move bit_set into rustc_index

3 files changed, 1 insertions, 1355 deletions

diff --git a/src/librustc_data_structures/bit_set.rs b/src/librustc_data_structures/bit_set.rs
deleted file mode 100644
index fe8ef642430..00000000000
--- a/src/librustc_data_structures/bit_set.rs
+++ /dev/null
@@ -1,984 +0,0 @@
-use crate::indexed_vec::{Idx, IndexVec};
-use smallvec::SmallVec;
-use std::fmt;
-use std::iter;
-use std::marker::PhantomData;
-use std::mem;
-use std::slice;
-
-#[cfg(test)]
-mod tests;
-
-pub type Word = u64;
-pub const WORD_BYTES: usize = mem::size_of::<Word>();
-pub const WORD_BITS: usize = WORD_BYTES * 8;
-
-/// A fixed-size bitset type with a dense representation. It does not support
-/// resizing after creation; use `GrowableBitSet` for that.
-///
-/// `T` is an index type, typically a newtyped `usize` wrapper, but it can also
-/// just be `usize`.
-///
-/// All operations that involve an element will panic if the element is equal
-/// to or greater than the domain size. All operations that involve two bitsets
-/// will panic if the bitsets have differing domain sizes.
-#[derive(Clone, Eq, PartialEq, RustcDecodable, RustcEncodable)]
-pub struct BitSet<T: Idx> {
-    domain_size: usize,
-    words: Vec<Word>,
-    marker: PhantomData<T>,
-}
-
-impl<T: Idx> BitSet<T> {
-    /// Creates a new, empty bitset with a given `domain_size`.
-    #[inline]
-    pub fn new_empty(domain_size: usize) -> BitSet<T> {
-        let num_words = num_words(domain_size);
-        BitSet {
-            domain_size,
-            words: vec![0; num_words],
-            marker: PhantomData,
-        }
-    }
-
-    /// Creates a new, filled bitset with a given `domain_size`.
-    #[inline]
-    pub fn new_filled(domain_size: usize) -> BitSet<T> {
-        let num_words = num_words(domain_size);
-        let mut result = BitSet {
-            domain_size,
-            words: vec![!0; num_words],
-            marker: PhantomData,
-        };
-        result.clear_excess_bits();
-        result
-    }
-
-    /// Gets the domain size.
-    pub fn domain_size(&self) -> usize {
-        self.domain_size
-    }
-
-    /// Clear all elements.
-    #[inline]
-    pub fn clear(&mut self) {
-        for word in &mut self.words {
-            *word = 0;
-        }
-    }
-
-    /// Clear excess bits in the final word.
-    fn clear_excess_bits(&mut self) {
-        let num_bits_in_final_word = self.domain_size % WORD_BITS;
-        if num_bits_in_final_word > 0 {
-            let mask = (1 << num_bits_in_final_word) - 1;
-            let final_word_idx = self.words.len() - 1;
-            self.words[final_word_idx] &= mask;
-        }
-    }
-
-    /// Efficiently overwrite `self` with `other`.
-    pub fn overwrite(&mut self, other: &BitSet<T>) {
-        assert!(self.domain_size == other.domain_size);
-        self.words.clone_from_slice(&other.words);
-    }
-
-    /// Count the number of set bits in the set.
-    pub fn count(&self) -> usize {
-        self.words.iter().map(|e| e.count_ones() as usize).sum()
-    }
-
-    /// Returns `true` if `self` contains `elem`.
-    #[inline]
-    pub fn contains(&self, elem: T) -> bool {
-        assert!(elem.index() < self.domain_size);
-        let (word_index, mask) = word_index_and_mask(elem);
-        (self.words[word_index] & mask) != 0
-    }
-
-    /// Is `self` is a (non-strict) superset of `other`?
-    #[inline]
-    pub fn superset(&self, other: &BitSet<T>) -> bool {
-        assert_eq!(self.domain_size, other.domain_size);
-        self.words.iter().zip(&other.words).all(|(a, b)| (a & b) == *b)
-    }
-
-    /// Is the set empty?
-    #[inline]
-    pub fn is_empty(&self) -> bool {
-        self.words.iter().all(|a| *a == 0)
-    }
-
-    /// Insert `elem`. Returns whether the set has changed.
-    #[inline]
-    pub fn insert(&mut self, elem: T) -> bool {
-        assert!(elem.index() < self.domain_size);
-        let (word_index, mask) = word_index_and_mask(elem);
-        let word_ref = &mut self.words[word_index];
-        let word = *word_ref;
-        let new_word = word | mask;
-        *word_ref = new_word;
-        new_word != word
-    }
-
-    /// Sets all bits to true.
-    pub fn insert_all(&mut self) {
-        for word in &mut self.words {
-            *word = !0;
-        }
-        self.clear_excess_bits();
-    }
-
-    /// Returns `true` if the set has changed.
-    #[inline]
-    pub fn remove(&mut self, elem: T) -> bool {
-        assert!(elem.index() < self.domain_size);
-        let (word_index, mask) = word_index_and_mask(elem);
-        let word_ref = &mut self.words[word_index];
-        let word = *word_ref;
-        let new_word = word & !mask;
-        *word_ref = new_word;
-        new_word != word
-    }
-
-    /// Sets `self = self | other` and returns `true` if `self` changed
-    /// (i.e., if new bits were added).
-    pub fn union(&mut self, other: &impl UnionIntoBitSet<T>) -> bool {
-        other.union_into(self)
-    }
-
-    /// Sets `self = self - other` and returns `true` if `self` changed.
-    /// (i.e., if any bits were removed).
-    pub fn subtract(&mut self, other: &impl SubtractFromBitSet<T>) -> bool {
-        other.subtract_from(self)
-    }
-
-    /// Sets `self = self & other` and return `true` if `self` changed.
-    /// (i.e., if any bits were removed).
-    pub fn intersect(&mut self, other: &BitSet<T>) -> bool {
-        assert_eq!(self.domain_size, other.domain_size);
-        bitwise(&mut self.words, &other.words, |a, b| { a & b })
-    }
-
-    /// Gets a slice of the underlying words.
-    pub fn words(&self) -> &[Word] {
-        &self.words
-    }
-
-    /// Iterates over the indices of set bits in a sorted order.
