src/hotspot/share/gc/shared/accessBarrierSupport.cpp

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#include "classfile/javaClasses.inline.hpp"
#include "gc/shared/accessBarrierSupport.inline.hpp"
#include "oops/access.hpp"

DecoratorSet AccessBarrierSupport::resolve_unknown_oop_ref_strength(DecoratorSet decorators, oop base, ptrdiff_t offset) {
  // Note that the referent in a FinalReference is technically not strong.
  // However, it always behaves like one in practice. The two cases are:
  //   1) A mutator calls Reference.get(). However, a mutator can only ever
  //      see inactive FinalReferences, whose referents really are strong.
  //   2) A GC heap walking operation. In this case the GC can see active
  //      FinalReferences, but the GC always wants to follow the referent
  //      as if it was strong.
  DecoratorSet ds = decorators & ~ON_UNKNOWN_OOP_REF;
  if (!java_lang_ref_Reference::is_referent_field(base, offset) ||
      java_lang_ref_Reference::is_final(base)) {
    ds |= ON_STRONG_OOP_REF;
  } else if (java_lang_ref_Reference::is_phantom(base)) {
    ds |= ON_PHANTOM_OOP_REF;
  } else {
    ds |= ON_WEAK_OOP_REF;
  }
  return ds;
}