Lattice-based representation inference, powered by left/right specific type feedback for BinaryOps …

src/hydrogen-instructions.h

 // Copyright 2012 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
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 27 matching lines @@
 #include "v8conversions.h"
 #include "v8utils.h"
 #include "zone.h"
 
 namespace v8 {
 namespace internal {
 
 // Forward declarations.
 class HBasicBlock;
 class HEnvironment;
+class HInferRepresentation;
 class HInstruction;
 class HLoopInformation;
 class HValue;
 class LInstruction;
 class LChunkBuilder;
 
 
 #define HYDROGEN_ABSTRACT_INSTRUCTION_LIST(V)  \
   V(BinaryOperation)                           \
   V(BitwiseBinaryOperation)                    \
@@ skipping 242 matching lines @@
   int32_t upper_;
   Range* next_;
   bool can_be_minus_zero_;
 };
 
 
 class Representation {
  public:
   enum Kind {
     kNone,
+    kInteger32,
+    kDouble,
     kTagged,
-    kDouble,
-    kInteger32,
     kExternal,
     kNumRepresentations
   };
 
   Representation() : kind_(kNone) { }
 
   static Representation None() { return Representation(kNone); }
   static Representation Tagged() { return Representation(kTagged); }
   static Representation Integer32() { return Representation(kInteger32); }
   static Representation Double() { return Representation(kDouble); }
   static Representation External() { return Representation(kExternal); }
 
   bool Equals(const Representation& other) {
     return kind_ == other.kind_;
   }
 
+  bool is_more_general_than(const Representation& other) {
+    ASSERT(kind_ != kExternal);
+    ASSERT(other.kind_ != kExternal);
+    return kind_ > other.kind_;
+  }
+
   Kind kind() const { return static_cast<Kind>(kind_); }
   bool IsNone() const { return kind_ == kNone; }
   bool IsTagged() const { return kind_ == kTagged; }
   bool IsInteger32() const { return kind_ == kInteger32; }
   bool IsDouble() const { return kind_ == kDouble; }
   bool IsExternal() const { return kind_ == kExternal; }
   bool IsSpecialization() const {
     return kind_ == kInteger32 || kind_ == kDouble;
   }
   const char* Mnemonic() const;
@@ skipping 282 matching lines @@
   int LoopWeight() const;
 
   int id() const { return id_; }
   void set_id(int id) { id_ = id; }
 
   HUseIterator uses() const { return HUseIterator(use_list_); }
 
   virtual bool EmitAtUses() { return false; }
   Representation representation() const { return representation_; }
   void ChangeRepresentation(Representation r) {
-    // Representation was already set and is allowed to be changed.
-    ASSERT(!r.IsNone());
     ASSERT(CheckFlag(kFlexibleRepresentation));
     RepresentationChanged(r);
     representation_ = r;
+    if (r.IsTagged()) {
+      // Tagged is the bottom of the lattice, don't go any further.
+      ClearFlag(kFlexibleRepresentation);
+    }
   }
-  void AssumeRepresentation(Representation r);
+  virtual void AssumeRepresentation(Representation r);
 
   virtual bool IsConvertibleToInteger() const { return true; }
 
   HType type() const { return type_; }
   void set_type(HType new_type) {
     ASSERT(new_type.IsSubtypeOf(type_));
     type_ = new_type;
   }
 
   // An operation needs to override this function iff:
@@ skipping 77 matching lines @@
     return result;
   }
 
   Range* range() const { return range_; }
   bool HasRange() const { return range_ != NULL; }
   void AddNewRange(Range* r, Zone* zone);
   void RemoveLastAddedRange();
   void ComputeInitialRange(Zone* zone);
 
   // Representation helpers.
+  virtual Representation observed_input_representation(int index) {
+    return Representation::None();
+  }
   virtual Representation RequiredInputRepresentation(int index) = 0;
-
-  virtual Representation InferredRepresentation() {
-    return representation();
-  }
-
-  // Type feedback access.
-  virtual Representation ObservedInputRepresentation(int index) {
-    return RequiredInputRepresentation(index);
-  }
+  virtual void InferRepresentation(HInferRepresentation* h_infer);
 
