alloca.s

早期freebsd实现

/* `alloca' standard 4.2 subroutine for 68000's and 16000's and others.
   Also has _setjmp and _longjmp for pyramids.
   Copyright (C) 1985, 1986, 1988 Free Software Foundation, Inc.

This file is part of GNU Emacs.

GNU Emacs is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 1, or (at your option)
any later version.

GNU Emacs is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU Emacs; see the file COPYING.  If not, write to
the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */


/* Both 68000 systems I have run this on have had broken versions of alloca.
   Also, I am told that non-berkeley systems do not have it at all.
   So replace whatever system-provided alloca there may be
   on all 68000 systems.  */

#define NOT_C_CODE
#include "config.h"

#ifndef HAVE_ALLOCA  /* define this to use system's alloca */

#ifndef hp9000s300
#ifndef m68k
#ifndef m68000
#ifndef WICAT
#ifndef ns32000
#ifndef ns16000
#ifndef sequent
#ifndef pyramid
#ifndef ATT3B5
#ifndef XENIX
you
lose!!
#endif /* XENIX */
#endif /* ATT3B5 */
#endif /* pyramid */
#endif /* sequent */
#endif /* ns32000 */
#endif /* ns16000 */
#endif /* WICAT */
#endif /* m68000 */
#endif /* m68k */
#endif /* hp9000s300 */


#ifdef hp9000s300
#ifdef OLD_HP_ASSEMBLER
	data
	text
	globl	_alloca
_alloca	
	move.l	(sp)+,a0	; pop return addr from top of stack
	move.l	(sp)+,d0	; pop size in bytes from top of stack
	add.l	#ROUND,d0	; round size up to long word
	and.l	#MASK,d0	; mask out lower two bits of size
	sub.l	d0,sp		; allocate by moving stack pointer
	tst.b	PROBE(sp)	; stack probe to allocate pages
	move.l	sp,d0		; return pointer
	add.l	#-4,sp		; new top of stack
	jmp	(a0)		; not a normal return
MASK	equ	-4		; Longword alignment
ROUND	equ	3		; ditto
PROBE	equ	-128		; safety buffer for C compiler scratch
	data
#else /* new hp assembler syntax */
/*
  The new compiler does "move.m <registers> (%sp)" to save registers,
    so we must copy the saved registers when we mung the sp.
  The old compiler did "move.m <register> <offset>(%a6)", which
    gave us no trouble
 */
	text
	set	PROBE,-128	# safety for C frame temporaries
	set	MAXREG,22	# d2-d7, a2-a5, fp2-fp7 may have been saved
	global	_alloca
_alloca:
	mov.l	(%sp)+,%a0	# return addess
	mov.l	(%sp)+,%d0	# number of bytes to allocate
	mov.l	%sp,%a1		# save old sp for register copy
	mov.l	%sp,%d1		# compute new sp
	sub.l	%d0,%d1		# space requested
	and.l	&-4,%d1		# round down to longword
	sub.l	&MAXREG*4,%d1	# space for saving registers
	mov.l	%d1,%sp		# save new value of sp
	tst.b	PROBE(%sp)	# create pages (sigh)
	mov.l	%a2,%d1		# save reg a2
	mov.l	%sp,%a2
	move.w	&MAXREG-1,%d0
copy_regs_loop:			/* save caller's saved registers */
	mov.l	(%a1)+,(%a2)+
	dbra	%d0,copy_regs_loop
	mov.l	%a2,%d0		# return value
	mov.l	%d1,%a2		# restore a2
	add.l	&-4,%sp		# adjust tos
	jmp	(%a0)		# rts
#endif /* new hp assembler */
#else
#ifdef m68k			/* SGS assembler totally different */
	file	"alloca.s"
	global	alloca
alloca:
	mov.l	(%sp)+,%a1	# pop return addr from top of stack
	mov.l	(%sp)+,%d0	# pop size in bytes from top of stack
	add.l	&R%1,%d0	# round size up to long word
	and.l	&-4,%d0		# mask out lower two bits of size
	sub.l	%d0,%sp		# allocate by moving stack pointer
	tst.b	P%1(%sp)	# stack probe to allocate pages
	mov.l	%sp,%a0		# return pointer as pointer
	mov.l	%sp,%d0		# return pointer as int to avoid disaster
	add.l	&-4,%sp		# new top of stack
	jmp	(%a1)		# not a normal return
	set	S%1,64		# safety factor for C compiler scratch
	set	R%1,3+S%1	# add to size for rounding
	set	P%1,-132	# probe this far below current top of stack

