gcc/config/i386/cygwin.asm

   1 /* stuff needed for libgcc on win32.
   2  *
   3  *   Copyright (C) 1996, 1998, 2001, 2003, 2008, 2009 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 3, or (at your option) any
   9  * later version.
  10  *
  11  * This file is distributed in the hope that it will be useful, but
  12  * WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * General Public License for more details.
  15  *
  16  * Under Section 7 of GPL version 3, you are granted additional
  17  * permissions described in the GCC Runtime Library Exception, version
  18  * 3.1, as published by the Free Software Foundation.
  19  *
  20  * You should have received a copy of the GNU General Public License and
  21  * a copy of the GCC Runtime Library Exception along with this program;
  22  * see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  23  * <http://www.gnu.org/licenses/>.
  24  */
  25
  26 #ifdef L_chkstk
  27
  28 /* Function prologue calls _alloca to probe the stack when allocating more
  29    than CHECK_STACK_LIMIT bytes in one go.  Touching the stack at 4K
  30    increments is necessary to ensure that the guard pages used
  31    by the OS virtual memory manger are allocated in correct sequence.  */
  32
  33         .global ___chkstk
  34         .global __alloca
  35 #ifndef _WIN64
  36 ___chkstk:
  37 __alloca:
  38         pushl   %ecx            /* save temp */
  39         leal    8(%esp), %ecx   /* point past return addr */
  40         cmpl    $0x1000, %eax   /* > 4k ?*/
  41         jb      Ldone
  42
  43 Lprobe:
  44         subl    $0x1000, %ecx           /* yes, move pointer down 4k*/
  45         orl     $0x0, (%ecx)            /* probe there */
  46         subl    $0x1000, %eax           /* decrement count */
  47         cmpl    $0x1000, %eax
  48         ja      Lprobe                  /* and do it again */
  49
  50 Ldone:
  51         subl    %eax, %ecx
  52         orl     $0x0, (%ecx)    /* less than 4k, just peek here */
  53
  54         movl    %esp, %eax      /* save old stack pointer */
  55         movl    %ecx, %esp      /* decrement stack */
  56         movl    (%eax), %ecx    /* recover saved temp */
  57         movl    4(%eax), %eax   /* recover return address */
  58
  59         /* Push the return value back.  Doing this instead of just
  60            jumping to %eax preserves the cached call-return stack
  61            used by most modern processors.  */
  62         pushl   %eax
  63         ret
  64 #else
  65 /* __alloca is a normal function call, which uses %rcx as the argument.  And stack space
  66    for the argument is saved.  */
  67 __alloca:
  68         movq    %rcx, %rax
  69         addq    $0x7, %rax
  70         andq    $0xfffffffffffffff8, %rax
  71         popq    %rcx            /* pop return address */
  72         popq    %r10            /* Pop the reserved stack space.  */
  73         movq    %rsp, %r10      /* get sp */
  74         cmpq    $0x1000, %rax   /* > 4k ?*/
  75         jb      Ldone_alloca
  76
  77 Lprobe_alloca:
  78         subq    $0x1000, %r10           /* yes, move pointer down 4k*/
  79         orq     $0x0, (%r10)            /* probe there */
  80         subq    $0x1000, %rax           /* decrement count */
  81         cmpq    $0x1000, %rax
  82         ja      Lprobe_alloca                   /* and do it again */
  83
  84 Ldone_alloca:
  85         subq    %rax, %r10
  86         orq     $0x0, (%r10)    /* less than 4k, just peek here */
  87         movq    %r10, %rax
  88         subq    $0x8, %r10      /* Reserve argument stack space.  */
  89         movq    %r10, %rsp      /* decrement stack */
  90
  91         /* Push the return value back.  Doing this instead of just
  92            jumping to %rcx preserves the cached call-return stack
  93            used by most modern processors.  */
  94         pushq   %rcx
  95         ret
  96
  97 /* ___chkstk is a *special* function call, which uses %rax as the argument.
  98    We avoid clobbering the 4 integer argument registers, %rcx, %rdx,
  99    %r8 and %r9, which leaves us with %rax, %r10, and %r11 to use.  */
 100 ___chkstk:
 101         addq    $0x7, %rax      /* Make sure stack is on alignment of 8.  */
 102         andq    $0xfffffffffffffff8, %rax
 103         popq    %r11            /* pop return address */
 104         movq    %rsp, %r10      /* get sp */
 105         cmpq    $0x1000, %rax   /* > 4k ?*/
 106         jb      Ldone
 107
 108 Lprobe:
 109         subq    $0x1000, %r10           /* yes, move pointer down 4k*/
 110         orl     $0x0, (%r10)            /* probe there */
 111         subq    $0x1000, %rax           /* decrement count */
 112         cmpq    $0x1000, %rax
 113         ja      Lprobe                  /* and do it again */
 114
 115 Ldone:
 116         subq    %rax, %r10
 117         orl     $0x0, (%r10)    /* less than 4k, just peek here */
 118         movq    %r10, %rsp      /* decrement stack */
 119
 120         /* Push the return value back.  Doing this instead of just
 121            jumping to %r11 preserves the cached call-return stack
 122            used by most modern processors.  */
 123         pushq   %r11
 124         ret
 125 #endif
 126 #endif