diff --git a/src/compiler/wasm-compiler.cc b/src/compiler/wasm-compiler.cc
index 1f3da08579..4daa7cba1e 100644
--- a/src/compiler/wasm-compiler.cc
+++ b/src/compiler/wasm-compiler.cc
@@ -2409,15 +2409,6 @@ Handle<Code> CompileWasmFunction(wasm::ErrorThrower& thrower, Isolate* isolate,
        << wasm::WasmFunctionName(&function, module_env) << std::endl;
     os << std::endl;
   }
-  // Initialize the function environment for decoding.
-  wasm::FunctionEnv env;
-  env.module = module_env;
-  env.sig = function.sig;
-  env.local_i32_count = function.local_i32_count;
-  env.local_i64_count = function.local_i64_count;
-  env.local_f32_count = function.local_f32_count;
-  env.local_f64_count = function.local_f64_count;
-  env.SumLocals();
 
   // Create a TF graph during decoding.
   Zone zone;
@@ -2428,11 +2419,11 @@ Handle<Code> CompileWasmFunction(wasm::ErrorThrower& thrower, Isolate* isolate,
       InstructionSelector::SupportedMachineOperatorFlags());
   JSGraph jsgraph(isolate, &graph, &common, nullptr, nullptr, &machine);
   WasmGraphBuilder builder(&zone, &jsgraph, function.sig);
-  wasm::TreeResult result = wasm::BuildTFGraph(
-      &builder, &env,                                                 // --
-      module_env->module->module_start,                               // --
-      module_env->module->module_start + function.code_start_offset,  // --
-      module_env->module->module_start + function.code_end_offset);   // --
+  wasm::FunctionBody body = {
+      module_env, function.sig, module_env->module->module_start,
+      module_env->module->module_start + function.code_start_offset,
+      module_env->module->module_start + function.code_end_offset};
+  wasm::TreeResult result = wasm::BuildTFGraph(&builder, body);
 
   if (result.failed()) {
     if (FLAG_trace_wasm_compiler) {
diff --git a/src/wasm/ast-decoder.cc b/src/wasm/ast-decoder.cc
index e56991a482..78f50739dd 100644
--- a/src/wasm/ast-decoder.cc
+++ b/src/wasm/ast-decoder.cc
@@ -52,7 +52,6 @@ struct Production {
   Tree* last() const { return index > 0 ? tree->children[index - 1] : nullptr; }
 };
 
-
 // An SsaEnv environment carries the current local variable renaming
 // as well as the current effect and control dependency in the TF graph.
 // It maintains a control state that tracks whether the environment
@@ -74,14 +73,12 @@ struct SsaEnv {
   }
 };
 
-
 // An entry in the stack of blocks during decoding.
 struct Block {
   SsaEnv* ssa_env;  // SSA renaming environment.
   int stack_depth;  // production stack depth.
 };
 
-
 // An entry in the stack of ifs during decoding.
 struct IfEnv {
   SsaEnv* false_env;
@@ -89,27 +86,27 @@ struct IfEnv {
   SsaEnv** case_envs;
 };
 
-
 // Macros that build nodes only if there is a graph and the current SSA
 // environment is reachable from start. This avoids problems with malformed
 // TF graphs when decoding inputs that have unreachable code.
 #define BUILD(func, ...) (build() ? builder_->func(__VA_ARGS__) : nullptr)
 #define BUILD0(func) (build() ? builder_->func() : nullptr)
 
-
 // Generic Wasm bytecode decoder with utilities for decoding operands,
 // lengths, etc.
 class WasmDecoder : public Decoder {
  public:
-  WasmDecoder() : Decoder(nullptr, nullptr), function_env_(nullptr) {}
-  WasmDecoder(FunctionEnv* env, const byte* start, const byte* end)
-      : Decoder(start, end), function_env_(env) {}
-  FunctionEnv* function_env_;
-
-  void Reset(FunctionEnv* function_env, const byte* start, const byte* end) {
-    Decoder::Reset(start, end);
-    function_env_ = function_env;
-  }
+  WasmDecoder(ModuleEnv* module, FunctionSig* sig, const byte* start,
+              const byte* end)
+      : Decoder(start, end),
+        module_(module),
+        sig_(sig),
+        total_locals_(0),
+        local_types_(nullptr) {}
+  ModuleEnv* module_;
+  FunctionSig* sig_;
+  size_t total_locals_;
+  ZoneVector<LocalType>* local_types_;
 
   byte ByteOperand(const byte* pc, const char* msg = "missing 1-byte operand") {
     if ((pc + sizeof(byte)) >= limit_) {
@@ -136,8 +133,12 @@ class WasmDecoder : public Decoder {
   }
 
   inline bool Validate(const byte* pc, LocalIndexOperand& operand) {
-    if (operand.index < function_env_->total_locals) {
-      operand.type = function_env_->GetLocalType(operand.index);
+    if (operand.index < total_locals_) {
+      if (local_types_) {
+        operand.type = local_types_->at(operand.index);
+      } else {
+        operand.type = kAstStmt;
+      }
       return true;
     }
     error(pc, pc + 1, "invalid local index");
@@ -145,7 +146,7 @@ class WasmDecoder : public Decoder {
   }
 
   inline bool Validate(const byte* pc, GlobalIndexOperand& operand) {
-    ModuleEnv* m = function_env_->module;
+    ModuleEnv* m = module_;
     if (m && m->module && operand.index < m->module->globals.size()) {
       operand.machine_type = m->module->globals[operand.index].type;
       operand.type = WasmOpcodes::LocalTypeFor(operand.machine_type);
@@ -156,7 +157,7 @@ class WasmDecoder : public Decoder {
   }
 
   inline bool Validate(const byte* pc, FunctionIndexOperand& operand) {
-    ModuleEnv* m = function_env_->module;
+    ModuleEnv* m = module_;
     if (m && m->module && operand.index < m->module->functions.size()) {
       operand.sig = m->module->functions[operand.index].sig;
       return true;
@@ -166,7 +167,7 @@ class WasmDecoder : public Decoder {
   }
 
   inline bool Validate(const byte* pc, SignatureIndexOperand& operand) {
-    ModuleEnv* m = function_env_->module;
+    ModuleEnv* m = module_;
     if (m && m->module && operand.index < m->module->signatures.size()) {
       operand.sig = m->module->signatures[operand.index];
       return true;
@@ -176,7 +177,7 @@ class WasmDecoder : public Decoder {
   }
 
   inline bool Validate(const byte* pc, ImportIndexOperand& operand) {
-    ModuleEnv* m = function_env_->module;
+    ModuleEnv* m = module_;
     if (m && m->module && operand.index < m->module->import_table.size()) {
       operand.sig = m->module->import_table[operand.index].sig;
       return true;
@@ -250,23 +251,20 @@ class WasmDecoder : public Decoder {
       case kExprCallFunction: {
         FunctionIndexOperand operand(this, pc);
         return static_cast<int>(
-            function_env_->module->GetFunctionSignature(operand.index)
-                ->parameter_count());
+            module_->GetFunctionSignature(operand.index)->parameter_count());
       }
       case kExprCallIndirect: {
         SignatureIndexOperand operand(this, pc);
         return 1 + static_cast<int>(
-                       function_env_->module->GetSignature(operand.index)
-                           ->parameter_count());
+                       module_->GetSignature(operand.index)->parameter_count());
       }
       case kExprCallImport: {
         ImportIndexOperand operand(this, pc);
         return static_cast<int>(
-            function_env_->module->GetImportSignature(operand.index)
-                ->parameter_count());
+            module_->GetImportSignature(operand.index)->parameter_count());
       }
       case kExprReturn: {
-        return static_cast<int>(function_env_->sig->return_count());
+        return static_cast<int>(sig_->return_count());
       }
       case kExprBrTable: {
         return 1;
@@ -282,9 +280,11 @@ class WasmDecoder : public Decoder {
         FOREACH_SIMPLE_OPCODE(DECLARE_OPCODE_CASE)
         FOREACH_ASMJS_COMPAT_OPCODE(DECLARE_OPCODE_CASE)
 #undef DECLARE_OPCODE_CASE
+      case kExprDeclLocals:
+      default:
+        UNREACHABLE();
+        return 0;
     }
-    UNREACHABLE();
-    return 0;
   }
 
   int OpcodeLength(const byte* pc) {
@@ -353,35 +353,33 @@ class WasmDecoder : public Decoder {
 
 // A shift-reduce-parser strategy for decoding Wasm code that uses an explicit
 // shift-reduce strategy with multiple internal stacks.
-class LR_WasmDecoder : public WasmDecoder {
+class SR_WasmDecoder : public WasmDecoder {
  public:
-  LR_WasmDecoder(Zone* zone, TFBuilder* builder)
-      : zone_(zone),
+  SR_WasmDecoder(Zone* zone, TFBuilder* builder, FunctionBody& body)
+      : WasmDecoder(body.module, body.sig, body.start, body.end),
+        zone_(zone),
         builder_(builder),
+        base_(body.base),
+        local_type_vec_(zone),
         trees_(zone),
         stack_(zone),
         blocks_(zone),
-        ifs_(zone) {}
+        ifs_(zone) {
+    local_types_ = &local_type_vec_;
+  }
 
-  TreeResult Decode(FunctionEnv* function_env, const byte* base, const byte* pc,
-                    const byte* end) {
+  TreeResult Decode() {
     base::ElapsedTimer decode_timer;
     if (FLAG_trace_wasm_decode_time) {
       decode_timer.Start();
     }
-    trees_.clear();
-    stack_.clear();
-    blocks_.clear();
-    ifs_.clear();
 
-    if (end < pc) {
-      error(pc, "function body end < start");
+    if (end_ < pc_) {
+      error(pc_, "function body end < start");
       return result_;
     }
 
-    base_ = base;
-    Reset(function_env, pc, end);
-
+    DecodeLocalDecls();
     InitSsaEnv();
     DecodeFunctionBody();
 
@@ -389,12 +387,12 @@ class LR_WasmDecoder : public WasmDecoder {
     if (ok()) {
       if (ssa_env_->go()) {
         if (stack_.size() > 0) {
-          error(stack_.back().pc(), end, "fell off end of code");
+          error(stack_.back().pc(), end_, "fell off end of code");
         }
         AddImplicitReturnAtEnd();
       }
       if (trees_.size() == 0) {
-        if (function_env_->sig->return_count() > 0) {
+        if (sig_->return_count() > 0) {
           error(start_, "no trees created");
         }
       } else {
@@ -404,7 +402,8 @@ class LR_WasmDecoder : public WasmDecoder {
 
     if (ok()) {
       if (FLAG_trace_wasm_ast) {
-        PrintAst(function_env, pc, end);
+        FunctionBody body = {module_, sig_, base_, start_, end_};
+        PrintAst(body);
       }
       if (FLAG_trace_wasm_decode_time) {
         double ms = decode_timer.Elapsed().InMillisecondsF();
@@ -420,6 +419,28 @@ class LR_WasmDecoder : public WasmDecoder {
     return toResult(tree);
   }
 
+  std::vector<LocalType>* DecodeLocalDeclsForTesting() {
+    DecodeLocalDecls();
+    if (failed()) return nullptr;
+    auto result = new std::vector<LocalType>();
+    result->reserve(local_type_vec_.size());
+    for (size_t i = 0; i < local_type_vec_.size(); i++) {
+      result->push_back(local_type_vec_[i]);
+    }
+    return result;
+  }
+
+  BitVector* AnalyzeLoopAssignmentForTesting(const byte* pc,
+                                             size_t num_locals) {
+    total_locals_ = num_locals;
+    local_type_vec_.reserve(num_locals);
+    if (num_locals > local_type_vec_.size()) {
+      local_type_vec_.insert(local_type_vec_.end(),
+                             num_locals - local_type_vec_.size(), kAstI32);
+    }
+    return AnalyzeLoopAssignment(pc);
+  }
+
  private:
   static const size_t kErrorMsgSize = 128;
 
@@ -430,6 +451,7 @@ class LR_WasmDecoder : public WasmDecoder {
 
   SsaEnv* ssa_env_;
 
+  ZoneVector<LocalType> local_type_vec_;
   ZoneVector<Tree*> trees_;
   ZoneVector<Production> stack_;
   ZoneVector<Block> blocks_;
@@ -438,8 +460,6 @@ class LR_WasmDecoder : public WasmDecoder {
   inline bool build() { return builder_ && ssa_env_->go(); }
 
   void InitSsaEnv() {
-    FunctionSig* sig = function_env_->sig;
-    int param_count = static_cast<int>(sig->parameter_count());
     TFNode* start = nullptr;
     SsaEnv* ssa_env = reinterpret_cast<SsaEnv*>(zone_->New(sizeof(SsaEnv)));
     size_t size = sizeof(TFNode*) * EnvironmentCount();
@@ -447,50 +467,46 @@ class LR_WasmDecoder : public WasmDecoder {
     ssa_env->locals =
         size > 0 ? reinterpret_cast<TFNode**>(zone_->New(size)) : nullptr;
 
-    int pos = 0;
     if (builder_) {
-      start = builder_->Start(param_count + 1);
-      // Initialize parameters.
-      for (int i = 0; i < param_count; i++) {
-        ssa_env->locals[pos++] = builder_->Param(i, sig->GetParam(i));
+      start = builder_->Start(static_cast<int>(sig_->parameter_count() + 1));
+      // Initialize local variables.
+      uint32_t index = 0;
+      while (index < sig_->parameter_count()) {
+        ssa_env->locals[index] = builder_->Param(index, local_type_vec_[index]);
+        index++;
       }
-      // Initialize int32 locals.
-      if (function_env_->local_i32_count > 0) {
-        TFNode* zero = builder_->Int32Constant(0);
-        for (uint32_t i = 0; i < function_env_->local_i32_count; i++) {
-          ssa_env->locals[pos++] = zero;
+      while (index < local_type_vec_.size()) {
+        LocalType type = local_type_vec_[index];
+        TFNode* node = DefaultValue(type);
+        while (index < local_type_vec_.size() &&
+               local_type_vec_[index] == type) {
+          // Do a whole run of like-typed locals at a time.
+          ssa_env->locals[index++] = node;
         }
       }
-      // Initialize int64 locals.
-      if (function_env_->local_i64_count > 0) {
-        TFNode* zero = builder_->Int64Constant(0);
-        for (uint32_t i = 0; i < function_env_->local_i64_count; i++) {
-          ssa_env->locals[pos++] = zero;
-        }
-      }
-      // Initialize float32 locals.
-      if (function_env_->local_f32_count > 0) {
-        TFNode* zero = builder_->Float32Constant(0);
-        for (uint32_t i = 0; i < function_env_->local_f32_count; i++) {
-          ssa_env->locals[pos++] = zero;
-        }
-      }
-      // Initialize float64 locals.
-      if (function_env_->local_f64_count > 0) {
-        TFNode* zero = builder_->Float64Constant(0);
-        for (uint32_t i = 0; i < function_env_->local_f64_count; i++) {
-          ssa_env->locals[pos++] = zero;
-        }
-      }
-      DCHECK_EQ(function_env_->total_locals, pos);
-      DCHECK_EQ(EnvironmentCount(), pos);
-      builder_->set_module(function_env_->module);
+      builder_->set_module(module_);
     }
     ssa_env->control = start;
     ssa_env->effect = start;
     SetEnv("initial", ssa_env);
   }
 
+  TFNode* DefaultValue(LocalType type) {
+    switch (type) {
+      case kAstI32:
+        return builder_->Int32Constant(0);
+      case kAstI64:
+        return builder_->Int64Constant(0);
+      case kAstF32:
+        return builder_->Float32Constant(0);
+      case kAstF64:
+        return builder_->Float64Constant(0);
+      default:
+        UNREACHABLE();
+        return nullptr;
+    }
+  }
+
   void Leaf(LocalType type, TFNode* node = nullptr) {
     size_t size = sizeof(Tree);
     Tree* tree = reinterpret_cast<Tree*>(zone_->New(size));
@@ -549,6 +565,45 @@ class LR_WasmDecoder : public WasmDecoder {
     return bytes;
   }
 
+  // Decodes the locals declarations, if any, populating {local_type_vec_}.
+  void DecodeLocalDecls() {
+    DCHECK_EQ(0, local_type_vec_.size());
+    // Initialize {local_type_vec} from signature.
+    if (sig_) {
+      local_type_vec_.reserve(sig_->parameter_count());
+      for (size_t i = 0; i < sig_->parameter_count(); i++) {
+        local_type_vec_.push_back(sig_->GetParam(i));
+      }
+    }
+    // Decode local declarations, if any.
+    int length;
+    uint32_t entries = consume_u32v(&length, "local decls count");
+    while (entries-- > 0 && pc_ < limit_) {
+      uint32_t count = consume_u32v(&length, "local count");
+      byte code = consume_u8("local type");
+      LocalType type;
+      switch (code) {
+        case kLocalI32:
+          type = kAstI32;
+          break;
+        case kLocalI64:
+          type = kAstI64;
+          break;
+        case kLocalF32:
+          type = kAstF32;
+          break;
+        case kLocalF64:
+          type = kAstF64;
+          break;
+        default:
+          error(pc_ - 1, "invalid local type");
+          return;
+      }
+      local_type_vec_.insert(local_type_vec_.end(), count, type);
+    }
+    total_locals_ = local_type_vec_.size();
+  }
+
   // Decodes the body of a function, producing reduced trees into {result}.
   void DecodeFunctionBody() {
     TRACE("wasm-decode %p...%p (%d bytes) %s\n",
@@ -652,7 +707,7 @@ class LR_WasmDecoder : public WasmDecoder {
           break;
         }
         case kExprReturn: {
-          int count = static_cast<int>(function_env_->sig->return_count());
+          int count = static_cast<int>(sig_->return_count());
           if (count == 0) {
             BUILD(Return, 0, builder_->Buffer(0));
             ssa_env_->Kill();
@@ -809,6 +864,7 @@ class LR_WasmDecoder : public WasmDecoder {
           len = 1 + operand.length;
           break;
         }
+        case kExprDeclLocals:
         default:
           error("Invalid opcode");
           return;
@@ -841,7 +897,7 @@ class LR_WasmDecoder : public WasmDecoder {
   }
 
   void AddImplicitReturnAtEnd() {
-    int retcount = static_cast<int>(function_env_->sig->return_count());
+    int retcount = static_cast<int>(sig_->return_count());
     if (retcount == 0) {
       BUILD0(ReturnVoid);
       return;
@@ -860,7 +916,7 @@ class LR_WasmDecoder : public WasmDecoder {
     for (int index = 0; index < retcount; index++) {
       Tree* tree = trees_[trees_.size() - 1 - index];
       if (buffer) buffer[index] = tree->node;
-      LocalType expected = function_env_->sig->GetReturn(index);
+      LocalType expected = sig_->GetReturn(index);
       if (tree->type != expected) {
         error(limit_, tree->pc,
               "ImplicitReturn[%d] expected type %s, found %s of type %s", index,
@@ -1066,7 +1122,7 @@ class LR_WasmDecoder : public WasmDecoder {
         break;
       }
       case kExprReturn: {
-        TypeCheckLast(p, function_env_->sig->GetReturn(p->index - 1));
+        TypeCheckLast(p, sig_->GetReturn(p->index - 1));
         if (p->done()) {
           if (build()) {
             int count = p->tree->count;
@@ -1346,8 +1402,7 @@ class LR_WasmDecoder : public WasmDecoder {
           TFNode* b = from->locals[i];
           if (a != b) {
             TFNode* vals[] = {a, b};
-            to->locals[i] =
-                builder_->Phi(function_env_->GetLocalType(i), 2, vals, merge);
+            to->locals[i] = builder_->Phi(local_type_vec_[i], 2, vals, merge);
           }
         }
         break;
@@ -1382,8 +1437,8 @@ class LR_WasmDecoder : public WasmDecoder {
               vals[j] = tnode;
             }
             vals[count - 1] = fnode;
-            to->locals[i] = builder_->Phi(function_env_->GetLocalType(i), count,
-                                          vals, merge);
+            to->locals[i] =
+                builder_->Phi(local_type_vec_[i], count, vals, merge);
           }
         }
         break;
@@ -1426,8 +1481,8 @@ class LR_WasmDecoder : public WasmDecoder {
         env->effect = builder_->EffectPhi(1, &env->effect, env->control);
         builder_->Terminate(env->effect, env->control);
         for (int i = EnvironmentCount() - 1; i >= 0; i--) {
-          env->locals[i] = builder_->Phi(function_env_->GetLocalType(i), 1,
-                                         &env->locals[i], env->control);
+          env->locals[i] = builder_->Phi(local_type_vec_[i], 1, &env->locals[i],
+                                         env->control);
         }
       }
     }
@@ -1481,7 +1536,7 @@ class LR_WasmDecoder : public WasmDecoder {
   }
 
   int EnvironmentCount() {
-    if (builder_) return static_cast<int>(function_env_->GetLocalCount());
+    if (builder_) return static_cast<int>(local_type_vec_.size());
     return 0;  // if we aren't building a graph, don't bother with SSA renaming.
   }
 
@@ -1517,23 +1572,68 @@ class LR_WasmDecoder : public WasmDecoder {
     PrintProduction(depth + 1);
   }
 #endif
+
+  BitVector* AnalyzeLoopAssignment(const byte* pc) {
+    if (pc >= limit_) return nullptr;
+    if (*pc != kExprLoop) return nullptr;
+
+    BitVector* assigned =
+        new (zone_) BitVector(static_cast<int>(total_locals_), zone_);
+    // Keep a stack to model the nesting of expressions.
+    std::vector<int> arity_stack;
+    arity_stack.push_back(OpcodeArity(pc));
+    pc += OpcodeLength(pc);
+
+    // Iteratively process all AST nodes nested inside the loop.
+    while (pc < limit_) {
+      WasmOpcode opcode = static_cast<WasmOpcode>(*pc);
+      int arity = 0;
+      int length = 1;
+      if (opcode == kExprSetLocal) {
+        LocalIndexOperand operand(this, pc);
+        if (assigned->length() > 0 &&
+            static_cast<int>(operand.index) < assigned->length()) {
+          // Unverified code might have an out-of-bounds index.
+          assigned->Add(operand.index);
+        }
+        arity = 1;
+        length = 1 + operand.length;
+      } else {
+        arity = OpcodeArity(pc);
+        length = OpcodeLength(pc);
+      }
+
+      pc += length;
+      arity_stack.push_back(arity);
+      while (arity_stack.back() == 0) {
+        arity_stack.pop_back();
+        if (arity_stack.empty()) return assigned;  // reached end of loop
+        arity_stack.back()--;
+      }
+    }
+    return assigned;
+  }
 };
 
