diff --git a/lib/cretonne/src/entity_list.rs b/lib/cretonne/src/entity_list.rs
index 1ccddc3aed..4b535e3f56 100644
--- a/lib/cretonne/src/entity_list.rs
+++ b/lib/cretonne/src/entity_list.rs
@@ -46,12 +46,11 @@
 //! The index stored in an `EntityList` points to part 2, the list elements. The value 0 is
 //! reserved for the empty list which isn't allocated in the vector.
 
+use entity_ref::EntityRef;
 use std::hash::{Hash, Hasher};
 use std::marker::PhantomData;
 use std::mem;
 
-use entity_map::EntityRef;
-
 /// A small list of entity references allocated from a pool.
 ///
 /// All of the list methods that take a pool reference must be given the same pool reference every
@@ -484,7 +483,7 @@ mod tests {
     use super::*;
     use super::{sclass_size, sclass_for_length};
     use ir::Inst;
-    use entity_map::EntityRef;
+    use entity_ref::EntityRef;
 
     #[test]
     fn size_classes() {
diff --git a/lib/cretonne/src/entity_map.rs b/lib/cretonne/src/entity_map.rs
index 8227a19fb6..be73b790e1 100644
--- a/lib/cretonne/src/entity_map.rs
+++ b/lib/cretonne/src/entity_map.rs
@@ -1,8 +1,7 @@
 //! Densely numbered entity references as mapping keys.
 //!
-//! This module defines an `EntityRef` trait that should be implemented by reference types wrapping
-//! a small integer index. The `EntityMap` data structure uses the dense index space to implement a
-//! map with a vector. There are primary and secondary entity maps:
+//! The `EntityMap` data structure uses the dense index space to implement a map with a vector.
+//! There are primary and secondary entity maps:
 //!
 //! - A *primary* `EntityMap` contains the main definition of an entity, and it can be used to
 //!   allocate new entity references with the `push` method. The values stores in a primary map
@@ -10,22 +9,10 @@
 //! - A *secondary* `EntityMap` contains additional data about entities kept in a primary map. The
 //!   values need to implement `Clone + Default` traits so the map can be grown with `ensure`.
 
-use std::vec::Vec;
-use std::default::Default;
+use entity_ref::EntityRef;
 use std::marker::PhantomData;
 use std::ops::{Index, IndexMut};
 
-/// A type wrapping a small integer index should implement `EntityRef` so it can be used as the key
-/// of an `EntityMap`.
-pub trait EntityRef: Copy + Eq {
-    /// Create a new entity reference from a small integer.
-    /// This should crash if the requested index is not representable.
-    fn new(usize) -> Self;
-
-    /// Get the index that was used to create this entity reference.
-    fn index(self) -> usize;
-}
-
 /// A mapping `K -> V` for densely indexed entity references.
 #[derive(Debug, Clone)]
 pub struct EntityMap<K, V>
diff --git a/lib/cretonne/src/entity_ref.rs b/lib/cretonne/src/entity_ref.rs
new file mode 100644
index 0000000000..9990b521f0
--- /dev/null
+++ b/lib/cretonne/src/entity_ref.rs
@@ -0,0 +1,51 @@
+//! Densely numbered entity references as mapping keys.
+//!
+//! This module defines an `EntityRef` trait that should be implemented by reference types wrapping
+//! a small integer index.
+
+/// A type wrapping a small integer index should implement `EntityRef` so it can be used as the key
+/// of an `EntityMap` or `SparseMap`.
+pub trait EntityRef: Copy + Eq {
+    /// Create a new entity reference from a small integer.
+    /// This should crash if the requested index is not representable.
+    fn new(usize) -> Self;
+
+    /// Get the index that was used to create this entity reference.
+    fn index(self) -> usize;
+}
+
+/// Macro which provides the common implementation of a 32-bit entity reference.
+#[macro_export]
+macro_rules! entity_impl {
+    // Basic traits.
+    ($entity:ident) => {
+        impl $crate::entity_ref::EntityRef for $entity {
+            fn new(index: usize) -> Self {
+                assert!(index < (::std::u32::MAX as usize));
+                $entity(index as u32)
+            }
+
+            fn index(self) -> usize {
+                self.0 as usize
+            }
+        }
+
+        impl $crate::packed_option::ReservedValue for $entity {
+            fn reserved_value() -> $entity {
+                $entity(::std::u32::MAX)
+            }
+        }
+    };
+
+    // Include basic `Display` impl using the given display prefix.
+    // Display an `Ebb` reference as "ebb12".
+    ($entity:ident, $display_prefix:expr) => {
+        entity_impl!($entity);
+
+        impl ::std::fmt::Display for $entity {
+            fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
+                write!(f, "{}{}", $display_prefix, self.0)
+            }
+        }
+    }
+}
diff --git a/lib/cretonne/src/ir/entities.rs b/lib/cretonne/src/ir/entities.rs
index 04b54e0488..98a29c7e61 100644
--- a/lib/cretonne/src/ir/entities.rs
+++ b/lib/cretonne/src/ir/entities.rs
@@ -19,46 +19,9 @@
 //! The entity references all implement the `Display` trait in a way that matches the textual IL
 //! format.
 
