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jeremybenn |
/* stuff needed for libgcc on win32.
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*
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* Copyright (C) 1996, 1998, 2001, 2003, 2008, 2009 Free Software Foundation, Inc.
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* Written By Steve Chamberlain
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*
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* This file is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the
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* Free Software Foundation; either version 3, or (at your option) any
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* later version.
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*
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* This file is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* Under Section 7 of GPL version 3, you are granted additional
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* permissions described in the GCC Runtime Library Exception, version
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* 3.1, as published by the Free Software Foundation.
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*
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* You should have received a copy of the GNU General Public License and
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* a copy of the GCC Runtime Library Exception along with this program;
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* see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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* .
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*/
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#ifdef L_chkstk
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/* Function prologue calls _alloca to probe the stack when allocating more
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than CHECK_STACK_LIMIT bytes in one go. Touching the stack at 4K
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increments is necessary to ensure that the guard pages used
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by the OS virtual memory manger are allocated in correct sequence. */
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.global ___chkstk
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.global __alloca
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#ifndef _WIN64
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___chkstk:
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__alloca:
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pushl %ecx /* save temp */
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leal 8(%esp), %ecx /* point past return addr */
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cmpl $0x1000, %eax /* > 4k ?*/
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jb Ldone
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Lprobe:
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subl $0x1000, %ecx /* yes, move pointer down 4k*/
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orl $0x0, (%ecx) /* probe there */
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subl $0x1000, %eax /* decrement count */
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cmpl $0x1000, %eax
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ja Lprobe /* and do it again */
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Ldone:
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subl %eax, %ecx
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orl $0x0, (%ecx) /* less than 4k, just peek here */
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movl %esp, %eax /* save old stack pointer */
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movl %ecx, %esp /* decrement stack */
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movl (%eax), %ecx /* recover saved temp */
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movl 4(%eax), %eax /* recover return address */
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/* Push the return value back. Doing this instead of just
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jumping to %eax preserves the cached call-return stack
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used by most modern processors. */
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pushl %eax
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ret
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#else
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/* __alloca is a normal function call, which uses %rcx as the argument. And stack space
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for the argument is saved. */
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__alloca:
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movq %rcx, %rax
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addq $0x7, %rax
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andq $0xfffffffffffffff8, %rax
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popq %rcx /* pop return address */
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popq %r10 /* Pop the reserved stack space. */
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movq %rsp, %r10 /* get sp */
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cmpq $0x1000, %rax /* > 4k ?*/
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jb Ldone_alloca
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Lprobe_alloca:
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subq $0x1000, %r10 /* yes, move pointer down 4k*/
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orq $0x0, (%r10) /* probe there */
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subq $0x1000, %rax /* decrement count */
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cmpq $0x1000, %rax
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ja Lprobe_alloca /* and do it again */
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Ldone_alloca:
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subq %rax, %r10
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orq $0x0, (%r10) /* less than 4k, just peek here */
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movq %r10, %rax
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subq $0x8, %r10 /* Reserve argument stack space. */
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movq %r10, %rsp /* decrement stack */
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/* Push the return value back. Doing this instead of just
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jumping to %rcx preserves the cached call-return stack
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used by most modern processors. */
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pushq %rcx
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ret
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/* ___chkstk is a *special* function call, which uses %rax as the argument.
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We avoid clobbering the 4 integer argument registers, %rcx, %rdx,
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%r8 and %r9, which leaves us with %rax, %r10, and %r11 to use. */
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___chkstk:
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addq $0x7, %rax /* Make sure stack is on alignment of 8. */
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andq $0xfffffffffffffff8, %rax
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popq %r11 /* pop return address */
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movq %rsp, %r10 /* get sp */
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cmpq $0x1000, %rax /* > 4k ?*/
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jb Ldone
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Lprobe:
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subq $0x1000, %r10 /* yes, move pointer down 4k*/
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orl $0x0, (%r10) /* probe there */
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subq $0x1000, %rax /* decrement count */
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cmpq $0x1000, %rax
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ja Lprobe /* and do it again */
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Ldone:
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subq %rax, %r10
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orl $0x0, (%r10) /* less than 4k, just peek here */
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movq %r10, %rsp /* decrement stack */
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/* Push the return value back. Doing this instead of just
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jumping to %r11 preserves the cached call-return stack
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used by most modern processors. */
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pushq %r11
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ret
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#endif
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#endif
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