Remove SminessPropagator and FlowGraphTypePropagator and all associated infrastructure and fields.

runtime/vm/flow_graph_optimizer.cc

Index: runtime/vm/flow_graph_optimizer.cc
diff --git a/runtime/vm/flow_graph_optimizer.cc b/runtime/vm/flow_graph_optimizer.cc
index b1a10b853c13453b59b130a7cc2f17cfb4eea976..f7db803b3ef25a1828f34e70bbf73cee056d16d3 100644
--- a/runtime/vm/flow_graph_optimizer.cc
+++ b/runtime/vm/flow_graph_optimizer.cc
@@ -84,7 +84,7 @@ bool FlowGraphOptimizer::TryCreateICData(InstanceCallInstr* call) {
   GrowableArray<intptr_t> class_ids(call->ic_data()->num_args_tested());
   ASSERT(call->ic_data()->num_args_tested() <= call->ArgumentCount());
   for (intptr_t i = 0; i < call->ic_data()->num_args_tested(); i++) {
-    intptr_t cid = call->ArgumentAt(i)->value()->ResultCid();
+    intptr_t cid = call->ArgumentAt(i)->value()->Type()->ToCid();
     class_ids.Add(cid);
   }
   // TODO(srdjan): Test for other class_ids > 1.
@@ -150,7 +150,7 @@ void FlowGraphOptimizer::SpecializePolymorphicInstanceCall(
     return;  // Already specialized.
   }
 
-  const intptr_t receiver_cid  = call->ArgumentAt(0)->value()->ResultCid();
+  const intptr_t receiver_cid  = call->ArgumentAt(0)->value()->Type()->ToCid();
   if (receiver_cid == kDynamicCid) {
     return;  // No information about receiver was infered.
   }
@@ -231,7 +231,7 @@ void FlowGraphOptimizer::InsertConversion(Representation from,
   Definition* converted = NULL;
   if ((from == kTagged) && (to == kUnboxedMint)) {
     ASSERT((deopt_target != NULL) ||
-           (use->definition()->GetPropagatedCid() == kDoubleCid));
+           (use->Type()->ToCid() == kDoubleCid));
     const intptr_t deopt_id = (deopt_target != NULL) ?
         deopt_target->DeoptimizationTarget() : Isolate::kNoDeoptId;
     converted = new UnboxIntegerInstr(new Value(use->definition()), deopt_id);
@@ -251,7 +251,7 @@ void FlowGraphOptimizer::InsertConversion(Representation from,
     const intptr_t deopt_id = (deopt_target != NULL) ?
         deopt_target->DeoptimizationTarget() : Isolate::kNoDeoptId;
     ASSERT((deopt_target != NULL) ||
-           (use->definition()->GetPropagatedCid() == kDoubleCid));
+           (use->Type()->ToCid() == kDoubleCid));
     ConstantInstr* constant = use->definition()->AsConstant();
     if ((constant != NULL) && constant->value().IsSmi()) {
       const double dbl_val = Smi::Cast(constant->value()).AsDoubleValue();
@@ -313,7 +313,7 @@ void FlowGraphOptimizer::SelectRepresentations() {
       for (intptr_t i = 0; i < join_entry->phis()->length(); ++i) {
         PhiInstr* phi = (*join_entry->phis())[i];
         if (phi == NULL) continue;
-        if (phi->GetPropagatedCid() == kDoubleCid) {
+        if (phi->Type()->ToCid() == kDoubleCid) {
           phi->set_representation(kUnboxedDouble);
         }
       }
@@ -1965,192 +1965,13 @@ void FlowGraphOptimizer::VisitStrictCompare(StrictCompareInstr* instr) {
 
   // If one of the input is not a boxable number (Mint, Double, Bigint), no
   // need for number checks.
-  if (!MayBeBoxableNumber(instr->left()->ResultCid()) ||
-      !MayBeBoxableNumber(instr->right()->ResultCid()))  {
+  if (!MayBeBoxableNumber(instr->left()->Type()->ToCid()) ||
+      !MayBeBoxableNumber(instr->right()->Type()->ToCid()))  {
     instr->set_needs_number_check(false);
   }
 }
 
