WIP.

src/cfg/serialize.rs

@@ -3,12 +3,20 @@
 //! in Wasm function body. Contains everything needed to emit Wasm
 //! except for value locations (and corresponding local spill/reloads).
 
+use std::collections::VecDeque;
+
+use fxhash::{FxHashMap, FxHashSet};
+
 use super::{
     structured::{BlockOrder, BlockOrderEntry, BlockOrderTarget},
     CFGInfo,
 };
-use crate::{BlockId, FunctionBody, Value};
+use crate::{BlockId, FunctionBody, Operator, Terminator, Value, ValueDef};
 
+/// A Wasm function body with a serialized sequence of operators that
+/// mirror Wasm opcodes in every way *except* for locals corresponding
+/// to SSA values. This is a sort of "pre-regalloc" representation of
+/// the final code.
 #[derive(Clone, Debug)]
 pub struct SerializedBody {
     pub(crate) operators: Vec<SerializedOperator>,
@@ -16,8 +24,8 @@ pub struct SerializedBody {
 
 #[derive(Clone, Debug)]
 pub enum SerializedBlockTarget {
-    Fallthrough(Vec<Value>),
-    Branch(usize, Vec<Value>),
+    Fallthrough(Vec<SerializedOperator>),
+    Branch(usize, Vec<SerializedOperator>),
 }
 
 #[derive(Clone, Debug)]
@@ -28,7 +36,7 @@ pub enum SerializedOperator {
     },
     StartLoop {
         header: BlockId,
-        param: Vec<(wasmparser::Type, Value)>,
+        params: Vec<(wasmparser::Type, Value)>,
     },
     Br(SerializedBlockTarget),
     BrIf {
@@ -41,43 +49,563 @@ pub enum SerializedOperator {
         targets: Vec<SerializedBlockTarget>,
         default: SerializedBlockTarget,
     },
-    Operator(Value),
+    /// Compute the given value. Stack discipline will be maintained:
+    /// all operands will be computed or fetched via `Get` and all
+    /// produced results will be used directly or stored via `Set`.
+    Operator(Operator),
+    /// Get the given value from the local corresponding to the
+    /// `Value`'s n'th result.
+    Get(Value, usize),
+    /// Set the local corresponding to the `Value`'s n'th result,
+    /// consuming the value on the stack.
+    Set(Value, usize),
+    /// Set the value, like `Set`, but without consuming it from the
+    /// stack.
+    Tee(Value, usize),
+    /// Get the given function argument.
+    GetArg(usize),
     End,
 }
 
