Re: Gen PC relative code m68k

[geneSmith <gene dot smith at sea dot siemens dot com>]

geneSmith wrote, On 5/13/2004 5:56 PM:

> geneSmith wrote, On 5/12/2004 4:33 PM:
>
> > Is it possible to compile with pc relative code and data references like
> > you can with MRI (microtec) compiler, i.e.,
> >
> > mcc68k -Mcp -Mdp -c xsubs.c    ?
> >
> > The closest I can find in gcc is the position independent flag, i.e.,
> >
> > gcc -c -fpic xsub.c
> >
> > but this produces some section .got and .got.plt which I have no idea
> > how to use. I need to zero .bss and initialize .data also in a separate
> > routine (probaby assembly).
> >
> > Is anyone familiar with this?
> >
> > Tks,
> > -gene
> For the record, this describes almost exactly what I was looking for.
> http://sources.redhat.com/ml/crossgcc/1999-q1/msg00170.html
> Thanks you Olivier Carmona!
Again for the record. A minor bug in O. Carmona's code. When used, a2 is 
a positive offset. With original code it was negative. Made it positive 
with 3 lines labeled new*: below.

start:

....

        /* Load the address relative to the PC */
        lea     (_GLOBAL_OFFSET_TABLE_,pc),a5
        /* Load the address given by the linker */
        movea.l #_GLOBAL_OFFSET_TABLE_,a2
        /* Then find the offset */
        suba.l  a5,a2
        beq     L1                  /* Null Offset ? */
new1:	move.l	a2,d1
new2:	neg.l	d1
new3:	move.l	d1,a2

        /* Add the offset to all of the Global Offset Table */
        move.l  #gotsize,d1         /* gostize : linker variable */
L0:     subq.l  #4,d1
        blt.b   L1                  /* End of GOT ? */
        movea.l (a5,d1.l),a3        /* Read the GOT */
        adda.l  a2,a3               /* Add the offset */
        move.l  a3,(a5,d1.l)        /* Write back in the GOT */
        bra     L0


------
Want more information?  See the CrossGCC FAQ, http://www.objsw.com/CrossGCC/
Want to unsubscribe? Send a note to crossgcc-unsubscribe@sources.redhat.com