-    #[inline]
-    pub fn iter(&self) -> BitIter<'_, T> {
-        BitIter {
-            cur: None,
-            iter: self.words.iter().enumerate(),
-            marker: PhantomData,
-        }
-    }
-
-    /// Duplicates the set as a hybrid set.
-    pub fn to_hybrid(&self) -> HybridBitSet<T> {
-        // Note: we currently don't bother trying to make a Sparse set.
-        HybridBitSet::Dense(self.to_owned())
-    }
-
-    /// Set `self = self | other`. In contrast to `union` returns `true` if the set contains at
-    /// least one bit that is not in `other` (i.e. `other` is not a superset of `self`).
-    ///
-    /// This is an optimization for union of a hybrid bitset.
-    fn reverse_union_sparse(&mut self, sparse: &SparseBitSet<T>) -> bool {
-        assert!(sparse.domain_size == self.domain_size);
-        self.clear_excess_bits();
-
-        let mut not_already = false;
-        // Index of the current word not yet merged.
-        let mut current_index = 0;
-        // Mask of bits that came from the sparse set in the current word.
-        let mut new_bit_mask = 0;
-        for (word_index, mask) in sparse.iter().map(|x| word_index_and_mask(*x)) {
-            // Next bit is in a word not inspected yet.
-            if word_index > current_index {
-                self.words[current_index] |= new_bit_mask;
-                // Were there any bits in the old word that did not occur in the sparse set?
-                not_already |= (self.words[current_index] ^ new_bit_mask) != 0;
-                // Check all words we skipped for any set bit.
-                not_already |= self.words[current_index+1..word_index].iter().any(|&x| x != 0);
-                // Update next word.
-                current_index = word_index;
-                // Reset bit mask, no bits have been merged yet.
-                new_bit_mask = 0;
-            }
-            // Add bit and mark it as coming from the sparse set.
-            // self.words[word_index] |= mask;
-            new_bit_mask |= mask;
-        }
-        self.words[current_index] |= new_bit_mask;
-        // Any bits in the last inspected word that were not in the sparse set?
-        not_already |= (self.words[current_index] ^ new_bit_mask) != 0;
-        // Any bits in the tail? Note `clear_excess_bits` before.
-        not_already |= self.words[current_index+1..].iter().any(|&x| x != 0);
-
-        not_already
-    }
-}
-
-/// This is implemented by all the bitsets so that BitSet::union() can be
-/// passed any type of bitset.
-pub trait UnionIntoBitSet<T: Idx> {
-    // Performs `other = other | self`.
-    fn union_into(&self, other: &mut BitSet<T>) -> bool;
-}
-
-/// This is implemented by all the bitsets so that BitSet::subtract() can be
-/// passed any type of bitset.
-pub trait SubtractFromBitSet<T: Idx> {
-    // Performs `other = other - self`.
-    fn subtract_from(&self, other: &mut BitSet<T>) -> bool;
-}
-
-impl<T: Idx> UnionIntoBitSet<T> for BitSet<T> {
-    fn union_into(&self, other: &mut BitSet<T>) -> bool {
-        assert_eq!(self.domain_size, other.domain_size);
-        bitwise(&mut other.words, &self.words, |a, b| { a | b })
-    }
-}
-
-impl<T: Idx> SubtractFromBitSet<T> for BitSet<T> {
-    fn subtract_from(&self, other: &mut BitSet<T>) -> bool {
-        assert_eq!(self.domain_size, other.domain_size);
-        bitwise(&mut other.words, &self.words, |a, b| { a & !b })
-    }
-}
-
-impl<T: Idx> fmt::Debug for BitSet<T> {
-    fn fmt(&self, w: &mut fmt::Formatter<'_>) -> fmt::Result {
-        w.debug_list()
-         .entries(self.iter())
-         .finish()
-    }
-}
-
-impl<T: Idx> ToString for BitSet<T> {
-    fn to_string(&self) -> String {
-        let mut result = String::new();
-        let mut sep = '[';
-
-        // Note: this is a little endian printout of bytes.
-
-        // i tracks how many bits we have printed so far.
-        let mut i = 0;
-        for word in &self.words {
-            let mut word = *word;
-            for _ in 0..WORD_BYTES { // for each byte in `word`:
-                let remain = self.domain_size - i;
-                // If less than a byte remains, then mask just that many bits.
-                let mask = if remain <= 8 { (1 << remain) - 1 } else { 0xFF };
-                assert!(mask <= 0xFF);
-                let byte = word & mask;
-
-                result.push_str(&format!("{}{:02x}", sep, byte));
-
-                if remain <= 8 { break; }
-                word >>= 8;
-                i += 8;
-                sep = '-';
-            }
-            sep = '|';
-        }
-        result.push(']');
-
-        result
-    }
-}
-
-pub struct BitIter<'a, T: Idx> {
-    cur: Option<(Word, usize)>,
-    iter: iter::Enumerate<slice::Iter<'a, Word>>,
-    marker: PhantomData<T>
-}
-
-impl<'a, T: Idx> Iterator for BitIter<'a, T> {
-    type Item = T;
-    fn next(&mut self) -> Option<T> {
-        loop {
-            if let Some((ref mut word, offset)) = self.cur {
-                let bit_pos = word.trailing_zeros() as usize;
-                if bit_pos != WORD_BITS {
-                    let bit = 1 << bit_pos;
-                    *word ^= bit;
-                    return Some(T::new(bit_pos + offset))
-                }
-            }
-
-            let (i, word) = self.iter.next()?;
-            self.cur = Some((*word, WORD_BITS * i));
-        }
-    }
-}
-
-#[inline]
-fn bitwise<Op>(out_vec: &mut [Word], in_vec: &[Word], op: Op) -> bool
-    where Op: Fn(Word, Word) -> Word
-{
-    assert_eq!(out_vec.len(), in_vec.len());
-    let mut changed = false;
-    for (out_elem, in_elem) in out_vec.iter_mut().zip(in_vec.iter()) {
-        let old_val = *out_elem;
-        let new_val = op(old_val, *in_elem);
-        *out_elem = new_val;
-        changed |= old_val != new_val;
-    }
-    changed
-}
-
-const SPARSE_MAX: usize = 8;
-
-/// A fixed-size bitset type with a sparse representation and a maximum of
-/// `SPARSE_MAX` elements. The elements are stored as a sorted `SmallVec` with
-/// no duplicates; although `SmallVec` can spill its elements to the heap, that
-/// never happens within this type because of the `SPARSE_MAX` limit.
