Subversion Repositories openrisc_2011-10-31

/* stuff needed for libgcc on win32.
 *
 *   Copyright (C) 1996, 1998, 2001, 2003, 2008, 2009 Free Software Foundation, Inc.
 *   Written By Steve Chamberlain
 * 
 * This file is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 3, or (at your option) any
 * later version.
 * 
 * This file is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 * 
 * Under Section 7 of GPL version 3, you are granted additional
 * permissions described in the GCC Runtime Library Exception, version
 * 3.1, as published by the Free Software Foundation.
 * 
 * You should have received a copy of the GNU General Public License and
 * a copy of the GCC Runtime Library Exception along with this program;
 * see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 * <http://www.gnu.org/licenses/>.
 */

#ifdef L_chkstk

/* Function prologue calls _alloca to probe the stack when allocating more
   than CHECK_STACK_LIMIT bytes in one go.  Touching the stack at 4K
   increments is necessary to ensure that the guard pages used
   by the OS virtual memory manger are allocated in correct sequence.  */

        .global ___chkstk
        .global __alloca
#ifndef _WIN64
___chkstk:
__alloca:
        pushl   %ecx            /* save temp */
        leal    8(%esp), %ecx   /* point past return addr */
        cmpl    $0x1000, %eax   /* > 4k ?*/
        jb      Ldone

Lprobe:
        subl    $0x1000, %ecx           /* yes, move pointer down 4k*/
        orl     $0x0, (%ecx)            /* probe there */
        subl    $0x1000, %eax           /* decrement count */
        cmpl    $0x1000, %eax
        ja      Lprobe                  /* and do it again */

Ldone:
        subl    %eax, %ecx         
        orl     $0x0, (%ecx)    /* less than 4k, just peek here */

        movl    %esp, %eax      /* save old stack pointer */
        movl    %ecx, %esp      /* decrement stack */
        movl    (%eax), %ecx    /* recover saved temp */
        movl    4(%eax), %eax   /* recover return address */

        /* Push the return value back.  Doing this instead of just
           jumping to %eax preserves the cached call-return stack
           used by most modern processors.  */
        pushl   %eax
        ret
#else
/* __alloca is a normal function call, which uses %rcx as the argument.  And stack space
   for the argument is saved.  */
__alloca:
        movq    %rcx, %rax
        addq    $0x7, %rax
        andq    $0xfffffffffffffff8, %rax
        popq    %rcx            /* pop return address */
        popq    %r10            /* Pop the reserved stack space.  */
        movq    %rsp, %r10      /* get sp */
        cmpq    $0x1000, %rax   /* > 4k ?*/
        jb      Ldone_alloca

Lprobe_alloca:
        subq    $0x1000, %r10           /* yes, move pointer down 4k*/
        orq     $0x0, (%r10)            /* probe there */
        subq    $0x1000, %rax           /* decrement count */
        cmpq    $0x1000, %rax
        ja      Lprobe_alloca                   /* and do it again */

Ldone_alloca:
        subq    %rax, %r10
        orq     $0x0, (%r10)    /* less than 4k, just peek here */
        movq    %r10, %rax
        subq    $0x8, %r10      /* Reserve argument stack space.  */
        movq    %r10, %rsp      /* decrement stack */

        /* Push the return value back.  Doing this instead of just
           jumping to %rcx preserves the cached call-return stack
           used by most modern processors.  */
        pushq   %rcx
        ret

/* ___chkstk is a *special* function call, which uses %rax as the argument.
   We avoid clobbering the 4 integer argument registers, %rcx, %rdx, 
   %r8 and %r9, which leaves us with %rax, %r10, and %r11 to use.  */
___chkstk:
        addq    $0x7, %rax      /* Make sure stack is on alignment of 8.  */
        andq    $0xfffffffffffffff8, %rax
        popq    %r11            /* pop return address */
        movq    %rsp, %r10      /* get sp */
        cmpq    $0x1000, %rax   /* > 4k ?*/
        jb      Ldone

Lprobe:
        subq    $0x1000, %r10           /* yes, move pointer down 4k*/
        orl     $0x0, (%r10)            /* probe there */
        subq    $0x1000, %rax           /* decrement count */
        cmpq    $0x1000, %rax
        ja      Lprobe                  /* and do it again */

Ldone:
        subq    %rax, %r10
        orl     $0x0, (%r10)    /* less than 4k, just peek here */
        movq    %r10, %rsp      /* decrement stack */

        /* Push the return value back.  Doing this instead of just
           jumping to %r11 preserves the cached call-return stack
           used by most modern processors.  */
        pushq   %r11
        ret
#endif
#endif