Re: Help needed: small piece of assembler code for IRAF

[John David Anglin <dave.anglin@bell.net>]

Hi Ole,

Attached is PA 1.1 zsvjmp.s code generated by gcc.  I then hacked the code to remove
the stack frame and added some comments.  See zsvjmp_.s file.  The resulting code is
slightly more optimal than your old assembly fragment.

It assembles okay with current binutils assembler.

Hope this helps,
Dave Anglin

On 2024-09-18 2:31 p.m., Ole Streicher wrote:
> Dear m68k enthusiasts,
>
> I am the maintainer of the "iraf" package [1]. Although most of the code is portable, it needs one piece of assembler code for each platform 
> that provides a (sort of) setjmp for FORTRAN.
>
> A "C" implementation for this looks like:
>
> #include <setjmp.h>
>
> int zsvjmp_( long *buf, long *status ) {
>   *status = 0;
>   ((long **)buf)[0] = status;
>   return sigsetjmp ((void *)((long **)buf+1),0);
> }
>
> however this does not work, since the "sigsetjmp" call needs to be replaced by a jump to sigsetjmp instead.
>
> As IRAF is a 40-year old package, there was already some assembler that was used ~35 years ago [2]:
>
> -------------------------------8<-----------------------------------
>     .proc
>     .import setjmp
>     .export zsvjmp
>     .callinfo
> zsvjmp
> ;
> ;    save address to status word in jmp_buf[0]
> ;
>     stw     arg1,0(0,arg0)
>     ldi    0,1
>     stws    1,0(0,arg1)
> ;
> ;    call setjmp with jmp_buf[1]..jmp_buf[51]
> ;
>     addi    4,arg0,arg0
>     b    setjmp
>     nop
> ;
> ;    setjmp will return directly to the caller of zsvjmp at this
> ;    point, so the next statement will never be reached.
> ;
>     nop
>     .procend
> -------------------------------8<-----------------------------------
>
> However, just including this does not work because assembler syntax changed [3].
>
> I created a small repository [4] that contains the assembler I collected
> so far as well as two test programs.
>
> As I am not familiar with HP assembler I have no idea how to adopt the assembler code. Maybe someone could help me here? Preferably under the 
> IRAF license [5], so that it can be included upstream later.
>
> One way that worked for other platforms was to compute the C snipped above (having the sigsetjmp function name by something else) with an 
> optimizing compiler.
>
> There is no request from the users to have this ported to hppa, and I
> doubt that ever will. My main motivation to get it ported is to check
> the package for hidden problems on "unusual" architectures.
>
> Best regards
>
> Ole
>
>
> [1] https://tracker.debian.org/pkg/iraf
> [2] https://github.com/iraf-community/iraf/blob/v2.16.1/unix/portkit/zsvjmp.s.HP800
> [3] https://buildd.debian.org/status/fetch.php?pkg=iraf&arch=hppa&ver=2.18.1%7Erc1-3%7E2&stamp=1726682218&raw=0
> [4] https://github.com/olebole/zsvjmp
> [5] https://iraf-community.github.io/COPYRIGHT.html


--
John David Anglin  dave.anglin@bell.net

	.LEVEL 1.1
	.text
	.align 4
.globl zsvjmp_
	.type	zsvjmp_, @function
zsvjmp_:
	.PROC
	.CALLINFO FRAME=64,CALLS,SAVE_RP
	.ENTRY
	stw %r2,-20(%r30)
	copy %r25,%r28
	ldo 64(%r30),%r30
	stw %r0,0(%r25)
	ldo 4(%r26),%r26
	ldi 0,%r25
	bl __sigsetjmp,%r2
	stw %r28,-4(%r26)
	ldw -84(%r30),%r2
	bv %r0(%r2)
	ldo -64(%r30),%r30
	.EXIT
	.PROCEND
	.size	zsvjmp_, .-zsvjmp_
	.ident	"GCC: (Debian 14.2.0-4) 14.2.0"
	.section	.note.GNU-stack,"",@progbits

	.LEVEL 1.1
	.text
	.align 4
.globl zsvjmp_
	.type	zsvjmp_, @function
zsvjmp_:
	.PROC
; We don't need a frame
	.CALLINFO
	.ENTRY
	copy %r25,%r28
;
;	*status = 0
;
	stw %r0,0(%r25)
;
;	arg0++
;
	ldo 4(%r26),%r26
	ldi 0,%r25
	b __sigsetjmp
;
;	((long **)buf)[0] = status;
;
	stw %r28,-4(%r26)
;
;	__sigsetjmp will return directly to the caller of zsvjmp at this
;	point, so the next statement will never be reached.
;
	nop
	.EXIT
	.PROCEND
	.size	zsvjmp_, .-zsvjmp_
	.ident	"GCC: (Debian 14.2.0-4) 14.2.0"
	.section	.note.GNU-stack,"",@progbits