diff --git a/lib/cretonne/src/ir/dfg.rs b/lib/cretonne/src/ir/dfg.rs
index 35bb9c8f7e..b913f505e6 100644
--- a/lib/cretonne/src/ir/dfg.rs
+++ b/lib/cretonne/src/ir/dfg.rs
@@ -1,8 +1,9 @@
 //! Data flow graph tracking Instructions, Values, and EBBs.
 
-use ir::{Ebb, Inst, Value, Type};
+use ir::{Ebb, Inst, Value, Type, SigRef, Signature, FuncRef};
 use ir::entities::{NO_VALUE, ExpandedValue};
 use ir::instructions::InstructionData;
+use ir::extfunc::ExtFuncData;
 use entity_map::{EntityMap, PrimaryEntityData};
 
 use std::ops::{Index, IndexMut};
@@ -33,10 +34,19 @@ pub struct DataFlowGraph {
     /// This is implemented directly with a `Vec` rather than an `EntityMap<Value, ...>` because
     /// the Value entity references can refer to two things -- an instruction or an extended value.
     extended_values: Vec<ValueData>,
+
+    /// Function signature table. These signatures are referenced by indirect call instructions as
+    /// well as the external function references.
+    pub signatures: EntityMap<SigRef, Signature>,
+
+    /// External function references. These are functions that can be called directly.
+    pub ext_funcs: EntityMap<FuncRef, ExtFuncData>,
 }
 
 impl PrimaryEntityData for InstructionData {}
 impl PrimaryEntityData for EbbData {}
+impl PrimaryEntityData for Signature {}
+impl PrimaryEntityData for ExtFuncData {}
 
 impl DataFlowGraph {
     /// Create a new empty `DataFlowGraph`.
@@ -45,6 +55,8 @@ impl DataFlowGraph {
             insts: EntityMap::new(),
             ebbs: EntityMap::new(),
             extended_values: Vec::new(),
+            signatures: EntityMap::new(),
+            ext_funcs: EntityMap::new(),
         }
     }
 
diff --git a/lib/cretonne/src/ir/extfunc.rs b/lib/cretonne/src/ir/extfunc.rs
index 78b723398e..6f89d5d307 100644
--- a/lib/cretonne/src/ir/extfunc.rs
+++ b/lib/cretonne/src/ir/extfunc.rs
@@ -6,7 +6,7 @@
 //! This module declares the data types used to represent external functions and call signatures.
 
 use std::fmt::{self, Display, Formatter};
-use ir::Type;
+use ir::{Type, FunctionName, SigRef};
 
 /// Function signature.
 ///
@@ -104,6 +104,21 @@ pub enum ArgumentExtension {
     Sext,
 }
 
+/// An external function.
+///
+/// Information about a function that can be called directly with a direct `call` instruction.
+#[derive(Clone, Debug)]
+pub struct ExtFuncData {
+    pub name: FunctionName,
+    pub signature: SigRef,
+}
+
+impl Display for ExtFuncData {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        write!(f, "{} {}", self.signature, self.name)
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/lib/cretonne/src/ir/mod.rs b/lib/cretonne/src/ir/mod.rs
index bbbc6d26ab..5056d9b29e 100644
--- a/lib/cretonne/src/ir/mod.rs
+++ b/lib/cretonne/src/ir/mod.rs
@@ -15,7 +15,7 @@ mod extfunc;
 mod builder;
 
 pub use ir::funcname::FunctionName;
-pub use ir::extfunc::{Signature, ArgumentType, ArgumentExtension};
+pub use ir::extfunc::{Signature, ArgumentType, ArgumentExtension, ExtFuncData};
 pub use ir::types::Type;
 pub use ir::entities::{Ebb, Inst, Value, StackSlot, JumpTable, FuncRef, SigRef};
 pub use ir::instructions::{Opcode, InstructionData, VariableArgs};
diff --git a/lib/cretonne/src/write.rs b/lib/cretonne/src/write.rs
index dfae305933..ac487c6f37 100644
--- a/lib/cretonne/src/write.rs
+++ b/lib/cretonne/src/write.rs
@@ -43,6 +43,17 @@ fn write_preamble(w: &mut Write, func: &Function) -> result::Result<bool, Error>
         try!(writeln!(w, "    {} = {}", ss, func.stack_slots[ss]));
     }
 
+    // Write out all signatures before functions since function decls can refer to signatures.
+    for sig in func.dfg.signatures.keys() {
+        any = true;
+        try!(writeln!(w, "    {} = signature{}", sig, func.dfg.signatures[sig]));
+    }
+
+    for fnref in func.dfg.ext_funcs.keys() {
+        any = true;
+        try!(writeln!(w, "    {} = {}", fnref, func.dfg.ext_funcs[fnref]));
+    }
+
     for jt in func.jump_tables.keys() {
         any = true;
         try!(writeln!(w, "    {} = {}", jt, func.jump_tables[jt]));