 
-// SminessPropagator ensures that CheckSmis are eliminated across phis.
-class SminessPropagator : public ValueObject {
- public:
-  explicit SminessPropagator(FlowGraph* flow_graph)
-      : flow_graph_(flow_graph),
-        known_smis_(new BitVector(flow_graph_->current_ssa_temp_index())),
-        rollback_checks_(10),
-        in_worklist_(NULL),
-        worklist_(0) { }
-
-  void Propagate();
-
- private:
-  void PropagateSminessRecursive(BlockEntryInstr* block);
-  void AddToWorklist(PhiInstr* phi);
-  PhiInstr* RemoveLastFromWorklist();
-  void ProcessPhis();
-
-  FlowGraph* flow_graph_;
-
-  BitVector* known_smis_;
-  GrowableArray<intptr_t> rollback_checks_;
-
-  BitVector* in_worklist_;
-  GrowableArray<PhiInstr*> worklist_;
-
-  DISALLOW_COPY_AND_ASSIGN(SminessPropagator);
-};
-
-
-void SminessPropagator::AddToWorklist(PhiInstr* phi) {
-  if (in_worklist_ == NULL) {
-    in_worklist_ = new BitVector(flow_graph_->current_ssa_temp_index());
-  }
-  if (!in_worklist_->Contains(phi->ssa_temp_index())) {
-    in_worklist_->Add(phi->ssa_temp_index());
-    worklist_.Add(phi);
-  }
-}
-
-
-PhiInstr* SminessPropagator::RemoveLastFromWorklist() {
-  PhiInstr* phi = worklist_.RemoveLast();
-  ASSERT(in_worklist_->Contains(phi->ssa_temp_index()));
-  in_worklist_->Remove(phi->ssa_temp_index());
-  return phi;
-}
-
-
-static bool IsDefinitelySmiPhi(PhiInstr* phi) {
-  for (intptr_t i = 0; i < phi->InputCount(); i++) {
-    const intptr_t cid = phi->InputAt(i)->ResultCid();
-    if (cid != kSmiCid) {
-      return false;
-    }
-  }
-  return true;
-}
-
-
-static bool IsPossiblySmiPhi(PhiInstr* phi) {
-  for (intptr_t i = 0; i < phi->InputCount(); i++) {
-    const intptr_t cid = phi->InputAt(i)->ResultCid();
-    if ((cid != kSmiCid) && (cid != kDynamicCid)) {
-      return false;
-    }
-  }
-  return true;
-}
-
-
-void SminessPropagator::ProcessPhis() {
-  // First optimistically mark all possible smi-phis: phi is possibly a smi if
-  // its operands are either smis or phis in the worklist.
-  for (intptr_t i = 0; i < worklist_.length(); i++) {
-    PhiInstr* phi = worklist_[i];
-    ASSERT(phi->GetPropagatedCid() == kDynamicCid);
-    phi->SetPropagatedCid(kSmiCid);
-
-    // Append all phis that use this phi and can potentially be smi to the
-    // end of worklist.
-    for (Value* use = phi->input_use_list();
-         use != NULL;
-         use = use->next_use()) {
-      PhiInstr* phi_use = use->instruction()->AsPhi();
-      if ((phi_use != NULL) &&
-          (phi_use->GetPropagatedCid() == kDynamicCid) &&
-          IsPossiblySmiPhi(phi_use)) {
-        AddToWorklist(phi_use);
-      }
-    }
-  }
-
-  // Now unmark phis that are not definitely smi: that is have only
-  // smi operands.
-  while (!worklist_.is_empty()) {
-    PhiInstr* phi = RemoveLastFromWorklist();
-    if (!IsDefinitelySmiPhi(phi)) {
-      // Phi result is not a smi. Propagate this fact to phis that depend on it.
-      phi->SetPropagatedCid(kDynamicCid);
-      for (Value* use = phi->input_use_list();
-           use != NULL;
-           use = use->next_use()) {
-        PhiInstr* phi_use = use->instruction()->AsPhi();
-        if ((phi_use != NULL) && (phi_use->GetPropagatedCid() == kSmiCid)) {
-          AddToWorklist(phi_use);
-        }
-      }
-    }
-  }
-}
-
-
-void SminessPropagator::PropagateSminessRecursive(BlockEntryInstr* block) {
-  const intptr_t rollback_point = rollback_checks_.length();
-
-  for (ForwardInstructionIterator it(block); !it.Done(); it.Advance()) {
-    Instruction* instr = it.Current();
-    if (instr->IsCheckSmi()) {
-      const intptr_t value_ssa_index =
-          instr->InputAt(0)->definition()->ssa_temp_index();
-      if (!known_smis_->Contains(value_ssa_index)) {
-        known_smis_->Add(value_ssa_index);
-        rollback_checks_.Add(value_ssa_index);
-      }
-    } else if (instr->IsBranch()) {
-      for (intptr_t i = 0; i < instr->InputCount(); i++) {
-        Value* use = instr->InputAt(i);
-        if (known_smis_->Contains(use->definition()->ssa_temp_index())) {
-          use->set_reaching_cid(kSmiCid);
-        }
-      }
-    }
-  }
-
-  for (intptr_t i = 0; i < block->dominated_blocks().length(); ++i) {
-    PropagateSminessRecursive(block->dominated_blocks()[i]);
-  }
-
-  if (block->last_instruction()->SuccessorCount() == 1 &&
-      block->last_instruction()->SuccessorAt(0)->IsJoinEntry()) {
-    JoinEntryInstr* join =
-        block->last_instruction()->SuccessorAt(0)->AsJoinEntry();
-    intptr_t pred_index = join->IndexOfPredecessor(block);
-    ASSERT(pred_index >= 0);
-    if (join->phis() != NULL) {
-      for (intptr_t i = 0; i < join->phis()->length(); ++i) {
-        PhiInstr* phi = (*join->phis())[i];
-        if (phi == NULL) continue;
-        Value* use = phi->InputAt(pred_index);
-        const intptr_t value_ssa_index = use->definition()->ssa_temp_index();
-        if (known_smis_->Contains(value_ssa_index) &&
-            (phi->GetPropagatedCid() != kSmiCid)) {
-          use->set_reaching_cid(kSmiCid);
-          AddToWorklist(phi);
-        }
-      }
-    }
-  }
-
-  for (intptr_t i = rollback_point; i < rollback_checks_.length(); i++) {
-    known_smis_->Remove(rollback_checks_[i]);
-  }
-  rollback_checks_.TruncateTo(rollback_point);
-}
-
-
-void SminessPropagator::Propagate() {
-  PropagateSminessRecursive(flow_graph_->graph_entry());
-  ProcessPhis();
-}
-
-
-void FlowGraphOptimizer::PropagateSminess() {
-  SminessPropagator propagator(flow_graph_);
-  propagator.Propagate();
-}
-
-
 // Range analysis for smi values.
 class RangeAnalysis : public ValueObject {
  public:
@@ -2268,7 +2089,7 @@ void RangeAnalysis::CollectSmiValues() {
       Instruction* current = instr_it.Current();
       Definition* defn = current->AsDefinition();
       if (defn != NULL) {
-        if ((defn->GetPropagatedCid() == kSmiCid) &&
+        if ((defn->Type()->ToCid() == kSmiCid) &&
             (defn->ssa_temp_index() != -1)) {
           smi_values_.Add(defn);
         }
@@ -2281,7 +2102,7 @@ void RangeAnalysis::CollectSmiValues() {
     if (join != NULL) {
       for (PhiIterator phi_it(join); !phi_it.Done(); phi_it.Advance()) {
         PhiInstr* current = phi_it.Current();
-        if (current->GetPropagatedCid() == kSmiCid) {
+        if ((current->Type()->ToCid() == kSmiCid)) {
           smi_values_.Add(current);
         }
       }
@@ -2736,261 +2557,6 @@ void FlowGraphOptimizer::InferSmiRanges() {
 }
 