+impl SerializedOperator {
+    pub fn visit_value_locals<R: FnMut(Value, usize), W: FnMut(Value, usize)>(
+        &self,
+        mut r: R,
+        mut w: W,
+    ) {
+        match self {
+            &SerializedOperator::Br(ref target) => {
+                target.visit_value_locals(&mut r, &mut w);
+            }
+            &SerializedOperator::BrIf {
+                cond,
+                ref if_true,
+                ref if_false,
+            } => {
+                r(cond, 0);
+                if_true.visit_value_locals(&mut r, &mut w);
+                if_false.visit_value_locals(&mut r, &mut w);
+            }
+            &SerializedOperator::BrTable {
+                index,
+                ref default,
+                ref targets,
+            } => {
+                r(index, 0);
+                default.visit_value_locals(&mut r, &mut w);
+                for target in targets {
+                    target.visit_value_locals(&mut r, &mut w);
+                }
+            }
+            &SerializedOperator::Get(v, i) => {
+                r(v, i);
+            }
+            &SerializedOperator::Set(v, i) | &SerializedOperator::Tee(v, i) => {
+                w(v, i);
+            }
+            &SerializedOperator::StartBlock { ref params, .. }
+            | &SerializedOperator::StartLoop { ref params, .. } => {
+                for &(_, value) in params {
+                    w(value, 0);
+                }
+            }
+            &SerializedOperator::GetArg(..)
+            | &SerializedOperator::Operator(..)
+            | &SerializedOperator::End => {}
+        }
+    }
+}
+
+impl SerializedBlockTarget {
+    fn visit_value_locals<R: FnMut(Value, usize), W: FnMut(Value, usize)>(
+        &self,
+        r: &mut R,
+        w: &mut W,
+    ) {
+        match self {
+            &SerializedBlockTarget::Branch(_, ref ops)
+            | &SerializedBlockTarget::Fallthrough(ref ops) => {
+                for op in ops {
+                    op.visit_value_locals(|value, i| r(value, i), |value, i| w(value, i));
+                }
+            }
+        }
+    }
+}
+
+struct SerializedBodyContext<'a> {
+    f: &'a FunctionBody,
+    cfg: &'a CFGInfo,
+    uses: &'a UseCountAnalysis,
+    schedule: &'a Schedule,
+    operators: Vec<SerializedOperator>,
+}
+
 impl SerializedBody {
     pub fn compute(f: &FunctionBody, cfg: &CFGInfo, order: &BlockOrder) -> SerializedBody {
-        let mut operators = vec![];
+        let uses = UseCountAnalysis::compute(f);
+        let schedule = Schedule::compute(f, cfg, &uses);
+        let mut ctx = SerializedBodyContext {
+            f,
+            cfg,
+            uses: &uses,
+            schedule: &schedule,
+            operators: vec![],
+        };
         for entry in &order.entries {
-            Self::compute_entry(f, cfg, entry, &mut operators);
+            ctx.compute_entry(entry);
+        }
+        SerializedBody {
+            operators: ctx.operators,
+        }
     }
-        SerializedBody { operators }
 }
 
