diff --git a/src/backend/mod.rs b/src/backend/mod.rs
index d516f36..3900d41 100644
--- a/src/backend/mod.rs
+++ b/src/backend/mod.rs
@@ -587,8 +587,7 @@ pub fn compile(module: &Module<'_>) -> anyhow::Result<Vec<u8>> {
         match func_decl {
             FuncDecl::Import(_, _) => anyhow::bail!("Import comes after func with body: {}", func),
             FuncDecl::Lazy(sig, _, _)
-            | FuncDecl::Body(sig, _, _)
-            | FuncDecl::Expanded(sig, _, _, _) => {
+            | FuncDecl::Body(sig, _, _) => {
                 funcs.function(sig.index() as u32);
             }
             FuncDecl::None => panic!("FuncDecl::None at compilation time"),
@@ -710,10 +709,6 @@ pub fn compile(module: &Module<'_>) -> anyhow::Result<Vec<u8>> {
                     let data = &module.orig_bytes[reader.range()];
                     Ok(FuncOrRawBytes::Raw(data))
                 }
-                FuncDecl::Expanded(_, _name, range, _) => {
-                    let data = &module.orig_bytes[range.clone()];
-                    Ok(FuncOrRawBytes::Raw(data))
-                }
                 FuncDecl::Body(_, name, body) => {
                     log::debug!("Compiling {} \"{}\"", func, name);
                     WasmFuncBackend::new(body)?
diff --git a/src/interp.rs b/src/interp.rs
index 0f93f04..9417597 100644
--- a/src/interp.rs
+++ b/src/interp.rs
@@ -95,7 +95,7 @@ impl InterpContext {
                 assert_eq!(import.kind, ImportKind::Func(func));
                 return self.call_import(&import.name[..], args);
             }
-            FuncDecl::Body(_, _, body) | FuncDecl::Expanded(_, _, _, body) => body,
+            FuncDecl::Body(_, _, body) => body,
             FuncDecl::None => panic!("FuncDecl::None in call()"),
         };
 
diff --git a/src/ir/display.rs b/src/ir/display.rs
index 08ce720..841829c 100644
--- a/src/ir/display.rs
+++ b/src/ir/display.rs
@@ -230,7 +230,7 @@ impl<'a> Display for ModuleDisplay<'a> {
         }
         for (func, func_decl) in self.0.funcs.entries() {
             match func_decl {
-                FuncDecl::Body(sig, name, body) | FuncDecl::Expanded(sig, name, _, body) => {
+                FuncDecl::Body(sig, name, body) => {
                     writeln!(
                         f,
                         "  {} \"{}\": {} = # {}",
diff --git a/src/ir/func.rs b/src/ir/func.rs
index e00df9c..7c937ed 100644
--- a/src/ir/func.rs
+++ b/src/ir/func.rs
@@ -4,7 +4,6 @@ use crate::entity::{EntityRef, EntityVec, PerEntity};
 use crate::frontend::parse_body;
 use crate::ir::SourceLoc;
 use anyhow::Result;
-use std::ops::Range;
 
 /// A declaration of a function: there is one `FuncDecl` per `Func`
 /// index.
@@ -14,10 +13,6 @@ pub enum FuncDecl<'a> {
     Import(Signature, String),
     /// An un-expanded body that can be lazily expanded if needed.
     Lazy(Signature, String, wasmparser::FunctionBody<'a>),
-    /// Expanded body, but still "clean" (unchanged); range in
-    /// original Wasm lets us pass it straight through when converting
-    /// back to a Wasm module.
-    Expanded(Signature, String, Range<usize>, FunctionBody),
     /// A modified or new function body that requires compilation.
     Body(Signature, String, FunctionBody),
     /// A placeholder.
@@ -30,7 +25,6 @@ impl<'a> FuncDecl<'a> {
         match self {
             FuncDecl::Import(sig, ..) => *sig,
             FuncDecl::Lazy(sig, ..) => *sig,
-            FuncDecl::Expanded(sig, ..) => *sig,
             FuncDecl::Body(sig, ..) => *sig,
             FuncDecl::None => panic!("No signature for FuncDecl::None"),
         }
@@ -39,9 +33,8 @@ impl<'a> FuncDecl<'a> {
     pub fn parse(&mut self, module: &Module) -> Result<()> {
         match self {
             FuncDecl::Lazy(sig, name, body) => {
-                let range = body.range();
                 let body = parse_body(module, *sig, body)?;
-                *self = FuncDecl::Expanded(*sig, name.clone(), range, body);
+                *self = FuncDecl::Body(*sig, name.clone(), body);
                 Ok(())
             }
             _ => Ok(()),
@@ -49,7 +42,6 @@ impl<'a> FuncDecl<'a> {
     }
 