-///
-/// This type is used by `HybridBitSet`; do not use directly.
-#[derive(Clone, Debug)]
-pub struct SparseBitSet<T: Idx> {
-    domain_size: usize,
-    elems: SmallVec<[T; SPARSE_MAX]>,
-}
-
-impl<T: Idx> SparseBitSet<T> {
-    fn new_empty(domain_size: usize) -> Self {
-        SparseBitSet {
-            domain_size,
-            elems: SmallVec::new()
-        }
-    }
-
-    fn len(&self) -> usize {
-        self.elems.len()
-    }
-
-    fn is_empty(&self) -> bool {
-        self.elems.len() == 0
-    }
-
-    fn contains(&self, elem: T) -> bool {
-        assert!(elem.index() < self.domain_size);
-        self.elems.contains(&elem)
-    }
-
-    fn insert(&mut self, elem: T) -> bool {
-        assert!(elem.index() < self.domain_size);
-        let changed = if let Some(i) = self.elems.iter().position(|&e| e >= elem) {
-            if self.elems[i] == elem {
-                // `elem` is already in the set.
-                false
-            } else {
-                // `elem` is smaller than one or more existing elements.
-                self.elems.insert(i, elem);
-                true
-            }
-        } else {
-            // `elem` is larger than all existing elements.
-            self.elems.push(elem);
-            true
-        };
-        assert!(self.len() <= SPARSE_MAX);
-        changed
-    }
-
-    fn remove(&mut self, elem: T) -> bool {
-        assert!(elem.index() < self.domain_size);
-        if let Some(i) = self.elems.iter().position(|&e| e == elem) {
-            self.elems.remove(i);
-            true
-        } else {
-            false
-        }
-    }
-
-    fn to_dense(&self) -> BitSet<T> {
-        let mut dense = BitSet::new_empty(self.domain_size);
-        for elem in self.elems.iter() {
-            dense.insert(*elem);
-        }
-        dense
-    }
-
-    fn iter(&self) -> slice::Iter<'_, T> {
-        self.elems.iter()
-    }
-}
-
-impl<T: Idx> UnionIntoBitSet<T> for SparseBitSet<T> {
-    fn union_into(&self, other: &mut BitSet<T>) -> bool {
-        assert_eq!(self.domain_size, other.domain_size);
-        let mut changed = false;
-        for elem in self.iter() {
-            changed |= other.insert(*elem);
-        }
-        changed
-    }
-}
-
-impl<T: Idx> SubtractFromBitSet<T> for SparseBitSet<T> {
-    fn subtract_from(&self, other: &mut BitSet<T>) -> bool {
-        assert_eq!(self.domain_size, other.domain_size);
-        let mut changed = false;
-        for elem in self.iter() {
-            changed |= other.remove(*elem);
-        }
-        changed
-    }
-}
-
-/// A fixed-size bitset type with a hybrid representation: sparse when there
-/// are up to a `SPARSE_MAX` elements in the set, but dense when there are more
-/// than `SPARSE_MAX`.
-///
-/// This type is especially efficient for sets that typically have a small
-/// number of elements, but a large `domain_size`, and are cleared frequently.
-///
-/// `T` is an index type, typically a newtyped `usize` wrapper, but it can also
-/// just be `usize`.
-///
-/// All operations that involve an element will panic if the element is equal
-/// to or greater than the domain size. All operations that involve two bitsets
-/// will panic if the bitsets have differing domain sizes.
-#[derive(Clone, Debug)]
-pub enum HybridBitSet<T: Idx> {
-    Sparse(SparseBitSet<T>),
-    Dense(BitSet<T>),
-}
-
-impl<T: Idx> HybridBitSet<T> {
-    pub fn new_empty(domain_size: usize) -> Self {
-        HybridBitSet::Sparse(SparseBitSet::new_empty(domain_size))
-    }
-
-    fn domain_size(&self) -> usize {
-        match self {
-            HybridBitSet::Sparse(sparse) => sparse.domain_size,
-            HybridBitSet::Dense(dense) => dense.domain_size,
-        }
-    }
-
-    pub fn clear(&mut self) {
-        let domain_size = self.domain_size();
-        *self = HybridBitSet::new_empty(domain_size);
-    }
-
-    pub fn contains(&self, elem: T) -> bool {
-        match self {
-            HybridBitSet::Sparse(sparse) => sparse.contains(elem),
-            HybridBitSet::Dense(dense) => dense.contains(elem),
-        }
-    }
-
-    pub fn superset(&self, other: &HybridBitSet<T>) -> bool {
-        match (self, other) {
-            (HybridBitSet::Dense(self_dense), HybridBitSet::Dense(other_dense)) => {
-                self_dense.superset(other_dense)
-            }
-            _ => {
-                assert!(self.domain_size() == other.domain_size());
-                other.iter().all(|elem| self.contains(elem))
-            }
-        }
-    }
-
-    pub fn is_empty(&self) -> bool {
-        match self {
-            HybridBitSet::Sparse(sparse) => sparse.is_empty(),
-            HybridBitSet::Dense(dense) => dense.is_empty(),
-        }
-    }
-
-    pub fn insert(&mut self, elem: T) -> bool {
-        // No need to check `elem` against `self.domain_size` here because all
-        // the match cases check it, one way or another.
-        match self {
-            HybridBitSet::Sparse(sparse) if sparse.len() < SPARSE_MAX => {
-                // The set is sparse and has space for `elem`.
-                sparse.insert(elem)
-            }
-            HybridBitSet::Sparse(sparse) if sparse.contains(elem) => {
-                // The set is sparse and does not have space for `elem`, but
-                // that doesn't matter because `elem` is already present.
-                false
-            }
-            HybridBitSet::Sparse(sparse) => {
-                // The set is sparse and full. Convert to a dense set.
-                let mut dense = sparse.to_dense();
-                let changed = dense.insert(elem);
-                assert!(changed);
-                *self = HybridBitSet::Dense(dense);
-                changed
-            }
-            HybridBitSet::Dense(dense) => dense.insert(elem),
-        }
-    }
-
-    pub fn insert_all(&mut self) {
-        let domain_size = self.domain_size();
-        match self {
-            HybridBitSet::Sparse(_) => {
-                *self = HybridBitSet::Dense(BitSet::new_filled(domain_size));
-            }
-            HybridBitSet::Dense(dense) => dense.insert_all(),
-        }
-    }
-
-    pub fn remove(&mut self, elem: T) -> bool {
-        // Note: we currently don't bother going from Dense back to Sparse.
