diff --git a/src/backend/binaryen.rs b/src/backend/binaryen.rs
index ebc31e8..e061c3d 100644
--- a/src/backend/binaryen.rs
+++ b/src/backend/binaryen.rs
@@ -14,8 +14,8 @@ pub struct Expression(BinaryenModule, BinaryenExpression);
 #[derive(Clone, Copy, Debug)]
 pub struct Export(BinaryenModule, BinaryenExport);
 
-type BinaryenIndex = u32;
-type BinaryenType = usize;
+pub type BinaryenIndex = u32;
+pub type BinaryenType = usize;
 
 impl Module {
     pub fn read(data: &[u8]) -> Result<Module> {
@@ -423,6 +423,8 @@ pub type BinaryenModule = *const c_void;
 type BinaryenFunction = *const c_void;
 type BinaryenExpression = *const c_void;
 type BinaryenExport = *const c_void;
+type BinaryenRelooper = *const c_void;
+type BinaryenRelooperBlock = *const c_void;
 
 #[repr(C)]
 struct BinaryenModuleAllocateAndWriteResult {
@@ -440,6 +442,74 @@ impl Drop for BinaryenModuleAllocateAndWriteResult {
     }
 }
 
+pub struct Relooper(BinaryenModule, BinaryenRelooper);
+
+#[derive(Clone, Copy, PartialEq, Eq)]
+pub struct RelooperBlock(BinaryenRelooperBlock);
+
+#[derive(Clone, Copy, PartialEq, Eq)]
+pub struct RelooperBlockWithSwitch(BinaryenRelooperBlock);
+
+impl Relooper {
+    pub fn new(module: &Module) -> Relooper {
+        let ptr = unsafe { RelooperCreate(module.0) };
+        Relooper(module.0, ptr)
+    }
+
+    pub fn construct(self, entry: RelooperBlock, index_var: usize) -> Expression {
+        let module = self.0;
+        let expr = unsafe { RelooperRenderAndDispose(self.1, entry.0, index_var as BinaryenIndex) };
+        std::mem::forget(self);
+        Expression(module, expr)
+    }
+
+    pub fn add_block(&mut self, expr: Expression) -> RelooperBlock {
+        RelooperBlock(unsafe { RelooperAddBlock(self.1, expr.1) })
+    }
+
+    pub fn add_block_with_switch(
+        &mut self,
+        expr: Expression,
+        sel: Expression,
+    ) -> RelooperBlockWithSwitch {
+        RelooperBlockWithSwitch(unsafe { RelooperAddBlockWithSwitch(self.1, expr.1, sel.1) })
+    }
+}
+
+impl RelooperBlock {
+    pub fn cond_branch(&self, to: RelooperBlock, cond: Expression, edge: Expression) {
+        unsafe {
+            RelooperAddBranch(self.0, to.0, cond.1, edge.1);
+        }
+    }
+
+    pub fn branch(&self, to: RelooperBlock, edge: Expression) {
+        unsafe {
+            RelooperAddBranch(self.0, to.0, std::ptr::null(), edge.1);
+        }
+    }
+}
+
+impl RelooperBlockWithSwitch {
+    pub fn switch(&self, to: RelooperBlock, edge: Expression, indices: &[BinaryenIndex]) {
+        unsafe {
+            RelooperAddBranchForSwitch(
+                self.0,
+                to.0,
+                indices.as_ptr(),
+                indices.len() as BinaryenIndex,
+                edge.1,
+            );
+        }
+    }
+}
+
+impl Drop for Relooper {
+    fn drop(&mut self) {
+        panic!("Relooper dropped without constructing/disposing");
+    }
+}
+
 #[link(name = "binaryen")]
 extern "C" {
     fn BinaryenModuleRead(data: *const u8, len: usize) -> BinaryenModule;
@@ -613,6 +683,32 @@ extern "C" {
     fn BinaryenLiteralInt64(x: i64) -> BinaryenLiteral;
     fn BinaryenLiteralFloat32Bits(x: i32) -> BinaryenLiteral;
     fn BinaryenLiteralFloat64Bits(x: i64) -> BinaryenLiteral;
+
+    fn RelooperCreate(module: BinaryenModule) -> BinaryenRelooper;
+    fn RelooperRenderAndDispose(
+        r: BinaryenRelooper,
+        entry: BinaryenRelooperBlock,
+        labelVar: BinaryenIndex,
+    ) -> BinaryenExpression;
+    fn RelooperAddBlock(r: BinaryenRelooper, code: BinaryenExpression) -> BinaryenRelooperBlock;
+    fn RelooperAddBranch(
+        from: BinaryenRelooperBlock,
+        to: BinaryenRelooperBlock,
+        cond: BinaryenExpression,
+        edge_code: BinaryenExpression,
+    );
+    fn RelooperAddBlockWithSwitch(
+        r: BinaryenRelooper,
+        code: BinaryenExpression,
+        selector: BinaryenExpression,
+    ) -> BinaryenRelooperBlock;
+    fn RelooperAddBranchForSwitch(
+        from: BinaryenRelooperBlock,
+        to: BinaryenRelooperBlock,
+        indices: *const BinaryenIndex,
+        n_indices: BinaryenIndex,
+        edge_code: BinaryenExpression,
+    );
 }
 