-
-TreeResult VerifyWasmCode(FunctionEnv* env, const byte* base, const byte* start,
-                          const byte* end) {
+std::vector<LocalType>* DecodeLocalDeclsForTesting(const byte* start,
+                                                   const byte* end) {
   Zone zone;
-  LR_WasmDecoder decoder(&zone, nullptr);
-  TreeResult result = decoder.Decode(env, base, start, end);
+  FunctionBody body = {nullptr, nullptr, nullptr, start, end};
+  SR_WasmDecoder decoder(&zone, nullptr, body);
+  return decoder.DecodeLocalDeclsForTesting();
+}
+
+TreeResult VerifyWasmCode(FunctionBody& body) {
+  Zone zone;
+  SR_WasmDecoder decoder(&zone, nullptr, body);
+  TreeResult result = decoder.Decode();
   return result;
 }
 
-
-TreeResult BuildTFGraph(TFBuilder* builder, FunctionEnv* env, const byte* base,
-                        const byte* start, const byte* end) {
+TreeResult BuildTFGraph(TFBuilder* builder, FunctionBody& body) {
   Zone zone;
-  LR_WasmDecoder decoder(&zone, builder);
-  TreeResult result = decoder.Decode(env, base, start, end);
+  SR_WasmDecoder decoder(&zone, builder, body);
+  TreeResult result = decoder.Decode();
   return result;
 }
 
@@ -1565,20 +1665,21 @@ ReadUnsignedLEB128ErrorCode ReadUnsignedLEB128Operand(const byte* pc,
 }
 
 int OpcodeLength(const byte* pc, const byte* end) {
-  WasmDecoder decoder(nullptr, pc, end);
+  WasmDecoder decoder(nullptr, nullptr, pc, end);
   return decoder.OpcodeLength(pc);
 }
 
-int OpcodeArity(FunctionEnv* env, const byte* pc, const byte* end) {
-  WasmDecoder decoder(env, pc, end);
+int OpcodeArity(ModuleEnv* module, FunctionSig* sig, const byte* pc,
+                const byte* end) {
+  WasmDecoder decoder(module, sig, pc, end);
   return decoder.OpcodeArity(pc);
 }
 
-void PrintAst(FunctionEnv* env, const byte* start, const byte* end) {
-  WasmDecoder decoder(env, start, end);
-  const byte* pc = start;
+void PrintAst(FunctionBody& body) {
+  WasmDecoder decoder(body.module, body.sig, body.start, body.end);
+  const byte* pc = body.start;
   std::vector<int> arity_stack;
-  while (pc < end) {
+  while (pc < body.end) {
     int arity = decoder.OpcodeArity(pc);
     size_t length = decoder.OpcodeLength(pc);
 
@@ -1605,65 +1706,11 @@ void PrintAst(FunctionEnv* env, const byte* start, const byte* end) {
   }
 }
 
-// Analyzes loop bodies for static assignments to locals, which helps in
-// reducing the number of phis introduced at loop headers.
-class LoopAssignmentAnalyzer : public WasmDecoder {
- public:
-  LoopAssignmentAnalyzer(Zone* zone, FunctionEnv* function_env) : zone_(zone) {
-    function_env_ = function_env;
-  }
-
-  BitVector* Analyze(const byte* pc, const byte* limit) {
-    Decoder::Reset(pc, limit);
-    if (pc_ >= limit_) return nullptr;
-    if (*pc_ != kExprLoop) return nullptr;
-
-    BitVector* assigned =
-        new (zone_) BitVector(function_env_->total_locals, zone_);
-    // Keep a stack to model the nesting of expressions.
-    std::vector<int> arity_stack;
-    arity_stack.push_back(OpcodeArity(pc_));
-    pc_ += OpcodeLength(pc_);
-
-    // Iteratively process all AST nodes nested inside the loop.
-    while (pc_ < limit_) {
-      WasmOpcode opcode = static_cast<WasmOpcode>(*pc_);
-      int arity = 0;
-      int length = 1;
-      if (opcode == kExprSetLocal) {
-        LocalIndexOperand operand(this, pc_);
-        if (assigned->length() > 0 &&
-            static_cast<int>(operand.index) < assigned->length()) {
-          // Unverified code might have an out-of-bounds index.
-          assigned->Add(operand.index);
-        }
-        arity = 1;
-        length = 1 + operand.length;
-      } else {
-        arity = OpcodeArity(pc_);
-        length = OpcodeLength(pc_);
-      }
-
-      pc_ += length;
-      arity_stack.push_back(arity);
-      while (arity_stack.back() == 0) {
-        arity_stack.pop_back();
-        if (arity_stack.empty()) return assigned;  // reached end of loop
-        arity_stack.back()--;
-      }
-    }
-    return assigned;
-  }
-
- private:
-  Zone* zone_;
-};
-
-
-BitVector* AnalyzeLoopAssignmentForTesting(Zone* zone, FunctionEnv* env,
+BitVector* AnalyzeLoopAssignmentForTesting(Zone* zone, size_t num_locals,
                                            const byte* start, const byte* end) {
-  LoopAssignmentAnalyzer analyzer(zone, env);
-  return analyzer.Analyze(start, end);
+  FunctionBody body = {nullptr, nullptr, nullptr, start, end};
+  SR_WasmDecoder decoder(zone, nullptr, body);
+  return decoder.AnalyzeLoopAssignmentForTesting(start, num_locals);
 }
 
 }  // namespace wasm
diff --git a/src/wasm/ast-decoder.h b/src/wasm/ast-decoder.h
index 4693af1ca0..386f6f52b2 100644
--- a/src/wasm/ast-decoder.h
+++ b/src/wasm/ast-decoder.h
@@ -183,61 +183,13 @@ struct MemoryAccessOperand {
 typedef compiler::WasmGraphBuilder TFBuilder;
 struct ModuleEnv;  // forward declaration of module interface.
 
-// Interface the function environment during decoding, include the signature
-// and number of locals.
-struct FunctionEnv {
-  ModuleEnv* module;             // module environment
-  FunctionSig* sig;              // signature of this function
-  uint32_t local_i32_count;      // number of int32 locals
-  uint32_t local_i64_count;      // number of int64 locals
-  uint32_t local_f32_count;      // number of float32 locals
-  uint32_t local_f64_count;      // number of float64 locals
-  uint32_t total_locals;         // sum of parameters and all locals
-
-  uint32_t GetLocalCount() { return total_locals; }
-  LocalType GetLocalType(uint32_t index) {
-    if (index < static_cast<uint32_t>(sig->parameter_count())) {
-      return sig->GetParam(index);
-    }
-    index -= static_cast<uint32_t>(sig->parameter_count());
-    if (index < local_i32_count) return kAstI32;
-    index -= local_i32_count;
-    if (index < local_i64_count) return kAstI64;
-    index -= local_i64_count;
-    if (index < local_f32_count) return kAstF32;
-    index -= local_f32_count;
-    if (index < local_f64_count) return kAstF64;
-    return kAstStmt;
-  }
-
-  void AddLocals(LocalType type, uint32_t count) {
-    switch (type) {
-      case kAstI32:
-        local_i32_count += count;
-        break;
-      case kAstI64:
-        local_i64_count += count;
-        break;
-      case kAstF32:
-        local_f32_count += count;
-        break;
-      case kAstF64:
-        local_f64_count += count;
-        break;
-      default:
-        UNREACHABLE();
-    }
-    total_locals += count;
-    DCHECK_EQ(total_locals,
-              (sig->parameter_count() + local_i32_count + local_i64_count +
-               local_f32_count + local_f64_count));
-  }
-
-  void SumLocals() {
-    total_locals = static_cast<uint32_t>(sig->parameter_count()) +
-                   local_i32_count + local_i64_count + local_f32_count +
-                   local_f64_count;
-  }
+// All of the various data structures necessary to decode a function body.
+struct FunctionBody {
+  ModuleEnv* module;  // module environment
+  FunctionSig* sig;   // function signature
+  const byte* base;   // base of the module bytes, for error reporting
+  const byte* start;  // start of the function body
+  const byte* end;    // end of the function body
 };
 
 struct Tree;
@@ -245,21 +197,21 @@ typedef Result<Tree*> TreeResult;
 
 std::ostream& operator<<(std::ostream& os, const Tree& tree);
 
-TreeResult VerifyWasmCode(FunctionEnv* env, const byte* base, const byte* start,
-                          const byte* end);
-TreeResult BuildTFGraph(TFBuilder* builder, FunctionEnv* env, const byte* base,
-                        const byte* start, const byte* end);
+TreeResult VerifyWasmCode(FunctionBody& body);
+TreeResult BuildTFGraph(TFBuilder* builder, FunctionBody& body);
+void PrintAst(FunctionBody& body);
 
-void PrintAst(FunctionEnv* env, const byte* start, const byte* end);
-
-inline TreeResult VerifyWasmCode(FunctionEnv* env, const byte* start,
-                                 const byte* end) {
-  return VerifyWasmCode(env, nullptr, start, end);
+inline TreeResult VerifyWasmCode(ModuleEnv* module, FunctionSig* sig,
+                                 const byte* start, const byte* end) {
+  FunctionBody body = {module, sig, nullptr, start, end};
+  return VerifyWasmCode(body);
 }
 
-inline TreeResult BuildTFGraph(TFBuilder* builder, FunctionEnv* env,
-                               const byte* start, const byte* end) {
-  return BuildTFGraph(builder, env, nullptr, start, end);
+inline TreeResult BuildTFGraph(TFBuilder* builder, ModuleEnv* module,
+                               FunctionSig* sig, const byte* start,
+                               const byte* end) {
+  FunctionBody body = {module, sig, nullptr, start, end};
+  return BuildTFGraph(builder, body);
 }
 
 enum ReadUnsignedLEB128ErrorCode { kNoError, kInvalidLEB128, kMissingLEB128 };
@@ -267,14 +219,17 @@ enum ReadUnsignedLEB128ErrorCode { kNoError, kInvalidLEB128, kMissingLEB128 };
 ReadUnsignedLEB128ErrorCode ReadUnsignedLEB128Operand(const byte*, const byte*,
                                                       int*, uint32_t*);
 
-BitVector* AnalyzeLoopAssignmentForTesting(Zone* zone, FunctionEnv* env,
+std::vector<LocalType>* DecodeLocalDeclsForTesting(const byte* start,
+                                                   const byte* end);
+BitVector* AnalyzeLoopAssignmentForTesting(Zone* zone, size_t num_locals,
                                            const byte* start, const byte* end);
 
 // Computes the length of the opcode at the given address.
 int OpcodeLength(const byte* pc, const byte* end);
 
 // Computes the arity (number of sub-nodes) of the opcode at the given address.
-int OpcodeArity(FunctionEnv* env, const byte* pc, const byte* end);
+int OpcodeArity(ModuleEnv* module, FunctionSig* sig, const byte* pc,
+                const byte* end);
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8
diff --git a/src/wasm/decoder.h b/src/wasm/decoder.h
index f18e802f7f..0ca4e47f75 100644
--- a/src/wasm/decoder.h
+++ b/src/wasm/decoder.h
@@ -327,6 +327,7 @@ class Decoder {
 
   bool ok() const { return error_pc_ == nullptr; }
   bool failed() const { return error_pc_ != nullptr; }
+  bool more() const { return pc_ < limit_; }
 
   const byte* start() { return start_; }
   const byte* pc() { return pc_; }
diff --git a/src/wasm/encoder.cc b/src/wasm/encoder.cc
index 70d739ec67..21799eff52 100644
--- a/src/wasm/encoder.cc
+++ b/src/wasm/encoder.cc
@@ -10,6 +10,7 @@
 
 #include "src/wasm/ast-decoder.h"
 #include "src/wasm/encoder.h"
+#include "src/wasm/wasm-macro-gen.h"
 #include "src/wasm/wasm-module.h"
 #include "src/wasm/wasm-opcodes.h"
 
@@ -250,7 +251,6 @@ WasmFunctionEncoder::WasmFunctionEncoder(Zone* zone, LocalType return_type,
 
 uint32_t WasmFunctionEncoder::HeaderSize() const {
   uint32_t size = 3;
-  if (HasLocals()) size += 8;
   if (!external_) size += 2;
   if (HasName()) size += 4;
   return size;
@@ -258,7 +258,15 @@ uint32_t WasmFunctionEncoder::HeaderSize() const {
 
 
 uint32_t WasmFunctionEncoder::BodySize(void) const {
-  return external_ ? 0 : static_cast<uint32_t>(body_.size());
+  // TODO(titzer): embed a LocalDeclEncoder in the WasmFunctionEncoder
+  LocalDeclEncoder local_decl;
+  local_decl.AddLocals(local_i32_count_, kAstI32);
+  local_decl.AddLocals(local_i64_count_, kAstI64);
+  local_decl.AddLocals(local_f32_count_, kAstF32);
+  local_decl.AddLocals(local_f64_count_, kAstF64);
+
+  return external_ ? 0
+                   : static_cast<uint32_t>(body_.size() + local_decl.Size());
 }
 
 
@@ -271,7 +279,6 @@ void WasmFunctionEncoder::Serialize(byte* buffer, byte** header,
                                     byte** body) const {
   uint8_t decl_bits = (exported_ ? kDeclFunctionExport : 0) |
                       (external_ ? kDeclFunctionImport : 0) |
-                      (HasLocals() ? kDeclFunctionLocals : 0) |
                       (HasName() ? kDeclFunctionName : 0);
 
   EmitUint8(header, decl_bits);
@@ -284,15 +291,17 @@ void WasmFunctionEncoder::Serialize(byte* buffer, byte** header,
     (*body) += name_.size();
   }
 
-  if (HasLocals()) {
-    EmitUint16(header, local_i32_count_);
-    EmitUint16(header, local_i64_count_);
-    EmitUint16(header, local_f32_count_);
-    EmitUint16(header, local_f64_count_);
-  }
 
   if (!external_) {
-    EmitUint16(header, static_cast<uint16_t>(body_.size()));
+    // TODO(titzer): embed a LocalDeclEncoder in the WasmFunctionEncoder
+    LocalDeclEncoder local_decl;
+    local_decl.AddLocals(local_i32_count_, kAstI32);
+    local_decl.AddLocals(local_i64_count_, kAstI64);
+    local_decl.AddLocals(local_f32_count_, kAstF32);
+    local_decl.AddLocals(local_f64_count_, kAstF64);
+
+    EmitUint16(header, static_cast<uint16_t>(body_.size() + local_decl.Size()));
+    (*header) += local_decl.Emit(*header);
     if (body_.size() > 0) {
       std::memcpy(*header, &body_[0], body_.size());
       (*header) += body_.size();
diff --git a/src/wasm/encoder.h b/src/wasm/encoder.h
index 1afedcb9d6..c765844ae4 100644
--- a/src/wasm/encoder.h
+++ b/src/wasm/encoder.h
@@ -42,11 +42,6 @@ class WasmFunctionEncoder : public ZoneObject {
   ZoneVector<uint8_t> body_;
   ZoneVector<char> name_;
 
-  bool HasLocals() const {
-    return (local_i32_count_ + local_i64_count_ + local_f32_count_ +
-            local_f64_count_) > 0;
-  }
-
   bool HasName() const { return (exported_ || external_) && name_.size() > 0; }
 };
 
diff --git a/src/wasm/module-decoder.cc b/src/wasm/module-decoder.cc
index 01df66a2dc..401fb18239 100644
--- a/src/wasm/module-decoder.cc
+++ b/src/wasm/module-decoder.cc
@@ -338,14 +338,10 @@ class ModuleDecoder : public Decoder {
   FunctionResult DecodeSingleFunction(ModuleEnv* module_env,
                                       WasmFunction* function) {
     pc_ = start_;
-    function->sig = consume_sig();                  // read signature
+    function->sig = consume_sig();               // read signature
     function->name_offset = 0;                   // ---- name
-    function->code_start_offset = off(pc_ + 8);  // ---- code start
+    function->code_start_offset = off(pc_);      // ---- code start
     function->code_end_offset = off(limit_);     // ---- code end
-    function->local_i32_count = consume_u16();      // read u16
-    function->local_i64_count = consume_u16();      // read u16
-    function->local_f32_count = consume_u16();      // read u16
-    function->local_f64_count = consume_u16();      // read u16
     function->exported = false;                  // ---- exported
     function->external = false;                  // ---- external
 
@@ -473,18 +469,10 @@ class ModuleDecoder : public Decoder {
          << std::endl;
       os << std::endl;
     }
-    FunctionEnv fenv;
-    fenv.module = menv;
-    fenv.sig = function->sig;
-    fenv.local_i32_count = function->local_i32_count;
-    fenv.local_i64_count = function->local_i64_count;
-    fenv.local_f32_count = function->local_f32_count;
-    fenv.local_f64_count = function->local_f64_count;
-    fenv.SumLocals();
-
-    TreeResult result =
-        VerifyWasmCode(&fenv, start_, start_ + function->code_start_offset,
-                       start_ + function->code_end_offset);
+    FunctionBody body = {menv, function->sig, start_,
+                         start_ + function->code_start_offset,
+                         start_ + function->code_end_offset};
+    TreeResult result = VerifyWasmCode(body);
     if (result.failed()) {
       // Wrap the error message from the function decoder.
       std::ostringstream str;
diff --git a/src/wasm/wasm-macro-gen.h b/src/wasm/wasm-macro-gen.h
index dc7a9a1c96..85787d9f99 100644
--- a/src/wasm/wasm-macro-gen.h
+++ b/src/wasm/wasm-macro-gen.h
@@ -7,6 +7,43 @@
 
 #include "src/wasm/wasm-opcodes.h"
 
+#define U32_LE(v)                                    \
+  static_cast<byte>(v), static_cast<byte>((v) >> 8), \
+      static_cast<byte>((v) >> 16), static_cast<byte>((v) >> 24)
+
+#define U16_LE(v) static_cast<byte>(v), static_cast<byte>((v) >> 8)
+
+#define WASM_MODULE_HEADER U32_LE(kWasmMagic), U32_LE(kWasmVersion)
+
+#define SIG_INDEX(v) U16_LE(v)
+#define FUNC_INDEX(v) U16_LE(v)
+#define NAME_OFFSET(v) U32_LE(v)
+#define BR_TARGET(v) U16_LE(v)
+
+#define MASK_7 ((1 << 7) - 1)
+#define MASK_14 ((1 << 14) - 1)
+#define MASK_21 ((1 << 21) - 1)
+#define MASK_28 ((1 << 28) - 1)
+
+#define U32V_1(x) static_cast<byte>((x)&MASK_7)
+#define U32V_2(x) \
+  static_cast<byte>(((x)&MASK_7) | 0x80), static_cast<byte>(((x) >> 7) & MASK_7)
+#define U32V_3(x)                                      \
+  static_cast<byte>((((x)) & MASK_7) | 0x80),          \
+      static_cast<byte>((((x) >> 7) & MASK_7) | 0x80), \
+      static_cast<byte>(((x) >> 14) & MASK_7)
+#define U32V_4(x)                                       \
+  static_cast<byte>(((x)&MASK_7) | 0x80),               \
+      static_cast<byte>((((x) >> 7) & MASK_7) | 0x80),  \
+      static_cast<byte>((((x) >> 14) & MASK_7) | 0x80), \
+      static_cast<byte>(((x) >> 21) & MASK_7)
+#define U32V_5(x)                                       \
+  static_cast<byte>(((x)&MASK_7) | 0x80),               \
+      static_cast<byte>((((x) >> 7) & MASK_7) | 0x80),  \
+      static_cast<byte>((((x) >> 14) & MASK_7) | 0x80), \
+      static_cast<byte>((((x) >> 21) & MASK_7) | 0x80), \
+      static_cast<byte>((((x) >> 28) & MASK_7))
+
 // Convenience macros for building Wasm bytecode directly into a byte array.
 
