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

runtime/vm/intermediate_language.h

Index: runtime/vm/intermediate_language.h
===================================================================
--- runtime/vm/intermediate_language.h	(revision 11671)
+++ runtime/vm/intermediate_language.h	(working copy)
@@ -502,7 +502,7 @@
 
   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:
@@ -540,7 +540,7 @@
 
   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:
@@ -573,7 +573,7 @@
 
   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:
@@ -1235,7 +1235,7 @@
 
   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:
@@ -1301,7 +1301,7 @@
 
   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:
@@ -1475,7 +1475,7 @@
 
   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:
@@ -1605,7 +1605,7 @@
 
   DECLARE_COMPUTATION(CloneContext)
 
-  virtual bool CanDeoptimize() const { return true; }
+  virtual bool CanDeoptimize() const { return false; }
   virtual intptr_t ResultCid() const { return kIllegalCid; }
 
  private:
@@ -1956,7 +1956,7 @@
 
   DECLARE_COMPUTATION(CheckStackOverflow)
 
-  virtual bool CanDeoptimize() const { return true; }
+  virtual bool CanDeoptimize() const { return false; }
   virtual intptr_t ResultCid() const { return kIllegalCid; }
 
  private:
@@ -3065,14 +3065,12 @@
 class ThrowInstr : public TemplateInstruction<0> {
  public:
   explicit ThrowInstr(intptr_t token_pos)
-      : deopt_id_(Isolate::Current()->GetNextDeoptId()),
-        token_pos_(token_pos) { }
+      : token_pos_(token_pos) { }

[regis, 2012/08/31 01:20:41]

one line?

[srdjan, 2012/08/31 15:24:01]

Done.

 
   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;
@@ -3082,7 +3080,6 @@
   virtual bool CanDeoptimize() const { return false; }
 
  private:
-  const intptr_t deopt_id_;
   const intptr_t token_pos_;
 
   DISALLOW_COPY_AND_ASSIGN(ThrowInstr);
@@ -3092,14 +3089,12 @@
 class ReThrowInstr : public TemplateInstruction<0> {
  public:
   explicit ReThrowInstr(intptr_t token_pos)
-      : deopt_id_(Isolate::Current()->GetNextDeoptId()),
-        token_pos_(token_pos) { }
+      : token_pos_(token_pos) { }

[regis, 2012/08/31 01:20:41]

one line?

[srdjan, 2012/08/31 15:24:01]

Done.

 
   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;
@@ -3109,7 +3104,6 @@
   virtual bool CanDeoptimize() const { return false; }
 
  private:
-  const intptr_t deopt_id_;
   const intptr_t token_pos_;
 
   DISALLOW_COPY_AND_ASSIGN(ReThrowInstr);