 #[repr(C)]
diff --git a/src/backend/lower.rs b/src/backend/lower.rs
index 73d4873..8025146 100644
--- a/src/backend/lower.rs
+++ b/src/backend/lower.rs
@@ -1,5 +1,6 @@
 use crate::backend::binaryen;
 use crate::ir::*;
+use crate::Operator;
 use fxhash::FxHashMap;
 use wasmparser::Type;
 
@@ -10,76 +11,148 @@ pub(crate) fn generate_body(
     body: &FunctionBody,
     into_mod: &mut binaryen::Module,
 ) -> (Vec<Type>, binaryen::Expression) {
+    let mut ctx = ElabCtx::new(body, into_mod);
+
     // For each block, generate an expr.
     let mut block_exprs: FxHashMap<BlockId, binaryen::Expression> = FxHashMap::default();
-    let mut ctx = ElabCtx::new(body, into_mod);
     for block in body.blocks() {
         let exprs = body[block]
             .insts
             .iter()
-            .map(|&inst| {
+            .flat_map(|&inst| {
                 let inst = body.resolve_alias(inst);
-                elaborate_value(body, into_mod, &mut ctx, inst)
+                ctx.elaborate_value(into_mod, inst)
             })
-            .collect::<Vec<_>>();
+            .collect::<Vec<binaryen::Expression>>();
         block_exprs.insert(block, binaryen::Expression::block(into_mod, &exprs[..]));
     }
 
-    todo!()
+    // Combine blocks into a single body expression, using the
+    // relooper/stackifier support built into Binaryen.
+    let mut relooper = binaryen::Relooper::new(into_mod);
+    let mut entry = None;
+    let mut relooper_blocks: FxHashMap<BlockId, binaryen::RelooperBlock> = FxHashMap::default();
+    for (block_id, block_expr) in block_exprs {}
+
+    let index_var = ctx.new_local(Type::I32);
+    let expr = relooper.construct(entry.unwrap(), index_var as usize);
+    (ctx.new_locals, expr)
 }
 
 #[derive(Clone, Debug)]
-struct ElabCtx {
-    value_to_expr: FxHashMap<Value, binaryen::Expression>,
-    block_params: FxHashMap<(Block, usize), LocalId>,
+struct ElabCtx<'a> {
+    body: &'a FunctionBody,
+    op_result_locals: FxHashMap<(Value, usize), LocalId>,
+    block_param_locals: FxHashMap<(BlockId, usize), LocalId>,
     new_locals: Vec<Type>,
 }
 
-impl ElabCtx {
-    fn new(body: &FunctionBody, into_mod: &mut binaryen::Module) -> ElabCtx {
+impl<'a> ElabCtx<'a> {
+    fn new(body: &'a FunctionBody, into_mod: &mut binaryen::Module) -> ElabCtx<'a> {
         // Create locals for each blockparam.
-        let mut block_params = FxHashMap::default();
-        let mut next_local = body.locals.len() as LocalId;
-        let mut new_locals = vec![];
+        let mut this = ElabCtx {
+            body,
+            op_result_locals: FxHashMap::default(),
+            block_param_locals: FxHashMap::default(),
+            new_locals: vec![],
+        };
+
         for block in body.blocks() {
-            for &(ty, param) in &body[block].params {
-                let new_local = next_local;
-                next_local += 1;
-                block_params.insert((ty, param), new_local);
-                new_locals.push(ty);
+            for &(ty, param) in &body[block].params {}
+        }
+
+        // Create locals for each Operator value and each blockparam.
+        for (value, def) in body.values() {
+            match def {
+                &ValueDef::Operator(_, _, ref tys) => {
+                    for (i, ty) in tys.iter().copied().enumerate() {
+                        let local = this.new_local(ty);
+                        this.op_result_locals.insert((value, i), local);
+                    }
+                }
+                &ValueDef::BlockParam(block, index, ty) => {
+                    let local = this.new_local(ty);
+                    this.block_param_locals.insert((block, index), local);
+                }
+                _ => {}
             }
         }
 