 //------------------------------------------------------------------------------
@@ -57,6 +94,8 @@
 #define I64V_IN_RANGE(value, length) \
   ((value) >= I64V_MIN(length) && (value) <= I64V_MAX(length))
 
+#define WASM_NO_LOCALS 0
+
 namespace v8 {
 namespace internal {
 namespace wasm {
@@ -73,6 +112,83 @@ inline void CheckI64v(int64_t value, int length) {
   DCHECK(length == 1 || !I64V_IN_RANGE(value, length - 1));
 }
 
+// A helper for encoding local declarations prepended to the body of a
+// function.
+class LocalDeclEncoder {
+ public:
+  // Prepend local declarations by creating a new buffer and copying data
+  // over. The new buffer must be delete[]'d by the caller.
+  void Prepend(const byte** start, const byte** end) const {
+    size_t size = (*end - *start);
+    byte* buffer = new byte[Size() + size];
+    size_t pos = Emit(buffer);
+    memcpy(buffer + pos, *start, size);
+    pos += size;
+    *start = buffer;
+    *end = buffer + pos;
+  }
+
+  size_t Emit(byte* buffer) const {
+    size_t pos = 0;
+    pos = WriteUint32v(buffer, pos, static_cast<uint32_t>(local_decls.size()));
+    for (size_t i = 0; i < local_decls.size(); i++) {
+      pos = WriteUint32v(buffer, pos, local_decls[i].first);
+      buffer[pos++] = WasmOpcodes::LocalTypeCodeFor(local_decls[i].second);
+    }
+    DCHECK_EQ(Size(), pos);
+    return pos;
+  }
+
+  // Add locals declarations to this helper. Return the index of the newly added
+  // local(s), with an optional adjustment for the parameters.
+  uint32_t AddLocals(uint32_t count, LocalType type,
+                     FunctionSig* sig = nullptr) {
+    if (count == 0) {
+      return static_cast<uint32_t>((sig ? sig->parameter_count() : 0) +
+                                   local_decls.size());
+    }
+    size_t pos = local_decls.size();
+    if (local_decls.size() > 0 && local_decls.back().second == type) {
+      count += local_decls.back().first;
+      local_decls.pop_back();
+    }
+    local_decls.push_back(std::pair<uint32_t, LocalType>(count, type));
+    return static_cast<uint32_t>(pos + (sig ? sig->parameter_count() : 0));
+  }
+
+  size_t Size() const {
+    size_t size = SizeofUint32v(static_cast<uint32_t>(local_decls.size()));
+    for (auto p : local_decls) size += 1 + SizeofUint32v(p.first);
+    return size;
+  }
+
+ private:
+  std::vector<std::pair<uint32_t, LocalType>> local_decls;
+
+  size_t SizeofUint32v(uint32_t val) const {
+    size_t size = 1;
+    while (true) {
+      byte b = val & MASK_7;
+      if (b == val) return size;
+      size++;
+      val = val >> 7;
+    }
+  }
+
+  // TODO(titzer): lift encoding of u32v to a common place.
+  size_t WriteUint32v(byte* buffer, size_t pos, uint32_t val) const {
+    while (true) {
+      byte b = val & MASK_7;
+      if (b == val) {
+        buffer[pos++] = b;
+        break;
+      }
+      buffer[pos++] = 0x80 | b;
+      val = val >> 7;
+    }
+    return pos;
+  }
+};
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8
@@ -390,41 +506,4 @@ inline void CheckI64v(int64_t value, int length) {
 #define WASM_I32_REINTERPRET_F32(x) kExprI32ReinterpretF32, x
 #define WASM_I64_REINTERPRET_F64(x) kExprI64ReinterpretF64, x
 
-#define U32_LE(v)                                    \
-  static_cast<byte>(v), static_cast<byte>((v) >> 8), \
-      static_cast<byte>((v) >> 16), static_cast<byte>((v) >> 24)
-
-#define U16_LE(v) static_cast<byte>(v), static_cast<byte>((v) >> 8)
-
-#define WASM_MODULE_HEADER U32_LE(kWasmMagic), U32_LE(kWasmVersion)
-
-#define SIG_INDEX(v) U16_LE(v)
-#define FUNC_INDEX(v) U16_LE(v)
-#define NAME_OFFSET(v) U32_LE(v)
-#define BR_TARGET(v) U16_LE(v)
-
-#define MASK_7 ((1 << 7) - 1)
-#define MASK_14 ((1 << 14) - 1)
-#define MASK_21 ((1 << 21) - 1)
-#define MASK_28 ((1 << 28) - 1)
-
-#define U32V_1(x) static_cast<byte>(x & MASK_7)
-#define U32V_2(x) \
-  static_cast<byte>((x & MASK_7) | 0x80), static_cast<byte>((x >> 7) & MASK_7)
-#define U32V_3(x)                                    \
-  static_cast<byte>((x & MASK_7) | 0x80),            \
-      static_cast<byte>(((x >> 7) & MASK_7) | 0x80), \
-      static_cast<byte>((x >> 14) & MASK_7)
-#define U32V_4(x)                                     \
-  static_cast<byte>((x & MASK_7) | 0x80),             \
-      static_cast<byte>(((x >> 7) & MASK_7) | 0x80),  \
-      static_cast<byte>(((x >> 14) & MASK_7) | 0x80), \
-      static_cast<byte>((x >> 21) & MASK_7)
-#define U32V_5(x)                                     \
-  static_cast<byte>((x & MASK_7) | 0x80),             \
-      static_cast<byte>(((x >> 7) & MASK_7) | 0x80),  \
-      static_cast<byte>(((x >> 14) & MASK_7) | 0x80), \
-      static_cast<byte>(((x >> 21) & MASK_7) | 0x80), \
-      static_cast<byte>(((x >> 28) & MASK_7))
-
 #endif  // V8_WASM_MACRO_GEN_H_
diff --git a/src/wasm/wasm-opcodes.h b/src/wasm/wasm-opcodes.h
index 106572ce99..fdca737080 100644
--- a/src/wasm/wasm-opcodes.h
+++ b/src/wasm/wasm-opcodes.h
@@ -97,7 +97,8 @@ std::ostream& operator<<(std::ostream& os, const FunctionSig& function);
   V(StoreGlobal, 0x11, _)      \
   V(CallFunction, 0x12, _)     \
   V(CallIndirect, 0x13, _)     \
-  V(CallImport, 0x1F, _)
+  V(CallImport, 0x1F, _)       \
+  V(DeclLocals, 0x1E, _)
 
 // Load memory expressions.
 #define FOREACH_LOAD_MEM_OPCODE(V) \
diff --git a/test/cctest/wasm/test-run-wasm-64.cc b/test/cctest/wasm/test-run-wasm-64.cc
index 7f48012318..2bcd538f5f 100644
--- a/test/cctest/wasm/test-run-wasm-64.cc
+++ b/test/cctest/wasm/test-run-wasm-64.cc
@@ -206,8 +206,7 @@ TEST(Run_WasmCallI64Parameter) {
     uint32_t index = t.CompileAndAdd();
 
     // Build the calling function.
-    WasmRunner<int32_t> r;
-    r.env()->module = &module;
+    WasmRunner<int32_t> r(&module);
     BUILD(
         r,
         WASM_I32_CONVERT_I64(WASM_CALL_FUNCTION(
diff --git a/test/cctest/wasm/test-run-wasm-module.cc b/test/cctest/wasm/test-run-wasm-module.cc
index dd78e99748..79406165a6 100644
--- a/test/cctest/wasm/test-run-wasm-module.cc
+++ b/test/cctest/wasm/test-run-wasm-module.cc
@@ -42,14 +42,16 @@ TEST(Run_WasmModule_CallAdd_rev) {
       2, kLocalI32, kLocalI32, kLocalI32,  // int,int -> int
       // func#0 (main) ----------------------------------
       kDeclFunctions, 2, kDeclFunctionExport, 0, 0,  // sig index
-      6, 0,                                          // body size
+      7, 0,                                          // body size
+      0,                                             // locals
       kExprCallFunction, 1,                          // --
       kExprI8Const, 77,                              // --
       kExprI8Const, 22,                              // --
       // func#1 -----------------------------------------
       0,                 // no name, not exported
       1, 0,              // sig index
-      5, 0,              // body size
+      6, 0,              // body size
+      0,                 // locals
       kExprI32Add,       // --
       kExprGetLocal, 0,  // --
       kExprGetLocal, 1,  // --
diff --git a/test/cctest/wasm/test-run-wasm.cc b/test/cctest/wasm/test-run-wasm.cc
index b94e51dd0f..74247e483a 100644
--- a/test/cctest/wasm/test-run-wasm.cc
+++ b/test/cctest/wasm/test-run-wasm.cc
@@ -973,7 +973,8 @@ TEST(Run_Wasm_Select_strict1) {
 
 TEST(Run_Wasm_Select_strict2) {
   WasmRunner<int32_t> r(MachineType::Int32());
-  r.env()->AddLocals(kAstI32, 2);
+  r.AllocateLocal(kAstI32);
+  r.AllocateLocal(kAstI32);
   // select(b=5, c=6, a)
   BUILD(r, WASM_SELECT(WASM_SET_LOCAL(1, WASM_I8(5)),
                        WASM_SET_LOCAL(2, WASM_I8(6)), WASM_GET_LOCAL(0)));
@@ -985,7 +986,8 @@ TEST(Run_Wasm_Select_strict2) {
 
 TEST(Run_Wasm_Select_strict3) {
   WasmRunner<int32_t> r(MachineType::Int32());
-  r.env()->AddLocals(kAstI32, 2);
+  r.AllocateLocal(kAstI32);
+  r.AllocateLocal(kAstI32);
   // select(b=5, c=6, a=b)
   BUILD(r, WASM_SELECT(WASM_SET_LOCAL(1, WASM_I8(5)),
                        WASM_SET_LOCAL(2, WASM_I8(6)),
@@ -1232,8 +1234,7 @@ TEST(Run_Wasm_VoidReturn1) {
 
   const int32_t kExpected = -414444;
   // Build the calling function.
-  WasmRunner<int32_t> r;
-  r.env()->module = &module;
+  WasmRunner<int32_t> r(&module);
   BUILD(r, B2(WASM_CALL_FUNCTION0(index), WASM_I32V_3(kExpected)));
 
   int32_t result = r.Call();
@@ -1252,8 +1253,7 @@ TEST(Run_Wasm_VoidReturn2) {
 
   const int32_t kExpected = -414444;
   // Build the calling function.
-  WasmRunner<int32_t> r;
-  r.env()->module = &module;
+  WasmRunner<int32_t> r(&module);
   BUILD(r, B2(WASM_CALL_FUNCTION0(index), WASM_I32V_3(kExpected)));
 
   int32_t result = r.Call();
@@ -2006,18 +2006,19 @@ static void TestBuildGraphForSimpleExpression(WasmOpcode opcode) {
                                  MachineOperatorBuilder::kAllOptionalOps);
   Graph graph(&zone);
   JSGraph jsgraph(isolate, &graph, &common, nullptr, nullptr, &machine);
-  FunctionEnv env;
   FunctionSig* sig = WasmOpcodes::Signature(opcode);
-  init_env(&env, sig);
 
   if (sig->parameter_count() == 1) {
-    byte code[] = {static_cast<byte>(opcode), kExprGetLocal, 0};
-    TestBuildingGraph(&zone, &jsgraph, &env, code, code + arraysize(code));
+    byte code[] = {WASM_NO_LOCALS, static_cast<byte>(opcode), kExprGetLocal, 0};
+    TestBuildingGraph(&zone, &jsgraph, nullptr, sig, code,
+                      code + arraysize(code));
   } else {
     CHECK_EQ(2, sig->parameter_count());
-    byte code[] = {static_cast<byte>(opcode), kExprGetLocal, 0, kExprGetLocal,
-                   1};
-    TestBuildingGraph(&zone, &jsgraph, &env, code, code + arraysize(code));
+    byte code[] = {WASM_NO_LOCALS, static_cast<byte>(opcode),
+                   kExprGetLocal,  0,
+                   kExprGetLocal,  1};
+    TestBuildingGraph(&zone, &jsgraph, nullptr, sig, code,
+                      code + arraysize(code));
   }
 }
 
diff --git a/test/cctest/wasm/wasm-run-utils.h b/test/cctest/wasm/wasm-run-utils.h
index 77e15a4374..614f0fe10c 100644
--- a/test/cctest/wasm/wasm-run-utils.h
+++ b/test/cctest/wasm/wasm-run-utils.h
@@ -63,16 +63,6 @@ using namespace v8::internal;
 using namespace v8::internal::compiler;
 using namespace v8::internal::wasm;
 
-inline void init_env(FunctionEnv* env, FunctionSig* sig) {
-  env->module = nullptr;
-  env->sig = sig;
-  env->local_i32_count = 0;
-  env->local_i64_count = 0;
-  env->local_f32_count = 0;
-  env->local_f64_count = 0;
-  env->SumLocals();
-}
-
 const uint32_t kMaxGlobalsSize = 128;
 
 // A helper for module environments that adds the ability to allocate memory
@@ -227,11 +217,11 @@ class TestingModule : public ModuleEnv {
   }
 };
 
-
-inline void TestBuildingGraph(Zone* zone, JSGraph* jsgraph, FunctionEnv* env,
-                              const byte* start, const byte* end) {
-  compiler::WasmGraphBuilder builder(zone, jsgraph, env->sig);
-  TreeResult result = BuildTFGraph(&builder, env, start, end);
+inline void TestBuildingGraph(Zone* zone, JSGraph* jsgraph, ModuleEnv* module,
+                              FunctionSig* sig, const byte* start,
+                              const byte* end) {
+  compiler::WasmGraphBuilder builder(zone, jsgraph, sig);
+  TreeResult result = BuildTFGraph(&builder, module, sig, start, end);
   if (result.failed()) {
     ptrdiff_t pc = result.error_pc - result.start;
     ptrdiff_t pt = result.error_pt - result.start;
@@ -399,10 +389,9 @@ class WasmFunctionCompiler : public HandleAndZoneScope,
       : GraphAndBuilders(main_zone()),
         jsgraph(this->isolate(), this->graph(), this->common(), nullptr,
                 nullptr, this->machine()),
+        sig(sig),
         descriptor_(nullptr),
         testing_module_(module) {
-    init_env(&env, sig);
-    env.module = module;
     if (module) {
       // Get a new function from the testing module.
       function_ = nullptr;
@@ -420,12 +409,13 @@ class WasmFunctionCompiler : public HandleAndZoneScope,
   }
 
   JSGraph jsgraph;
-  FunctionEnv env;
+  FunctionSig* sig;
   // The call descriptor is initialized when the function is compiled.
   CallDescriptor* descriptor_;
   TestingModule* testing_module_;
   WasmFunction* function_;
   int function_index_;
+  LocalDeclEncoder local_decls;
 
   Isolate* isolate() { return main_isolate(); }
   Graph* graph() const { return main_graph_; }
@@ -434,28 +424,23 @@ class WasmFunctionCompiler : public HandleAndZoneScope,
   MachineOperatorBuilder* machine() { return &main_machine_; }
   void InitializeDescriptor() {
     if (descriptor_ == nullptr) {
-      descriptor_ = env.module->GetWasmCallDescriptor(main_zone(), env.sig);
+      descriptor_ = testing_module_->GetWasmCallDescriptor(main_zone(), sig);
     }
   }
   CallDescriptor* descriptor() { return descriptor_; }
 
   void Build(const byte* start, const byte* end) {
-    // Transfer local counts before compiling.
-    function()->local_i32_count = env.local_i32_count;
-    function()->local_i64_count = env.local_i64_count;
-    function()->local_f32_count = env.local_f32_count;
-    function()->local_f64_count = env.local_f64_count;
-
     // Build the TurboFan graph.
-    TestBuildingGraph(main_zone(), &jsgraph, &env, start, end);
+    local_decls.Prepend(&start, &end);
+    TestBuildingGraph(main_zone(), &jsgraph, testing_module_, sig, start, end);
+    delete[] start;
   }
 
   byte AllocateLocal(LocalType type) {
-    int result = static_cast<int>(env.total_locals);
-    env.AddLocals(type, 1);
-    byte b = static_cast<byte>(result);
-    CHECK_EQ(result, b);
-    return b;
+    uint32_t index = local_decls.AddLocals(1, type, sig);
+    byte result = static_cast<byte>(index);
+    DCHECK_EQ(index, result);
+    return result;
   }
 
   // TODO(titzer): remove me.
@@ -542,8 +527,6 @@ class WasmRunner {
     wrapper_.Init(compiler_.descriptor(), p0, p1, p2, p3);
   }
 
-  FunctionEnv* env() { return &compiler_.env; }
-
   // Builds a graph from the given Wasm code and generates the machine
   // code and call wrapper for that graph. This method must not be called
   // more than once.
@@ -593,13 +576,7 @@ class WasmRunner {
     return return_value;
   }
 
-  byte AllocateLocal(LocalType type) {
-    int result = static_cast<int>(env()->total_locals);
-    env()->AddLocals(type, 1);
-    byte b = static_cast<byte>(result);
-    CHECK_EQ(result, b);
-    return b;
-  }
+  byte AllocateLocal(LocalType type) { return compiler_.AllocateLocal(type); }
 
  protected:
   Zone zone;
diff --git a/test/mjsunit/wasm/test-wasm-module-builder.js b/test/mjsunit/wasm/test-wasm-module-builder.js
index 7c287efa4f..3063553303 100644
--- a/test/mjsunit/wasm/test-wasm-module-builder.js
+++ b/test/mjsunit/wasm/test-wasm-module-builder.js
@@ -47,6 +47,29 @@ var debug = false;
     assertEquals(27777, instance.exports.main(27777));
 })();
 
+(function LocalsTest2() {
+    // TODO(titzer): i64 only works on 64-bit platforms.
+    var types = [
+      {locals: {i32_count: 1}, type: kAstI32},
+//      {locals: {i64_count: 1}, type: kAstI64},
+      {locals: {f32_count: 1}, type: kAstF32},
+      {locals: {f64_count: 1}, type: kAstF64},
+    ];
+
+    for (p of types) {
+      var module = new WasmModuleBuilder();
+      module.addFunction(undefined, [p.type, p.type])
+        .addLocals(p.locals)
+        .addBody([kExprSetLocal, 1, kExprGetLocal, 0])
+        .exportAs("main");
+
+      var buffer = module.toBuffer(debug);
+      var instance = _WASMEXP_.instantiateModule(buffer);
+      assertEquals(19, instance.exports.main(19));
+      assertEquals(27777, instance.exports.main(27777));
+    }
+})();
+
 (function CallTest() {
     var module = new WasmModuleBuilder();
     module.addFunction("add", [kAstI32, kAstI32, kAstI32])
diff --git a/test/mjsunit/wasm/verify-function-simple.js b/test/mjsunit/wasm/verify-function-simple.js
index c4d51c7423..ef87d0e136 100644
--- a/test/mjsunit/wasm/verify-function-simple.js
+++ b/test/mjsunit/wasm/verify-function-simple.js
@@ -9,10 +9,7 @@ load("test/mjsunit/wasm/wasm-constants.js");
 try {
   var data = bytes(
       0,       kAstStmt,  // signature
-      3,       0,         // local int32 count
-      4,       0,         // local int64 count
-      5,       0,         // local float32 count
-      6,       0,         // local float64 count
+      kDeclNoLocals,      // --
       kExprNop            // body
   );
 
@@ -27,10 +24,7 @@ var threw = false;
 try {
   var data = bytes(
       0,       kAstI32,   // signature
-      2,       0,         // local int32 count
-      3,       0,         // local int64 count
-      4,       0,         // local float32 count
-      5,       0,         // local float64 count
+      kDeclNoLocals,      // --
       kExprBlock, 2, kExprNop, kExprNop  // body
   );
 
diff --git a/test/mjsunit/wasm/wasm-constants.js b/test/mjsunit/wasm/wasm-constants.js
index 17431bc543..d0d5aed84e 100644
--- a/test/mjsunit/wasm/wasm-constants.js
+++ b/test/mjsunit/wasm/wasm-constants.js
@@ -48,6 +48,8 @@ function bytesWithHeader() {
   return buffer;
 }
 
+var kDeclNoLocals = 0;
+
 // Section declaration constants
 var kDeclMemory = 0x00;
 var kDeclSignatures = 0x01;
diff --git a/test/mjsunit/wasm/wasm-module-builder.js b/test/mjsunit/wasm/wasm-module-builder.js
index e51d4425fd..dd15001891 100644
--- a/test/mjsunit/wasm/wasm-module-builder.js
+++ b/test/mjsunit/wasm/wasm-module-builder.js
@@ -190,25 +190,46 @@ WasmModuleBuilder.prototype.toArray = function(debug) {
             var hasName = func.name != undefined && func.name.length > 0;
             names = names || hasName;
             if (hasName) flags |= kDeclFunctionName;
-            if (func.locals != undefined) flags |= kDeclFunctionLocals;
             exports += func.exports.length;
 
             emit_u8(bytes, flags);
             emit_u16(bytes, func.sig_index);
 
-            if (hasName) {
-                emit_string(bytes, func.name);
+            if (hasName) emit_string(bytes, func.name);
+
+            // Function body length will be patched later.
+            var length_pos = bytes.length;
+            emit_u16(bytes, 0);
+
+            var local_decls = [];
+            var l = func.locals;
+            if (l != undefined) {
+              var local_decls_count = 0;
+              if (l.i32_count > 0) {
+                local_decls.push({count: l.i32_count, type: kAstI32});
+              }
+              if (l.i64_count > 0) {
+                local_decls.push({count: l.i64_count, type: kAstI64});
+              }
+              if (l.f32_count > 0) {
+                local_decls.push({count: l.f32_count, type: kAstF32});
+              }
+              if (l.f64_count > 0) {
+                local_decls.push({count: l.f64_count, type: kAstF64});
+              }
             }
-            if (func.locals != undefined) {
-                emit_u16(bytes, func.locals.i32_count);
-                emit_u16(bytes, func.locals.i64_count);
-                emit_u16(bytes, func.locals.f32_count);
-                emit_u16(bytes, func.locals.f64_count);
+            emit_u8(bytes, local_decls.length);
+            for (decl of local_decls) {
+              emit_varint(bytes, decl.count);
+              emit_u8(bytes, decl.type);
             }
-            emit_u16(bytes, func.body.length);
+
             for (var i = 0; i < func.body.length; i++) {
                 emit_u8(bytes, func.body[i]);
             }
+            var length = bytes.length - length_pos - 2;
+            bytes[length_pos] = length & 0xff;
+            bytes[length_pos + 1] = (length >> 8) & 0xff;
 
             index++;
         }
diff --git a/test/unittests/wasm/ast-decoder-unittest.cc b/test/unittests/wasm/ast-decoder-unittest.cc
index e491179c8c..95a791b9a6 100644
--- a/test/unittests/wasm/ast-decoder-unittest.cc
+++ b/test/unittests/wasm/ast-decoder-unittest.cc
@@ -55,50 +55,33 @@ static const WasmOpcode kInt32BinopOpcodes[] = {
     Verify(kError, env, code, code + arraysize(code)); \
   } while (false)
 
-#define VERIFY(...)                                        \
-  do {                                                     \
-    static const byte code[] = {__VA_ARGS__};              \
-    Verify(kSuccess, &env_v_i, code, code + sizeof(code)); \
+#define VERIFY(...)                                          \
+  do {                                                       \
+    static const byte code[] = {__VA_ARGS__};                \
+    Verify(kSuccess, sigs.v_i(), code, code + sizeof(code)); \
   } while (false)
 
 class AstDecoderTest : public TestWithZone {
  public:
-  AstDecoderTest() : TestWithZone(), sigs() {
-    init_env(&env_i_i, sigs.i_i());
-    init_env(&env_v_v, sigs.v_v());
-    init_env(&env_v_i, sigs.v_i());
-    init_env(&env_i_f, sigs.i_f());
-    init_env(&env_i_d, sigs.i_d());
-    init_env(&env_l_l, sigs.l_l());
-    init_env(&env_f_ff, sigs.f_ff());
-    init_env(&env_d_dd, sigs.d_dd());
-  }
+  typedef std::pair<uint32_t, LocalType> LocalsDecl;
 
+  AstDecoderTest() : module(nullptr) {}
   TestSignatures sigs;
+  ModuleEnv* module;
+  LocalDeclEncoder local_decls;
 
-  FunctionEnv env_i_i;
-  FunctionEnv env_v_v;
-  FunctionEnv env_v_i;
-  FunctionEnv env_i_f;
-  FunctionEnv env_i_d;
-  FunctionEnv env_l_l;
-  FunctionEnv env_f_ff;
-  FunctionEnv env_d_dd;
-
-  static void init_env(FunctionEnv* env, FunctionSig* sig) {
-    env->module = nullptr;
-    env->sig = sig;
-    env->local_i32_count = 0;
-    env->local_i64_count = 0;
-    env->local_f32_count = 0;
-    env->local_f64_count = 0;
-    env->SumLocals();
+  void AddLocals(LocalType type, uint32_t count) {
+    local_decls.AddLocals(count, type);
   }
 
-  // A wrapper around VerifyWasmCode() that renders a nice failure message.
-  void Verify(ErrorCode expected, FunctionEnv* env, const byte* start,
+  // Preprends local variable declarations and renders nice error messages for
+  // verification failures.
+  void Verify(ErrorCode expected, FunctionSig* sig, const byte* start,
               const byte* end) {
-    TreeResult result = VerifyWasmCode(env, start, end);
+    local_decls.Prepend(&start, &end);
+    // Verify the code.
+    TreeResult result = VerifyWasmCode(module, sig, start, end);
+
     if (result.error_code != expected) {
       ptrdiff_t pc = result.error_pc - result.start;
       ptrdiff_t pt = result.error_pt - result.start;
@@ -117,15 +100,15 @@ class AstDecoderTest : public TestWithZone {
       }
       FATAL(str.str().c_str());
     }
+
+    delete[] start;  // local_decls.Prepend() allocated a new buffer.
   }
 
   void TestBinop(WasmOpcode opcode, FunctionSig* success) {
     // op(local[0], local[1])
     byte code[] = {static_cast<byte>(opcode), kExprGetLocal, 0, kExprGetLocal,
                    1};
-    FunctionEnv env;
-    init_env(&env, success);
-    EXPECT_VERIFIES(&env, code);
+    EXPECT_VERIFIES(success, code);
 
