51 lines
1.5 KiB
Rust
51 lines
1.5 KiB
Rust
use rustc_index::bit_set::BitSet;
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use rustc_index::vec::Idx;
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use std::collections::VecDeque;
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/// A work queue is a handy data structure for tracking work left to
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/// do. (For example, basic blocks left to process.) It is basically a
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/// de-duplicating queue; so attempting to insert X if X is already
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/// enqueued has no effect. This implementation assumes that the
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/// elements are dense indices, so it can allocate the queue to size
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/// and also use a bit set to track occupancy.
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pub struct WorkQueue<T: Idx> {
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deque: VecDeque<T>,
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set: BitSet<T>,
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}
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impl<T: Idx> WorkQueue<T> {
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/// Creates a new work queue that starts empty, where elements range from (0..len).
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#[inline]
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pub fn with_none(len: usize) -> Self {
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WorkQueue { deque: VecDeque::with_capacity(len), set: BitSet::new_empty(len) }
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}
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/// Attempt to enqueue `element` in the work queue. Returns false if it was already present.
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#[inline]
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pub fn insert(&mut self, element: T) -> bool {
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if self.set.insert(element) {
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self.deque.push_back(element);
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true
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} else {
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false
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}
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}
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/// Attempt to pop an element from the work queue.
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#[inline]
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pub fn pop(&mut self) -> Option<T> {
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if let Some(element) = self.deque.pop_front() {
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self.set.remove(element);
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Some(element)
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} else {
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None
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}
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}
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/// Returns `true` if nothing is enqueued.
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#[inline]
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pub fn is_empty(&self) -> bool {
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self.deque.is_empty()
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}
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}
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