We can throw an exception but we cannot deoptimize at a runtime call.

runtime/vm/intermediate_language.h

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_INTERMEDIATE_LANGUAGE_H_
 #define VM_INTERMEDIATE_LANGUAGE_H_
 
 #include "vm/allocation.h"
 #include "vm/ast.h"
 #include "vm/growable_array.h"
@@ skipping 484 matching lines @@
   bool is_eliminated() const {
     return is_eliminated_;
   }
   void eliminate() {
     ASSERT(!is_eliminated_);
     is_eliminated_ = true;
   }
 
   virtual void PrintOperandsTo(BufferFormatter* f) const;
 
-  virtual bool CanDeoptimize() const { return true; }
+  virtual bool CanDeoptimize() const { return false; }
   virtual intptr_t ResultCid() const { return kDynamicCid; }
 
  private:
   const intptr_t token_pos_;
   const AbstractType& dst_type_;
   const String& dst_name_;
   bool is_eliminated_;
 
   DISALLOW_COPY_AND_ASSIGN(AssertAssignableComp);
 };
@@ skipping 17 matching lines @@
   bool is_eliminated() const {
     return is_eliminated_;
   }
   void eliminate() {
     ASSERT(!is_eliminated_);
     is_eliminated_ = true;
   }
 
   virtual void PrintOperandsTo(BufferFormatter* f) const;
 
-  virtual bool CanDeoptimize() const { return true; }
+  virtual bool CanDeoptimize() const { return false; }
   virtual intptr_t ResultCid() const { return kBoolCid; }
 
  private:
   const intptr_t token_pos_;
   bool is_eliminated_;
 
   DISALLOW_COPY_AND_ASSIGN(AssertBooleanComp);
 };
 
 
@@ skipping 12 matching lines @@
   intptr_t formal_parameter_index() const {
     return ast_node_.formal_parameter_index();
   }
   const String& formal_parameter_name() const {
     return ast_node_.formal_parameter_name();
   }
   Value* saved_arguments_descriptor() const { return inputs_[0]; }
 
   virtual void PrintOperandsTo(BufferFormatter* f) const;
 
-  virtual bool CanDeoptimize() const { return true; }
+  virtual bool CanDeoptimize() const { return false; }
   virtual intptr_t ResultCid() const { return kBoolCid; }
 
  private:
   const ArgumentDefinitionTestNode& ast_node_;
 
   DISALLOW_COPY_AND_ASSIGN(ArgumentDefinitionTestComp);
 };
 
 
 // Denotes the current context, normally held in a register.  This is
@@ skipping 641 matching lines @@
   Value* value() const { return inputs_[0]; }
   Value* instantiator() const { return inputs_[1]; }
   Value* instantiator_type_arguments() const { return inputs_[2]; }
 
   bool negate_result() const { return negate_result_; }
   const AbstractType& type() const { return type_; }
   intptr_t token_pos() const { return token_pos_; }
 
   virtual void PrintOperandsTo(BufferFormatter* f) const;
 
-  virtual bool CanDeoptimize() const { return true; }
+  virtual bool CanDeoptimize() const { return false; }
   virtual intptr_t ResultCid() const { return kBoolCid; }
 
  private:
   const intptr_t token_pos_;
   Value* value_;
   Value* instantiator_;
   Value* type_arguments_;
   const AbstractType& type_;
   const bool negate_result_;
 
@@ skipping 45 matching lines @@
     inputs_[1] = instantiator;
   }
 
   DECLARE_COMPUTATION(AllocateObjectWithBoundsCheck)
 
   const Function& constructor() const { return ast_node_.constructor(); }
   intptr_t token_pos() const { return ast_node_.token_pos(); }
 
   virtual void PrintOperandsTo(BufferFormatter* f) const;
 
-  virtual bool CanDeoptimize() const { return true; }
+  virtual bool CanDeoptimize() const { return false; }
   virtual intptr_t ResultCid() const { return kDynamicCid; }
 
  private:
   const ConstructorCallNode& ast_node_;
 
   DISALLOW_COPY_AND_ASSIGN(AllocateObjectWithBoundsCheckComp);
 };
 
 
 class CreateArrayComp : public TemplateComputation<1> {
@@ skipping 153 matching lines @@
   DECLARE_COMPUTATION(InstantiateTypeArguments)
 
   Value* instantiator() const { return inputs_[0]; }
   const AbstractTypeArguments& type_arguments() const {
     return type_arguments_;
   }
   intptr_t token_pos() const { return token_pos_; }
 
   virtual void PrintOperandsTo(BufferFormatter* f) const;
 
