src/alloca.s

   1 /* `alloca' standard 4.2 subroutine for 68000's and 16000's and others.
   2    Also has _setjmp and _longjmp for pyramids.
   3    Copyright (C) 1985, 1986, 1988 Free Software Foundation, Inc.
   4
   5    This program is free software; you can redistribute it and/or modify it
   6    under the terms of the GNU General Public License as published by the
   7    Free Software Foundation; either version 2, or (at your option) any
   8    later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License along
  16    with this program; if not, write to the Free Software Foundation, Inc.,
  17    59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
  18
  19 /* Both 68000 systems I have run this on have had broken versions of alloca.
  20    Also, I am told that non-berkeley systems do not have it at all.
  21    So replace whatever system-provided alloca there may be
  22    on all 68000 systems.  */
  23
  24 #define NOT_C_CODE
  25 #ifdef emacs
  26 #include <config.h>
  27 #else
  28 #include "config.h"
  29 #endif
  30
  31 #ifndef HAVE_ALLOCA  /* define this to use system's alloca */
  32
  33 #ifndef hp9000s300
  34 #ifndef m68k
  35 #ifndef m68000
  36 #ifndef WICAT
  37 #ifndef ns32000
  38 #ifndef ns16000
  39 #ifndef sequent
  40 #ifndef pyramid
  41 #ifndef ATT3B5
  42 #ifndef XENIX
  43 you
  44 lose!!
  45 #endif /* XENIX */
  46 #endif /* ATT3B5 */
  47 #endif /* pyramid */
  48 #endif /* sequent */
  49 #endif /* ns16000 */
  50 #endif /* ns32000 */
  51 #endif /* WICAT */
  52 #endif /* m68000 */
  53 #endif /* m68k */
  54 #endif /* hp9000s300 */
  55
  56
  57 #ifdef hp9000s300
  58 #ifdef OLD_HP_ASSEMBLER
  59         data
  60         text
  61         globl   _alloca
  62 _alloca
  63         move.l  (sp)+,a0        ; pop return addr from top of stack
  64         move.l  (sp)+,d0        ; pop size in bytes from top of stack
  65         add.l   #ROUND,d0       ; round size up to long word
  66         and.l   #MASK,d0        ; mask out lower two bits of size
  67         sub.l   d0,sp           ; allocate by moving stack pointer
  68         tst.b   PROBE(sp)       ; stack probe to allocate pages
  69         move.l  sp,d0           ; return pointer
  70         add.l   #-4,sp          ; new top of stack
  71         jmp     (a0)            ; not a normal return
  72 MASK    equ     -4              ; Longword alignment
  73 ROUND   equ     3               ; ditto
  74 PROBE   equ     -128            ; safety buffer for C compiler scratch
  75         data
  76 #else /* new hp assembler syntax */
  77 /*
  78   The new compiler does "move.m <registers> (%sp)" to save registers,
  79     so we must copy the saved registers when we mung the sp.
  80   The old compiler did "move.m <register> <offset>(%a6)", which
  81     gave us no trouble
  82  */
  83         text
  84         set     PROBE,-128      # safety for C frame temporaries
  85         set     MAXREG,22       # d2-d7, a2-a5, fp2-fp7 may have been saved
  86         global  _alloca
  87 _alloca:
  88         mov.l   (%sp)+,%a0      # return address
  89         mov.l   (%sp)+,%d0      # number of bytes to allocate
  90         mov.l   %sp,%a1         # save old sp for register copy
  91         mov.l   %sp,%d1         # compute new sp
  92         sub.l   %d0,%d1         # space requested
  93         and.l   &-4,%d1         # round down to longword
  94         sub.l   &MAXREG*4,%d1   # space for saving registers
  95         mov.l   %d1,%sp         # save new value of sp
  96         tst.b   PROBE(%sp)      # create pages (sigh)
  97         mov.l   %a2,%d1         # save reg a2
  98         mov.l   %sp,%a2
  99         move.w  &MAXREG-1,%d0
 100 copy_regs_loop:                 /* save caller's saved registers */
 101         mov.l   (%a1)+,(%a2)+
 102         dbra    %d0,copy_regs_loop
 103         mov.l   %a2,%d0         # return value
 104         mov.l   %d1,%a2         # restore a2
 105         add.l   &-4,%sp         # adjust tos
 106         jmp     (%a0)           # rts
 107 #endif /* new hp assembler */
 108 #else
 109 #ifdef m68k                     /* SGS assembler totally different */
 110         file    "alloca.s"
 111         global  alloca
 112 alloca:
 113 #ifdef MOTOROLA_DELTA
 114 /* slightly modified version of alloca to motorola sysV/68 pcc - based
 115    compiler.
 116    this compiler saves used registers relative to %sp instead of %fp.
 117    alright, just make new copy of saved register set whenever we allocate
 118    new space from stack..