-        match self {
-            HybridBitSet::Sparse(sparse) => sparse.remove(elem),
-            HybridBitSet::Dense(dense) => dense.remove(elem),
-        }
-    }
-
-    pub fn union(&mut self, other: &HybridBitSet<T>) -> bool {
-        match self {
-            HybridBitSet::Sparse(self_sparse) => {
-                match other {
-                    HybridBitSet::Sparse(other_sparse) => {
-                        // Both sets are sparse. Add the elements in
-                        // `other_sparse` to `self` one at a time. This
-                        // may or may not cause `self` to be densified.
-                        assert_eq!(self.domain_size(), other.domain_size());
-                        let mut changed = false;
-                        for elem in other_sparse.iter() {
-                            changed |= self.insert(*elem);
-                        }
-                        changed
-                    }
-                    HybridBitSet::Dense(other_dense) => {
-                        // `self` is sparse and `other` is dense. To
-                        // merge them, we have two available strategies:
-                        // * Densify `self` then merge other
-                        // * Clone other then integrate bits from `self`
-                        // The second strategy requires dedicated method
-                        // since the usual `union` returns the wrong
-                        // result. In the dedicated case the computation
-                        // is slightly faster if the bits of the sparse
-                        // bitset map to only few words of the dense
-                        // representation, i.e. indices are near each
-                        // other.
-                        //
-                        // Benchmarking seems to suggest that the second
-                        // option is worth it.
-                        let mut new_dense = other_dense.clone();
-                        let changed = new_dense.reverse_union_sparse(self_sparse);
-                        *self = HybridBitSet::Dense(new_dense);
-                        changed
-                    }
-                }
-            }
-
-            HybridBitSet::Dense(self_dense) => self_dense.union(other),
-        }
-    }
-
-    /// Converts to a dense set, consuming itself in the process.
-    pub fn to_dense(self) -> BitSet<T> {
-        match self {
-            HybridBitSet::Sparse(sparse) => sparse.to_dense(),
-            HybridBitSet::Dense(dense) => dense,
-        }
-    }
-
-    pub fn iter(&self) -> HybridIter<'_, T> {
-        match self {
-            HybridBitSet::Sparse(sparse) => HybridIter::Sparse(sparse.iter()),
-            HybridBitSet::Dense(dense) => HybridIter::Dense(dense.iter()),
-        }
-    }
-}
-
-impl<T: Idx> UnionIntoBitSet<T> for HybridBitSet<T> {
-    fn union_into(&self, other: &mut BitSet<T>) -> bool {
-        match self {
-            HybridBitSet::Sparse(sparse) => sparse.union_into(other),
-            HybridBitSet::Dense(dense) => dense.union_into(other),
-        }
-    }
-}
-
-impl<T: Idx> SubtractFromBitSet<T> for HybridBitSet<T> {
-    fn subtract_from(&self, other: &mut BitSet<T>) -> bool {
-        match self {
-            HybridBitSet::Sparse(sparse) => sparse.subtract_from(other),
-            HybridBitSet::Dense(dense) => dense.subtract_from(other),
-        }
-    }
-}
-
-pub enum HybridIter<'a, T: Idx> {
-    Sparse(slice::Iter<'a, T>),
-    Dense(BitIter<'a, T>),
-}
-
-impl<'a, T: Idx> Iterator for HybridIter<'a, T> {
-    type Item = T;
-
-    fn next(&mut self) -> Option<T> {
-        match self {
-            HybridIter::Sparse(sparse) => sparse.next().map(|e| *e),
-            HybridIter::Dense(dense) => dense.next(),
-        }
-    }
-}
-
-/// A resizable bitset type with a dense representation.
-///
-/// `T` is an index type, typically a newtyped `usize` wrapper, but it can also
-/// just be `usize`.
-///
-/// All operations that involve an element will panic if the element is equal
-/// to or greater than the domain size.
-#[derive(Clone, Debug, PartialEq)]
-pub struct GrowableBitSet<T: Idx> {
-    bit_set: BitSet<T>,
-}
-
-impl<T: Idx> GrowableBitSet<T> {
-    /// Ensure that the set can hold at least `min_domain_size` elements.
-    pub fn ensure(&mut self, min_domain_size: usize) {
-        if self.bit_set.domain_size < min_domain_size {
-            self.bit_set.domain_size = min_domain_size;
-        }
-
-        let min_num_words = num_words(min_domain_size);
-        if self.bit_set.words.len() < min_num_words {
-            self.bit_set.words.resize(min_num_words, 0)
-        }
-    }
-
-    pub fn new_empty() -> GrowableBitSet<T> {
-        GrowableBitSet { bit_set: BitSet::new_empty(0) }
-    }
-
-    pub fn with_capacity(capacity: usize) -> GrowableBitSet<T> {
-        GrowableBitSet { bit_set: BitSet::new_empty(capacity) }
-    }
-
-    /// Returns `true` if the set has changed.
-    #[inline]
-    pub fn insert(&mut self, elem: T) -> bool {
-        self.ensure(elem.index() + 1);
-        self.bit_set.insert(elem)
-    }
-
-    #[inline]
-    pub fn contains(&self, elem: T) -> bool {
-        let (word_index, mask) = word_index_and_mask(elem);
-        if let Some(word) = self.bit_set.words.get(word_index) {
-            (word & mask) != 0
-        } else {
-            false
-        }
-    }
-}
-
-/// A fixed-size 2D bit matrix type with a dense representation.
-///
-/// `R` and `C` are index types used to identify rows and columns respectively;
-/// typically newtyped `usize` wrappers, but they can also just be `usize`.
-///
-/// All operations that involve a row and/or column index will panic if the
-/// index exceeds the relevant bound.
-#[derive(Clone, Debug, Eq, PartialEq, RustcDecodable, RustcEncodable)]
-pub struct BitMatrix<R: Idx, C: Idx> {
-    num_rows: usize,
-    num_columns: usize,
-    words: Vec<Word>,
-    marker: PhantomData<(R, C)>,
-}
-
-impl<R: Idx, C: Idx> BitMatrix<R, C> {
-    /// Creates a new `rows x columns` matrix, initially empty.
-    pub fn new(num_rows: usize, num_columns: usize) -> BitMatrix<R, C> {
-        // For every element, we need one bit for every other
-        // element. Round up to an even number of words.
