lib/i86/misc/alloca.s

   1 #
   2 !       alloca() - allocate space on the stack          Author: Kees J. Bot
   3 !                                                               26 Jan 1994
   4
   5 #if __ACK__     /* BCC can't do alloca(), register saving is wrong. */
   6
   7 .text
   8 .define _alloca
   9 _alloca:
  10         pop     cx              ! Return address
  11         pop     ax              ! Bytes to allocate
  12         add     ax, #2*2+1      ! Add space for two saved register variables
  13         andb    al, #0xFE       ! Align
  14         mov     bx, sp          ! Keep current sp
  15         sub     sp, ax          ! Lower stack
  16         mov     ax, sp          ! Return value
  17         push    2(bx)           ! Push what is probably the saved si
  18         push    (bx)            ! Saved di
  19                                 ! Now ACK can still do:
  20                                 !       pop di; pop si; mov sp, bp; pop bp; ret
  21         push    ax              ! Dummy argument
  22         jmp     (cx)
  23 #endif