 119    this is true at last until SVR3V7 . bug has reported to Motorola. */
 120         set     MAXREG,10       # max no of registers to save (d2-d7, a2-a5)
 121         mov.l   (%sp)+,%a1      # pop return addr from top of stack
 122         mov.l   (%sp)+,%d0      # pop size in bytes from top of stack
 123         mov.l   %sp,%a0         # save stack pointer for register copy
 124         addq.l  &3,%d0          # round size up to long word
 125         andi.l  &-4,%d0         # mask out lower two bits of size
 126         mov.l   %sp,%d1         # compute new value of sp to d1
 127         sub.l   %d0,%d1         # pseudo-allocate by moving stack pointer
 128         sub.l   &MAXREG*4,%d1   # allocate more space for saved regs.
 129         mov.l   %d1,%sp         # actual allocation.
 130         move.w  &MAXREG-1,%d0   # d0 counts saved regs.
 131         mov.l   %a2,%d1         # preserve a2.
 132         mov.l   %sp,%a2         # make pointer to new reg save area.
 133 copy_regs_loop:                 # copy stuff from old save area.
 134         mov.l   (%a0)+,(%a2)+   # save saved register
 135         dbra    %d0,copy_regs_loop
 136         mov.l   %a2,%a0         # now a2 is start of allocated space.
 137         mov.l   %a2,%d0         # return it in both a0 and d0 to play safe.
 138         mov.l   %d1,%a2         # restore a2.
 139         subq.l  &4,%sp          # new top of stack
 140         jmp     (%a1)           # far below normal return
 141 #else /* not MOTOROLA_DELTA */
 142         mov.l   (%sp)+,%a1      # pop return addr from top of stack
 143         mov.l   (%sp)+,%d0      # pop size in bytes from top of stack
 144         add.l   &R%1,%d0        # round size up to long word
 145         and.l   &-4,%d0         # mask out lower two bits of size
 146         sub.l   %d0,%sp         # allocate by moving stack pointer
 147         tst.b   P%1(%sp)        # stack probe to allocate pages
 148         mov.l   %sp,%a0         # return pointer as pointer
 149         mov.l   %sp,%d0         # return pointer as int to avoid disaster
 150         add.l   &-4,%sp         # new top of stack
 151         jmp     (%a1)           # not a normal return
 152         set     S%1,64          # safety factor for C compiler scratch
 153         set     R%1,3+S%1       # add to size for rounding
 154         set     P%1,-132        # probe this far below current top of stack
 155 #endif /* not MOTOROLA_DELTA */
 156
 157 #else /* not m68k */
 158
 159 #ifdef m68000
 160
 161 #ifdef WICAT
 162 /*
 163  * Registers are saved after the corresponding link so we have to explicitly
 164  * move them to the top of the stack where they are expected to be.
 165  * Since we do not know how many registers were saved in the calling function
 166  * we must assume the maximum possible (d2-d7,a2-a5).  Hence, we end up
 167  * wasting some space on the stack.
 168  *
 169  * The large probe (tst.b) attempts to make up for the fact that we have
 170  * potentially used up the space that the caller probed for its own needs.
 171  */
 172         .procss m0
 173         .config "68000 1"
 174         .module _alloca
 175 MAXREG: .const  10
 176         .sect   text
 177         .global _alloca
 178 _alloca:
 179         move.l  (sp)+,a1        ; pop return address
 180         move.l  (sp)+,d0        ; pop allocation size
 181         move.l  sp,d1           ; get current SP value
 182         sub.l   d0,d1           ; adjust to reflect required size...
 183         sub.l   #MAXREG*4,d1    ; ...and space needed for registers
 184         and.l   #-4,d1          ; backup to longword boundary
 185         move.l  sp,a0           ; save old SP value for register copy
 186         move.l  d1,sp           ; set the new SP value
 187         tst.b   -4096(sp)       ; grab an extra page (to cover caller)
 188         move.l  a2,d1           ; save callers register
 189         move.l  sp,a2
 190         move.w  #MAXREG-1,d0    ; # of longwords to copy
 191 loop:   move.l  (a0)+,(a2)+     ; copy registers...
 192         dbra    d0,loop         ; ...til there are no more
 193         move.l  a2,d0           ; end of register area is addr for new space
 194         move.l  d1,a2           ; restore saved a2.
 195         addq.l  #4,sp           ; caller will increment sp by 4 after return.
 196         move.l  d0,a0           ; return value in both a0 and d0.