-    fn compute_entry(
-        f: &FunctionBody,
-        cfg: &CFGInfo,
-        entry: &BlockOrderEntry,
-        operators: &mut Vec<SerializedOperator>,
-    ) {
+impl<'a> SerializedBodyContext<'a> {
+    fn compute_entry(&mut self, entry: &BlockOrderEntry) {
         match entry {
-            &BlockOrderEntry::StartBlock(header, ref params) => {
-                operators.push(SerializedOperator::StartBlock {
+            &BlockOrderEntry::StartBlock(header, ref params)
+            | &BlockOrderEntry::StartLoop(header, ref params) => {
+                let is_loop = match entry {
+                    &BlockOrderEntry::StartLoop(..) => true,
+                    _ => false,
+                };
+
+                if is_loop {
+                    self.operators.push(SerializedOperator::StartLoop {
+                        header,
+                        params: params.clone(),
+                    });
+                } else {
+                    self.operators.push(SerializedOperator::StartBlock {
                         header,
                         params: params.clone(),
                     });
                 }
-            &BlockOrderEntry::StartLoop(header, ref params) => {
-                operators.push(SerializedOperator::StartBlock {
-                    header,
-                    params: params.clone(),
-                });
+
+                // Save params that are on the stack into
+                // locals. TODO: reuse one or more values immediately
+                // if ready-to-schedule ops can use them.
+                for &(_, value) in params.iter().rev() {
+                    self.operators.push(SerializedOperator::Set(value, 0));
+                }
             }
             &BlockOrderEntry::End => {
-                operators.push(SerializedOperator::End);
+                self.operators.push(SerializedOperator::End);
             }
             &BlockOrderEntry::BasicBlock(block, ref targets) => {
-                todo!()
+                // Schedule ops. First handle the compute-at-top ones.
+                if let Some(compute_at_top) = self.schedule.compute_at_top_of_block.get(&block) {
+                    self.schedule_ops(None, &compute_at_top[..]);
+                }
+
+                // Next schedule all toplevels, and values ready to
+                // schedule after each one.
+                for &inst in &self.f.blocks[block].insts {
+                    if let Some(after) = self.schedule.compute_after_value.get(&inst) {
+                        self.schedule_ops(Some(inst), &after[..]);
+                    }
+                }
+
+                // For each BlockOrderTarget, compute a SerializedBlockTarget.
+                let targets = targets
+                    .iter()
+                    .map(|target| {
+                        let mut rev_ops = vec![];
+                        for &value in target.args.iter().rev() {
+                            self.push_value(value, &mut rev_ops);
+                        }
+                        rev_ops.reverse();
+                        match target.relative_branch {
+                            Some(branch) => SerializedBlockTarget::Branch(branch, rev_ops),
+                            None => SerializedBlockTarget::Fallthrough(rev_ops),
+                        }
+                    })
+                    .collect::<Vec<_>>();
+
+                // Finally, generate branch ops.
+                match &self.f.blocks[block].terminator {
+                    &Terminator::Br { .. } => {
+                        let target = targets.into_iter().next().unwrap();
+                        self.operators.push(SerializedOperator::Br(target));
+                    }
+                    &Terminator::CondBr { cond, .. } => {
+                        let mut iter = targets.into_iter();
+                        let if_true = iter.next().unwrap();
+                        let if_false = iter.next().unwrap();
+                        self.operators.push(SerializedOperator::BrIf {
+                            cond,
+                            if_true,
+                            if_false,
+                        });
+                    }
+                    &Terminator::Select { value, .. } => {
+                        let mut iter = targets.into_iter();
+                        let default = iter.next().unwrap();
+                        let targets = iter.collect::<Vec<_>>();
+                        self.operators.push(SerializedOperator::BrTable {
+                            index: value,
+                            targets,
+                            default,
+                        });
+                    }
+                    &Terminator::Return { ref values, .. } => {
+                        let mut rev_ops = vec![];
+                        for &value in values.iter().rev() {
+                            self.push_value(value, &mut rev_ops);
+                        }
+                        rev_ops.reverse();
+                        self.operators.extend(rev_ops.into_iter());
+                        self.operators
+                            .push(SerializedOperator::Operator(Operator::Return));
+                    }
+                    &Terminator::None => {
+                        self.operators
+                            .push(SerializedOperator::Operator(Operator::Unreachable));
+                    }
+                }
+            }
+        }
+    }
+
+    fn schedule_ops(&mut self, toplevel: Option<Value>, values: &[Value]) {
+        // Work backward, generating values in the appropriate order
+        // on the stack if single-use.
+        let mut rev_ops = vec![];
+        let mut to_compute = values
+            .iter()
+            .chain(toplevel.iter())
+            .cloned()
+            .collect::<FxHashSet<_>>();
+        for &value in values.iter().rev() {
+            self.schedule_op(
+                value,
+                &mut rev_ops,
+                /* leave_value_on_stack = */ false,