   // This gives the instruction an opportunity to replace itself with an
   // instruction that does the same in some better way.  To replace an
   // instruction with a new one, first add the new instruction to the graph,
   // then return it.  Return NULL to have the instruction deleted.
   virtual HValue* Canonicalize() { return this; }
 
   bool Equals(HValue* other);
   virtual intptr_t Hashcode();
 
@@ skipping 27 matching lines @@
   virtual void Verify() = 0;
 #endif
 
  protected:
   // This function must be overridden for instructions with flag kUseGVN, to
   // compare the non-Operand parts of the instruction.
   virtual bool DataEquals(HValue* other) {
     UNREACHABLE();
     return false;
   }
+
+  virtual Representation RepresentationFromInputs() {
+    return representation();
+  }
+  Representation RepresentationFromUses();
+  virtual void UpdateRepresentation(Representation new_rep,
+                                    HInferRepresentation* h_infer,
+                                    const char* reason);
+  void AddDependantsToWorklist(HInferRepresentation* h_infer);
+
   virtual void RepresentationChanged(Representation to) { }
+
   virtual Range* InferRange(Zone* zone);
   virtual void DeleteFromGraph() = 0;
   virtual void InternalSetOperandAt(int index, HValue* value) = 0;
   void clear_block() {
     ASSERT(block_ != NULL);
     block_ = NULL;
   }
 
   void set_representation(Representation r) {
-    // Representation is set-once.
     ASSERT(representation_.IsNone() && !r.IsNone());
     representation_ = r;
   }
 
   static GVNFlagSet AllDependsOnFlagSet() {
     GVNFlagSet result;
     // Create changes mask.
 #define ADD_FLAG(type) result.Add(kDependsOn##type);
   GVN_TRACKED_FLAG_LIST(ADD_FLAG)
   GVN_UNTRACKED_FLAG_LIST(ADD_FLAG)
@@ skipping 292 matching lines @@
         expected_input_types_(expected_input_types) {
     ASSERT(true_target != NULL && false_target != NULL);
   }
   explicit HBranch(HValue* value)
       : HUnaryControlInstruction(value, NULL, NULL) { }
 
 
   virtual Representation RequiredInputRepresentation(int index) {
     return Representation::None();
   }
+  virtual Representation observed_input_representation(int index);
 
   ToBooleanStub::Types expected_input_types() const {
     return expected_input_types_;
   }
 
   DECLARE_CONCRETE_INSTRUCTION(Branch)
 
  private:
   ToBooleanStub::Types expected_input_types_;
 };
@@ skipping 184 matching lines @@
   DECLARE_CONCRETE_INSTRUCTION(ClampToUint8)
 
  protected:
   virtual bool DataEquals(HValue* other) { return true; }
 
  private:
   virtual bool IsDeletable() const { return true; }
 };
 
 
+enum RemovableSimulate {
+  REMOVABLE,

[danno, 2012/11/14 10:38:22]

make this REMOVABLE_SIMULATE?

[Jakob Kummerow, 2012/11/14 15:53:23]

Done.

+  FIXED
+};
+
+
 class HSimulate: public HInstruction {
  public:
-  HSimulate(BailoutId ast_id, int pop_count, Zone* zone)
+  HSimulate(BailoutId ast_id,
+            int pop_count,
+            Zone* zone,
+            RemovableSimulate removable)
       : ast_id_(ast_id),
         pop_count_(pop_count),
         values_(2, zone),
         assigned_indexes_(2, zone),
-        zone_(zone) {}
+        zone_(zone),
+        removable_(removable) {}
   virtual ~HSimulate() {}
 
   virtual void PrintDataTo(StringStream* stream);
 
   bool HasAstId() const { return !ast_id_.IsNone(); }
   BailoutId ast_id() const { return ast_id_; }
   void set_ast_id(BailoutId id) {
     ASSERT(!HasAstId());
     ast_id_ = id;
   }
@@ skipping 13 matching lines @@
   void AddPushedValue(HValue* value) {
     AddValue(kNoIndex, value);
   }
   virtual int OperandCount() { return values_.length(); }
   virtual HValue* OperandAt(int index) const { return values_[index]; }
 
   virtual Representation RequiredInputRepresentation(int index) {
     return Representation::None();
   }
 
