src/hotspot/share/code/relocInfo.hpp

@@ -1,7 +1,7 @@
  /*
-  * Copyright (c) 1997, 2025, Oracle and/or its affiliates. All rights reserved.
+  * Copyright (c) 1997, 2026, Oracle and/or its affiliates. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.

@@ -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 +1071,47 @@
    friend class RelocIterator;
    friend class RelocationHolder;
    barrier_Relocation() : Relocation(relocInfo::barrier_type) { }
  };
  
+ class patchable_barrier_Relocation : public Relocation {
+  private:
+   static const int32_t unresolved = INT32_MAX;
+ 
+   int32_t _target_offset;
+   uint16_t _metadata;
+ 
+  public:
+   static RelocationHolder spec(uint16_t metadata) {
+     return RelocationHolder::construct<patchable_barrier_Relocation>(metadata);
+   }
+ 
+   patchable_barrier_Relocation(uint16_t metadata) : Relocation(relocInfo::patchable_barrier_type),
+     _target_offset(unresolved), _metadata(metadata) { }
+ 
+   void pack_data_to(CodeSection* dest) override;
+   void unpack_data() override;
+ 
+   void copy_into(RelocationHolder& holder) const override;
+ 
+   uint16_t metadata() const {
+     return _metadata;
+   }
+   bool is_target_offset_resolved() const {
+     return _target_offset != unresolved;
+   }
+   int32_t target_offset() const {
+     assert(is_target_offset_resolved(), "Should be");
+     return _target_offset;
+   }
+   void set_target_offset(int32_t 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.