 197         jmp     (a1)
 198         .end    _alloca
 199 #else
 200
 201 /* Some systems want the _, some do not.  Win with both kinds.  */
 202 .globl  _alloca
 203 _alloca:
 204 .globl  alloca
 205 alloca:
 206         movl    sp@+,a0
 207         movl    a7,d0
 208         subl    sp@,d0
 209         andl    #~3,d0
 210         movl    d0,sp
 211         tstb    sp@(0)          /* Make stack pages exist  */
 212                                 /* Needed on certain systems
 213                                    that lack true demand paging */
 214         addql   #4,d0
 215         jmp     a0@
 216
 217 #endif /* not WICAT */
 218 #endif /* m68000 */
 219 #endif /* not m68k */
 220 #endif /* not hp9000s300 */
 221
 222 #if defined (ns16000) || defined (ns32000)
 223
 224         .text
 225         .align  2
 226 /* Some systems want the _, some do not.  Win with both kinds.  */
 227 .globl  _alloca
 228 _alloca:
 229 .globl  alloca
 230 alloca:
 231
 232 /* Two different assembler syntaxes are used for the same code
 233         on different systems.  */
 234
 235 #ifdef sequent
 236 #define IM
 237 #define REGISTER(x) x
 238 #else
 239 #ifdef NS5   /* ns SysV assembler */
 240 #define IM $
 241 #define REGISTER(x) x
 242 #else
 243 #define IM $
 244 #define REGISTER(x) 0(x)
 245 #endif
 246 #endif
 247
 248 /*
 249  * The ns16000 is a little more difficult, need to copy regs.
 250  * Also the code assumes direct linkage call sequence (no mod table crap).
 251  * We have to copy registers, and therefore waste 32 bytes.
 252  *
 253  * Stack layout:
 254  * new  sp ->   junk
 255  *              registers (copy)
 256  *      r0 ->   new data
 257  *               |        (orig retval)
 258  *               |        (orig arg)
 259  * old  sp ->   regs      (orig)
 260  *              local data
 261  *      fp ->   old fp
 262  */
 263
 264         movd    tos,r1          /*  pop return addr */
 265         negd    tos,r0          /*  pop amount to allocate */
 266         sprd    sp,r2
 267         addd    r2,r0
 268         bicb    IM/**/3,r0      /*  4-byte align */
 269         lprd    sp,r0
 270         adjspb  IM/**/36        /*  space for regs, +4 for caller to pop */
 271         movmd   0(r2),4(sp),IM/**/4     /*  copy regs */
 272         movmd   0x10(r2),0x14(sp),IM/**/4
 273         jump    REGISTER(r1)    /* funky return */
 274 #endif /* ns16000 or ns32000 */
 275
 276 #ifdef pyramid
 277
 278 .globl _alloca
 279
 280 _alloca: addw $3,pr0    # add 3 (dec) to first argument
 281         bicw $3,pr0     # then clear its last 2 bits
 282         subw pr0,sp     # subtract from SP the val in PR0
 283         andw $-32,sp    # keep sp aligned on multiple of 32.
 284         movw sp,pr0     # ret. current SP
 285         ret
 286
 287 #ifdef PYRAMID_OLD /* This isn't needed in system version 4.  */
 288 .globl __longjmp
 289 .globl _longjmp
 290 .globl __setjmp
 291 .globl _setjmp
 292
 293 __longjmp: jump _longjmp
 294 __setjmp:  jump _setjmp
 295 #endif
 296
 297 #endif /* pyramid */
 298
 299 #ifdef ATT3B5
 300
 301         .align 4
 302         .globl alloca
 303
 304 alloca:
 305         movw %ap, %r8
 306         subw2 $9*4, %r8
 307         movw 0(%r8), %r1    /* pc */
 308         movw 4(%r8), %fp
 309         movw 8(%r8), %sp
 310         addw2 %r0, %sp /* make room */
 311         movw %sp, %r0 /* return value */
 312         jmp (%r1) /* continue... */
 313
 314 #endif /* ATT3B5 */
 315
 316 #ifdef XENIX
 317
 318 .386
 319
 320 _TEXT segment dword use32 public 'CODE'
 321 assume   cs:_TEXT
 322
 323 ;-------------------------------------------------------------------------
 324
 325 public _alloca
 326 _alloca proc near
 327
 328         pop     ecx             ; return address
 329         pop     eax             ; amount to alloc
 330         add     eax,3           ; round it to 32-bit boundary
 331         and     al,11111100B    ;
 332         mov     edx,esp         ; current sp in edx
 333         sub     edx,eax         ; lower the stack
 334         xchg    esp,edx         ; start of allocation in esp, old sp in edx
 335         mov     eax,esp         ; return ptr to base in eax
 336         push    [edx+8]         ; save poss. stored reg. values (esi,edi,ebx)
 337         push    [edx+4]         ;  on lowered stack
 338         push    [edx]           ;
 339         sub     esp,4           ; allow for 'add esp, 4'
 340         jmp     ecx             ; jump to return address
 341
 342 _alloca endp
 343
 344 _TEXT   ends
 345
 346 end
 347
 348 #endif /* XENIX */
 349
 350 #endif /* not HAVE_ALLOCA */