+  void MergeInto(HSimulate* other);
+  bool is_candidate_for_removal() { return removable_ == REMOVABLE; }
+
   DECLARE_CONCRETE_INSTRUCTION(Simulate)
 
 #ifdef DEBUG
   virtual void Verify();
 #endif
 
  protected:
   virtual void InternalSetOperandAt(int index, HValue* value) {
     values_[index] = value;
   }
 
  private:
   static const int kNoIndex = -1;
   void AddValue(int index, HValue* value) {
     assigned_indexes_.Add(index, zone_);
     // Resize the list of pushed values.
     values_.Add(NULL, zone_);
     // Set the operand through the base method in HValue to make sure that the
     // use lists are correctly updated.
     SetOperandAt(values_.length() - 1, value);
   }
   BailoutId ast_id_;
   int pop_count_;
   ZoneList<HValue*> values_;
   ZoneList<int> assigned_indexes_;
   Zone* zone_;
+  RemovableSimulate removable_;
 };
 
 
 class HStackCheck: public HTemplateInstruction<1> {
  public:
   enum Type {
     kFunctionEntry,
     kBackwardsBranch
   };
 
@@ skipping 606 matching lines @@
  public:
   explicit HBitNot(HValue* value) : HUnaryOperation(value) {
     set_representation(Representation::Integer32());
     SetFlag(kUseGVN);
     SetFlag(kTruncatingToInt32);
   }
 
   virtual Representation RequiredInputRepresentation(int index) {
     return Representation::Integer32();
   }
+  virtual Representation observed_input_representation(int index) {
+    return Representation::Integer32();
+  }
   virtual HType CalculateInferredType();
 
   virtual HValue* Canonicalize();
 
   DECLARE_CONCRETE_INSTRUCTION(BitNot)
 
  protected:
   virtual bool DataEquals(HValue* other) { return true; }
 
  private:
   virtual bool IsDeletable() const { return true; }
 };
 
 
 class HUnaryMathOperation: public HTemplateInstruction<2> {
  public:
   HUnaryMathOperation(HValue* context, HValue* value, BuiltinFunctionId op)
       : op_(op) {
     SetOperandAt(0, context);
     SetOperandAt(1, value);
     switch (op) {
       case kMathFloor:
       case kMathRound:
       case kMathCeil:
         set_representation(Representation::Integer32());
         break;
       case kMathAbs:
-        set_representation(Representation::Tagged());
+        // Not setting representation here: it is None intentionally.
         SetFlag(kFlexibleRepresentation);
         SetGVNFlag(kChangesNewSpacePromotion);
         break;
       case kMathSqrt:
       case kMathPowHalf:
       case kMathLog:
       case kMathSin:
       case kMathCos:
       case kMathTan:
         set_representation(Representation::Double());
@@ skipping 159 matching lines @@
         map_set->Add(Handle<Map>(transitioned_map), zone);
       }
     };
     map_set->Sort();
     return check_map;
   }
 
   virtual Representation RequiredInputRepresentation(int index) {
     return Representation::Tagged();
   }
+
   virtual void PrintDataTo(StringStream* stream);
   virtual HType CalculateInferredType();
 
   HValue* value() { return OperandAt(0); }
   SmallMapList* map_set() { return &map_set_; }
 
   DECLARE_CONCRETE_INSTRUCTION(CheckMaps)
 
  protected:
   virtual bool DataEquals(HValue* other) {
@@ skipping 207 matching lines @@
       : inputs_(2, zone),
         merged_index_(merged_index),
         phi_id_(-1),
         is_live_(false),
         is_convertible_to_integer_(true) {
     for (int i = 0; i < Representation::kNumRepresentations; i++) {
       non_phi_uses_[i] = 0;
       indirect_uses_[i] = 0;
     }
     ASSERT(merged_index >= 0);
-    set_representation(Representation::Tagged());
     SetFlag(kFlexibleRepresentation);
   }
 
-  virtual Representation InferredRepresentation();
+  virtual Representation RepresentationFromInputs();
 
   virtual Range* InferRange(Zone* zone);
+  virtual void InferRepresentation(HInferRepresentation* h_infer);
+  Representation RepresentationFromUseRequirements();
   virtual Representation RequiredInputRepresentation(int index) {
     return representation();
   }
   virtual HType CalculateInferredType();
   virtual int OperandCount() { return inputs_.length(); }
   virtual HValue* OperandAt(int index) const { return inputs_[index]; }
   HValue* GetRedundantReplacement();
   void AddInput(HValue* value);
   bool HasRealUses();
 
