src/hotspot/share/code/relocInfo.hpp

*** 267,10 ***
--- 267,11 ---
      runtime_call_w_cp_type  = 14, // Runtime call which may load its target from the constant pool
      data_prefix_tag         = 15, // tag for a prefix (carries data arguments)
      post_call_nop_type      = 16, // A tag for post call nop relocations
      entry_guard_type        = 17, // A tag for an nmethod entry barrier guard value
      barrier_type            = 18, // GC barrier data
+     patchable_barrier_type  = 19, // Patchable GC barrier
      type_mask               = 31  // A mask which selects only the above values
    };
  
   private:
    unsigned short _value;

*** 309,10 ***
--- 310,11 ---
      visitor(section_word) \
      visitor(trampoline_stub) \
      visitor(post_call_nop) \
      visitor(entry_guard) \
      visitor(barrier) \
+     visitor(patchable_barrier) \
  
  
   public:
    enum : unsigned short{
      value_width             = sizeof(unsigned short) * BitsPerByte,

*** 1069,10 ***
--- 1071,37 ---
    friend class RelocIterator;
    friend class RelocationHolder;
    barrier_Relocation() : Relocation(relocInfo::barrier_type) { }
  };
  
+ class patchable_barrier_Relocation : public Relocation {
+ public:
+   jint _metadata;
+   jint _target_offset;
+ 
+   static RelocationHolder spec(int metadata) {
+     return RelocationHolder::construct<patchable_barrier_Relocation>(metadata);
+   }
+ 
+   patchable_barrier_Relocation(int metadata) : Relocation(relocInfo::patchable_barrier_type),
+     _metadata(metadata), _target_offset(0) { }
+ 
+   void pack_data_to(CodeSection* dest) override;
+   void unpack_data() override;
+ 
+   void copy_into(RelocationHolder& holder) const override;
+ 
+   jint metadata() const { return _metadata; }
+   jint target_offset() const { return _target_offset; }
+ 
+   void set_target_offset(jint target_offset);
+ 
+ private:
+   friend class RelocIterator;
+   friend class RelocationHolder;
+   patchable_barrier_Relocation() : Relocation(relocInfo::patchable_barrier_type) { }
+ };
  
  class virtual_call_Relocation : public CallRelocation {
  
   public:
    // "cached_value" points to the first associated set-oop.