-        ElabCtx {
-            value_to_expr: FxHashMap::default(),
-            block_params,
-            new_locals,
+        this
+    }
+
+    fn elaborate_value(
+        &mut self,
+        into_mod: &binaryen::Module,
+        value: Value,
+    ) -> Option<binaryen::Expression> {
+        let value = self.body.resolve_alias(value);
+
+        match &self.body[value] {
+            &ValueDef::Operator(op, ref args, ref tys) => {
+                // Get expressions for each arg.
+                let args = args.iter().map(|&arg| self.get_val_local(arg));
+                // Create `get_local` expressions for each arg.
+                let binaryen_args = args
+                    .map(|arg_local| into_mod.expr_local_get(arg_local, self.local_ty(arg_local)))
+                    .collect::<Vec<_>>();
+                // Create operator.
+                let expr = self.create_binaryen_op(op, binaryen_args, tys);
+
+                // Set local(s) as appropriate.
+                if tys.len() == 0 {
+                    // Nothing. Create a `drop` expr that wraps the actual operator.
+                    Some(into_mod.expr_drop(expr))
+                } else if tys.len() == 1 {
+                    // Set value directly.
+                    let local = self.get_val_local(value);
+                    Some(into_mod.expr_local_set(local, expr))
+                } else {
+                    todo!("support multivalue")
+                }
+            }
+            _ => None,
         }
     }
-}
 
-fn elaborate_value(
-    body: &FunctionBody,
-    into_mod: &binaryen::Module,
-    ctx: &mut ElabCtx,
-    value: Value,
-) -> binaryen::Expression {
-    let value = body.resolve_alias(value);
-    if let Some(expr) = ctx.value_to_expr.get(&value) {
-        return *expr;
+    fn get_val_local(&self, value: Value) -> LocalId {
+        match &self.body[value] {
+            &ValueDef::Arg(idx, _) => idx as LocalId,
+            &ValueDef::BlockParam(block, idx, _) => {
+                self.block_param_locals.get(&(block, idx)).copied().unwrap()
+            }
+            &ValueDef::Operator(..) => self.op_result_locals.get(&(value, 0)).copied().unwrap(),
+            &ValueDef::PickOutput(value, idx, _) => {
+                self.op_result_locals.get(&(value, idx)).copied().unwrap()
+            }
+            &ValueDef::Alias(val) => self.get_val_local(val),
+            &ValueDef::Placeholder(_) => unreachable!(),
+        }
     }
 
-    match &body[value] {
-        &ValueDef::BlockParam(block, idx) => {}
-        &ValueDef::Arg(idx) => {}
-        &ValueDef::PickOutput(value, idx) => {}
-        &ValueDef::Operator(op, ref args) => {}
-
-        &ValueDef::Alias(_) => unreachable!(),
-        &ValueDef::Placeholder => unreachable!(),
+    fn new_local(&mut self, ty: Type) -> LocalId {
+        let index = (self.body.locals.len() + self.new_locals.len()) as LocalId;
+        self.new_locals.push(ty);
+        index
     }
 
-    todo!()
+    fn create_binaryen_op(
+        &mut self,
+        op: Operator,
+        args: Vec<binaryen::Expression>,
+        tys: &[Type],
+    ) -> binaryen::Expression {
+        todo!()
+    }
+
+    fn local_ty(&self, local: LocalId) -> Type {
+        let index = local as usize;
+        self.body
+            .locals
+            .get(index)
+            .copied()
+            .unwrap_or_else(|| self.new_locals[index - self.body.locals.len()])
+    }
 }
 
 pub(crate) fn create_new_func(
diff --git a/src/frontend.rs b/src/frontend.rs
index 25ab17e..6612116 100644
--- a/src/frontend.rs
+++ b/src/frontend.rs
@@ -128,7 +128,7 @@ fn parse_body<'a>(
 
     for (arg_idx, &arg_ty) in module.signature(my_sig).params.iter().enumerate() {
         let local_idx = arg_idx as LocalId;
-        let value = builder.body.add_value(ValueDef::Arg(arg_idx), vec![arg_ty]);
+        let value = builder.body.add_value(ValueDef::Arg(arg_idx, arg_ty));
         trace!("defining local {} to value {}", local_idx, value);
         builder.locals.declare(local_idx, arg_ty);
         builder.locals.set(local_idx, value);
@@ -155,7 +155,7 @@ fn parse_body<'a>(
         assert!(builder.locals.is_sealed(block));
     }
     for value in &builder.body.values {
-        assert!(value != &ValueDef::Placeholder);
+        assert!(!matches!(value, &ValueDef::Placeholder(_)));
     }
 
