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