-        let words_per_row = num_words(num_columns);
-        BitMatrix {
-            num_rows,
-            num_columns,
-            words: vec![0; num_rows * words_per_row],
-            marker: PhantomData,
-        }
-    }
-
-    /// Creates a new matrix, with `row` used as the value for every row.
-    pub fn from_row_n(row: &BitSet<C>, num_rows: usize) -> BitMatrix<R, C> {
-        let num_columns = row.domain_size();
-        let words_per_row = num_words(num_columns);
-        assert_eq!(words_per_row, row.words().len());
-        BitMatrix {
-            num_rows,
-            num_columns,
-            words: iter::repeat(row.words()).take(num_rows).flatten().cloned().collect(),
-            marker: PhantomData,
-        }
-    }
-
-    pub fn rows(&self) -> impl Iterator<Item = R> {
-        (0..self.num_rows).map(R::new)
-    }
-
-    /// The range of bits for a given row.
-    fn range(&self, row: R) -> (usize, usize) {
-        let words_per_row = num_words(self.num_columns);
-        let start = row.index() * words_per_row;
-        (start, start + words_per_row)
-    }
-
-    /// Sets the cell at `(row, column)` to true. Put another way, insert
-    /// `column` to the bitset for `row`.
-    ///
-    /// Returns `true` if this changed the matrix.
-    pub fn insert(&mut self, row: R, column: C) -> bool {
-        assert!(row.index() < self.num_rows && column.index() < self.num_columns);
-        let (start, _) = self.range(row);
-        let (word_index, mask) = word_index_and_mask(column);
-        let words = &mut self.words[..];
-        let word = words[start + word_index];
-        let new_word = word | mask;
-        words[start + word_index] = new_word;
-        word != new_word
-    }
-
-    /// Do the bits from `row` contain `column`? Put another way, is
-    /// the matrix cell at `(row, column)` true?  Put yet another way,
-    /// if the matrix represents (transitive) reachability, can
-    /// `row` reach `column`?
-    pub fn contains(&self, row: R, column: C) -> bool {
-        assert!(row.index() < self.num_rows && column.index() < self.num_columns);
-        let (start, _) = self.range(row);
-        let (word_index, mask) = word_index_and_mask(column);
-        (self.words[start + word_index] & mask) != 0
-    }
-
-    /// Returns those indices that are true in rows `a` and `b`. This
-    /// is an O(n) operation where `n` is the number of elements
-    /// (somewhat independent from the actual size of the
-    /// intersection, in particular).
-    pub fn intersect_rows(&self, row1: R, row2: R) -> Vec<C> {
-        assert!(row1.index() < self.num_rows && row2.index() < self.num_rows);
-        let (row1_start, row1_end) = self.range(row1);
-        let (row2_start, row2_end) = self.range(row2);
-        let mut result = Vec::with_capacity(self.num_columns);
-        for (base, (i, j)) in (row1_start..row1_end).zip(row2_start..row2_end).enumerate() {
-            let mut v = self.words[i] & self.words[j];
-            for bit in 0..WORD_BITS {
-                if v == 0 {
-                    break;
-                }
-                if v & 0x1 != 0 {
-                    result.push(C::new(base * WORD_BITS + bit));
-                }
-                v >>= 1;
-            }
-        }
-        result
-    }
-
-    /// Adds the bits from row `read` to the bits from row `write`, and
-    /// returns `true` if anything changed.
-    ///
-    /// This is used when computing transitive reachability because if
-    /// you have an edge `write -> read`, because in that case
-    /// `write` can reach everything that `read` can (and
-    /// potentially more).
-    pub fn union_rows(&mut self, read: R, write: R) -> bool {
-        assert!(read.index() < self.num_rows && write.index() < self.num_rows);
-        let (read_start, read_end) = self.range(read);
-        let (write_start, write_end) = self.range(write);
-        let words = &mut self.words[..];
-        let mut changed = false;
-        for (read_index, write_index) in (read_start..read_end).zip(write_start..write_end) {
-            let word = words[write_index];
-            let new_word = word | words[read_index];
-            words[write_index] = new_word;
-            changed |= word != new_word;
-        }
-        changed
-    }
-
-    /// Adds the bits from `with` to the bits from row `write`, and
-    /// returns `true` if anything changed.
-    pub fn union_row_with(&mut self, with: &BitSet<C>, write: R) -> bool {
-        assert!(write.index() < self.num_rows);
-        assert_eq!(with.domain_size(), self.num_columns);
-        let (write_start, write_end) = self.range(write);
-        let mut changed = false;
-        for (read_index, write_index) in (0..with.words().len()).zip(write_start..write_end) {
-            let word = self.words[write_index];
-            let new_word = word | with.words()[read_index];
-            self.words[write_index] = new_word;
-            changed |= word != new_word;
-        }
-        changed
-    }
-
-    /// Sets every cell in `row` to true.
-    pub fn insert_all_into_row(&mut self, row: R) {
-        assert!(row.index() < self.num_rows);
-        let (start, end) = self.range(row);
-        let words = &mut self.words[..];
-        for index in start..end {
-            words[index] = !0;
-        }
-        self.clear_excess_bits(row);
-    }
-
-    /// Clear excess bits in the final word of the row.
-    fn clear_excess_bits(&mut self, row: R) {
-        let num_bits_in_final_word = self.num_columns % WORD_BITS;
-        if num_bits_in_final_word > 0 {
-            let mask = (1 << num_bits_in_final_word) - 1;
-            let (_, end) = self.range(row);
-            let final_word_idx = end - 1;
-            self.words[final_word_idx] &= mask;
-        }
-    }
-
-    /// Gets a slice of the underlying words.
-    pub fn words(&self) -> &[Word] {
-        &self.words
-    }
-
-    /// Iterates through all the columns set to true in a given row of
-    /// the matrix.
-    pub fn iter(&self, row: R) -> BitIter<'_, C> {
-        assert!(row.index() < self.num_rows);
-        let (start, end) = self.range(row);
-        BitIter {
-            cur: None,
-            iter: self.words[start..end].iter().enumerate(),
-            marker: PhantomData,
-        }
-    }
-
-    /// Returns the number of elements in `row`.
