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Move or-pattern expansion inside the main part of the algorithm

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This commit is contained in:
Nadrieril 2024-06-30 12:25:07 +02:00
parent bff4d213fa
commit c5062f7318
1 changed files with 24 additions and 36 deletions
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60
compiler/rustc_mir_build/src/build/matches/mod.rs
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@ -1119,6 +1119,11 @@ fn from_flat_pat(flat_pat: FlatPat<'pat, 'tcx>, has_guard: bool) -> Self {
}
}
/// Returns whether the first match pair of this candidate is an or-pattern.
fn starts_with_or_pattern(&self) -> bool {
matches!(&*self.match_pairs, [MatchPair { test_case: TestCase::Or { .. }, .. }, ..])
}
/// Visit the leaf candidates (those with no subcandidates) contained in
/// this candidate.
fn visit_leaves<'a>(&'a mut self, mut visit_leaf: impl FnMut(&'a mut Self)) {
@ -1435,39 +1440,20 @@ fn match_candidates(
otherwise_block: BasicBlock,
candidates: &mut [&mut Candidate<'_, 'tcx>],
) {
// If any candidate starts with an or-pattern, we have to expand the or-pattern before we
// can proceed further.
let expand_ors = candidates.iter().any(|candidate| {
matches!(
&*candidate.match_pairs,
[MatchPair { test_case: TestCase::Or { .. }, .. }, ..]
)
});
ensure_sufficient_stack(|| {
if !expand_ors {
// No candidates start with an or-pattern, we can continue.
self.match_expanded_candidates(
span,
scrutinee_span,
start_block,
otherwise_block,
candidates,
);
} else {
self.expand_and_match_or_candidates(
span,
scrutinee_span,
start_block,
otherwise_block,
candidates,
);
}
self.match_candidates_with_enough_stack(
span,
scrutinee_span,
start_block,
otherwise_block,
candidates,
)
});
}
/// Construct the decision tree for `candidates`. Caller must ensure that no candidate in
/// `candidates` starts with an or-pattern.
fn match_expanded_candidates(
/// Construct the decision tree for `candidates`. Don't call this, call `match_candidates`
/// instead to reserve sufficient stack space.
fn match_candidates_with_enough_stack(
&mut self,
span: Span,
scrutinee_span: Span,
@ -1492,12 +1478,17 @@ fn match_expanded_candidates(
// The first candidate has satisfied all its match pairs; we link it up and continue
// with the remaining candidates.
start_block = self.select_matched_candidate(first, start_block);
self.match_expanded_candidates(
self.match_candidates(span, scrutinee_span, start_block, otherwise_block, remaining)
}
candidates if candidates.iter().any(|candidate| candidate.starts_with_or_pattern()) => {
// If any candidate starts with an or-pattern, we have to expand the or-pattern before we
// can proceed further.
self.expand_and_match_or_candidates(
span,
scrutinee_span,
start_block,
otherwise_block,
remaining,
candidates,
)
}
candidates => {
@ -1591,9 +1582,7 @@ fn expand_and_match_or_candidates(
let mut expand_until = 0;
for (i, candidate) in candidates.iter().enumerate() {
expand_until = i + 1;
if candidate.match_pairs.len() > 1
&& matches!(&candidate.match_pairs[0].test_case, TestCase::Or { .. })
{
if candidate.match_pairs.len() > 1 && candidate.starts_with_or_pattern() {
// The candidate has an or-pattern as well as more match pairs: we must
// split the candidates list here.
break;
@ -1604,8 +1593,7 @@ fn expand_and_match_or_candidates(
// Expand one level of or-patterns for each candidate in `candidates_to_expand`.
let mut expanded_candidates = Vec::new();
for candidate in candidates_to_expand.iter_mut() {
if let [MatchPair { test_case: TestCase::Or { .. }, .. }, ..] = &*candidate.match_pairs
{
if candidate.starts_with_or_pattern() {
let or_match_pair = candidate.match_pairs.remove(0);
// Expand the or-pattern into subcandidates.
self.create_or_subcandidates(candidate, or_match_pair);