+                &mut to_compute,
+            );
+        }
+        if let Some(toplevel) = toplevel {
+            self.schedule_op(
+                toplevel,
+                &mut rev_ops,
+                /* leave_value_on_stack = */ false,
+                &mut to_compute,
+            );
+        }
+        rev_ops.reverse();
+        self.operators.extend(rev_ops.into_iter());
+    }
+
+    fn push_value(&mut self, v: Value, rev_ops: &mut Vec<SerializedOperator>) {
+        match &self.f.values[v.index()] {
+            &ValueDef::PickOutput(v, i) => {
+                rev_ops.push(SerializedOperator::Get(v, i));
+            }
+            &ValueDef::Arg(i) => {
+                rev_ops.push(SerializedOperator::GetArg(i));
+            }
+            _ => {
+                rev_ops.push(SerializedOperator::Get(v, 0));
+            }
+        }
+    }
+
+    fn schedule_op(
+        &mut self,
+        op: Value,
+        rev_ops: &mut Vec<SerializedOperator>,
+        leave_value_on_stack: bool,
+        to_compute: &mut FxHashSet<Value>,
+    ) {
+        let op = self.f.resolve_alias(op);
+        if !to_compute.remove(&op) {
+            if leave_value_on_stack {
+                self.push_value(op, rev_ops);
+            }
+            return;
+        }
+
+        let (operator, operands) = match &self.f.values[op.index()] {
+            &ValueDef::Operator(op, ref operands) => (op, operands),
+            _ => {
+                return;
+            }
+        };
+
+        // We're generating ops in reverse order. So we must first
+        // store value.
+        for i in (0..self.f.types[op.index()].len()).rev() {
+            if !leave_value_on_stack {
+                rev_ops.push(SerializedOperator::Set(op, i));
+            } else {
+                assert_eq!(i, 0);
+                if self.uses.use_count[op.index()] > 1 {
+                    rev_ops.push(SerializedOperator::Tee(op, i));
+                }
+            }
+        }
+
+        rev_ops.push(SerializedOperator::Operator(operator));
+
+        // Now push the args in reverse order.
+        for &arg in operands.iter().rev() {
+            match &self.f.values[arg.index()] {
+                &ValueDef::Operator(..) => {
+                    if self.uses.use_count[arg.index()] == 1 && self.f.types[arg.index()].len() == 1
+                    {
+                        self.schedule_op(
+                            arg, rev_ops, /* leave_on_stack = */ true, to_compute,
+                        );
+                    } else {
+                        self.push_value(arg, rev_ops);
+                    }
+                }
+                _ => {
+                    self.push_value(arg, rev_ops);
+                }
+            }
+        }
+    }
+}
+
+#[derive(Clone, Debug)]
+pub struct UseCountAnalysis {
+    toplevel: FxHashSet<Value>,
+    use_count: Vec</* Value, */ usize>,
+}
+
+impl UseCountAnalysis {
+    fn compute(f: &FunctionBody) -> UseCountAnalysis {
+        let n_values = f.values.len();
+        let mut counts = UseCountAnalysis {
+            use_count: vec![0; n_values],
+            toplevel: FxHashSet::default(),
+        };
+
+        let mut workqueue = VecDeque::new();
+        let mut workqueue_set = FxHashSet::default();
+        for block in 0..f.blocks.len() {
+            for &value in &f.blocks[block].insts {
+                let value = f.resolve_alias(value);
+                if workqueue_set.insert(value) {
+                    workqueue.push_back(value);
+                }
+                counts.toplevel.insert(value);
+            }
+
+            while let Some(value) = workqueue.pop_front() {
+                workqueue_set.remove(&value);
+                counts.add(value);
+                match &f.values[value.index()] {
+                    &ValueDef::Alias(..) | &ValueDef::Arg(..) | &ValueDef::BlockParam(..) => {}
+                    &ValueDef::Operator(_op, ref args) => {
+                        for &arg in args {
+                            let arg = f.resolve_alias(arg);
+                            if counts.use_count[arg.index()] == 0 {
+                                if workqueue_set.insert(arg) {
+                                    workqueue.push_back(arg);
+                                }
+                            }
+                        }
+                    }
+                    &ValueDef::PickOutput(value, _) => {
+                        let value = f.resolve_alias(value);
+                        if counts.use_count[value.index()] == 0 {
+                            if workqueue_set.insert(value) {
+                                workqueue.push_back(value);
+                            }
+                        }
+                    }
+                    &ValueDef::Placeholder => {
+                        panic!("Unresolved placeholder for value {}", value);
+                    }
+                }
+            }
+        }
+
+        counts
+    }
+
+    fn add(&mut self, value: Value) {
+        self.use_count[value.index()] += 1;
+    }
+}
+
+#[derive(Clone, Debug, Default)]
+pub struct Schedule {
+    /// Output: location at which to compute each value.
+    pub location: Vec</* Value, */ Location>,
+    /// Output: for each toplevel value, all values that are computed
+    /// after it is.
+    pub compute_after_value: FxHashMap<Value, Vec<Value>>,
+    /// Output: all values ready at the top of a given block.
+    pub compute_at_top_of_block: FxHashMap<BlockId, Vec<Value>>,
+}
+
+pub struct SchedulerContext<'a> {
+    /// The schedule we are constructing.
+    schedule: &'a mut Schedule,
+    /// In-progress state: for each value, the values that have one
+    /// more ready input once that value is computed.
+    waiting_on_value: FxHashMap<Value, Vec<Value>>,
+    /// In-progress state: for each value, how many inputs need to
+    /// become ready.
+    remaining_inputs: FxHashMap<Value, usize>,
+    /// In-progress state: all values that are ready to be scheduled.
+    ready: Vec<Value>,