 
-void FlowGraphTypePropagator::VisitBlocks() {
-  ASSERT(current_iterator_ == NULL);
-  for (intptr_t i = 0; i < block_order_.length(); ++i) {
-    BlockEntryInstr* entry = block_order_[i];
-    entry->Accept(this);
-    ForwardInstructionIterator it(entry);
-    current_iterator_ = &it;
-    for (; !it.Done(); it.Advance()) {
-      Instruction* current = it.Current();
-      // No need to propagate the input types of the instruction, as long as
-      // PhiInstr's are handled as part of JoinEntryInstr.
-
-      // Visit the instruction and possibly eliminate type checks.
-      current->Accept(this);
-      // The instruction may have been removed from the graph.
-      Definition* defn = current->AsDefinition();
-      if ((defn != NULL) &&
-          !defn->IsPushArgument() &&
-          (defn->previous() != NULL)) {
-        // Cache the propagated computation type.
-        AbstractType& type = AbstractType::Handle(defn->CompileType());
-        still_changing_ = defn->SetPropagatedType(type) || still_changing_;
-
-        // Propagate class ids.
-        const intptr_t cid = defn->ResultCid();
-        still_changing_ = defn->SetPropagatedCid(cid) || still_changing_;
-      }
-    }
-    current_iterator_ = NULL;
-  }
-}
-
-
-void FlowGraphTypePropagator::VisitAssertAssignable(
-    AssertAssignableInstr* instr) {
-  bool is_null, is_instance;
-  if (FLAG_eliminate_type_checks &&

