Supported folding of constant size allocation followed by dynamic size allocation.

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 1219 matching lines @@
   virtual int operand_position(int index) const V8_OVERRIDE {
     const int pos = position_.operand_position(index);
     return (pos != RelocInfo::kNoPosition) ? pos : position();
   }
   void set_operand_position(Zone* zone, int index, int pos) {
     ASSERT(0 <= index && index < OperandCount());
     position_.ensure_storage_for_operand_positions(zone, OperandCount());
     position_.set_operand_position(index, pos);
   }
 
+  bool Dominates(HInstruction* other);
+
   bool CanTruncateToInt32() const { return CheckFlag(kTruncatingToInt32); }
 
   virtual LInstruction* CompileToLithium(LChunkBuilder* builder) = 0;
 
 #ifdef DEBUG
   virtual void Verify() V8_OVERRIDE;
 #endif
 
   virtual bool IsCall() { return false; }
 
@@ skipping 4193 matching lines @@
     return new(zone) HAllocate(context, size, type, pretenure_flag,
         instance_type);
   }
 
   // Maximum instance size for which allocations will be inlined.
   static const int kMaxInlineSize = 64 * kPointerSize;
 
   HValue* context() { return OperandAt(0); }
   HValue* size() { return OperandAt(1); }
 
+  HAllocate* wired_allocate() { return wired_allocate_; }
+  void set_wired_allocate(HAllocate* alloc) { wired_allocate_ = alloc; }
+
   virtual Representation RequiredInputRepresentation(int index) V8_OVERRIDE {
     if (index == 0) {
       return Representation::Tagged();
     } else {
       return Representation::Integer32();
     }
   }
 
   virtual Handle<Map> GetMonomorphicJSObjectMap() {
     return known_initial_map_;
@@ skipping 47 matching lines @@
     PREFILL_WITH_FILLER = 1 << 4
   };
 
   HAllocate(HValue* context,
             HValue* size,
             HType type,
             PretenureFlag pretenure_flag,
             InstanceType instance_type)
       : HTemplateInstruction<2>(type),
         dominating_allocate_(NULL),
+        wired_allocate_(NULL),
         filler_free_space_size_(NULL),
         clear_next_map_word_(false) {
     SetOperandAt(0, context);
     SetOperandAt(1, size);
     set_representation(Representation::Tagged());
     SetFlag(kTrackSideEffectDominators);
     SetGVNFlag(kChangesNewSpacePromotion);
     SetGVNFlag(kDependsOnNewSpacePromotion);
     flags_ = pretenure_flag == TENURED
         ? (Heap::TargetSpaceId(instance_type) == OLD_POINTER_SPACE
@@ skipping 29 matching lines @@
         (IsOldDataSpaceAllocation() && allocate->IsOldDataSpaceAllocation()) ||
         (IsOldPointerSpaceAllocation() &&
             allocate->IsOldPointerSpaceAllocation());
   }
 
   void ClearNextMapWord(int offset);
 
   Flags flags_;
   Handle<Map> known_initial_map_;
   HAllocate* dominating_allocate_;
+  // JSArray allocation will contain pointer to FixedArray allocation here.
+  // Allocation folding will treat wired allocations differently.
+  HAllocate* wired_allocate_;
   HStoreNamedField* filler_free_space_size_;
   bool clear_next_map_word_;
 };
 
 
 class HStoreCodeEntry V8_FINAL: public HTemplateInstruction<2> {
  public:
   static HStoreCodeEntry* New(Zone* zone,
                               HValue* context,
                               HValue* function,
@@ skipping 1894 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_