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428
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1 /* `alloca' standard 4.2 subroutine for 68000's and 16000's and others.
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2 Copyright (C) 1985, 1986, 1988 Free Software Foundation, Inc.
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3
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4 This file is part of XEmacs.
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5
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6 XEmacs is free software; you can redistribute it and/or modify it
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7 under the terms of the GNU General Public License as published by the
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8 Free Software Foundation; either version 2, or (at your option) any
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9 later version.
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10
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11 XEmacs is distributed in the hope that it will be useful, but WITHOUT
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12 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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13 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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14 for more details.
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15
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16 You should have received a copy of the GNU General Public License
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17 along with XEmacs; see the file COPYING. If not, write to
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18 the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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19 Boston, MA 02111-1307, USA. */
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20
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21 /* Synched up with: FSF 19.30. */
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22
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23 /* Both 68000 systems I have run this on have had broken versions of alloca.
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24 Also, I am told that non-berkeley systems do not have it at all.
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25 So replace whatever system-provided alloca there may be
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26 on all 68000 systems. */
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27
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28 #define NOT_C_CODE
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29 #ifdef emacs
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30 #include <config.h>
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31 #else
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32 #include "config.h"
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33 #endif
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34
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35 #ifndef HAVE_ALLOCA /* define this to use system's alloca */
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36
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37 #ifndef m68k
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38 #ifndef m68000
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39 you
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40 lose!!
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41 #endif /* m68000 */
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42 #endif /* m68k */
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43
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44
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45 #ifdef m68k /* SGS assembler totally different */
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46 file "alloca.s"
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47 global alloca
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48 alloca:
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49 mov.l (%sp)+,%a1 # pop return addr from top of stack
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50 mov.l (%sp)+,%d0 # pop size in bytes from top of stack
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51 add.l &R%1,%d0 # round size up to long word
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52 and.l &-4,%d0 # mask out lower two bits of size
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53 sub.l %d0,%sp # allocate by moving stack pointer
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54 tst.b P%1(%sp) # stack probe to allocate pages
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55 mov.l %sp,%a0 # return pointer as pointer
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56 mov.l %sp,%d0 # return pointer as int to avoid disaster
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57 add.l &-4,%sp # new top of stack
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58 jmp (%a1) # not a normal return
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59 set S%1,64 # safety factor for C compiler scratch
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60 set R%1,3+S%1 # add to size for rounding
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61 set P%1,-132 # probe this far below current top of stack
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62
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63 #else /* not m68k */
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64
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65 #ifdef m68000
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66
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67 /* Some systems want the _, some do not. Win with both kinds. */
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68 .globl _alloca
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69 _alloca:
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70 .globl alloca
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71 alloca:
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72 movl sp@+,a0
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73 movl a7,d0
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74 subl sp@,d0
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75 andl #~3,d0
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76 movl d0,sp
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77 tstb sp@(0) /* Make stack pages exist */
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78 /* Needed on certain systems
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79 that lack true demand paging */
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80 addql #4,d0
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81 jmp a0@
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82
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83 #endif /* m68000 */
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84 #endif /* not m68k */
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85
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86 #endif /* not HAVE_ALLOCA */
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