     trace!("Final function body:{:?}", ret);
@@ -291,32 +291,30 @@ impl LocalTracker {
 
     fn create_default_value(&mut self, body: &mut FunctionBody, ty: Type) -> Value {
         match ty {
-            Type::I32 => body.add_value(
-                ValueDef::Operator(Operator::I32Const { value: 0 }, vec![]),
+            Type::I32 => body.add_value(ValueDef::Operator(
+                Operator::I32Const { value: 0 },
+                vec![],
                 vec![ty],
-            ),
-            Type::I64 => body.add_value(
-                ValueDef::Operator(Operator::I64Const { value: 0 }, vec![]),
+            )),
+            Type::I64 => body.add_value(ValueDef::Operator(
+                Operator::I64Const { value: 0 },
+                vec![],
                 vec![ty],
-            ),
-            Type::F32 => body.add_value(
-                ValueDef::Operator(
-                    Operator::F32Const {
-                        value: Ieee32::from_bits(0),
-                    },
-                    vec![],
-                ),
+            )),
+            Type::F32 => body.add_value(ValueDef::Operator(
+                Operator::F32Const {
+                    value: Ieee32::from_bits(0),
+                },
+                vec![],
                 vec![ty],
-            ),
-            Type::F64 => body.add_value(
-                ValueDef::Operator(
-                    Operator::F64Const {
-                        value: Ieee64::from_bits(0),
-                    },
-                    vec![],
-                ),
+            )),
+            Type::F64 => body.add_value(ValueDef::Operator(
+                Operator::F64Const {
+                    value: Ieee64::from_bits(0),
+                },
+                vec![],
                 vec![ty],
-            ),
+            )),
             _ => todo!("unsupported type: {:?}", ty),
         }
     }
@@ -1180,7 +1178,7 @@ impl<'a, 'b> FunctionBodyBuilder<'a, 'b> {
 
         let value = self
             .body
-            .add_value(ValueDef::Operator(op, input_operands), outputs.clone());
+            .add_value(ValueDef::Operator(op, input_operands, outputs.clone()));
         log::trace!(" -> value: {:?}", value);
 
         if let Some(block) = self.cur_block {
@@ -1194,7 +1192,7 @@ impl<'a, 'b> FunctionBodyBuilder<'a, 'b> {
             for (i, output_ty) in outputs.into_iter().enumerate() {
                 let pick = self
                     .body
-                    .add_value(ValueDef::PickOutput(value, i), vec![output_ty]);
+                    .add_value(ValueDef::PickOutput(value, i, output_ty));
                 self.op_stack.push((output_ty, pick));
                 log::trace!(" -> pick {}: {:?} ty {:?}", i, pick, output_ty);
             }
diff --git a/src/ir.rs b/src/ir.rs
index 7a3d8d0..0d455a7 100644
--- a/src/ir.rs
+++ b/src/ir.rs
@@ -110,9 +110,6 @@ pub struct FunctionBody {
     pub blocks: Vec<Block>,
     /// Value definitions, indexed by `Value`.
     pub values: Vec<ValueDef>,
-    /// Types, indexed by `Value`. A single value can have multiple
-    /// types if multi-value (e.g. a call).
-    pub types: Vec<Vec<Type>>,
 }
 
 impl FunctionBody {
@@ -134,12 +131,11 @@ impl FunctionBody {
         log::trace!("add_edge: from {} to {}", from, to);
     }
 
-    pub fn add_value(&mut self, value: ValueDef, tys: Vec<Type>) -> Value {
-        log::trace!("add_value: def {:?} ty {:?}", value, tys);
+    pub fn add_value(&mut self, value: ValueDef) -> Value {
+        log::trace!("add_value: def {:?}", value);
         let id = Value(self.values.len() as u32);
         log::trace!(" -> value {:?}", id);
         self.values.push(value.clone());
-        self.types.push(tys);
         id
     }
 
