[PATCH, gas] PC-relative fx_offset calculation

Alan Modra amodra@gmail.com
Thu Mar 7 22:31:00 GMT 2013

On Thu, Mar 07, 2013 at 01:39:00PM +0800, Chung-Lin Tang wrote:
> On 2013/3/6 06:28 PM, Alan Modra wrote:
> > On Wed, Mar 06, 2013 at 02:37:00PM +0800, Chung-Lin Tang wrote:
> >> This is only lightly tested so far, WDYT? (I believe this patch should
> >> make more sense now...)
> > 
> > Yes, it makes sense, but why is it that you need to call frag_more in
> > the middle of assembling an instruction?  The normal course of action
> > is to parse the insn, call frag_more when you know the size (or max
> > size) of the insn, then emit insn bytes and any fixups.
> I don't think the nios2 port is calling frag_more() like that. The
> overall sequence of actions is like the way you described.


> However it seems that, dot_value is recorded during the parsing (when
> expression() is called), and the subsequent frag_more() call may create
> a new frag, causing mismatch of fx_frag and fx_dot_value when creating
> the new fix.

Huh.  I think you're correct.  If you can commit your patch, please do

> I am not sure why this has not been seen in other ports, as the
> dot_value patch seems to have been there for a decade...

Possibly the reason other ports haven't seen the problem is that they
don't use fx_offset.  I do see a comment in tc-tilepro.c and
tc-tilegx.c that indicates those ports have hit the problem.

Alan Modra
Australia Development Lab, IBM

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