-use entity_map::EntityRef;
-use packed_option::ReservedValue;
-use std::fmt::{self, Display, Formatter};
+use std::fmt;
 use std::u32;
 
-// Implement the common traits for a 32-bit entity reference.
-macro_rules! entity_impl {
-    // Basic traits.
-    ($entity:ident) => {
-        impl EntityRef for $entity {
-            fn new(index: usize) -> Self {
-                assert!(index < (u32::MAX as usize));
-                $entity(index as u32)
-            }
-
-            fn index(self) -> usize {
-                self.0 as usize
-            }
-        }
-
-        impl ReservedValue for $entity {
-            fn reserved_value() -> $entity {
-                $entity(u32::MAX)
-            }
-        }
-    };
-
-    // Include basic `Display` impl using the given display prefix.
-    // Display an `Ebb` reference as "ebb12".
-    ($entity:ident, $display_prefix:expr) => {
-        entity_impl!($entity);
-
-        impl Display for $entity {
-            fn fmt(&self, fmt: &mut Formatter) -> fmt::Result {
-                write!(fmt, "{}{}", $display_prefix, self.0)
-            }
-        }
-    }
-}
-
 /// An opaque reference to an extended basic block in a function.
 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, PartialOrd, Ord)]
 pub struct Ebb(u32);
@@ -138,17 +101,17 @@ pub enum AnyEntity {
     SigRef(SigRef),
 }
 
-impl Display for AnyEntity {
-    fn fmt(&self, fmt: &mut Formatter) -> fmt::Result {
+impl fmt::Display for AnyEntity {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         match *self {
-            AnyEntity::Function => write!(fmt, "function"),
-            AnyEntity::Ebb(r) => r.fmt(fmt),
-            AnyEntity::Inst(r) => r.fmt(fmt),
-            AnyEntity::Value(r) => r.fmt(fmt),
-            AnyEntity::StackSlot(r) => r.fmt(fmt),
-            AnyEntity::JumpTable(r) => r.fmt(fmt),
-            AnyEntity::FuncRef(r) => r.fmt(fmt),
-            AnyEntity::SigRef(r) => r.fmt(fmt),
+            AnyEntity::Function => write!(f, "function"),
+            AnyEntity::Ebb(r) => r.fmt(f),
+            AnyEntity::Inst(r) => r.fmt(f),
+            AnyEntity::Value(r) => r.fmt(f),
+            AnyEntity::StackSlot(r) => r.fmt(f),
+            AnyEntity::JumpTable(r) => r.fmt(f),
+            AnyEntity::FuncRef(r) => r.fmt(f),
+            AnyEntity::SigRef(r) => r.fmt(f),
         }
     }
 }
diff --git a/lib/cretonne/src/ir/jumptable.rs b/lib/cretonne/src/ir/jumptable.rs
index 24dad02056..aaaa694a50 100644
--- a/lib/cretonne/src/ir/jumptable.rs
+++ b/lib/cretonne/src/ir/jumptable.rs
@@ -122,7 +122,7 @@ impl Display for JumpTableData {
 mod tests {
     use super::JumpTableData;
     use ir::Ebb;
-    use entity_map::EntityRef;
+    use entity_ref::EntityRef;
 
     #[test]
     fn empty() {
diff --git a/lib/cretonne/src/ir/layout.rs b/lib/cretonne/src/ir/layout.rs
index 3d569adcc6..0fa48edc6f 100644
--- a/lib/cretonne/src/ir/layout.rs
+++ b/lib/cretonne/src/ir/layout.rs
@@ -982,7 +982,7 @@ impl<'f> Cursor<'f> {
 #[cfg(test)]
 mod tests {
     use super::{Layout, Cursor, CursorPosition};
-    use entity_map::EntityRef;
+    use entity_ref::EntityRef;
     use ir::{Ebb, Inst, ProgramOrder};
     use std::cmp::Ordering;
 
diff --git a/lib/cretonne/src/ir/progpoint.rs b/lib/cretonne/src/ir/progpoint.rs
index 3134a53603..373bc382ab 100644
--- a/lib/cretonne/src/ir/progpoint.rs
+++ b/lib/cretonne/src/ir/progpoint.rs
@@ -1,6 +1,6 @@
 //! Program points.
 
-use entity_map::EntityRef;
+use entity_ref::EntityRef;
 use ir::{Ebb, Inst, ValueDef};
 use std::fmt;
 use std::u32;
@@ -122,7 +122,7 @@ pub trait ProgramOrder {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use entity_map::EntityRef;
+    use entity_ref::EntityRef;
     use ir::{Inst, Ebb};
 
     #[test]
diff --git a/lib/cretonne/src/isa/registers.rs b/lib/cretonne/src/isa/registers.rs
index 5549e98157..2823fbea37 100644
--- a/lib/cretonne/src/isa/registers.rs
+++ b/lib/cretonne/src/isa/registers.rs
@@ -1,6 +1,6 @@
 //! Data structures describing the registers in an ISA.
 