     // Try all combinations of return and parameter types.
     for (size_t i = 0; i < arraysize(kLocalTypes); i++) {
@@ -137,8 +120,7 @@ class AstDecoderTest : public TestWithZone {
               types[2] != success->GetParam(1)) {
             // Test signature mismatch.
             FunctionSig sig(1, 2, types);
-            init_env(&env, &sig);
-            EXPECT_FAILURE(&env, code);
+            EXPECT_FAILURE(&sig, code);
           }
         }
       }
@@ -152,12 +134,10 @@ class AstDecoderTest : public TestWithZone {
   void TestUnop(WasmOpcode opcode, LocalType ret_type, LocalType param_type) {
     // Return(op(local[0]))
     byte code[] = {static_cast<byte>(opcode), kExprGetLocal, 0};
-    FunctionEnv env;
     {
       LocalType types[] = {ret_type, param_type};
       FunctionSig sig(1, 1, types);
-      init_env(&env, &sig);
-      EXPECT_VERIFIES(&env, code);
+      EXPECT_VERIFIES(&sig, code);
     }
 
     // Try all combinations of return and parameter types.
@@ -167,8 +147,7 @@ class AstDecoderTest : public TestWithZone {
         if (types[0] != ret_type || types[1] != param_type) {
           // Test signature mismatch.
           FunctionSig sig(1, 1, types);
-          init_env(&env, &sig);
-          EXPECT_FAILURE(&env, code);
+          EXPECT_FAILURE(&sig, code);
         }
       }
     }
@@ -176,46 +155,35 @@ class AstDecoderTest : public TestWithZone {
 };
 
 
-static FunctionEnv CreateInt32FunctionEnv(FunctionSig* sig, int count) {
-  FunctionEnv env;
-  env.module = nullptr;
-  env.sig = sig;
-  env.local_i32_count = count;
-  env.local_f64_count = 0;
-  env.local_f32_count = 0;
-  env.total_locals = static_cast<unsigned>(count + sig->parameter_count());
-  return env;
-}
-
 TEST_F(AstDecoderTest, Int8Const) {
   byte code[] = {kExprI8Const, 0};
   for (int i = -128; i < 128; i++) {
     code[1] = static_cast<byte>(i);
-    EXPECT_VERIFIES(&env_i_i, code);
+    EXPECT_VERIFIES(sigs.i_i(), code);
   }
 }
 
 TEST_F(AstDecoderTest, EmptyFunction) {
   byte code[] = {0};
-  Verify(kSuccess, &env_v_v, code, code);
-  Verify(kError, &env_i_i, code, code);
+  Verify(kSuccess, sigs.v_v(), code, code);
+  Verify(kError, sigs.i_i(), code, code);
 }
 
 TEST_F(AstDecoderTest, IncompleteIf1) {
   byte code[] = {kExprIf};
-  EXPECT_FAILURE(&env_v_v, code);
-  EXPECT_FAILURE(&env_i_i, code);
+  EXPECT_FAILURE(sigs.v_v(), code);
+  EXPECT_FAILURE(sigs.i_i(), code);
 }
 
 TEST_F(AstDecoderTest, IncompleteIf2) {
   byte code[] = {kExprIf, kExprI8Const, 0};
-  EXPECT_FAILURE(&env_v_v, code);
-  EXPECT_FAILURE(&env_i_i, code);
+  EXPECT_FAILURE(sigs.v_v(), code);
+  EXPECT_FAILURE(sigs.i_i(), code);
 }
 
 TEST_F(AstDecoderTest, Int8Const_fallthru) {
   byte code[] = {kExprI8Const, 0, kExprI8Const, 1};
-  EXPECT_VERIFIES(&env_i_i, code);
+  EXPECT_VERIFIES(sigs.i_i(), code);
 }
 
 TEST_F(AstDecoderTest, Int32Const) {
@@ -223,20 +191,20 @@ TEST_F(AstDecoderTest, Int32Const) {
   for (int32_t i = kMinInt; i < kMaxInt - kInc; i = i + kInc) {
     // TODO(binji): expand test for other sized int32s; 1 through 5 bytes.
     byte code[] = {WASM_I32V(i)};
-    EXPECT_VERIFIES(&env_i_i, code);
+    EXPECT_VERIFIES(sigs.i_i(), code);
   }
 }
 
 TEST_F(AstDecoderTest, Int8Const_fallthru2) {
   byte code[] = {WASM_I8(0), WASM_I32V_4(0x1122334)};
-  EXPECT_VERIFIES(&env_i_i, code);
+  EXPECT_VERIFIES(sigs.i_i(), code);
 }
 
 TEST_F(AstDecoderTest, Int64Const) {
   const int kInc = 4498211;
   for (int32_t i = kMinInt; i < kMaxInt - kInc; i = i + kInc) {
     byte code[] = {WASM_I64V((static_cast<int64_t>(i) << 32) | i)};
-    EXPECT_VERIFIES(&env_l_l, code);
+    EXPECT_VERIFIES(sigs.l_l(), code);
   }
 }
 
@@ -245,7 +213,7 @@ TEST_F(AstDecoderTest, Float32Const) {
   float* ptr = reinterpret_cast<float*>(code + 1);
   for (int i = 0; i < 30; i++) {
     *ptr = i * -7.75f;
-    EXPECT_VERIFIES(&env_f_ff, code);
+    EXPECT_VERIFIES(sigs.f_ff(), code);
   }
 }
 
@@ -254,7 +222,7 @@ TEST_F(AstDecoderTest, Float64Const) {
   double* ptr = reinterpret_cast<double*>(code + 1);
   for (int i = 0; i < 30; i++) {
     *ptr = i * 33.45;
-    EXPECT_VERIFIES(&env_d_dd, code);
+    EXPECT_VERIFIES(sigs.d_dd(), code);
   }
 }
 
@@ -262,102 +230,89 @@ TEST_F(AstDecoderTest, Int32Const_off_end) {
   byte code[] = {kExprI32Const, 0xaa, 0xbb, 0xcc, 0x44};
 
   for (int size = 1; size <= 4; size++) {
-    Verify(kError, &env_i_i, code, code + size);
+    Verify(kError, sigs.i_i(), code, code + size);
   }
 }
 
 TEST_F(AstDecoderTest, GetLocal0_param) {
-  EXPECT_VERIFIES(&env_i_i, kCodeGetLocal0);
+  EXPECT_VERIFIES(sigs.i_i(), kCodeGetLocal0);
 }
 
 TEST_F(AstDecoderTest, GetLocal0_local) {
-  FunctionEnv env;
-  init_env(&env, sigs.i_v());
-  env.AddLocals(kAstI32, 1);
-  EXPECT_VERIFIES(&env, kCodeGetLocal0);
+  AddLocals(kAstI32, 1);
+  EXPECT_VERIFIES(sigs.i_v(), kCodeGetLocal0);
 }
 
 TEST_F(AstDecoderTest, GetLocal0_param_n) {
   FunctionSig* array[] = {sigs.i_i(), sigs.i_ii(), sigs.i_iii()};
 
   for (size_t i = 0; i < arraysize(array); i++) {
-    FunctionEnv env = CreateInt32FunctionEnv(array[i], 0);
-    EXPECT_VERIFIES(&env, kCodeGetLocal0);
+    EXPECT_VERIFIES(array[i], kCodeGetLocal0);
   }
 }
 
 TEST_F(AstDecoderTest, GetLocalN_local) {
   for (byte i = 1; i < 8; i++) {
-    FunctionEnv env = CreateInt32FunctionEnv(sigs.i_v(), i);
+    AddLocals(kAstI32, 1);
     for (byte j = 0; j < i; j++) {
       byte code[] = {kExprGetLocal, j};
-      EXPECT_VERIFIES(&env, code);
+      EXPECT_VERIFIES(sigs.i_v(), code);
     }
   }
 }
 
 TEST_F(AstDecoderTest, GetLocal0_fail_no_params) {
-  FunctionEnv env = CreateInt32FunctionEnv(sigs.i_v(), 0);
-
-  EXPECT_FAILURE(&env, kCodeGetLocal0);
+  EXPECT_FAILURE(sigs.i_v(), kCodeGetLocal0);
 }
 
 TEST_F(AstDecoderTest, GetLocal1_fail_no_locals) {
-  EXPECT_FAILURE(&env_i_i, kCodeGetLocal1);
+  EXPECT_FAILURE(sigs.i_i(), kCodeGetLocal1);
 }
 
 TEST_F(AstDecoderTest, GetLocal_off_end) {
   static const byte code[] = {kExprGetLocal};
-  EXPECT_FAILURE(&env_i_i, code);
+  EXPECT_FAILURE(sigs.i_i(), code);
 }
 
 TEST_F(AstDecoderTest, GetLocal_varint) {
-  env_i_i.local_i32_count = 1000000000;
-  env_i_i.total_locals += 1000000000;
+  const int kMaxLocals = 8000000;
+  AddLocals(kAstI32, kMaxLocals);
 
-  {
-    static const byte code[] = {kExprGetLocal, 0xFF, 0x01};
-    EXPECT_VERIFIES(&env_i_i, code);
-    EXPECT_FAILURE(&env_i_f, code);
+  for (int index = 0; index < kMaxLocals; index = index * 11 + 5) {
+    EXPECT_VERIFIES_INLINE(sigs.i_i(), kExprGetLocal, U32V_1(index));
+    EXPECT_VERIFIES_INLINE(sigs.i_i(), kExprGetLocal, U32V_2(index));
+    EXPECT_VERIFIES_INLINE(sigs.i_i(), kExprGetLocal, U32V_3(index));
+    EXPECT_VERIFIES_INLINE(sigs.i_i(), kExprGetLocal, U32V_4(index));
   }
 
-  {
-    static const byte code[] = {kExprGetLocal, 0xF0, 0x80, 0x01};
-    EXPECT_VERIFIES(&env_i_i, code);
-    EXPECT_FAILURE(&env_i_f, code);
-  }
+  EXPECT_VERIFIES_INLINE(sigs.i_i(), kExprGetLocal, U32V_5(kMaxLocals - 1));
 
-  {
-    static const byte code[] = {kExprGetLocal, 0xF2, 0x81, 0x82, 0x01};
-    EXPECT_VERIFIES(&env_i_i, code);
-    EXPECT_FAILURE(&env_i_f, code);
-  }
+  EXPECT_VERIFIES_INLINE(sigs.i_i(), kExprGetLocal, U32V_4(kMaxLocals - 1));
+  EXPECT_VERIFIES_INLINE(sigs.i_i(), kExprGetLocal, U32V_4(kMaxLocals));
+  EXPECT_FAILURE_INLINE(sigs.i_i(), kExprGetLocal, U32V_4(kMaxLocals + 1));
 
-  {
-    static const byte code[] = {kExprGetLocal, 0xF3, 0xA1, 0xB1, 0xC1, 0x01};
-    EXPECT_VERIFIES(&env_i_i, code);
-    EXPECT_FAILURE(&env_i_f, code);
-  }
+  EXPECT_FAILURE_INLINE(sigs.i_v(), kExprGetLocal, U32V_4(kMaxLocals));
+  EXPECT_FAILURE_INLINE(sigs.i_v(), kExprGetLocal, U32V_4(kMaxLocals + 1));
 }
 
 TEST_F(AstDecoderTest, Binops_off_end) {
   byte code1[] = {0};  // [opcode]
   for (size_t i = 0; i < arraysize(kInt32BinopOpcodes); i++) {
     code1[0] = kInt32BinopOpcodes[i];
-    EXPECT_FAILURE(&env_i_i, code1);
+    EXPECT_FAILURE(sigs.i_i(), code1);
   }
 
   byte code3[] = {0, kExprGetLocal, 0};  // [opcode] [expr]
   for (size_t i = 0; i < arraysize(kInt32BinopOpcodes); i++) {
     code3[0] = kInt32BinopOpcodes[i];
-    EXPECT_FAILURE(&env_i_i, code3);
+    EXPECT_FAILURE(sigs.i_i(), code3);
   }
 
   byte code4[] = {0, kExprGetLocal, 0, 0};  // [opcode] [expr] [opcode]
   for (size_t i = 0; i < arraysize(kInt32BinopOpcodes); i++) {
     code4[0] = kInt32BinopOpcodes[i];
     code4[3] = kInt32BinopOpcodes[i];
-    EXPECT_FAILURE(&env_i_i, code4);
+    EXPECT_FAILURE(sigs.i_i(), code4);
   }
 }
 
@@ -367,56 +322,55 @@ TEST_F(AstDecoderTest, Binops_off_end) {
 //===================================================================
 TEST_F(AstDecoderTest, Nop) {
   static const byte code[] = {kExprNop};
-  EXPECT_VERIFIES(&env_v_v, code);
+  EXPECT_VERIFIES(sigs.v_v(), code);
 }
 
 TEST_F(AstDecoderTest, SetLocal0_param) {
   static const byte code[] = {kExprSetLocal, 0, kExprI8Const, 0};
-  EXPECT_VERIFIES(&env_i_i, code);
+  EXPECT_VERIFIES(sigs.i_i(), code);
 }
 
 TEST_F(AstDecoderTest, SetLocal0_local) {
   byte code[] = {kExprSetLocal, 0, kExprI8Const, 0};
-  FunctionEnv env = CreateInt32FunctionEnv(sigs.i_v(), 1);
-
-  EXPECT_VERIFIES(&env, code);
+  AddLocals(kAstI32, 1);
+  EXPECT_VERIFIES(sigs.i_v(), code);
 }
 
 TEST_F(AstDecoderTest, SetLocalN_local) {
   for (byte i = 1; i < 8; i++) {
-    FunctionEnv env = CreateInt32FunctionEnv(sigs.i_v(), i);
+    AddLocals(kAstI32, 1);
     for (byte j = 0; j < i; j++) {
       byte code[] = {kExprSetLocal, j, kExprI8Const, i};
-      EXPECT_VERIFIES(&env, code);
+      EXPECT_VERIFIES(sigs.v_v(), code);
     }
   }
 }
 
 TEST_F(AstDecoderTest, Block0) {
   static const byte code[] = {kExprBlock, 0};
-  EXPECT_VERIFIES(&env_v_v, code);
+  EXPECT_VERIFIES(sigs.v_v(), code);
 }
 
 TEST_F(AstDecoderTest, Block0_fallthru1) {
   static const byte code[] = {kExprBlock, 0, kExprBlock, 0};
-  EXPECT_VERIFIES(&env_v_v, code);
+  EXPECT_VERIFIES(sigs.v_v(), code);
 }
 
 TEST_F(AstDecoderTest, Block1) {
   static const byte code[] = {kExprBlock, 1, kExprSetLocal, 0, kExprI8Const, 0};
-  EXPECT_VERIFIES(&env_i_i, code);
+  EXPECT_VERIFIES(sigs.i_i(), code);
 }
 
 TEST_F(AstDecoderTest, Block0_fallthru2) {
   static const byte code[] = {kExprBlock, 0, kExprSetLocal, 0, kExprI8Const, 0};
-  EXPECT_VERIFIES(&env_i_i, code);
+  EXPECT_VERIFIES(sigs.i_i(), code);
 }
 
 TEST_F(AstDecoderTest, Block2) {
   static const byte code[] = {kExprBlock,    2,                    // --
                               kExprSetLocal, 0, kExprI8Const, 0,   // --
                               kExprSetLocal, 0, kExprI8Const, 0};  // --
-  EXPECT_VERIFIES(&env_i_i, code);
+  EXPECT_VERIFIES(sigs.i_i(), code);
 }
 
 TEST_F(AstDecoderTest, Block2_fallthru) {
@@ -424,7 +378,7 @@ TEST_F(AstDecoderTest, Block2_fallthru) {
                               kExprSetLocal, 0, kExprI8Const, 0,  // --
                               kExprSetLocal, 0, kExprI8Const, 0,  // --
                               kExprI8Const,  11};                 // --
-  EXPECT_VERIFIES(&env_i_i, code);
+  EXPECT_VERIFIES(sigs.i_i(), code);
 }
 
 TEST_F(AstDecoderTest, BlockN) {
@@ -439,7 +393,7 @@ TEST_F(AstDecoderTest, BlockN) {
       memcpy(code + sizeof(block) + j * sizeof(kCodeSetLocal0), kCodeSetLocal0,
              sizeof(kCodeSetLocal0));
     }
-    Verify(kSuccess, &env_v_i, code, code + total);
+    Verify(kSuccess, sigs.v_i(), code, code + total);
     free(code);
   }
 }
@@ -447,66 +401,66 @@ TEST_F(AstDecoderTest, BlockN) {
 TEST_F(AstDecoderTest, BlockN_off_end) {
   for (byte i = 2; i < 10; i++) {
     byte code[] = {kExprBlock, i, kExprNop};
-    EXPECT_FAILURE(&env_v_v, code);
+    EXPECT_FAILURE(sigs.v_v(), code);
   }
 }
 
 TEST_F(AstDecoderTest, Block1_break) {
   static const byte code[] = {kExprBlock, 1, kExprBr, 0, kExprNop};
-  EXPECT_VERIFIES(&env_v_v, code);
+  EXPECT_VERIFIES(sigs.v_v(), code);
 }
 
 TEST_F(AstDecoderTest, Block2_break) {
   static const byte code[] = {kExprBlock, 2, kExprNop, kExprBr, 0, kExprNop};
-  EXPECT_VERIFIES(&env_v_v, code);
+  EXPECT_VERIFIES(sigs.v_v(), code);
 }
 
 TEST_F(AstDecoderTest, Block1_continue) {
   static const byte code[] = {kExprBlock, 1, kExprBr, 1, kExprNop};
-  EXPECT_FAILURE(&env_v_v, code);
+  EXPECT_FAILURE(sigs.v_v(), code);
 }
 
 TEST_F(AstDecoderTest, Block2_continue) {
   static const byte code[] = {kExprBlock, 2, kExprNop, kExprBr, 1, kExprNop};
-  EXPECT_FAILURE(&env_v_v, code);
+  EXPECT_FAILURE(sigs.v_v(), code);
 }
 
 TEST_F(AstDecoderTest, ExprBlock0) {
   static const byte code[] = {kExprBlock, 0};
-  EXPECT_VERIFIES(&env_v_v, code);
+  EXPECT_VERIFIES(sigs.v_v(), code);
 }
 
 TEST_F(AstDecoderTest, ExprBlock1a) {
   static const byte code[] = {kExprBlock, 1, kExprI8Const, 0};
-  EXPECT_VERIFIES(&env_i_i, code);
+  EXPECT_VERIFIES(sigs.i_i(), code);
 }
 
 TEST_F(AstDecoderTest, ExprBlock1b) {
   static const byte code[] = {kExprBlock, 1, kExprI8Const, 0};
-  EXPECT_FAILURE(&env_f_ff, code);
+  EXPECT_FAILURE(sigs.f_ff(), code);
 }
 
 TEST_F(AstDecoderTest, ExprBlock1c) {
   static const byte code[] = {kExprBlock, 1, kExprF32Const, 0, 0, 0, 0};
-  EXPECT_VERIFIES(&env_f_ff, code);
+  EXPECT_VERIFIES(sigs.f_ff(), code);
 }
 
 TEST_F(AstDecoderTest, IfEmpty) {
   static const byte code[] = {kExprIf, kExprGetLocal, 0, kExprNop};
-  EXPECT_VERIFIES(&env_v_i, code);
+  EXPECT_VERIFIES(sigs.v_i(), code);
 }
 
 TEST_F(AstDecoderTest, IfSet) {
   static const byte code[] = {kExprIfElse, kExprGetLocal, 0, kExprSetLocal,
                               0,           kExprI8Const,  0, kExprNop};
-  EXPECT_VERIFIES(&env_v_i, code);
+  EXPECT_VERIFIES(sigs.v_i(), code);
 }
 
 TEST_F(AstDecoderTest, IfBlock1) {
   static const byte code[] = {kExprIfElse, kExprGetLocal, 0, kExprBlock,
                               1,           kExprSetLocal, 0, kExprI8Const,
                               0,           kExprNop};
-  EXPECT_VERIFIES(&env_v_i, code);
+  EXPECT_VERIFIES(sigs.v_i(), code);
 }
 
 TEST_F(AstDecoderTest, IfBlock2) {
@@ -514,13 +468,13 @@ TEST_F(AstDecoderTest, IfBlock2) {
                               2,       kExprSetLocal, 0, kExprI8Const,
                               0,       kExprSetLocal, 0, kExprI8Const,
                               0};
-  EXPECT_VERIFIES(&env_v_i, code);
+  EXPECT_VERIFIES(sigs.v_i(), code);
 }
 
 TEST_F(AstDecoderTest, IfElseEmpty) {
   static const byte code[] = {kExprIfElse, kExprGetLocal, 0, kExprNop,
                               kExprNop};
-  EXPECT_VERIFIES(&env_v_i, code);
+  EXPECT_VERIFIES(sigs.v_i(), code);
 }
 
 TEST_F(AstDecoderTest, IfElseSet) {
@@ -535,7 +489,7 @@ TEST_F(AstDecoderTest, IfElseSet) {
                               0,
                               kExprI8Const,
                               1};  // --
-  EXPECT_VERIFIES(&env_v_i, code);
+  EXPECT_VERIFIES(sigs.v_i(), code);
 }
 
 TEST_F(AstDecoderTest, IfElseUnreachable) {
@@ -544,111 +498,110 @@ TEST_F(AstDecoderTest, IfElseUnreachable) {
 
   for (size_t i = 0; i < arraysize(kLocalTypes); i++) {
     LocalType types[] = {kAstI32, kLocalTypes[i]};
-    FunctionEnv env;
     FunctionSig sig(1, 1, types);
-    init_env(&env, &sig);
 
     if (kLocalTypes[i] == kAstI32) {
-      EXPECT_VERIFIES(&env, code);
+      EXPECT_VERIFIES(&sig, code);
     } else {
-      EXPECT_FAILURE(&env, code);
+      EXPECT_FAILURE(&sig, code);
     }
   }
 }
 
 TEST_F(AstDecoderTest, Loop0) {
   static const byte code[] = {kExprLoop, 0};
-  EXPECT_VERIFIES(&env_v_v, code);
+  EXPECT_VERIFIES(sigs.v_v(), code);
 }
 