[Vyacheslav Egorov (Google), 2013/02/11 17:31:07]

In new approach type propagator only propagates types. It does not remove any
instructions. This is left to the canonicalization pass where it belongs.

-      !instr->is_eliminated() &&
-      ((instr->value()->CanComputeIsNull(&is_null) && is_null) ||
-       (instr->value()->CanComputeIsInstanceOf(instr->dst_type(), &is_instance)
-        && is_instance))) {
-    // TODO(regis): Remove is_eliminated_ field and support.
-    instr->eliminate();
-
-    Value* use = instr->value();
-    ASSERT(use != NULL);
-    Definition* result = use->definition();
-    ASSERT(result != NULL);
-    // Replace uses and remove the current instruction via the iterator.
-    instr->ReplaceUsesWith(result);
-    ASSERT(current_iterator()->Current() == instr);
-    current_iterator()->RemoveCurrentFromGraph();
-    if (FLAG_trace_optimization) {
-      OS::Print("Replacing v%"Pd" with v%"Pd"\n",
-                instr->ssa_temp_index(),
-                result->ssa_temp_index());
-    }
-
-    if (FLAG_trace_type_check_elimination) {
-      FlowGraphPrinter::PrintTypeCheck(parsed_function(),
-                                       instr->token_pos(),
-                                       instr->value(),
-                                       instr->dst_type(),
-                                       instr->dst_name(),
-                                       instr->is_eliminated());
-    }
-  }
-}
-
-
-void FlowGraphTypePropagator::VisitAssertBoolean(AssertBooleanInstr* instr) {
-  bool is_null, is_bool;
-  if (FLAG_eliminate_type_checks &&
-      !instr->is_eliminated() &&
-      instr->value()->CanComputeIsNull(&is_null) &&
-      !is_null &&
-      instr->value()->CanComputeIsInstanceOf(Type::Handle(Type::BoolType()),
-                                             &is_bool) &&
-      is_bool) {
-    // TODO(regis): Remove is_eliminated_ field and support.
-    instr->eliminate();
-    Value* use = instr->value();
-    Definition* result = use->definition();
-    ASSERT(result != NULL);
-    // Replace uses and remove the current instruction via the iterator.
-    instr->ReplaceUsesWith(result);
-    ASSERT(current_iterator()->Current() == instr);
-    current_iterator()->RemoveCurrentFromGraph();
-    if (FLAG_trace_optimization) {
-      OS::Print("Replacing v%"Pd" with v%"Pd"\n",
-                instr->ssa_temp_index(),
-                result->ssa_temp_index());
-    }
-
-    if (FLAG_trace_type_check_elimination) {
-      FlowGraphPrinter::PrintTypeCheck(parsed_function(),
-                                       instr->token_pos(),
-                                       instr->value(),
-                                       Type::Handle(Type::BoolType()),
-                                       Symbols::BooleanExpression(),
-                                       instr->is_eliminated());
-    }
-  }
-}
-
-
-void FlowGraphTypePropagator::VisitInstanceOf(InstanceOfInstr* instr) {
-  bool is_null;
-  bool is_instance = false;
-  if (FLAG_eliminate_type_checks &&
-      instr->value()->CanComputeIsNull(&is_null) &&
-      (is_null ||
-       instr->value()->CanComputeIsInstanceOf(instr->type(), &is_instance))) {
-    bool val = instr->negate_result() ? !is_instance : is_instance;

[Vyacheslav Egorov (Google), 2013/02/11 17:31:07]

I temporary removed any constant folding for instance-of instruction.

This version could actually fold away only (null is Smth) expression so I don't
think we would miss it.