@@ skipping 43 matching lines @@
     return is_convertible_to_integer_;
   }
 
   void set_is_convertible_to_integer(bool b) {
     is_convertible_to_integer_ = b;
   }
 
   bool AllOperandsConvertibleToInteger() {
     for (int i = 0; i < OperandCount(); ++i) {
       if (!OperandAt(i)->IsConvertibleToInteger()) {
+        if (FLAG_trace_representation) {
+          HValue* input = OperandAt(i);
+          PrintF("#%d %s: Input #%d %s at %d is NCTI\n",
+                 id(), Mnemonic(), input->id(), input->Mnemonic(), i);
+        }
         return false;
       }
     }
     return true;
   }
 
-  void ResetInteger32Uses();
-
  protected:
   virtual void DeleteFromGraph();
   virtual void InternalSetOperandAt(int index, HValue* value) {
     inputs_[index] = value;
   }
 
  private:
   ZoneList<HValue*> inputs_;
   int merged_index_;
 
@@ skipping 163 matching lines @@
   // not the converse.
   bool has_int32_value_ : 1;
   bool has_double_value_ : 1;
   int32_t int32_value_;
   double double_value_;
 };
 
 
 class HBinaryOperation: public HTemplateInstruction<3> {
  public:
-  HBinaryOperation(HValue* context, HValue* left, HValue* right) {
+  HBinaryOperation(HValue* context, HValue* left, HValue* right)
+      : observed_output_representation_(Representation::None()) {
     ASSERT(left != NULL && right != NULL);
     SetOperandAt(0, context);
     SetOperandAt(1, left);
     SetOperandAt(2, right);
+    observed_input_representation_[0] = Representation::None();
+    observed_input_representation_[1] = Representation::None();
   }
 
   HValue* context() { return OperandAt(0); }
   HValue* left() { return OperandAt(1); }
   HValue* right() { return OperandAt(2); }
 
   // TODO(kasperl): Move these helpers to the IA-32 Lithium
   // instruction sequence builder.
   HValue* LeastConstantOperand() {
     if (IsCommutative() && left()->IsConstant()) return right();
     return left();
   }
 
   HValue* MostConstantOperand() {
     if (IsCommutative() && left()->IsConstant()) return left();
     return right();
   }
 
+  void set_observed_input_representation(Representation left,
+                                         Representation right) {
+    observed_input_representation_[0] = left;
+    observed_input_representation_[1] = right;
+  }
+
+  virtual void initialize_output_representation(Representation observed) {
+    observed_output_representation_ = observed;
+  }
+
+  virtual Representation observed_input_representation(int index) {
+    if (index == 0) return Representation::Tagged();
+    return observed_input_representation_[index - 1];
+  }
+
+  virtual Representation RepresentationFromInputs();
+  virtual void AssumeRepresentation(Representation r);
+
   virtual bool IsCommutative() const { return false; }
 
   virtual void PrintDataTo(StringStream* stream);
 
   DECLARE_ABSTRACT_INSTRUCTION(BinaryOperation)
+
+ private:
+  Representation observed_input_representation_[2];
+  Representation observed_output_representation_;
 };
 
 
 class HWrapReceiver: public HTemplateInstruction<2> {
  public:
   HWrapReceiver(HValue* receiver, HValue* function) {
     set_representation(Representation::Tagged());
     SetOperandAt(0, receiver);
     SetOperandAt(1, function);
   }
@@ skipping 149 matching lines @@
     }
     // Also allow the length to be tagged if the index is constant, because
     // it can be tagged to allow direct comparison.
     if (index()->IsConstant() &&
         index()->representation().IsInteger32() &&
         arg_index == 1) {
       return Representation::Tagged();
     }
     return Representation::Integer32();
   }
+  virtual Representation observed_input_representation(int index) {
+    return Representation::Integer32();
+  }
 
   virtual void PrintDataTo(StringStream* stream);
 
   HValue* index() { return OperandAt(0); }
   HValue* length() { return OperandAt(1); }
 