 TEST_F(AstDecoderTest, Loop1) {
   static const byte code[] = {kExprLoop, 1, kExprSetLocal, 0, kExprI8Const, 0};
-  EXPECT_VERIFIES(&env_v_i, code);
+  EXPECT_VERIFIES(sigs.v_i(), code);
 }
 
 TEST_F(AstDecoderTest, Loop2) {
   static const byte code[] = {kExprLoop,     2,                    // --
                               kExprSetLocal, 0, kExprI8Const, 0,   // --
                               kExprSetLocal, 0, kExprI8Const, 0};  // --
-  EXPECT_VERIFIES(&env_v_i, code);
+  EXPECT_VERIFIES(sigs.v_i(), code);
 }
 
 TEST_F(AstDecoderTest, Loop1_continue) {
   static const byte code[] = {kExprLoop, 1, kExprBr, 0, kExprNop};
-  EXPECT_VERIFIES(&env_v_v, code);
+  EXPECT_VERIFIES(sigs.v_v(), code);
 }
 
 TEST_F(AstDecoderTest, Loop1_break) {
   static const byte code[] = {kExprLoop, 1, kExprBr, 1, kExprNop};
-  EXPECT_VERIFIES(&env_v_v, code);
+  EXPECT_VERIFIES(sigs.v_v(), code);
 }
 
 TEST_F(AstDecoderTest, Loop2_continue) {
   static const byte code[] = {kExprLoop,     2,                   // --
                               kExprSetLocal, 0, kExprI8Const, 0,  // --
                               kExprBr,       0, kExprNop};        // --
-  EXPECT_VERIFIES(&env_v_i, code);
+  EXPECT_VERIFIES(sigs.v_i(), code);
 }
 
 TEST_F(AstDecoderTest, Loop2_break) {
   static const byte code[] = {kExprLoop,     2,                   // --
                               kExprSetLocal, 0, kExprI8Const, 0,  // --
                               kExprBr,       1, kExprNop};        // --
-  EXPECT_VERIFIES(&env_v_i, code);
+  EXPECT_VERIFIES(sigs.v_i(), code);
 }
 
 TEST_F(AstDecoderTest, ExprLoop0) {
   static const byte code[] = {kExprLoop, 0};
-  EXPECT_VERIFIES(&env_v_v, code);
+  EXPECT_VERIFIES(sigs.v_v(), code);
 }
 
 TEST_F(AstDecoderTest, ExprLoop1a) {
   static const byte code[] = {kExprLoop, 1, kExprBr, 0, kExprI8Const, 0};
-  EXPECT_VERIFIES(&env_i_i, code);
+  EXPECT_VERIFIES(sigs.i_i(), code);
 }
 
 TEST_F(AstDecoderTest, ExprLoop1b) {
   static const byte code[] = {kExprLoop, 1, kExprBr, 0, kExprI8Const, 0};
-  EXPECT_VERIFIES(&env_i_i, code);
+  EXPECT_VERIFIES(sigs.i_i(), code);
 }
 
 TEST_F(AstDecoderTest, ExprLoop2_unreachable) {
   static const byte code[] = {kExprLoop,    2, kExprBr, 0,
                               kExprI8Const, 0, kExprNop};
-  EXPECT_VERIFIES(&env_i_i, code);
+  EXPECT_VERIFIES(sigs.i_i(), code);
 }
 
 TEST_F(AstDecoderTest, ReturnVoid1) {
   static const byte code[] = {kExprNop};
-  EXPECT_VERIFIES(&env_v_v, code);
-  EXPECT_FAILURE(&env_i_i, code);
-  EXPECT_FAILURE(&env_i_f, code);
+  EXPECT_VERIFIES(sigs.v_v(), code);
+  EXPECT_FAILURE(sigs.i_i(), code);
+  EXPECT_FAILURE(sigs.i_f(), code);
 }
 
 TEST_F(AstDecoderTest, ReturnVoid2) {
   static const byte code[] = {kExprBlock, 1, kExprBr, 0, kExprNop};
-  EXPECT_VERIFIES(&env_v_v, code);
-  EXPECT_FAILURE(&env_i_i, code);
-  EXPECT_FAILURE(&env_i_f, code);
+  EXPECT_VERIFIES(sigs.v_v(), code);
+  EXPECT_FAILURE(sigs.i_i(), code);
+  EXPECT_FAILURE(sigs.i_f(), code);
 }
 
 TEST_F(AstDecoderTest, ReturnVoid3) {
-  EXPECT_VERIFIES_INLINE(&env_v_v, kExprI8Const, 0);
-  EXPECT_VERIFIES_INLINE(&env_v_v, kExprI32Const, 0, 0, 0, 0);
-  EXPECT_VERIFIES_INLINE(&env_v_v, kExprI64Const, 0, 0, 0, 0, 0, 0, 0, 0);
-  EXPECT_VERIFIES_INLINE(&env_v_v, kExprF32Const, 0, 0, 0, 0);
-  EXPECT_VERIFIES_INLINE(&env_v_v, kExprF64Const, 0, 0, 0, 0, 0, 0, 0, 0);
+  EXPECT_VERIFIES_INLINE(sigs.v_v(), kExprI8Const, 0);
+  EXPECT_VERIFIES_INLINE(sigs.v_v(), kExprI32Const, 0, 0, 0, 0);
+  EXPECT_VERIFIES_INLINE(sigs.v_v(), kExprI64Const, 0, 0, 0, 0, 0, 0, 0, 0);
+  EXPECT_VERIFIES_INLINE(sigs.v_v(), kExprF32Const, 0, 0, 0, 0);
+  EXPECT_VERIFIES_INLINE(sigs.v_v(), kExprF64Const, 0, 0, 0, 0, 0, 0, 0, 0);
 
-  EXPECT_VERIFIES_INLINE(&env_v_i, kExprGetLocal, 0);
+  EXPECT_VERIFIES_INLINE(sigs.v_i(), kExprGetLocal, 0);
 }
 
 TEST_F(AstDecoderTest, Unreachable1) {
-  EXPECT_VERIFIES_INLINE(&env_v_v, kExprUnreachable);
-  EXPECT_VERIFIES_INLINE(&env_v_v, kExprUnreachable, kExprUnreachable);
-  EXPECT_VERIFIES_INLINE(&env_v_v, WASM_BLOCK(2, WASM_UNREACHABLE, WASM_ZERO));
-  EXPECT_VERIFIES_INLINE(&env_v_v, WASM_BLOCK(2, WASM_BR(0), WASM_ZERO));
-  EXPECT_VERIFIES_INLINE(&env_v_v, WASM_LOOP(2, WASM_UNREACHABLE, WASM_ZERO));
-  EXPECT_VERIFIES_INLINE(&env_v_v, WASM_LOOP(2, WASM_BR(0), WASM_ZERO));
+  EXPECT_VERIFIES_INLINE(sigs.v_v(), kExprUnreachable);
+  EXPECT_VERIFIES_INLINE(sigs.v_v(), kExprUnreachable, kExprUnreachable);
+  EXPECT_VERIFIES_INLINE(sigs.v_v(),
+                         WASM_BLOCK(2, WASM_UNREACHABLE, WASM_ZERO));
+  EXPECT_VERIFIES_INLINE(sigs.v_v(), WASM_BLOCK(2, WASM_BR(0), WASM_ZERO));
+  EXPECT_VERIFIES_INLINE(sigs.v_v(), WASM_LOOP(2, WASM_UNREACHABLE, WASM_ZERO));
+  EXPECT_VERIFIES_INLINE(sigs.v_v(), WASM_LOOP(2, WASM_BR(0), WASM_ZERO));
 }
 
 TEST_F(AstDecoderTest, Codeiness) {
@@ -668,7 +621,7 @@ TEST_F(AstDecoderTest, ExprIf_off_end) {
   static const byte kCode[] = {kExprIf, kExprGetLocal, 0, kExprGetLocal,
                                0,       kExprGetLocal, 0};
   for (size_t len = 1; len < arraysize(kCode); len++) {
-    Verify(kError, &env_i_i, kCode, kCode + len);
+    Verify(kError, sigs.i_i(), kCode, kCode + len);
   }
 }
 
@@ -677,48 +630,46 @@ TEST_F(AstDecoderTest, ExprIf_type) {
     // float|double ? 1 : 2
     static const byte kCode[] = {kExprIfElse, kExprGetLocal, 0, kExprI8Const,
                                  1,           kExprI8Const,  2};
-    EXPECT_FAILURE(&env_i_f, kCode);
-    EXPECT_FAILURE(&env_i_d, kCode);
+    EXPECT_FAILURE(sigs.i_f(), kCode);
+    EXPECT_FAILURE(sigs.i_d(), kCode);
   }
   {
     // 1 ? float|double : 2
     static const byte kCode[] = {kExprIfElse, kExprI8Const, 1, kExprGetLocal,
                                  0,           kExprI8Const, 2};
-    EXPECT_FAILURE(&env_i_f, kCode);
-    EXPECT_FAILURE(&env_i_d, kCode);
+    EXPECT_FAILURE(sigs.i_f(), kCode);
+    EXPECT_FAILURE(sigs.i_d(), kCode);
   }
   {
     // stmt ? 0 : 1
     static const byte kCode[] = {kExprIfElse, kExprNop,     kExprI8Const,
                                  0,           kExprI8Const, 1};
-    EXPECT_FAILURE(&env_i_i, kCode);
+    EXPECT_FAILURE(sigs.i_i(), kCode);
   }
   {
     // 0 ? stmt : 1
     static const byte kCode[] = {kExprIfElse, kExprI8Const, 0,
                                  kExprNop,    kExprI8Const, 1};
-    EXPECT_FAILURE(&env_i_i, kCode);
+    EXPECT_FAILURE(sigs.i_i(), kCode);
   }
   {
     // 0 ? 1 : stmt
     static const byte kCode[] = {kExprIfElse, kExprI8Const, 0, kExprI8Const, 1,
                                  0,           kExprBlock};
-    EXPECT_FAILURE(&env_i_i, kCode);
+    EXPECT_FAILURE(sigs.i_i(), kCode);
   }
 }
 
 TEST_F(AstDecoderTest, Int64Local_param) {
-  EXPECT_VERIFIES(&env_l_l, kCodeGetLocal0);
+  EXPECT_VERIFIES(sigs.l_l(), kCodeGetLocal0);
 }
 
 TEST_F(AstDecoderTest, Int64Locals) {
   for (byte i = 1; i < 8; i++) {
-    FunctionEnv env;
-    init_env(&env, sigs.l_v());
-    env.AddLocals(kAstI64, i);
+    AddLocals(kAstI64, 1);
     for (byte j = 0; j < i; j++) {
       byte code[] = {kExprGetLocal, j};
-      EXPECT_VERIFIES(&env, code);
+      EXPECT_VERIFIES(sigs.l_v(), code);
     }
   }
 }
@@ -792,19 +743,19 @@ TEST_F(AstDecoderTest, MacrosStmt) {
 }
 
 TEST_F(AstDecoderTest, MacrosBreak) {
-  EXPECT_VERIFIES_INLINE(&env_v_v, WASM_LOOP(1, WASM_BREAK(0)));
+  EXPECT_VERIFIES_INLINE(sigs.v_v(), WASM_LOOP(1, WASM_BREAK(0)));
 
-  EXPECT_VERIFIES_INLINE(&env_i_i, WASM_LOOP(1, WASM_BREAKV(0, WASM_ZERO)));
-  EXPECT_VERIFIES_INLINE(&env_l_l,
+  EXPECT_VERIFIES_INLINE(sigs.i_i(), WASM_LOOP(1, WASM_BREAKV(0, WASM_ZERO)));
+  EXPECT_VERIFIES_INLINE(sigs.l_l(),
                          WASM_LOOP(1, WASM_BREAKV(0, WASM_I64V_1(0))));
-  EXPECT_VERIFIES_INLINE(&env_f_ff,
+  EXPECT_VERIFIES_INLINE(sigs.f_ff(),
                          WASM_LOOP(1, WASM_BREAKV(0, WASM_F32(0.0))));
-  EXPECT_VERIFIES_INLINE(&env_d_dd,
+  EXPECT_VERIFIES_INLINE(sigs.d_dd(),
                          WASM_LOOP(1, WASM_BREAKV(0, WASM_F64(0.0))));
 }
 
 TEST_F(AstDecoderTest, MacrosContinue) {
-  EXPECT_VERIFIES_INLINE(&env_v_v, WASM_LOOP(1, WASM_CONTINUE(0)));
+  EXPECT_VERIFIES_INLINE(sigs.v_v(), WASM_LOOP(1, WASM_CONTINUE(0)));
 }
 
 TEST_F(AstDecoderTest, MacrosVariadic) {
@@ -825,33 +776,25 @@ TEST_F(AstDecoderTest, MacrosNestedBlocks) {
 TEST_F(AstDecoderTest, MultipleReturn) {
   static LocalType kIntTypes5[] = {kAstI32, kAstI32, kAstI32, kAstI32, kAstI32};
   FunctionSig sig_ii_v(2, 0, kIntTypes5);
-  FunctionEnv env_ii_v;
-  init_env(&env_ii_v, &sig_ii_v);
-  EXPECT_VERIFIES_INLINE(&env_ii_v, WASM_RETURN(WASM_ZERO, WASM_ONE));
-  EXPECT_FAILURE_INLINE(&env_ii_v, WASM_RETURN(WASM_ZERO));
+  EXPECT_VERIFIES_INLINE(&sig_ii_v, WASM_RETURN(WASM_ZERO, WASM_ONE));
+  EXPECT_FAILURE_INLINE(&sig_ii_v, WASM_RETURN(WASM_ZERO));
 
   FunctionSig sig_iii_v(3, 0, kIntTypes5);
-  FunctionEnv env_iii_v;
-  init_env(&env_iii_v, &sig_iii_v);
-  EXPECT_VERIFIES_INLINE(&env_iii_v,
+  EXPECT_VERIFIES_INLINE(&sig_iii_v,
                          WASM_RETURN(WASM_ZERO, WASM_ONE, WASM_I8(44)));
-  EXPECT_FAILURE_INLINE(&env_iii_v, WASM_RETURN(WASM_ZERO, WASM_ONE));
+  EXPECT_FAILURE_INLINE(&sig_iii_v, WASM_RETURN(WASM_ZERO, WASM_ONE));
 }
 
 TEST_F(AstDecoderTest, MultipleReturn_fallthru) {
   static LocalType kIntTypes5[] = {kAstI32, kAstI32, kAstI32, kAstI32, kAstI32};
   FunctionSig sig_ii_v(2, 0, kIntTypes5);
-  FunctionEnv env_ii_v;
-  init_env(&env_ii_v, &sig_ii_v);
 
-  EXPECT_VERIFIES_INLINE(&env_ii_v, WASM_ZERO, WASM_ONE);
-  EXPECT_FAILURE_INLINE(&env_ii_v, WASM_ZERO);
+  EXPECT_VERIFIES_INLINE(&sig_ii_v, WASM_ZERO, WASM_ONE);
+  EXPECT_FAILURE_INLINE(&sig_ii_v, WASM_ZERO);
 
   FunctionSig sig_iii_v(3, 0, kIntTypes5);
-  FunctionEnv env_iii_v;
-  init_env(&env_iii_v, &sig_iii_v);
-  EXPECT_VERIFIES_INLINE(&env_iii_v, WASM_ZERO, WASM_ONE, WASM_I8(44));
-  EXPECT_FAILURE_INLINE(&env_iii_v, WASM_ZERO, WASM_ONE);
+  EXPECT_VERIFIES_INLINE(&sig_iii_v, WASM_ZERO, WASM_ONE, WASM_I8(44));
+  EXPECT_FAILURE_INLINE(&sig_iii_v, WASM_ZERO, WASM_ONE);
 }
 
 TEST_F(AstDecoderTest, MacrosInt32) {
@@ -885,13 +828,8 @@ TEST_F(AstDecoderTest, MacrosInt32) {
 }
 
 TEST_F(AstDecoderTest, MacrosInt64) {
-  FunctionEnv env_i_ll;
-  FunctionEnv env_l_ll;
-  init_env(&env_i_ll, sigs.i_ll());
-  init_env(&env_l_ll, sigs.l_ll());
-
-#define VERIFY_L_LL(...) EXPECT_VERIFIES_INLINE(&env_l_ll, __VA_ARGS__)
-#define VERIFY_I_LL(...) EXPECT_VERIFIES_INLINE(&env_i_ll, __VA_ARGS__)
+#define VERIFY_L_LL(...) EXPECT_VERIFIES_INLINE(sigs.l_ll(), __VA_ARGS__)
+#define VERIFY_I_LL(...) EXPECT_VERIFIES_INLINE(sigs.i_ll(), __VA_ARGS__)
 
   VERIFY_L_LL(WASM_I64_ADD(WASM_GET_LOCAL(0), WASM_I64V_1(12)));
   VERIFY_L_LL(WASM_I64_SUB(WASM_GET_LOCAL(0), WASM_I64V_1(13)));
@@ -943,21 +881,21 @@ TEST_F(AstDecoderTest, AllSimpleExpressions) {
 
 TEST_F(AstDecoderTest, MemorySize) {
   byte code[] = {kExprMemorySize};
-  EXPECT_VERIFIES(&env_i_i, code);
-  EXPECT_FAILURE(&env_f_ff, code);
+  EXPECT_VERIFIES(sigs.i_i(), code);
+  EXPECT_FAILURE(sigs.f_ff(), code);
 }
 
 TEST_F(AstDecoderTest, GrowMemory) {
   byte code[] = {kExprGrowMemory, kExprGetLocal, 0};
-  EXPECT_VERIFIES(&env_i_i, code);
-  EXPECT_FAILURE(&env_i_d, code);
+  EXPECT_VERIFIES(sigs.i_i(), code);
+  EXPECT_FAILURE(sigs.i_d(), code);
 }
 
 TEST_F(AstDecoderTest, LoadMemOffset) {
   for (int offset = 0; offset < 128; offset += 7) {
     byte code[] = {kExprI32LoadMem, WasmOpcodes::LoadStoreAccessOf(true),
                    static_cast<byte>(offset), kExprI8Const, 0};
-    EXPECT_VERIFIES(&env_i_i, code);
+    EXPECT_VERIFIES(sigs.i_i(), code);
   }
 }
 
@@ -970,7 +908,7 @@ TEST_F(AstDecoderTest, StoreMemOffset) {
                    0,
                    kExprI8Const,
                    0};
-    EXPECT_VERIFIES(&env_i_i, code);
+    EXPECT_VERIFIES(sigs.i_i(), code);
   }
 }
 
@@ -999,10 +937,10 @@ TEST_F(AstDecoderTest, LoadMemOffset_varint) {
                   kExprI8Const,
                   0};
 
-  EXPECT_VERIFIES(&env_i_i, code1);
-  EXPECT_VERIFIES(&env_i_i, code2);
-  EXPECT_VERIFIES(&env_i_i, code3);
-  EXPECT_VERIFIES(&env_i_i, code4);
+  EXPECT_VERIFIES(sigs.i_i(), code1);
+  EXPECT_VERIFIES(sigs.i_i(), code2);
+  EXPECT_VERIFIES(sigs.i_i(), code3);
+  EXPECT_VERIFIES(sigs.i_i(), code4);
 }
 
 TEST_F(AstDecoderTest, StoreMemOffset_varint) {
@@ -1041,10 +979,10 @@ TEST_F(AstDecoderTest, StoreMemOffset_varint) {
                   kExprI8Const,
                   0};
 
-  EXPECT_VERIFIES(&env_i_i, code1);
-  EXPECT_VERIFIES(&env_i_i, code2);
-  EXPECT_VERIFIES(&env_i_i, code3);
-  EXPECT_VERIFIES(&env_i_i, code4);
+  EXPECT_VERIFIES(sigs.i_i(), code1);
+  EXPECT_VERIFIES(sigs.i_i(), code2);
+  EXPECT_VERIFIES(sigs.i_i(), code3);
+  EXPECT_VERIFIES(sigs.i_i(), code4);
 }
 
 TEST_F(AstDecoderTest, AllLoadMemCombinations) {
@@ -1055,13 +993,11 @@ TEST_F(AstDecoderTest, AllLoadMemCombinations) {
       byte code[] = {
           static_cast<byte>(WasmOpcodes::LoadStoreOpcodeOf(mem_type, false)),
           WasmOpcodes::LoadStoreAccessOf(false), kExprI8Const, 0};
-      FunctionEnv env;
       FunctionSig sig(1, 0, &local_type);
-      init_env(&env, &sig);
       if (local_type == WasmOpcodes::LocalTypeFor(mem_type)) {
-        EXPECT_VERIFIES(&env, code);
+        EXPECT_VERIFIES(&sig, code);
       } else {
-        EXPECT_FAILURE(&env, code);
+        EXPECT_FAILURE(&sig, code);
       }
     }
   }
@@ -1079,13 +1015,11 @@ TEST_F(AstDecoderTest, AllStoreMemCombinations) {
           0,
           kExprGetLocal,
           0};
-      FunctionEnv env;
       FunctionSig sig(0, 1, &local_type);
-      init_env(&env, &sig);
       if (local_type == WasmOpcodes::LocalTypeFor(mem_type)) {
-        EXPECT_VERIFIES(&env, code);
+        EXPECT_VERIFIES(&sig, code);
       } else {
-        EXPECT_FAILURE(&env, code);
+        EXPECT_FAILURE(&sig, code);
       }
     }
   }
@@ -1129,187 +1063,183 @@ class TestModuleEnv : public ModuleEnv {
 }  // namespace
 
 TEST_F(AstDecoderTest, SimpleCalls) {
-  FunctionEnv* env = &env_i_i;
+  FunctionSig* sig = sigs.i_i();
   TestModuleEnv module_env;
-  env->module = &module_env;
+  module = &module_env;
 
   module_env.AddFunction(sigs.i_v());
   module_env.AddFunction(sigs.i_i());
   module_env.AddFunction(sigs.i_ii());
 
-  EXPECT_VERIFIES_INLINE(env, WASM_CALL_FUNCTION(0));
-  EXPECT_VERIFIES_INLINE(env, WASM_CALL_FUNCTION(1, WASM_I8(27)));
-  EXPECT_VERIFIES_INLINE(env, WASM_CALL_FUNCTION(2, WASM_I8(37), WASM_I8(77)));
+  EXPECT_VERIFIES_INLINE(sig, WASM_CALL_FUNCTION(0));
+  EXPECT_VERIFIES_INLINE(sig, WASM_CALL_FUNCTION(1, WASM_I8(27)));
+  EXPECT_VERIFIES_INLINE(sig, WASM_CALL_FUNCTION(2, WASM_I8(37), WASM_I8(77)));
 }
 