I am going to re-add folding after this change has landed.

-    Definition* result = new ConstantInstr(val ? Bool::True() : Bool::False());
-    result->set_ssa_temp_index(flow_graph_->alloc_ssa_temp_index());
-    result->InsertBefore(instr);
-    // Replace uses and remove the current instruction via the iterator.
-    instr->ReplaceUsesWith(result);
-    ASSERT(current_iterator()->Current() == instr);
-    current_iterator()->RemoveCurrentFromGraph();
-    if (FLAG_trace_optimization) {
-      OS::Print("Replacing v%"Pd" with v%"Pd"\n",
-                instr->ssa_temp_index(),
-                result->ssa_temp_index());
-    }
-
-    if (FLAG_trace_type_check_elimination) {
-      FlowGraphPrinter::PrintTypeCheck(parsed_function(),
-                                       instr->token_pos(),
-                                       instr->value(),
-                                       instr->type(),
-                                       Symbols::InstanceOf(),
-                                       /* eliminated = */ true);
-    }
-  }
-}
-
-
-void FlowGraphTypePropagator::VisitGraphEntry(GraphEntryInstr* graph_entry) {
-  // Visit incoming parameters.
-  for (intptr_t i = 0; i < graph_entry->initial_definitions()->length(); i++) {
-    ParameterInstr* param =
-        (*graph_entry->initial_definitions())[i]->AsParameter();
-    if (param != NULL) VisitParameter(param);
-  }
-}
-
-
-void FlowGraphTypePropagator::VisitJoinEntry(JoinEntryInstr* join_entry) {
-  if (join_entry->phis() != NULL) {
-    for (intptr_t i = 0; i < join_entry->phis()->length(); ++i) {
-      PhiInstr* phi = (*join_entry->phis())[i];
-      if (phi != NULL) {
-        VisitPhi(phi);
-      }
-    }
-  }
-}
-
-
-// TODO(srdjan): Investigate if the propagated cid should be more specific.
-void FlowGraphTypePropagator::VisitPushArgument(PushArgumentInstr* push) {
-  if (!push->has_propagated_cid()) push->SetPropagatedCid(kDynamicCid);
-}
-
-
-void FlowGraphTypePropagator::VisitPhi(PhiInstr* phi) {
-  // We could set the propagated type of the phi to the least upper bound of its
-  // input propagated types. However, keeping all propagated types allows us to
-  // optimize method dispatch.
-  // TODO(regis): Support a set of propagated types. For now, we compute the
-  // least specific of the input propagated types.
-  AbstractType& type = AbstractType::Handle(phi->LeastSpecificInputType());
-  bool changed = phi->SetPropagatedType(type);
-  if (changed) {
-    still_changing_ = true;
-  }
-
-  // Merge class ids: if any two inputs have different class ids then result
-  // is kDynamicCid.
-  intptr_t merged_cid = kIllegalCid;
-  for (intptr_t i = 0; i < phi->InputCount(); i++) {
-    // Result cid of UseVal can be kIllegalCid if the referred definition
-    // has not been visited yet.
-    intptr_t cid = phi->InputAt(i)->ResultCid();
-    if (cid == kIllegalCid) {
-      still_changing_ = true;
-      continue;
-    }
-    if (merged_cid == kIllegalCid) {
-      // First time set.
-      merged_cid = cid;
-    } else if (merged_cid != cid) {
-      merged_cid = kDynamicCid;
-    }
-  }
-  if (merged_cid == kIllegalCid) {
-    merged_cid = kDynamicCid;
-  }
-  changed = phi->SetPropagatedCid(merged_cid);
-  if (changed) {
-    still_changing_ = true;
-  }
-}
-
-
-void FlowGraphTypePropagator::VisitParameter(ParameterInstr* param) {
-  // TODO(regis): Once we inline functions, the propagated type of the formal

[Vyacheslav Egorov (Google), 2013/02/11 17:31:07]

I temporary disabled this code as well (always type check these arguments).

I will return it after this CL lands.

