Only set binary operation side effects flags, when observable.

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 3929 matching lines @@
   HBitwiseBinaryOperation(HValue* context, HValue* left, HValue* right,
                           HType type = HType::Tagged())
       : HBinaryOperation(context, left, right, type) {
     SetFlag(kFlexibleRepresentation);
     SetFlag(kTruncatingToInt32);
     SetFlag(kAllowUndefinedAsNaN);
     SetAllSideEffects();
   }
 
   virtual void RepresentationChanged(Representation to) V8_OVERRIDE {
-    if (to.IsTagged()) {
+    if (to.IsTagged()) SetGVNFlag(kChangesNewSpacePromotion);
+    if (to.IsTagged() &&
+        (left()->ToNumberCanBeObserved() || right()->ToNumberCanBeObserved())) {
       SetAllSideEffects();
       ClearFlag(kUseGVN);
     } else {
-      ASSERT(to.IsSmiOrInteger32());
       ClearAllSideEffects();
       SetFlag(kUseGVN);
     }
   }
 
   virtual void UpdateRepresentation(Representation new_rep,
                                     HInferRepresentationPhase* h_infer,
                                     const char* reason) V8_OVERRIDE {
     // We only generate either int32 or generic tagged bitwise operations.
     if (new_rep.IsDouble()) new_rep = Representation::Integer32();
@@ skipping 51 matching lines @@
 class HArithmeticBinaryOperation : public HBinaryOperation {
  public:
   HArithmeticBinaryOperation(HValue* context, HValue* left, HValue* right)
       : HBinaryOperation(context, left, right, HType::TaggedNumber()) {
     SetAllSideEffects();
     SetFlag(kFlexibleRepresentation);
     SetFlag(kAllowUndefinedAsNaN);
   }
 
   virtual void RepresentationChanged(Representation to) V8_OVERRIDE {
-    if (to.IsTagged()) {
+    if (to.IsTagged()) SetGVNFlag(kChangesNewSpacePromotion);
+    if (to.IsTagged() &&
+        (left()->ToNumberCanBeObserved() || right()->ToNumberCanBeObserved())) {
       SetAllSideEffects();
       ClearFlag(kUseGVN);
     } else {
       ClearAllSideEffects();
       SetFlag(kUseGVN);
     }
   }
 
   DECLARE_ABSTRACT_INSTRUCTION(ArithmeticBinaryOperation)
  private:
@@ skipping 518 matching lines @@
       return true;
     } else if (right()->IsInteger32Constant()) {
       decomposition->Apply(left(), right()->GetInteger32Constant());
       return true;
     } else {
       return false;
     }
   }
 
   virtual void RepresentationChanged(Representation to) V8_OVERRIDE {
-    if (to.IsTagged()) ClearFlag(kAllowUndefinedAsNaN);
-    HArithmeticBinaryOperation::RepresentationChanged(to);
+    if (to.IsTagged()) {
+      SetGVNFlag(kChangesNewSpacePromotion);
+      ClearFlag(kAllowUndefinedAsNaN);
+    }
+    if (to.IsTagged() &&
+        (left()->ToNumberCanBeObserved() || right()->ToNumberCanBeObserved() ||
+         left()->ToStringCanBeObserved() || right()->ToStringCanBeObserved())) {
+      SetAllSideEffects();
+      ClearFlag(kUseGVN);
+    } else {
+      ClearAllSideEffects();
+      SetFlag(kUseGVN);
+    }
   }
 
   DECLARE_CONCRETE_INSTRUCTION(Add)
 
  protected:
   virtual bool DataEquals(HValue* other) V8_OVERRIDE { return true; }
 
   virtual Range* InferRange(Zone* zone) V8_OVERRIDE;
 
  private:
@@ skipping 2048 matching lines @@
 
   DECLARE_CONCRETE_INSTRUCTION(StringAdd)
 
  protected:
   virtual bool DataEquals(HValue* other) V8_OVERRIDE { return true; }
 
  private:
   HStringAdd(HValue* context, HValue* left, HValue* right, StringAddFlags flags)
       : HBinaryOperation(context, left, right, HType::String()), flags_(flags) {
     set_representation(Representation::Tagged());
-    if (flags_ == STRING_ADD_CHECK_NONE) {
+    if (MightHaveSideEffects()) {
+      SetAllSideEffects();
+    } else {
       SetFlag(kUseGVN);
       SetGVNFlag(kDependsOnMaps);
       SetGVNFlag(kChangesNewSpacePromotion);
-    } else {
-      SetAllSideEffects();
     }
   }
 
+  bool MightHaveSideEffects() const {
+    return flags_ != STRING_ADD_CHECK_NONE &&
+      (left()->ToStringCanBeObserved() || right()->ToStringCanBeObserved());
+  }
+
   // No side-effects except possible allocation:
   // NOTE: this instruction does not call ToString() on its inputs, when flags_
   // is set to STRING_ADD_CHECK_NONE.
   virtual bool IsDeletable() const V8_OVERRIDE {
-    return flags_ == STRING_ADD_CHECK_NONE;
+    return !MightHaveSideEffects();
   }
 
   const StringAddFlags flags_;
 };
 
 
 class HStringCharCodeAt V8_FINAL : public HTemplateInstruction<3> {
  public:
   DECLARE_INSTRUCTION_WITH_CONTEXT_FACTORY_P2(HStringCharCodeAt,
                                               HValue*,
@@ skipping 460 matching lines @@
   virtual bool IsDeletable() const V8_OVERRIDE { return true; }
 };
 
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_INSTRUCTIONS_H_