Remove ChunkedBitSet impls that are no longer needed.

`ChunkedBitSet` is no longer used directly by dataflow analyses, with
`MixedBitSet` replacing it in those contexts.

compiler/rustc_mir_dataflow/src/framework/lattice.rs

@@ -40,7 +40,7 @@
 
 use std::iter;
 
-use rustc_index::bit_set::{BitSet, ChunkedBitSet, MixedBitSet};
+use rustc_index::bit_set::{BitSet, MixedBitSet};
 use rustc_index::{Idx, IndexVec};
 
 use crate::framework::BitSetExt;
@@ -126,12 +126,6 @@ impl<T: Idx> JoinSemiLattice for BitSet<T> {
     }
 }
 
-impl<T: Idx> JoinSemiLattice for ChunkedBitSet<T> {
-    fn join(&mut self, other: &Self) -> bool {
-        self.union(other)
-    }
-}
-
 impl<T: Idx> JoinSemiLattice for MixedBitSet<T> {
     fn join(&mut self, other: &Self) -> bool {
         self.union(other)

compiler/rustc_mir_dataflow/src/framework/mod.rs

@@ -35,7 +35,7 @@
 use std::cmp::Ordering;
 
 use rustc_data_structures::work_queue::WorkQueue;
-use rustc_index::bit_set::{BitSet, ChunkedBitSet, MixedBitSet};
+use rustc_index::bit_set::{BitSet, MixedBitSet};
 use rustc_index::{Idx, IndexVec};
 use rustc_middle::bug;
 use rustc_middle::mir::{self, BasicBlock, CallReturnPlaces, Location, TerminatorEdges, traversal};
@@ -71,12 +71,6 @@ impl<T: Idx> BitSetExt<T> for BitSet<T> {
     }
 }
 
-impl<T: Idx> BitSetExt<T> for ChunkedBitSet<T> {
-    fn contains(&self, elem: T) -> bool {
-        self.contains(elem)
-    }
-}
-
 impl<T: Idx> BitSetExt<T> for MixedBitSet<T> {
     fn contains(&self, elem: T) -> bool {
         self.contains(elem)
@@ -333,16 +327,6 @@ impl<T: Idx> GenKill<T> for BitSet<T> {
     }
 }
 
-impl<T: Idx> GenKill<T> for ChunkedBitSet<T> {
-    fn gen_(&mut self, elem: T) {
-        self.insert(elem);
-    }
-
-    fn kill(&mut self, elem: T) {
-        self.remove(elem);
-    }
-}
-
 impl<T: Idx> GenKill<T> for MixedBitSet<T> {
     fn gen_(&mut self, elem: T) {
         self.insert(elem);