   DECLARE_CONCRETE_INSTRUCTION(BoundsCheck)
 
  protected:
   virtual bool DataEquals(HValue* other) { return true; }
   BoundsCheckKeyMode key_mode_;
 };
 
 
 class HBitwiseBinaryOperation: public HBinaryOperation {
  public:
   HBitwiseBinaryOperation(HValue* context, HValue* left, HValue* right)
       : HBinaryOperation(context, left, right) {
-    set_representation(Representation::Tagged());
     SetFlag(kFlexibleRepresentation);
+    SetFlag(kTruncatingToInt32);
     SetAllSideEffects();
-    observed_input_representation_[0] = Representation::Tagged();
-    observed_input_representation_[1] = Representation::None();
-    observed_input_representation_[2] = Representation::None();
   }
 
   virtual Representation RequiredInputRepresentation(int index) {
     return index == 0
         ? Representation::Tagged()
         : representation();
   }
 
   virtual void RepresentationChanged(Representation to) {
     if (!to.IsTagged()) {
       ASSERT(to.IsInteger32());
       ClearAllSideEffects();
-      SetFlag(kTruncatingToInt32);
       SetFlag(kUseGVN);
+    } else {
+      SetAllSideEffects();
+      ClearFlag(kUseGVN);
     }
   }
 
-  virtual HType CalculateInferredType();
-
-  virtual Representation ObservedInputRepresentation(int index) {
-    return observed_input_representation_[index];
+  virtual void UpdateRepresentation(Representation new_rep,
+                                    HInferRepresentation* h_infer,
+                                    const char* reason) {
+    // We only generate either int32 or generic tagged bitwise operations.
+    if (new_rep.IsDouble()) new_rep = Representation::Integer32();
+    HValue::UpdateRepresentation(new_rep, h_infer, reason);
   }
 
-  void InitializeObservedInputRepresentation(Representation r) {
-    observed_input_representation_[1] = r;
-    observed_input_representation_[2] = r;
+  virtual void initialize_output_representation(Representation observed) {
+    if (observed.IsDouble()) observed = Representation::Integer32();
+    HBinaryOperation::initialize_output_representation(observed);
   }
 
+  virtual HType CalculateInferredType();
+
   DECLARE_ABSTRACT_INSTRUCTION(BitwiseBinaryOperation)
 
  private:
   virtual bool IsDeletable() const { return true; }
-
-  Representation observed_input_representation_[3];
 };
 
 
 class HMathFloorOfDiv: public HBinaryOperation {
  public:
   HMathFloorOfDiv(HValue* context, HValue* left, HValue* right)
       : HBinaryOperation(context, left, right) {
     set_representation(Representation::Integer32());
     SetFlag(kUseGVN);
     SetFlag(kCanOverflow);
@@ skipping 12 matching lines @@
 
  private:
   virtual bool IsDeletable() const { return true; }
 };
 
 
 class HArithmeticBinaryOperation: public HBinaryOperation {
  public:
   HArithmeticBinaryOperation(HValue* context, HValue* left, HValue* right)
       : HBinaryOperation(context, left, right) {
-    set_representation(Representation::Tagged());
+    SetAllSideEffects();
     SetFlag(kFlexibleRepresentation);
-    SetAllSideEffects();
   }
 
   virtual void RepresentationChanged(Representation to) {
-    if (!to.IsTagged()) {
+    if (to.IsTagged()) {
+      SetAllSideEffects();
+      ClearFlag(kUseGVN);
+    } else {
       ClearAllSideEffects();
       SetFlag(kUseGVN);
     }
   }
 
   virtual HType CalculateInferredType();
   virtual Representation RequiredInputRepresentation(int index) {
     return index == 0
         ? Representation::Tagged()
         : representation();
   }
 
-  virtual Representation InferredRepresentation() {
-    if (left()->representation().Equals(right()->representation())) {
-      return left()->representation();
-    }
-    return HValue::InferredRepresentation();
-  }
-
  private:
   virtual bool IsDeletable() const { return true; }
 };
 
 
 class HCompareGeneric: public HBinaryOperation {
  public:
   HCompareGeneric(HValue* context,
                   HValue* left,
                   HValue* right,
                   Token::Value token)
       : HBinaryOperation(context, left, right), token_(token) {
     ASSERT(Token::IsCompareOp(token));
     set_representation(Representation::Tagged());
     SetAllSideEffects();
   }
 
   virtual Representation RequiredInputRepresentation(int index) {
-    return Representation::Tagged();
-  }
-
-  Representation GetInputRepresentation() const {
-    return Representation::Tagged();
+    return index == 0
+        ? Representation::Tagged()
+        : representation();
   }
 