#else /* not m68k */

#ifdef m68000

#ifdef WICAT
/*
 * Registers are saved after the corresponding link so we have to explicitly
 * move them to the top of the stack where they are expected to be.
 * Since we do not know how many registers were saved in the calling function
 * we must assume the maximum possible (d2-d7,a2-a5).  Hence, we end up
 * wasting some space on the stack.
 *
 * The large probe (tst.b) attempts to make up for the fact that we have
 * potentially used up the space that the caller probed for its own needs.
 */
	.procss m0
	.config "68000 1"
	.module	_alloca
MAXREG:	.const	10
	.sect	text
	.global	_alloca
_alloca:
	move.l	(sp)+,a1	; pop return address
	move.l	(sp)+,d0	; pop allocation size
	move.l	sp,d1		; get current SP value
	sub.l	d0,d1		; adjust to reflect required size...
	sub.l	#MAXREG*4,d1	; ...and space needed for registers
	and.l	#-4,d1		; backup to longword boundry
	move.l	sp,a0		; save old SP value for register copy
	move.l	d1,sp		; set the new SP value
	tst.b	-4096(sp)	; grab an extra page (to cover caller)
	move.l	a2,d1		; save callers register
	move.l	sp,a2
	move.w	#MAXREG-1,d0	; # of longwords to copy
loop:	move.l	(a0)+,(a2)+	; copy registers...
	dbra	d0,loop		; ...til there are no more
	move.l	a2,d0		; end of register area is addr for new space
	move.l	d1,a2		; restore saved a2.
	addq.l	#4,sp		; caller will increment sp by 4 after return.
	move.l	d0,a0		; return value in both a0 and d0.
	jmp	(a1)
	.end	_alloca
#else

/* Some systems want the _, some do not.  Win with both kinds.  */
.globl	_alloca
_alloca:
.globl	alloca
alloca:
	movl	sp@+,a0
	movl	a7,d0
	subl	sp@,d0
	andl	#~3,d0
	movl	d0,sp
	tstb	sp@(0)		/* Make stack pages exist  */
				/* Needed on certain systems
				   that lack true demand paging */
	addql	#4,d0
	jmp	a0@

#endif /* not WICAT */
#endif /* m68000 */
#endif /* not m68k */
#endif /* not hp9000s300 */

#if defined (ns16000) || defined (ns32000)

	.text
	.align	2
/* Some systems want the _, some do not.  Win with both kinds.  */
.globl	_alloca
_alloca:
.globl	alloca
alloca:

/* Two different assembler syntaxes are used for the same code
	on different systems.  */

#ifdef sequent
#define IM
#define REGISTER(x) x
#else
#define IM $
#define REGISTER(x) 0(x)
#endif

/*
 * The ns16000 is a little more difficult, need to copy regs.
 * Also the code assumes direct linkage call sequence (no mod table crap).
 * We have to copy registers, and therefore waste 32 bytes.
 *
 * Stack layout:
 * new	sp ->	junk	
 *	 	registers (copy)
 *	r0 ->	new data		
 *		 | 	  (orig retval)
 *		 |	  (orig arg)
 * old  sp ->	regs	  (orig)
 *		local data
 *	fp ->	old fp
 */

	movd	tos,r1		/*  pop return addr */
	negd	tos,r0		/*  pop amount to allocate */
	sprd	sp,r2
	addd	r2,r0
	bicb	IM/**/3,r0	/*  4-byte align */
	lprd	sp,r0
	adjspb	IM/**/36	/*  space for regs, +4 for caller to pop */
	movmd	0(r2),4(sp),IM/**/4	/*  copy regs */
	movmd	0x10(r2),0x14(sp),IM/**/4
	jump	REGISTER(r1)	/* funky return */
#endif /* ns16000 or ns32000. */

#ifdef pyramid

.globl _alloca

_alloca: addw $3,pr0	# add 3 (dec) to first argument
	bicw $3,pr0	# then clear its last 2 bits
	subw pr0,sp	# subtract from SP the val in PR0
	andw $-32,sp	# keep sp aligned on multiple of 32.
	movw sp,pr0	# ret. current SP
	ret

#ifdef PYRAMID_OLD /* This isn't needed in system version 4.  */
.globl __longjmp
.globl _longjmp
.globl __setjmp
.globl _setjmp

__longjmp: jump _longjmp
__setjmp:  jump _setjmp
#endif

#endif /* pyramid */

#ifdef ATT3B5

	.align 4
	.globl alloca

alloca:
	movw %ap, %r8
	subw2 $9*4, %r8
	movw 0(%r8), %r1    /* pc */
	movw 4(%r8), %fp
	movw 8(%r8), %sp
	addw2 %r0, %sp /* make room */
	movw %sp, %r0 /* return value */
	jmp (%r1) /* continue... */

#endif /* ATT3B5 */

#ifdef XENIX

.386

_TEXT segment dword use32 public 'CODE'
assume   cs:_TEXT

;-------------------------------------------------------------------------

public _alloca
_alloca proc near

	pop	ecx		; return address
	pop	eax		; amount to alloc
	add	eax,3		; round it to 32-bit boundary
	and	al,11111100B	;
	mov	edx,esp		; current sp in edx
	sub	edx,eax		; lower the stack
	xchg	esp,edx		; start of allocation in esp, old sp in edx
	mov	eax,esp		; return ptr to base in eax
	push	[edx+8]		; save poss. stored reg. values (esi,edi,ebx)
	push	[edx+4]		;  on lowered stack
	push	[edx]		;
	sub	esp,4		; allow for 'add esp, 4'
	jmp	ecx		; jump to return address

_alloca endp

_TEXT	ends

end

#endif /* XENIX */

#endif /* not HAVE_ALLOCA */