-  // parameter will reflect the compile type of the passed-in argument.
-  // For now, we do not know anything about the argument type and therefore set
-  // it to the DynamicType, unless the argument is a compiler generated value,
-  // i.e. the receiver argument or the constructor phase argument.
-  AbstractType& param_type = AbstractType::Handle(Type::DynamicType());
-  param->SetPropagatedCid(kDynamicCid);
-  bool param_type_is_known = false;
-  if (param->index() == 0) {
-    const Function& function = parsed_function().function();
-    if ((function.IsDynamicFunction() || function.IsConstructor())) {
-      // Parameter is the receiver .
-      param_type_is_known = true;
-    }
-  } else if ((param->index() == 1) &&
-      parsed_function().function().IsConstructor()) {
-    // Parameter is the constructor phase.
-    param_type_is_known = true;
-  }
-  if (param_type_is_known) {
-    LocalScope* scope = parsed_function().node_sequence()->scope();
-    param_type = scope->VariableAt(param->index())->type().raw();
-    if (FLAG_use_cha) {
-      const intptr_t cid = Class::Handle(param_type.type_class()).id();
-      if (!CHA::HasSubclasses(cid)) {
-        // Receiver's class has no subclasses.
-        param->SetPropagatedCid(cid);
-      }
-    }
-  }
-  bool changed = param->SetPropagatedType(param_type);
-  if (changed) {
-    still_changing_ = true;
-  }
-}
-
-
-void FlowGraphTypePropagator::PropagateTypes() {
-  // TODO(regis): Is there a way to make this more efficient, e.g. by visiting
-  // only blocks depending on blocks that have changed and not the whole graph.
-  do {
-    still_changing_ = false;
-    VisitBlocks();
-  } while (still_changing_);
-}
-
-
 static BlockEntryInstr* FindPreHeader(BlockEntryInstr* header) {
   for (intptr_t j = 0; j < header->PredecessorCount(); ++j) {
     BlockEntryInstr* candidate = header->PredecessorAt(j);
@@ -3035,7 +2601,7 @@ void LICM::TryHoistCheckSmiThroughPhi(ForwardInstructionIterator* it,
     return;
   }
 
-  if (phi->GetPropagatedCid() == kSmiCid) {
+  if (phi->Type()->ToCid() == kSmiCid) {
     current->UnuseAllInputs();
     it->RemoveCurrentFromGraph();
     return;
@@ -3047,8 +2613,9 @@ void LICM::TryHoistCheckSmiThroughPhi(ForwardInstructionIterator* it,
   intptr_t non_smi_input = kNotFound;
   for (intptr_t i = 0; i < phi->InputCount(); ++i) {
     Value* input = phi->InputAt(i);
-    if (input->ResultCid() != kSmiCid) {
-      if ((non_smi_input != kNotFound) || (input->ResultCid() != kDynamicCid)) {
+    if (input->Type()->ToCid() != kSmiCid) {
+      if ((non_smi_input != kNotFound) ||
+          (input->Type()->ToCid() != kDynamicCid)) {
         // There are multiple kDynamicCid inputs or there is an input that is
         // known to be non-smi.
         return;
@@ -3072,7 +2639,7 @@ void LICM::TryHoistCheckSmiThroughPhi(ForwardInstructionIterator* it,
   current->value()->set_definition(non_smi_input_defn);
   non_smi_input_defn->AddInputUse(current->value());
 
-  phi->SetPropagatedCid(kSmiCid);
+  phi->Type()->ReplaceWith(CompileType::FromCid(kSmiCid));
 }
 
 
@@ -4118,10 +3685,10 @@ void ConstantPropagator::VisitStrictCompare(StrictCompareInstr* instr) {
 
   if (IsNonConstant(left) || IsNonConstant(right)) {
     // TODO(vegorov): incorporate nullability information into the lattice.
-    if ((left.IsNull() && (instr->right()->ResultCid() != kDynamicCid)) ||
-        (right.IsNull() && (instr->left()->ResultCid() != kDynamicCid))) {
-      bool result = left.IsNull() ? (instr->right()->ResultCid() == kNullCid)
-                                  : (instr->left()->ResultCid() == kNullCid);
+    if ((left.IsNull() && instr->right()->Type()->HasDecidableNullability()) ||
+        (right.IsNull() && instr->left()->Type()->HasDecidableNullability())) {
+      bool result = left.IsNull() ? instr->right()->Type()->IsNull()
+                                  : instr->left()->Type()->IsNull();
       if (instr->kind() == Token::kNE_STRICT) result = !result;
       SetValue(instr, result ? Bool::True() : Bool::False());
     } else {