   Token::Value token() const { return token_; }
   virtual void PrintDataTo(StringStream* stream);
 
   virtual HType CalculateInferredType();
 
   DECLARE_CONCRETE_INSTRUCTION(CompareGeneric)
 
  private:
   Token::Value token_;
 };
 
 
 class HCompareIDAndBranch: public HTemplateControlInstruction<2, 2> {
  public:
   HCompareIDAndBranch(HValue* left, HValue* right, Token::Value token)
       : token_(token) {
+    SetFlag(kFlexibleRepresentation);
     ASSERT(Token::IsCompareOp(token));
     SetOperandAt(0, left);
     SetOperandAt(1, right);
   }
 
   HValue* left() { return OperandAt(0); }
   HValue* right() { return OperandAt(1); }
   Token::Value token() const { return token_; }
 
-  void SetInputRepresentation(Representation r);
-  Representation GetInputRepresentation() const {
-    return input_representation_;
+  void set_observed_input_representation(Representation left,
+                                         Representation right) {
+      observed_input_representation_[0] = left;
+      observed_input_representation_[1] = right;
   }
 
+  virtual void InferRepresentation(HInferRepresentation* h_infer);
+
   virtual Representation RequiredInputRepresentation(int index) {
-    return input_representation_;
+    return representation();
+  }
+  virtual Representation observed_input_representation(int index) {
+    return observed_input_representation_[index];
   }
   virtual void PrintDataTo(StringStream* stream);
 
   DECLARE_CONCRETE_INSTRUCTION(CompareIDAndBranch)
 
  private:
-  Representation input_representation_;
+  Representation observed_input_representation_[2];
   Token::Value token_;
 };
 
 
 class HCompareObjectEqAndBranch: public HTemplateControlInstruction<2, 2> {
  public:
   HCompareObjectEqAndBranch(HValue* left, HValue* right) {
     SetOperandAt(0, left);
     SetOperandAt(1, right);
   }
@@ skipping 40 matching lines @@
       : HUnaryControlInstruction(value, NULL, NULL), kind_(kind), nil_(nil) { }
 
   EqualityKind kind() const { return kind_; }
   NilValue nil() const { return nil_; }
 
   virtual void PrintDataTo(StringStream* stream);
 
   virtual Representation RequiredInputRepresentation(int index) {
     return Representation::Tagged();
   }
+  virtual Representation observed_input_representation(int index) {
+    return Representation::Tagged();
+  }
 
   DECLARE_CONCRETE_INSTRUCTION(IsNilAndBranch)
 
  private:
   EqualityKind kind_;
   NilValue nil_;
 };
 
 
 class HIsObjectAndBranch: public HUnaryControlInstruction {
@@ skipping 257 matching lines @@
   }
 
   HValue* left() { return OperandAt(0); }
   HValue* right() const { return OperandAt(1); }
 
   virtual Representation RequiredInputRepresentation(int index) {
     return index == 0
       ? Representation::Double()
       : Representation::None();
   }
+  virtual Representation observed_input_representation(int index) {
+    return RequiredInputRepresentation(index);
+  }
 
   DECLARE_CONCRETE_INSTRUCTION(Power)
 
  protected:
   virtual bool DataEquals(HValue* other) { return true; }
 
  private:
   virtual bool IsDeletable() const {
     return !right()->representation().IsTagged();
   }
@@ skipping 165 matching lines @@
 
 class HMathMinMax: public HArithmeticBinaryOperation {
  public:
   enum Operation { kMathMin, kMathMax };
 
   HMathMinMax(HValue* context, HValue* left, HValue* right, Operation op)
       : HArithmeticBinaryOperation(context, left, right),
         operation_(op) { }
 
   virtual Representation RequiredInputRepresentation(int index) {
-      return index == 0
-          ? Representation::Tagged()
-          : representation();
-    }
+    return index == 0 ? Representation::Tagged()
+                      : representation();
+  }
 