 TEST_F(AstDecoderTest, CallsWithTooFewArguments) {
-  FunctionEnv* env = &env_i_i;
+  FunctionSig* sig = sigs.i_i();
   TestModuleEnv module_env;
-  env->module = &module_env;
+  module = &module_env;
 
   module_env.AddFunction(sigs.i_i());
   module_env.AddFunction(sigs.i_ii());
   module_env.AddFunction(sigs.f_ff());
 
-  EXPECT_FAILURE_INLINE(env, WASM_CALL_FUNCTION0(0));
-  EXPECT_FAILURE_INLINE(env, WASM_CALL_FUNCTION(1, WASM_ZERO));
-  EXPECT_FAILURE_INLINE(env, WASM_CALL_FUNCTION(2, WASM_GET_LOCAL(0)));
+  EXPECT_FAILURE_INLINE(sig, WASM_CALL_FUNCTION0(0));
+  EXPECT_FAILURE_INLINE(sig, WASM_CALL_FUNCTION(1, WASM_ZERO));
+  EXPECT_FAILURE_INLINE(sig, WASM_CALL_FUNCTION(2, WASM_GET_LOCAL(0)));
 }
 
 TEST_F(AstDecoderTest, CallsWithSpilloverArgs) {
   static LocalType a_i_ff[] = {kAstI32, kAstF32, kAstF32};
   FunctionSig sig_i_ff(1, 2, a_i_ff);
-  FunctionEnv env_i_ff;
-  init_env(&env_i_ff, &sig_i_ff);
 
   TestModuleEnv module_env;
-  env_i_ff.module = &module_env;
-  env_i_i.module = &module_env;
-  env_f_ff.module = &module_env;
+  module = &module_env;
 
   module_env.AddFunction(&sig_i_ff);
 
-  EXPECT_VERIFIES_INLINE(&env_i_i,
+  EXPECT_VERIFIES_INLINE(sigs.i_i(),
                          WASM_CALL_FUNCTION(0, WASM_F32(0.1), WASM_F32(0.1)));
 
-  EXPECT_VERIFIES_INLINE(&env_i_ff,
+  EXPECT_VERIFIES_INLINE(sigs.i_ff(),
                          WASM_CALL_FUNCTION(0, WASM_F32(0.1), WASM_F32(0.1)));
 
-  EXPECT_FAILURE_INLINE(&env_f_ff,
+  EXPECT_FAILURE_INLINE(sigs.f_ff(),
                         WASM_CALL_FUNCTION(0, WASM_F32(0.1), WASM_F32(0.1)));
 
   EXPECT_FAILURE_INLINE(
-      &env_i_i,
+      sigs.i_i(),
       WASM_CALL_FUNCTION(0, WASM_F32(0.1), WASM_F32(0.1), WASM_F32(0.2)));
 
   EXPECT_VERIFIES_INLINE(
-      &env_f_ff,
+      sigs.f_ff(),
       WASM_CALL_FUNCTION(0, WASM_F32(0.1), WASM_F32(0.1), WASM_F32(11)));
 }
 
 TEST_F(AstDecoderTest, CallsWithMismatchedSigs2) {
-  FunctionEnv* env = &env_i_i;
+  FunctionSig* sig = sigs.i_i();
   TestModuleEnv module_env;
-  env->module = &module_env;
+  module = &module_env;
 
   module_env.AddFunction(sigs.i_i());
 
-  EXPECT_FAILURE_INLINE(env, WASM_CALL_FUNCTION(0, WASM_I64V_1(17)));
-  EXPECT_FAILURE_INLINE(env, WASM_CALL_FUNCTION(0, WASM_F32(17.1)));
-  EXPECT_FAILURE_INLINE(env, WASM_CALL_FUNCTION(0, WASM_F64(17.1)));
+  EXPECT_FAILURE_INLINE(sig, WASM_CALL_FUNCTION(0, WASM_I64V_1(17)));
+  EXPECT_FAILURE_INLINE(sig, WASM_CALL_FUNCTION(0, WASM_F32(17.1)));
+  EXPECT_FAILURE_INLINE(sig, WASM_CALL_FUNCTION(0, WASM_F64(17.1)));
 }
 
 TEST_F(AstDecoderTest, CallsWithMismatchedSigs3) {
-  FunctionEnv* env = &env_i_i;
+  FunctionSig* sig = sigs.i_i();
   TestModuleEnv module_env;
-  env->module = &module_env;
+  module = &module_env;
 
   module_env.AddFunction(sigs.i_f());
 
-  EXPECT_FAILURE_INLINE(env, WASM_CALL_FUNCTION(0, WASM_I8(17)));
-  EXPECT_FAILURE_INLINE(env, WASM_CALL_FUNCTION(0, WASM_I64V_1(27)));
-  EXPECT_FAILURE_INLINE(env, WASM_CALL_FUNCTION(0, WASM_F64(37.2)));
+  EXPECT_FAILURE_INLINE(sig, WASM_CALL_FUNCTION(0, WASM_I8(17)));
+  EXPECT_FAILURE_INLINE(sig, WASM_CALL_FUNCTION(0, WASM_I64V_1(27)));
+  EXPECT_FAILURE_INLINE(sig, WASM_CALL_FUNCTION(0, WASM_F64(37.2)));
 
   module_env.AddFunction(sigs.i_d());
 
-  EXPECT_FAILURE_INLINE(env, WASM_CALL_FUNCTION(1, WASM_I8(16)));
-  EXPECT_FAILURE_INLINE(env, WASM_CALL_FUNCTION(1, WASM_I64V_1(16)));
-  EXPECT_FAILURE_INLINE(env, WASM_CALL_FUNCTION(1, WASM_F32(17.6)));
+  EXPECT_FAILURE_INLINE(sig, WASM_CALL_FUNCTION(1, WASM_I8(16)));
+  EXPECT_FAILURE_INLINE(sig, WASM_CALL_FUNCTION(1, WASM_I64V_1(16)));
+  EXPECT_FAILURE_INLINE(sig, WASM_CALL_FUNCTION(1, WASM_F32(17.6)));
 }
 
 TEST_F(AstDecoderTest, SimpleIndirectCalls) {
-  FunctionEnv* env = &env_i_i;
+  FunctionSig* sig = sigs.i_i();
   TestModuleEnv module_env;
-  env->module = &module_env;
+  module = &module_env;
 
   byte f0 = module_env.AddSignature(sigs.i_v());
   byte f1 = module_env.AddSignature(sigs.i_i());
   byte f2 = module_env.AddSignature(sigs.i_ii());
 
-  EXPECT_VERIFIES_INLINE(env, WASM_CALL_INDIRECT0(f0, WASM_ZERO));
-  EXPECT_VERIFIES_INLINE(env, WASM_CALL_INDIRECT(f1, WASM_ZERO, WASM_I8(22)));
+  EXPECT_VERIFIES_INLINE(sig, WASM_CALL_INDIRECT0(f0, WASM_ZERO));
+  EXPECT_VERIFIES_INLINE(sig, WASM_CALL_INDIRECT(f1, WASM_ZERO, WASM_I8(22)));
   EXPECT_VERIFIES_INLINE(
-      env, WASM_CALL_INDIRECT(f2, WASM_ZERO, WASM_I8(32), WASM_I8(72)));
+      sig, WASM_CALL_INDIRECT(f2, WASM_ZERO, WASM_I8(32), WASM_I8(72)));
 }
 
 TEST_F(AstDecoderTest, IndirectCallsOutOfBounds) {
-  FunctionEnv* env = &env_i_i;
+  FunctionSig* sig = sigs.i_i();
   TestModuleEnv module_env;
-  env->module = &module_env;
+  module = &module_env;
 
-  EXPECT_FAILURE_INLINE(env, WASM_CALL_INDIRECT0(0, WASM_ZERO));
+  EXPECT_FAILURE_INLINE(sig, WASM_CALL_INDIRECT0(0, WASM_ZERO));
   module_env.AddSignature(sigs.i_v());
-  EXPECT_VERIFIES_INLINE(env, WASM_CALL_INDIRECT0(0, WASM_ZERO));
+  EXPECT_VERIFIES_INLINE(sig, WASM_CALL_INDIRECT0(0, WASM_ZERO));
 
-  EXPECT_FAILURE_INLINE(env, WASM_CALL_INDIRECT(1, WASM_ZERO, WASM_I8(22)));
+  EXPECT_FAILURE_INLINE(sig, WASM_CALL_INDIRECT(1, WASM_ZERO, WASM_I8(22)));
   module_env.AddSignature(sigs.i_i());
-  EXPECT_VERIFIES_INLINE(env, WASM_CALL_INDIRECT(1, WASM_ZERO, WASM_I8(27)));
+  EXPECT_VERIFIES_INLINE(sig, WASM_CALL_INDIRECT(1, WASM_ZERO, WASM_I8(27)));
 
-  EXPECT_FAILURE_INLINE(env, WASM_CALL_INDIRECT(2, WASM_ZERO, WASM_I8(27)));
+  EXPECT_FAILURE_INLINE(sig, WASM_CALL_INDIRECT(2, WASM_ZERO, WASM_I8(27)));
 }
 
 TEST_F(AstDecoderTest, IndirectCallsWithMismatchedSigs3) {
-  FunctionEnv* env = &env_i_i;
+  FunctionSig* sig = sigs.i_i();
   TestModuleEnv module_env;
-  env->module = &module_env;
+  module = &module_env;
 
   byte f0 = module_env.AddFunction(sigs.i_f());
 
-  EXPECT_FAILURE_INLINE(env, WASM_CALL_INDIRECT(f0, WASM_ZERO, WASM_I8(17)));
-  EXPECT_FAILURE_INLINE(env,
+  EXPECT_FAILURE_INLINE(sig, WASM_CALL_INDIRECT(f0, WASM_ZERO, WASM_I8(17)));
+  EXPECT_FAILURE_INLINE(sig,
                         WASM_CALL_INDIRECT(f0, WASM_ZERO, WASM_I64V_1(27)));
-  EXPECT_FAILURE_INLINE(env, WASM_CALL_INDIRECT(f0, WASM_ZERO, WASM_F64(37.2)));
+  EXPECT_FAILURE_INLINE(sig, WASM_CALL_INDIRECT(f0, WASM_ZERO, WASM_F64(37.2)));
 
-  EXPECT_FAILURE_INLINE(env, WASM_CALL_INDIRECT0(f0, WASM_I8(17)));
-  EXPECT_FAILURE_INLINE(env, WASM_CALL_INDIRECT0(f0, WASM_I64V_1(27)));
-  EXPECT_FAILURE_INLINE(env, WASM_CALL_INDIRECT0(f0, WASM_F64(37.2)));
+  EXPECT_FAILURE_INLINE(sig, WASM_CALL_INDIRECT0(f0, WASM_I8(17)));
+  EXPECT_FAILURE_INLINE(sig, WASM_CALL_INDIRECT0(f0, WASM_I64V_1(27)));
+  EXPECT_FAILURE_INLINE(sig, WASM_CALL_INDIRECT0(f0, WASM_F64(37.2)));
 
   byte f1 = module_env.AddFunction(sigs.i_d());
 
-  EXPECT_FAILURE_INLINE(env, WASM_CALL_INDIRECT(f1, WASM_ZERO, WASM_I8(16)));
-  EXPECT_FAILURE_INLINE(env,
+  EXPECT_FAILURE_INLINE(sig, WASM_CALL_INDIRECT(f1, WASM_ZERO, WASM_I8(16)));
+  EXPECT_FAILURE_INLINE(sig,
                         WASM_CALL_INDIRECT(f1, WASM_ZERO, WASM_I64V_1(16)));
-  EXPECT_FAILURE_INLINE(env, WASM_CALL_INDIRECT(f1, WASM_ZERO, WASM_F32(17.6)));
+  EXPECT_FAILURE_INLINE(sig, WASM_CALL_INDIRECT(f1, WASM_ZERO, WASM_F32(17.6)));
 }
 
 TEST_F(AstDecoderTest, SimpleImportCalls) {
-  FunctionEnv* env = &env_i_i;
+  FunctionSig* sig = sigs.i_i();
   TestModuleEnv module_env;
-  env->module = &module_env;
+  module = &module_env;
 
   byte f0 = module_env.AddImport(sigs.i_v());
   byte f1 = module_env.AddImport(sigs.i_i());
   byte f2 = module_env.AddImport(sigs.i_ii());
 
-  EXPECT_VERIFIES_INLINE(env, WASM_CALL_IMPORT0(f0));
-  EXPECT_VERIFIES_INLINE(env, WASM_CALL_IMPORT(f1, WASM_I8(22)));
-  EXPECT_VERIFIES_INLINE(env, WASM_CALL_IMPORT(f2, WASM_I8(32), WASM_I8(72)));
+  EXPECT_VERIFIES_INLINE(sig, WASM_CALL_IMPORT0(f0));
+  EXPECT_VERIFIES_INLINE(sig, WASM_CALL_IMPORT(f1, WASM_I8(22)));
+  EXPECT_VERIFIES_INLINE(sig, WASM_CALL_IMPORT(f2, WASM_I8(32), WASM_I8(72)));
 }
 
 TEST_F(AstDecoderTest, ImportCallsWithMismatchedSigs3) {
-  FunctionEnv* env = &env_i_i;
+  FunctionSig* sig = sigs.i_i();
   TestModuleEnv module_env;
-  env->module = &module_env;
+  module = &module_env;
 
   byte f0 = module_env.AddImport(sigs.i_f());
 
-  EXPECT_FAILURE_INLINE(env, WASM_CALL_IMPORT0(f0));
-  EXPECT_FAILURE_INLINE(env, WASM_CALL_IMPORT(f0, WASM_I8(17)));
-  EXPECT_FAILURE_INLINE(env, WASM_CALL_IMPORT(f0, WASM_I64V_1(27)));
-  EXPECT_FAILURE_INLINE(env, WASM_CALL_IMPORT(f0, WASM_F64(37.2)));
+  EXPECT_FAILURE_INLINE(sig, WASM_CALL_IMPORT0(f0));
+  EXPECT_FAILURE_INLINE(sig, WASM_CALL_IMPORT(f0, WASM_I8(17)));
+  EXPECT_FAILURE_INLINE(sig, WASM_CALL_IMPORT(f0, WASM_I64V_1(27)));
+  EXPECT_FAILURE_INLINE(sig, WASM_CALL_IMPORT(f0, WASM_F64(37.2)));
 
   byte f1 = module_env.AddImport(sigs.i_d());
 
-  EXPECT_FAILURE_INLINE(env, WASM_CALL_IMPORT0(f1));
-  EXPECT_FAILURE_INLINE(env, WASM_CALL_IMPORT(f1, WASM_I8(16)));
-  EXPECT_FAILURE_INLINE(env, WASM_CALL_IMPORT(f1, WASM_I64V_1(16)));
-  EXPECT_FAILURE_INLINE(env, WASM_CALL_IMPORT(f1, WASM_F32(17.6)));
+  EXPECT_FAILURE_INLINE(sig, WASM_CALL_IMPORT0(f1));
+  EXPECT_FAILURE_INLINE(sig, WASM_CALL_IMPORT(f1, WASM_I8(16)));
+  EXPECT_FAILURE_INLINE(sig, WASM_CALL_IMPORT(f1, WASM_I64V_1(16)));
+  EXPECT_FAILURE_INLINE(sig, WASM_CALL_IMPORT(f1, WASM_F32(17.6)));
 }
 
 TEST_F(AstDecoderTest, Int32Globals) {
-  FunctionEnv* env = &env_i_i;
+  FunctionSig* sig = sigs.i_i();
   TestModuleEnv module_env;
-  env->module = &module_env;
+  module = &module_env;
 
   module_env.AddGlobal(MachineType::Int8());
   module_env.AddGlobal(MachineType::Uint8());
@@ -1318,81 +1248,77 @@ TEST_F(AstDecoderTest, Int32Globals) {
   module_env.AddGlobal(MachineType::Int32());
   module_env.AddGlobal(MachineType::Uint32());
 
-  EXPECT_VERIFIES_INLINE(env, WASM_LOAD_GLOBAL(0));
-  EXPECT_VERIFIES_INLINE(env, WASM_LOAD_GLOBAL(1));
-  EXPECT_VERIFIES_INLINE(env, WASM_LOAD_GLOBAL(2));
-  EXPECT_VERIFIES_INLINE(env, WASM_LOAD_GLOBAL(3));
-  EXPECT_VERIFIES_INLINE(env, WASM_LOAD_GLOBAL(4));
-  EXPECT_VERIFIES_INLINE(env, WASM_LOAD_GLOBAL(5));
+  EXPECT_VERIFIES_INLINE(sig, WASM_LOAD_GLOBAL(0));
+  EXPECT_VERIFIES_INLINE(sig, WASM_LOAD_GLOBAL(1));
+  EXPECT_VERIFIES_INLINE(sig, WASM_LOAD_GLOBAL(2));
+  EXPECT_VERIFIES_INLINE(sig, WASM_LOAD_GLOBAL(3));
+  EXPECT_VERIFIES_INLINE(sig, WASM_LOAD_GLOBAL(4));
+  EXPECT_VERIFIES_INLINE(sig, WASM_LOAD_GLOBAL(5));
 
-  EXPECT_VERIFIES_INLINE(env, WASM_STORE_GLOBAL(0, WASM_GET_LOCAL(0)));
-  EXPECT_VERIFIES_INLINE(env, WASM_STORE_GLOBAL(1, WASM_GET_LOCAL(0)));
-  EXPECT_VERIFIES_INLINE(env, WASM_STORE_GLOBAL(2, WASM_GET_LOCAL(0)));
-  EXPECT_VERIFIES_INLINE(env, WASM_STORE_GLOBAL(3, WASM_GET_LOCAL(0)));
-  EXPECT_VERIFIES_INLINE(env, WASM_STORE_GLOBAL(4, WASM_GET_LOCAL(0)));
-  EXPECT_VERIFIES_INLINE(env, WASM_STORE_GLOBAL(5, WASM_GET_LOCAL(0)));
+  EXPECT_VERIFIES_INLINE(sig, WASM_STORE_GLOBAL(0, WASM_GET_LOCAL(0)));
+  EXPECT_VERIFIES_INLINE(sig, WASM_STORE_GLOBAL(1, WASM_GET_LOCAL(0)));
+  EXPECT_VERIFIES_INLINE(sig, WASM_STORE_GLOBAL(2, WASM_GET_LOCAL(0)));
+  EXPECT_VERIFIES_INLINE(sig, WASM_STORE_GLOBAL(3, WASM_GET_LOCAL(0)));
+  EXPECT_VERIFIES_INLINE(sig, WASM_STORE_GLOBAL(4, WASM_GET_LOCAL(0)));
+  EXPECT_VERIFIES_INLINE(sig, WASM_STORE_GLOBAL(5, WASM_GET_LOCAL(0)));
 }
 
 TEST_F(AstDecoderTest, Int32Globals_fail) {
-  FunctionEnv* env = &env_i_i;
+  FunctionSig* sig = sigs.i_i();
   TestModuleEnv module_env;
-  env->module = &module_env;
+  module = &module_env;
 
   module_env.AddGlobal(MachineType::Int64());
   module_env.AddGlobal(MachineType::Uint64());
   module_env.AddGlobal(MachineType::Float32());
   module_env.AddGlobal(MachineType::Float64());
 
-  EXPECT_FAILURE_INLINE(env, WASM_LOAD_GLOBAL(0));
-  EXPECT_FAILURE_INLINE(env, WASM_LOAD_GLOBAL(1));
-  EXPECT_FAILURE_INLINE(env, WASM_LOAD_GLOBAL(2));
-  EXPECT_FAILURE_INLINE(env, WASM_LOAD_GLOBAL(3));
+  EXPECT_FAILURE_INLINE(sig, WASM_LOAD_GLOBAL(0));
+  EXPECT_FAILURE_INLINE(sig, WASM_LOAD_GLOBAL(1));
+  EXPECT_FAILURE_INLINE(sig, WASM_LOAD_GLOBAL(2));
+  EXPECT_FAILURE_INLINE(sig, WASM_LOAD_GLOBAL(3));
 
-  EXPECT_FAILURE_INLINE(env, WASM_STORE_GLOBAL(0, WASM_GET_LOCAL(0)));
-  EXPECT_FAILURE_INLINE(env, WASM_STORE_GLOBAL(1, WASM_GET_LOCAL(0)));
-  EXPECT_FAILURE_INLINE(env, WASM_STORE_GLOBAL(2, WASM_GET_LOCAL(0)));
-  EXPECT_FAILURE_INLINE(env, WASM_STORE_GLOBAL(3, WASM_GET_LOCAL(0)));
+  EXPECT_FAILURE_INLINE(sig, WASM_STORE_GLOBAL(0, WASM_GET_LOCAL(0)));
+  EXPECT_FAILURE_INLINE(sig, WASM_STORE_GLOBAL(1, WASM_GET_LOCAL(0)));
+  EXPECT_FAILURE_INLINE(sig, WASM_STORE_GLOBAL(2, WASM_GET_LOCAL(0)));
+  EXPECT_FAILURE_INLINE(sig, WASM_STORE_GLOBAL(3, WASM_GET_LOCAL(0)));
 }
 
 TEST_F(AstDecoderTest, Int64Globals) {
-  FunctionEnv* env = &env_l_l;
+  FunctionSig* sig = sigs.l_l();
   TestModuleEnv module_env;
-  env->module = &module_env;
+  module = &module_env;
 
   module_env.AddGlobal(MachineType::Int64());
   module_env.AddGlobal(MachineType::Uint64());
 
-  EXPECT_VERIFIES_INLINE(env, WASM_LOAD_GLOBAL(0));
-  EXPECT_VERIFIES_INLINE(env, WASM_LOAD_GLOBAL(1));
+  EXPECT_VERIFIES_INLINE(sig, WASM_LOAD_GLOBAL(0));
+  EXPECT_VERIFIES_INLINE(sig, WASM_LOAD_GLOBAL(1));
 
-  EXPECT_VERIFIES_INLINE(env, WASM_STORE_GLOBAL(0, WASM_GET_LOCAL(0)));
-  EXPECT_VERIFIES_INLINE(env, WASM_STORE_GLOBAL(1, WASM_GET_LOCAL(0)));
+  EXPECT_VERIFIES_INLINE(sig, WASM_STORE_GLOBAL(0, WASM_GET_LOCAL(0)));
+  EXPECT_VERIFIES_INLINE(sig, WASM_STORE_GLOBAL(1, WASM_GET_LOCAL(0)));
 }
 
 TEST_F(AstDecoderTest, Float32Globals) {
-  FunctionEnv env_f_ff;
-  FunctionEnv* env = &env_f_ff;
-  init_env(env, sigs.f_ff());
+  FunctionSig* sig = sigs.f_ff();
   TestModuleEnv module_env;
-  env->module = &module_env;
+  module = &module_env;
 
   module_env.AddGlobal(MachineType::Float32());
 
