1 /*
   2  * Copyright (c) 1999, 2010, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "opto/chaitin.hpp"
  27 #include "opto/machnode.hpp"
  28 
  29 // Disallow the use of the frame pointer (EBP) for implicit null exceptions
  30 // on win95/98.  If we do not do this, the OS gets confused and gives a stack
  31 // error.
  32 void PhaseRegAlloc::pd_preallocate_hook() {
  33 #ifndef _WIN64
  34   if (ImplicitNullChecks && !os::win32::is_nt()) {
  35     for (uint block_num=1; block_num<_cfg._num_blocks; block_num++) {
  36       Block *block = _cfg._blocks[block_num];
  37 
  38       Node *block_end = block->end();
  39       if (block_end->is_MachNullCheck() &&
  40           block_end->as_Mach()->ideal_Opcode() != Op_Con) {
  41         // The last instruction in the block is an implicit null check.
  42         // Fix its input so that it does not load into the frame pointer.
  43         _matcher.pd_implicit_null_fixup(block_end->in(1)->as_Mach(),
  44                                         block_end->as_MachNullCheck()->_vidx);
  45       }
  46     }
  47   }
  48 #else
  49   // WIN64==itanium on XP
  50 #endif
  51 }
  52 
  53 #ifdef ASSERT
  54 // Verify that no implicit null check uses the frame pointer (EBP) as
  55 // its register on win95/98.  Use of the frame pointer in an implicit
  56 // null check confuses the OS, yielding a stack error.
  57 void PhaseRegAlloc::pd_postallocate_verify_hook() {
  58 #ifndef _WIN64
  59   if (ImplicitNullChecks && !os::win32::is_nt()) {
  60     for (uint block_num=1; block_num<_cfg._num_blocks; block_num++) {
  61       Block *block = _cfg._blocks[block_num];
  62 
  63       Node *block_end = block->_nodes[block->_nodes.size()-1];
  64       if (block_end->is_MachNullCheck() && block_end->as_Mach()->ideal_Opcode() != Op_Con) {
  65         // The last instruction in the block is an implicit
  66         // null check.  Verify that this instruction does not
  67         // use the frame pointer.
  68         int reg = get_reg_first(block_end->in(1)->in(block_end->as_MachNullCheck()->_vidx));
  69         assert(reg != EBP_num,
  70                "implicit null check using frame pointer on win95/98");
  71       }
  72     }
  73   }
  74 #else
  75   // WIN64==itanium on XP
  76 #endif
  77 }
  78 #endif