1 /*
   2  * Copyright 2004-2008 Sun Microsystems, Inc.  All Rights Reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
  20  * CA 95054 USA or visit www.sun.com if you need additional information or
  21  * have any questions.
  22  *
  23  */
  24 
  25 # include "incls/_precompiled.incl"
  26 # include "incls/_dump_x86_32.cpp.incl"
  27 
  28 
  29 
  30 // Generate the self-patching vtable method:
  31 //
  32 // This method will be called (as any other Klass virtual method) with
  33 // the Klass itself as the first argument.  Example:
  34 //
  35 //      oop obj;
  36 //      int size = obj->klass()->klass_part()->oop_size(this);
  37 //
  38 // for which the virtual method call is Klass::oop_size();
  39 //
  40 // The dummy method is called with the Klass object as the first
  41 // operand, and an object as the second argument.
  42 //
  43 
  44 //=====================================================================
  45 
  46 // All of the dummy methods in the vtable are essentially identical,
  47 // differing only by an ordinal constant, and they bear no releationship
  48 // to the original method which the caller intended. Also, there needs
  49 // to be 'vtbl_list_size' instances of the vtable in order to
  50 // differentiate between the 'vtable_list_size' original Klass objects.
  51 
  52 #define __ masm->
  53 
  54 void CompactingPermGenGen::generate_vtable_methods(void** vtbl_list,
  55                                                    void** vtable,
  56                                                    char** md_top,
  57                                                    char* md_end,
  58                                                    char** mc_top,
  59                                                    char* mc_end) {
  60 
  61   intptr_t vtable_bytes = (num_virtuals * vtbl_list_size) * sizeof(void*);
  62   *(intptr_t *)(*md_top) = vtable_bytes;
  63   *md_top += sizeof(intptr_t);
  64   void** dummy_vtable = (void**)*md_top;
  65   *vtable = dummy_vtable;
  66   *md_top += vtable_bytes;
  67 
  68   // Get ready to generate dummy methods.
  69 
  70   CodeBuffer cb((unsigned char*)*mc_top, mc_end - *mc_top);
  71   MacroAssembler* masm = new MacroAssembler(&cb);
  72 
  73   Label common_code;
  74   for (int i = 0; i < vtbl_list_size; ++i) {
  75     for (int j = 0; j < num_virtuals; ++j) {
  76       dummy_vtable[num_virtuals * i + j] = (void*)masm->pc();
  77 
  78       // Load rax, with a value indicating vtable/offset pair.
  79       // -- bits[ 7..0]  (8 bits) which virtual method in table?
  80       // -- bits[12..8]  (5 bits) which virtual method table?
  81       // -- must fit in 13-bit instruction immediate field.
  82       __ movl(rax, (i << 8) + j);
  83       __ jmp(common_code);
  84     }
  85   }
  86 
  87   __ bind(common_code);
  88 
  89 #ifdef WIN32
  90   // Expecting to be called with "thiscall" conventions -- the arguments
  91   // are on the stack, except that the "this" pointer is in rcx.
  92 #else
  93   // Expecting to be called with Unix conventions -- the arguments
  94   // are on the stack, including the "this" pointer.
  95 #endif
  96 
  97   // In addition, rax was set (above) to the offset of the method in the
  98   // table.
  99 
 100 #ifdef WIN32
 101   __ push(rcx);                         // save "this"
 102 #endif
 103   __ mov(rcx, rax);
 104   __ shrptr(rcx, 8);                    // isolate vtable identifier.
 105   __ shlptr(rcx, LogBytesPerWord);
 106   Address index(noreg, rcx,  Address::times_1);
 107   ExternalAddress vtbl((address)vtbl_list);
 108   __ movptr(rdx, ArrayAddress(vtbl, index)); // get correct vtable address.
 109 #ifdef WIN32
 110   __ pop(rcx);                          // restore "this"
 111 #else
 112   __ movptr(rcx, Address(rsp, BytesPerWord));   // fetch "this"
 113 #endif
 114   __ movptr(Address(rcx, 0), rdx);      // update vtable pointer.
 115 
 116   __ andptr(rax, 0x00ff);                       // isolate vtable method index
 117   __ shlptr(rax, LogBytesPerWord);
 118   __ addptr(rax, rdx);                  // address of real method pointer.
 119   __ jmp(Address(rax, 0));              // get real method pointer.
 120 
 121   __ flush();
 122 
 123   *mc_top = (char*)__ pc();
 124 }