src/hotspot/share/ci/ciInstance.cpp - master - githubmirror/panama-vector

src/hotspot/share/ci/ciInstance.cpp
258 строк11 KB
David Simms
8389219: Implement JEP 401: Value Objects (Preview)
31 июл 2026, 03:45
31 июл 2026, 03:45cc278db
/*
 * Copyright (c) 1999, 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.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 *
 */

#include "ci/ciConstant.hpp"
#include "ci/ciField.hpp"
#include "ci/ciInlineKlass.hpp"
#include "ci/ciInstance.hpp"
#include "ci/ciInstanceKlass.hpp"
#include "ci/ciNullObject.hpp"
#include "ci/ciUtilities.inline.hpp"
#include "classfile/javaClasses.inline.hpp"
#include "classfile/vmClasses.hpp"
#include "oops/fieldStreams.hpp"
#include "oops/fieldStreams.inline.hpp"
#include "oops/oop.inline.hpp"
#include "oops/valuePayload.inline.hpp"

// ciInstance
//
// This class represents an instanceOop in the HotSpot virtual
// machine.

// ------------------------------------------------------------------
// ciObject::java_mirror_type
ciType* ciInstance::java_mirror_type() {
  VM_ENTRY_MARK;
  oop m = get_oop();
  // Return null if it is not java.lang.Class.
  if (m == nullptr || m->klass() != vmClasses::Class_klass()) {
    return nullptr;
  }
  // Return either a primitive type or a klass.
  if (java_lang_Class::is_primitive(m)) {
    return ciType::make(java_lang_Class::primitive_type(m));
  } else {
    Klass* k = java_lang_Class::as_Klass(m);
    assert(k != nullptr, "");
    return CURRENT_THREAD_ENV->get_klass(k);
  }
}

// ------------------------------------------------------------------
// ciInstance::field_value_impl
ciConstant ciInstance::field_value_impl(ciField* field) {
  BasicType field_bt = field->type()->basic_type();
  int offset = field->offset_in_bytes();
  ciConstant value = check_constant_value_cache(offset, field_bt);
  if (value.is_valid()) {
    return value;
  }
  VM_ENTRY_MARK;
  oop obj = get_oop();
  assert(obj != nullptr, "bad oop");
  switch(field_bt) {
    case T_BYTE:    value = ciConstant(field_bt, obj->byte_field(offset)); break;
    case T_CHAR:    value = ciConstant(field_bt, obj->char_field(offset)); break;
    case T_SHORT:   value = ciConstant(field_bt, obj->short_field(offset)); break;
    case T_BOOLEAN: value = ciConstant(field_bt, obj->bool_field(offset)); break;
    case T_INT:     value = ciConstant(field_bt, obj->int_field(offset)); break;
    case T_FLOAT:   value = ciConstant(obj->float_field(offset)); break;
    case T_DOUBLE:  value = ciConstant(obj->double_field(offset)); break;
    case T_LONG:    value = ciConstant(obj->long_field(offset)); break;
    case T_OBJECT:  // fall through
    case T_ARRAY: {
      if (field->is_flat()) {
        assert(field->is_atomic(), "do not query atomically a non-atomic flat field");
        InlineKlass* vk = field->type()->as_inline_klass()->get_InlineKlass();
        FlatValuePayload payload = FlatValuePayload::construct_from_parts(obj, offset, vk, field->layout_kind());
        oop res = payload.read(THREAD);
        if (HAS_PENDING_EXCEPTION) {
          CLEAR_PENDING_EXCEPTION;
          return ciConstant();
        }
        value = ciConstant(field_bt, CURRENT_ENV->get_object(res));
      } else {
        oop o = obj->obj_field(offset);

        // A field will be "constant" if it is known always to be
        // a non-null reference to an instance of a particular class,
        // or to a particular array.  This can happen even if the instance
        // or array is not perm.  In such a case, an "unloaded" ciArray
        // or ciInstance is created.  The compiler may be able to use
        // information about the object's class (which is exact) or length.

        if (o == nullptr) {
          value = ciConstant(field_bt, ciNullObject::make());
        } else {
          value = ciConstant(field_bt, CURRENT_ENV->get_object(o));
        }
      }
      break;
    }
    default:
      fatal("no field value: %s", type2name(field_bt));
  }
  add_to_constant_value_cache(offset, value);
  return value;
}