-  virtual bool CanDeoptimize() const { return true; }
+  virtual bool CanDeoptimize() const { return false; }
   virtual intptr_t ResultCid() const { return kDynamicCid; }
 
  private:
   const intptr_t token_pos_;
   const AbstractTypeArguments& type_arguments_;
 
   DISALLOW_COPY_AND_ASSIGN(InstantiateTypeArgumentsComp);
 };
 
 
@@ skipping 109 matching lines @@
       : token_pos_(token_pos) {
     ASSERT(context_value != NULL);
     inputs_[0] = context_value;
   }
 
   intptr_t token_pos() const { return token_pos_; }
   Value* context_value() const { return inputs_[0]; }
 
   DECLARE_COMPUTATION(CloneContext)
 
-  virtual bool CanDeoptimize() const { return true; }
+  virtual bool CanDeoptimize() const { return false; }
   virtual intptr_t ResultCid() const { return kIllegalCid; }
 
  private:
   const intptr_t token_pos_;
 
   DISALLOW_COPY_AND_ASSIGN(CloneContextComp);
 };
 
 
 class CatchEntryComp : public TemplateComputation<0> {
@@ skipping 330 matching lines @@
 
 class CheckStackOverflowComp : public TemplateComputation<0> {
  public:
   explicit CheckStackOverflowComp(intptr_t token_pos)
       : token_pos_(token_pos) {}
 
   intptr_t token_pos() const { return token_pos_; }
 
   DECLARE_COMPUTATION(CheckStackOverflow)
 
-  virtual bool CanDeoptimize() const { return true; }
+  virtual bool CanDeoptimize() const { return false; }
   virtual intptr_t ResultCid() const { return kIllegalCid; }
 
  private:
   const intptr_t token_pos_;
 
   DISALLOW_COPY_AND_ASSIGN(CheckStackOverflowComp);
 };
 
 
 class DoubleToDoubleComp : public TemplateComputation<1> {
@@ skipping 1087 matching lines @@
  private:
   const intptr_t deopt_id_;
   const intptr_t token_pos_;
 
   DISALLOW_COPY_AND_ASSIGN(ReturnInstr);
 };
 
 
 class ThrowInstr : public TemplateInstruction<0> {
  public:
-  explicit ThrowInstr(intptr_t token_pos)
-      : deopt_id_(Isolate::Current()->GetNextDeoptId()),
-        token_pos_(token_pos) { }
+  explicit ThrowInstr(intptr_t token_pos) : token_pos_(token_pos) { }
 
   DECLARE_INSTRUCTION(Throw)
 
   virtual intptr_t ArgumentCount() const { return 1; }
 
-  intptr_t deopt_id() const { return deopt_id_; }
   intptr_t token_pos() const { return token_pos_; }
 
   virtual LocationSummary* MakeLocationSummary() const;
 
   virtual void EmitNativeCode(FlowGraphCompiler* compiler);
 
   virtual bool CanDeoptimize() const { return false; }
 
  private:
-  const intptr_t deopt_id_;
   const intptr_t token_pos_;
 
   DISALLOW_COPY_AND_ASSIGN(ThrowInstr);
 };
 
 
 class ReThrowInstr : public TemplateInstruction<0> {
  public:
-  explicit ReThrowInstr(intptr_t token_pos)
-      : deopt_id_(Isolate::Current()->GetNextDeoptId()),
-        token_pos_(token_pos) { }
+  explicit ReThrowInstr(intptr_t token_pos) : token_pos_(token_pos) { }
 
   DECLARE_INSTRUCTION(ReThrow)
 
   virtual intptr_t ArgumentCount() const { return 2; }
 
-  intptr_t deopt_id() const { return deopt_id_; }
   intptr_t token_pos() const { return token_pos_; }
 
   virtual LocationSummary* MakeLocationSummary() const;
 
   virtual void EmitNativeCode(FlowGraphCompiler* compiler);
 
   virtual bool CanDeoptimize() const { return false; }
 
  private:
-  const intptr_t deopt_id_;
   const intptr_t token_pos_;
 
   DISALLOW_COPY_AND_ASSIGN(ReThrowInstr);
 };
 
 
 class GotoInstr : public TemplateInstruction<0> {
  public:
   explicit GotoInstr(JoinEntryInstr* entry)
     : successor_(entry),
@@ skipping 214 matching lines @@
   ForwardInstructionIterator* current_iterator_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(FlowGraphVisitor);
 };
 
 
 }  // namespace dart
 
 #endif  // VM_INTERMEDIATE_LANGUAGE_H_