     pub fn optimize(&mut self) {
-        self.mark_dirty();
         match self {
             FuncDecl::Body(_, _, body) => {
                 body.optimize();
@@ -59,7 +51,6 @@ impl<'a> FuncDecl<'a> {
     }
 
     pub fn convert_to_max_ssa(&mut self) {
-        self.mark_dirty();
         match self {
             FuncDecl::Body(_, _, body) => {
                 body.convert_to_max_ssa();
@@ -68,23 +59,14 @@ impl<'a> FuncDecl<'a> {
         }
     }
 
-    pub fn mark_dirty(&mut self) {
-        let new = match std::mem::take(self) {
-            FuncDecl::Expanded(sig, name, _, body) => FuncDecl::Body(sig, name, body),
-            x => x,
-        };
-        *self = new;
-    }
-
     pub fn body(&self) -> Option<&FunctionBody> {
         match self {
-            FuncDecl::Expanded(_, _, _, body) | FuncDecl::Body(_, _, body) => Some(body),
+            FuncDecl::Body(_, _, body) => Some(body),
             _ => None,
         }
     }
 
     pub fn body_mut(&mut self) -> Option<&mut FunctionBody> {
-        self.mark_dirty();
         match self {
             FuncDecl::Body(_, _, body) => Some(body),
             _ => None,
@@ -95,7 +77,6 @@ impl<'a> FuncDecl<'a> {
         match self {
             FuncDecl::Body(_, name, _)
             | FuncDecl::Lazy(_, name, _)
-            | FuncDecl::Expanded(_, name, _, _)
             | FuncDecl::Import(_, name) => &name[..],
             FuncDecl::None => panic!("No name for FuncDecl::None"),
         }
@@ -105,7 +86,6 @@ impl<'a> FuncDecl<'a> {
         match self {
             FuncDecl::Body(_, name, _)
             | FuncDecl::Lazy(_, name, _)
-            | FuncDecl::Expanded(_, name, _, _)
             | FuncDecl::Import(_, name) => *name = new_name.to_owned(),
             FuncDecl::None => panic!("No name for FuncDecl::None"),
         }
diff --git a/src/ir/module.rs b/src/ir/module.rs
index 886c736..61286dc 100644
--- a/src/ir/module.rs
+++ b/src/ir/module.rs
@@ -187,6 +187,21 @@ impl<'a> Module<'a> {
         Ok(&mut self.funcs[id])
     }
 
+    pub fn clone_and_expand_body(&self, id: Func) -> Result<FunctionBody> {
+        let mut body = self.funcs[id].clone();
+        body.parse(self)?;
+        Ok(match body {
+            FuncDecl::Body(_, _, body) => body,
+            _ => unreachable!(),
+        })
+    }
+
+    pub fn replace_body(&mut self, id: Func, body: FunctionBody) {
+        let sig = self.funcs[id].sig();
+        let name = self.funcs[id].name().to_owned();
+        self.funcs[id] = FuncDecl::Body(sig, name, body);
+    }
+
     pub fn expand_all_funcs(&mut self) -> Result<()> {
         for id in 0..self.funcs.len() {
             let id = Func::new(id);