Improve implementation of HSeqStringSetChar.

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 190 matching lines @@
   V(BackingStoreFields)                        \
   V(Calls)                                     \
   V(ContextSlots)                              \
   V(DoubleArrayElements)                       \
   V(DoubleFields)                              \
   V(ElementsKind)                              \
   V(ElementsPointer)                           \
   V(GlobalVars)                                \
   V(InobjectFields)                            \
   V(OsrEntries)                                \
-  V(ExternalMemory)
+  V(ExternalMemory)                            \
+  V(StringChars)
 
 
 #define DECLARE_ABSTRACT_INSTRUCTION(type)                              \
   virtual bool Is##type() const V8_FINAL V8_OVERRIDE { return true; }   \
   static H##type* cast(HValue* value) {                                 \
     ASSERT(value->Is##type());                                          \
     return reinterpret_cast<H##type*>(value);                           \
   }
 
 
@@ skipping 313 matching lines @@
     *a = *b;
     *b = c;
   }
 
   HValue* base_;
   int offset_;
   int scale_;
 };
 
 
-typedef EnumSet<GVNFlag> GVNFlagSet;
+typedef EnumSet<GVNFlag, int64_t> GVNFlagSet;
 
 
 class HValue : public ZoneObject {
  public:
   static const int kNoNumber = -1;
 
   enum Flag {
     kFlexibleRepresentation,
     kCannotBeTagged,
     // Participate in Global Value Numbering, i.e. elimination of
@@ skipping 6187 matching lines @@
   }
 
  private:
   HStringCharCodeAt(HValue* context, HValue* string, HValue* index) {
     SetOperandAt(0, context);
     SetOperandAt(1, string);
     SetOperandAt(2, index);
     set_representation(Representation::Integer32());
     SetFlag(kUseGVN);
     SetGVNFlag(kDependsOnMaps);
+    SetGVNFlag(kDependsOnStringChars);
     SetGVNFlag(kChangesNewSpacePromotion);
   }
 
   // No side effects: runtime function assumes string + number inputs.
   virtual bool IsDeletable() const V8_OVERRIDE { return true; }
 };
 
 
 class HStringCharFromCode V8_FINAL : public HTemplateInstruction<2> {
  public:
@@ skipping 277 matching lines @@
 
  private:
   HSeqStringSetChar(String::Encoding encoding,
                     HValue* string,
                     HValue* index,
                     HValue* value) : encoding_(encoding) {
     SetOperandAt(0, string);
     SetOperandAt(1, index);
     SetOperandAt(2, value);
     set_representation(Representation::Tagged());
+    SetGVNFlag(kChangesStringChars);
   }
 
   String::Encoding encoding_;
 };
 
 
 class HCheckMapValue V8_FINAL : public HTemplateInstruction<2> {
  public:
   DECLARE_INSTRUCTION_FACTORY_P2(HCheckMapValue, HValue*, HValue*);
 
@@ skipping 130 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_