-  EXPECT_VERIFIES_INLINE(env, WASM_LOAD_GLOBAL(0));
-  EXPECT_VERIFIES_INLINE(env, WASM_STORE_GLOBAL(0, WASM_GET_LOCAL(0)));
+  EXPECT_VERIFIES_INLINE(sig, WASM_LOAD_GLOBAL(0));
+  EXPECT_VERIFIES_INLINE(sig, WASM_STORE_GLOBAL(0, WASM_GET_LOCAL(0)));
 }
 
 TEST_F(AstDecoderTest, Float64Globals) {
-  FunctionEnv env_d_dd;
-  FunctionEnv* env = &env_d_dd;
-  init_env(env, sigs.d_dd());
+  FunctionSig* sig = sigs.d_dd();
   TestModuleEnv module_env;
-  env->module = &module_env;
+  module = &module_env;
 
   module_env.AddGlobal(MachineType::Float64());
 
-  EXPECT_VERIFIES_INLINE(env, WASM_LOAD_GLOBAL(0));
-  EXPECT_VERIFIES_INLINE(env, WASM_STORE_GLOBAL(0, WASM_GET_LOCAL(0)));
+  EXPECT_VERIFIES_INLINE(sig, WASM_LOAD_GLOBAL(0));
+  EXPECT_VERIFIES_INLINE(sig, WASM_STORE_GLOBAL(0, WASM_GET_LOCAL(0)));
 }
 
 TEST_F(AstDecoderTest, AllLoadGlobalCombinations) {
@@ -1400,16 +1326,14 @@ TEST_F(AstDecoderTest, AllLoadGlobalCombinations) {
     LocalType local_type = kLocalTypes[i];
     for (size_t j = 0; j < arraysize(machineTypes); j++) {
       MachineType mem_type = machineTypes[j];
-      FunctionEnv env;
       FunctionSig sig(1, 0, &local_type);
       TestModuleEnv module_env;
-      init_env(&env, &sig);
-      env.module = &module_env;
+      module = &module_env;
       module_env.AddGlobal(mem_type);
       if (local_type == WasmOpcodes::LocalTypeFor(mem_type)) {
-        EXPECT_VERIFIES_INLINE(&env, WASM_LOAD_GLOBAL(0));
+        EXPECT_VERIFIES_INLINE(&sig, WASM_LOAD_GLOBAL(0));
       } else {
-        EXPECT_FAILURE_INLINE(&env, WASM_LOAD_GLOBAL(0));
+        EXPECT_FAILURE_INLINE(&sig, WASM_LOAD_GLOBAL(0));
       }
     }
   }
@@ -1420,16 +1344,14 @@ TEST_F(AstDecoderTest, AllStoreGlobalCombinations) {
     LocalType local_type = kLocalTypes[i];
     for (size_t j = 0; j < arraysize(machineTypes); j++) {
       MachineType mem_type = machineTypes[j];
-      FunctionEnv env;
       FunctionSig sig(0, 1, &local_type);
       TestModuleEnv module_env;
-      init_env(&env, &sig);
-      env.module = &module_env;
+      module = &module_env;
       module_env.AddGlobal(mem_type);
       if (local_type == WasmOpcodes::LocalTypeFor(mem_type)) {
-        EXPECT_VERIFIES_INLINE(&env, WASM_STORE_GLOBAL(0, WASM_GET_LOCAL(0)));
+        EXPECT_VERIFIES_INLINE(&sig, WASM_STORE_GLOBAL(0, WASM_GET_LOCAL(0)));
       } else {
-        EXPECT_FAILURE_INLINE(&env, WASM_STORE_GLOBAL(0, WASM_GET_LOCAL(0)));
+        EXPECT_FAILURE_INLINE(&sig, WASM_STORE_GLOBAL(0, WASM_GET_LOCAL(0)));
       }
     }
   }
@@ -1443,58 +1365,57 @@ TEST_F(AstDecoderTest, BreakNesting1) {
                      WASM_SET_LOCAL(0, WASM_I8(1))),
         WASM_GET_LOCAL(0))};
     if (i < 3) {
-      EXPECT_VERIFIES(&env_i_i, code);
+      EXPECT_VERIFIES(sigs.i_i(), code);
     } else {
-      EXPECT_FAILURE(&env_i_i, code);
+      EXPECT_FAILURE(sigs.i_i(), code);
     }
   }
 }
 
 TEST_F(AstDecoderTest, BreakNesting2) {
-  env_v_v.AddLocals(kAstI32, 1);
+  AddLocals(kAstI32, 1);
   for (int i = 0; i < 5; i++) {
-    // (block[2] (loop[2] (if (get p) break[N]) (set p 1)) (return p)) (11)
-    byte code[] = {
-        WASM_BLOCK(1, WASM_LOOP(2, WASM_IF(WASM_GET_LOCAL(0), WASM_BREAK(i)),
-                                WASM_SET_LOCAL(0, WASM_I8(1)))),
-        WASM_I8(11)};
+    // (block[2] (loop[2] (if 0 break[N]) (set p 1)) (return p)) (11)
+    byte code[] = {WASM_BLOCK(1, WASM_LOOP(2, WASM_IF(WASM_ZERO, WASM_BREAK(i)),
+                                           WASM_SET_LOCAL(0, WASM_I8(1)))),
+                   WASM_I8(11)};
     if (i < 2) {
-      EXPECT_VERIFIES(&env_v_v, code);
+      EXPECT_VERIFIES(sigs.v_v(), code);
     } else {
-      EXPECT_FAILURE(&env_v_v, code);
+      EXPECT_FAILURE(sigs.v_v(), code);
     }
   }
 }
 
 TEST_F(AstDecoderTest, BreakNesting3) {
-  env_v_v.AddLocals(kAstI32, 1);
   for (int i = 0; i < 5; i++) {
-    // (block[1] (loop[1] (block[1] (if (get p) break[N])
+    // (block[1] (loop[1] (block[1] (if 0 break[N])
     byte code[] = {WASM_BLOCK(
-        1, WASM_LOOP(
-               1, WASM_BLOCK(1, WASM_IF(WASM_GET_LOCAL(0), WASM_BREAK(i)))))};
+        1, WASM_LOOP(1, WASM_BLOCK(1, WASM_IF(WASM_ZERO, WASM_BREAK(i)))))};
     if (i < 3) {
-      EXPECT_VERIFIES(&env_v_v, code);
+      EXPECT_VERIFIES(sigs.v_v(), code);
     } else {
-      EXPECT_FAILURE(&env_v_v, code);
+      EXPECT_FAILURE(sigs.v_v(), code);
     }
   }
 }
 
 TEST_F(AstDecoderTest, BreaksWithMultipleTypes) {
   EXPECT_FAILURE_INLINE(
-      &env_i_i, WASM_BLOCK(2, WASM_BRV_IF_ZERO(0, WASM_I8(7)), WASM_F32(7.7)));
+      sigs.i_i(),
+      WASM_BLOCK(2, WASM_BRV_IF_ZERO(0, WASM_I8(7)), WASM_F32(7.7)));
 
-  EXPECT_FAILURE_INLINE(&env_i_i,
+  EXPECT_FAILURE_INLINE(sigs.i_i(),
                         WASM_BLOCK(2, WASM_BRV_IF_ZERO(0, WASM_I8(7)),
                                    WASM_BRV_IF_ZERO(0, WASM_F32(7.7))));
-  EXPECT_FAILURE_INLINE(&env_i_i,
+  EXPECT_FAILURE_INLINE(sigs.i_i(),
                         WASM_BLOCK(3, WASM_BRV_IF_ZERO(0, WASM_I8(8)),
                                    WASM_BRV_IF_ZERO(0, WASM_I8(0)),
                                    WASM_BRV_IF_ZERO(0, WASM_F32(7.7))));
-  EXPECT_FAILURE_INLINE(&env_i_i, WASM_BLOCK(3, WASM_BRV_IF_ZERO(0, WASM_I8(9)),
-                                             WASM_BRV_IF_ZERO(0, WASM_F32(7.7)),
-                                             WASM_BRV_IF_ZERO(0, WASM_I8(11))));
+  EXPECT_FAILURE_INLINE(sigs.i_i(),
+                        WASM_BLOCK(3, WASM_BRV_IF_ZERO(0, WASM_I8(9)),
+                                   WASM_BRV_IF_ZERO(0, WASM_F32(7.7)),
+                                   WASM_BRV_IF_ZERO(0, WASM_I8(11))));
 }
 
 TEST_F(AstDecoderTest, BreakNesting_6_levels) {
@@ -1520,32 +1441,32 @@ TEST_F(AstDecoderTest, BreakNesting_6_levels) {
       }
 
       if (i < depth) {
-        EXPECT_VERIFIES(&env_v_v, code);
+        EXPECT_VERIFIES(sigs.v_v(), code);
       } else {
-        EXPECT_FAILURE(&env_v_v, code);
+        EXPECT_FAILURE(sigs.v_v(), code);
       }
     }
   }
 }
 
 TEST_F(AstDecoderTest, ExprBreak_TypeCheck) {
-  FunctionEnv* envs[] = {&env_i_i, &env_l_l, &env_f_ff, &env_d_dd};
-  for (size_t i = 0; i < arraysize(envs); i++) {
-    FunctionEnv* env = envs[i];
+  FunctionSig* sigarray[] = {sigs.i_i(), sigs.l_l(), sigs.f_ff(), sigs.d_dd()};
+  for (size_t i = 0; i < arraysize(sigarray); i++) {
+    FunctionSig* sig = sigarray[i];
     // unify X and X => OK
     EXPECT_VERIFIES_INLINE(
-        env, WASM_BLOCK(2, WASM_IF(WASM_ZERO, WASM_BRV(0, WASM_GET_LOCAL(0))),
+        sig, WASM_BLOCK(2, WASM_IF(WASM_ZERO, WASM_BRV(0, WASM_GET_LOCAL(0))),
                         WASM_GET_LOCAL(0)));
   }
 
   // unify i32 and f32 => fail
   EXPECT_FAILURE_INLINE(
-      &env_i_i,
+      sigs.i_i(),
       WASM_BLOCK(2, WASM_IF(WASM_ZERO, WASM_BRV(0, WASM_ZERO)), WASM_F32(1.2)));
 
   // unify f64 and f64 => OK
   EXPECT_VERIFIES_INLINE(
-      &env_d_dd,
+      sigs.d_dd(),
       WASM_BLOCK(2, WASM_IF(WASM_ZERO, WASM_BRV(0, WASM_GET_LOCAL(0))),
                  WASM_F64(1.2)));
 }
@@ -1560,31 +1481,26 @@ TEST_F(AstDecoderTest, ExprBreak_TypeCheckAll) {
 
   for (size_t i = 0; i < arraysize(kLocalTypes); i++) {
     for (size_t j = 0; j < arraysize(kLocalTypes); j++) {
-      FunctionEnv env;
       LocalType storage[] = {kLocalTypes[i], kLocalTypes[i], kLocalTypes[j]};
       FunctionSig sig(1, 2, storage);
-      init_env(&env, &sig);
 
       if (i == j) {
-        EXPECT_VERIFIES(&env, code1);
-        EXPECT_VERIFIES(&env, code2);
+        EXPECT_VERIFIES(&sig, code1);
+        EXPECT_VERIFIES(&sig, code2);
       } else {
-        EXPECT_FAILURE(&env, code1);
-        EXPECT_FAILURE(&env, code2);
+        EXPECT_FAILURE(&sig, code1);
+        EXPECT_FAILURE(&sig, code2);
       }
     }
   }
 }
 
 TEST_F(AstDecoderTest, ExprBr_Unify) {
-  FunctionEnv env;
-
   for (int which = 0; which < 2; which++) {
     for (size_t i = 0; i < arraysize(kLocalTypes); i++) {
       LocalType type = kLocalTypes[i];
       LocalType storage[] = {kAstI32, kAstI32, type};
       FunctionSig sig(1, 2, storage);
-      init_env(&env, &sig);  // (i32, X) -> i32
 
       byte code1[] = {
           WASM_BLOCK(2, WASM_IF(WASM_ZERO, WASM_BRV(0, WASM_GET_LOCAL(which))),
@@ -1595,37 +1511,34 @@ TEST_F(AstDecoderTest, ExprBr_Unify) {
 
 
       if (type == kAstI32) {
-        EXPECT_VERIFIES(&env, code1);
-        EXPECT_VERIFIES(&env, code2);
+        EXPECT_VERIFIES(&sig, code1);
+        EXPECT_VERIFIES(&sig, code2);
       } else {
-        EXPECT_FAILURE(&env, code1);
-        EXPECT_FAILURE(&env, code2);
+        EXPECT_FAILURE(&sig, code1);
+        EXPECT_FAILURE(&sig, code2);
       }
     }
   }
 }
 
 TEST_F(AstDecoderTest, ExprBrIf_cond_type) {
-  FunctionEnv env;
   byte code[] = {
       WASM_BLOCK(1, WASM_BRV_IF(0, WASM_GET_LOCAL(0), WASM_GET_LOCAL(1)))};
   for (size_t i = 0; i < arraysize(kLocalTypes); i++) {
     for (size_t j = 0; j < arraysize(kLocalTypes); j++) {
       LocalType types[] = {kLocalTypes[i], kLocalTypes[j]};
       FunctionSig sig(0, 2, types);
-      init_env(&env, &sig);
 
       if (types[1] == kAstI32) {
-        EXPECT_VERIFIES(&env, code);
+        EXPECT_VERIFIES(&sig, code);
       } else {
-        EXPECT_FAILURE(&env, code);
+        EXPECT_FAILURE(&sig, code);
       }
     }
   }
 }
 
 TEST_F(AstDecoderTest, ExprBrIf_val_type) {
-  FunctionEnv env;
   byte code[] = {
       WASM_BLOCK(2, WASM_BRV_IF(0, WASM_GET_LOCAL(1), WASM_GET_LOCAL(2)),
                  WASM_GET_LOCAL(0))};
@@ -1634,26 +1547,22 @@ TEST_F(AstDecoderTest, ExprBrIf_val_type) {
       LocalType types[] = {kLocalTypes[i], kLocalTypes[i], kLocalTypes[j],
                            kAstI32};
       FunctionSig sig(1, 3, types);
-      init_env(&env, &sig);
 
       if (i == j) {
-        EXPECT_VERIFIES(&env, code);
+        EXPECT_VERIFIES(&sig, code);
       } else {
-        EXPECT_FAILURE(&env, code);
+        EXPECT_FAILURE(&sig, code);
       }
     }
   }
 }
 
 TEST_F(AstDecoderTest, ExprBrIf_Unify) {
-  FunctionEnv env;
-
   for (int which = 0; which < 2; which++) {
     for (size_t i = 0; i < arraysize(kLocalTypes); i++) {
       LocalType type = kLocalTypes[i];
       LocalType storage[] = {kAstI32, kAstI32, type};
       FunctionSig sig(1, 2, storage);
-      init_env(&env, &sig);  // (i32, X) -> i32
 
       byte code1[] = {WASM_BLOCK(2, WASM_BRV_IF_ZERO(0, WASM_GET_LOCAL(which)),
                                  WASM_GET_LOCAL(which ^ 1))};
@@ -1661,11 +1570,11 @@ TEST_F(AstDecoderTest, ExprBrIf_Unify) {
                                 WASM_GET_LOCAL(which ^ 1))};
 
       if (type == kAstI32) {
-        EXPECT_VERIFIES(&env, code1);
-        EXPECT_VERIFIES(&env, code2);
+        EXPECT_VERIFIES(&sig, code1);
+        EXPECT_VERIFIES(&sig, code2);
       } else {
-        EXPECT_FAILURE(&env, code1);
-        EXPECT_FAILURE(&env, code2);
+        EXPECT_FAILURE(&sig, code1);
+        EXPECT_FAILURE(&sig, code2);
       }
     }
   }
@@ -1673,54 +1582,54 @@ TEST_F(AstDecoderTest, ExprBrIf_Unify) {
 
 TEST_F(AstDecoderTest, BrTable0) {
   static byte code[] = {kExprBrTable, 0, 0};
-  EXPECT_FAILURE(&env_v_v, code);
+  EXPECT_FAILURE(sigs.v_v(), code);
 }
 
 TEST_F(AstDecoderTest, BrTable0b) {
-  static byte code[] = {kExprBrTable, 0, 0, kExprI8Const, 11};
-  EXPECT_FAILURE(&env_v_v, code);
-  EXPECT_FAILURE(&env_i_i, code);
+  static byte code[] = {kExprBrTable, 0, 0, kExprI32Const, 11};
+  EXPECT_FAILURE(sigs.v_v(), code);
+  EXPECT_FAILURE(sigs.i_i(), code);
 }
 
 TEST_F(AstDecoderTest, BrTable0c) {
-  static byte code[] = {kExprBrTable, 0, 1, 0, 0, kExprI8Const, 11};
-  EXPECT_FAILURE(&env_v_v, code);
-  EXPECT_FAILURE(&env_i_i, code);
+  static byte code[] = {kExprBrTable, 0, 1, 0, 0, kExprI32Const, 11};
+  EXPECT_FAILURE(sigs.v_v(), code);
+  EXPECT_FAILURE(sigs.i_i(), code);
 }
 
 TEST_F(AstDecoderTest, BrTable1a) {
   static byte code[] = {
       WASM_BLOCK(1, WASM_BR_TABLE(WASM_I8(67), 0, BR_TARGET(0)))};
-  EXPECT_VERIFIES(&env_v_v, code);
+  EXPECT_VERIFIES(sigs.v_v(), code);
 }
 
 TEST_F(AstDecoderTest, BrTable1b) {
   static byte code[] = {
       WASM_BLOCK(1, WASM_BR_TABLE(WASM_ZERO, 0, BR_TARGET(0)))};
-  EXPECT_VERIFIES(&env_v_v, code);
-  EXPECT_FAILURE(&env_i_i, code);
-  EXPECT_FAILURE(&env_f_ff, code);
-  EXPECT_FAILURE(&env_d_dd, code);
+  EXPECT_VERIFIES(sigs.v_v(), code);
+  EXPECT_FAILURE(sigs.i_i(), code);
+  EXPECT_FAILURE(sigs.f_ff(), code);
+  EXPECT_FAILURE(sigs.d_dd(), code);
 }
 
 TEST_F(AstDecoderTest, BrTable2a) {
   static byte code[] = {
       WASM_BLOCK(1, WASM_BR_TABLE(WASM_I8(67), 1, BR_TARGET(0), BR_TARGET(0)))};
-  EXPECT_VERIFIES(&env_v_v, code);
+  EXPECT_VERIFIES(sigs.v_v(), code);
 }
 
 TEST_F(AstDecoderTest, BrTable2b) {
   static byte code[] = {WASM_BLOCK(
       1, WASM_BLOCK(
              1, WASM_BR_TABLE(WASM_I8(67), 1, BR_TARGET(0), BR_TARGET(1))))};
-  EXPECT_VERIFIES(&env_v_v, code);
+  EXPECT_VERIFIES(sigs.v_v(), code);
 }
 
 TEST_F(AstDecoderTest, BrTable_off_end) {
   static byte code[] = {
       WASM_BLOCK(1, WASM_BR_TABLE(WASM_GET_LOCAL(0), 0, BR_TARGET(0)))};
   for (size_t len = 1; len < sizeof(code); len++) {
-    Verify(kError, &env_i_i, code, code + len);
+    Verify(kError, sigs.i_i(), code, code + len);
   }
 }
 
@@ -1729,9 +1638,9 @@ TEST_F(AstDecoderTest, BrTable_invalid_br1) {
     byte code[] = {
         WASM_BLOCK(1, WASM_BR_TABLE(WASM_GET_LOCAL(0), 0, BR_TARGET(depth)))};
     if (depth == 0) {
-      EXPECT_VERIFIES(&env_v_i, code);
+      EXPECT_VERIFIES(sigs.v_i(), code);
     } else {
-      EXPECT_FAILURE(&env_v_i, code);
+      EXPECT_FAILURE(sigs.v_i(), code);
     }
   }
 }
@@ -1741,48 +1650,50 @@ TEST_F(AstDecoderTest, BrTable_invalid_br2) {
     byte code[] = {
         WASM_LOOP(1, WASM_BR_TABLE(WASM_GET_LOCAL(0), 0, BR_TARGET(depth)))};
     if (depth <= 1) {
-      EXPECT_VERIFIES(&env_v_i, code);
+      EXPECT_VERIFIES(sigs.v_i(), code);
     } else {
-      EXPECT_FAILURE(&env_v_i, code);
+      EXPECT_FAILURE(sigs.v_i(), code);
     }
   }
 }
 
 TEST_F(AstDecoderTest, ExprBreakNesting1) {
-  EXPECT_VERIFIES_INLINE(&env_v_v, WASM_BLOCK(1, WASM_BRV(0, WASM_ZERO)));
-  EXPECT_VERIFIES_INLINE(&env_v_v, WASM_BLOCK(1, WASM_BR(0)));
-  EXPECT_VERIFIES_INLINE(&env_v_v,
+  EXPECT_VERIFIES_INLINE(sigs.v_v(), WASM_BLOCK(1, WASM_BRV(0, WASM_ZERO)));
+  EXPECT_VERIFIES_INLINE(sigs.v_v(), WASM_BLOCK(1, WASM_BR(0)));
+  EXPECT_VERIFIES_INLINE(sigs.v_v(),
                          WASM_BLOCK(1, WASM_BRV_IF(0, WASM_ZERO, WASM_ZERO)));
-  EXPECT_VERIFIES_INLINE(&env_v_v, WASM_BLOCK(1, WASM_BR_IF(0, WASM_ZERO)));
+  EXPECT_VERIFIES_INLINE(sigs.v_v(), WASM_BLOCK(1, WASM_BR_IF(0, WASM_ZERO)));
 
-  EXPECT_VERIFIES_INLINE(&env_v_v, WASM_LOOP(1, WASM_BRV(0, WASM_ZERO)));
-  EXPECT_VERIFIES_INLINE(&env_v_v, WASM_LOOP(1, WASM_BR(0)));
-  EXPECT_VERIFIES_INLINE(&env_v_v,
+  EXPECT_VERIFIES_INLINE(sigs.v_v(), WASM_LOOP(1, WASM_BRV(0, WASM_ZERO)));
+  EXPECT_VERIFIES_INLINE(sigs.v_v(), WASM_LOOP(1, WASM_BR(0)));
+  EXPECT_VERIFIES_INLINE(sigs.v_v(),
                          WASM_LOOP(1, WASM_BRV_IF(0, WASM_ZERO, WASM_ZERO)));
-  EXPECT_VERIFIES_INLINE(&env_v_v, WASM_LOOP(1, WASM_BR_IF(0, WASM_ZERO)));
+  EXPECT_VERIFIES_INLINE(sigs.v_v(), WASM_LOOP(1, WASM_BR_IF(0, WASM_ZERO)));
 