-    pub fn count(&self, row: R) -> usize {
-        let (start, end) = self.range(row);
-        self.words[start..end].iter().map(|e| e.count_ones() as usize).sum()
-    }
-}
-
-/// A fixed-column-size, variable-row-size 2D bit matrix with a moderately
-/// sparse representation.
-///
-/// Initially, every row has no explicit representation. If any bit within a
-/// row is set, the entire row is instantiated as `Some(<HybridBitSet>)`.
-/// Furthermore, any previously uninstantiated rows prior to it will be
-/// instantiated as `None`. Those prior rows may themselves become fully
-/// instantiated later on if any of their bits are set.
-///
-/// `R` and `C` are index types used to identify rows and columns respectively;
-/// typically newtyped `usize` wrappers, but they can also just be `usize`.
-#[derive(Clone, Debug)]
-pub struct SparseBitMatrix<R, C>
-where
-    R: Idx,
-    C: Idx,
-{
-    num_columns: usize,
-    rows: IndexVec<R, Option<HybridBitSet<C>>>,
-}
-
-impl<R: Idx, C: Idx> SparseBitMatrix<R, C> {
-    /// Creates a new empty sparse bit matrix with no rows or columns.
-    pub fn new(num_columns: usize) -> Self {
-        Self {
-            num_columns,
-            rows: IndexVec::new(),
-        }
-    }
-
-    fn ensure_row(&mut self, row: R) -> &mut HybridBitSet<C> {
-        // Instantiate any missing rows up to and including row `row` with an
-        // empty HybridBitSet.
-        self.rows.ensure_contains_elem(row, || None);
-
-        // Then replace row `row` with a full HybridBitSet if necessary.
-        let num_columns = self.num_columns;
-        self.rows[row].get_or_insert_with(|| HybridBitSet::new_empty(num_columns))
-    }
-
-    /// Sets the cell at `(row, column)` to true. Put another way, insert
-    /// `column` to the bitset for `row`.
-    ///
-    /// Returns `true` if this changed the matrix.
-    pub fn insert(&mut self, row: R, column: C) -> bool {
-        self.ensure_row(row).insert(column)
-    }
-
-    /// Do the bits from `row` contain `column`? Put another way, is
-    /// the matrix cell at `(row, column)` true?  Put yet another way,
-    /// if the matrix represents (transitive) reachability, can
-    /// `row` reach `column`?
-    pub fn contains(&self, row: R, column: C) -> bool {
-        self.row(row).map_or(false, |r| r.contains(column))
-    }
-
-    /// Adds the bits from row `read` to the bits from row `write`, and
-    /// returns `true` if anything changed.
-    ///
-    /// This is used when computing transitive reachability because if
-    /// you have an edge `write -> read`, because in that case
-    /// `write` can reach everything that `read` can (and
-    /// potentially more).
-    pub fn union_rows(&mut self, read: R, write: R) -> bool {
-        if read == write || self.row(read).is_none() {
-            return false;
-        }
-
-        self.ensure_row(write);
-        if let (Some(read_row), Some(write_row)) = self.rows.pick2_mut(read, write) {
-            write_row.union(read_row)
-        } else {
-            unreachable!()
-        }
-    }
-
-    /// Union a row, `from`, into the `into` row.
-    pub fn union_into_row(&mut self, into: R, from: &HybridBitSet<C>) -> bool {
-        self.ensure_row(into).union(from)
-    }
-
-    /// Insert all bits in the given row.
-    pub fn insert_all_into_row(&mut self, row: R) {
-        self.ensure_row(row).insert_all();
-    }
-
-    pub fn rows(&self) -> impl Iterator<Item = R> {
-        self.rows.indices()
-    }
-
-    /// Iterates through all the columns set to true in a given row of
-    /// the matrix.
-    pub fn iter<'a>(&'a self, row: R) -> impl Iterator<Item = C> + 'a {
-        self.row(row).into_iter().flat_map(|r| r.iter())
-    }
-
-    pub fn row(&self, row: R) -> Option<&HybridBitSet<C>> {
-        if let Some(Some(row)) = self.rows.get(row) {
-            Some(row)
-        } else {
-            None
-        }
-    }
-}
-
-#[inline]
-fn num_words<T: Idx>(domain_size: T) -> usize {
-    (domain_size.index() + WORD_BITS - 1) / WORD_BITS
-}
-
-#[inline]
-fn word_index_and_mask<T: Idx>(elem: T) -> (usize, Word) {
-    let elem = elem.index();
-    let word_index = elem / WORD_BITS;
-    let mask = 1 << (elem % WORD_BITS);
-    (word_index, mask)
-}
diff --git a/src/librustc_data_structures/bit_set/tests.rs b/src/librustc_data_structures/bit_set/tests.rs
deleted file mode 100644
index ac7913815ff..00000000000
--- a/src/librustc_data_structures/bit_set/tests.rs
+++ /dev/null
@@ -1,369 +0,0 @@
-use super::*;
-
-extern crate test;
-use test::Bencher;
-
-#[test]
-fn test_new_filled() {
-    for i in 0..128 {
-        let idx_buf = BitSet::new_filled(i);
-        let elems: Vec<usize> = idx_buf.iter().collect();
-        let expected: Vec<usize> = (0..i).collect();
-        assert_eq!(elems, expected);
-    }
-}
-
-#[test]
-fn bitset_iter_works() {
-    let mut bitset: BitSet<usize> = BitSet::new_empty(100);
-    bitset.insert(1);
-    bitset.insert(10);
-    bitset.insert(19);
-    bitset.insert(62);
-    bitset.insert(63);
-    bitset.insert(64);
-    bitset.insert(65);
-    bitset.insert(66);
-    bitset.insert(99);
-    assert_eq!(
-        bitset.iter().collect::<Vec<_>>(),
-        [1, 10, 19, 62, 63, 64, 65, 66, 99]
-    );
-}
-
-#[test]
-fn bitset_iter_works_2() {
-    let mut bitset: BitSet<usize> = BitSet::new_empty(320);
-    bitset.insert(0);
