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Auto merge of #94709 - martingms:link-to-chunked-opt-pr, r=nnethercote

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Add link to closed PR for future optimizers of ChunkedBitSet relations

While optimizing these operations proved unfruitful w.r.t. improving compiler performance right now, faster versions might be needed at a later time. This PR adds a link in the FIXME to save any future optimizers some time, as requested by `@nnethercote` in https://github.com/rust-lang/rust/pull/94625.

r? `@nnethercote`
This commit is contained in:
bors 2022-03-07 21:20:05 +00:00
commit 89adcc636f
1 changed files with 8 additions and 4 deletions
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12
compiler/rustc_index/src/bit_set.rs
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@ -654,15 +654,19 @@ impl<T: Idx> BitRelations<ChunkedBitSet<T>> for ChunkedBitSet<T> {
impl<T: Idx> BitRelations<HybridBitSet<T>> for ChunkedBitSet<T> {
fn union(&mut self, other: &HybridBitSet<T>) -> bool {
// FIXME: this is slow if `other` is dense, and could easily be
// improved, but it hasn't been a problem in practice so far.
// FIXME: This is slow if `other` is dense, but it hasn't been a problem
// in practice so far.
// If a a faster implementation of this operation is required, consider
// reopening https://github.com/rust-lang/rust/pull/94625
assert_eq!(self.domain_size, other.domain_size());
sequential_update(|elem| self.insert(elem), other.iter())
}
fn subtract(&mut self, other: &HybridBitSet<T>) -> bool {
// FIXME: this is slow if `other` is dense, and could easily be
// improved, but it hasn't been a problem in practice so far.
// FIXME: This is slow if `other` is dense, but it hasn't been a problem
// in practice so far.
// If a a faster implementation of this operation is required, consider
// reopening https://github.com/rust-lang/rust/pull/94625
assert_eq!(self.domain_size, other.domain_size());
sequential_update(|elem| self.remove(elem), other.iter())
}