@@ -166,30 +162,31 @@ impl FunctionBody {
         result
     }
 
-    pub fn add_mutable_inst(&mut self, tys: Vec<Type>, def: ValueDef) -> Value {
+    pub fn add_mutable_inst(&mut self, def: ValueDef) -> Value {
         let value = Value(self.values.len() as u32);
-        self.types.push(tys);
         self.values.push(def);
         value
     }
 
     pub fn add_blockparam(&mut self, block: BlockId, ty: Type) -> Value {
         let index = self.blocks[block].params.len();
-        let value = self.add_value(ValueDef::BlockParam(block, index), vec![ty]);
+        let value = self.add_value(ValueDef::BlockParam(block, index, ty));
         self.blocks[block].params.push((ty, value));
         value
     }
 
     pub fn add_placeholder(&mut self, ty: Type) -> Value {
-        self.add_mutable_inst(vec![ty], ValueDef::Placeholder)
+        self.add_mutable_inst(ValueDef::Placeholder(ty))
     }
 
     pub fn replace_placeholder_with_blockparam(&mut self, block: BlockId, value: Value) {
-        assert!(self.values[value.index()] == ValueDef::Placeholder);
-        let ty = self.types[value.index()].get(0).cloned().unwrap();
         let index = self.blocks[block].params.len();
+        let ty = match &self.values[value.index()] {
+            &ValueDef::Placeholder(ty) => ty,
+            _ => unreachable!(),
+        };
         self.blocks[block].params.push((ty, value));
-        self.values[value.index()] = ValueDef::BlockParam(block, index);
+        self.values[value.index()] = ValueDef::BlockParam(block, index, ty);
     }
 
     pub fn resolve_and_update_alias(&mut self, value: Value) -> Value {
@@ -295,12 +292,12 @@ impl Value {
 
 #[derive(Clone, Debug, PartialEq, Eq, Hash)]
 pub enum ValueDef {
-    Arg(usize),
-    BlockParam(BlockId, usize),
-    Operator(Operator, Vec<Value>),
-    PickOutput(Value, usize),
+    Arg(usize, Type),
+    BlockParam(BlockId, usize, Type),
+    Operator(Operator, Vec<Value>, Vec<Type>),
+    PickOutput(Value, usize, Type),
     Alias(Value),
-    Placeholder,
+    Placeholder(Type),
 }
 
 impl ValueDef {
@@ -308,14 +305,14 @@ impl ValueDef {
         match self {
             &ValueDef::Arg { .. } => {}
             &ValueDef::BlockParam { .. } => {}
-            &ValueDef::Operator(_, ref args) => {
+            &ValueDef::Operator(_, ref args, _) => {
                 for &arg in args {
                     f(arg);
                 }
             }
             &ValueDef::PickOutput(from, ..) => f(from),
             &ValueDef::Alias(value) => f(value),
-            &ValueDef::Placeholder => {}
+            &ValueDef::Placeholder(_) => {}
         }
     }
 
@@ -323,14 +320,14 @@ impl ValueDef {
         match self {
             &mut ValueDef::Arg { .. } => {}
             &mut ValueDef::BlockParam { .. } => {}
-            &mut ValueDef::Operator(_, ref mut args) => {
+            &mut ValueDef::Operator(_, ref mut args, _) => {
                 for arg in args {
                     f(arg);
                 }
             }
             &mut ValueDef::PickOutput(ref mut from, ..) => f(from),
             &mut ValueDef::Alias(ref mut value) => f(value),
-            &mut ValueDef::Placeholder => {}
+            &mut ValueDef::Placeholder(_) => {}
         }
     }
 }
diff --git a/src/use_count.rs b/src/use_count.rs
index c6e04a7..4cb6d68 100644
--- a/src/use_count.rs
+++ b/src/use_count.rs
@@ -41,7 +41,7 @@ impl UseCountAnalysis {
                 workqueue_set.remove(&value);
                 match &f.values[value.index()] {
                     &ValueDef::Alias(..) | &ValueDef::Arg(..) | &ValueDef::BlockParam(..) => {}
-                    &ValueDef::Operator(_op, ref args) => {
+                    &ValueDef::Operator(_op, ref args, _) => {
                         for &arg in args {
                             let arg = f.resolve_alias(arg);
                             counts.add(arg);
@@ -52,7 +52,7 @@ impl UseCountAnalysis {
                             }
                         }
                     }
-                    &ValueDef::PickOutput(value, _) => {
+                    &ValueDef::PickOutput(value, _, _) => {
                         let value = f.resolve_alias(value);
                         counts.add(value);
                         if counts.use_count[value.index()] == 1 {
@@ -61,7 +61,7 @@ impl UseCountAnalysis {
                             }
                         }
                     }
-                    &ValueDef::Placeholder => {
+                    &ValueDef::Placeholder(_) => {
                         panic!("Unresolved placeholder for value {}", value);
                     }
                 }