-    bitset.insert(127);
-    bitset.insert(191);
-    bitset.insert(255);
-    bitset.insert(319);
-    assert_eq!(bitset.iter().collect::<Vec<_>>(), [0, 127, 191, 255, 319]);
-}
-
-#[test]
-fn union_two_sets() {
-    let mut set1: BitSet<usize> = BitSet::new_empty(65);
-    let mut set2: BitSet<usize> = BitSet::new_empty(65);
-    assert!(set1.insert(3));
-    assert!(!set1.insert(3));
-    assert!(set2.insert(5));
-    assert!(set2.insert(64));
-    assert!(set1.union(&set2));
-    assert!(!set1.union(&set2));
-    assert!(set1.contains(3));
-    assert!(!set1.contains(4));
-    assert!(set1.contains(5));
-    assert!(!set1.contains(63));
-    assert!(set1.contains(64));
-}
-
-#[test]
-fn hybrid_bitset() {
-    let mut sparse038: HybridBitSet<usize> = HybridBitSet::new_empty(256);
-    assert!(sparse038.is_empty());
-    assert!(sparse038.insert(0));
-    assert!(sparse038.insert(1));
-    assert!(sparse038.insert(8));
-    assert!(sparse038.insert(3));
-    assert!(!sparse038.insert(3));
-    assert!(sparse038.remove(1));
-    assert!(!sparse038.is_empty());
-    assert_eq!(sparse038.iter().collect::<Vec<_>>(), [0, 3, 8]);
-
-    for i in 0..256 {
-        if i == 0 || i == 3 || i == 8 {
-            assert!(sparse038.contains(i));
-        } else {
-            assert!(!sparse038.contains(i));
-        }
-    }
-
-    let mut sparse01358 = sparse038.clone();
-    assert!(sparse01358.insert(1));
-    assert!(sparse01358.insert(5));
-    assert_eq!(sparse01358.iter().collect::<Vec<_>>(), [0, 1, 3, 5, 8]);
-
-    let mut dense10 = HybridBitSet::new_empty(256);
-    for i in 0..10 {
-        assert!(dense10.insert(i));
-    }
-    assert!(!dense10.is_empty());
-    assert_eq!(dense10.iter().collect::<Vec<_>>(), [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
-
-    let mut dense256 = HybridBitSet::new_empty(256);
-    assert!(dense256.is_empty());
-    dense256.insert_all();
-    assert!(!dense256.is_empty());
-    for i in 0..256 {
-        assert!(dense256.contains(i));
-    }
-
-    assert!(sparse038.superset(&sparse038));    // sparse + sparse (self)
-    assert!(sparse01358.superset(&sparse038));  // sparse + sparse
-    assert!(dense10.superset(&sparse038));      // dense + sparse
-    assert!(dense10.superset(&dense10));        // dense + dense (self)
-    assert!(dense256.superset(&dense10));       // dense + dense
-
-    let mut hybrid = sparse038;
-    assert!(!sparse01358.union(&hybrid));       // no change
-    assert!(hybrid.union(&sparse01358));
-    assert!(hybrid.superset(&sparse01358) && sparse01358.superset(&hybrid));
-    assert!(!dense10.union(&sparse01358));
-    assert!(!dense256.union(&dense10));
-    let mut dense = dense10;
-    assert!(dense.union(&dense256));
-    assert!(dense.superset(&dense256) && dense256.superset(&dense));
-    assert!(hybrid.union(&dense256));
-    assert!(hybrid.superset(&dense256) && dense256.superset(&hybrid));
-
-    assert_eq!(dense256.iter().count(), 256);
-    let mut dense0 = dense256;
-    for i in 0..256 {
-        assert!(dense0.remove(i));
-    }
-    assert!(!dense0.remove(0));
-    assert!(dense0.is_empty());
-}
-
-#[test]
-fn grow() {
-    let mut set: GrowableBitSet<usize> = GrowableBitSet::with_capacity(65);
-    for index in 0..65 {
-        assert!(set.insert(index));
-        assert!(!set.insert(index));
-    }
-    set.ensure(128);
-
-    // Check if the bits set before growing are still set
-    for index in 0..65 {
-        assert!(set.contains(index));
-    }
-
-    // Check if the new bits are all un-set
-    for index in 65..128 {
-        assert!(!set.contains(index));
-    }
-
-    // Check that we can set all new bits without running out of bounds
-    for index in 65..128 {
-        assert!(set.insert(index));
-        assert!(!set.insert(index));
-    }
-}
-
-#[test]
-fn matrix_intersection() {
-    let mut matrix: BitMatrix<usize, usize> = BitMatrix::new(200, 200);
-
-    // (*) Elements reachable from both 2 and 65.
-
-    matrix.insert(2, 3);
-    matrix.insert(2, 6);
-    matrix.insert(2, 10); // (*)
-    matrix.insert(2, 64); // (*)
-    matrix.insert(2, 65);
-    matrix.insert(2, 130);
-    matrix.insert(2, 160); // (*)
-
-    matrix.insert(64, 133);
-
-    matrix.insert(65, 2);
-    matrix.insert(65, 8);
-    matrix.insert(65, 10); // (*)
-    matrix.insert(65, 64); // (*)
-    matrix.insert(65, 68);
-    matrix.insert(65, 133);
-    matrix.insert(65, 160); // (*)
-
-    let intersection = matrix.intersect_rows(2, 64);
-    assert!(intersection.is_empty());
-
-    let intersection = matrix.intersect_rows(2, 65);
-    assert_eq!(intersection, &[10, 64, 160]);
-}
-
-#[test]
-fn matrix_iter() {
-    let mut matrix: BitMatrix<usize, usize> = BitMatrix::new(64, 100);
-    matrix.insert(3, 22);
-    matrix.insert(3, 75);
-    matrix.insert(2, 99);
-    matrix.insert(4, 0);
-    matrix.union_rows(3, 5);
-    matrix.insert_all_into_row(6);
-
-    let expected = [99];
-    let mut iter = expected.iter();
-    for i in matrix.iter(2) {
-        let j = *iter.next().unwrap();
-        assert_eq!(i, j);
-    }
-    assert!(iter.next().is_none());
-
-    let expected = [22, 75];
-    let mut iter = expected.iter();
-    assert_eq!(matrix.count(3), expected.len());
-    for i in matrix.iter(3) {
-        let j = *iter.next().unwrap();
-        assert_eq!(i, j);
-    }
-    assert!(iter.next().is_none());
-
-    let expected = [0];
