth + 1,
recovery_symbols: epsilon_recovery_symbols.clone(),
recovery_state: epsilon_recovery_state,
},
visiting,
memo,
expected,
)
.into_iter()
.map(|mut outcome| {
prepend_decision(&mut outcome, decision);Found a 21 line (113 tokens) duplication in the following files:
let start_state = atn
.rule_to_start_state()
.get(rule_index)
.copied()
.ok_or_else(|| {
AntlrError::Unsupported(format!("rule {rule_index} has no start state"))
})?;
let stop_state = atn
.rule_to_stop_state()
.get(rule_index)
.copied()
.filter(|state| *state != usize::MAX)
.ok_or_else(|| {
AntlrError::Unsupported(format!("rule {rule_index} has no stop state"))
})?;
let start_index = self.current_visible_index();
self.clear_prediction_diagnostics();
self.reset_per_parse_caches();
self.reset_recognition_arena();
let caller_follow_state = self.pending_invoking_follow_state(atn);Found a 15 line (113 tokens) duplication in the following files:
fn generated_match_token_counts_single_token_deletion_recovery() {
let atn = generated_match_recovery_atn();
let data = RecognizerData::new(
"Mini.g4",
Vocabulary::new(
[None, Some("'X'"), Some("'Y'"), Some("'Z'")],
[None, Some("X"), Some("Y"), Some("Z")],
[None::<&str>, None, None, None],
),
);
let mut parser = BaseParser::new(
CommonTokenStream::new(Source {
tokens: vec![
TestToken::new(3).with_text("z"),
TestToken::new(2).with_text("y"),Found a 14 line (110 tokens) duplication in the following files:
fn parser_matches_token_and_reports_mismatch() {
let source = Source {
tokens: vec![
TestToken::new(1).with_text("x"),
TestToken::eof("parser-test", 1, 1, 1),
],
index: 0,
};
let data = RecognizerData::new(
"Mini.g4",
Vocabulary::new([None, Some("'x'")], [None, Some("X")], [None::<&str>, None]),
);
let mut parser = BaseParser::new(CommonTokenStream::new(source), data);
let matched = parser.match_token(1).expect("token 1 should match");Found a 13 line (109 tokens) duplication in the following files:
fn parser_matches_token_and_reports_mismatch() {
let source = Source {
tokens: vec![
TestToken::new(1).with_text("x"),
TestToken::eof("parser-test", 1, 1, 1),
],
index: 0,
};
let data = RecognizerData::new(
"Mini.g4",
Vocabulary::new([None, Some("'x'")], [None, Some("X")], [None::<&str>, None]),
);
let mut parser = BaseParser::new(CommonTokenStream::new(source), data);Found a 22 line (108 tokens) duplication in the following files:
) -> Option<RecognizeOutcome> {
let (error_index, message) = self.expected_error_message(rule_index, start_index, expected);
let diagnostic = diagnostic_for_token(self.token_at(error_index), message);
let mut next_index = error_index;
loop {
let symbol = self.token_type_at(next_index);
if sync_symbols.contains(&symbol) {
if next_index == error_index {
return None;
}
break;
}
if symbol == TOKEN_EOF {
break;
}
let after = self.consume_index(next_index, symbol);
if after == next_index {
break;
}
next_index = after;
}
let mut nodes = NodeSeqId::EMPTY;Found a 15 line (108 tokens) duplication in the following files:
fn outcome_ties_keep_later_non_recursive_alternative() {
let arena = RecognitionArena::default();
let first = RecognizeOutcome {
index: 1,
consumed_eof: false,
alt_number: 0,
member_values: BTreeMap::new(),
return_values: BTreeMap::new(),
diagnostics: DiagnosticSeqId::EMPTY,
decisions: Vec::new(),
actions: vec![ParserAction::new(1, 0, 0, None)],
nodes: NodeSeqId::EMPTY,
};
let second = RecognizeOutcome {
actions: vec![ParserAction::new(2, 0, 0, None)],Found a 12 line (102 tokens) duplication in the following files:
atn.add_state(AtnState::new(4, AtnStateKind::BlockEnd).with_rule_index(0));
atn.add_state(AtnState::new(5, AtnStateKind::RuleStop).with_rule_index(0));
atn.set_rule_to_start_state(vec![0]);
atn.set_rule_to_stop_state(vec![5]);
atn.add_decision_state(1);
atn.state_mut(0)
.expect("state 0")
.add_transition(Transition::Epsilon { target: 1 });
atn.state_mut(1)
.expect("state 1")
.add_transition(Transition::Atom {
target: 2, |
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Code Review
This pull request introduces a parser-owned, index-addressed recognition arena to replace speculative Rc node lists with compact IDs, which significantly improves parsing performance and reduces memory allocations. It also exports RecognitionArenaStats and updates the changelog and README with detailed benchmark results. There are no review comments, so I have no feedback to provide.
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Actionable comments posted: 1
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Verify each finding against current code. Fix only still-valid issues, skip the
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Inline comments:
In `@src/parser.rs`:
- Line 5642: The arena statistics snapshots in src/parser.rs at lines 5642-5642
and 6165-6165 are taken before recursive tree materialization and boundary
folding completes. Move each record_recognition_arena_stats call to after all
folding/materialization, passing the final folded root’s arena state so
RecognitionArenaStats reflects current totals, live records, and capacities.
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📒 Files selected for processing (4)
CHANGELOG.mdREADME.mdsrc/lib.rssrc/parser.rs
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tinovyatkin
changed the title
1 participant
Addresses #83
What changed
RecognizedNode/FastRecognizedNodeobject graphs and persistentNodeListtails with compact node and sequence IDs into a parser-owned append-only arena.TokenId, and move missing-token text, return values, and diagnostics into side pools.Rcnode graphs.RecognitionArenaStatsfor total/live/dead node, link, and extra counts plus retained capacities; emit the same counters throughANTLR_PERF_DUMP.Why
The previous persistent representation shared tails, but every speculative node and list tail still incurred allocator and reference-count traffic. Losing alternatives amplified that cost on ambiguous or deeply nested grammars. The arena turns node creation and prepend operations into append-only vector writes while preserving alternative ordering, diagnostics, left-recursive folding, semantic behavior, and child order.
The current public recursive tree is still produced at one compatibility boundary. Issue #84 will replace that boundary with direct flat-CST handoff; this PR does not add a second tree implementation or a legacy recognition fallback.
Measured impact
A same-machine forced-interpreter Kotlin comparison against
c068688dbused 100 measured parses per fixture:On the largest fixture, maximum RSS fell from 37.29 MB to 32.83 MB (-12.0%). The normal 17-fixture generated-parser sweep had no C#, Java, or Trino regression above 1%; Kotlin improved on all four fixtures.
Validation
cargo fmt --checkcargo test --locked --all-targets --all-featurescargo clippy --locked --all-targets --all-features -- -D warningscargo run --release --quiet --bin antlr4-runtime-testsuite(356 passed, 0 failed, 1 skipped)tests/kotlin-parity/run.sh ...(nine file/script fixtures byte-identical toantlr4-python3-runtime)