Implement basic array prefetching hints in Hydrogen.

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 4324 matching lines @@
   virtual HValue* GetKey() = 0;
   virtual void SetKey(HValue* key) = 0;
   virtual void SetIndexOffset(uint32_t index_offset) = 0;
   virtual bool IsDehoisted() = 0;
   virtual void SetDehoisted(bool is_dehoisted) = 0;
   virtual ~ArrayInstructionInterface() { };
 };
 
 
 class HLoadKeyed
-    : public HTemplateInstruction<3>, public ArrayInstructionInterface {
+    : public HTemplateInstruction<4>, public ArrayInstructionInterface {
  public:
   HLoadKeyed(HValue* obj,
              HValue* key,
              HValue* dependency,
+             HValue* prefetch_distance,
              ElementsKind elements_kind)
       : bit_field_(0) {
     bit_field_ = ElementsKindField::encode(elements_kind);
 
     SetOperandAt(0, obj);
     SetOperandAt(1, key);
     SetOperandAt(2, dependency);
+    SetOperandAt(3, prefetch_distance);
 
     if (!is_external()) {
       // I can detect the case between storing double (holey and fast) and
       // smi/object by looking at elements_kind_.
       ASSERT(IsFastSmiOrObjectElementsKind(elements_kind) ||
              IsFastDoubleElementsKind(elements_kind));
 
       if (IsFastSmiOrObjectElementsKind(elements_kind)) {
         if (IsFastSmiElementsKind(elements_kind) &&
             IsFastPackedElementsKind(elements_kind)) {
@@ skipping 21 matching lines @@
 
     SetFlag(kUseGVN);
   }
 
   bool is_external() const {
     return IsExternalArrayElementsKind(elements_kind());
   }
   HValue* elements() { return OperandAt(0); }
   HValue* key() { return OperandAt(1); }
   HValue* dependency() { return OperandAt(2); }
+  HValue* prefetch_distance() { return OperandAt(3); }
+  void SetPrefetchDistance(HValue* prefetch_distance) {
+    SetOperandAt(3, prefetch_distance);
+  }
   uint32_t index_offset() { return IndexOffsetField::decode(bit_field_); }
   void SetIndexOffset(uint32_t index_offset) {
     bit_field_ = IndexOffsetField::update(bit_field_, index_offset);
   }
   HValue* GetKey() { return key(); }
   void SetKey(HValue* key) { SetOperandAt(1, key); }
   bool IsDehoisted() { return IsDehoistedField::decode(bit_field_); }
   void SetDehoisted(bool is_dehoisted) {
     bit_field_ = IsDehoistedField::update(bit_field_, is_dehoisted);
   }
@@ skipping 982 matching lines @@
   virtual bool IsDeletable() const { return true; }
 };
 
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_INSTRUCTIONS_H_