-    let mut iter = expected.iter();
-    assert_eq!(matrix.count(4), expected.len());
-    for i in matrix.iter(4) {
-        let j = *iter.next().unwrap();
-        assert_eq!(i, j);
-    }
-    assert!(iter.next().is_none());
-
-    let expected = [22, 75];
-    let mut iter = expected.iter();
-    assert_eq!(matrix.count(5), expected.len());
-    for i in matrix.iter(5) {
-        let j = *iter.next().unwrap();
-        assert_eq!(i, j);
-    }
-    assert!(iter.next().is_none());
-
-    assert_eq!(matrix.count(6), 100);
-    let mut count = 0;
-    for (idx, i) in matrix.iter(6).enumerate() {
-        assert_eq!(idx, i);
-        count += 1;
-    }
-    assert_eq!(count, 100);
-
-    if let Some(i) = matrix.iter(7).next() {
-        panic!("expected no elements in row, but contains element {:?}", i);
-    }
-}
-
-#[test]
-fn sparse_matrix_iter() {
-    let mut matrix: SparseBitMatrix<usize, usize> = SparseBitMatrix::new(100);
-    matrix.insert(3, 22);
-    matrix.insert(3, 75);
-    matrix.insert(2, 99);
-    matrix.insert(4, 0);
-    matrix.union_rows(3, 5);
-
-    let expected = [99];
-    let mut iter = expected.iter();
-    for i in matrix.iter(2) {
-        let j = *iter.next().unwrap();
-        assert_eq!(i, j);
-    }
-    assert!(iter.next().is_none());
-
-    let expected = [22, 75];
-    let mut iter = expected.iter();
-    for i in matrix.iter(3) {
-        let j = *iter.next().unwrap();
-        assert_eq!(i, j);
-    }
-    assert!(iter.next().is_none());
-
-    let expected = [0];
-    let mut iter = expected.iter();
-    for i in matrix.iter(4) {
-        let j = *iter.next().unwrap();
-        assert_eq!(i, j);
-    }
-    assert!(iter.next().is_none());
-
-    let expected = [22, 75];
-    let mut iter = expected.iter();
-    for i in matrix.iter(5) {
-        let j = *iter.next().unwrap();
-        assert_eq!(i, j);
-    }
-    assert!(iter.next().is_none());
-}
-
-/// Merge dense hybrid set into empty sparse hybrid set.
-#[bench]
-fn union_hybrid_sparse_empty_to_dense(b: &mut Bencher) {
-    let mut pre_dense: HybridBitSet<usize> = HybridBitSet::new_empty(256);
-    for i in 0..10 {
-        assert!(pre_dense.insert(i));
-    }
-    let pre_sparse: HybridBitSet<usize> = HybridBitSet::new_empty(256);
-    b.iter(|| {
-        let dense = pre_dense.clone();
-        let mut sparse = pre_sparse.clone();
-        sparse.union(&dense);
-    })
-}
-
-/// Merge dense hybrid set into full hybrid set with same indices.
-#[bench]
-fn union_hybrid_sparse_full_to_dense(b: &mut Bencher) {
-    let mut pre_dense: HybridBitSet<usize> = HybridBitSet::new_empty(256);
-    for i in 0..10 {
-        assert!(pre_dense.insert(i));
-    }
-    let mut pre_sparse: HybridBitSet<usize> = HybridBitSet::new_empty(256);
-    for i in 0..SPARSE_MAX {
-        assert!(pre_sparse.insert(i));
-    }
-    b.iter(|| {
-        let dense = pre_dense.clone();
-        let mut sparse = pre_sparse.clone();
-        sparse.union(&dense);
-    })
-}
-
-/// Merge dense hybrid set into full hybrid set with indices over the whole domain.
-#[bench]
-fn union_hybrid_sparse_domain_to_dense(b: &mut Bencher) {
-    let mut pre_dense: HybridBitSet<usize> = HybridBitSet::new_empty(SPARSE_MAX*64);
-    for i in 0..10 {
-        assert!(pre_dense.insert(i));
-    }
-    let mut pre_sparse: HybridBitSet<usize> = HybridBitSet::new_empty(SPARSE_MAX*64);
-    for i in 0..SPARSE_MAX {
-        assert!(pre_sparse.insert(i*64));
-    }
-    b.iter(|| {
-        let dense = pre_dense.clone();
-        let mut sparse = pre_sparse.clone();
-        sparse.union(&dense);
-    })
-}
-
-/// Merge dense hybrid set into empty hybrid set where the domain is very small.
-#[bench]
-fn union_hybrid_sparse_empty_small_domain(b: &mut Bencher) {
-    let mut pre_dense: HybridBitSet<usize> = HybridBitSet::new_empty(SPARSE_MAX);
-    for i in 0..SPARSE_MAX {
-        assert!(pre_dense.insert(i));
-    }
-    let pre_sparse: HybridBitSet<usize> = HybridBitSet::new_empty(SPARSE_MAX);
-    b.iter(|| {
-        let dense = pre_dense.clone();
-        let mut sparse = pre_sparse.clone();
-        sparse.union(&dense);
-    })
-}
-
-/// Merge dense hybrid set into full hybrid set where the domain is very small.
-#[bench]
-fn union_hybrid_sparse_full_small_domain(b: &mut Bencher) {
-    let mut pre_dense: HybridBitSet<usize> = HybridBitSet::new_empty(SPARSE_MAX);
-    for i in 0..SPARSE_MAX {
-        assert!(pre_dense.insert(i));
-    }
-    let mut pre_sparse: HybridBitSet<usize> = HybridBitSet::new_empty(SPARSE_MAX);
-    for i in 0..SPARSE_MAX {
-        assert!(pre_sparse.insert(i));
-    }
-    b.iter(|| {
-        let dense = pre_dense.clone();
-        let mut sparse = pre_sparse.clone();
-        sparse.union(&dense);
-    })
-}
diff --git a/src/librustc_data_structures/lib.rs b/src/librustc_data_structures/lib.rs
index a9ef297fa99..e28ee48201c 100644
--- a/src/librustc_data_structures/lib.rs
+++ b/src/librustc_data_structures/lib.rs
@@ -37,7 +37,7 @@ extern crate libc;
 extern crate cfg_if;
 
 pub use rustc_serialize::hex::ToHex;
-pub use rustc_index::{indexed_vec, newtype_index};
+pub use rustc_index::{bit_set, indexed_vec, newtype_index};
 
 #[inline(never)]
 #[cold]
@@ -69,7 +69,6 @@ pub mod macros;
 pub mod svh;
 pub mod base_n;
 pub mod binary_search_util;
-pub mod bit_set;
 pub mod box_region;
 pub mod const_cstr;
 pub mod flock;