Disable aggressive optimizations on the last optimization attempt.

src/hydrogen-instructions.h

 // Copyright 2010 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
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 //       disclaimer in the documentation and/or other materials provided
@@ skipping 755 matching lines @@
   int position() const { return position_; }
   bool has_position() const { return position_ != RelocInfo::kNoPosition; }
   void set_position(int position) { position_ = position; }
 
   virtual LInstruction* CompileToLithium(LChunkBuilder* builder) = 0;
 
 #ifdef DEBUG
   virtual void Verify() const;
 #endif
 
+  // Conservative indication of whether the instruction can
+  // deoptimize. Allowed to have false positives.

[Kevin Millikin (Chromium), 2011/01/18 11:18:39]

The comment is also confusing.  The predicate has false negatives (not every
instruction that can deoptimize says true).

[Vitaly Repeshko, 2011/01/18 12:24:56]

I renamed the function and the comment is much clearer now.

+  virtual bool CanDeoptimize() const { return false; }

[fschneider, 2011/01/18 10:45:51]

I'd rather name this predicate IsCheckInstruction() because 
in the long run we want the logic for deciding if an instructions can deoptimize
factored out into a platform-specific part.

[Vitaly Repeshko, 2011/01/18 12:24:56]

Done.

+
   DECLARE_INSTRUCTION(Instruction)
 
  protected:
   HInstruction()
       : next_(NULL),
         previous_(NULL),
         position_(RelocInfo::kNoPosition) {
     SetFlag(kDependsOnOsrEntries);
   }
 
@@ skipping 711 matching lines @@
 
 class HCheckMap: public HUnaryOperation {
  public:
   HCheckMap(HValue* value, Handle<Map> map)
       : HUnaryOperation(value), map_(map) {
     set_representation(Representation::Tagged());
     SetFlag(kUseGVN);
     SetFlag(kDependsOnMaps);
   }
 
+  virtual bool CanDeoptimize() const { return true; }
+
   virtual Representation RequiredInputRepresentation(int index) const {
     return Representation::Tagged();
   }
   virtual void PrintDataTo(StringStream* stream) const;
   virtual HType CalculateInferredType() const;
 
 #ifdef DEBUG
   virtual void Verify() const;
 #endif
 
@@ skipping 13 matching lines @@
 
 
 class HCheckFunction: public HUnaryOperation {
  public:
   HCheckFunction(HValue* value, Handle<JSFunction> function)
       : HUnaryOperation(value), target_(function) {
     set_representation(Representation::Tagged());
     SetFlag(kUseGVN);
   }
 
+  virtual bool CanDeoptimize() const { return true; }
+
   virtual Representation RequiredInputRepresentation(int index) const {
     return Representation::Tagged();
   }
   virtual void PrintDataTo(StringStream* stream) const;
   virtual HType CalculateInferredType() const;
 
 #ifdef DEBUG
   virtual void Verify() const;
 #endif
 
@@ skipping 16 matching lines @@
  public:
   // Check that the instance type is in the range [first, last] where
   // both first and last are included.
   HCheckInstanceType(HValue* value, InstanceType first, InstanceType last)
       : HUnaryOperation(value), first_(first), last_(last) {
     ASSERT(first <= last);
     set_representation(Representation::Tagged());
     SetFlag(kUseGVN);
   }
 
+  virtual bool CanDeoptimize() const { return true; }
+
   virtual Representation RequiredInputRepresentation(int index) const {
     return Representation::Tagged();
   }
 
 #ifdef DEBUG
   virtual void Verify() const;
 #endif
 
   static HCheckInstanceType* NewIsJSObjectOrJSFunction(HValue* value);
 
@@ skipping 17 matching lines @@
 };
 
 
 class HCheckNonSmi: public HUnaryOperation {
  public:
   explicit HCheckNonSmi(HValue* value) : HUnaryOperation(value) {
     set_representation(Representation::Tagged());
     SetFlag(kUseGVN);
   }
 
+  virtual bool CanDeoptimize() const { return true; }
+
   virtual Representation RequiredInputRepresentation(int index) const {
     return Representation::Tagged();
   }
 
   virtual HType CalculateInferredType() const;
 
 #ifdef DEBUG
   virtual void Verify() const;
 #endif
 
   DECLARE_CONCRETE_INSTRUCTION(CheckNonSmi, "check_non_smi")
 };
 
 
 class HCheckPrototypeMaps: public HInstruction {
  public:
   HCheckPrototypeMaps(Handle<JSObject> prototype, Handle<JSObject> holder)
       : prototype_(prototype), holder_(holder) {
     SetFlag(kUseGVN);
     SetFlag(kDependsOnMaps);
   }
 
+  virtual bool CanDeoptimize() const { return true; }
+
 #ifdef DEBUG
   virtual void Verify() const;
 #endif
 
   Handle<JSObject> prototype() const { return prototype_; }
   Handle<JSObject> holder() const { return holder_; }
 
   DECLARE_CONCRETE_INSTRUCTION(CheckPrototypeMaps, "check_prototype_maps")
 
   virtual intptr_t Hashcode() const {
@@ skipping 16 matching lines @@
 };
 
 
 class HCheckSmi: public HUnaryOperation {
  public:
   explicit HCheckSmi(HValue* value) : HUnaryOperation(value) {
     set_representation(Representation::Tagged());
     SetFlag(kUseGVN);
   }
 
+  virtual bool CanDeoptimize() const { return true; }
+
   virtual Representation RequiredInputRepresentation(int index) const {
     return Representation::Tagged();
   }
   virtual HType CalculateInferredType() const;
 
 #ifdef DEBUG
   virtual void Verify() const;
 #endif
 
   DECLARE_CONCRETE_INSTRUCTION(CheckSmi, "check_smi")
@@ skipping 308 matching lines @@
 };
 
 
 class HBoundsCheck: public HBinaryOperation {
  public:
   HBoundsCheck(HValue* index, HValue* length)
       : HBinaryOperation(index, length) {
     SetFlag(kUseGVN);
   }
 
+  virtual bool CanDeoptimize() const { return true; }
+
   virtual Representation RequiredInputRepresentation(int index) const {
     return Representation::Integer32();
   }
 
 #ifdef DEBUG
   virtual void Verify() const;
 #endif
 
   HValue* index() const { return left(); }
   HValue* length() const { return right(); }
@@ skipping 1049 matching lines @@
   HValue* object() const { return left(); }
   HValue* key() const { return right(); }
 };
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_INSTRUCTIONS_H_