minix/lib/i86/misc/alloca.s

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2005-04-21 16:53:53 +02:00
#
! alloca() - allocate space on the stack Author: Kees J. Bot
! 26 Jan 1994
#if __ACK__ /* BCC can't do alloca(), register saving is wrong. */
.text
.define _alloca
_alloca:
pop cx ! Return address
pop ax ! Bytes to allocate
add ax, #2*2+1 ! Add space for two saved register variables
andb al, #0xFE ! Align
mov bx, sp ! Keep current sp
sub sp, ax ! Lower stack
mov ax, sp ! Return value
push 2(bx) ! Push what is probably the saved si
push (bx) ! Saved di
! Now ACK can still do:
! pop di; pop si; mov sp, bp; pop bp; ret
push ax ! Dummy argument
jmp (cx)
#endif