+    /// Input context: CFG.
+    cfg: &'a CFGInfo,
+    /// Input context: function body.
+    f: &'a FunctionBody,
+}
+
+/// Locations are denoted by top-level values (those in `insts`),
+/// which are those with a side-effect; the sea-of-nodes
+/// representation for all other value nodes allows them to be
+/// computed anywhere dominated by all operands and that dominates all
+/// uses, so we have significant flexibility. We denote a location as
+/// "after a toplevel", then in the second pass where we actually
+/// generate operators according to stack discipline, we resolve the
+/// order for all values at a given toplevel.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum Location {
+    /// At a separate top-level location.
+    Toplevel,
+    /// After a given value.
+    After(Value),
+    /// At the top of a given block.
+    BlockTop(BlockId),
+    /// Not yet scheduled.
+    None,
+}
+
+impl Schedule {
+    pub fn compute(f: &FunctionBody, cfg: &CFGInfo, uses: &UseCountAnalysis) -> Self {
+        let mut schedule = Schedule::default();
+        schedule.location = vec![Location::None; f.values.len()];
+
+        let mut ctx = SchedulerContext {
+            schedule: &mut schedule,
+            f,
+            cfg,
+            waiting_on_value: FxHashMap::default(),
+            remaining_inputs: FxHashMap::default(),
+            ready: vec![],
+        };
+
+        // Prepare the "waiting on value", "remaining inputs", and
+        // "ready" vectors.
+        for (value, value_def) in f.values() {
+            if uses.use_count[value.index()] == 0 {
+                continue;
+            }
+            match value_def {
+                &ValueDef::Operator(_, ref operands) => {
+                    if operands.len() == 0 {
+                        ctx.ready.push(value);
+                    } else {
+                        ctx.remaining_inputs.insert(value, operands.len());
+                        for &input in operands {
+                            let input = f.resolve_alias(input);
+                            ctx.waiting_on_value
+                                .entry(input)
+                                .or_insert_with(|| vec![])
+                                .push(value);
+                        }
+                    }
+                }
+                &ValueDef::Alias(v) | &ValueDef::PickOutput(v, _) => {
+                    let v = f.resolve_alias(v);
+                    ctx.remaining_inputs.insert(v, 1);
+                    ctx.waiting_on_value
+                        .entry(v)
+                        .or_insert_with(|| vec![])
+                        .push(value);
+                }
+                _ => {}
+            }
+        }
+
+        // Traverse blocks in RPO. When we schedule a given op, we've
+        // already scheduled all of its operands, so we can find the
+        // right place for it without any sort of backtracking or
+        // fixpoint convergence.
+        //
+        // - Values in `insts` (toplevel operations)
+        //   are scheduled at their locations. All side-effecting ops
+        //   are in this category, and hence never experience
+        //   code-motion relative to other side-effecting ops or
+        //   control flow.
+        //
+        // - Otherwise, values are scheduled after their last operand
+        //   is ready. All operands must have been computed by the
+        //   time we reach a given operator in RPO, and each operand's
+        //   scheduled site must dominate the current location
+        //   (toplevel value). Because the dominance relation forms a
+        //   tree structure (the domtree), for any two operand def
+        //   sites X and Y to the current location L, given X dom L
+        //   and Y dom L, either X dom Y or Y dom X. Thus, consider
+        //   the current-best and each new operand in pairs, and pick
+        //   the one that is dominated by the other.
+
+        for &block in cfg.postorder.iter().rev() {
+            for &(_, param) in &f.blocks[block].params {
+                ctx.wake_dependents(param);
+            }
+            for &inst in &f.blocks[block].insts {
+                ctx.sched_toplevel(inst);
+            }
+        }
+
+        schedule
+    }
+}
+
+impl<'a> SchedulerContext<'a> {
+    fn sched_toplevel(&mut self, v: Value) {
+        assert_eq!(self.schedule.location[v.index()], Location::None);
+        self.schedule.location[v.index()] = Location::Toplevel;
+        self.wake_dependents(v);
+    }
+
+    fn sched_ready_after_value(&mut self, v: Value) {
+        while !self.ready.is_empty() {
+            for ready in std::mem::take(&mut self.ready) {
+                self.schedule.location[ready.index()] = Location::After(v);
+                self.schedule
+                    .compute_after_value
+                    .entry(v)
+                    .or_insert_with(|| vec![])
+                    .push(ready);
+                self.wake_dependents(ready);
+            }
+        }
+    }
+
+    fn sched_ready_at_block_top(&mut self, block: BlockId) {
+        while !self.ready.is_empty() {
+            for ready in std::mem::take(&mut self.ready) {
+                self.schedule.location[ready.index()] = Location::BlockTop(block);
+                self.schedule
+                    .compute_at_top_of_block
+                    .entry(block)
+                    .or_insert_with(|| vec![])
+                    .push(ready);
+                self.wake_dependents(ready);
+            }
+        }
+    }
+
+    fn wake_dependents(&mut self, v: Value) {
+        let dependents = self.waiting_on_value.remove(&v).unwrap_or_default();
+        for dependent in dependents {
+            let remaining = self.remaining_inputs.get_mut(&dependent).unwrap();
+            *remaining -= 1;
+            if *remaining == 0 {
+                self.remaining_inputs.remove(&dependent);
+                self.ready.push(dependent);
+                self.wake_dependents(dependent);
             }
         }
     }