-use entity_map::EntityRef;
+use entity_ref::EntityRef;
 use std::fmt;
 
 /// Register units are the smallest units of register allocation.
diff --git a/lib/cretonne/src/lib.rs b/lib/cretonne/src/lib.rs
index 6ac2f7993b..09bdfc9302 100644
--- a/lib/cretonne/src/lib.rs
+++ b/lib/cretonne/src/lib.rs
@@ -12,6 +12,8 @@ pub const VERSION: &'static str = env!("CARGO_PKG_VERSION");
 
 #[macro_use]
 pub mod dbg;
+#[macro_use]
+pub mod entity_ref;
 
 pub mod binemit;
 pub mod dominator_tree;
diff --git a/lib/cretonne/src/loop_analysis.rs b/lib/cretonne/src/loop_analysis.rs
index 5ed5f8a4d8..d0a9d505bd 100644
--- a/lib/cretonne/src/loop_analysis.rs
+++ b/lib/cretonne/src/loop_analysis.rs
@@ -1,34 +1,16 @@
 //! A loop analysis represented as mappings of loops to their header Ebb
 //! and parent in the loop tree.
 
-use ir::{Function, Ebb, Layout};
-use flowgraph::ControlFlowGraph;
 use dominator_tree::DominatorTree;
-use entity_map::{EntityMap, PrimaryEntityData};
-use packed_option::{PackedOption, ReservedValue};
-use entity_map::{EntityRef, Keys};
-use std::u32;
+use entity_map::{EntityMap, PrimaryEntityData, Keys};
+use flowgraph::ControlFlowGraph;
+use ir::{Function, Ebb, Layout};
+use packed_option::PackedOption;
 
 /// A opaque reference to a code loop.
 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
 pub struct Loop(u32);
-impl EntityRef for Loop {
-    fn new(index: usize) -> Self {
-        assert!(index < (u32::MAX as usize));
-        Loop(index as u32)
-    }
-
-    fn index(self) -> usize {
-        self.0 as usize
-    }
-}
-
-impl ReservedValue for Loop {
-    fn reserved_value() -> Loop {
-        Loop(u32::MAX)
-    }
-}
-
+entity_impl!(Loop, "loop");
 
 /// Loop tree information for a single function.
 ///
diff --git a/lib/cretonne/src/regalloc/diversion.rs b/lib/cretonne/src/regalloc/diversion.rs
index 89decad82f..e8e8d3d190 100644
--- a/lib/cretonne/src/regalloc/diversion.rs
+++ b/lib/cretonne/src/regalloc/diversion.rs
@@ -89,7 +89,7 @@ impl RegDiversions {
 mod tests {
     use super::*;
     use ir::Value;
-    use entity_map::EntityRef;
+    use entity_ref::EntityRef;
 
     #[test]
     fn inserts() {
diff --git a/lib/cretonne/src/regalloc/liverange.rs b/lib/cretonne/src/regalloc/liverange.rs
index 1cabd113dd..9866fabb20 100644
--- a/lib/cretonne/src/regalloc/liverange.rs
+++ b/lib/cretonne/src/regalloc/liverange.rs
@@ -394,7 +394,7 @@ impl SparseMapValue<Value> for LiveRange {
 mod tests {
     use super::LiveRange;
     use ir::{Inst, Ebb, Value};
-    use entity_map::EntityRef;
+    use entity_ref::EntityRef;
     use ir::{ProgramOrder, ExpandedProgramPoint};
     use std::cmp::Ordering;
 
diff --git a/lib/cretonne/src/regalloc/solver.rs b/lib/cretonne/src/regalloc/solver.rs
index d94cf3e72d..b2e73bf91f 100644
--- a/lib/cretonne/src/regalloc/solver.rs
+++ b/lib/cretonne/src/regalloc/solver.rs
@@ -675,7 +675,7 @@ impl Solver {
 
 #[cfg(test)]
 mod tests {
-    use entity_map::EntityRef;
+    use entity_ref::EntityRef;
     use ir::Value;
     use isa::{TargetIsa, RegClass, RegUnit};
     use regalloc::AllocatableSet;
diff --git a/lib/cretonne/src/sparse_map.rs b/lib/cretonne/src/sparse_map.rs
index ad49ac49fa..b1e844b618 100644
--- a/lib/cretonne/src/sparse_map.rs
+++ b/lib/cretonne/src/sparse_map.rs
@@ -35,7 +35,8 @@
 //! - `SparseMap` requires the values to implement `SparseMapValue<K>` which means that they must
 //!   contain their own key.
 
-use entity_map::{EntityRef, EntityMap};
+use entity_map::EntityMap;
+use entity_ref::EntityRef;
 use std::mem;
 use std::slice;
 use std::u32;
@@ -215,7 +216,7 @@ pub type SparseSet<T> = SparseMap<T, T>;
 #[cfg(test)]
 mod tests {
     use super::*;
-    use entity_map::EntityRef;
+    use entity_ref::EntityRef;
     use ir::Inst;
 
     // Mock key-value object for testing.