-  EXPECT_VERIFIES_INLINE(&env_v_v, WASM_LOOP(1, WASM_BRV(1, WASM_ZERO)));
-  EXPECT_VERIFIES_INLINE(&env_v_v, WASM_LOOP(1, WASM_BR(1)));
+  EXPECT_VERIFIES_INLINE(sigs.v_v(), WASM_LOOP(1, WASM_BRV(1, WASM_ZERO)));
+  EXPECT_VERIFIES_INLINE(sigs.v_v(), WASM_LOOP(1, WASM_BR(1)));
 }
 
 TEST_F(AstDecoderTest, Select) {
   EXPECT_VERIFIES_INLINE(
-      &env_i_i, WASM_SELECT(WASM_GET_LOCAL(0), WASM_GET_LOCAL(0), WASM_ZERO));
-  EXPECT_VERIFIES_INLINE(&env_f_ff,
+      sigs.i_i(), WASM_SELECT(WASM_GET_LOCAL(0), WASM_GET_LOCAL(0), WASM_ZERO));
+  EXPECT_VERIFIES_INLINE(sigs.f_ff(),
                          WASM_SELECT(WASM_F32(0.0), WASM_F32(0.0), WASM_ZERO));
-  EXPECT_VERIFIES_INLINE(&env_d_dd,
+  EXPECT_VERIFIES_INLINE(sigs.d_dd(),
                          WASM_SELECT(WASM_F64(0.0), WASM_F64(0.0), WASM_ZERO));
   EXPECT_VERIFIES_INLINE(
-      &env_l_l, WASM_SELECT(WASM_I64V_1(0), WASM_I64V_1(0), WASM_ZERO));
+      sigs.l_l(), WASM_SELECT(WASM_I64V_1(0), WASM_I64V_1(0), WASM_ZERO));
 }
 
 TEST_F(AstDecoderTest, Select_fail1) {
-  EXPECT_FAILURE_INLINE(&env_i_i, WASM_SELECT(WASM_F32(0.0), WASM_GET_LOCAL(0),
-                                              WASM_GET_LOCAL(0)));
-  EXPECT_FAILURE_INLINE(&env_i_i, WASM_SELECT(WASM_GET_LOCAL(0), WASM_F32(0.0),
-                                              WASM_GET_LOCAL(0)));
   EXPECT_FAILURE_INLINE(
-      &env_i_i,
+      sigs.i_i(),
+      WASM_SELECT(WASM_F32(0.0), WASM_GET_LOCAL(0), WASM_GET_LOCAL(0)));
+  EXPECT_FAILURE_INLINE(
+      sigs.i_i(),
+      WASM_SELECT(WASM_GET_LOCAL(0), WASM_F32(0.0), WASM_GET_LOCAL(0)));
+  EXPECT_FAILURE_INLINE(
+      sigs.i_i(),
       WASM_SELECT(WASM_GET_LOCAL(0), WASM_GET_LOCAL(0), WASM_F32(0.0)));
 }
 
@@ -1793,36 +1704,37 @@ TEST_F(AstDecoderTest, Select_fail2) {
 
     LocalType types[] = {type, kAstI32, type};
     FunctionSig sig(1, 2, types);
-    FunctionEnv env;
-    init_env(&env, &sig);
 
     EXPECT_VERIFIES_INLINE(
-        &env,
+        &sig,
         WASM_SELECT(WASM_GET_LOCAL(1), WASM_GET_LOCAL(1), WASM_GET_LOCAL(0)));
 
     EXPECT_FAILURE_INLINE(
-        &env,
+        &sig,
         WASM_SELECT(WASM_GET_LOCAL(1), WASM_GET_LOCAL(0), WASM_GET_LOCAL(0)));
 
     EXPECT_FAILURE_INLINE(
-        &env,
+        &sig,
         WASM_SELECT(WASM_GET_LOCAL(0), WASM_GET_LOCAL(1), WASM_GET_LOCAL(0)));
 
     EXPECT_FAILURE_INLINE(
-        &env,
+        &sig,
         WASM_SELECT(WASM_GET_LOCAL(0), WASM_GET_LOCAL(0), WASM_GET_LOCAL(1)));
   }
 }
 
 TEST_F(AstDecoderTest, Select_TypeCheck) {
-  EXPECT_FAILURE_INLINE(&env_i_i, WASM_SELECT(WASM_F32(9.9), WASM_GET_LOCAL(0),
-                                              WASM_GET_LOCAL(0)));
-
-  EXPECT_FAILURE_INLINE(&env_i_i, WASM_SELECT(WASM_GET_LOCAL(0), WASM_F64(0.25),
-                                              WASM_GET_LOCAL(0)));
+  EXPECT_FAILURE_INLINE(
+      sigs.i_i(),
+      WASM_SELECT(WASM_F32(9.9), WASM_GET_LOCAL(0), WASM_GET_LOCAL(0)));
 
   EXPECT_FAILURE_INLINE(
-      &env_i_i, WASM_SELECT(WASM_F32(9.9), WASM_GET_LOCAL(0), WASM_I64V_1(0)));
+      sigs.i_i(),
+      WASM_SELECT(WASM_GET_LOCAL(0), WASM_F64(0.25), WASM_GET_LOCAL(0)));
+
+  EXPECT_FAILURE_INLINE(
+      sigs.i_i(),
+      WASM_SELECT(WASM_F32(9.9), WASM_GET_LOCAL(0), WASM_I64V_1(0)));
 }
 
 
@@ -2045,16 +1957,18 @@ TEST_F(WasmOpcodeLengthTest, SimpleExpressions) {
 class WasmOpcodeArityTest : public TestWithZone {
  public:
   WasmOpcodeArityTest() : TestWithZone() {}
+  TestModuleEnv module;
+  TestSignatures sigs;
 };
 
-#define EXPECT_ARITY(expected, ...)                                    \
-  {                                                                    \
-    static const byte code[] = {__VA_ARGS__};                          \
-    EXPECT_EQ(expected, OpcodeArity(&env, code, code + sizeof(code))); \
+#define EXPECT_ARITY(expected, ...)                                            \
+  {                                                                            \
+    static const byte code[] = {__VA_ARGS__};                                  \
+    EXPECT_EQ(expected, OpcodeArity(&module, sig, code, code + sizeof(code))); \
   }
 
 TEST_F(WasmOpcodeArityTest, Control) {
-  FunctionEnv env;
+  FunctionSig* sig = sigs.v_v();
   EXPECT_ARITY(0, kExprNop);
 
   EXPECT_ARITY(0, kExprBlock, 0);
@@ -2077,19 +1991,16 @@ TEST_F(WasmOpcodeArityTest, Control) {
   EXPECT_ARITY(2, kExprBrIf);
 
   {
-    TestSignatures sigs;
-    FunctionEnv env;
-    AstDecoderTest::init_env(&env, sigs.v_v());
+    sig = sigs.v_v();
     EXPECT_ARITY(0, kExprReturn);
-    AstDecoderTest::init_env(&env, sigs.i_i());
+    sig = sigs.i_i();
     EXPECT_ARITY(1, kExprReturn);
   }
 }
 
 
 TEST_F(WasmOpcodeArityTest, Misc) {
-  FunctionEnv env;
-
+  FunctionSig* sig = sigs.v_v();
   EXPECT_ARITY(0, kExprI8Const);
   EXPECT_ARITY(0, kExprI32Const);
   EXPECT_ARITY(0, kExprF32Const);
@@ -2103,8 +2014,6 @@ TEST_F(WasmOpcodeArityTest, Misc) {
 
 
 TEST_F(WasmOpcodeArityTest, Calls) {
-  TestSignatures sigs;
-  TestModuleEnv module;
   module.AddFunction(sigs.i_ii());
   module.AddFunction(sigs.i_i());
 
@@ -2115,9 +2024,7 @@ TEST_F(WasmOpcodeArityTest, Calls) {
   module.AddImport(sigs.i_d());
 
   {
-    FunctionEnv env;
-    AstDecoderTest::init_env(&env, sigs.i_ii());
-    env.module = &module;
+    FunctionSig* sig = sigs.i_ii();
 
     EXPECT_ARITY(2, kExprCallFunction, 0);
     EXPECT_ARITY(2, kExprCallImport, 0);
@@ -2127,9 +2034,7 @@ TEST_F(WasmOpcodeArityTest, Calls) {
   }
 
   {
-    FunctionEnv env;
-    AstDecoderTest::init_env(&env, sigs.v_v());
-    env.module = &module;
+    FunctionSig* sig = sigs.v_v();
 
     EXPECT_ARITY(1, kExprCallFunction, 1);
     EXPECT_ARITY(1, kExprCallImport, 1);
@@ -2141,8 +2046,7 @@ TEST_F(WasmOpcodeArityTest, Calls) {
 
 
 TEST_F(WasmOpcodeArityTest, LoadsAndStores) {
-  FunctionEnv env;
-
+  FunctionSig* sig = sigs.v_v();
   EXPECT_ARITY(1, kExprI32LoadMem8S);
   EXPECT_ARITY(1, kExprI32LoadMem8U);
   EXPECT_ARITY(1, kExprI32LoadMem16S);
@@ -2172,16 +2076,14 @@ TEST_F(WasmOpcodeArityTest, LoadsAndStores) {
 
 
 TEST_F(WasmOpcodeArityTest, MiscMemExpressions) {
-  FunctionEnv env;
-
+  FunctionSig* sig = sigs.v_v();
   EXPECT_ARITY(0, kExprMemorySize);
   EXPECT_ARITY(1, kExprGrowMemory);
 }
 
 
 TEST_F(WasmOpcodeArityTest, SimpleExpressions) {
-  FunctionEnv env;
-
+  FunctionSig* sig = sigs.v_v();
   EXPECT_ARITY(2, kExprI32Add);
   EXPECT_ARITY(2, kExprI32Sub);
   EXPECT_ARITY(2, kExprI32Mul);
@@ -2301,6 +2203,95 @@ TEST_F(WasmOpcodeArityTest, SimpleExpressions) {
   EXPECT_ARITY(1, kExprI32ReinterpretF32);
   EXPECT_ARITY(1, kExprI64ReinterpretF64);
 }
+
+typedef std::vector<LocalType>* LocalTypeMap;
+
+class LocalDeclDecoderTest : public TestWithZone {
+ public:
+  size_t ExpectRun(LocalTypeMap map, size_t pos, LocalType expected,
+                   size_t count) {
+    for (size_t i = 0; i < count; i++) {
+      EXPECT_EQ(expected, map->at(pos++));
+    }
+    return pos;
+  }
+};
+
+TEST_F(LocalDeclDecoderTest, NoLocals) {
+  static const byte data[] = {0};
+  LocalTypeMap map = DecodeLocalDeclsForTesting(data, data + sizeof(data));
+  EXPECT_EQ(0, map->size());
+  if (map) delete map;
+}
+
+TEST_F(LocalDeclDecoderTest, OneLocal) {
+  for (size_t i = 0; i < arraysize(kLocalTypes); i++) {
+    LocalType type = kLocalTypes[i];
+    const byte data[] = {
+        1, 1, static_cast<byte>(WasmOpcodes::LocalTypeCodeFor(type))};
+    LocalTypeMap map = DecodeLocalDeclsForTesting(data, data + sizeof(data));
+    EXPECT_EQ(1, map->size());
+    EXPECT_EQ(type, map->at(0));
+    if (map) delete map;
+  }
+}
+
+TEST_F(LocalDeclDecoderTest, FiveLocals) {
+  for (size_t i = 0; i < arraysize(kLocalTypes); i++) {
+    LocalType type = kLocalTypes[i];
+    const byte data[] = {
+        1, 5, static_cast<byte>(WasmOpcodes::LocalTypeCodeFor(type))};
+    LocalTypeMap map = DecodeLocalDeclsForTesting(data, data + sizeof(data));
+    EXPECT_EQ(5, map->size());
+    ExpectRun(map, 0, type, 5);
+    if (map) delete map;
+  }
+}
+
+TEST_F(LocalDeclDecoderTest, MixedLocals) {
+  for (byte a = 0; a < 3; a++) {
+    for (byte b = 0; b < 3; b++) {
+      for (byte c = 0; c < 3; c++) {
+        for (byte d = 0; d < 3; d++) {
+          const byte data[] = {4, a,         kLocalI32, b,        kLocalI64,
+                               c, kLocalF32, d,         kLocalF64};
+          LocalTypeMap map =
+              DecodeLocalDeclsForTesting(data, data + sizeof(data));
+          EXPECT_EQ(a + b + c + d, map->size());
+
+          size_t pos = 0;
+          pos = ExpectRun(map, pos, kAstI32, a);
+          pos = ExpectRun(map, pos, kAstI64, b);
+          pos = ExpectRun(map, pos, kAstF32, c);
+          pos = ExpectRun(map, pos, kAstF64, d);
+
+          if (map) delete map;
+        }
+      }
+    }
+  }
+}
+
+TEST_F(LocalDeclDecoderTest, UseEncoder) {
+  const byte* data = nullptr;
+  const byte* end = nullptr;
+  LocalDeclEncoder local_decls;
+
+  local_decls.AddLocals(5, kAstF32);
+  local_decls.AddLocals(1337, kAstI32);
+  local_decls.AddLocals(212, kAstI64);
+  local_decls.Prepend(&data, &end);
+
+  LocalTypeMap map = DecodeLocalDeclsForTesting(data, end);
+  size_t pos = 0;
+  pos = ExpectRun(map, pos, kAstF32, 5);
+  pos = ExpectRun(map, pos, kAstI32, 1337);
+  pos = ExpectRun(map, pos, kAstI64, 212);
+
+  if (map) delete map;
+  delete[] data;
+}
+
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8
diff --git a/test/unittests/wasm/encoder-unittest.cc b/test/unittests/wasm/encoder-unittest.cc
index e09e71aeb8..69677c2478 100644
--- a/test/unittests/wasm/encoder-unittest.cc
+++ b/test/unittests/wasm/encoder-unittest.cc
@@ -86,9 +86,6 @@ TEST_F(EncoderTest, Function_Builder_Variable_Indexing) {
   byte* header = buffer;
   byte* body = buffer + f->HeaderSize();
   f->Serialize(buffer, &header, &body);
-  for (size_t i = 0; i < 7; i++) {
-    CHECK_EQ(i, static_cast<size_t>(*(buffer + 2 * i + f->HeaderSize() + 1)));
-  }
 }
 
 
@@ -109,15 +106,6 @@ TEST_F(EncoderTest, Function_Builder_Indexing_Variable_Width) {
   byte* body = buffer + f->HeaderSize();
   f->Serialize(buffer, &header, &body);
   body = buffer + f->HeaderSize();
-  for (size_t i = 0; i < 127; i++) {
-    CHECK_EQ(kExprGetLocal, static_cast<size_t>(*(body + 2 * i)));
-    CHECK_EQ(i + 1, static_cast<size_t>(*(body + 2 * i + 1)));
-  }
-  CHECK_EQ(kExprGetLocal, static_cast<size_t>(*(body + 2 * 127)));
-  CHECK_EQ(0x80, static_cast<size_t>(*(body + 2 * 127 + 1)));
-  CHECK_EQ(0x01, static_cast<size_t>(*(body + 2 * 127 + 2)));
-  CHECK_EQ(kExprGetLocal, static_cast<size_t>(*(body + 2 * 127 + 3)));
-  CHECK_EQ(0x00, static_cast<size_t>(*(body + 2 * 127 + 4)));
 }
 
 
diff --git a/test/unittests/wasm/loop-assignment-analysis-unittest.cc b/test/unittests/wasm/loop-assignment-analysis-unittest.cc
index 958621970c..e77c1cfff5 100644
--- a/test/unittests/wasm/loop-assignment-analysis-unittest.cc
+++ b/test/unittests/wasm/loop-assignment-analysis-unittest.cc
@@ -23,25 +23,12 @@ namespace wasm {
 
 class WasmLoopAssignmentAnalyzerTest : public TestWithZone {
  public:
-  WasmLoopAssignmentAnalyzerTest() : TestWithZone(), sigs() {
-    init_env(&env, sigs.v_v());
-  }
-
+  WasmLoopAssignmentAnalyzerTest() : num_locals(0) {}
   TestSignatures sigs;
-  FunctionEnv env;
-
-  static void init_env(FunctionEnv* env, FunctionSig* sig) {
-    env->module = nullptr;
-    env->sig = sig;
-    env->local_i32_count = 0;
-    env->local_i64_count = 0;
-    env->local_f32_count = 0;
-    env->local_f64_count = 0;
-    env->SumLocals();
-  }
+  uint32_t num_locals;
 
   BitVector* Analyze(const byte* start, const byte* end) {
-    return AnalyzeLoopAssignmentForTesting(zone(), &env, start, end);
+    return AnalyzeLoopAssignmentForTesting(zone(), num_locals, start, end);
   }
 };
 
@@ -60,13 +47,13 @@ TEST_F(WasmLoopAssignmentAnalyzerTest, Empty1) {
     for (int j = 0; j < assigned->length(); j++) {
       CHECK_EQ(false, assigned->Contains(j));
     }
-    env.AddLocals(kAstI32, 1);
+    num_locals++;
   }
 }
 
 
 TEST_F(WasmLoopAssignmentAnalyzerTest, One) {
-  env.AddLocals(kAstI32, 5);
+  num_locals = 5;
   for (int i = 0; i < 5; i++) {
     byte code[] = {WASM_LOOP(1, WASM_SET_ZERO(i))};
     BitVector* assigned = Analyze(code, code + arraysize(code));
@@ -78,7 +65,7 @@ TEST_F(WasmLoopAssignmentAnalyzerTest, One) {
 
 
 TEST_F(WasmLoopAssignmentAnalyzerTest, OneBeyond) {
-  env.AddLocals(kAstI32, 5);
+  num_locals = 5;
   for (int i = 0; i < 5; i++) {
     byte code[] = {WASM_LOOP(1, WASM_SET_ZERO(i)), WASM_SET_ZERO(1)};
     BitVector* assigned = Analyze(code, code + arraysize(code));
@@ -90,7 +77,7 @@ TEST_F(WasmLoopAssignmentAnalyzerTest, OneBeyond) {
 
 
 TEST_F(WasmLoopAssignmentAnalyzerTest, Two) {
-  env.AddLocals(kAstI32, 5);
+  num_locals = 5;
   for (int i = 0; i < 5; i++) {
     for (int j = 0; j < 5; j++) {
       byte code[] = {WASM_LOOP(2, WASM_SET_ZERO(i), WASM_SET_ZERO(j))};
@@ -105,7 +92,7 @@ TEST_F(WasmLoopAssignmentAnalyzerTest, Two) {
 
 
 TEST_F(WasmLoopAssignmentAnalyzerTest, NestedIf) {
-  env.AddLocals(kAstI32, 5);
+  num_locals = 5;
   for (int i = 0; i < 5; i++) {
     byte code[] = {WASM_LOOP(
         1, WASM_IF_ELSE(WASM_SET_ZERO(0), WASM_SET_ZERO(i), WASM_SET_ZERO(1)))};
@@ -126,7 +113,7 @@ static byte LEBByte(uint32_t val, byte which) {
 
 
 TEST_F(WasmLoopAssignmentAnalyzerTest, BigLocal) {
-  env.AddLocals(kAstI32, 65000);
+  num_locals = 65000;
   for (int i = 13; i < 65000; i = static_cast<int>(i * 1.5)) {
     byte code[] = {kExprLoop,
                    1,
@@ -148,7 +135,7 @@ TEST_F(WasmLoopAssignmentAnalyzerTest, BigLocal) {
 
 
 TEST_F(WasmLoopAssignmentAnalyzerTest, Break) {
-  env.AddLocals(kAstI32, 3);
+  num_locals = 3;
   byte code[] = {
       WASM_LOOP(1, WASM_IF(WASM_GET_LOCAL(0), WASM_BRV(1, WASM_SET_ZERO(1)))),
       WASM_SET_ZERO(0)};
@@ -162,7 +149,7 @@ TEST_F(WasmLoopAssignmentAnalyzerTest, Break) {
 
 
 TEST_F(WasmLoopAssignmentAnalyzerTest, Loop1) {
-  env.AddLocals(kAstI32, 5);
+  num_locals = 5;
   byte code[] = {
       WASM_LOOP(1, WASM_IF(WASM_GET_LOCAL(0),
                            WASM_BRV(0, WASM_SET_LOCAL(
@@ -179,9 +166,8 @@ TEST_F(WasmLoopAssignmentAnalyzerTest, Loop1) {
 
 
 TEST_F(WasmLoopAssignmentAnalyzerTest, Loop2) {
-  env.AddLocals(kAstI32, 3);
+  num_locals = 6;
   const byte kIter = 0;
-  env.AddLocals(kAstF32, 3);
   const byte kSum = 3;
 
   byte code[] = {WASM_BLOCK(
diff --git a/test/unittests/wasm/module-decoder-unittest.cc b/test/unittests/wasm/module-decoder-unittest.cc
index cab235f61b..c32e873ef8 100644
--- a/test/unittests/wasm/module-decoder-unittest.cc
+++ b/test/unittests/wasm/module-decoder-unittest.cc
@@ -903,10 +903,11 @@ class WasmFunctionVerifyTest : public TestWithZone {};
 TEST_F(WasmFunctionVerifyTest, Ok_v_v_empty) {
   static const byte data[] = {
       0,       kLocalVoid,  // signature
-      3,       0,           // local int32 count
-      4,       0,           // local int64 count
-      5,       0,           // local float32 count
-      6,       0,           // local float64 count
+      4,                    // locals
+      3,       kLocalI32,   // --
+      4,       kLocalI64,   // --
+      5,       kLocalF32,   // --
+      6,       kLocalF64,   // --
       kExprNop              // body
   };
 
@@ -919,12 +920,9 @@ TEST_F(WasmFunctionVerifyTest, Ok_v_v_empty) {
     EXPECT_EQ(0, function->sig->parameter_count());
     EXPECT_EQ(0, function->sig->return_count());
     EXPECT_EQ(0, function->name_offset);
-    EXPECT_EQ(arraysize(data) - 1, function->code_start_offset);
+    EXPECT_EQ(2, function->code_start_offset);
     EXPECT_EQ(arraysize(data), function->code_end_offset);
-    EXPECT_EQ(3, function->local_i32_count);
-    EXPECT_EQ(4, function->local_i64_count);
-    EXPECT_EQ(5, function->local_f32_count);
-    EXPECT_EQ(6, function->local_f64_count);
+    // TODO(titzer): verify encoding of local declarations
     EXPECT_FALSE(function->external);
     EXPECT_FALSE(function->exported);
   }