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 /*

  * Copyright (c) 2004, 2010, 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.

  *

  */

 #ifndef SHARE_VM_PRIMS_JNIFASTGETFIELD_HPP

 #define SHARE_VM_PRIMS_JNIFASTGETFIELD_HPP

 #include "memory/allocation.hpp"

 #include "prims/jvm_misc.hpp"

 // Basic logic of a fast version of jni_Get<Primitive>Field:

 //

 // (See safepoint.hpp for a description of _safepoint_counter)

 //

 // load _safepoint_counter into old_counter

 // IF old_counter is odd THEN

 //   a safepoint is going on, return jni_GetXXXField

 // ELSE

 //   load the primitive field value into result (speculatively)

 //   load _safepoint_counter into new_counter

 //   IF (old_counter == new_counter) THEN

 //     no safepoint happened during the field access, return result

 //   ELSE

 //     a safepoint might have happened in-between, return jni_GetXXXField()

 //   ENDIF

 // ENDIF

 //

 // LoadLoad membars to maintain the load order may be necessary

 // for some platforms.

 //

 // The fast versions don't check for pending suspension request.

 // This is fine since it's totally read-only and doesn't create new race.

 //

 // There is a hypothetical safepoint counter wraparound. But it's not

 // a practical concern.

 class JNI_FastGetField : AllStatic {

  private:

   enum { LIST_CAPACITY = 40 };      // a conservative number for the number of

                                     // speculative loads on all the platforms

   static address speculative_load_pclist [];

   static address slowcase_entry_pclist   [];

   static int     count;

   static address generate_fast_get_int_field0(BasicType type);

   static address generate_fast_get_float_field0(BasicType type);

  public:

 #if defined(_WINDOWS) && !defined(_WIN64)

   static GetBooleanField_t jni_fast_GetBooleanField_fp;

   static GetByteField_t    jni_fast_GetByteField_fp;

   static GetCharField_t    jni_fast_GetCharField_fp;

   static GetShortField_t   jni_fast_GetShortField_fp;

   static GetIntField_t     jni_fast_GetIntField_fp;

   static GetLongField_t    jni_fast_GetLongField_fp;

   static GetFloatField_t   jni_fast_GetFloatField_fp;

   static GetDoubleField_t  jni_fast_GetDoubleField_fp;

 #endif

   static address generate_fast_get_boolean_field();

   static address generate_fast_get_byte_field();

   static address generate_fast_get_char_field();

   static address generate_fast_get_short_field();

   static address generate_fast_get_int_field();

   static address generate_fast_get_long_field();

   static address generate_fast_get_float_field();

   static address generate_fast_get_double_field();

   // If pc is in speculative_load_pclist, return the corresponding

   // slow case entry pc. Otherwise, return -1.

   // This is used by signal/exception handler to handle such case:

   // After an even safepoint counter is loaded and a fast field access

   // is about to begin, a GC kicks in and shrinks the heap. Then the

   // field access may fault. The signal/exception handler needs to

   // return to the slow case.

   //

   // The GC may decide to temporarily stuff some bad values into handles,

   // for example, for debugging purpose, in which case we need the mapping also.

   static address find_slowcase_pc(address pc);

 };

 #endif // SHARE_VM_PRIMS_JNIFASTGETFIELD_HPP