/*

 * Copyright (c) 2004, 2012, 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 "precompiled.hpp"

#include "asm/macroAssembler.hpp"

#include "asm/codeBuffer.hpp"

#include "memory/metaspaceShared.hpp"

// Generate the self-patching vtable method:

//

// This method will be called (as any other Klass virtual method) with

// the Klass itself as the first argument.  Example:

//

//      oop obj;

//      int size = obj->klass()->oop_size(this);

//

// for which the virtual method call is Klass::oop_size();

//

// The dummy method is called with the Klass object as the first

// operand, and an object as the second argument.

//

//=====================================================================

// All of the dummy methods in the vtable are essentially identical,

// differing only by an ordinal constant, and they bear no relationship

// to the original method which the caller intended. Also, there needs

// to be 'vtbl_list_size' instances of the vtable in order to

// differentiate between the 'vtable_list_size' original Klass objects.

#define __ masm->

void MetaspaceShared::generate_vtable_methods(void** vtbl_list,

                                                   void** vtable,

                                                   char** md_top,

                                                   char* md_end,

                                                   char** mc_top,

                                                   char* mc_end) {

  intptr_t vtable_bytes = (num_virtuals * vtbl_list_size) * sizeof(void*);

  *(intptr_t *)(*md_top) = vtable_bytes;

  *md_top += sizeof(intptr_t);

  void** dummy_vtable = (void**)*md_top;

  *vtable = dummy_vtable;

  *md_top += vtable_bytes;

  // Get ready to generate dummy methods.

  CodeBuffer cb((unsigned char*)*mc_top, mc_end - *mc_top);

  MacroAssembler* masm = new MacroAssembler(&cb);

  Label common_code;

  for (int i = 0; i < vtbl_list_size; ++i) {

    for (int j = 0; j < num_virtuals; ++j) {

      dummy_vtable[num_virtuals * i + j] = (void*)masm->pc();

      // Load rax, with a value indicating vtable/offset pair.

      // -- bits[ 7..0]  (8 bits) which virtual method in table?

      // -- bits[12..8]  (5 bits) which virtual method table?

      // -- must fit in 13-bit instruction immediate field.

      __ movl(rax, (i << 8) + j);

      __ jmp(common_code);

    }

  }

  __ bind(common_code);

#ifdef WIN32

  // Expecting to be called with "thiscall" conventions -- the arguments

  // are on the stack, except that the "this" pointer is in rcx.

#else

  // Expecting to be called with Unix conventions -- the arguments

  // are on the stack, including the "this" pointer.

#endif

  // In addition, rax was set (above) to the offset of the method in the

  // table.

#ifdef WIN32

  __ push(rcx);                         // save "this"

#endif

  __ mov(rcx, rax);

  __ shrptr(rcx, 8);                    // isolate vtable identifier.

  __ shlptr(rcx, LogBytesPerWord);

  Address index(noreg, rcx,  Address::times_1);

  ExternalAddress vtbl((address)vtbl_list);

  __ movptr(rdx, ArrayAddress(vtbl, index)); // get correct vtable address.

#ifdef WIN32

  __ pop(rcx);                          // restore "this"

#else

  __ movptr(rcx, Address(rsp, BytesPerWord));   // fetch "this"

#endif

  __ movptr(Address(rcx, 0), rdx);      // update vtable pointer.

  __ andptr(rax, 0x00ff);                       // isolate vtable method index

  __ shlptr(rax, LogBytesPerWord);

  __ addptr(rax, rdx);                  // address of real method pointer.

  __ jmp(Address(rax, 0));              // get real method pointer.

  __ flush();

  *mc_top = (char*)__ pc();

}