Move `DataFlowState::{each_bit,interpret_set}` method definitions to parent module.

Refactored `each_bit`, which traverses a `IdxSet`, so that the bulk of
its implementation lives in `rustc_data_structures`.

src/librustc_data_structures/indexed_set.rs

@@ -153,4 +153,38 @@ pub fn union(&mut self, other: &IdxSet<T>) -> bool {
     pub fn subtract(&mut self, other: &IdxSet<T>) -> bool {
         bitwise(self.words_mut(), other.words(), &Subtract)
     }
+
+    /// Calls `f` on each index value held in this set, up to the
+    /// bound `max_bits` on the size of universe of indexes.
+    pub fn each_bit<F>(&self, max_bits: usize, f: F) where F: FnMut(T) {
+        each_bit(self, max_bits, f)
+    }
+}
+
+fn each_bit<T: Idx, F>(words: &IdxSet<T>, max_bits: usize, mut f: F) where F: FnMut(T) {
+    let usize_bits: usize = mem::size_of::<usize>() * 8;
+
+    for (word_index, &word) in words.words().iter().enumerate() {
+        if word != 0 {
+            let base_index = word_index * usize_bits;
+            for offset in 0..usize_bits {
+                let bit = 1 << offset;
+                if (word & bit) != 0 {
+                    // NB: we round up the total number of bits
+                    // that we store in any given bit set so that
+                    // it is an even multiple of usize::BITS. This
+                    // means that there may be some stray bits at
+                    // the end that do not correspond to any
+                    // actual value; that's why we first check
+                    // that we are in range of bits_per_block.
+                    let bit_index = base_index + offset as usize;
+                    if bit_index >= max_bits {
+                        return;
+                    } else {
+                        f(Idx::new(bit_index));
+                    }
+                }
+            }
+        }
+    }
 }

src/librustc_mir/dataflow/graphviz.rs

@@ -13,7 +13,6 @@
 use syntax::ast::NodeId;
 use rustc::mir::{BasicBlock, Mir};
 use rustc_data_structures::bitslice::bits_to_string;
-use rustc_data_structures::indexed_set::{IdxSet};
 use rustc_data_structures::indexed_vec::Idx;
 
 use dot;
@@ -24,7 +23,6 @@
 use std::io;
 use std::io::prelude::*;
 use std::marker::PhantomData;
-use std::mem;
 use std::path::Path;
 
 use util;
@@ -32,54 +30,6 @@
 use super::{BitDenotation, DataflowState};
 use super::DataflowBuilder;
 
-impl<O: BitDenotation> DataflowState<O> {
-    fn each_bit<F>(&self, words: &IdxSet<O::Idx>, mut f: F)
-        where F: FnMut(O::Idx) {
-        //! Helper for iterating over the bits in a bitvector.
-
-        let bits_per_block = self.operator.bits_per_block();
-        let usize_bits: usize = mem::size_of::<usize>() * 8;
-
-        for (word_index, &word) in words.words().iter().enumerate() {
-            if word != 0 {
-                let base_index = word_index * usize_bits;
-                for offset in 0..usize_bits {
-                    let bit = 1 << offset;
-                    if (word & bit) != 0 {
-                        // NB: we round up the total number of bits
-                        // that we store in any given bit set so that
-                        // it is an even multiple of usize::BITS. This
-                        // means that there may be some stray bits at
-                        // the end that do not correspond to any
-                        // actual value; that's why we first check
-                        // that we are in range of bits_per_block.
-                        let bit_index = base_index + offset as usize;
-                        if bit_index >= bits_per_block {
-                            return;
-                        } else {
-                            f(O::Idx::new(bit_index));
-                        }
-                    }
-                }
-            }
-        }
-    }
-
-    pub fn interpret_set<'c, P>(&self,
-                                o: &'c O,
-                                words: &IdxSet<O::Idx>,
-                                render_idx: &P)
-                                -> Vec<&'c Debug>
-        where P: Fn(&O, O::Idx) -> &Debug
-    {
-        let mut v = Vec::new();
-        self.each_bit(words, |i| {
-            v.push(render_idx(o, i));
-        });
-        v
-    }
-}
-
 pub trait MirWithFlowState<'tcx> {
     type BD: BitDenotation;
     fn node_id(&self) -> NodeId;

src/librustc_mir/dataflow/mod.rs

@@ -293,6 +293,28 @@ pub struct DataflowState<O: BitDenotation>
     pub(crate) operator: O,
 }
 
+impl<O: BitDenotation> DataflowState<O> {
+    pub fn each_bit<F>(&self, words: &IdxSet<O::Idx>, f: F) where F: FnMut(O::Idx)
+    {
+        let bits_per_block = self.operator.bits_per_block();
+        words.each_bit(bits_per_block, f)
+    }
+
+    pub fn interpret_set<'c, P>(&self,
+                                o: &'c O,
+                                words: &IdxSet<O::Idx>,
+                                render_idx: &P)
+                                -> Vec<&'c Debug>
+        where P: Fn(&O, O::Idx) -> &Debug
+    {
+        let mut v = Vec::new();
+        self.each_bit(words, |i| {
+            v.push(render_idx(o, i));
+        });
+        v
+    }
+}
+
 #[derive(Debug)]
 pub struct AllSets<E: Idx> {
     /// Analysis bitwidth for each block.