gomp-20050608-branch/gcc/config/i386/cygwin.asm

   1 /* stuff needed for libgcc on win32.
   2  *
   3  *   Copyright (C) 1996, 1998, 2001, 2003 Free Software Foundation, Inc.
   4  *   Written By Steve Chamberlain
   5  *
   6  * This file is free software; you can redistribute it and/or modify it
   7  * under the terms of the GNU General Public License as published by the
   8  * Free Software Foundation; either version 2, or (at your option) any
   9  * later version.
  10  *
  11  * In addition to the permissions in the GNU General Public License, the
  12  * Free Software Foundation gives you unlimited permission to link the
  13  * compiled version of this file with other programs, and to distribute
  14  * those programs without any restriction coming from the use of this
  15  * file.  (The General Public License restrictions do apply in other
  16  * respects; for example, they cover modification of the file, and
  17  * distribution when not linked into another program.)
  18  *
  19  * This file is distributed in the hope that it will be useful, but
  20  * WITHOUT ANY WARRANTY; without even the implied warranty of
  21  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  22  * General Public License for more details.
  23  *
  24  * You should have received a copy of the GNU General Public License
  25  * along with this program; see the file COPYING.  If not, write to
  26  * the Free Software Foundation, 51 Franklin Street, Fifth Floor,
  27  * Boston, MA 02110-1301, USA.
  28  *
  29  *    As a special exception, if you link this library with files
  30  *    compiled with GCC to produce an executable, this does not cause
  31  *    the resulting executable to be covered by the GNU General Public License.
  32  *    This exception does not however invalidate any other reasons why
  33  *    the executable file might be covered by the GNU General Public License.
  34  */
  35
  36 #ifdef L_chkstk
  37
  38 /* Function prologue calls _alloca to probe the stack when allocating more
  39    than CHECK_STACK_LIMIT bytes in one go.  Touching the stack at 4K
  40    increments is necessary to ensure that the guard pages used
  41    by the OS virtual memory manger are allocated in correct sequence.  */
  42
  43         .global ___chkstk
  44         .global __alloca
  45 ___chkstk:
  46 __alloca:
  47         pushl  %ecx             /* save temp */
  48         movl   %esp,%ecx        /* get sp */
  49         addl   $0x8,%ecx        /* and point to return addr */
  50
  51 probe:  cmpl   $0x1000,%eax     /* > 4k ?*/
  52         jb    done
  53
  54         subl   $0x1000,%ecx             /* yes, move pointer down 4k*/
  55         orl    $0x0,(%ecx)              /* probe there */
  56         subl   $0x1000,%eax             /* decrement count */
  57         jmp    probe                    /* and do it again */
  58
  59 done:   subl   %eax,%ecx
  60         orl    $0x0,(%ecx)      /* less that 4k, just peek here */
  61
  62         movl   %esp,%eax
  63         movl   %ecx,%esp        /* decrement stack */
  64
  65         movl   (%eax),%ecx      /* recover saved temp */
  66         movl   4(%eax),%eax     /* get return address */
  67         jmp    *%eax
  68 #endif