// ------------------------------------------------------------------
// ciInstance::field_value
//
// Constant value of a field of any kind: a declared field, or a leaf field.
// For a flat declared field, a cached copy of the value object is returned.
//
// Since stable fields can be treated as "constant" but are not really, we need
// to cache the value of fields so that the compiler will observe only one value
// per field. We also need to ensure that leaf fields from a single stable
// flat declared field will be observed to be consistent with each other.
//
// To do so, we need to always fetch the whole declared field containing the
// desired field. If we want a sub-field of a flat field, we then extract the field
// out of the cached copy, using sub_field_value.
//
// In the case we request a non-flat field, or a declared field (possibly flat), there
// is no sub-field to extract and sub_field_value will not be called.
ciConstant ciInstance::field_value(ciField* field) {
  assert(is_loaded(), "invalid access - must be loaded");
  assert(field->holder()->is_loaded(), "invalid access - holder must be loaded");
  assert(field->is_static() || field->holder()->is_inlinetype() || klass()->is_subclass_of(field->holder()),
         "invalid access - must be subclass");
  ciInstanceKlass* klass = this->klass()->as_instance_klass();
  int containing_field_idx = klass->field_index_by_offset(field->offset_in_bytes());
  ciField* containing_field = klass->declared_nonstatic_field_at(containing_field_idx);
  if (containing_field->is_flat() && !containing_field->is_atomic()) {
    assert(field != containing_field, "do not ask for a non atomic declared field");
    return field_value_impl(field);
  }
  ciConstant containing_field_value = field_value_impl(containing_field);
  if (!containing_field_value.is_valid()) {
    return ciConstant();
  }
  if (field->original_holder() == nullptr) {
    return containing_field_value;
  }
  ciObject* obj = containing_field_value.as_object();
  if (obj->is_instance()) {
    ciInstance* inst = obj->as_instance();
    // inst->klass() must be an inline klass since it is the value of a flat field.
    ciInlineKlass* inst_klass = inst->klass()->as_inline_klass();
    ciField* field_in_value_klass = inst_klass->get_field_by_offset(inst_klass->payload_offset() + field->offset_in_bytes() - containing_field->offset_in_bytes(), false);
    return inst->sub_field_value(field_in_value_klass);
  } else if (obj->is_null_object()) {
    return ciConstant::make_zero_or_null(field->type()->basic_type());
  }
  // obj should not be an array since we are trying to get a field inside it
  ShouldNotReachHere();
  return ciConstant();
}

// Extract a leaf field from a value object.
//
// This is used by field_value when getting the value of a sub-field. field_value
// will take care of getting the value of the declared field containing the requested
// field, and of caching (see the comment on field_value for why). But if we want the
// value of a sub-field, we need to extract it from the value of the declared field
// containing the said sub-field. This is what this function does.
//
// This is meant for internal used only. In particular, this function does not cache
// the result and must be called only on already cached values (to ensure consistency).
// field_value takes care of that.
ciConstant ciInstance::sub_field_value(ciField* field) {
  precond(klass()->is_inlinetype());
  precond(!field->is_flat());
  int offset = field->offset_in_bytes();
  BasicType field_btype = field->type()->basic_type();

  ciConstant value;
  VM_ENTRY_MARK;
  oop obj = get_oop();
  assert(obj != nullptr, "bad oop");
  switch(field_btype) {
  case T_BYTE:    value = ciConstant(field_btype, obj->byte_field(offset)); break;
  case T_CHAR:    value = ciConstant(field_btype, obj->char_field(offset)); break;
  case T_SHORT:   value = ciConstant(field_btype, obj->short_field(offset)); break;
  case T_BOOLEAN: value = ciConstant(field_btype, obj->bool_field(offset)); break;
  case T_INT:     value = ciConstant(field_btype, obj->int_field(offset)); break;
  case T_FLOAT:   value = ciConstant(obj->float_field(offset)); break;
  case T_DOUBLE:  value = ciConstant(obj->double_field(offset)); break;
  case T_LONG:    value = ciConstant(obj->long_field(offset)); break;
  case T_OBJECT:  // fall through
  case T_ARRAY: {
    oop o = obj->obj_field(offset);

    // A field will be "constant" if it is known always to be
    // a non-null reference to an instance of a particular class,
    // or to a particular array.  This can happen even if the instance
    // or array is not perm.  In such a case, an "unloaded" ciArray
    // or ciInstance is created.  The compiler may be able to use
    // information about the object's class (which is exact) or length.

    if (o == nullptr) {
      value = ciConstant(field_btype, ciNullObject::make());
    } else {
      value = ciConstant(field_btype, CURRENT_ENV->get_object(o));
    }
    break;
  }
  default:
    fatal("no field value: %s", type2name(field_btype));
  }
  return value;
}

// ------------------------------------------------------------------
// ciInstance::field_value_by_offset
//
// Constant value of a field at the specified offset.
ciConstant ciInstance::field_value_by_offset(int field_offset) {
  ciInstanceKlass* ik = klass()->as_instance_klass();
  ciField* field = ik->get_field_by_offset(field_offset, false);
  if (field == nullptr)
    return ciConstant();  // T_ILLEGAL
  return field_value(field);
}

// ------------------------------------------------------------------
// ciInstance::print_impl
//
// Implementation of the print method.
void ciInstance::print_impl(outputStream* st) {
  st->print(" type=");
  klass()->print(st);
}


ciKlass* ciInstance::java_lang_Class_klass() {
  VM_ENTRY_MARK;
  assert(java_lang_Class::as_Klass(get_oop()) != nullptr, "klass is null");
  return CURRENT_ENV->get_metadata(java_lang_Class::as_Klass(get_oop()))->as_klass();
}

char* ciInstance::java_lang_String_str(char* buf, size_t buflen) {
  VM_ENTRY_MARK;
  assert(get_oop()->is_a(vmClasses::String_klass()), "not a String");
  return java_lang_String::as_utf8_string(get_oop(), buf, buflen);
}