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Use otherwise_block for or-pattern shortcutting

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This commit is contained in:
Nadrieril 2024-03-04 01:41:37 +01:00
parent 5fe2ca65cf
commit 764f086f2c
1 changed files with 8 additions and 3 deletions
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11
compiler/rustc_mir_build/src/build/matches/mod.rs
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@ -1585,18 +1585,23 @@ fn test_candidates_with_or(
// We could add them to the or-candidates before the call to `test_or_pattern` but this
// would make it impossible to detect simplifiable or-patterns. That would guarantee
// exponentially large CFGs for cases like `(1 | 2, 3 | 4, ...)`.
let mut last_otherwise = None;
first_candidate.visit_leaves(|leaf_candidate| {
last_otherwise = leaf_candidate.otherwise_block;
});
first_candidate.visit_leaves(|leaf_candidate| {
assert!(leaf_candidate.match_pairs.is_empty());
leaf_candidate.match_pairs.extend(remaining_match_pairs.iter().cloned());
let or_start = leaf_candidate.pre_binding_block.unwrap();
// In a case like `(P | Q, R | S)`, if `P` succeeds and `R | S` fails, we know `(Q,
// R | S)` will fail too. If there is no guard, we skip testing of `Q` by branching
// directly to `remainder_start`. If there is a guard, `or_otherwise` can be reached
// by guard failure as well, so we can't skip `Q`.
// directly to `last_otherwise`. If there is a guard,
// `leaf_candidate.otherwise_block` can be reached by guard failure as well, so we
// can't skip `Q`.
let or_otherwise = if leaf_candidate.has_guard {
leaf_candidate.otherwise_block.unwrap()
} else {
remainder_start
last_otherwise.unwrap()
};
self.test_candidates_with_or(
span,