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 #ifndef _WIN64
  46 ___chkstk:
  47 __alloca:
  48         pushl   %ecx            /* save temp */
  49         leal    8(%esp), %ecx   /* point past return addr */
  50         cmpl    $0x1000, %eax   /* > 4k ?*/
  51         jb      Ldone
  52
  53 Lprobe:
  54         subl    $0x1000, %ecx           /* yes, move pointer down 4k*/
  55         orl     $0x0, (%ecx)            /* probe there */
  56         subl    $0x1000, %eax           /* decrement count */
  57         cmpl    $0x1000, %eax
  58         ja      Lprobe                  /* and do it again */
  59
  60 Ldone:
  61         subl    %eax, %ecx
  62         orl     $0x0, (%ecx)    /* less than 4k, just peek here */
  63
  64         movl    %esp, %eax      /* save old stack pointer */
  65         movl    %ecx, %esp      /* decrement stack */
  66         movl    (%eax), %ecx    /* recover saved temp */
  67         movl    4(%eax), %eax   /* recover return address */
  68
  69         /* Push the return value back.  Doing this instead of just
  70            jumping to %eax preserves the cached call-return stack
  71            used by most modern processors.  */
  72         pushl   %eax
  73         ret
  74 #else
  75 /* __alloca is a normal function call, which uses %rcx as the argument.  And stack space
  76    for the argument is saved.  */
  77 __alloca:
  78         movq    %rcx, %rax
  79         addq    $0x7, %rax
  80         andq    $0xfffffffffffffff8, %rax
  81         popq    %rcx            /* pop return address */
  82         popq    %r10            /* Pop the reserved stack space.  */
  83         movq    %rsp, %r10      /* get sp */
  84         cmpq    $0x1000, %rax   /* > 4k ?*/
  85         jb      Ldone_alloca
  86
  87 Lprobe_alloca:
  88         subq    $0x1000, %r10           /* yes, move pointer down 4k*/
  89         orq     $0x0, (%r10)            /* probe there */
  90         subq    $0x1000, %rax           /* decrement count */
  91         cmpq    $0x1000, %rax
  92         ja      Lprobe_alloca                   /* and do it again */
  93
  94 Ldone_alloca:
  95         subq    %rax, %r10
  96         orq     $0x0, (%r10)    /* less than 4k, just peek here */
  97         movq    %r10, %rax
  98         subq    $0x8, %r10      /* Reserve argument stack space.  */
  99         movq    %r10, %rsp      /* decrement stack */
 100
 101         /* Push the return value back.  Doing this instead of just
 102            jumping to %rcx preserves the cached call-return stack
 103            used by most modern processors.  */
 104         pushq   %rcx
 105         ret
 106
 107 /* ___chkstk is a *special* function call, which uses %rax as the argument.
 108    We avoid clobbering the 4 integer argument registers, %rcx, %rdx,
 109    %r8 and %r9, which leaves us with %rax, %r10, and %r11 to use.  */
 110 ___chkstk:
 111         addq    $0x7, %rax      /* Make sure stack is on alignment of 8.  */
 112         andq    $0xfffffffffffffff8, %rax
 113         popq    %r11            /* pop return address */
 114         movq    %rsp, %r10      /* get sp */
 115         cmpq    $0x1000, %rax   /* > 4k ?*/
 116         jb      Ldone
 117
 118 Lprobe:
 119         subq    $0x1000, %r10           /* yes, move pointer down 4k*/
 120         orl     $0x0, (%r10)            /* probe there */
 121         subq    $0x1000, %rax           /* decrement count */
 122         cmpq    $0x1000, %rax
 123         ja      Lprobe                  /* and do it again */
 124
 125 Ldone:
 126         subq    %rax, %r10
 127         orl     $0x0, (%r10)    /* less than 4k, just peek here */
 128         movq    %r10, %rsp      /* decrement stack */
 129
 130         /* Push the return value back.  Doing this instead of just
 131            jumping to %r11 preserves the cached call-return stack
 132            used by most modern processors.  */
 133         pushq   %r11
 134         ret
 135 #endif
 136 #endif