-  virtual Representation InferredRepresentation() {
-    if (left()->representation().IsInteger32() &&
-        right()->representation().IsInteger32()) {
+  virtual Representation observed_input_representation(int index) {
+    return RequiredInputRepresentation(index);
+  }
+
+  virtual Representation RepresentationFromInputs() {
+    Representation left_rep = left()->representation();
+    Representation right_rep = right()->representation();
+    if ((left_rep.IsNone() || left_rep.IsInteger32()) &&
+        (right_rep.IsNone() || right_rep.IsInteger32())) {
       return Representation::Integer32();
     }
     return Representation::Double();
   }
 
   virtual bool IsCommutative() const { return true; }
 
   Operation operation() { return operation_; }
 
   DECLARE_CONCRETE_INSTRUCTION(MathMinMax)
@@ skipping 686 matching lines @@
     // kind_double:     tagged[int32] (none)
     // kind_external: external[int32] (none)
     if (index == 0) {
       return is_external() ? Representation::External()
           : Representation::Tagged();
     }
     if (index == 1) return Representation::Integer32();
     return Representation::None();
   }
 
+  virtual Representation observed_input_representation(int index) {
+    return RequiredInputRepresentation(index);
+  }
+
   virtual void PrintDataTo(StringStream* stream);
 
   bool RequiresHoleCheck() const;
 
   virtual Range* InferRange(Zone* zone);
 
   DECLARE_CONCRETE_INSTRUCTION(LoadKeyed)
 
  protected:
   virtual bool DataEquals(HValue* other) {
@@ skipping 171 matching lines @@
     SetOperandAt(2, val);
 
     if (is_external()) {
       SetGVNFlag(kChangesSpecializedArrayElements);
     } else if (IsFastDoubleElementsKind(elements_kind)) {
       SetGVNFlag(kChangesDoubleArrayElements);
       SetFlag(kDeoptimizeOnUndefined);
     } else {
       SetGVNFlag(kChangesArrayElements);
     }
+
+    // EXTERNAL_{UNSIGNED_,}{BYTE,SHORT,INT}_ELEMENTS are truncating.
+    if (elements_kind >= EXTERNAL_BYTE_ELEMENTS &&
+        elements_kind <= EXTERNAL_UNSIGNED_INT_ELEMENTS) {
+      SetFlag(kTruncatingToInt32);
+    }
   }
 
   virtual Representation RequiredInputRepresentation(int index) {
     // kind_fast:       tagged[int32] = tagged
     // kind_double:     tagged[int32] = double
     // kind_external: external[int32] = (double | int32)
     if (index == 0) {
       return is_external() ? Representation::External()
                            : Representation::Tagged();
     } else if (index == 1) {
       return Representation::Integer32();
     }
 
     ASSERT_EQ(index, 2);
     if (IsDoubleOrFloatElementsKind(elements_kind())) {
       return Representation::Double();
     }
 
     return is_external() ? Representation::Integer32()
                          : Representation::Tagged();
   }
 
   bool is_external() const {
     return IsExternalArrayElementsKind(elements_kind());
   }
+
+  virtual Representation observed_input_representation(int index) {
+    if (index < 2) return RequiredInputRepresentation(index);
+    if (IsDoubleOrFloatElementsKind(elements_kind())) {
+      return Representation::Double();
+    }
+    if (is_external()) {
+      return Representation::Integer32();
+    }
+    // For fast object elements kinds, don't assume anything.
+    return Representation::None();
+  }
+
   HValue* elements() { return OperandAt(0); }
   HValue* key() { return OperandAt(1); }
   HValue* value() { return OperandAt(2); }
   bool value_is_smi() const {
     return IsFastSmiElementsKind(elements_kind_);
   }
   ElementsKind elements_kind() const { return elements_kind_; }
   uint32_t index_offset() { return index_offset_; }
   void SetIndexOffset(uint32_t index_offset) { index_offset_ = index_offset; }
   HValue* GetKey() { return key(); }
@@ skipping 718 matching lines @@
   virtual bool IsDeletable() const { return true; }
 };
 
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_INSTRUCTIONS_H_