Been busy, but I'm back looking at this.
David Laight wrote:
> With a scratch register there are some two instruction sequences.
> Reusing the destination register something like:
>
> addis %r30,%r31,hi(.label - 1b)
> lwzx %r30,lo(.label - 1b)(%r30)
>
I've managed to convert that into something gcc understands:
addis 30, 31, (.label-(1b))@ha
lwz 30, (.label-(1b))@l(30)
The "@l" is the equivalent of lo() and "@ha" is the sign extending
verions of hi(). Unfortunately, this code segfaults on executiion.
I suspect that is because I have used the LWZ instruction instead
of LWZX suggested by David.
Unfortunately gcc doesn't accept LWZX which I found documented
here:
http://pds.twi.tudelft.nl/vakken/in101/labcourse/instruction-set/lwzx.html
and seems to have LX as a synonym, but that instruction only seems
to work on registers, not on addresses as we have here.
I'm actually beginning to have a better understanding of the code
and I've pulled out these snippets code code into a small assember
program I'm compiling with gcc and running under gdb.
Cheers,
Erik
--
----------------------------------------------------------------------
Erik de Castro Lopo
http://www.mega-nerd.com/
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