src/frontend.rs

@@ -131,7 +131,7 @@ fn parse_body<'a>(
 
     for (arg_idx, &arg_ty) in module.signatures[my_sig].params.iter().enumerate() {
         let local_idx = arg_idx as LocalId;
-        let value = builder.body.add_value(ValueDef::Arg(arg_idx), Some(arg_ty));
+        let value = builder.body.add_value(ValueDef::Arg(arg_idx), vec![arg_ty]);
         trace!("defining local {} to value {}", local_idx, value);
         builder.locals.declare(local_idx, arg_ty);
         builder.locals.set(local_idx, value);
@@ -295,11 +295,11 @@ impl LocalTracker {
         match ty {
             Type::I32 => body.add_value(
                 ValueDef::Operator(Operator::I32Const { value: 0 }, vec![]),
-                Some(ty),
+                vec![ty],
             ),
             Type::I64 => body.add_value(
                 ValueDef::Operator(Operator::I64Const { value: 0 }, vec![]),
-                Some(ty),
+                vec![ty],
             ),
             Type::F32 => body.add_value(
                 ValueDef::Operator(
@@ -308,7 +308,7 @@ impl LocalTracker {
                     },
                     vec![],
                 ),
-                Some(ty),
+                vec![ty],
             ),
             Type::F64 => body.add_value(
                 ValueDef::Operator(
@@ -317,7 +317,7 @@ impl LocalTracker {
                     },
                     vec![],
                 ),
-                Some(ty),
+                vec![ty],
             ),
             _ => todo!("unsupported type: {:?}", ty),
         }
@@ -1173,16 +1173,12 @@ impl<'a, 'b> FunctionBodyBuilder<'a, 'b> {
         }
         input_operands.reverse();
         log::trace!(" -> operands: {:?}", input_operands);
+        log::trace!(" -> ty {:?}", outputs);
 
-        let ty = if n_outputs == 1 {
-            Some(outputs[0])
-        } else {
-            None
-        };
         let value = self
             .body
-            .add_value(ValueDef::Operator(op, input_operands), ty);
-        log::trace!(" -> value: {:?} ty {:?}", value, ty);
+            .add_value(ValueDef::Operator(op, input_operands), outputs.clone());
+        log::trace!(" -> value: {:?}", value);
 
         if let Some(block) = self.cur_block {
             if !op_effects(&op).unwrap().is_empty() {
@@ -1197,7 +1193,7 @@ 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), Some(output_ty));
+                    .add_value(ValueDef::PickOutput(value, i), vec![output_ty]);
                 self.op_stack.push((output_ty, pick));
                 log::trace!(" -> pick {}: {:?} ty {:?}", i, pick, output_ty);
             }

src/ir.rs

@@ -4,6 +4,7 @@ use std::collections::hash_map::Entry;
 
 use crate::{
     cfg::{
+        serialize::SerializedBody,
         structured::{BlockOrder, LoopNest, WasmRegion},
         CFGInfo,
     },
@@ -55,7 +56,9 @@ pub struct FunctionBody {
     /// Sea-of-nodes representation.
     pub values: Vec<ValueDef>,
     value_dedup: FxHashMap<ValueDef, Value>,
-    pub types: Vec</* Value, */ Option<Type>>,
+    /// A single value can have multiple types if multi-value (e.g. a
+    /// call).
+    pub types: Vec</* Value, */ Vec<Type>>,
 }
 
 impl FunctionBody {
@@ -77,18 +80,19 @@ impl FunctionBody {
         log::trace!("add_edge: from {} to {}", from, to);
     }
 
-    pub fn add_value(&mut self, value: ValueDef, ty: Option<Type>) -> Value {
+    pub fn add_value(&mut self, value: ValueDef, tys: Vec<Type>) -> Value {
+        log::trace!("add_value: def {:?} ty {:?}", value, tys);
         let id = match self.value_dedup.entry(value.clone()) {
             Entry::Occupied(o) => *o.get(),
             Entry::Vacant(v) => {
                 let id = Value(self.values.len() as u32);
                 self.values.push(value.clone());
-                self.types.push(ty);
+                self.types.push(tys);
                 v.insert(id);
                 id
             }
         };
-        log::trace!("add_value: def {:?} ty {:?} -> {:?}", value, ty, id);
+        log::trace!(" -> value {:?}", id);
         id
     }
 
@@ -116,27 +120,27 @@ impl FunctionBody {
         result
     }
 
-    pub fn add_mutable_inst(&mut self, ty: Option<Type>, def: ValueDef) -> Value {
+    pub fn add_mutable_inst(&mut self, tys: Vec<Type>, def: ValueDef) -> Value {
         let value = Value(self.values.len() as u32);
-        self.types.push(ty);
+        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), Some(ty));
+        let value = self.add_value(ValueDef::BlockParam(block, index), vec![ty]);
         self.blocks[block].params.push((ty, value));
         value
     }
 
     pub fn add_placeholder(&mut self, ty: Type) -> Value {
-        self.add_mutable_inst(Some(ty), ValueDef::Placeholder)
+        self.add_mutable_inst(vec![ty], ValueDef::Placeholder)
     }
 
     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()].unwrap();
+        let ty = self.types[value.index()].get(0).cloned().unwrap();
         let index = self.blocks[block].params.len();
         self.blocks[block].params.push((ty, value));
         self.values[value.index()] = ValueDef::BlockParam(block, index);
@@ -169,6 +173,13 @@ impl FunctionBody {
         self.locals.push(ty);
         id
     }
+
+    pub fn values<'a>(&'a self) -> impl Iterator<Item = (Value, &'a ValueDef)> + 'a {
+        self.values
+            .iter()
+            .enumerate()
+            .map(|(idx, value_def)| (Value(idx as u32), value_def))
+    }
 }
 
 impl std::ops::Index<Value> for FunctionBody {
@@ -481,7 +492,9 @@ impl<'a> Module<'a> {
                     let cfg = CFGInfo::new(body);
                     let loopnest = LoopNest::compute(&cfg);
                     let regions = WasmRegion::compute(&cfg, &loopnest);
-                    let _blockorder = BlockOrder::compute(body, &cfg, &regions);
+                    let blockorder = BlockOrder::compute(body, &cfg, &regions);
+                    let serialized = SerializedBody::compute(body, &cfg, &blockorder);
+                    log::trace!("serialized:{:?}", serialized);
                 }
                 _ => {}
             }